Brain Advance Access originally published online on February 23, 2005
Brain 2005 128(4):700-710; doi:10.1093/brain/awh446
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Review Article |
Cortical triggers in generalized reflex seizures and epilepsies
1 Departments of Neurology and Neurosurgery 2 Human Genetics and 3 Pediatrics, McGill University 4 Epilepsy Clinic, Montreal Neurological Hospital and Institute, Montreal, Quebec, Canada and 5 Scuola di Specializzazione di Neurologia, Università degli Studi di Messina, Italy
Correspondence to: Benjamin G. Zifkin, MDCM, FRCPC, Epilepsy Clinic, Montreal Neurological Institute and Hospital, 3801 University Street, Room 128, Montreal, QC H3A 2B4, Canada
Activation of specific cortical territories by sensory stimuli or of less restricted areas of the brain by cognitive stimuli is known to induce apparently generalized seizures in predisposed patients; this is clinically and electroencephalographically distinct from reflex triggering of partial seizures. Photosensitive patients may have seizures when exposed to environmental stimuli producing appropriate flickering light or geometric patterns. Some children with benign myoclonic epilepsy in infancy have seizures triggered by unexpected touch or noise. Seizures induced by thinking have been reported in response to non-verbal higher mental activity such as mental arithmetic. Praxis-induced seizures are triggered by similar mental activities accompanied by the use of the hands. Language-induced seizures are usually triggered by verbal higher mental activity. Functional imaging and other methods have contributed to understanding how these seizures arise. Patients with these generalized reflex seizures appear to have regions of cortical hyperexcitability overlapping or coinciding with areas physiologically activated during specific sensory stimulations and cognitive or motor activities. When these areas receive appropriate afferent volleys and a critical mass of cortex is activated, an epileptic activity is produced that ultimately involves cortico-reticular or cortico-cortical pathways resulting in a generalized or bilateral epileptic event.
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