Analysis of clinical patterns and underlying epileptogenic zones of hypermotor seizures

Hypermotor seizures (HMS) are characterized by complex movements involving the proximal segment of the limbs and trunk. Although they are primarily reported in mesial frontal or orbitofrontal epilepsies, they have also been described in patients with temporal or insular epilepsies, questioning the localizing value of HMS in patients contemplating epilepsy surgery. Furthermore, HMS can include different forms of HM behaviors. Whether these clinical variations may be systematized and may reflect different locations of the epileptogenic zone (EZ) has not been evaluated yet.

We have retrospectively analyzed ictal signs and intracerebral EEG data in 11 patients presenting with HMS who became seizure free following epilepsy surgery with a minimum follow-up of 24 months. Clinical phenomena were reviewed blinded to seizure onset zone.

Two types of HMS could be distinguished in this population: HMS1, observed in six patients, mainly consisted of marked agitation that either included body rocking, kicking, or boxing, associated with a facial expression of fear. HMS2, observed in the five other patients, mainly consisted of mild agitation that included either horizontal movements or rotation of trunk and pelvis while lying on the bed, usually associated with tonic/dystonic posturing. SEEG findings showed that the EZ associated with HMS1 was mainly centered on the ventromesial frontal cortex. Conversely, HMS2 was primarily associated with an EZ localized within the mesial premotor cortex.

Although these findings remain to be confirmed by larger studies, they may help optimize the placement of intracerebral electrodes in patients contemplating epilepsy surgery.