Peribuccal and pharyngeal myorhythmia as a presenting symptom of hypertrophic olivary degeneration

Abstract

A 58-year-old woman underwent to a successful surgical treatment of a left cerebellar paravermian cavernous malformation. Seven months later she progressively developed involuntary contractions of the left peribuccal region. Neurological examination revealed repetitive, rhythmic, slow frequency jerks of the left corner of the mouth (Video, segment-1). She did not report swallowing difficulties, saliva pooling or ear clicks. However, a careful examination of the oral cavity revealed the presence of synchronous contractions of left pharyngeal muscles (Video, segment-2). The involuntary movements occurred at rest and were suppressed neither by voluntary activity nor by distractions manoeuvres with motor tasks, disappearing during sleep. No palatal or ocular movement abnormalities were observed. Surface electromyography recorded to the left orbicularis oris at rest showed repetitive synchronous 3-Hz rhythmic bursts with a mean duration of 130 msec (Fig. 1D and E), without any electroencephalographic correlation. 3T-brain MRI revealed FLAIR hyperintensity and hypertrophy of right inferior olivary nucleus (ION) consistent with hypertrophic olivary degeneration (HOD), associated with T2-hyperintensity and thinning of left superior cerebellar peduncle (Fig. 1A and B). DTI-based fiber direction failed in demonstrating the normal appearance of decussation of superior cerebellar peduncles, probably as a result of axonal degeneration processes of dentatorubral tract (Fig. 1, C). A diagnosis of isolated peribuccal and pharyngeal myorhythmia due to HOD was made. Clonazepam and pregabalin did not entail any benefit. Botulinum toxin type A injections was started and repeated every three months with 8 Xeomin® units injected into the left orbicularis oris and depressor anguli oris muscles, leading to persistent reduction of involuntary peribuccal contractions. To date, 24 months after surgery patient's conditions are stable with no palatal involvement.