Cytotoxic CD8(+) T cells and CD138(+) plasma cells prevail in cerebrospinal fluid in non-paraneoplastic cerebellar ataxia with contactin-associated protein-2 antibodies

OBJECTIVE: The purpose of this paper is to report a patient with otherwise unexplained cerebellar ataxia with serum antibodies against contactin-associated protein-2 (CASPR-2) and provide a detailed description of the composition of cellular infiltrates in the cerebrospinal fluid (CSF) compared to the peripheral blood (PB). CASPR-2 antibodies strongly labeling axons of cerebellar granule neurons have recently been identified in sera from nine patients with otherwise unexplained progressive cerebellar ataxia with mild to severe cerebellar atrophy. DESIGN: This is a report of a single case. METHODS: The study methods used were neurologic examination, magnetic resonance imaging, fluorodeoxyglucose positron emisson tomography, lumbar puncture and multicolor flow-cytometry. RESULTS: A 23-year-old Caucasian male presented with a two-year history of a progressive cerebellar and brainstem syndrome. Magnetic resonance imaging (MRI) showed pronounced cerebellar atrophy, especially of the medial parts of the hemispheres and the vermis. Cerebral fluorodeoxyglucose positron emission tomography (FDG-PET) showed pronounced hypometabolism of the whole cerebellum. CASPR-2 antibodies were detected in the serum but not the CSF, and none of the staging and laboratory assessments revealed other causes of progressive cerebellar degeneration. Interestingly, flow-cytometry of the CSF as compared to the PB showed increased fractions of CD138(+) plasma cells as well as human leukocyte antigen (HLA)-DR(+) CD8(+) T cells suggesting that both B cells and CD8(+) T cells were preferentially recruited to and activated within the CSF- (and putatively central nervous system (CNS)-) compartment. CONCLUSION: We confirm the association of CASPR-2 serum antibodies with cerebellar ataxia and provide the first evidence for a combined humoral and cellular immune response in this novel antibody-associated inflammatory CNS disease.