Cervical Dystonia Following Injury to the Cerebellar Pontine Angle: An Instructive Case

A 38-year-old woman presented with cervical dystonia in the context of a recent surgery to remove a vestibular schwannoma. She initially presented to neurology with pain in the right arm, and MRI of the brain showed an incidental right-sided vestibular schwannoma (Video 1, Segment 1). An elective gamma-knife procedure was performed, which failed. Hydrocephalus requiring ventriculoperitoneal shunt insertion developed, and 3 years following the initial procedure the lesion was surgically excised. Surgery was further complicated by right middle cerebellar peduncle injury, extending to the cerebellopontine angle and marginally to the right pontine tegmentum, with subsequent mass effect on cerebellum displayed on follow-up MRI (Video 1, Segment 2). Six months later, the patient experienced forced head deviation to the right, with difficulty moving from this position. Examination revealed clear right-sided torticollis, with hypertrophy of the left sternocleidomastoid muscle. Cervical dystonia worsened with action and nearly resolved with the patient lying down. A clear geste antagoniste, where symptoms improved with the patient touching the side of her head, was present (Video 1, Segment 3). Findings consistent with injury to the cerebellar pathways were additionally exhibited. She demonstrated clear dysarthria, bilateral dysmetria, dysdiadochokinesia (worse on the right), and prominent gait ataxia (Video 1, Segment 4). Although a possible role of the schwannoma itself in the cervical dystonia pathogenesis cannot be entirely ruled out, the timing of signs, occurring soon after the postsurgical injury, suggest a prominent involvement of structures lying within the cerebellar pontine angle.