[A case of non-herpetic acute encephalitis presenting high intensity lesion at unilateral temparal cortex on MR FLAIR image].

We reported a case of non-herpetic acute encephalitis with unilateral temporal cortex lesion revealed by MR imaging and SPECT study. The patient was an eighteen years old woman who developed tonic-clonic seizure after common cold symptom. She was healthy before this episode. Neurological abnormality was only a single convulsion at onset and there was no other abnormal physical and neurological signs except for low grade fever. Electroencephalogram showed spike and slow wave complex of 2 Hz focused on a right posteriotemporal point (T 6) and an MR FLAIR (fluid-attenuated inversion recovery) image revealed a high signal intensity area at right temporal cortex. There was a decrease of cerebral blood flow in the same portion on SPECT study. This lesion was obscure on T1 and T2 MR images. Cerebrospinal fluid showed pleocytosis with normal glucose level and protein concentration. Bacterial and fungal cultures of CSF were negative and a detection of tubercule bacillus by PCR hybridization method was also negative. Although CSF findings suggested viral infection of CNS, virological study could not demonstrate infections of herpes simplex virus type 1, type 2, varicella-zoster virus, cytomegalovirus, measles virus, mumps virus, Japanese encephalitis virus, and influenza virus type A and B. After infusion of acyclovir and antibiotics, the patient was discharged from our hospital without sequelae of encephalitis. EEG was normal at this point and a high intensity area of MR FLAIR image disappeared two months later. SPECT findings were normalized six months later. The encephalitis presenting unilateral temporal cortex lesion without the infection of herpes simplex virus is thought to be very rare. Our case was distinguished from non-herpetic acute limbic encephalitis by an extent of the lesion and clinical manifestations. MR FLAIR image was useful for the detection of the lesion in this case.