Neurocase (1999) Vol. 5, pp. 13–19  Oxford University Press 1999 Increased Focal Interictal Discharges During Specific Cognitive Tasks Olaf Blanke, Alan Pegna, Jean-Pierre Marcoz 1 , Theodor Landis and Margitta Seeck Department of Neurology, University Hospital of Geneva, 1211 Geneva, Switzerland and 1 Department of Paediatrics, Cantonal Hospital, Sion, Switzerland Abstract We present a patient with pharmacoresistant right temporal lobe epilepsy who showed a significant increase in focal interictal spikes in response to specific visuospatial tasks. Temporal spiking was particularly increased during immediate recall of visuospatial material, but not during verbal memory tasks. This reflexive phenomenon, situated in between cognitive alterations as seen in most patients with epilepsy and frank seizures elicited by higher cerebral function as in reflex epilepsy, is discussed in relation to cognition and underlying neural substrates. Introduction Various non-specific extrinsic techniques to increase interictal spiking or to facilitate seizures, such as hyper- ventilation, intermittent photic stimulation, and sleep dep- rivation are well known. In comparison, the increase in interictal or ictal epileptiform discharges by specific cogni- tive activity is extremely rare (Altafullah and Halgren, 1988; Helmstaedter et al., 1992; Binnie, 1994; Brockway et al., 1996). Interictal spikes and prolonged rhythmic ictal discharges are both intimately related to the genesis of clinically evident epileptic seizures (Hughes, 1989) and occur infre- quently in non-epileptic individuals (Zivin and Ajmone- Marsan, 1968). Rarely do highly specific intrinsic stimuli such as complex cognitive tasks (e.g. reading: Bickford et al., 1956; Wolf, 1994) induce seizures which are then referred to as reflex epilepsy. The international classifi- cation of seizures and epilepsies (Commission, 1989) con- siders reflex epilepsy to be a primary localization-related epilepsy. In contrast to primary epilepsies, clinical or EEG changes in secondary epileptic disorders are associated with the activation of a system of neurons limited to one part of the brain. In patients with partial epilepsies, the cerebral location of the cognitive deficit and of the epileptic focus were shown to converge (Jones-Gotman et al., 1993). It could further be demonstrated that the presence of interic- tal epileptic discharges during neuropsychological testing can impair the patient’s performance (the so-called TCI, transient cognitive impairment: Aarts et al., 1984; Regard et al., 1985, 1994). It is therefore advisable to monitor the EEG during neuropsychological testing in order to deduce meaningful interpretations. Cognition is known to diminish interictal spiking without a specific relation to the cognitive task (Hutt, 1972; Aarts et al., 1984). On the other hand, increase of interictal epileptic discharges during cognitive activities has rarely been reported (Altafullah and Halgren, 1988; Helmstaedter et al., 1992; Binnie, 1994; Brockway et al., 1996). Here, we present a patient with pharmacoresistant right temporal lobe epilepsy who showed a significant increase of right temporal focal spikes during visuospatial tasks, as compared to verbal material and to various control periods without neuropsychological testing. In this patient, a con- sistent relationship existed between the occurrence of a limited number of closely related mental activities and the presence of focal discharges. Materials and methods Case history This 21-year-old, right-handed, male biology student began having seizures at the age of 12 years. The habitual seizures started with an aura described as an ascending epigastric sensation, followed by manual and facial automatisms, which lasted 2–4 min. Seizure frequency was 10–20 per month, often followed by secondary generaliz- ation. Medical history revealed febrile seizures between the Correspondence to: Dr M. Seeck, Department of Neurology, Laboratory of Presurgical Evaluation for Epilepsy, University Hospital of Geneva, 24 rue Micheli-du-Crest, 1211 Geneva, Switzerland. Tel: + 41 22 3728355, Fax: + 41 22 3728340, e-mail: mase@diogenes.hcuge.ch