Cortical Variation of Central Region in Children with Malformation of Cortical Development
Abstract number :
1.180
Submission category :
Year :
2001
Submission ID :
3050
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
T. Akai, MD, Neurosurgery, Kanazawa Medical College, Kanazawa, Japan; H. Otsubo, MD, Clinical Neurophysiology, The Hospital for Sick Children, Toronto, ON, Canada; E.W. Pang, PhD, Clinical Neurophysiology, The Hospital for Sick Children, Toronto, ON, Cana
RATIONALE: Functional mapping during epilepsy surgery, using somatosensory evoked potentials (SEP) and cortical stimulation is known to be difficult in the developing brains of children. Since MRI showed various abnormal findings of malformation of cortical development (MCD), MCD comprises a significant proportion of epilepsy surgery candidates. We analyzed whether MCD affected variation of central cortex, brain functional localization and SEP.
METHODS: We retrospectively studied 17 children with intractable epilepsy, including 9 patients with MCD, who underwent epilepsy surgery following extraoperative subdural EEG recording. Extraoperative SEP was studied by contralateral median nerve stimulation. The latency, amplitude and location of N20 and P25 were analyzed. Extraoperative electrical cortical stimulation was performed with 50Hz biphasic pulses 0.2 ms in duration.
RESULTS: Overlaps of motor and sensory cortices were more prominently found in 7 of 9 patients with MCD, compared to 3 of 8 patients with other disorders including gliosis and normal variant. Central vein did not correspond to the central sulcus in 6 of 9 children with MCD. Six of 8 with other disorders, showed central vein bordering the central sulcus between sensory-motor cortex. In 9 cases (3 MCD, 6 others), sensory cortex was involved within the epileptic region and N20 amplitudes were lower than those not involved in the epileptic region (P[lt]0.05). Latency of N20, amplitude and latency of P25 were not affected by the location of the electrodes on epilepsy focus. The existence of MCD did not affect the findings of somatosensory evoked potentials.
CONCLUSIONS: Because of more prominent mixed sensory-motor cortex and variation of central cortex in patients with MCD, accurate localization using SEP and cortical stimulation is essential for epilepsy surgery to minimize functional deficits. The amplitude of N20 was a sensitive marker for the extent of the epileptic region in somatosensory cortex.