PhiliPPine Journal of otolaryngology-head and neck Surgery Vol. 31 no. 1 January – June 2016
ORIGINAL ARTICLES
22 PhiliPPine Journal of otolaryngology-head and neck Surgery
ABSTRACT
Objective: To determine the risk of vocal fold paralysis in patients who underwent total
thyroidectomy with and without intraoperative recurrent laryngeal nerve identification.
Methods:
Design: Retrospective Cohort Study
Setting: Tertiary Military Hospital
Participants: Two hundred thirty seven (237) adult patients who underwent
total thyroidectomy for benign lesions based on post-operative histopathology operated on
by senior third or fourth year residents. Excluded were those who underwent lobectomy with
isthmusectomy or reoperation/completion thyroidectomy, had intrathoracic goiters, confirmed
malignancies based on post-operative histopathology, or cases wherein the RLN had to be
sacrificed due to gross involvement of the nerve caused by malignancy.
Results: Group A, wherein intraoperative identification of RLN was done, had a temporary
and permanent RLN injury incidence of 2.75% and 0.92% respectively. Group B, wherein
intraoperative identification of RLN was not done, had a temporary and permanent RLN injury
incidence of 17.19% and 12.5%, respectively. Through binary linear regression, the probability
of having temporary paralysis increases almost two-fold if the nerve is not identified, and the
probability of having permanent paralysis increases by almost nine-fold if the nerve is not
identified.
Conclusion: We recommend routine intraoperative RLN identification, which has a lower risk for
temporary and permanent vocal fold paralysis when compared to non-identification of the RLN.
Keywords: cranial nerve injuries/prevention and control, recurrent laryngeal nerve injuries, thyroid
neoplasms/surgery, thyroidectomy/adverse effects, vocal cord paralysis/prevention control
Vocal Fold Paralysis with Intraoperative Recurrent
Laryngeal Nerve Identification versus
Non-Identification of Recurrent Laryngeal Nerve
in Total Thyroidectomy:
A Retrospective Cohort Study
Andrie Jeremy Formanez, MD
Department of Otorhinolaryngology
Head and Neck Surgery
Armed Forces of the Philippines Medical Center
Quezon City, Philippines
Correspondence: Dr. Andrie Jeremy Formanez
Department of Otorhinolaryngology-Head and Neck Surgery
Armed Forces of the Philippines Medical Center
7th Floor Armed Forces of the Philippines Medical Center
V. Luna Avenue, Quezon City 0840
Philippines
Phone: (632) 426 2701 local 6172
Email: docdrie@yahoo.com
The author declared that this represents original material, that
the manuscript has been read and approved by the author, that
the requirements for authorship have been met by the author,
and that the author believes that the manuscript represents
honest work.
Disclosures: The author signed a disclosure that there are no
financial or other (including personal) relationships, intellectual
passion, political or religious beliefs, and institutional affiliations
that might lead to a conflict of interest
Philipp J Otolaryngol Head Neck Surg 2016; 31 (1): 22-25 c Philippine Society of Otolaryngology – Head and Neck Surgery, Inc.
Creative Commons (CC BY-NC-ND 4.0)
Attribution - NonCommercial - NoDerivatives 4.0 International
PhiliPPine Journal of otolaryngology-head and neck Surgery Vol. 31 no. 1 January – June 2016
ORIGINAL ARTICLES
PhiliPPine Journal of otolaryngology-head and neck Surgery 23
Iatrogenic recurrent laryngeal nerve (RLN) injury remains one
of the most common complications of thyroid surgery. Temporary
RLN injury occurs in 2.5% to 5% of thyroidectomy patients of
complications following thyroidectomy.1 Permanent RLN injury occurs
in approximately 1% to 1.5% of total thyroidectomy procedures.1
Patients with this complication suffer from different manifestations, the
least serious of which is hoarseness. However, this can be particularly
devastating in patients for whom the quality of their voice is integral to
their occupation.2 More serious manifestations include aspiration and
dyspnea, which are potentially life-threatening.3 Further hospitalization
is required to address these problems, which would have been
unnecessary had the integrity of the RLN been preserved.
The risk factors that contribute to morbidity following thyroid
surgery are well-defined, but their actual contribution is still open
to question.4 Increased extent of dissection, surgeon experience,
malignancy, underlying thyroid disease, and intraoperative technique
have been shown to affect post-thyroidectomy morbidity.5 In
addition, operation for completion6 and addition of neck dissection7
are additional risk factors for postoperative thyroid morbidity. Surgical
technique, more specifically intraoperative RLN identification, is
one of the factors which may affect the outcome of thyroid surgery,
but some surgeons still do not routinely identify the RLN as can be
gleaned from studies in India,8 Turkey,9 and China.10
In our institution, the Department of Otorhinolaryngology - Head
and Neck Surgery receives 3 - 5 referrals for hoarseness following
thyroid surgery annually. This number is significant given the number
of thyroid surgeries done per year and gives cause for alarm given the
potentially catastrophic complications of RLN injury. The significant
number of referrals warrants investigation of the possible causes.
