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Magnetoencephalographic spike sources associated with auditory auras in paediatric localisation-related epilepsy
  1. I S Mohamed1,
  2. H Otsubo1,
  3. E Pang1,
  4. S H Chuang2,
  5. J T Rutka3,
  6. P Dirks3,
  7. S K Weiss1,
  8. O C Snead1
  1. 1Division of Neurology, The Hospital for Sick Children, Toronto, Ontario, Canada
  2. 2Division of Diagnostic Imaging, The Hospital for Sick Children
  3. 3Division of Neurosurgery, The Hospital for Sick Children
  1. Correspondence to:
 H Otsubo
 Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; hiroshi.otsubo{at}sickkids.ca

Abstract

Objective: To characterise magnetoencephalographic spike sources in paediatric patients with auditory auras and recurrent localisation-related epilepsy.

Methods: Six patients (four boys and two girls (ages 7–14 years) were retrospectively studied. All patients had auditory auras as part of their initial seizure manifestation, including four patients who underwent previous brain surgery. Scalp video electroencephalography and magnetoencephalography (MEG) were carried out in six patients, intraoperative electrocorticography in three patients and extraoperative intracranial video electroencephalography in one patient. MEG auditory-evoked fields (AEFs) were studied in four patients.

Results: Three patients had elementary auditory auras, one had complex auditory aura and two had both complex and elementary auras. All six patients had clustered MEG spike sources with coexisting scattered spike sources. MEG clusters were localised in the superior temporal gyrus with surrounding scatters in four patients (two left and two right); two patients had scattered spikes in the superior temporal gyrus in addition to clustered MEG spike sources in the left inferior and middle frontal gyri or parieto-occipital region. AEFs were located within an MEG cluster in one patient and within 3 cm of a cluster in two patients. Surgical resection, including the regions of MEG clusters, was carried out in four patients. Three of four patients who had previous surgeries were seizure free at 2 years after excision of the MEG cluster region.

Conclusions: MEG spike sources clustered in the superior temporal gyrus in six patients with auditory auras. These spike sources were in close proximity or seemed to engulf the magnetic AEF. Areas with MEG spike sources contained the residual or recurrent epileptogenic zone after incomplete cortical excision for lesional epilepsy.

  • AEF, auditory-evoked field
  • DNET, dysembryoplastic neuroepithelial tumour
  • ECD, equivalent current dipole
  • ECoG, electrocortigraphy
  • EEG, electroencephalography
  • FLAIR, fluid-attenuated inversion recovery
  • IVEE, intracranial video electroencephalography
  • MEG, magnetoencephalography
  • MRI, magnetic resonance imaging
  • MST, multiple subpial transection

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Footnotes

  • Published Online First 4 August 2006

  • Competing interests: None.

  • Ethical approval: This study was conducted using protocols approved by the Hospital for Sick Children Research Ethics Board.

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