title: Use of clinical and neuroimaging characteristics to distinguish temporal lobe herpes simplex encephalitis from its mimics.
abstract: BACKGROUND
  We describe the spectrum of etiologies associated with temporal lobe (TL) encephalitis and identify clinical and radiologic features that distinguish herpes simplex encephalitis (HSE) from its mimics.
  
  
  METHODS
  We reviewed all adult cases of encephalitis with TL abnormalities on magnetic resonance imaging (MRI) from the California Encephalitis Project. We evaluated the association between specific clinical and MRI characteristics and HSE compared with other causes of TL encephalitis and used multivariate logistic modeling to identify radiologic predictors of HSE.
  
  
  RESULTS
  Of 251 cases of TL encephalitis, 43% had an infectious etiology compared with 16% with a noninfectious etiology. Of infectious etiologies, herpes simplex virus was the most commonly identified agent (n = 60), followed by tuberculosis (n = 8) and varicella zoster virus (n = 7). Of noninfectious etiologies, more than half (n = 21) were due to autoimmune disease. Patients with HSE were older (56.8 vs 50.2 years; P = .012), more likely to be white (53% vs 35%; P = .013), more likely to present acutely (88% vs 64%; P = .001) and with a fever (80% vs 49%; P < .001), and less likely to present with a rash (2% vs 15%; P = .010). In a multivariate model, bilateral TL involvement (odds ratio [OR], 0.38; 95% confidence interval [CI], .18-.79; P = .010) and lesions outside the TL, insula, or cingulate (OR, 0.37; 95% CI, .18-.74; P = .005) were associated with lower odds of HSE.
  
  
  CONCLUSIONS
  In addition to HSE, other infectious and noninfectious etiologies should be considered in the differential diagnosis for TL encephalitis, depending on the presentation. Specific clinical and imaging features may aid in distinguishing HSE from non-HSE causes of TL encephalitis.
authors: Department of Neurology.
authors: Felicia C
authors: FC
authors: Chow
authors: Department of Pediatrics, University of California, San Francisco Department of Kaiser Permanente, Oakland, California.
authors: Carol A
authors: CA
authors: Glaser
authors: Department of Communicable Disease Emergency Response Branch.
authors: Heather
authors: H
authors: Sheriff
authors: Department of Viral and Rickettsial Disease Laboratory, California Department of Public Health, Richmond.
authors: Dongxiang
authors: D
authors: Xia
authors: Department of Viral and Rickettsial Disease Laboratory, California Department of Public Health, Richmond.
authors: Sharon
authors: S
authors: Messenger
authors: Department of Pediatrics, University of Alabama at Birmingham.
authors: Richard
authors: R
authors: Whitley
authors: Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors: Arun
authors: A
authors: Venkatesan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002140:California; D003937:Diagnosis, Differential; D004660:Encephalitis / Q000175:diagnosis / Q000209:etiology* / Q000821:virology; D020803:Encephalitis, Herpes Simplex / Q000175:diagnosis*; D020804:Encephalitis, Varicella Zoster / Q000175:diagnosis; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015999:Multivariate Analysis; D059906:Neuroimaging; D012189:Retrospective Studies; D013702:Temporal Lobe / Q000821:virology; D013997:Time Factors; D014376:Tuberculosis / Q000175:diagnosis
keywords: brain infection; encephalitis; herpes simplex; magnetic resonance imaging; temporal lobe
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