Ebook Office-Based rhinology: Principles and techniques (Part 1)

Part 1 book “Office-Based rhinology: Principles and techniques” has contents: History of nasal endoscopy, endoscopic anatomy for office-based rhinology procedures, radiology of the nose and paranasal sinuses, room setup and equipment for office procedures, patient selection and informed consent for office-based procedures,… and other contents.

Principles and Techniques

Principles and Techniques

Zara M Patel, MD Sarah K Wise, MD, MSCR

John M DelGaudio, MD, FACS

Division of RhinologyDepartment of Otolaryngology-Head and Neck SurgeryEmory University of School of Medicine

e-mail: info@pluralpublishing.com

Web site: http://www.pluralpublishing.com

Copyright © by Plural Publishing, Inc 2013

Typeset in 11/13 Adobe Garamond by Flanagan’s Publishing Services, Inc.

Printed in the United States of America by Bang Printing

All rights, including that of translation, reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, including photocopying, recording, taping, Web distribution, or information storage and retrieval systems with- out the prior written consent of the publisher.

For permission to use material from this text, contact us by

Telephone: (866) 758-7251

Fax: (888) 758-7255

e-mail: permissions@pluralpublishing.com

NOTICE TO THE READER

Care has been taken to confirm the accuracy of the indications, procedures, drug dosages, and diagnosis and remediation protocols presented in this book and to ensure that they conform to the practices of the general med- ical and health services communities However, the authors, editors, and publisher are not responsible for errors

or omissions or for any consequences from application of the information in this book and make no warranty, expressed or implied, with respect to the currency, completeness, or accuracy of the contents of the publication The diagnostic and remediation protocols and the medications described do not necessarily have specific approval

by the Food and Drug administration for use in the disorders and/or diseases and dosages for which they are recommended Application of this information in a particular situation remains the professional responsibility of the practitioner Because standards of practice and usage change, it is the responsibility of the practitioner to keep abreast of revised recommendations, dosages, and procedures.

Every attempt has been made to contact the copyright holders for material originally printed in another source If any have been inadvertently overlooked, the publishers will gladly make the necessary arrangements at the first opportunity.

Library of Congress Cataloging-in-Publication Data

Office-based rhinology : principles and techniques / Zara M Patel, co-editor, Sarah K Wise, co-editor, John M DelGaudio, co-editor.

p ; cm.

Includes bibliographical references and index.

ISBN-13: 978-1-59756-475-5 (alk paper)

ISBN-10: 1-59756-475-3 (alk paper)

I Patel, Zara M II Wise, Sarah K III DelGaudio, John M

[DNLM: 1 Nose Diseases — surgery 2 Ambulatory Surgical Procedures — methods 3 Nasal Surgical Procedures — methods 4 Nose surgery WV 300]

617.5'23 — dc23

2012042898

Introduction vii Contributors ix

5 Patient Selection and Informed Consent for Office-Based Procedures 45

Index 145

As otolaryngology has moved toward

mini-mally invasive procedures in every

sub-specialty, there has been a parallel trend to

perform these procedures in the office setting,

when possible

Physicians and patients alike can derive

benefits from moving procedures from the

hos-pital operating room to the office exam room

Physicians have more flexibility in scheduling,

delays associated with staff shift changes and

equipment turnover are eliminated, time can

be used more efficiently, and more patients

can be seen Patients are more comfortable in

a familiar environment, require less time away

from their regular schedules, have decreased

anesthesia requirements, are not exposed to

hospital acquired infectious organisms, and

often have a lower insurance copay for

office-based procedures

In this text, we cover the foundation of

knowledge a surgeon must have to prepare for

office-based procedures, including anatomy, radiology, and basic endoscopic skills We review the basic preparatory steps involved such as proper patient selection, room setup, and local anesthetic techniques, and then pres-ent multiple rhinologic procedures that can be performed in the office setting

We have asked expert rhinologists across the subspecialty to share their techniques in this text, and we thank them for their excel-lent contributions We have also compiled a DVD of selected surgical procedures to help the reader obtain a more complete and thor-ough understanding of these procedures

We hope this book will educate surgeons

at all stages of their career, whether yngology residents or those who have been practicing for many years, and allow them to develop a new and fulfilling aspect of their practice as otolaryngologists

otolar-Zara M PatelSarah K WiseJohn M DelGaudioDepartment of Otolaryngology— Head and Neck Surgery

Emory University School of Medicine

Alkis James Psaltis, MD, PhD, FRACS

Department of Otolaryngology-Head and

Neck Surgery

Medical University of South Carolina

Charleston, South Carolina

Medical University of South Carolina

Charleston, South Carolina

Chulalongkorn UniversityThailand

Emory University of School of MedicineAtlanta, Georgia

Chapters 1, 2, and 5

love and support throughout the years, I owe so much to each of you.

—Zara M Patel

To my husband and son, Justin and Bryson, who brighten every day while still keeping me grounded And to Ray and Ginny Miller, my remarkable parents, whose encouragement and guidance have made me strong I cannot thank you enough for your support.

—Sarah K Wise

To my children, Rachel and Michael, the lights of my life You make every day special And to my co-editors, Sarah and Zara I could not ask for better partners and colleagues.

—John M DelGaudio

1 History of Nasal Endoscopy

Elizabeth K Hoddeson Sarah K Wise John M DelGaudio

History of the Endoscope

The history of minimally invasive surgery

extends back in time far beyond the current

century Phillip Bozzini (1773–1809), a young

German obstetrician, first elucidated the

pros-pect of minimally invasive surgery by

essen-tially creating the foundation upon which the

principles of modern endoscopy originated;

he invented an instrument, the Lichtleiter,

which was a tool that could be introduced into

the body to solve the problem of inadequate

illumination during physical examination.1

However, he never tested his invention on a

human patient, and during his short lifetime

his device never gained widespread

accep-tance.1 Antoine Jean Desormeaux (1815–

1894) of France is credited as the “father of

endoscopy,” as he was the first to apply the

lichtleiter in patient care.2 He utilized a

sys-tem of mirrors, lenses, and flames burning

alcohol and turpentine to provide

illumina-tion for urological procedures.2 He presented

the term “endoscope” at the Academy in Paris

in 1865.2 Thomas Edison’s landmark

inven-tion, the electric light bulb, was first utilized

in an instrument created to provide surgical illumination for urological procedures by Maximilian Nitze (1848–1906), the “father

or urology,” who also is credited with taking the first endoscopic photographs.3,4 The Ger-man urologist was credited with two major contributions: magnifying the image through lenses and illuminating the organs by using an internal rather than an external light.3

The turn of the century showed ing advances in the implementation of these pioneering principles for surgical procedures

sweep-In 1910, Hans Christian Jacobaeus (1879–1937) described his original procedure, the

