To evaluate the prognosis value of facial nerve conduction study in Bell’s palsy outcome. A descriptive and cross-sectional study using electro diagnostic data and medical chart review on 29 patients diagnosed with Bell’s palsy in Department of Neurology, Military Hospital 103 from January 2017 to December 2017, were evaluated using the facial nerve grading system 2.0 (FNGS) during their initial visit and on day 20 and day 40.
Trang 1FACIAL NERVE CONDUCTION STUDY IN THE PROGNOSIS OF
BELL’S PALSY OUTCOME BY USING FNGS 2.0
Le Trung Duc*; Nguyen Duc Thuan*; Nguyen Tien Son*
SUMMARY
Objectives: To evaluate the prognosis value of facial nerve conduction study in Bell’s palsy outcome Subjects and methods: A descriptive and cross-sectional study using electro diagnostic data and medical chart review on 29 patients diagnosed with Bell’s palsy in Department of Neurology, Military Hospital 103 from January 2017 to December 2017, were evaluated using the facial nerve grading system 2.0 (FNGS) during their initial visit and on day
20 and day 40 We performed facial nerve conduction studies (NCS) in the first 5 days and on the 20th day Facial NCS results were classified into amplitude loss less than 75% and amplitude loss 75% or greater to stratify into good or poor prognosis Results: In the first 5 days, the amplitude loss was less than 75% in 13 patients (44.8%) and 75% or greater in 16 patients (55.2%) On the 20th day, the amplitude loss was less than 75% in 8 patients (27.6%) and 75%
or greater in 21 patients (72.4%) There was a statistically significant correlation between patients with compound muscle action potential (CMAP) amplitude difference 75% or higher in the first 5 days and those with FNGS 2.0 equal to grade 3 or above (Chi Square = 9.311, p = 0.004) There was a statistically significant correlation between patients with CMAP amplitude difference 75% or higher on 20th day and those with FNGS 2.0 equal to grade 3 or above (Chi
square = 19.859, p < 0.001) Conclusion: The facial nerve conduction study is a valuable tool for
follow-up and recovery prognosis of the Bell’palsy, especially in the subacute phase Based on our data, poor prognosis is predicted in patients with more than 75% amplitude loss at both the initial and the follow-up facial NCS
* Key words: Bell’s palsy; Facial nerve; Nerve conduction study
INTRODUCTION
Bell’s palsy, defined as an acute
unilateral peripheral facial nerve palsy
without detectable cause, is the most
common cause of facial nerve palsy
FNGS 2.0, first introduced in 2009,
was designed to overcome the limitations
of existing grading systems like House
Brackmann, Sunnybrook
Electrophysiological methods have been used to determine the severity of nerve degeneration and prognosis in IPFP since the 1960s Currently, the nerve excitability test, NCS, blink reflex test and needle electromyography are used to determine the prognosis
The purpose of our study was: To
evaluate the prognosis value of facial nerve conduction study in Bell’s palsy outcome by using FNGS 2.0
*
Corresponding author: Nguyen Duc Thuan (thuanneuro82@gmail.com)
Date accepted: 21/03/2018
Trang 2SUBJECTS AND METHODS
This is a prospective study on the patients
with Bell’s palsy between the period of
January 2017 to December 2017 in Neurology
Department of Military Hospital 103 The
study included 29 patients diagnosed with
idiopathic peripheral facial paresis Patients
who were characterized by acute onset,
isolated, unilateral, peripheral facial nerve
paralysis without detectable cause were
included The clinical diagnosis of idiopathic
peripheral facial paresis was based on the
ICD-X criteria Exclusion criteria were
previous history of peripheral or central
facial paralysis, diabetes and other peripheral neuropathies All patients were treated with methylprednisolon 80 mg/day IV within 7 days and neurotrophic drugs after the onset of disease The initial dose of methylprednisolon was administered for a week and then tapered gradually over the following week Clinical evaluation comprised the FNGS and facial NCS was conducted in the first 5 days and 20th and
40th days after paralysis onset We defined a good outcome as the FNGS grade I or grade II and a poor outcome as FNGS grade 3 or higher
Table 1:
FNGS 2.0
Degree of secondary movement
2 Slight weakness
> 75% of normal
Slight weakness >
75% of normal Complete closure with mild effort
Slight weakness >
75% of normal
Slight weakness >
75% of normal
Slight synkinesis, minimal contracture
3 Obvious
weakness >
50% of normal
Resting
symmetry
Slight weakness >
75% of normal Complete closure with maximal effort
Slight weakness >
75% of normal Resting symmetry
Slight weakness >
75% of normal Resting symmetry
Obvious synkinesis, mild
to moderate contracture
4 Asymmetry at
rest < 50% of
normal
Cannot close
completely
Asymmetry at rest
< 50% of normal
Asymmetry at rest < 50% of normal
Asymmetry at rest < 50% of normal
Disfiguring synkinesis, severe contracture
movement
Trace movement Trace
movement
Trace movement
6 No movement No movement No movement No movement
Trang 3Grade Total score
VI 24
* Electrophysiological assessment:
All patients underwent facial NCS on
admission using Natus VikingQuest
Facial NCS was performed first on the
intact side and then repeated on the
affected side Potentials were recorded
from each of the frontal, orbicularis oris
and orbicularis oculi muscles The stimulation
intensity ranged from 30 to 45 mA The
current intensity was increased stepwise
until there was no further incrase in the
amplitude of the diphasic myogenic CAP
An additional 10% of current was added
to ensure supramaximal stimulation The
amplitude of the CMAP in the affected
side and the intact side were compared
The value of 75% or less versus more
than 75% amplitude loss was considered
