The clinical, EEG, and radiological findings in 6 patients with the asymmetric variant of hypsarrhythmia among 26 children with infantile spasms are reported from the University of Michigan EEG Laboratory, Ann Arbor, MI. The spasms were symptomatic of cerebral dysplasia in 4, porencephaly in 1, and hypoxic-ischemic encephalopathy in 1. Focal abnormalities on neurologic exam or imaging study were found in 5 children. The abnormal EEG activity was ipsilateral to the lesion in 4 and contralateral in 1. Of hypsarrhythmia EEGs seen in this lab, 23% were asymmetric. The EEG may show focal abnormalities that are not detected by clinical exam or imaging study. [1]

COMMENT. The EEG may identify patients with infantile spasms whose lesions are amenable to surgery, even when not detected by clinical findings and imaging studies. Most cases showing asymmetric hypsarrhythmia had developmental abnormalities of the brain, primarily large cystic lesions. Cerebral tumors have been reported, eg. Branch CE and Dyken PR. Choroid plexus papilloma and infantile spasms. Ann Neurol 1979;5:302. The spasms resolved after surgery for removal of the tumor. These cases favor a primary cortical rather than brainstem origin for infantile spasms.

A generalized electrodecremental EEG resulting from a focal cortical ictal discharge and associated with partial seizures is reported in 23 patients seen at the Johns Hopkins Epilepsy Center. [2]

The surgical treatment of an early epileptic encephalopathy with suppression-bursts (Ohtahara’s syndrome) and focal cortical dysplasia is reported from Hopital Pellegrin, Bordeaux, France [3]. Infantile spasms and brief left-sided tonic unilateral seizures began at 5 days of age. The interictal EEG showed an asymmetrical suppression-burst pattern affecting the right hemisphere. MRI showed right frontotemporal cortical thickening. Seizures were resistant to AEDs and steroid therapy. The right precentral area resected showed cytoarchitectural dysplasia and ectopic neurons deep in subcortical white matter. At 1 year follow-up, the child had suffered only a “febrile seizure,” and had minor developmental delay with slight left-sided weakness. Surgery may be effective in some cases of Ohtahara’s syndrome.

Sarnat HB, University of Washington, Seattle, reviews “Ependymal reactions to injury” and focal dysplasias of the developing brain that may be secondary to damage to fetal ependyma. [4]