Furthermore, to the best of our knowledge, no local data has been
published regarding the incidence and causative factors of RLN
injury following thyroidectomy. Hence, the purpose of this study is to
determine the risk of vocal fold paralysis in patients who underwent
total thyroidectomy with and without recurrent laryngeal nerve
identification.
METHODS
With Ethical Review Board (ERB) approval, this retrospective
cohort study consisted of 237 adult patients who underwent total
thyroidectomy and presented with benign lesions based on post-
operative histopathology from January 2009 to December 2014 at the
V. Luna General Hospital, a tertiary military hospital. Operations were
performed by senior third year or fourth year residents.
Patients who underwent only lobectomy with isthmusectomy or
underwent reoperation/completion thyroidectomy were excluded
from the study. Patients who presented with prior vocal fold paralysis,
intrathoracic goiters, or with suspicious/confirmed malignancies based
on post-operative histopathology were also excluded. Furthermore,
cases wherein the RLN had to be sacrificed due to gross involvement of
the nerve by malignancy were excluded. Preoperative evaluation of the
patients included thyroid ultrasound, free T4 and thyroid stimulating
hormone determination, serum calcium concentration, fine-needle
aspiration biopsy and evaluation of vocal fold mobility by flexible or
rigid laryngoscopy.
Patients were divided into two groups based on a review of operative
techniques in their records. Patients in Group A were those wherein the
surgeon indicated that he/she identified and preserved the RLN during
the procedure whereas patients in Group B were those where the
surgeon did not indicate that he/she identified or preserved the RLN.
Intraoperative dimensions of the thyroid tumors were also recorded.
Records of flexible nasopharyngolaryngoscopy or rigid
laryngoendoscopy performed by resident physicians of the
Department of ORL -HNS on patients who manifested with hoarseness
post-operatively were reviewed. Vocal fold paralysis was defined as
having decreased or absent vocal fold mobility upon assessment.
(Figure 1) Patients thus assessed were then followed-up regularly at
three-month intervals for the first post-operative year. Permanent
vocal fold paralysis was diagnosed when vocal fold mobility did not
return 6 months after surgery.
Figure 1. Still Photo of the Glottis and Supraglottis of a Patient with Paralysis of Right Recurrent
Laryngeal Nerve following Total Thyroidectomy
PhiliPPine Journal of otolaryngology-head and neck Surgery Vol. 31 no. 1 January – June 2016
24 PhiliPPine Journal of otolaryngology-head and neck Surgery
ORIGINAL ARTICLES
Age, sex, tumor size, temporary and permanent post-operative
vocal cord paralysis were tabulated using Microsoft Office Excel 2007
(Microsoft Corp., Washington, USA). IBM SPSS 23 (International Business
Machines Corp.) was used for the independent T-test and binary logistic
regression analysis.
The prevalence of temporary and recurrent vocal fold paralysis
were expressed as percentages of the total number of cases per group.
Independent T-test was used to determine if there was a significant
difference in tumor size between both groups. Binary logistic regression
analysis was used to evaluate the relationship between intraoperative
RLN identification and RLN preservation.
RESULTS
A total of 237 patients with an age range of 20 to 65 years old
(median age 41 years old) were included. There were more females
than males (163:74). There were 109 patients in Group A, wherein 3
demonstrated temporary RLN injury with an incidence of 2.75%. The
RLN injuries in all these 3 patients were unilateral. Furthermore, the
average tumor size in these patients taken as the widest diameter was
at 5.6 ± 0.93 cm. In comparison, there were 128 patients in Group
B wherein 22 patients presented with temporary RLN injury and an
incidence 17.19%. ( Table 1) Of these patients, 3 had bilateral RLN
injury. Average tumor size in this group was 5.3 ± 0.78 cm. There was
no significant difference in tumor size between the two groups based
on independent T-Test at 95% confidence interval (p = 1.96).
Group A over Group B was found to be e-2.158925 = 0.1154. Obtaining
its reciprocal leads to 8.67, meaning that the probability of having
permanent paralysis increases by almost nine-fold if not identified.
