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JAMA Neurol. 2015 Jan;72(1):66-72. doi: 10.1001/jamaneurol.2014.2376.

Encephalitis of unclear origin diagnosed by brain biopsy: a diagnostic challenge.

Author information

1
Multiple Sclerosis and Neuroinflammation Center, Department of Neurology, University of California, San Francisco.
2
Department of Pathology, University of California, San Francisco.

Abstract

IMPORTANCE:

Brain biopsy specimens that exhibit encephalitis without specific histopathologic features pose a diagnostic challenge to neuropathologists and neurologists. Such cases are generally referred to pathologically as encephalitis, not otherwise specified (ENOS). A systematic approach to diagnostic evaluation in such patients is challenging, and currently there is no generally accepted algorithm.

OBJECTIVE:

To examine ultimate diagnostic outcomes in patients with ENOS diagnosed by brain biopsy.

DESIGN, SETTING, AND PARTICIPANTS:

This retrospective case series at the University of California, San Francisco, Medical Center, a tertiary care urban neurosciences center, studied patients with encephalitis diagnosed by brain biopsy from January 1, 1983, through December 31, 2011.

EXPOSURES:

Brain biopsy.

MAIN OUTCOMES AND MEASURES:

Clinical and neuropathologic diagnosis.

RESULTS:

Among 58 patients who met the inclusion criteria for the study, the original pathologic diagnosis was ENOS in 49 patients (84%). The median age was 40 years (interquartile range, 27-53 years), 35 patients were male, and 13 had known human immunodeficiency virus or AIDS. Median time from onset of symptoms to brain biopsy was 66 days (interquartile range, 18-135 days). For the 29 patients in whom material for pathologic analysis was still available, additional neuropathologic review led to a more specific categorization in 10 (34%). Clinical detail and follow-up information was available for 42 patients, and a specific diagnosis was reached with the help of ancillary testing and/or clinical follow-up in 12 patients. Despite a comprehensive neuropathologic review with additional studies and information, 27 patients still had to be classified in the ENOS category at the end of the study.

CONCLUSIONS AND RELEVANCE:

ENOS is the most common initial type of encephalitis diagnosed by brain biopsy. In such patients, it may be worth having the biopsy materials reviewed again in a comprehensive fashion by a neuropathologist because additional review led to a more specific categorization in one-third of our cases. Ancillary testing, clinical correlation, and clinical follow-up establish more specific diagnoses in some patients. ENOS still remains a diagnostic challenge after all these efforts in many cases. Current algorithms are of limited value. More advanced methods and better diagnostic algorithms are needed to characterize these patients.

PMID:
25365755
DOI:
10.1001/jamaneurol.2014.2376
[Indexed for MEDLINE]
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