Episodic ataxia in CASPR2 autoimmunity.

A 64-year-old man developed cognitive dysfunction and generalized seizures, followed by episodes of transient speech and gait disturbances lasting several minutes, occurring multiple times per day; the events were not associated with any triggers. Neurologic examination during one of his episodic symptoms (video 1) showed transient ataxic dysarthria. Testing for neural autoantibodies revealed evidence of voltage-gated potassium channel complex antibodies by radioimmunoprecipitation assay; CASPR2-IgG was positive in serum and CSF by cell-based assay. Brain MRI was normal; CSF analysis showed an elevated protein level at 101 mg/dL, but it was otherwise normal. Oncologic evaluation was negative. The cognitive symptoms improved; seizures and episodic ataxia resolved after 12 weeks of treatment with IV methylprednisolone. Episodic ataxia is a manifestation of CASPR2 autoimmunity;[1] patients can have normal MRI, and immunotherapy is beneficial.

Neurologic examination of the patient showing transient ataxic dysarthria.Download Supplementary Video 1 via http://dx.doi.org/10.1212/000536_Video_1