“laparathorakoskopie,” in addition to forming the first thoracoscopy in the same year.5 Also in 1910, Victor Darwin Lespi-nasse (1878–1946), in spite of being a urolo-gist from Chicago and not a neurosurgeon, performed the first intraventricular endoscopy and coagulation of the choroid plexus for the treatment of hydrocephalus in two children.3Laparascopy became much more func-tional with the contribution of Otto Goetze,

per-a diper-agnostic rper-adiologist of Germper-any He invented a needle that could be used to create

a pneumoperitoneum, and had the foresight

to describe its potential applications to

facili-tate minimally invasive surgery.6 In its early

stages, the pneumoperitoneum was not

with-out serious complications; Raoul Palmer, a

gynecologist, stressed the importance of the

Trendelenburg position to allow the insufflated

air to fill the pelvis, rather than compressing

the chest cavity, and stressed the need for

con-tinuous monitoring of abdominal pressure to

facilitate early detection of complications.6

The genius and creativity of many men

further contributed to the principles of

mod-ern endoscopy In 1929 Heinz Kalk invented a

135-degree lens system as well as an approach

to the peritoneum utilizing two trocars He

was the first to use laparoscopy to diagnose

liver and gallbladder disease.6 In the era of

World War II, many people suffered the

rav-ages of Mycobacterium tuberculosis; Janos

Ver-ess saw the need for better treatments, and

invented the spring-loaded needle in 1938

with the purpose of draining air or fluid from

body cavities, although he did not ever suggest

its use in laparoscopy.6 Harold H Hopkins, a

mathematician and physicist, is credited with

the development of the zoom lens system

(1948), the rod-lens system, and fiberoptics

(1960).3 His inventions provided greater light

transmission, a wider view, improved image

quality, and permitted a smaller diameter lens

Modern endoscopic instrumentation was

rap-idly materializing

Despite the amazing medical potential of

the inventions by these revolutionary

physi-cians, all of their advances were met with a

certain level of resistance In 1966 Kurt Semm

invented the automatic insufflator.6 He utilized

his improved visualization to attempt an

appen-dectomy during a routine laparoscopic

gyneco-logical exam.6 He was almost removed from the

German Society of Physicians for his

unortho-dox medical decision.6 The first successful

lapa-roscopic cholecystectomy was performed on a

human in 1987 by Phillip Mouret.7

One of the major advantages edged for endoscopic procedures is their minimally invasive nature, which decreases postoperative discomfort and speeds recovery time However, the mini-laparotomy inci-sion for laparoscopic surgery was not even described until 1971 by H.M Hasson.6The increasing acceptance of endoscopic surgery as a standard of patient care was exhib-ited in 1981, when the American College of Obstetrics and Gynecology instituted train-ing in laparoscopic surgery as an integral part

acknowl-of each acknowl-of its residency training programs.8Since that time, minimally invasive surgi-cal techniques have emerged as the standard and preferred techniques in general, urologic, orthopedic, and otolaryngologic surgical fields

History of Endoscopy of the Nose and Paranasal Sinuses

In 1901 Hirschmann, a German gologist, used a modified cystoscope to exam-ine the maxillary sinuses, and is consequently credited as the pioneer of endoscopic parana-sal sinus surgery.3,9 However, reports by Spiess detail routine use of anterior rhinoscopy since

otolaryn-1868, albeit limited by extreme difficulty in exploring the different meatuses and cavities

of the sinonasal region.10 Early endoscopic diagnostic interest focused on the Eustachian tube orifice and maxillary sinus antrum, but the techniques failed to gain popular accep-tance, often looked upon as superfluous, providing results that were more simply and equally obtained using more direct means.3,10

In 1902, Reichert performed the first sinus surgery on a maxillary sinus via an oroantral fistula as well as the first successful ethmoid surgery by removing the middle turbinate, but technical challenges limited widespread accep-tance of the technique.10–12

After Hopkins’ revolutionary

improve-ments to the optical components of

endo-scopes, which resulted in enhanced light

delivery and superior optical quality, the

techniques were extended to investigate all

paranasal sinus cavities, with the goals of

reducing unnecessary and unnecessarily

inva-sive surgery.3,10,11 Walter Messerklinger was

able to use these endoscopes, both zero and

30-degree, to study sinonasal anatomy and

mucociliary clearance in cadavers and thereby

produce his landmark book on sinonasal

endoscopic anatomy and diagnosis.10,11

Early applications of endoscopic

tech-niques to the paranasal sinuses were hindered

by technical feasibility Adequate

instrumen-tation had to be developed to facilitate even

exploring the possibilities of these

revolu-tionary techniques Upon request, Karl Storz

designed and built endoscopes with 0, 30, 70,

90, and 120 degrees of deflection to facilitate

diagnosis and operative therapy.10 The first

instruments used in sinus surgery were

ortho-pedic grasping instruments designed for

car-tilage removal, which were modified by Carl

Reiner from Vienna such that they could be

inserted into the nose parallel to the

endo-scope shaft.10,11 Following these postsurgical

patients endoscopically in the office

permit-ted these surgeon pioneers to recognize the

detrimental effects of stripping mucosa and

leaving exposed bone on the healing process,

and finer nasal instruments designed to cut

through bone and mucosa were developed.10

Functional endoscopic sinus surgery

(FESS), was coined by David Kennedy to

stress the importance of preserving mucosa

and mucociliary drainage pathways during

surgical intervention.3 David Kennedy, Heinz

Stammberger, and Wolfgang Draf are some

of the otolarynologists who popularized these

techniques, and ultimately helped change the

standard of care for management of paranasal

sinus pathology.3

Prior to the popularization of FESS, the majority of ethmoid procedures were performed via external incisions or with a headlight intranasally, but more often surgery was only directed at the maxillary and fron-tal sinuses.11,14 The operating microscope was suggested as a means of performing ethmoid-ectomies; however, despite providing a magni-fied image, its utility was limited as the small nasal aperture precludes a consistent binocu-lar view.11 The endoscope provides a magni-fied view in addition to deflected angles of view, allowing surgeons to overcome previous impediments to addressing areas not directly within the line of sight.11

Sinonasal endoscopy and FESS have revolutionized the field of rhinology, alter-ing our understanding of both anatomy and physiology of the paranasal sinuses in addition

to changing our medical and surgical ment of paranasal sinus pathology Due to its portability, the endoscope has become an invaluable tool in the office setting for diag-nosis and postoperative care, and as outlined

manage-in this text, has allowed manage-increasmanage-ingly complex interventions to take place in the office setting

as well.11

References

1 Rathert P, Lutzeyer W, Goddwin WE Philipp

Bozzini (1773–1809) and the lichtleiter

Urol-ogy 1974;3:113–118.

2 Saxena AK History of endoscopic sinus

sur-gery In: Saxena AK, Hollworth ME, eds

Essen-tials of Pediatric Endoscopic Surgery Springer,

Berlin; 2009:3–16

3 Doglietto F, Prevedello DM, Jane JA Jr, Han

J, Laws ER Jr A brief history of endoscopic transsphenoidal surgery — from Philipp Bozzini to the First World Congress of Endo-

scopic Skull Base Surgery Neurosurg Focus

2005;19(6):1–6

4 Reuter M The historical development of

en-dophotography World J Urol 2000;18:299–

302

5 Mouton WG, Bessell JR, Madderns GJ

Look-ing back to the advent of modern endoscopy:

150th birthday of Maximilian Nitze World J

Surg 1998;22:1256–1258.

6 Nezhat C The glory days of endoscopy In:

Nezhat’s History of Endoscopy 2005: http://

laparoscopy.blogs.com/endoscopyhistory/

7 Mouret P How I developed laparoscopic

cho-lecystectomy Ann Acad Med Singapore 1996;

25:744–747

8 Satava RM Surgical robotics: the early

chron-icles Surg Laparosc, Endosc Percutan Tech

2003;12:6–16

9 Draf W Endoscopy of the Paranasal Sinuses

Berlin: Springer-Verlag; 1983:4–9

10 Messerklinger W Background and evolution

of endoscopic sinus surgery ENT Journal

1994;73(7):449–450

11 Kennedy DW Functional endoscopic sinus

surgery: technique Arch Otolaryngol 1985;

111: 643–649

12 Pownell PH, Minoli JJ, Rohrich RJ

Diagnos-tic nasal endoscopy Plast Reconstr Surg 1997;

99: 1451–1458

13 Messerklinger W Endoscopy of the Nose

Balti-more, MD: Urban & Schwarzenberg; 1978

14 Schaefer SD An anatomic approach to

endo-scopic intranasal ethmoidectomy

Laryngo-scope 1998;108:1628–1634.

