Anti-CASPR2 Antibody-Associated Syndrome Presenting With Episodic Ataxia

The anti-CASPR2 antibody-associated syndrome is a rare immune-mediated disorder. Most case reports describe neurologic symptoms that include encephalic signs, peripheral nerve hyperexcitability, dysautonomia, or neuropathic pain. We report the case of a 70-year-old man, admitted to the emergency department with complaints of slurred speech and imbalance. Neurological examination was relevant for dysarthria, hyperreflexia, and pancerebellar syndrome. Cranial CT and basic laboratory tests were normal and he spontaneously recovered after 14 hours. Over the next four months, the patient experienced three similar episodes in relation to stressful events (emotional and organic disturbances like prolonged fasting and vaccination). A contrast-enhanced MRI was performed, along with extensive laboratory testing, analysis of cerebrospinal fluid (CSF), paraneoplastic investigation, and next-generation sequencing panel for episodic ataxias. The results revealed oligoclonal bands in the CSF and positive anti-CASPR2 antibodies both in serum and CSF. Three-day-IV- methylprednisolone pulse followed by plasmapheresis and monthly intravenous immunoglobulins was performed with good response. In conclusion, the neurological manifestations that led to the diagnosis of anti-CASPR2 antibody-associated syndrome were intermittent self-limiting episodes of ataxia, often triggered by concurrent stress-inducing factors. This case supports the aim of other authors to add paroxysmal cerebellar ataxia to the spectrum of the anti-CASPR2 antibody syndrome.