Clinical and Stroboscopic evaluation of vocal cord function
before and after thyroid surgery.
Year : 2019 | Volume : 7 | Issue : 2 Page : 62-66
Kondamudi D1, Apoorva Reddy. N2, 2, Asheesh Dora Ghanpur,3, Balakrishnan R4
1 Senior resident, TMH Mumbai,
2 Senior resident, ESIC Medical College Gulbarga,
3 Assistant Professor in ENT, Prathima Institute of Medical Sciences, Karimnagar,
4 Professor and Head, Department of ENT, KMC Manipal.
*Corresponding author: Asheesh Dora Ghanpur, Assistant Professor, Department of ENT, Prathima Institute of Medical Sciences,
Karimnagar.
Email ID: - ent.asheesh@gmail.com
Abstract
Introduction: Voice change due to injury to the
Recurrent Laryngeal nerve and the external branch of the
superior laryngeal nerve is an important complication of
Thyroid Surgery
Objectives: Video Laryngeal Stroboscopy comes in
handy for the detection of vocal cord palsies postoperatively
that may be missed on routine examination, to know the extent
of the pathology.
Methods: 100 patients with thyroid swelling who have
been evaluated and planned for thyroidectomy in a tertiary
care centre between June 2016 to June 2018 were taken as
subjects for this prospective observational study. Clinical
examination and Video Laryngeal Stroboscopy were done pre
operatively and compared to the same on third post-operative
day and 1month following surgery.
Results: Preoperative Video Laryngeal Stroboscopy was
normal in all subjects. 26 out of 100 subjects had subjective
postoperative voice change of various degrees. Out of 26
patients, 22 were diagnosed to have Recurrent Laryngeal Nerve
palsy and 4 with Superior Laryngeal Nerve palsy .Most common
symptoms post-surgery were Voice fatigue in 26% followed by
decreased pitch range in 13% and hoarseness in 6% cases.
Bowing of vocal cords was seen in 4 subjects (4%), Asymmetry
of travelling mucosal wave (slight to severe) in 8 subjects (8%),
incomplete glottis closure in 6 subjects (6%).
Conclusion: Video Laryngeal Stroboscopy is a useful tool
in evaluation of patients with suspected laryngeal paralysis.
Paralysis of Superior Laryngeal Nerve, Recurrent Laryngeal
Nerve or both results in asymmetric laryngeal vibration that is
easily identified by even inexperienced observers using
Stroboscopy in an otherwise normal rigid telescopy of larynx.
Keywords: Recurrent laryngeal nerve palsy,
Stroboscopy, Thyroidectomy
MAIN TEXT
INTRODUCTION
One of the common squeal we encounter after
thyroidectomy is voice change due to various degrees of injury
to the recurrent laryngeal nerve and the external branch of
the superior laryngeal nerve. When performing thyroid
surgeries, the effect on the voice is of great concern. Video
Laryngeal stroboscopy is arguably the most important clinical
tool for the evaluation of voice disorders but it is not routinely
done as a part of pre-operative evaluation of Thyroid patients.
Video Laryngeal Stroboscopy is essential for the detection of
vocal cord palsies postoperatively as symptomatic assessment
and radiographic evaluation are insufficient. As the incidence
of invasive thyroid disease is increasing, preoperative
stroboscopic evaluation of vocal cords is valuable tool to not
only know the extent of the pathology but also to predict the
outcome of the surgery.
AIMS AND OBJECTIVES:
To outline the importance of Video Laryngeal
Stroboscopy in assessing the status of Vocal cords in thyroid
disease before undertaking surgery. To outline the importance
of Video Laryngeal Stroboscopy in early and prompt diagnosis
of Recurrent Laryngeal Nerve palsy.
MATERIALS AND METHODS
All patients presenting to ENT outpatient department
with a thyroid swelling and who were evaluated and planned
for surgery between June 2016 to June 2018 were taken as
subjects for this prospective observational study. Institutional
Ethics Committee (IEC) clearance obtained before undertaking
the study.
