Partial epilepsy presenting as focal atonic seizure: a case report.

A case of atonic seizures localized to the frontal lobe by video-EEG monitoring is reported. The patient is a 38-year-old female with intractable atonic seizures characterized by abrupt onset of facial grimacing and a slow head drop. The onset of atonic seizures was about 6 years before presentation. Video-EEG monitoring showed that her atonic seizures were emanating from the right frontal head region. A high voltage spike and slow wave discharge invariably coincided with the onset of atonic seizures in the patient, similar to the interruption of tonic muscular activity time-locked to a spike on the EEG described in epileptic negative myoclonus; a syndrome associated with epileptic activity in the premotor cortex. Since routine MRI imaging in this patient was normal, diffusion tensor imaging (DTI) was applied to analyze the white matter integrity of the normal-appearing white matter in the frontal lobes of the patient. We compared the fractional anisotropy, parallel diffusivity and perpendicular diffusivity of normal-appearing white matter in the right versus left frontal lobe. Our results showed no significant difference between the two sides. Possible reasons for the normal DTI findings are discussed.