Extraoperative cortical stimulation of motor function in children

Chitoku, Shiro; Otsubo, Hiroshi; Harada, Yu; Jay, Venita; Rutka, James T; Weiss, Shelly K; Abdoll, Mohamed; Snead, O.Carter

« Previous Next »Pediatric Neurology
Volume 24, Issue 5 , Pages 344-350, May 2001

Extraoperative cortical stimulation of motor function in children

Shiro Chitoku, MD
- Division of Neurology and Department of Paediatrics; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
- Bloorview Epilepsy Research Program; Toronto, Ontario, Canada
- Communications should be addressed to: Dr. Chitoku; Division of Neurology and Department of Paediatrics; The Hospital for Sick Children; 555 University Ave.; Toronto, M5G IX8, Canada
Hiroshi Otsubo, MD
- Division of Neurology and Department of Paediatrics; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
- Bloorview Epilepsy Research Program; Toronto, Ontario, Canada
Yu Harada, MD
- Division of Neurology and Department of Paediatrics; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
Venita Jay, MD
- Department of Pathology; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
- Bloorview Epilepsy Research Program; Toronto, Ontario, Canada
James T Rutka, MD, PhD
- Division of Neurosurgery and Department of Surgery; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
Shelly K Weiss, MD
- Division of Neurology and Department of Paediatrics; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
Mohamed Abdoll, MSc
- Department of Population Health Sciences; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
O.Carter Snead III, MD
- Division of Neurology and Department of Paediatrics; The Hospital for Sick Children and the University of Toronto; Toronto, Ontario, Canada
- Bloorview Epilepsy Research Program; Toronto, Ontario, Canada

Received 15 September 2000; accepted 20 February 2001.

Abstract

The purpose of the study was to investigate factors altering the amperage threshold needed to provoke functional responses in children with epilepsy. Twenty patients (4–18 years of age) who underwent epilepsy surgery at our institution from 1996–2000 after insertion of subdural grid electrodes were reviewed retrospectively. Extraoperative electrical cortical stimulation was performed with 50-Hz biphasic pulses of 0.2 ms in duration using a “distance reference” technique. Amperage thresholds of primary motor responses and afterdischarges were evaluated. The patients were grouped according to underlying pathology: eight with neuronal migration disorders (group A) and 12 with other disorders (group B). The motor cortex was defined successfully in all children because the afterdischarges threshold was higher than the motor cortical threshold. Amperage thresholds ranged from 2–20 mA (mean = 7.7) for primary motor function. An inverse relationship was found between amperage threshold and age: the younger the patient, the higher the threshold (P = 0.0005). Patients in group A required a higher amperage (2–20 mA, mean = 8.6) for motor cortical mapping than those in group B (2–14 mA, mean = 6.4). Younger children with neuronal migration disorders require a higher amperage threshold to achieve adequate motor functional mapping with careful observation of afterdischarges.