2 Endoscopic Anatomy for Office-Based

Rhinology Procedures

Sarah K Wise Craig Villari John M DelGaudio

Introduction

Endoscopic paranasal sinus surgeons must

have a solid understanding of the complex

anatomic relationships of the nose and

para-nasal sinuses in order to appropriately care

for patients with disease in this area This

knowledge of paranasal sinus anatomy and

pathophysiology is often translated to

plan-ning procedural approaches to the nose and

paranasal sinuses in the office and operating

room This chapter reviews the anatomy of the

nose and paranasal sinuses, with special

atten-tion to endoscopic anatomy for office-based

rhinology procedures

Structural Framework of

the Paranasal Sinuses and

Nasal Cavity

The paranasal sinus and nasal cavity structure

has contributions from eight major bones of

the face and skull These include the maxilla,

and the ethmoid, sphenoid, and frontal bones,

which contribute to the overall shape and ated structure of the paranasal sinus cavities The nasal bones, lacrimal bones, zygomatic bones, and vomer are also important in com-pleting the bony framework of the nasal and paranasal sinus cavities The remainder of the nasal cavity structure anteriorly largely comes from the upper lateral cartilage and lower lateral cartilage of the external nose and the quadrangular cartilage of the nasal septum.The most anterior of the nasal cavity,

aer-or vestibule, is the region in which the mous epithelial surface of the facial skin tran-sitions to the moist respiratory mucosa of the nasal and paranasal sinus cavities On initial endoscopic inspection of the nasal cavity, the most prominent structures will be the inferior turbinate laterally, the nasal septum medially, and the middle turbinate a bit more poste-riorly (Figure 2–1) The turbinates are bony structures that emanate from the sidewalls

squa-of the nose (inferior turbinates) or skull base (medial, superior, and supreme turbinates) and are essentially covered by a mucosal surface on all sides, except at their bony attachment sites The middle and superior turbinates are espe-cially important landmarks for endoscopic

procedures in rhinology The middle turbinate

assists in directing the surgeon to the middle

meatus, maxillary sinus ostium, anterior

eth-moid cavity, and frontal recess The superior

turbinate is quite helpful in identifying the

natural ostium of the sphenoid sinus The

nasal septum divides the right and left sides

of the nasal cavity and is composed of the

quadrangular cartilage at its anterior aspect,

maxillary crest and vomer inferiorly, and

per-pendicular plate of the ethmoid bone

superi-orly as it attaches to the skull base Finally, the

right and left choanae denote the most

poste-rior aspect of the nasal cavities, beyond which

the nasopharynx and eustachian tube orifices

can be visualized

Middle Meatus and

Associated Structures

Middle Turbinate

As stated previously the middle turbinate

serves as an important landmark for

endo-scopic sinus dissections within the anterior ethmoid cavity and frontal recess Most sur-geons performing endoscopic paranasal sinus procedures are familiar with seeing the ante-rior free edge of the middle turbinate bor-dering the entrance to the middle meatus This middle turbinate free edge exists in the parasaggital plane The intricate structure of the middle turbinate also has components that occur in the semicoronal and semiaxial planes, as the turbinate attaches to the skull base, lamina papyracea, and lateral nasal wall These semicoronal and semiaxial components

of the middle turbinate comprise the vertical and horizontal aspects of the middle turbinate basal lamella, respectively The middle turbi-nate basal lamella divides the anterior and pos-terior ethmoid cavities (Figure 2–2)

Pneumatization of the middle turbinate occurs with some frequency.1–3 Most com-monly, we recognize pneumatization of the free, parasaggital portion of the middle turbi-nate, which is denoted as a middle turbinate

concha bullosa (Figure 2–3) However,

pneu-matization of the vertical portion of the dle turbinate may also occur; this is termed an

mid-intralamellar cell.

Uncinate Process

The uncinate process extends from the lateral nasal wall and forms a hook-shaped struc-ture with vertical and horizontal portions The vertical portion of the uncinate process attaches to the maxilla near the lacrimal bone, and its free edge extends posteriorly from this region.4 The superior attachment of the verti-cal portion of the uncinate process is variable and thus affects the drainage pattern of the frontal sinus.3,4 The most common configu-ration seen is that the superior aspect of the uncinate process attaches to the lamina papy-racea, with the frontal sinus draining medial

to this attachment, into the middle meatus

Figure 2–1. endoscopic view of the left

nasal cavity in a patient who has not had

prior sinus surgery the nasal septum (NS),

left middle turbinate (Mt), and left inferior

turbinate (It) are labeled

The superior aspect of the uncinate process

may alternatively attach to the skull base or to

the middle turbinate, in which case the frontal

sinus would drain to the ethmoid

infundibu-lum, lateral to the uncinate process

Hiatus Semilunaris and

Ethmoid Infundibulum

The hiatus semilunaris is the two-dimensional

“doorway” that forms the entrance to the

three-dimensional “space” of the ethmoid

infundibu-lum The hiatus semilunaris is bordered medially

by the posterior free edge of the uncinate

pro-cess and laterally by the structures of the lateral nasal wall and anterior ethmoid air cells The

ethmoid infundibulum has as its borders the

lamina papyracea laterally, the uncinate process anteriorly and medially, and the ethmoid bulla posteriorly The natural ostium of the maxil-lary sinus drains into the ethmoid infundibu-lum, as does the frontal sinus at times

Agger Nasi Cells

The most anterior of all ethmoid cells is the

agger nasi cell Agger nasi cells and the agger

nasi region are most commonly discussed due

do their importance in endoscopic frontal sinus dissections and appropriate drainage of the frontal sinus outflow tract The agger nasi cell is located near the confluence of the lacri-mal bones, nasal bones, and maxilla In con-sidering frontal recess dissections, the agger nasi region is anterior and lateral to the frontal sinus drainage pathway Incomplete removal

of agger nasi walls or septations may lead to obstruction of appropriate frontal sinus drain-age5 (Figure 2–4)

Figure 2–2. endoscopic view of the left

paranasal sinus cavities in a patient who

has undergone left maxillary antrostomy

and anterior ethmoidectomy the middle

turbinate is medialized, and the leading

edge of the parasaggital portion of the

middle turbinate is labeled Mt the vertical

and horizontal portions of the middle

turbinate basal lamella are labeled V and

h, respectively this picture shows all

three portions of the left middle turbinate,

which is often difficult to conceptualize the

posterior ethmoid cavity lies posterior to

the middle turbinate basal lamella (LNW =

lateral nasal wall)

Figure 2–3. Coronal Ct scan in bone window algorithm demonstrating a large right middle turbinate concha bullosa

Ethmoid Bulla

The ethmoid bulla is typically the largest of

the anterior ethmoid cells Upon dissection

of the anterior ethmoid cavity, the ethmoid

bulla is noted as a prominent protuberance

lying posterior to the vertical portion of the

uncinate process The lateral attachment of

the ethmoid bulla is the lamina papyracea It

is further bordered anteriorly by the ethmoid

infundibulum and posteriorly by the vertical

portion of the middle turbinate basal lamella

and the retrobullar recess

Ethmoid Complex

Initiating its development by budding from the middle meatus around 11 to 12 weeks

of fetal life, the ethmoid complex is the first

of the paranasal sinuses to develop logically.6,7 The ethmoid complex and lamina papyracea are ossified by 20 to 24 weeks of embryologic development.6,7 At birth, the eth-moid cells have reached their adult number, but they are not fully developed in size This makes the ethmoid complex the most mature

embryo-of the paranasal sinuses at birth.8Unlike the maxillary, frontal, and sphe-noid sinuses, each of which consists of a large cavity draining to a single ostium, the ethmoid sinus is a complex of small ethmoid sinus cells The anterior and posterior ethmoid cavities are separated by the basal lamella of the mid-dle turbinate (see Figure 2–2) The anterior ethmoid complex is bounded medially by the parasaggital portion of the middle turbinate and drains to the middle meatus The poste-rior ethmoid complex is bounded medially by the parasagittal portion of the superior turbi-nate and drains to the superior meatus.Two notable anterior ethmoid sinus cells have already been discussed: the ethmoid bulla and the agger nasi cell Another ethmoid sinus

cell of significant importance is the infraorbital

ethmoid cell, previously known as the Haller

cell, which pneumatizes along the medial inferior orbit and may narrow the maxillary sinus drainage pathway into the infundibu-lum Named cells emanating from the ante-rior ethmoid complex may also play a role in anatomic narrowing of the frontal recess For

example, the supraorbital ethmoid cell

pneuma-tizes from the ethmoid cavity superiorly and laterally over the bony orbit and has an ostium that drains posteriorly and laterally to the true frontal sinus ostium (Figure 2–5)

