Clinical patterns and pathophysiology of hypermotor seizures: an ictal SPECT study

Hypermotor seizures (HMS) can include different forms of hypermotor behaviour due to various mechanisms associated with generation of ictal automatisms. Despite the varied location of seizure onset, similar semiologic features during seizures may exist. Ictal single-photon emission tomography (SPECT) apparently reflects not only the origin of epileptic discharge but also the spread to adjacent cortical areas. Taking this benefit of SPECT studies into account, preoperative SPECT results from 13 patients with HMS who underwent epilepsy surgery were analysed. The radioisotope 99mTc-ECD was injected in all patients within five seconds after seizure onset. Group analysis was performed with statistical parametric mapping (SPM) of paired ictal-interictal SPECTs in order to identify regions of significant ictal hyperperfusion. Hyperperfused regions with a corrected cluster-level significance p-value of < 0.002 were considered significant. Seizure onset at implanted subdural electrodes was defined as the epileptic focus in 12 of 13 patients. Two patterns were recognized: HMS-1 with marked agitation and HMS-2 with mild agitation. Ictal hyperperfusion images revealed significant hyperperfusion in the anterior cingulate cortex, orbito-frontal gyrus, lentiform nucleus, midbrain and pons. These hyperperfused areas represent the symptomatogenic zone which was different from the epileptogenic zone, as confirmed by the favourable outcomes after surgical resection. The present findings suggest that a network, including frontal and possibly extrafrontal brainstem and limbic structures, is involved in the genesis of the complex epileptic manifestations of HMS. Moreover, ictal SPECT analysed by SPM is a useful method for studying the neural networks of different types of seizures.