Rapidly Progressive Gait and Coordination Difficulties

A 59-year-old woman noted sudden onset of slurred speech. Within a few days, she noted double vision, gait unsteadiness, and incoordination of her limbs. She sought care at her local emergency department. Computed tomography and magnetic resonance imaging of the head were negative for stroke. Her symptoms persisted. Neurologic examination indicated a moderate pancerebellar ataxia, without additional abnormalities. Her pursuit eye movements were saccadic. She had binocular diplopia with horizontal, gaze-evoked nystagmus. She had ataxic dysarthria and dysmetria of all limbs. Her steps and walking were irregular and she could not accomplish tandem gait. Additional neural antibody testing was undertaken, beyond the classic paraneoplastic antibodies. Metabotropic glutamate receptor 1-immunoglobulin G was detected in the serum and cerebrospinal fluid. The patient was diagnosed with autoimmune cerebellar ataxia. Because of the reported association of metabotropic glutamate receptor 1-immunoglobulin G with Hodgkin disease and non-Hodgkin lymphoma, positron emission tomography–computed tomography of the trunk (orbits to thighs) was performed, which was negative. After 6 weeks of intravenous methylprednisolone, the patient returned for evaluation. She had a mild ataxic dysarthria and minimal dysmetria of her left upper extremity only. She could tandem walk almost without error, and her gait appeared normal (no longer broad-based). At that point, immunotherapy was discontinued. At last follow-up, her neurologic examination findings remained stable. The subacute onset and rapid progression of ataxic symptoms in this adult patient led to suspicion for an autoimmune cause.