As stated previously, the vertical portion

of the basal lamella forms the anterior ary of the posterior ethmoid complex, and the

bound-A

B

Figure 2–4. Coronal (A) and sagittal (B)

Ct scans in bone window algorithm

demonstrating agger nasi cells (arrows)

On sagittal scan in particular, the potential

for the posterior aspect of the agger nasi

cell to narrow the frontal sinus drainage

pathway can be appreciated

superior turbinate forms the medial boundary

of the posterior ethmoid complex Superiorly,

the posterior ethmoid region is bounded by

the skull base, and laterally by the lamina

papyracea In number, the posterior ethmoid

complex typically has fewer cells than the

anterior ethmoid complex

One named posterior ethmoid cell is of

particular importance: the sphenoethmoid cell,

or Onodi cell At times confused for a

sep-tated sphenoid sinus, a sphenoethmoid cell

is posterior ethmoid cell that is pneumatized

superiorly and laterally to the true sphenoid

sinus The sphenoethmoid cell comes into

proximity of the optic nerve as it transitions from the optic chiasm and progresses toward the orbital apex In fact, with good pneuma-tization, the bony impression of the optic nerve and carotid artery may often be seen as impressions on the walls of sphenoethmoid cells Sphenoethmoid cells may occur in as many as 30% of patients and are important

to recognize to ensure appropriately thorough and safe endoscopic dissections.9

Maxillary Sinus

The infundibulum that will eventually lead to the maxillary sinus cavity begins to develop around 14 to 16 weeks of fetal development,

as an invagination into the maxillary bone.6 At

17 to 18 weeks gestation, the cavity that will become the maxillary sinus air space can be seen.10 By birth, the maxillary sinus is 10 mm

in its maximum dimension, and it continues

to aerate until it reaches its adult dimensions around age 12.8

Often, one of the initial steps in scopic sinus surgery is identification of the natural ostium of the maxillary sinus as it drains into the ethmoid infundibulum Open-ing this natural maxillary sinus ostium allows the endoscopic surgeon to view the maxillary sinus cavity, which is volumetrically the larg-est of the paranasal sinuses (Figure 2–6) The maxillary sinus has as its borders the alveolar portion of the maxillary bone anteriorly, the zygoma laterally, the pterygopalatine fossa and infratemporal fossa posteriorly, the lat-eral nasal wall medially, and the orbital floor superiorly.1

endo-It is important to note that the natural ostium of the maxillary sinus will be located within the ethmoid infundibulum, covered by the uncinate process in an unoperated patient, and out of view during routine nasal endos-copy Accessory ostia may be visible at the anterior or posterior fontanelles in as many

A

B

Figure 2–5. Coronal (A) and axial (B) Ct

scans in bone window algorithm showing

supraorbital ethmoid cells (arrows), which

drain posteriorly and laterally to the true

frontal sinus ostium

as 23% of patients.11 These anterior and

pos-terior fontanelles are found along the lateral

nasal wall (medial wall of the maxillary sinus)

in areas where the bone, connective tissue, and

mucosa are deficient, resulting in accessory

maxillary sinus ostia

Infraorbital ethmoid cells, or Haller cells,

have already been discussed These are

gener-ally anterior ethmoid cells that are found along

the medial inferior orbit and may narrow the

maxillary sinus drainage pathway Most

com-monly, infraorbital ethmoid cells originate

from the anterior ethmoid cavity, but they

may originate from the posterior ethmoid

cav-ity in as many as 12% of cases.2,12

Alterations in the expected adult volume

of the maxillary sinus may occur in certain

cases Such instances include cases of

maxil-lary silent sinus syndrome or negative pressure

phenomena and cystic fibrosis, among others

Likewise, younger children have

underdevel-oped paranasal sinus cavities with

substan-tially less aeration than a fully developed adult

In these cases, the maxillary sinus volume is

smaller with respect to the orbital volume

on the ipsilateral side, and extreme care must

be taken in dissecting around the natural illary sinus ostium to avoid orbital injury This

max-is especially true in the setting of office-based rhinology procedures, which do not offer the option of general anesthesia or muscle relax-ation to ensure that the patient is completely still during dissection of the paranasal sinuses

Frontal Sinus

As the last of the paranasal sinuses to develop, the frontal sinus is typically not aerated at birth Around the age of 4 years, the frontal sinus is 11 to 19 mm in width.8 The frontal sinus reaches its tetrahedral shape around age

12, and continues aeration into early hood.8 The borders of the frontal sinus include the anterior and posterior tables of the fron-tal bone The bony interfrontal sinus septum

adult-is located medially Laterally, the floor of the frontal sinus is composed of the orbital roof.The frontal sinus outflow tract and frontal recess are known amongst rhinologic surgeons

as challenging regions for surgical dissection and areas where stenosis and recurrence of disease often occurs The frontal recess forms

an hourglass shape where the contents of the frontal sinus contents drain into the ethmoid infundibulum or middle meatus.2 The frontal recess has as its boundaries: the frontal sinus superiorly, the nasal cavity inferiorly, the agger nasi region anteriorly, the ethmoid bulla pos-teriorly, the middle turbinate medially, and the lamina papyracea laterally (Figure 2–7).The anatomy of the frontal recess is highly variable from patient to patient, with

a number of named cells and other unnamed anatomic variants often playing a role The focus of this text on office-based rhinologic procedures does not lend itself to an exten-sive description of frontal recess anatomy for endoscopic dissection However, some of the

Figure 2–6. endoscopic view of left para­

nasal sinus cavities following endoscopic

sinus surgery the left maxillary sinus ostium

is widely patent, and the large volume of

the maxillary sinus can be appreciated

more common anatomic variants will be

men-tioned for the sake of completeness

Two main types of frontal recess cells are

located in an anterior-lateral position with

respect to the true frontal sinus ostium: agger

nasi cells and frontal cells Agger nasi cells have

already been discussed Agger nasi are the most

anterior of all ethmoid cells, pneumatizing just

superior to the lacrimal region and

encroach-ing on the frontal sinus drainage pathway

from an anterior and lateral direction (see

Figure 2–4) Second, types 1 through 4 frontal

cells which pneumatize superior to the agger

nasi cells Dependent on their classification,

frontal cells may or may not pneumatize into

the frontal sinus itself.13,14 The type 1 frontal

cell is a solitary anterior ethmoid cell located

superior to the agger nasi cell, which does

not aerate into the frontal sinus The type 2

frontal cell is defined as multiple “stacked”

cells located superior to the agger nasi cell,

which may or may not aerate into the frontal

sinus The type 3 frontal cell is a solitary large

cell, located superior to the agger nasi cell, which aerates into the frontal sinus and com-municates with the frontal recess The type 4 frontal cell is a cell located entirely within the frontal sinus, attached to the anterior table of the frontal sinus.14

Certain ethmoid cells and recesses may pneumatize into the frontal recess and are located in a posterior position with respect

to the frontal sinus drainage pathway The supraorbital ethmoid cell has previously been mentioned This is an ethmoid cell pneuma-tizing superiorly and laterally over the orbit and draining posteriorly and laterally in com-parison to the drainage of the frontal sinus

The suprabullar recess is located superior to the

ethmoid bulla when the ethmoid bulla does not come into contact with the skull base The term suprabullar recess denotes an open space,

whereas the term suprabullar cell is used when

the space is closed and forms a true cell Next,

the term frontal bulla cell is used when an

ethmoid cell pneumatizes along the posterior table of the frontal sinus and into the frontal recess Like the suprabullar cell, the ostium of the frontal bulla cell drains posterior to the ostium of the true frontal sinus

