Anti-Ma2 Paraneoplastic Syndrome

Anti-Ma2 paraneoplastic syndrome (also known as anti-Ta) is a classic paraneoplastic neurologic disorder caused by antibodies against Ma2 protein expressed in neurons and tumor tissue. The clinical-radiological-immunological constellation is characteristic: young to middle-aged men, hypothalamic-diencephalic and upper brainstem involvement, and high association (>90%) with testicular germ cell tumors.

Clinical phenotype features limbic encephalitis (memory loss, behavioral change, seizures), hypothalamic-diencephalic syndrome (excessive daytime sleepiness, narcolepsy-cataplexy, hyperphagia, hypothermia, central diabetes insipidus, hypothalamic-pituitary endocrinopathy), and brainstem encephalitis with vertical gaze palsy, oscillopsia, internuclear ophthalmoplegia, and bulbar dysfunction. Cerebellar ataxia and atypical parkinsonism may occur.

Diagnostic workup includes anti-Ma2 antibody detection in serum and CSF, brain MRI showing T2-FLAIR hyperintensity in mesial temporal lobes, hypothalamus, midbrain, and pons, comprehensive testicular ultrasound and PET-CT for occult tumor, and orchiectomy if abnormal even with normal imaging (occult intratubular germ cell neoplasia). Combined oncologic resection and immunotherapy (corticosteroids, IVIG, rituximab, cyclophosphamide) is preferred over immunotherapy alone, as tumor removal is critical for stabilization. Outcomes are better than other paraneoplastic disorders with early diagnosis and orchiectomy, but residual deficits common.