Re: Prognostic value of electroneurography in Bell’s palsy and Ramsay–Hunt’s syndrome
2
4 Finally, in the current climate of financial constraints, we found it encouraging of the authors to acknowledge at least the cost-effectiveness of our technique and with respect to the advantage of their audible stimulus. We must say that we have worked with a number of deaf surgeons, and the noise in the operative theatre does not help even with full volume! Conflict of interest None to declare. Tahery, J. & Natt, R.S. Department of Ear, Nose & Throat Surgery, Countess of Chester Hospital NHS Foundation Trust, Liverpool Road, Chester CH2 1UL. E-mail: [email protected] Reference 1 Kasbekar A.V. & Srinivasan V.R. (2010) Fibre-optic laryngoscope and endotracheal tube assembly:a robust method of monitoring recurrent laryngeal nerve function during thyroid surgery: how we do it. Clin Otolaryngol. 35, 508–509 Re: Prognostic value of electroneurography in Bell’s palsy and Ramsay–Hunt’s syndrome 8 November 2010 Sir, I read with great interest the article written by Lee et al. 1 entitled ‘Prognostic value of electroneurography in Bell’s palsy and Ramsay–Hunt’s syndrome’. They concluded that the electroneurography (ENoG) values obtained between days 7 and 10 for Bell’s palsy, and between days 10 and 14 for herpes zoster oticus, were not precise prog- nostic indicators. Historically, ENoG has been important ever since early surgery was recommended by Fisch 2 . Sub- sequently, Ganz et al. 3 supported early surgery although May et al. 4 did not. The main difference was the range of decompression surgery. I would like to emphasise that masseter muscle volume conduction during ENoG may have an impact on the result. According to Fisch 2 and May et al., 4 when ENoG is <10%, it becomes a poor prognostic factor and an indication for surgery. However, if volume conduction from the masseter muscle is disre- garded, ENoG can be overestimated by over 10%, even when the real value is <10%. There are three methods to avoid masseter volume conduction. First, palpate or observe the masseter muscle during ENoG. Second, do two channel recordings, one on the nasalis and the other on the masseter. Third, move the stimulation point to the zygomatic arch point and then move medially or lat- erally. If the amplitude increases when the stimulation point is moved laterally or reduces when moved medially, then it could be attributed to volume conduction from the masseter muscle. If the amplitude change is to the contrary, then it could be attributed to genuine conduc- tion from the nasalis (Fig. 1). I am uncertain if Lee et al. 1 precluded the possibility of masseter muscle volume con- duction. ENoG is subject to dynamic time delay, and even when ENoG is 0%, we can expect good prognosis with detectable voluntary MUAP. While early surgery remains controversial, the prognostic value of ENoG obtained within the first 2 weeks should be respected. Fig. 1. Three methods can monitor masseter volume conduc- tion. First, palpate or observe of masseter muscle during electro- neurography. Second, do two channel recordings, one on the nasalis and the other on the masseter. Third, move the stimula- tion point to the zygomatic arch point and move medially or laterally from that point. C, concentric needle electrode; R, recording electrode; S, stimulation electrode. CORRESPONDENCE: LETTERS 88 Correspondence Ó 2011 Blackwell Publishing Ltd • Clinical Otolaryngology 36, 86–100
Transcript of Re: Prognostic value of electroneurography in Bell’s palsy and Ramsay–Hunt’s syndrome
4 Finally, in the current climate of financial constraints,
we found it encouraging of the authors to acknowledge at
least the cost-effectiveness of our technique and with
respect to the advantage of their audible stimulus. We
must say that we have worked with a number of deaf
surgeons, and the noise in the operative theatre does not
help even with full volume!
Conflict of interest
None to declare.
Tahery, J. & Natt, R.S.Department of Ear, Nose & Throat Surgery,
Countess of Chester Hospital NHS Foundation Trust,
Liverpool Road, Chester CH2 1UL.
E-mail: [email protected]
Reference
1 Kasbekar A.V. & Srinivasan V.R. (2010) Fibre-optic laryngoscope
and endotracheal tube assembly:a robust method of monitoring
recurrent laryngeal nerve function during thyroid surgery: how
we do it. Clin Otolaryngol. 35, 508–509
Re: Prognostic value of electroneurography in Bell’s palsyand Ramsay–Hunt’s syndrome
8 November 2010
Sir,
I read with great interest the article written by Lee et al.1
entitled ‘Prognostic value of electroneurography in Bell’s
palsy and Ramsay–Hunt’s syndrome’. They concluded
that the electroneurography (ENoG) values obtained
between days 7 and 10 for Bell’s palsy, and between days
10 and 14 for herpes zoster oticus, were not precise prog-
nostic indicators. Historically, ENoG has been important
ever since early surgery was recommended by Fisch2. Sub-
sequently, Ganz et al.3 supported early surgery although
May et al.4 did not. The main difference was the range of
decompression surgery. I would like to emphasise that
masseter muscle volume conduction during ENoG may
have an impact on the result. According to Fisch2 and
May et al.,4 when ENoG is <10%, it becomes a poor
prognostic factor and an indication for surgery. However,
if volume conduction from the masseter muscle is disre-
garded, ENoG can be overestimated by over 10%, even
when the real value is <10%. There are three methods to
avoid masseter volume conduction. First, palpate or
observe the masseter muscle during ENoG. Second, do
two channel recordings, one on the nasalis and the other
on the masseter. Third, move the stimulation point to
the zygomatic arch point and then move medially or lat-
erally. If the amplitude increases when the stimulation
point is moved laterally or reduces when moved medially,
then it could be attributed to volume conduction from
the masseter muscle. If the amplitude change is to the
contrary, then it could be attributed to genuine conduc-
tion from the nasalis (Fig. 1). I am uncertain if Lee et al.1
precluded the possibility of masseter muscle volume con-
duction. ENoG is subject to dynamic time delay, and
even when ENoG is 0%, we can expect good prognosis
with detectable voluntary MUAP. While early surgery
remains controversial, the prognostic value of ENoG
obtained within the first 2 weeks should be respected.
