The Emerging Architecture of Neuropsychological Impairment in Epilepsy

Abstract

A new literature is now under way, one linking cognitive abnormalities directly to indices of structural, functional, metabolic, and other neurobiologic markers of cerebral integrity, independent of their association with clinical epilepsy characteristics. These trends are reviewed in this article. The focus is on temporal lobe epilepsy (TLE) as a model with which to address the core points because this form of localization-related epilepsy has been very carefully studied from both a cognitive and imaging standpoint. Some pertinent historical issues are touched on first, followed by more detailed reviews of the cognitive and neuroimaging abnormalities that have been found in TLE, followed by an overview of studies examining direct structure-function relationships in TLE and other epilepsies.

Structural and Quantitative MRI in Epilepsy

“…As summarized in a comprehensive review of VBM group studies comparing patients with TLE to healthy controls (Keller & Roberts, 2008 ), hippocampal atrophy ipsilateral to the seizure focus and bilateral thalamic atrophy are common fi ndings; however, several neocortical abnormalities can also be observed. Such fi ndings are consistent with the diverse cognitive defi cits demonstrated in TLE outside of memory impairment (Hermann, Lin, Jones, & Seidenberg, 2009 ). However, widespread neocortical atrophy associated with seizure burden must be differentiated from the presence of dual pathology, as the presence of extratemporal structural abnormalities is associated with a reduction in the likelihood of seizure freedom following a mesial temporal resection (Sisodiya et al, 1997 ).…”

Influence of Resting-State Network on Lateralization of Functional Connectivity in Mesial Temporal Lobe Epilepsy

“…[42][43][44] In previous studies, the sensorimotor network had abnormal RS-FC and the patients with mTLE displayed cognitive impairments. 38,43,45 The increased RS-FC in the sensorimotor network in the current study may be a compensatory mechanism between the left and the right sensorimotor cortex as shown in Fig 3B. In contrast, internetwork connections between the aforementioned RSNs were generally stronger in patients with R-mTLE than in control subjects. This phenomenon may have been produced by compensatory mechanisms.…”

Memory, executive function and language function are similarly impaired in both temporal and extra temporal refractory epilepsy—A prospective study

“…Studies indicate the association of cognitive impairment with factors like age of onset, seizure type, seizure frequency and localization of the seizure focus, however, there is variation in the strength of association of these factors, reported in different studies (Lah et al, 2006;Hamed, 2009). Recent literature suggests transition from a long-standing focus on the relationship between cognitive function and clinical epilepsy features to one linking cognitive impairment to underlying anatomic, metabolic, and other neurobiologic correlates of the epilepsies (Hermann et al, 2009).…”