title: Epileptic spasms in older pediatric patients: MEG and ictal high-frequency oscillations suggest focal-onset seizures in a subset of epileptic spasms.
abstract: OBJECTIVE
  To elucidate the pathophysiology of intractable epileptic spasms in older children by describing the interictal magnetoencephalography spike sources (MEGSSs), intracranial EEG ictal-onset zones (IOZs) and their ictal high-frequency oscillations (HFOs) and surgical outcomes.
  
  
  METHODS
  We studied five patients (4.5-14 years) who underwent surgery following intracranial video-EEG (VEEG) monitoring. We analyzed clinical profiles, MRIs, scalp and intracranial VEEGs, and MEGSSs. We localized ictal HFOs using a sampling rate of 1000 Hz and multiple band frequency analysis (MBFA).
  
  
  RESULTS
  Seizure onset ranged from 0.4 to 8 years. Three patients presented with asymmetrical spasms. Interictal scalp VEEG recorded predominantly unilateral epileptiform discharges in four; generalized and multifocal in one. Ictal scalp VEEG showed generalized high-amplitude slow waves with superimposed fast waves in four patients; hemispheric electrodecremental episodes in one. MRI findings were normal in three, hemispheric polymicrogyria and periventricular heterotopia in one each. All patients had unilateral MEGSS clusters. Ictal HFOs, ranging from 150 to 250 Hz, localized over Rolandic and frontal regions in four, with one also having extensive temporo-occipital HFOs. After cortical resection, three patients were seizure free; one had >90% reduction in seizure frequency. One patient experienced residual seizures after resection of the hemispheric ictal HFO region.
  
  
  CONCLUSIONS
  Unilateral clusters of MEGSSs overlapped regional IOZs in older patients with epileptic spasms. High spatio-temporal MBFA before and during spasms revealed the regional ictal HFOs. Seizure-free outcomes following resection of zone with MEGSS clusters and ictal HFOs suggested that a subset of epileptic spasms was focal-onset seizures.
authors.affiliation: Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada M5G1X8. rnair@mcmaster.ca
authors.forename: Rajesh
authors.initials: R
authors.lastname: Ramachandrannair
authors.forename: Ayako
authors.initials: A
authors.lastname: Ochi
authors.forename: Katsumi
authors.initials: K
authors.lastname: Imai
authors.forename: Mony
authors.initials: M
authors.lastname: Benifla
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Akiyama
authors.forename: Stephanie
authors.initials: S
authors.lastname: Holowka
authors.forename: James T
authors.initials: JT
authors.lastname: Rutka
authors.forename: O Carter
authors.initials: OC
authors.lastname: Snead
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Otsubo
mesh_terms: D000293:Adolescent; D000927:Anticonvulsants / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004351:Drug Resistance; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000139:chemically induced / Q000503:physiopathology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D019635:Neurosurgical Procedures; D012640:Seizures / Q000150:complications / Q000503:physiopathology*; D013035:Spasm / Q000209:etiology / Q000503:physiopathology*; D016896:Treatment Outcome
chemical_list: D000927:Anticonvulsants