Relapsed Herpes Simplex Virus Encephalitis after Epilepsy Surgery
An 11-year-old boy with a past medical history of HSV encephalitis at the age of five presented to Severance Children’s Hospital with a history of intractable seizures for the past six years. He had been healthy with normal neuropsychological development until the onset of the encephalitis. Magnetic resonance imaging (MRI) demonstrated focal encephalomalacia in the right temporal and left parietal lobes, suggestive of sequelae of previous insult (). He had suffered from daily convulsive seizures, which were sometimes provoked by auditory stimulation. His electroencephalogram (EEG) showed diffuse slowing in both hemispheres; frequent generalized slow sharp and wave discharges; frequent generalized paroxysmal fast activities; and frequent sharp waves from multifocal areas with ictal episodes originating from the left parietal area. He underwent left parietal cortisectomy after an extensive presurgical evaluation. Five days after the operation, he presented with a high fever, lethargy and recurrent seizures. Cerebrospinal fluid (CSF) examination by lumbar puncture showed 5/mm3 red blood cells, 105/mm3 white blood cells (99% lymphocytes), 90.1 mg/dL protein, and 60 mg/dL glucose. CSF HSV type 1 PCR was positive, and CSF HSV culture was not available. Brain tissue pathology from cortisectomy revealed focal cortical dyslamination with giant and dysmorphic neurons, accompanied by focal microglial cell nodules (CD 68 positive) with perivascular lymphocytic infiltrations that implied an old viral infection which is consistent with focal cortical dysplasia (FCD) type IIId. Brain MRI showed swelling and hyperintensity in the left temporoparietal region on T2-weighted images that were widely distributed from the surgical resection margin, suggesting the possibility of ischemic insult or infection (). EEG showed excessive delta activity, generalized rhythmic sharp wave discharges, and occasional subclinical seizures from the left occipital area. Intravenous acyclovir 45 mg/kg/day was initiated after relapsed HSV encephalitis was suspected based on these results. High spiking fever and altered mental status improved during the three-week intravenous acyclovir treatment. When he visited the outpatient clinic one month later, our patient’s neurological function had returned to baseline status, including cognition, mental, speech, and motor functions.