Finally, a frontal intersinus septal cell exists

when the frontal intersinus septum becomes pneumatized The frontal intersinus septal cell drains into either the right or left frontal sinus The ostium of the frontal intersinus septal cell will be located medially with respect to the true frontal sinus ostium

Figure 2–7. endoscopic view of the left

frontal sinus ostium (white arrow) following

endoscopic sinus surgery the anterior

ethmoid artery can be seen traveling

just posterior to the frontal recess, in a

posterior­lateral to anterior­medial direction

(black arrow).

which the sphenoid sinus completes its

aera-tion, certain authors note that the adult size

of the sphenoid sinus is achieved by

approxi-mately age 12.8,15

The boundaries of the sphenoid sinus

include the planum sphenoidale (a portion

of the posterior skull base) superiorly, and the

sphenoid floor and rostrum inferiorly The

thin anterior wall of the sphenoid sinus is at

the posterior extent of the nasal cavity The

posterior boundaries of the sphenoid sinus

include the sella turcica and clivus The

sphe-noid intersinus septum divides the right and

left sphenoid sinuses The sphenoid intersinus

septum is commonly oriented off-midline,

resulting in unequal volumes between the

right and left sphenoid sinus cavities

Various landmarks are often used to

iden-tify the natural ostium of the sphenoid sinus

Traditional teaching notes that the sphenoid

sinus ostium sits approximately 7 cm posterior

to the nasal spine, at a 30-degree angle

supe-riorly Endoscopically, the natural sphenoid

sinus ostium can be found 1 to 1.5 cm above

the superior aspect of the choana, between the

nasal septum and the superior turbinate.17

The sphenoid sinus is surrounded by

many vital structures, including the pituitary

gland superiorly and medially, the optic

chi-asm superior to the pituitary gland, the optic

nerves superiorly and laterally, and the carotid

arteries posteriorly and laterally The

cavern-ous sinus hcavern-ouses cranial nerves III, IV, V1, V2,

and VI and is located laterally with respect to

the pituitary gland Due to these extremely

important structures, great care must be taken

in any manipulation of the sphenoid sinus in

any setting

Skull Base

The skull base slopes from a more superior

position in the anterior lateral paranasal sinuses

to an inferior position in the medial and rior aspects The skull base also thins medially around the attachment of the medial turbinate

poste-to the skull base and cribriform plate, and has been shown to be only 0.2 mm thick in cer-tain locations.18 Use of the Keros classification system to quantify the height of the olfactory sulcus and determine potential risk for cere-brospinal fluid leak may help in planning for endoscopic paranasal sinus procedures Keros type 1 signifies an olfactory sulcus depth from

1 to 3 mm, Keros type 2 denotes a depth of 4

to 7 mm, and Keros type 3 classifies those with

a depth from 8 to 16 mm With increasing Keros depth, the theoretical risk of iatrogenic cerebrospinal fluid leak in the ethmoid region increases Solares and colleagues have noted that the most common Keros depth is Keros type 1, at approximately 83%.19

The ethmoid arteries, which emanate from the carotid artery system, also run along the ethmoid skull base The anterior ethmoid artery exits from the orbit, running in an ante-rior medial direction, and inserts medially along the ethmoid roof at the lateral lamella

of the middle turbinate (see Figure 2–7) The anterior ethmoid artery may be seen in a mes-entery below the bony skull base at times, a configuration that should be noted on imag-ing in order to prevent injury in this area

Conclusions

The nasal and paranasal sinus anatomy is complex and may be daunting to beginning surgeons However, with careful study of this anatomy, the surgeon will gain comfort in performing procedures in this region Study

of the nasal and paranasal sinus anatomy is essential to planning for procedures both in the operating room and in the office, in order

to perform complete procedures and avoid unnecessary complications

1 Bolger W Anatomy of the paranasal sinuses

In: Kennedy D, Bolger W, Zinreich S, eds

Diseases of the Sinuses: Diagnosis and

Manage-ment Hamilton, Ontario: BC Decker, Inc.;

2001:1–11

2 Stammberger H, Kennedy D, Bolger W, et

al Paranasal sinuses: anatomic terminology

and nomenclature Ann Otol Rhinol Laryngol

1995;104 (suppl 167):7–16

3 Stammberger H Functional Endoscopic Sinus

Surgery: The Messerklinger Technique

Philadel-phia, PA: BC Decker; 1991

4 Bolger W, Woodruff W, Morehead J, Parsons

D Maxillary sinus hypoplasia: classification

and description of associated uncinate

pro-cess hypoplasia Otolaryngol Head Neck Surg

1990;103:759–765

5 Kuhn F, Bolger W, Tisdal R The agger nasi

cell in frontal recess obstruction: an anatomic,

radiologic, and clinical correlation Op Tech

Otolaryngol Head Neck Surg 1991;2:226–231.

6 Wake M, Taneko S, Hawke M The early

devel-opment of sino-nasal mucosa Laryngoscope

1994;104:850–855

7 Wang R, Jiang S, Gu R The cartilagenous

nasal capsule and embryonic development of

human paranasal sinuses J Otolaryngol 1994;

23:239–243

8 Wolf G, Anderhuber W, Kuhn F

Develop-ment of the paranasal sinuses in children:

implications for paranasal sinus surgery Ann

Otol Rhinol Laryngol 1993;102:705–711.

9 Batra P, Citardi M, Gallivan R, Roh H, Lanza

D Software-enabled CT analysis of optic

nerve position and paranasal sinus

pneumati-zation patterns Otolaryngol Head Neck Surg

11 Van Alyea O The ostium maxillare: anatomic

study of its surgical accessibility Arch

Otolar-yngol 1936;24:553–569.

12 Kainz J, Braun H, Genser P Haller’s cells: phologic evaluation and clinico-surgical rele-

mor-vance Laryngorhinootologie 1993;72: 599–604.

13 Van Alyea O Frontal cells: an anatomic study

of these cells with consideration of their

clini-cal significance Arch Otolaryngol 1941; 34:

11–23

14 Bent J, Cuilty-Siller C, Kuhn F The frontal

cell as a cause of frontal sinus obstruction Am

J Rhinol 1994;8:185–191.

15 Vidic B The postnasal development of the sphenoidal sinus and its spread into the dor-

sum sellae and posterior clinoid processes Am

J Roentegenology Radium Ther Nuclear Med

Age-of the sphenoid sinus: volume assessment by

helical CT scanning AJNR Am J Neuroradiol

2000;21:179–182

18 Kainz J, Stammberger H The roof of the rior ethmoid: a place of least resistance in the

ante-skull base Am J Rhinol 1989;3:191–199.

19 Solares C, Lee W, Batra P, Citardi M Lateral

lamella of the cribiform place Arch

Otolaryn-gol 2008;134:285–289.

