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Disturbances of memory, behavior, cognition, and seizures can result from immune-mediated encephalitides. These disorders can be paraneoplastic or not and may associate with several antibodies.1 Recently, a treatment-responsive paraneoplastic encephalitis that associates with antibodies to NR1/NR2 heteromers of the NMDA receptor (NMDAR) was reported.2 Patients were young women with teratomas, usually of the ovary, who presented with prominent psychiatric symptoms, and less frequently with features of limbic encephalitis. We report a man with treatment-responsive limbic encephalitis and antibodies to NR1/NR2 heteromers. ### Case report. For 3 months this 53-year-old man had progressive short-term memory deficits and disorientation that forced him to leave his job. During the month before hospital admission he had multiple episodes compatible with partial complex seizures. He had no past medical history of interest. The neurologic examination only revealed short-term memory deficits and impairment of temporal orientation. Blood cell count, general chemistry, B12, folic acid, thyroid function test, thyroglobulin antibodies, RPR, Lyme serology, antibodies to double stranded DNA, and SSA/Ro and SSB/La were unrevealing. CSF analysis showed 5 WBC/μL (100% lymphocytes) and normal glucose and protein concentration. Serum and CSF disclosed the same oligoclonal IgG bands. Paraneoplastic antineuronal and VGKC antibodies were negative. EEG demonstrated bilateral temporal lobe epileptic activity. MRI of the brain revealed noncontrast enhancing T2 and FLAIR hyperintensities involving the medial aspect of the temporal lobes and nonspecific hyperintensities in the frontal lobes (figure, A). Ultrasound of the testis, CT of the chest, abdomen and …

To report the presence of microscopic neoplasms of the testis in men with anti-Ma2-associated encephalitis (Ma2-encephalitis) and to discuss the clinical implications.Orchiectomy specimens were examined using immunohistochemistry with Ma2 and Oct4 antibodies.Among 25 patients with Ma2-encephalitis younger than 50 years, 19 had germ-cell tumors, and 6 had no evidence of cancer. These 6 patients underwent orchiectomy because they fulfilled five criteria: 1) demonstration of anti-Ma2 antibodies in association with MRI or clinical features compatible with Ma2-encephalitis, 2) life-threatening or progressive neurologic deficits, 3) age50 years, 4) absence of other tumors, and 5) new testicular enlargement or risk factors for germ-cell tumors, mainly cryptorchidism or ultrasound evidence of testicular microcalcifications. All orchiectomy specimens showed intratubular-germ cell neoplasms unclassified type (IGCNU) and other abnormalities including microcalcifications, atrophy, fibrosis, inflammatory infiltrates, or hypospermatogenesis. Ma2 was expressed by neoplastic cells in three of three patients examined. Even though most patients had severe neurologic deficits at the time of orchiectomy (median progression of symptoms, 10 months), 4 had partial improvement and prolonged stabilization (8 to 84 months, median 22.5 months) and two did not improve after the procedure.In young men with Ma2-encephalitis, 1) the disorder should be attributed to a germ-cell neoplasm of the testis unless another Ma2-expressing tumor is found, 2) negative tumor markers, ultrasound, body CT, or PET do not exclude an intratubular germ-cell neoplasm of the testis, and 3) if no tumor is found, the presence of the five indicated criteria should prompt consideration of orchiectomy.