Fig. 1. Three methods can monitor masseter volume conduc-
tion. First, palpate or observe of masseter muscle during electro-
neurography. Second, do two channel recordings, one on the
nasalis and the other on the masseter. Third, move the stimula-
tion point to the zygomatic arch point and move medially or
laterally from that point. C, concentric needle electrode;
R, recording electrode; S, stimulation electrode.
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88 Correspondence
� 2011 Blackwell Publishing Ltd • Clinical Otolaryngology 36, 86–100
I hope that the influence of masseter volume conduction
will be verified in the near future study.
Conflicts of interest
None declared.
Kim M.-W. & Kim E.-H.Department of Rehabilitation Medicine, College of Medicine,
Incheon St Mary’s Hospital, The Catholic University of Korea,
Seoul, Korea.
E-mail: [email protected]
References
1 Lee D.H., Chae S.Y., Park Y.S. et al. (2006) Prognostic value of
electroneurography in Bell’s palsy and Ramsay-Hunt’s syndrome.
Clin. Otolaryngol. 31, 144–148
2 Fisch U. (1981) Surgery for Bell’s palsy. Arch. Otolaryngol. 107, 1–11
3 Gantz B.J., Rubinstein J.T., Gidley P. et al. (1999) Surgical man-
agement of Bell’s palsy. Laryngoscope 109, 1177–1188
4 May M., Klein S.R. & Taylor F.H. (1985) Idiopathic (Bell’s) facial
palsy: natural history defies steroid or surgical treatment. Laryn-
goscope 95, 406–409
Response to Kim and Kim
15 November 2010
Sir,
First, I would like to thank Kim and Kim for their
comments on our article.
One of the factors that affect the surface electromy-
ography (EMG) is volume conduction. Volume conduc-
tion or far-field potential refers to the source of the
compound muscle action potential (CMAP) far from
the surface electrode. For facial EMG, the corrugators,
temporalis or masseter muscles are the common source
of volume conduction. When stimulating the facial
nerve anterior to the earlobe, it is relatively easy to
activate the masseter muscle directly. In patients with
facial paralysis, a volume-conducted masseter CMAP
can coincide with the expected facial nerve response’s
position and be mistaken for a facial CMAP.
Therefore, in our hospital, several techniques have
been used, including the methods that Kim and Kim
mentioned.
In response to the concerns raised by Kim and Kim, I
would like to clarify following points. In our study, we
focused just on the complete recovery of the facial paraly-
sis because most patients do not satisfy just ‘recovery’. Of
course, the ENoG (electroneurography) more than 10%
guaranteed the ‘good’ prognosis including partial recovery
in our study. Of 19 patients with Bell’s palsy and nine
patients with herpes zoster oticus, who had ENoG more
than 10% but did not recover completely, 14 and seven
patients respectively showed ‘satisfactory recovery’ in our
study. Our study showed that the recovery rate was
87.5% for Bell’s palsy and 84.2% for herpes zoster oticus,
but the complete recovery rate was reduced to 52.5% for
Bell’s palsy and 47.4% for herpes zoster oticus. That is,
our study supported the established usefulness of ENoG
and EMG.
The focus of our article was that ENoG is still valid to
predict the prognosis of facial paralysis but it is not
accurate or reliable enough to determine the prognosis
of facial paralysis quantitatively.
We did not include the voluntary motor unit action
potential (MUAP) into the analysis because EMG is the
study showing the late prognostic parameter. I agreed
that detectable voluntary MUAP is the important
prognostic parameter. I hope that the exact prognosis
of facial paralysis will be studied in a future study
analysing many clinical parameters including voluntary
MUAP.
Conflicts of interest
None declared.
Lee, D.-H.Department of Otolaryngology-Head and Neck Surgery,
College of Medicine, The Catholic University of Korea,
Seoul, Korea.
E-mail: [email protected]
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Correspondence 89
� 2011 Blackwell Publishing Ltd • Clinical Otolaryngology 36, 86–100