DISCUSSION
This study found that intraoperative RLN identification has a lower
risk for temporary and permanent vocal cord paralysis compared to
non-identification of the RLN. The importance of preservation of the
RLN cannot be overemphasized. In agreement with Pradeep et al., our
findings suggest that the key to achieving preservation is to trace the
entire course of the nerve along the tracheoesophageal groove up to
its entry into the larynx.9
In this study, confounding factors which may cause or contribute
to vocal cord paralysis such as malignancy, reoperation, completion
thyroidectomy, were taken out of the equation based on inclusion and
exclusion criteria. Tumor size, which is another confounding factor, was
not statistically significant, with similar tumor sizes in both groups.
However, since this was a retrospective cohort study, it was not
able to control for the uniformity of the entire operative technique as
well as the skill of the surgeon. Since the study was done at a training
institution, the experience of senior residents is limited to the number
of cases to which they are exposed. Post-hoc analysis revealed that third
year surgeons accounted for 67% of temporary paralysis in group A
while a fourth year surgeon was responsible for the remaining case. In
group B, third year surgeons accounted for 45% of temporary paralysis
compared to the 55% of cases handled by fourth year surgeons. The
lone case of permanent paralysis in group A was performed by a fourth
year surgeon. In group B, 75% of the cases of permanent paralysis were
handled by third year surgeons, compared to the 25% which were
handled by fourth year surgeons. This may suggest that experience
does play a role in cases when the recurrent nerve was not routinely
identified.
The results of this study showed less temporary and permanent vocal
cord paralysis in patients where intraoperative RLN identification was
performed. Moreover, statistical analysis using binary linear regression
confirms that intraoperative RLN identification serves as a protective
factor against temporary and permanent RLN injury following thyroid
surgery as evidenced by the increased probability of RLN injury if the
nerve was not identified during surgery.
The prevalence of temporary and permanent vocal paralysis for
group A at 2.75% and 0.92%, respectively are slightly higher when
compared to the finding of Canbaz et al. and Veyseller et al. who
reported no paralysis for the group where the RLN was preserved and
identified.9, 10
Table 1. Incidence of Temporary and Permanent RLN Paralysis
Group A Group B
Number of Patients
Patients with Temporary Paralysis
Incidence of Temporary Paralysis
Patients with Permanent Paralysis
Incidence of Permanent Paralysis
Bilateral RLN injury
109
3
2.75%
1
0.92%
0
128
22
17.19%
16
12.50%
3
Through binary linear regression, the odds of having temporary
paralysis in Group A over Group B was found to be e-0.6819142 = 0.5056. Its
reciprocal 1.98 means that the probability of having temporary paralysis
increases by almost two-fold if the nerve is not identified.
There was only one patient with permanent RLN injury in Group A,
with an incidence of 0.92%. In contrast, there were 16 patients in Group
B who had permanent RLN injury, and an incidence of 12.5%. Of these,
2 had bilateral RLN injury. The odds of having permanent paralysis for
PhiliPPine Journal of otolaryngology-head and neck Surgery Vol. 31 no. 1 January – June 2016
ORIGINAL ARTICLES
PhiliPPine Journal of otolaryngology-head and neck Surgery 25
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14. Zambudio AR, Rodriguez J, Riquelme J, Soria T, Canteras M, Parrilla P. Prospective study of
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Likewise, the rates of temporary and permanent vocal cord paralysis
in group B at 17.19% and 12.15%, respectively, are higher than those of
the two aforementioned studies (0%, 7.9%) and (1%, 1.5%). The higher
incidences of temporary and permanent RLN injury in this study may
be attributed to the fact that the surgeons in group A only followed the
main trunk of the RLN up to its entry into the larynx while the surgeons
in group B did not identify the RLN as compared to the previous
studies where the RLN and its branches were meticulously followed
up to its entry to the larynx.9,10 Injury to the RLN can be brought about
by inadvertent transection of a bifurcation of the nerve prior to its
entry into the larynx, this bifurcation being present 34% - 70% of the
time.11,12
A considerable number of surgeons do not perform
routine intraoperative RLN identification since it is said to cause
hypoparathyroidism, mainly through devascularization of the parathyroid
glands.13 However, among experienced surgeons who routinely identify
the RLN, temporary and permanent hypoparathyroidism was not high,
with incidences of 9.6% and 0.7%, respectively.14
It can be concluded from this study that intraoperative RLN
identification has a lower risk for temporary and permanent vocal
cord paralysis when compared to non-identification of the RLN. The
probability of having temporary paralysis increases almost two-fold if
the nerve is not identified, and the probability of having permanent
paralysis increases by almost nine-fold if the nerve is not identified.
While future studies may assess RLN injury and other complications
of thyroidectomy by comparing surgeons who routinely perform
intraoperative RLN identification and others who do not, we recommend
routine identification of the RLN.