Paraneoplastic neurological syndromes (PNS) are rare complications of cancer occurring in 0.01% of cases. Their clinical, biological and radiological presentation is heterogeneous and may constitute a diagnostic challenge. Anti-Ma2 PNS are rare diseases with a guarded prognosis. They are most often associated with a seminoma-like testicular tumor but can also be associated with lung cancer. Classically, they present as limbic, diencephalic and/or brainstem encephalitis. Anti-Ma2 antibodies target intracellular receptors and are characteristic of a particular form of encephalitis. Atypical manifestations including narcolepsy-cataplexy, weight gain, sexual dysfunction and motor neuron syndrome have been described and explain the difficulty in diagnosing anti-Ma2 associated PNS. It seems interesting to better characterize the phenotypes of Ma2 patients in order to optimize the diagnosis and follow-up.

Inclusion Criteria:

• Neurological disorder
• Anti-Ma2 positivity in sera or CSF
• Patient > 18 years old

Exclusion Criteria:

• Patient without clinical data
• Patient without Ma2 antibody in sera or CSF

Patients with anti-Ma2 paraneoplastic neurological syndromes with or without cancer