3 Radiology of the Nose and

Paranasal Sinuses Kristen Lloyd Baugnon

There is extreme variability in the anatomy

of the paranasal sinuses, including both

inter-patient variability, and intrainter-patient

variabil-ity (from each side of the nose to the other)

Therefore, prior to any planned sinonasal

pro-cedure, whether the procedure will be

office-based or performed in the operating room,

adequate preoperative imaging of the sinuses

and thorough understanding of the anatomy

is imperative This chapter reviews some of the

modalities available for preoperative imaging,

and review imaging findings of normal

anat-omy, as well as patients with pathology, paying

specific attention to variants or abnormalities

that may predispose the patient to

postproce-dural complications

Choice of Imaging Modality

and Technique

The mainstay of preoperative sinus imaging

has been CT (computed tomography) of the

sinuses, technology which, coincidentally,

emerged around the same time as the

incep-tion of endoscopic sinus surgery As

endo-scopic sinus surgery technology has evolved, so

has CT technology Modern generation

mul-tislice (now up to 64-slice) spiral CT scanners have the capability of performing thin section

CT scans very quickly in the axial plane, with excellent multiplanar reformation capability, without the stair-stepping artifact seen with previous generation scanners Therefore, with new generation CT scanners, there is no need

to perform direct coronal imaging, as was viously performed

pre-Current CT protocols for imaging of the sinonasal cavity include thin section axial images (0.5- to 1-mm slice thickness), with images primarily reviewed in the bone algorithm, with window width/level settings around 3000/300 HU (Hounsfield units) for adequate bony detail Sagittal and coronal reformations should always be generated, and sent to the PACS (image archiving system) for review However, radiologists and endos-copists (particularly if utilizing intraoperative image guidance), should consider reviewing the images on a 3D workstation, with the ability to localize findings in 3 planes simul-taneously, and the ability to perform oblique reconstructions, if necessary Finally, the CT protocols should also include sending a thicker sliced reconstruction set (around 2 to 3-mm slice thickness) through the sinuses, orbits, and included brain in the soft tissue windows

(WW/WL around 300/35 HU) These images

are important to review to exclude any gross

intracranial, intraorbital, or other extrasinus

extension of disease, and to assess the density

of the sinus contents, in the setting of possible

fungal sinus disease or mucocele

The decision to perform a dedicated

image guided protocol CT scan for use in

com-puter aided endoscopic sinus surgery should

be based on the discretion and experience of

the operating surgeon The instances in which

the American Academy of

Otolaryngology-Head and Neck Surgery recommends image

guided surgery include: revision sinus surgery;

distorted sinus anatomy (developmental,

post-operative, or traumatic origin); extensive

sino-nasal polyposis; pathology involving the frontal,

posterior ethmoid, and sphenoid sinuses;

dis-ease abutting the skull base, orbit, optic nerve,

or carotid artery; CSF rhinorrhea, or

condi-tions where there is a skull base defect; and

benign and malignant sinonasal neoplasms.1

The protocol is the same thin section protocol

described above However, in these scans, the

patients should be scanned on the table top (not

in a head holder), to mimic the position of the

patient in the operating room, and the tip of the

nose and ears should be included in the field of

view, for instrument registration purposes

The use of contrast with CT for the

rou-tine evaluation of sinonasal inflammatory

dis-ease is not indicated To delineate the extent of

neoplasm, or if there is a suspicion of

intraor-bital or intracranial complication or extension

of sinus inflammatory or neoplastic disease,

often contrast-enhanced MRI (magnetic

res-onance imaging) is the best study However,

in certain settings where MRI is not readily

available, or contraindicated (ie, pacemaker),

contrast-enhanced CT can be performed

MRI is not routinely performed for

preoperative sinus evaluation, as it does not

provide bony detail However, MRI has the

advantage of exquisite soft tissue resolution,

and in the setting of suspected sinonasal mass

or tumor, MRI (particularly the T2-weighted

images), can be extremely helpful in tiating between tumor and benign secretions Benign secretions on T2w imaging are very hyperintense, or bright, whereas the majority

differen-of tumors are low to intermediate signal sity (Figure 3–1) Additionally, as described above, MRI with contrast is extremely help-ful in assessing for intracranial or intraorbital extension of benign or malignant sinus dis-ease MRI is often a useful adjunct to CT in these settings, complementing the fine bony detail and anatomy information gained by the thin section CT.2 The most helpful sequences include thin section (3 to 4-mm slice thick-ness) axial and coronal T1-weighted, and T2 weighted pre-contrast images, followed by fat-saturated axial and coronal post-contrast T1-weighted images through the sinuses Fat saturation on the post-contrast images

inten-is helpful for assessing intraorbital extension and for perineural spread of disease, although

it can introduce artifacts, particularly if there

is metallic hardware or extensive dental gam MRI can also be helpful in the evaluation

amal-of patients after osteoplastic flap procedures, and is often the first line imaging for pituitary, skull base, or clival masses

Angiography is utilized in rare instances

of a suspicion of a highly vascular tumor, for possible preoperative embolization, or in rare cases of suspected vascular injury after endo-scopic surgery

Review of the CT Images

In reviewing the images, it is helpful to have

a standardized approach We prefer to assess the patient in a similar manner to the way the patient is endoscopically examined, first on one side, and then another It is helpful to first assess what, if any, prior surgeries have been undertaken The nasal cavity is then assessed, looking within the recesses and meatuses, and looking for any soft tissue mass, or significant

nasal septal or turbinate pathology Then it is

helpful to evaluate each sinus and outflow tract

individually to assess for any potential

devel-opmental or pathologic obstruction (either

related to inflammation, tumor, iatrogenic or

post-traumatic etiology) The density of the

secretions within the sinuses is assessed

Den-sity of secretions greater than muscle is

sug-gestive of complicated secretions, either due to

blood products, proteinaceous or inspissated

secretions, or fungal colonization

Nasal Cavity

The nasal cavity is best assessed in the

coro-nal plane The degree of curvature of the nasal

septum, as well as the morphology, size, and

shape of the turbinates can be seen best in

this plane Anatomic variants such as nasal

septal deviations, septal spurs, concha

bullo-sae (pneumatization of the middle turbinate),

or paradoxical curvature of the middle nates, as well as acquired/iatrogenic abnor-malities, such as nasal septal perforations,

turbi-or truncation turbi-or deviation of the turbinates, should be noted (Figure 3–2) Although these entities most often contribute to nasal airway obstruction, occasionally they may contribute

to sinus outflow tract obstruction And tainly, they can limit the endoscopic access, and may need to be addressed surgically.Additionally, the recesses of the nasal cavity are seen best in the coronal plane The two superior recesses of the nasal cavity, the olfactory (anterior) and sphenoethmoidal (posterior) recesses, are located medial to the turbinates, and the superior, middle, and inferior meatuses are seen inferolateral to the turbinates Any abnormal soft tissue in these normally air-filled potential spaces should be considered pathologic It is often difficult on

cer-CT to differentiate mucosal edema or tions within the nasal cavity from scar or even

Figure 3–1. A Ct images of a left nasal cavity soft tissue mass, seemingly extending

through the middle meatus into the maxillary sinus, filling the ethmoid air cells Note the

bony remodeling and expansion of the left lamina papyracea (thin arrow), as well as apparent destruction of the left middle turbinate and ethmoid septations (wide arrow)

these are nonspecific bony changes, and could be due to benign process such as

inverted papilloma or sinonasal malignancy the extent of tumor is difficult to assess on

Ct. B t2w MrI (note bright CSF) delineates the extent of the relatively hypointense

tumor in the left nasal cavity (thin arrow), from the hyperintense benign postobstructive secretions in the left maxillary sinus (wide arrow) Biopsy revealed adenocarcinoma.

polyposis or other soft tissue masses

Fortu-nately, these are usually relatively easy to

differ-entiate on endoscopic examination However,

certain radiologic features can be helpful in

dif-ferentiating these entities For instance, benign

secretions should layer dependently, or can

form linear bands Additionally, scar formation

or synechiae should usually be thin and linear

(weblike) The presence of nondependent soft

tissue, particularly with mass effect (adjacent

bony thinning or remodeling), is more

sug-gestive of a soft tissue mass, such as polyposis,

or other tumor or tumor-like lesion Of note,

if soft tissue is seen in the superior sinonasal cavity, one should look closely for the pres-ence of an adjacent skull base osseous defect, and if seen, the possibility of a meningoen-cephalocele should be considered Soft tissue windows looking at the intracranial contents should be reviewed, and a thin-section MRI should be considered in this setting, prior to any attempted biopsy (Figure 3–3)

*

Figure 3–2. A Coronal Ct image at

level of maxillary infundibulum showing

slight rightward nasal septal deviation

and incidental concha bullosae of the

middle turbinates (*), left greater than right

Note the normal position of the uncinate

process bilaterally (arrows). B Coronal Ct

image demonstrating left septal deviation

with large left septal spur contacting and

deforming a paradoxical middle turbinate,

with curvature in the opposite direction

compared to normal (thin arrow) Image

is posterior to the maxillary outflow tract,

which is obstructed on the left, with

unilateral sinus disease (wide arrow). C Unilateral postoperative changes in the left

sinonasal cavity postoperative changes from septoplasty, with focal septal thinning

inferiorly (thin arrow), as well as postoperative changes from left inferior and middle

turbinectomies, left uncinectomy, and maxillary antrostomy Note the chronic recurrent mucosal disease, with circumferential thickening and sclerosis of the bone surrounding

the maxillary sinus, termed osteoneogenesis (wide arrow).

