Cortical mapping in MRI-negative epilepsy surgery

TY - CHAP

T1 - Cortical mapping in MRI-negative epilepsy surgery

AU - Alarcon, Gonzalo

AU - Valentin, Antonio

PY - 2015/4/1

Y1 - 2015/4/1

N2 - Deciding the extension of a resection for the treatment of epilepsy should include two objectives: A Resection of the regions originating seizures, and b. Avoidance of functional deficits resulting from the resection of functionally eloquent cortical areas. Obtaining adequate seizure control often involves extending the resection beyond the limits of the lesion or of the seizure onset zone. Since the regions originating seizures may be close to or merged with functional cortex, measures must be taken to minimize the risk of function loss. This is particularly relevant in patients with MRI-negative epilepsy, where most removed cortex may be structurally normal and may possibly be functional. Limited removal of association cortex does not usually induce severe neurological or cognitive deficits. However, removal of language, primary motor or sensory areas can be associated with corresponding transient or permanent deficits which should be avoided whenever possible. Unilateral temporal resections can induce memory deficits in the small proportion of patients where memory is lateralized to the resected hemisphere. Identification of functional cortex (functional mapping) is therefore of paramount importance to avoid its removal and, consequently, prevent deficits associated with resection. The first approach to localization of motor, sensory and language areas can be anatomical. However, given the individual variability in the location of these areas (Figure 13.1, see also Ojemann et al. (1) and Nii et al. (2)), their detailed localization in individual patients may be required before resection to avoid their removal. For instance, although the usual anatomical landmark to avoid receptive language area is 4–4.5 cm from the temporal pole (sparing superior temporal gyrus), functional mapping has occasionally identified language areas within 3 cm of the temporal tip (3, 4).

AB - Deciding the extension of a resection for the treatment of epilepsy should include two objectives: A Resection of the regions originating seizures, and b. Avoidance of functional deficits resulting from the resection of functionally eloquent cortical areas. Obtaining adequate seizure control often involves extending the resection beyond the limits of the lesion or of the seizure onset zone. Since the regions originating seizures may be close to or merged with functional cortex, measures must be taken to minimize the risk of function loss. This is particularly relevant in patients with MRI-negative epilepsy, where most removed cortex may be structurally normal and may possibly be functional. Limited removal of association cortex does not usually induce severe neurological or cognitive deficits. However, removal of language, primary motor or sensory areas can be associated with corresponding transient or permanent deficits which should be avoided whenever possible. Unilateral temporal resections can induce memory deficits in the small proportion of patients where memory is lateralized to the resected hemisphere. Identification of functional cortex (functional mapping) is therefore of paramount importance to avoid its removal and, consequently, prevent deficits associated with resection. The first approach to localization of motor, sensory and language areas can be anatomical. However, given the individual variability in the location of these areas (Figure 13.1, see also Ojemann et al. (1) and Nii et al. (2)), their detailed localization in individual patients may be required before resection to avoid their removal. For instance, although the usual anatomical landmark to avoid receptive language area is 4–4.5 cm from the temporal pole (sparing superior temporal gyrus), functional mapping has occasionally identified language areas within 3 cm of the temporal tip (3, 4).

UR - http://www.scopus.com/inward/record.url?scp=84952682802&partnerID=8YFLogxK

U2 - 10.1017/CBO9781139525312.014

DO - 10.1017/CBO9781139525312.014

M3 - Chapter

AN - SCOPUS:84952682802

SN - 9781139525312

SN - 9781107034235

SP - 136

EP - 152

BT - MRI-Negative Epilepsy: Evaluation and Surgical Management

PB - Cambridge University Press

ER -