The origin of hypsarrhythmia and tonic spasms in West syndrome: evidence from a case of porencephaly and hydrocephalus with focal hypsarrhythmia

We report on a 3-year-old girl with West syndrome and with focal hypsarrhyt hmia. The left hemisphere of the patient was virtually completely defective and continuous hypsarrhythmia was only seen in the residual right frontal cortex, where an interictal single photon emission computed tomography (SPE CT) showed hyperperfusion. Despite a focal epileptic pattern, the tonic spa sms were quite symmetrical. In our patient, spasms might not require the se nsorimotor cortex, but the brainstem containing the descending pathways tha t control spinal reflexes and other infratentorial structures seem to be es sential for the occurrence of spasms. This is in accordance with the result of an ictal SPECT that showed hyperperfusion of the brainstem and cerebell um. These findings suggest that hypsarrhythmia originates from cortical les ions, while subcortical structures may be primarily responsible for the ton ic spasms in this patient. (C) 1999 Elsevier Science B.V. All rights reserv ed.