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Hemihypsatthythmia; Herpes Simplex Encephalitis. A 4-year-old boy with intractable epilepsy caused by herpes simplex encephalitis at 2 years of age.
His seizure is described as “very frequent clusters of asymmetric tonic spasms with left-sided predominance accompanied by head and eye deviation to
the left side, with or without horizontal nystagmus with fast component to the left side.” MRI showed severe encephalomalacia of the entire right
hemisphere with mild left cerebral atrophy. Interictal EEG shows a hypsarrhythmic pattern over the left hemisphere with severe background suppression
and multifocal sharp waves over the right hemisphere. This EEG pattern is compatible with left hemihypsarrhythmia. The patient showed significant
improvement of seizures after the right functional hemispherectomy. Brain pathology can be lateralized to either ipsilateral or contralateral
Source: Epileptic Encephalopathy, Atlas of Pediatric EEG
hemihypsarrhythmia.31
Citation: Laoprasert P. Atlas of Pediatric EEG; 2011 Available at: http://mhmedical.com/ Accessed: May 05, 2017
Infections are considered to be etiological factors in 10% of patients with infantile spasms (congenital or acquired cytomegalovirus (CMV), congenital
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rubella, herpes simplex virus, enterovirus, adenovirus, meningococcus, pneumococcus, pertussis, and unknown agents). The outcome of children with
infectious etiology is poor.76 herpes simplex virus (HSV-1) and varicella-zoster virus (VZV) are the most common causes of sporadic encephalitis in adults
and children, respectively.77 Sixty-one percent of children have early seizures and an associated poor outcome.78