C

Figure 3–3. A a 70-year-old woman

with reported history of nasal polyps

polypoid soft tissue masses in the posterior

nasal cavity, within the sphenoethmoidal

recesses bilaterally, may be mistaken for

simple nasal polyps B however, review

of the more posterior images through the

planum sphenoidale demonstrate large

osseous defects (arrows). C and D axial

and coronal soft tissue window images

demonstrate hypodensity within the inferior

left frontal lobe (thin arrows), adjacent to

the osseous skull base defect, compatible

with gliosis, and demonstrate soft tissue

herniating through the defect, isodense to

brain tissue (wide arrow), compatible with

encephalocele encephalocele also noted

on the right (protruding through an osseous

defect on a different image) MrI should be ordered to confirm E Sagittal MrI images

demonstrating large meningoencephalocele prolapsing into the nasal cavity (arrow).

E

Abnormal soft tissue within the nasal

cavity meatuses and recesses can contribute to

certain patterns of post-obstructive sinusitis,

related to the sinus drainage pathways For

instance, abnormal soft tissue within the

mid-dle meatus and hiatus semilunaris can

contrib-ute to an “ostiomeatal unit” pattern of disease,

with resultant post-obstructive mucosal

dis-ease within the ipsilateral maxillary, frontal,

and anterior ethmoid sinuses Additionally,

soft tissue within the sphenoethmoidal recess

contributes to a “sphenoethmoidal recess”

pattern of disease, with postobstructive

secre-tions within the adjacent posterior ethmoid

and sphenoid sinuses (Figure 3–4)

Maxillary Sinus

The maxillary sinus outflow tract, including

the ostium and infundibulum, is best assessed

in the coronal plane; however axial imaging

is often also helpful The uncinate process should be identified, extending superiorly from the inferior turbinate attachment to the lateral nasal wall, and its morphology, as well

as its proximity and relationship to the lacrimal duct noted Any soft tissue occlud-ing or obstructing the maxillary sinus outflow tract, should be characterized, and one should assess for extension of this soft tissue into the middle meatus Anatomic variants, includ-ing maxillary sinus hypoplasia, lateralized uncinate process, and Haller cell (infraor-bital ethmoid cell) formation should also be noted, as these can contribute to postoperative complications with uncinectomy (ie, orbital complications or nasolacrimal duct injury),

naso-or contribute to disease and/naso-or recurrent ease postoperatively, particularly in the case of untreated variant cells (Figure 3–5) The post-operative appearance of the maxillary sinus is

Figure 3–4. A Ostiomeatal unit pattern of disease Coronal Ct image demonstrating a

polypoid soft tissue mass in the left middle meatus and maxillary sinus outflow tract, with postobstructive opacification of the left maxillary, anterior ethmoid, and frontal sinuses Given unilaterality, depending on appearance on endoscopy, biopsy, and MrI should be considered. B Sphenoethmoidal recess pattern of disease polypoid soft tissue in the

right sphenoethmoidal recess, with obstruction of an adjacent posterior ethmoid air cell and the sphenoid sinus No skull base defect seen on the coronal images to suggest meningoencephalocele

variable, and dependent on the extent of

unci-nectomy and size of the maxillary sinus

oste-otomy/antrostomy Residual uncinate process

(in addition to lateralization of the middle

turbinate) has been reported to contribute to

recurrent or residual sinus disease in the

post-operative setting (Figure 3–6) Finally, any

additional medial maxillary sinus wall defect,

such as a variant accessory sinus ostium or a

surgically created nasoantral window, should

be noted, as these can potentially contribute

to sinus recirculation syndrome

Frontal Sinus

The complicated frontal recess or frontal sinus outflow tract is best seen in a combination of sagittal, coronal, and axial planes Many studies have shown the utility of paramedian sagittal images through the frontal recess, in addition

to coronal images, aiding in the understanding

of the complex three-dimensional anatomy.3–6There is extensive variability to the frontal recess anatomy, and thorough knowledge of this anatomy is imperative prior to surgery in

A

*

B

Figure 3–5. A hypoplastic maxillary sinus

(right greater than left) with lateralized

uncinate process (arrow). B Normal

position of the uncinate process and medial

maxillary sinus wall, along a vertical plane

with the medial orbital wall (arrow) also an

infraorbital ethmoid cell (or haller cell) on

the left (*), mildly narrowing the maxillary

outflow tract C early postoperative

imaging after FeSS, in a patient

complaining of diplopia packing material

in the nasal cavity bilaterally, and blood

products (hyperdense secretions) in the

maxillary sinuses Note the fracture through

the right orbital floor, with a tiny focus of

air adjacent to the inferior rectus muscle (arrow) patient’s ophthalmologic examination

was compatible with inferior rectus injury and entrapment an atelectatic or lateralized uncinate process may place the patient at risk for this postoperative complication

C

this region, due to the risk of injury to the

adjacent nasolacrimal duct, orbit, anterior

ethmoidal artery, and skull base, with

resul-tant epiphora, orbital injury, hemorrhage, and

CSF leak, respectively

Not only is the frontal sinus ostium

vari-able in size and diameter, but during

devel-opment, anterior ethmoid cells often migrate

along the course of the frontal recess, termed

“frontoethmoid cells.” The presence of these

various accessory cells contributes to the

ana-tomic complexity and potential for

obstruc-tion, and, although of no consequence in the

asymptomatic patient, should be delineated

in those patients with frontal sinus disease

Additionally, the presence of these variant cells

has been linked with recurrence of symptoms

postoperatively

In reviewing the images through the

frontal sinus, first, the frontal sinus itself is

characterized as to its degree of development

Cystic fibrosis, and other chronic sinus

dis-eases can contribute to underdevelopment or

hypoplasia of the frontal sinus The extent

of mucosal disease is then determined Next, the frontal sinus outflow tract, including the frontal sinus ostium and frontal recess extend-ing into the hiatus semilunaris, is identified in the sagittal and coronal planes, noting areas of narrowing or obstruction with soft tissue The agger nasi air cell, the most consistent vari-ant anterior ethmoid cell, reportedly present

in up to 98% of patients, is located anterior

to the frontal sinus outflow tract and middle turbinate, and is the anterior and inferior most anterior frontoethmoid cell.7 The ethmoid bulla is then identified, as the cell or group of cells just posterior to the free edge of the mid-dle turbinate, usually the anterior and inferior most anterior ethmoid cell or cells posterior to the frontal sinus outflow tract (Figure 3–7) Other variant cells are characterized accord-ing to their relationship to the agger nasi cell, the ethmoid bulla, and the frontal sinus out-flow tract These include type I through IV frontal cells which are located anterior to the frontal sinus outflow tract Cells located pos-terior to the frontal sinus outflow tract and

Figure 3–6. A postoperative appearance status post bilateral uncinectomies, wide

bilateral maxillary antrostomies, and ethmoidectomies Note the expected postoperative medialized middle turbinates B postoperative appearance status post bilateral partial

middle turbinectomies, as well as uncinectomies and maxillary antrostomies Note the

lateralization of the right middle turbinate remnant (arrow) with soft tissue laterally, in the

frontal sinus outflow tract

associated with the bulla include supraorbital

ethmoid cells, suprabullar cells, and frontal

bullar cells The degree of disease within these

cells, as well as the effect on the outflow tracts

(frontal and maxillary sinus), should be noted

In the postoperative setting, any retained or

unopened cells, particularly if diseased, should

be described, and any soft tissue or

osteoneo-genesis narrowing the outflow tract should

be identified

The anterior ethmoid artery should be

identified, and noted if it is located on a

mes-entery within the frontal recess, suspended

from the skull base (Figure 3–8) This occurs

reportedly approximately 36% of the time,

and places the patient at increased risk for

intraoperative bleeding and orbital hematoma,

as a severed vessel can retract into the orbit.8

Finally, any osseous dehiscence of the walls of

the frontal sinus (anterior or posterior table)

