Objective: To describe a rare a case of a patient who developed “dancing larynx”-like syndrome after gamma knife radiation for trigeminal neuralgia (TN) associated with a demyelinating pontine lesion.

Background: Multiple sclerosis (MS) has been associated with a variety of movement disorders, including focal myoclonus. We report a case of focal myoclonus giving the appearance of a “dancing larynx” associated with TN secondary to a demyelinating pontine lesion that worsened after gamma knife radiation.

Method: A 44 year-old right-handed male with history of MS presented to the clinic for evaluation of abnormal neck movements. His first MS symptom was left-sided TN, which failed medical treatment and required gamma knife radiation to the nerve root. Following the procedure, he developed anterior neck spasms that impaired talking and eating. He denied throat spasms or ear clicking. Exam was significant for irregular, clonic movements of the left submental region and arrhythmic movements of the larynx up-and-down, cerebellar dysarthria, right hemiparesis, and ataxia. Palatal elevation was normal without tremor. EMG of the bilateral mylohyoid muscles excluded myokymia. MRI brain showed T2 hyperintensities in the left cerebellopontine angle, left inferior midbrain/lateral pons, and extensive T2 lesion burden in the periventricular white matter. The left cerebellopontine angle lesion showed expansion following radiation, and appeared atypical for an MS lesion. The patient received injections of botulinum toxin to the mylohyoid muscles, with resolution of the movements.

Results: MS has been associated with many movement disorders, including palatal myoclonus, classically thought to be secondary to lesions in the dentato-rubro-olivary pathway [1,2]. One case was documented to be secondary to a pontine lesion [3]. Similar movements of the larynx, termed “dancing larynx,” have been described following viral illness in absence of MRI findings [4]. Our patient presented with TN and focal myoclonus of the mylohyoid and anterior belly of the digastric (both innervated by the trigeminal nerve), giving the appearance of a “dancing larynx”-like syndrome. We hypothesize that symptoms worsened after gamma knife radiation, secondary to irritation of the nerve root or pons itself.

Conclusion: MS can present with a variety of movement disorders, including focal myoclonus. Symptoms may respond well to botulinum toxin injections.

References: [1] Tranchant C, Bhatia KP, Marsden CD. Movement disorders in multiple sclerosis. Mov Disord. 1995;10;4:418-423 [2] Mehanna R and Jankovic J. Movement disorders in multiple sclerosis and other demyelinating diseases. J Neruol Sci. 2013;328 (1-2): 1-8. [3] Revol A, Vighetto A, Confavreux C, Trillet M, Aimard G. Oculo-paalatal myoclonus and multiple sclerosis. Rev Neurol (Paris). 1990;146(8-9):518-521. [4] Schrag A, Bhatia KP, Quinn NP, Marsden CD. The dancing larynx- a variant of palatal tremor? Mov Disord. 1999;14;5: 882-883

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dancing-larynx-syndrome-associated-with-trigeminal-neuralgia-secondary-to-multiple-sclerosis/