Mapping of cognitive functions in chronic intractable epilepsy: Role of fMRI

Abstract

Background: Functional magnetic resonance imaging (fMRI), a non-invasive technique with high spatial resolution and blood oxygen level dependent (BOLD) contrast, has been applied to localize and map cognitive functions in the clinical condition of chronic intractable epilepsy.

Purpose: fMRI was used to map the language and memory network in patients of chronic intractable epilepsy pre- and post-surgery.

Materials and methods: After obtaining approval from the institutional ethics committee, six patients with intractable epilepsy with an equal number of age-matched controls were recruited in the study. A 1.5 T MR scanner with 12-channel head coil, integrated with audio-visual fMRI accessories was used. Echo planar imaging sequence was used for BOLD studies. There were two sessions in TLE (pre- and post-surgery).

Results: In TLE patients, BOLD activation increased post-surgery in comparison of pre-surgery in inferior frontal gyrus (IFG), middle frontal gyrus (MFG), and superior temporal gyrus (STG), during semantic lexical, judgment, comprehension, and semantic memory tasks.

Conclusion: Functional MRI is useful to study the basic concepts related to language and memory lateralization in TLE and guide surgeons for preservation of important brain areas during ATLR. This will help in understanding future directions for the diagnosis and treatment of such disease.

Keywords: Cognition; functional magnetic resonance imaging; intractable epilepsy.

Figure 1(A-L)

The BOLD activation on group analysis in controls (A, D, G, J), pre-surgery TLE group (B, E, H, K), and post-surgery TLE group (C, F, I, L) during (i) semantic lexical reading (A,B,C); (ii) semantic judgment task (D,E,F); (iii) semantic reading (simple sentence) task (G, H, I); and (iv) semantic syntactic reading (jumbled sentences) task (J, K, L). (LH: Left hemisphere, RH: Right hemisphere, STG: Superior temporal gyrus, MTG: Middle temporal gyrus, IFG: Inferior frontal gyrus, PoCG: Post central gyrus, PrCG: Precentral gyrus)

Figure 2(A-C)

BOLD activation during verbal memory task in (A) healthy control (B) pre-surgery TLE, and (C) post-surgery TLE (STG: Superior temporal gyrus, MTG: Middle temporal gyrus, IFG: Inferior frontal gyrus, MFG: Middle frontal gyrus)