Current trends in electroencephalography

Several recent articles re-emphasize the value of clinical electrophysiolog y: in localizing epileptogenesis, predicting effectiveness of epilepsy surg ery, and disclosing a mechanism of benign Rolandic epilepsy of childhood. A review of the role of EEG in the diagnosis of epilepsy indicated that epi leptiform activity will appear in 50% of initial awake recordings of adults with epilepsy and in 85% of subjects undergoing two recordings. This contr asts with the appearance of spikes in only 4 of 1000 normal persons. Severa l studies focused on the value of electroencephalography in extratemporal e pilepsy: 62% of patients with neocortical epilepsy had at least one localiz ing ictal EEG; occipital and temporal neocortical seizures were localized i n a greater proportion than frontal or parietal attacks. Interictal spikes, if unifocal, always arose from the epileptogenic region in a study of thei r seizure localizing value. Such congruence augured for better seizure cont rol by focal resection in two studies reviewed herein. Studies indicating the value of interictal temporal lobe spikes and scalp-r ecorded seizures in lateralising a temporal seizure focus are reviewed. One study found EEG to be slightly more reliable for lateralization of tempora l epileptogenesis than MRI, In patients with benign Rolandic seizures, enha nced motor evoked potentials (MEPs) were obtained from transcranial magneti c stimulation when this was applied 50-80 msec after electrical stimulation of the thumb whereas this interval inhibited the MEP in normal subjects. T his suggests that afferent cutaneous input abnormally and synchronously act ivates a large population of sensory neurons; such activation is subsequent ly transmitted to the motor cortex to produce the focal spikes in this cond ition. Finally, advances in non-invasive technology have redefined and limited the need for invasive monitoring in children with intractable seizure disorder s. Curr Opin Neurol 14:193-197. (C) 2001 Lippincott Williams & Wilkins.