Epilepsy and cognitive impairment

As far back as the seventeenth century, Thomas Willis recognized that long-term epilepsy could bring on ‘stupidity’, a term roughly corresponding to our notion of dementia (Zimmer, 2004). Nineteenth-century authors such as Henry Maudsley and William Gowers both regarded epileptics as prone to dementia or defective memory; Maudsley thought such decline inevitable (Brown & Vaughan, 1988). Their views may have been determined by clinical practice amongst patients with very severe seizure disorders, and with the advent of effective antiepileptic drugs in the twentieth century a more optimistic outlook generally prevailed. Now, however, cognitive impairment in epilepsy is once again a subject of increasing concern. Rather than an ‘epileptic dementia’, it is now thought better to consider ‘dementia in people with epilepsy’, a syndrome with various possible causes.

The marked heterogeneity of epilepsy syndromes, with respect to factors such as site of seizure origin (generalized versus partial, or localization-related), aetiology (idiopathic versus symptomatic), and pathology (Engel & Pedley, 1997; Panayiotopoulos, 2002), means that definition of a specific profile of neuropsychological impairments is as untenable for epilepsy as it is for cerebrovascular disease. Nonetheless certain common patterns may be identified in certain epilepsy syndromes.

Historically, epilepsy surgery provided one of the critical clues to the relevance of certain brain structures in cognitive function through one of the most remarkable cases in the history of neuropsychology, Henry or HM, who developed profound anterograde amnesia following surgical removal of the anterior temporal lobes, including the hippocampus, bilaterally for intractable seizures of temporal lobe origin (Scoville & Milner, 1957; Ogden, 2005).