[A high aged case of herpes simplex viral encephalitis associated with progressive cerebral white matter lesion]

An 80-year-old male without abnormal past medical history presented with coma, general seizures, and fever subsequent to abnormal behavior. The pressure of the cerebrospinal fluid(CSF) elevated(13.5-20.5 cm H2O), and CSF examination revealed pleocytosis with predominant mononuclear cells(80-879/mm3) and elevated protein level(32-130 mg/dl). DNAs of herpes simplex virus(HSV) type 1 and 2 in CSF were not confirmed by polymerase chain reaction method in the acute phase. The HSV(type 1) antibody(HSV-1 Ab) ratio of serum to CSF(= [serum HSV-1 Ab]/[CSF HSV-1 Ab]) was 0.98 and HSV-1 Ab index(= [CSF HSV-1 Ab]/[serum HSV-1 Ab] divided by [CSF albumin]/[serum albumin]) was 62.4. Initial fluid attenuated inversion recovery(FLAIR) (TR/TE/TI = 6,882/110/1,700 msec) axial magnetic resonance(MR) imaging showed hyperintensity in the subfrontal area, inferomedial portions of the temporal lobes, cingulate gyri, and insular cortices bilaterally. Meningoencephalitis caused by HSV-1 was diagnosed based on the values of HSV-1 Ab ratio of serum to CSF(less than 20), of HSV-1 Ab index(larger than 1.91), and the findings of MR imaging. Diffuse white matter lesions manifesting hyperintensity on FLAIR imaging in the bilateral frontal and temporal lobes close to the affected cortices developed approximately six weeks after the onset despite administration of antiviral agent and steroid. The lesion extensively involved the white matter of the bilateral frontal and temporal lobes finally. The initial value of myelin basic protein(MBP) in CSF was 0.9 ng/ml (normal value: less than 4 ng/ml). Subsequent measurement of MBP in CSF about two, six weeks, two, three, and six months after the onset showed a marked increase of 233.9 ng/ml followed by a gradual decrease of 25.4 ng/ml, 18.4 ng/ml, 7.4 ng/ml and 4.3 ng/ml, respectively. Therefore, demyelination of the lesion in the cerebral white matter was suggested by the chronological change in FLAIR imaging and MBP in CSF.