[Limbic encephalitis and SIADH revealing small-cell anaplastic lung cancer: MRI and immunologic findings]

Paraneoplastic limbic encephalitis (PLE) is a manifestation of clinico pathological entity encephalo-myelo-neuropathy associated with anti-neuronal antibodies type 1 (ANNA-1 also called anti-Hu). Isolated PLE is rare. We reported a case of PLE in a 61-year-old heavy smoker man. An inappropriate antidiuretic hormone secretion syndrome was associated. Cranial MRI showed hyperintensity in amygdalo-hippocampic regions on T2 weighted sequences which appeared hypointense on T1-weighted sequences without gadolinium enhancement. Anti-Hu antibodies were absent in serum and in CSF. Despite chemotherapy, he died 18 months after disease onset. Our patient presented PLE without myelonouropathy and without ANNA-1 which suggests a different immunopathology.