Figure 3–7. Sagittal (A) and coronal (B) images of the frontal sinus outflow tract Note

the agger nasi cells (*) and the partially opacified ethmoid bulla (“b”) the frontal sinus

ostium (white line) is the area of waisting between the nasofrontal process (arrow) and the posterior table of the frontal sinus the recess (dashed line) is extremely variable in its

course to the hiatus semilunaris and middle meatus, and the outflow tract is best seen in the coronal and sagittal planes Frontal cells, when present are located above the agger nasi cell, and bullar cells are located over the ethmoid bulla, posterior to the frontal sinus outflow tract

Figure 3–8. anterior ethmoid artery on

a mesentery (wide arrows) also note the

asymmetric low lying and sloping right ethmoid roof, lateral lamella, and cribriform

plate (thin arrow).

Ethmoid Sinuses

The ethmoid sinuses are best assessed in a

combination of axial and coronal planes The

extremely variable anterior and posterior

eth-moid air cells are separated by the basal or

ground lamella, which is the lateral insertion

of the middle turbinate, onto the lamina

papy-racea The anterior ethmoid air cells drain into

the middle meatus, and the posterior ethmoid

air cells drain into the superior meatus and

sphenoethmoidal recess, and mucosal disease

within the air cells should be detected, and a

source of potential obstruction elucidated, if

one exists As described above, there are

addi-tional variant ethmoid cells along the frontal

sinus outflow tract, associated with the frontal

process of the maxilla, so called “anterior

fron-toethmoid cells,” that is, type I to IV frontal

cells, as well as named anterior ethmoid cells

associated with the ethmoid bulla, so-called

“posterior frontoethmoid cells,” namely,

supra-bullar, frontal supra-bullar, and supraorbital ethmoid

cells The superior turbinate and superior

meatus are important landmarks for the geon performing posterior ethmoid dissection, and should be located

sur-Laterally, the ethmoid air cells are bound

by the thin lamina papyracea The lamina yracea may be congenitally dehiscent or, more often, is frequently fractured, with even rela-tively minor orbital trauma Any dehiscence

pap-of the lamina papyracea, particularly if there is any herniation of orbital fat, should be noted,

as this significantly increases the possibility of orbital injury and hematoma intraoperatively (Figure 3–9)

The skull base, including the ethmoid roof (or fovea ethmoidalis), thin lateral lamella and cribriform plates, should be closely inspected, to assess the morphology of the skull base, and to look for any osseous defects

A low lying or angled skull base can cantly increase the risk of skull base injury and CSF leak (see Figure 3–8) Additionally, it is not uncommon to encounter patients with congenital or acquired (often iatrogenic or post-traumatic) dehiscence in these regions,

Figure 3–9. A Note the bowing of the left lamina papyracea medially on the axial bone

window Ct images through the ethmoid air cells (arrow). B Soft tissue windows at the

same level showing herniation of orbital fat and slight bowing of the medial rectus through

the defect, into the ethmoid air cells (arrow) this increases the risk of possible orbital

injury intraoperatively

which would not only be a potential source

of CSF leak in the symptomatic patient, but

increase their risk during ESS

Finally, care should be taken to identify a

possible Onodi cell, or sphenoethmoidal cell,

a variant pneumatized posterior ethmoid cell

that extends over the native sphenoid sinus and

borders the optic nerve canal Failure to

recog-nize this cell places the patient at increased risk

for optic nerve injury Additionally, pathology

in this cell (including neoplasm, mucocele, or

sinusitis), can affect the optic nerve Finally, an

Onodi cell may distort the anatomy and

loca-tion of the native sphenoid ostium, which may

be more inferiorly and medially displaced than

its normal position.9 Axial and sagittal images

can be helpful in delineating the Onodi cell It

is helpful in the axial plane to assess the

sphe-noid sinus from inferiorly, locating the native

ostium Any septated and pneumatized cell

above the sphenoid sinus, bordering the optic

nerve canal laterally, is an Onodi cell, which

can then be confirmed in the sagittal plane

(Figure 3–10)

Sphenoid Sinuses

The degree of pneumatization of the noid sinuses is variable, and as with the fron-tal sinuses, they can be under-pneumatized

sphe-in patients with cystic fibrosis Additionally,

it is not uncommon for a patient to have

an extensively pneumatized sphenoid sinus, with pneumatization extending through the optic strut into the clinoid process The lat-ter entity may put the optic nerve at risk, if it

is not known previously, particularly in those patients undergoing extensive sphenoidotomy for endoscopic skull base tumor resection, and

in cases of bony dehiscence of the optic nerve canal Additionally, in patients undergoing

a clinoidectomy for neurosurgical approach

to a parasellar lesion, pneumatization of the clinoid process places the patient at increased risk of CSF leak (Figure 3–11A) After noting the degree of pneumatization, the amount of mucosal disease is characterized, assessing the nature and degree of disease within the native ostium and adjacent sphenoethmoidal recess

Figure 3–10. A Sagittal Ct image demonstrating a posterior ethmoid air cell

pneumatizing over the sphenoid sinus (“s”), bordering the optic nerve canal (arrow) called

a sphenoethmoidal (Onodi) cell (*). B axial Ct image showing the small native sphenoid

sinus with its ostium inferomedially on the right, and the sphenoethmoid cell laterally

In addition to assessing for dehiscence of

the walls of the optic nerve canal, any bony

defect of the internal carotid artery canal

should be noted, as injury to the carotid artery

can be a catastrophic complication, resulting

in vessel pseudoaneurysm or rupture, and

life-threatening epistaxis Insertion of the

inter-sphenoidal sinus septum on a thin carotid

canal can place the ICA at increased risk of

injury, particularly in those patients

under-going a wide sphenoidotomy for endoscopic

exposure of the skull base (Figure 3–11B)

Finally, the planum sphenoidale and

lat-eral walls of the sphenoid sinuses are carefully

assessed for any osseous defects, in both the

axial and coronal planes Focal osseous defects

in the lateral recess of the sphenoid sinus are

a common site for spontaneous CSF leak in

patients with suspected intracranial

hyperten-sion Central skull base fractures involving the

planum sphenoidale, or iatrogenic defects, are

also another common source of CSF leak.10

Tumors or Tumor-Like Conditions

As described above, upon initial review of a noncontrast sinus CT, it is important to assess any abnormal soft tissue in the nasal cavity and paranasal sinuses, and to assess specifically for any abnormal mass like soft tissue or abnormal bony erosion It often can be very difficult to differentiate between a benign or malignant process for small tumors, and endoscopy with possible biopsy is necessary in that instance

In general, the role of imaging is to assess for aggressive features of a sinonasal soft tissue mass, not to arrive at a specific histologic diag-nosis Benign slow growing entities should cause bony thinning, remodeling, and expan-sion, whereas more aggressive processes usually cause bony erosion and destruction, as well as involvement of the adjacent soft tissues In the setting of any unusual bony changes, abnor-

Figure 3–11. A axial Ct image at the superior aspect of the sphenoid sinuses

demonstrating a pneumatized clinoid process on the right (thin arrow) this variant can place the patient at risk for optic nerve injury (note the proximity to the optic nerve — wide

arrow), as well as at risk for CSF leak during craniotomy. B Intersphenoidal sinus septum

inserting on a thin left carotid canal this variant can place the carotid artery at increased risk of injury with wide sphenoidotomy and resection of the intersphenoidal sinus septum