1374 Unusual Oscillations: A Case of Secondary Palato-Pharyngo-Laryngeal Myoclonus Seen on Polysomnography

Abstract Introduction Palato-pharyngo-laryngeal myoclonus is a rare variant of palatal myoclonus characterized by involuntary, rhythmic contractions of the muscles of the soft palate, pharynx, and larynx. Symptoms include dysarthria, dysphonia, dysphagia, tinnitus, inappropriate vocal cord closure, or laryngospasm. Symptomatic palatal myoclonus cases are associated with brainstem lesions affecting the dentato-rubro-olivary tract (Guillain-Mollaret triangle). This results in hypertrophic olivary degeneration and disinhibition of the inferior olivary nucleus resulting in abnormal synchronized oscillations that propagate through the cerebellum to produce abnormal rhythmic motor output. Report of case(s) A 64-year-old man with left cerebellar ischemic stroke complicated by pseudo-meningocele requiring ventriculoperitoneal shunt presented to sleep clinic with snoring and witnessed apneas. His neurologic deficits included left-sided ataxia, dysarthria, dysphonia, and dysphagia. Weeks to months after his stroke, he also developed an irregular breathing pattern and facial twitching. Respiratory symptoms were persistent throughout the day, limiting participation in rehabilitation, and notably worse at night. A split-night polysomnography (PSG) revealed severe central sleep apnea with an Apnea-Hypopnea Index (AHI) of 91.1/hr, with Cheyne Stokes respirations. During the titration portion of the study, a continuous, oscillating airflow signal of approximately 2 Hz frequency that was locked to rapid phasic bursts (lasting 150-200 ms) in the chin electromyogram (EMG) signal was visualized. Flexible laryngoscopy demonstrated visible bilateral (left-predominant) myoclonus of the soft palate, pharynx, and vocal folds confirming diagnosis of palato-pharyngo-laryngeal myoclonus. He underwent EMG guided botulinum toxin injection to left thyroarytenoid, left palatopharyngeal and palatal muscles with limited relief of symptoms. Pharmacologic therapies including levetiracetam, baclofen, and zonisamide provided minimal improvement. Regarding central sleep apnea, titration using CPAP, BIPAP, and BiPAP with respiratory rate were unsuccessful at controlling respiratory events. Subsequent Adaptive Servo-Ventilation titration demonstrated excellent control of respiratory events (residual AHI 2.5) and resulted in significant subjective benefits in sleep quality during follow up despite issues with mask leak and elevated residual AHI. Conclusion This case highlights the rare diagnosis of Symptomatic Palato-pharyngo-laryngeal myoclonus after stroke and the importance of monitoring for abnormal waveforms on PSG, as this could alert study interpreters to consider this condition. Support (if any)