a cut-off point for prognosis
*Statistical analysis:
Statistical analysis of the data was
performed using Statistical Package for
Social Sciences software package
Sensitivity, specificity, positive predictive
value and negative predictive value were
caculated to determine the prognostic
value of facial NCS The Mann-Whitney
test was used to compare the facial NCS
result with clinical improvement The Mc
Nemar test was used to compare the
performances of facial NCS in the first 5
days with those on the 20th day The significance level was set at p < 0.05
RESULTS
1 Clinical evaluation
Twenty nine patients (19 males and 10 females; mean age 44.3 years, range:
20 - 79 years) diagnosed with Bell’s palsy were studied In the first 5 days, the clinical evaluation according to the FNGS revealed that 4 patients (13.8%) was in grade III, 6 patients (20.7%) in grade IV, 18 (62%) in grade V and 1 patien (3.5%) in grade VI
On the 40th day, the final outcome based
on FNGS was grade I in 17 patients (58.6%), grade II in 6 patients (20.7%) and grade III in 6 patients (20.7%)
12 out of 19 patients (63.1%) with complete facial nerve paralysis returned
to normal function All patients with incomplete lesions had normal facial nerve function in the 40th day
2 NCS
On the first 5 days, the amplitude loss was less than 75% in 13 patients (44.8%) and 75% or greater in 16 patients (55,2%) On the 20th day, the amplitude loss was less than 75% in 8 patients (27.6%) and 75% or greater in 21 patients (72.4%)
Trang 42 0
6
0
5
10
15
20
25
Figure 1: Relationship between FNGS 2.0 grade on the day 40 and CMAP amplitude
difference on the day 20
Sensitivity, specificity, PPV and NPV of NCS results are presented in table I Poor prognosis was defined as a positive test result, good prognosis was defined as a negative test result For initial NCS, we found a PPV and NPV of 46% and 93.8%, respectively After a period of 15 days, PPV and NPV of follow-up NCS increased to 75% and 95.2%
Table 2: Predictive value of facial NCS
There was a statistically significant
relationship between patients with CMAP
amplitude difference 75% or higher in the
first 5 days and those with FNGS 2.0
equal to grade 3 or above (Chi square =
9.311, p = 0.004)
There was a statistically significant
relationship between patients with CMAP
amplitude difference 75% or higher on
20th day and those with FNGS 2.0 equal
to grade 3 or above (Chi square = 19.859,
p < 0.001)
Mc Nemar's test was used in order to
compare NCS in the first 5 days and NCS
on 20th day NCS on the 20th day show the best performance (p < 0.05)
DISCUSSION
For patients with Bell’s palsy in the
acute phase, the NCS showed reduced
amplitudes of CMAP in the frontal, orbicularis oculi muscle and orbicularis oris muscle on the affected side and the
normal amplitudes on the intact side
Statistically, the disease course was described in a study by Peitersen E [3] on 1.011 patients One-third had an incomplete paralysis, two-thirds had complete paralysis
Trang 594% of the patients with incomplete lesions
returned to normal function, while only
60% of those with clinically complete
lesions returned to normal function
Among 19 patients with complete facial
nerve paralysis in the present study, 12
patients (63.1%) returned to normal
function All of patients with incomplete
lesions had normal facial nerve function
on the 40th day, which reveals that we had
a representative population, according to
previous studies
Jabor et al reported that prognosis is
favorable if some recovery is seen within
the first 21 days of onset [4] In our study,
we performed facial NCS in the first 5
days and on the 20th day There was a
statistically significant relation between
patients with CMAP amplitude difference
75% or higher both in the first 5 days and
on day 20 and patients with poor recovery
on the 40th day after onset However,
NCS results on day 20 illustrate a higher
prognosis value than those in the first 5
days (McNemar test, p < 0.05), which is
probably consistent with axonal recovery
and collateral sprouting process of facial
nerve Our results are consistent with
those that reported CMAP amplitude
differences of ≥ 75% indicate a poor
prognosis at 3 months [7] Ozgul et al
investigated the disease 3 months after
the onset, which indicates similar findings
Besides, some studies reported 50% and
90% CMAP amplitude difference in the
second month and in the third week
respectively, which indicated poor prognosis
unlike other studies [1, 2] In our study,
we utilize FNGS 2.0 Few studies have
compared FNGS 2.0 and House Brackmann
grading systems and confirmed whether FNGS could evaluate facial nerve function more detail and accuracy than House Beckmann scale [5, 6]
CONCLUSION
The facial NCS is a valuable tool for follow-up and recovery prognosis of the Bell’palsy, especially in the subacute phase Based on our data, poor prognosis
is predicted in patients with more than 75% amplitude loss at both the initial and the follow-up facial NCS
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1 Fisch U Surgery for Bell’s palsy Arch
Otolaryngol 1981, 107, pp.1-11
2 Danielides V, Skevas A, Van Cauwenberge
P A comparison of electroneuronography with
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3 Peitersen E The natural history of Bell's
palsy Am J Otol 1982, 4, p107
4 Jabor M.A, Gianoli G Management of
Bell's palsy J La State Med Soc 1996, 148, p.279
5 Ho Y Lee, Moon S Park Agreement
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6 Jeffrey T Vrabec, Douglas D Backous
FNGS 2.0 Otolaryngology-Head and Neck Surgery 2009 140, pp.445-450
7 Engström M, Jonsson L, Grindlund M, Stålberg E House-Brackmann, Yanagihara
Grading scores in relation to electroneurographic results in the time course of Bell’s palsy Acta Otolaryngol 1998, 118, pp.783-789