[1791] The Diagnostic Utility of Brain Biopsy in Patients with Clinical Suspicion of Encephalitis and Non-Enhancing CNS Lesions

Gillian L Genrich, Jeff Gelfand, Ari Green, Bruce Cree, Tarik Tihan. University of California at San Francisco, San Francisco

Background: The clinical manifestations of encephalitis are highly diverse and the differential diagnosis includes numerous infectious and noninfectious processes. Brain biopsy is an invasive diagnostic modality of last resort, in patients for whom CSF analyses and neuroimaging do not yield conclusive diagnoses. The diagnostic utility of biopsies in such cases is not well established. In patients who do undergo biopsy, the diagnosis may be interpreted as encephalitis without specific features. The clinical outcomes in this particular patient cohort are useful in determining the value of an invasive procedure in definitive diagnosis.
Design: We reviewed Department of Pathology archives for all cases submitted with a clinical suspicion of encephalitis from 1989-2010. The search algorithm identified all cases in which “encephalitis” appeared in the clinical differential diagnosis and in the final pathology report. For cases, the clinical symptoms at presentation, histopathologic features and diagnoses on brain biopsy, and follow-up information were gathered from electronic medical records and physician files.
Results: We identified 130 patients (87 males, 43 females; mean age 41 years) with a clinical suspicion and pathological diagnosis of encephalitis. The diagnoses were encephalitis, not otherwise specified (NOS) in 79 cases, specific viral encephalitis in 28 cases, toxoplasma encephalitis in 11 cases, paraneoplastic (limbic) encephalitis in 3 cases, fungal encephalitis in 2 cases, and Rasmussen's encephalitis in 2 cases. Other diagnoses included Balamuthia sp., Pseudalesscheria boydii, larva migrans, tuberculosis and granulomatous encephalitis NOS (1 case each). In the “encephalitis, NOS” group, there were 47 males and 32 females (mean age, 41 years). The "NOS" diagnosis was changed to a specific diagnosis after retrospective histopathologic review in 5 cases. Clinical follow-up revealed a specific diagnosis in 23 cases. The diagnoses could not be further specified in 51 cases.
Conclusions: The initial diagnostic yield of brain biopsies in patients with a suspicion of “encephalitis” and with diffuse radiological abnormalities without enhancement was 39%. Among the biopsies with “encephalitis NOS,” a specific etiology was not determined in 51 cases after follow-up. The overall nonspecific diagnoses (39%) even after follow-up necessitates a more cautious approach to brain biopsy in encephalitis cases, and the use of an algorithm to maximize the diagnostic yield.
Category: Neuropathology

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 278, Tuesday Afternoon


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