Parameters assessed during examination
2 were
Fundamental frequency is measured by using the strobe unit
and is used to set the frequency of the light flashes, periodicity, amplitude (amplitude refers to the lateral excursion of the vocal
folds during their displacement away from the midline during
oscillation.), symmetry, glottic closure, mucosal wave,
estimated speed of glottic wave.
Inclusion criteria were patients of all ages with thyroid
disease and are treated by hemithyroidectomy, Completion/
total thyroidectomy. Exclusion criteria were pre-existing
laryngeal or vocal cord pathology. Co-morbidities that may
affect stroboscopy instrumentation usage like inadequate
mouth opening, cervical spine problems
A Video Laryngeal Stroboscopy unit consists of a
Stroboscopic light source, Microphone, Video camera,
Endoscope and Video recorder. Recent research has suggested
that the application of the Mallampati classification system is
useful for predicting the adequacy of transoral rigid
laryngoscopic exposure for stroboscopy
3.
For rigid strobolaryngoscopy (used in our study), topical
anesthesia (10% xylocaine spray) to the posterior tongue as
well as the oropharynx was applied. The patient leaned forward
with the neck flexed and the head extended at the atlantooccipital
joint (Kirstein position). We ensured that the
microphone is calibrated properly. With mouth open and
tongue protruded, tongue was retracted anteriorly and rigid
telescope was carefully inserted. Proper focus demonstrated
clear visualization of the subepithelial vasculature of the vocal
fold. To avoid fogging, the tip of the telescope was dipped in
antifog solution (savlon or hot water). With the vocal folds in
clear focus, we took the patient through a number of vocal
tasks using the ?ee sound. This should be done at low, midrange,
and high frequency pitches as well as different volumes.
Movement of arytenoid and vocal fold mobility, glottis closure
pattern, mucosal wave and pliability were noted.
DATA acquisition: Detailed history and clinical
examination were done as per the proforma designed for the
study. History of previous neck explorations, symptoms
suggestive of an impairment of VF mobility, the suspected
pathology of the thyroid disease (benign or malignant) was
verified.
Preoperative Rigid telescopy of larynx and Video
Laryngeal Stroboscopy were performed and findings recorded.
Postoperative rigid telescopy and Video Laryngeal Stroboscopy
were performed on the postoperative day 03 and later at one
month following the surgery in all subjects in sitting position
with a rigid 70 degree scope Subjects were asked to phonate
?eee using various pitches and the images were recorded and
various paramateres mentioned above were documented as
follows.
Mobility: Normal-Bilateral Vocal folds mobile, Unilateral
vocal fold palsy (UVFP), Bilateral vocal fold palsy (BVFP).
Stroboscopic Parameters used for assessment:
1.Symmetry- Normal, Mild, Moderate and Severe asymmetry
2. Amplitude- Normal, Mild, Moderate, Severe
3.Periodicity- Normal, aperiodic
4.Nonvibratory segments- None, Anterior
one third, Middle one third, Posterior one third
5.Duration of closure – Predominantly closed, Predominantly open, Half open and Half closed
6.Closure pattern- Hour glass, Spindle,
Posterior glottic chink, Anterior glottis chink, Complete closure,
Complete non closure
Findings indicating External Branch of Superior
Laryngeal Nerve Palsy: Bowing and Inferior displacement of
vocal cord, Rotation of posterior glottis towards paralysed side4.
Findings indicating Recurrent Laryngeal Nerve Palsy:
Asymmetry of travelling wave motion(slight to severe),
Incomplete Glottic closure(mild to severe), Extent of the wave
excursion along the vocal fold mucosa, Lateral displacement
of vocal fold on vibration, Estimated speed of glottis
wave(Absent wave on paralysed side)
5.
