DefinePK

Abstract

Introduction


The most common cause of sporadic encephalitis, in adults, is Herpes Simplex.1,2 About 10-16% of all encephalitis are due to HSV.3,4 High mortality rate of about 50-70% is associated with untreated HSE. Fewer than 3% survivor's return to normal neurologic function.2,5 Morbidity and mortality can be reduced by early recognition and prompt antiviral therapy.6 Early, in the disease course, serology and the polymerase chain reaction (PCR) test of cerebrospinal fluid (CSF), for the presence of the virus, may remain normal. The sensitivity of CSF PCR for HSV is reported to be 90% and specificity around 92%.7 CT scan and MRI, which is more sensitive, can show the characteristic findings of medial temporal lobe and insular involvement, which can contribute significantly to the diagnosis of HSE. The lesions can also involve, unilaterally or bilaterally, the medial temporal cortex, orbital frontal lobe, insular cortex, parietal, occipital, brain stem, internal capsule, and cingulate gyrus. The basal ganglia and lobar white matter are relatively spared. In one series, low density lesions were shown, by head CT scan, in about 70% of cases a few days after onset of symptoms.8 MRI shows hypointense lesions on T1 weighted images and hyperintense lesions on T2 weighted images at an earlier stage than by CT.9-11 These are typically seen in the temporal lobes.9-11 Characteristic clinical features of HSE, on presentation, include acute progressive onset of fever, headache, seizures, aphasia, personality changes and lethargy. Clinical features along with abnormal cerebrospinal fluid (CSF), specific cortical MRI lesions, and focal abnormalities on electroencephalography (EEG),corroborate the diagnosis of HSE. The involvement of allocortical temporal lobe pathways is particularly suggestive of HSE. The incidence of extra temporal involvement in HSE is not well known. To test the hypothesis that extra temporal involvement is common in HSE we conducted this retrospective study of consecutive patients, seen during a 12-year period, in our hospital.