Functional magnetic resonance imaging for assessment of language and memory in clinical practice: review

Abstract

There has been considerable interest in the role that functional magnetic resonance imaging (fMRI) may play in the assessment of patients with epilepsy. This review considers recent progress in this field and the current role of fMRI in the preoperative assessment of language and memory function. Many studies have compared fMRI with the intracarotid amytal test for establishing language dominance, with most showing over 90% concordance between the two tests. Atypical dominance is greater in patients with left temporal lobe epilepsy and has been shown to be associated with increased epileptic activity. Preoperative fMRI has been used to predict language deficits following left anterior temporal lobe resection. A variety of paradigms have been used to assess memory function, and novel paradigms have demonstrated robust medial temporal lobe activation. Different patterns of encoding activity have been observed between patients with unilateral temporal lobe epilepsy and control individuals. The application of fMRI paradigms used in cognitive neuroscience to patients with epilepsy is complicated by several factors. Although fMRI is increasingly being used clinically to establish language dominance, further work is required to localize accurately those specific language functions that are most at risk following surgery. Memory paradigms are not yet validated for use in surgical planning, although methodological and technical advances should make this possible in the near future. Further studies looking at the reorganization of language and memory function after surgery are also required.