Neuropsychological issues in MRI-negative focal epilepsy surgery: Evaluation and outcomes

The first epilepsy surgery began in the 1880s at Queen Square and was based solely upon clinical findings and semiology. Horsley’s first case presented with an old depressed skull fracture, with seizures beginning in the contralateral limbs. Horsley’s second case presented with seizures starting in the left thumb and forefinger. Jackson noted that the motor activity was identical to the motor response of electrical stimulation of the motor hand area in primates. At surgery, a tuberculoma was found and removed from the exact location predicted by Jackson [1]. In the 1930s, Berger first recorded electroencephalograms (EEGs) from humans, and Foerster employed EEG to guide epilepsy surgery. Soon after, Jasper and Penfield at the Montreal Neurological Institute (MNI) and Bailey and Gibbs at the University of Chicago used EEG to identify focal epileptic discharges, which led to the concept that “psychomotor seizures” commonly arose from the anterior temporal lobe (TL) and that resection of this region could control seizures. In 1950, Penfield and Flanigin published the first case series of anterior temporal lobectomies for the treatment of poorly controlled epilepsy [2]. In this era, Penfield and Jasper’s use of cortical mapping advanced our knowledge of cortical functions, and allowed tailoring of surgical resections to avoid or reduce postoperative deficits [3]. Juhn Wada developed the intracarotid amobarbital procedure to lateralize language function and was invited to the MNI to apply the technique, now commonly referred to as the Wada test, to epilepsy surgery [4]. Shortly thereafter, patient HM underwent bilateral TL resections for epilepsy and developed a severe amnestic syndrome. This case and others, including some with unilateral resections and presumed damage to the contralateral mesial TL, demonstrated the importance of these structures to memory. Milner performed detailed neuropsychological testing on HM and other patients, leading to the routine use of neuropsychology to predict cognitive outcome [5]. Milner also modified the Wada test to predict postoperative memory outcome [6].