Posttraumatic Oculopalatal Myoclonus

Oculopalatal myoclonus (OPM) is defined clinically by continuous rhythmic movements of the soft palate with synchronous pendular nystagmus. Because it is rare and typically results from brainstem infarction or hemorrhage, OPM has not been well-characterized as a sequela of trauma. We describe four patients with delayed-onset OPM following closed head injury. All experienced (1) prolonged coma (range from two to six weeks); (2) severe cerebellar ataxia; and (3) multiple brainstem deficits, including dysarthria, dysphagia, diplopia, and partial airway obstruction. OPM developed gradually in each patient; the average time of diagnosis was 3.3 years (range one to five years) following the initial injury. In three patients, magnetic resonance imaging revealed increased T2 signal intensity in the inferior olives. In two patients, disabling oscillopsia or dysphonia responded to treatment with valproic acid. We conclude that OPM is a disabling and treatable sequela of severe head injury, and postulate that brainstem axonal shearing injury may play an important role in the pathogenesis of this disorder.