Palatal myoclonus, also known as palatal tremor, is a focal myoclonic syndrome characterized by rhythmic, unilateral or bilateral, palatal contractions which continue during sleep. This may be asymptomatic, or there may be a clicking sound in the inner ear (especially in essential palatal myoclonus). There may be associated contractions of external ocular muscles (oculopalatal myoclonus), larynx, neck, diaphragm (respiratory myoclonus, diaphragmatic flutter, or Leeuwenhoek’s disease), trunk, and limbs, which may bring the palatal myoclonus to attention. Palatal myoclonus may be accompanied by pendular nystagmus and oscillopsia.
Palatal myoclonus is associated with lesions interrupting pathways between the red nucleus, inferior olivary nucleus and dentate nucleus (Guillain-Mollaret triangle). Hypertrophy of the inferior olivary nucleus may be evident neuroradiologically (structural or functional imaging) and pathologically. This is a consequence of a lesion in the dentato-olivary pathway which leads to transsynaptic degeneration and hypermetabolism of the olivary nucleus. Although many cases are essential/idiopathic, recognized symptomatic causes of palatal myoclonus include vascular lesions, trauma, neoplasia, demyelination, epilepsy and, rarely, adult-onset Alexander’s disease.
Drug treatment of palatal myoclonus is often unsuccessful, although reports of benefit with 5-hydroxytryptophan, carbamazepine, sodium valproate, clonazepam, baclofen, and even sumatriptan have appeared. Botulinum toxin injections may also help.