Aim:
Damage to the superior laryngeal nerve (SLN) is more difficult to diagnose clinically
than a recurrent laryngeal nerve (RLN) lesion. But in many routine laryngeal EMG (LEMG)
examinations this nerve is not regularly tested. According to the guides lines for
LEMG of the European Laryngological Society we measure all relevant intrinsic laryngeal
muscles to evaluate a vocal fold paralysis. In this study we looked at the SLN involvement
in vocal fold paralysis patients who attended our neurolaryngology clinic.
Method:
LEMG results of 339 patients who attended our neurolaryngology clinic between 2008
and 2016 were evaluated. Results were stratified into iatrogenic and non-iatrogenic
lesions, and further according to the kind of surgery that led to the paralysis. Cancer
related cases were excluded.
Results:
There were a total of 179 paretic vocal folds with ipsilateral EMG of thyroarytenoid
muscle (RLN) and cricothyroid muscles (SLN) EMG that could be evaluated. Patients
with vocal fold paralysis after thyroid surgery and surgery of the carotid artery
showed a relevant ipsilateral SLN involvement in 50% of cases. In cervical spine surgery
it was 36.4%. In 43.5% of non-iatrogenic cases we saw an isolated RLN damage, while
56.5% had a lesion of the vagal stem (SLN + RLN).
Conclusions:
There was an unexpectedly high share of SLN involvement in iatrogenic paralysis. Therefore
we recommend the routine measurement of the cricothyroid muscle during an LEMG examination.
Not all idiopathic or viral vocal fold paralysis cases were due to vagal stem lesions
but could be limited to the RLN portion.
