title: Partial epilepsy manifesting atonic seizure: report of two cases.
abstract: OBJECTIVE
  Atonic seizures are commonly seen in patients with generalized epilepsy but only infrequently in patients with partial epilepsy. Clinically generalized atonic seizures as a partial epilepsy have not been studied in detail with video/EEG monitoring. Here we describe the clinical and physiologic characteristics of atonic seizures due to partial epilepsy and discuss the underlying mechanism.
  
  
  METHODS
  Two patients with partial epilepsy manifesting atonic seizures, one with frontal lobe epilepsy (FLE) and the other with parietal lobe epilepsy (PLE), were reported. The long-term video/EEG monitoring, magnetic resonance imaging (MRI), and interictal fluorodeoxyglucose-positron emission tomography (FDG-PET) were investigated in each patient.
  
  
  RESULTS
  Paroxysmal diminution of muscle tone mainly involved the axial muscles in both patients. In contrast with the abrupt falls seen in patients with Lennox-Gastaut syndrome, the falls in these patients were slow, taking 2-5 s to fall down. Ictal EEG records showed low-voltage fast activity in the frontocentral area followed by repetitive spikes at the midline frontocentral area in the patient with FLE, and rhythmic spikes in the left central area in the patient with PLE. Interictal FDG-PET disclosed hypometabolic regions consistent with the clinical and EEG findings.
  
  
  CONCLUSIONS
  Slow falls might be a feature of atonic seizures in partial epilepsy. Long-lasting atonia in partial epilepsy could be due to either one of the following two possible mechanisms: (a) epileptic activities arising from the negative motor area, of which 50-Hz electric stimulation causes motor inhibition, or (b) sustained atonia with successive electromyogram (EMG) silent periods caused by epileptic discharges arising from the inhibitory area of the primary sensorimotor area.
authors.affiliation: Human Brain Research Center, Departments of Neurology and Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Satow
authors.forename: Akio
authors.initials: A
authors.lastname: Ikeda
authors.forename: Junichi
authors.initials: J
authors.lastname: Yamamoto
authors.forename: Motohiro
authors.initials: M
authors.lastname: Takayama
authors.forename: Masao
authors.initials: M
authors.lastname: Matsuhashi
authors.forename: Shinji
authors.initials: S
authors.lastname: Ohara
authors.forename: Riki
authors.initials: R
authors.lastname: Matsumoto
authors.forename: Tahamina
authors.initials: T
authors.lastname: Begum
authors.forename: Hidenao
authors.initials: H
authors.lastname: Fukuyama
authors.forename: Nobuo
authors.initials: N
authors.lastname: Hashimoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shibasaki
mesh_terms: D000328:Adult; D002648:Child; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D004832:Epilepsy, Absence / Q000209:etiology*; D017034:Epilepsy, Frontal Lobe / Q000503:physiopathology; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic; D010296:Parietal Lobe / Q000503:physiopathology; D013690:Television; D014055:Tomography, Emission-Computed
chemical_list: D019788:Fluorodeoxyglucose F18