Nonvasculitic autoimmune inflammatory meningoencephalitis as a cause of potentially reversible dementia: report of 4 cases.

The aim of this study is to evaluate the presentation of unusual dementias in 4 patients and correlate these presentations with the histopathological findings after brain biopsy sampling to define a diagnostic entity. The authors detail the cases of 4 patients (2 women, 46 and 56 years of age; and 2 men, 67 and 74 years of age) who presented with acute and subsequently subacute encephalopathies. Their bizarre presenting symptom complexes and the results of neurological examinations, radiographic studies, electroencephalography (EEG) recordings, and serological marker tests are reviewed. The diagnostic surgical procedures and successful treatments in these patients are discussed. All 4 patients underwent craniotomy and excisional brain biopsy sampling as part of a comprehensive evaluation. Histopathological confirmation of nonvasculitic autoimmune inflammatory meningoencephalitis (NAIM) by a neuropathologist was present in all 4 patients. All patients were successfully treated with a course of corticosteroid medication. Nonvasculitic autoimmune inflammatory meningoencephalitis is a potentially treatable form of dementia whose salient features include a younger average age at onset, rapid progression with significant cognitive and behavioral features, absence of family history, abnormal EEG findings, and elevated levels of inflammatory markers. Although it is an invasive procedure, brain biopsy sampling is safe and can offer histological confirmation of this condition. This procedure is important because NAIM can be treated successfully if it is distinguished from the nontreatable dementias that mimic it.