Thyroid Surgery was performed according to standards
based on the recommendations of the American society of
surgeons.
6,
7,
8 Identification of the Recurrent Laryngeal Nerve
was mandatory and was attempted in all patients.
Intraoperative neuromonitoring was not performed.
Statistical Methods: Demographic data was charted
using diagrammatic representation. Data was analysed SPSS,
version 16.0.
RESULTS
Overall 26 out of 100 subjects had subjective
postoperative voice change of various degrees. Most common
symptoms complained were Easy Voice fatigue seen in 26% of
the subjects. Decreased pitch range was seen in 13%,
Hoarseness was noticed in 6 (6%), Preoperative
Videostroboscopy was NORMAL in all subjects. Postoperative
Videostroboscopy was done on Post operative day 3 and at 1
month following surgery. On Postoperative Video Laryngeal
Stroboscopy Bowing of vocal cords- 4 cases (4%), Asymmetry
of travelling mucosal wave (slight to severe) in 8 subjects (8%)
Incomplete glottis closure in 6 subjects (6%).
PATIENTS WITH RECURRENT LARYNGEAL NERVE PARALYSIS:
Glottic closure: Mild to moderate incomplete-4 cases,
severely incomplete 2 cases. Glottic wave : Extent excursion
along vocal fold mucosa was Symmetric in none, Mild to
moderate asymmetry in 4 cases, Marked asymmetry in 6 cases
and was absent on paralysis side 4 cases.
![](table26.png)
Recurrent Laryngeal Nerve Palsy can be complete or
incomplete. A complete paralysis is that in which all the motor
units of the nerve, as in the case of the surgical section, are
affected. In incomplete paralysis, some of the motor units in
the nerve are affected, as in mechanical pressure, straining of
the nerve, or heat damage from thermocauterisation during
thyroidectomy.
In complete paralysis the vocal fold is immobile and has
no muscle tone. The glottis does not close completely. The
movements of the vocal folds are asymmetrical. The mucosal
wave is absent or reduced in the paralytic vocal fold.
In incomplete paralysis, the vocal fold is slightly mobile
and has some muscular tone. Glottic closure is better. The
mucosal wave is reduced in the affected fold and the bilateral
waves are asymmetrical. Abnormalities in the vibratory pattern
become more apparent as the number of affected neurons
increases.
In Superior Laryngeal Nerve Palsy, Anterior glottis moves
to the affected side because of the tone of the unaffected
cricothyroid muscle. The mucosal wave is asymmetrical as the
wave is late in the affected fold.12 in our series, Preoperative
Video Laryngeal Stroboscopy and rigid telescopies were normal
in all patients. There were no false positive abnormalities. 4
subjects with incomplete Recurrent Laryngeal Nerve Palsy and
3 with Superior Laryngeal Nerve palsy had no symptoms. 4
cases of Superior Laryngeal Nerve palsy and 6 with incomplete
Recurrent Laryngeal Nerve palsy were not diagnosed by rigid
telescopy of larynx. These were subsequently diagnosed on
Video Laryngeal Stroboscopy post operatively. In the evaluation
on the third postoperative day, rigid telescopy showed
abnormalities of movement in the vocal cords resembling vocal
cord palsy in 16 out of 26 patients .Video Laryngeal Stroboscopy
on the second postoperative day diagnosed the 4 Superior
Laryngeal Nerve palsy (which looked normal on rigid telescopy
of larynx), 8 incomplete inferior laryngeal nerve palsies , and
three complete inferior laryngeal nerve palsy (patients with
the injured recurrent nerve),in those 26 patients with vocal
disturbances. Thus incomplete Recurrent Laryngeal Nerve
palsies and two laryngeal injuries were found only by Video
Laryngeal Stroboscopy and they were all asymptomtic. The
present study highlights the efficiency of Video Laryngeal
Stroboscopy in the early diagnosis of nerve palsies. At the end
of first month, only patients with a cut nerve still had a weak
voice. Video Laryngeal Stroboscopy and laryngoscopy showed
that the right vocal cord was adducted medially and the left
cord also hyper adducted to compensate for the right. The
other 16 patients with symptoms had complete relief of their
vocal disturbances. The Video Laryngeal Stroboscopy and
laryngoscopy of those patients at one month were within
normal limits. Incomplete paralysis of the Recurrent Laryngeal
Nerve with a small number of affected neurons causes little
abnormality in the movement of the vocal fold, which can be
asymptomatic, and can easily be missed rigid laryngoscopy.
