Limbic encephalitis: a clinical-radiological comparison between herpetic and autoimmune etiologies

Herpetic (HE) and autoimmune (AE) encephalitis share clinical and radiological features. We compared both types of encephalitis with the aim of making a differential clinical-radiological pattern.

All cases with a clinical diagnosis of encephalitis who attended our hospital between 1999 and 2012 were reviewed. We selected those cases with positive polymerase chain reaction for herpes simplex virus 1 (HSV-1) in the cerebrospinal fluid (CSF), and those with antineuronal antibodies or paraneoplastic etiology. We compared epidemiological, clinical, CSF, electroencephalographic and radiological findings.

Twelve patients with positive polymerase chain reaction for HSV-1, and 10 patients with antineuronal antibody or paraneoplastic etiology were found. The only features found exclusively in one group were the presence of psychiatric symptoms and tumors in AE. Acute onset of symptoms, fever and aphasia were more frequent in HE, which showed higher level of proteins and erythrocyte count in CSF. Neuroimaging was abnormal in all cases of HE, but only in 60% of AE. Insular and diffuse temporal lobe involvement and absence of basal ganglia involvement were more frequent in HE, and mesial temporal involvement in AE. The highest diagnostic values for differentiating HE from AE were the association of acute onset of symptoms and fever (sensitivity 0.92, specificity 1), and the absence of basal ganglia involvement (sensitivity 0.82, specificity 1).

There are few differences between HE and AE. Psychiatric symptoms and association with tumors were unique for AE. Acute onset with fever and absence of basal ganglia involvement in magnetic resonance imaging support a diagnosis of HE.