Regional cerebral blood flow during seizure activity, measured by transcranial Doppler sonography, and SPECT were studied in three infants with Sturge-Weber syndrome (SWS), during work-up for possible epilepsy surgery at Great Ormond Street Hospital and The Institute of Child Health, London, UK. The infants presented with recurrent seizures, altered consciousness, and neurologic deficits, and two showed clinical and radiological progression of the encephalopathy. SPECT showed hemispheric hypoperfusion, and middle cerebral artery velocity (MCAV) was reduced by 30-60% in the affected hemisphere compared with the contralateral side. MCAV during seizures was increased from 6 to 30% in the involved hemisphere compared to 24-179% for the contralateral side. This hemodynamic response to seizures of the unaffected hemisphere appeared to decrease over time, leading to increased cognitive and neurologic deficits with further seizure episodes. Abnormalities of the venous circulation in SWS, with reduced capacity for increasing venous return, cause venous hypertension and chronic progressive ischemia. 
COMMENT. Sturge-Weber syndrome is characterized by epilepsy, hemiparesis, and pial and facial angiomata. The onset of seizures is often associated with neurologic deterioration and learning disability. The hemisphere underlying the venous angioma shows progressive gliosis, atrophy, and calcification, compatible with ischemia. The present study of the cerebral hemodynamics, in both affected and contralateral hemispheres, during seizure activity elucidates the cause of the progressive ischemia and neurologic deterioration in SWS. The progressive nature of the SWS encephalopathy after seizure onset, and especially in cases complicated by status epilepticus, should prompt consideration of early surgical excision. (see Progress in Pediatric Neurology I, PNB Publ, 1991;pp38-39, for report of progressive mental impairment in SWS).
Cutaneous mosaicism of lethal mutations and the lethal gene concept is proposed for Sturge Weber and other neurocutaneous syndromes . SWS is a non-hereditary disorder. The concept of autosomal lethal genes surviving only in a mosaic state is proposed to explain the genetic basis of syndromes such as SWS, characterized by sporadic occurrence, distribution of lesions in an asymmetrical pattern, lack of diffuse involvement of entire organs, and equal sex ratio.
The Sturge-Weber Foundation currently announces a new book on SWS, edited by Bodensteiner JB and Roach ES.