Asymmetrical mucosal waves seen on Video Laryngeal
Stroboscopy provide the diagnosis. Nevertheless, 6 of our
patients who had incomplete paralysis on Video Laryngeal
Stroboscopy had insignificant findings on rigid telescopy. The
displacement of the anterior glottis occurs in severe cases of
Superior Laryngeal Nerve paralysis. Asymmetry in the mucosal
wave is the only finding in mild cases. Rigid telescopy of larynx
was normal in 4 patients who had incomplete Superior
Laryngeal Nerve paralysis on Video Laryngeal Stroboscopy.
However, it is not possible to differentiate between complete
and incomplete paralysis, so as to assess the prognosis.
Recurrent Laryngeal Nerve Palsy was temporary in those with
incomplete palsy on Video Laryngeal Stroboscopy, but was
permanent in the one with complete palsy on Video Laryngeal
Stroboscopy. Video Laryngeal Stroboscopy was successful not
only in the diagnosis of vocal disturbance after thyroidectomy,
but also in assessing the outcome of the injury to the Recurrent
Laryngeal Nerve Palsy.
Incomplete paralysis of the Recurrent Laryngeal Nerve
on Video Laryngeal Stroboscopy means neuropraxia that is, a
temporary and reversible block of nerve conduction. Complete
paralysis of the Recurrent Laryngeal Nerve means neurotmesis
or axonotmesis, in which some regeneration may occur, but
complete recovery cannot be expected. Rigid telescopy of
larynx and Video Laryngeal Stroboscopy are useful in routine
postoperative use for diagnosis of nerve palsies and, cases of
neuropraxic injury may be misdiagnosed or undiagnosed with
rigid telescopy of larynx .Video Laryngeal Stroboscopy has
certain obvious advantages when compared with a rigid
telescopic examination of larynx, both in differential diagnosis
of the vocal disturbances and in the prediction of the outcome
of the paralysis. Hence routine usage of Video Laryngeal
Stroboscopy, especially postoperative should be done in
thyroidectomies and in cases with abnormalities of the voice,
or damage seen on indirect laryngoscopy, rigid telescopy or
both.
CONCLUSION
Laryngeal stroboscopy is a useful tool in evaluation of
patients with suspected laryngeal paralysis. Paralysis of
Superior Laryngeal Nerve, Recurrent Laryngeal Nerve or both
results in asymmetric vocal cord vibration that is easily
identified by even inexperienced observers. The mucosal wave
has a greater velocity and further travels along the mucosa on
the normal vocal fold. The probable cause for these vibratory
findings is the reduced stiffness in the paralyzed cord, which
reduces the velocity and extent of the travelling mucosal wave.
Stroboscopy can reliably identify the abnormal vibratory
pattern in an otherwise normal indirect laryngoscopy and rigid
telescopy of larynx. Our experience suggests stroboscopy
cannot reliably distinguish Recurrent Laryngeal Nerve paralysis
from vagal paralysis. Studies are being planned in canine model
to better quantify the travelling wave findings in laryngeal
paralysis.
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How to cite this article : Dheeraj Kondamudi , Apoorva
Reddy N, Asheesh Dora Ghanpur, Balakrishnan R.
Perspectives in Medical Research 2019; 7(2):62-66
Sources of Support: Nil,Conflict of interest:None declared