Transcranial Magnetic Stimulation in Assessment of Vocal Cord Paralysis Due to post Viral (COVID‐19) Vagal Neuropathy

Coronavirus disease (COVID‐19), caused by SARS‐CoV‐2, may be asymptomatic or could cause mild to severe symptoms affecting the respiratory system. Many individuals suffering from COVID‐19 have reported persistent symptoms and/or complications lasting beyond 4–12 and >12 weeks, now called ongoing symptomatic COVID‐19, long COVID‐19, or post‐COVID‐19 syndrome. It is known that approximately 22%–27% of patients present with laryngeal‐related symptoms, including dysphonia or aphonia, hoarseness, voice fatigue, vocal fold paralysis, and paresis. Further, vocal cord paralysis, caused by postviral vagal neuropathy resulting in dysfunctional vocal cord mobility, has been confirmed by laryngeal electromyography (EMG) in patients with no history of intubation recovering from COVID‐19. It is well known that the primary motor cortex for laryngeal motor representation (M1) plays an important role in human voice and speech production. Also, the MEPs response represents the pathway of spatial and temporal summation of several descending volleys activating the α‐motoneurons, thus reliably reflecting the excitation state of the M1, cortico‐bulbar cells for the vagal nerve, the corticobulbar tract, the peripheral recurrent laryngeal nerve, and the target laryngeal muscle. Here, the paper presents a case of a 39‐year‐old female who has recovered from COVID‐19 twice, in whom paralysis of the left vocal cord occurred after the second COVID‐19. Acoustic voice analysis showed pathological voice findings for jitter (1.15%), shimmer (1.182 dB), and noise‐to‐harmonic ratio (NHR) (8 dB). Eleven months after the first examination, laryngoscopy, and stroboscopic examination showed symmetric and consistent vocal cords mobility with complete adduction during phonation. In addition, the voice analysis measures were typical for jitter, shimmer, and NHR. E‐field navigated TMS was used as a nonstandard neurophysiologic technique to evaluate the excitability of the corticobulbar tract by recording the MEP from thyroarytenoid (TA) muscle and estimating the MEP peak‐top‐peak amplitude. Results show that navigated TMS may well be suited in laryngological research and clinical settings for evaluating COVID‐19‐related symptoms.