[Herpes simplex encephalitis originating from bilateral thalamic lesions with hemorrhagic component].

A 71-year-old woman with hypertension and hypothyroidism was transferred to our hospital from a nearby hospital because of right thalamic hemorrhage evident on CT. She had been suffered from fever and headache for five days. Neurological examination on admission revealed somnolence, rigidity in the neck and extremities, and bilateral Babinski signs. Then she developed decorticate rigidity in a day. On brain MRI four hours after admission, T2-hyperintese lesions were demonstrated in the bilateral thalamus in addition to hemorrhagic change of the right thalamus on the initial CT. No pleocytosis was evident on cerebrospinal fluid examination at admission. Follow-up MRI on the fifth hospital day, however, revealed expansion of the lesions bilaterally to the medial temporal lobes including amygdala, hippocampus and insular cortex. The diagnosis of herpes simplex encephalitis was established by PCR of cerebrospinal fluid on the same day. After immediate treatment with acyclovir and ara-A, she gradually became conscious and could respond to simple conversation. This was an unusual case of herpes simplex encephalitis originating from bilateral thalamic lesions on brain imaging. We should consider thalamus as a primary lesion in herpes simplex encephalitis.