Nonvasculitic autoimmune inflammatory meningoencephalitis

Caselli and colleagues described five cases with encephalopathy, progressive cognitive decline, ataxia, abnormal CSF studies and steroid responsiveness, and proposed the term non-vasculitic autoimmune inflammatory meningoencephalitis (NAIM). Many of these cases had brain biopsy showing mild leptomeningeal perivascular lymphocytic inflammation, however, none of the cases had a post-mortem. Nonvasculitic autoimmune mediated meningoencephalitis has been described in patients with Sjogren's syndrome, systemic lupus erythematosus and, more recently, with Hashimoto's disease. The present study is the first post-mortem report of a case with a clinical diagnosis of NAIM. Neuropathological examination revealed a panencephalitis with intact vessel walls. T and B immunostaining showed a mixture of T and B cells. The findings were not consistent with other reported findings in collagen vascular diseases including Sjogren's syndrome, CNS vasculitis or Hashimoto's encephalopathy. There was no evidence of neoplasia, bacteria, acid-fast bacilli, fungi or atypical infectious agents. This is the first post-mortem report of a case with a clinical diagnosis of NAIM and demonstrates a panencephalitis without evidence of a vasculitis. The pathology seems unique, however, Sjogren and Hashimoto's encephalopathy might be variants of NAIM.