Abstracts

Executive dysfunction is common in patients with frontal lobe epilepsy (FLE) and is thought to be secondary to underlying frontal lobe dysfunction. However, executive dysfunction has also been reported in a subset of patients with temporal lobe epilepsy (TLE). Thus, the specificity of executive dysfunction to FLE versus TLE is unclear. In addition, the degree of executive dysfunction in these populations may be related to disease-specific variables, including the side of the seizure focus, presence of a structural lesion, and/or the age of seizure onset. The goal of this investigation was to determine (1) the nature and extent of executive dysfunction in patients with FLE and TLE and (2) the relationships between disease-specific variables and executive dysfunction. Participants in this investigation were 23 patients with FLE (10 left, 11 right, one bilateral), 20 patients with TLE (11 left, 8 right, one bilateral), and 23 age- and education-matched controls. Fifteen patients with FLE had MRI-confirmed frontal lobe lesions. All patients with TLE had mesial temporal sclerosis. All participants completed the Delis-Kaplan Executive Functions System. Test performances were adjusted for age, gender, and education and transformed to a common metric (z scores). Composite z-scores were created for each of the following domains: switching, inhibition, fluency, abstraction, and planning. Results revealed that patients with FLE were impaired relative to controls in switching, inhibition, fluency, and abstraction, but not planning. Conversely, patients with TLE were found to be [italic]significantly[/italic] impaired only in fluency relative to controls, although their performances across domains were decreased and did not differ from those with FLE. In the FLE group, correlation analyses did not reveal a relationship between age of seizure onset and any domain of executive functioning. Instead, a left-sided seizure focus and structural lesions were associated with poorer performances. In patients with TLE, an early age of seizure onset was related to greater impairment in one domain (i.e., abstraction) regardless of the side of the seizure focus. Executive dysfunction in patients with FLE is pervasive and appears to depend on the side of the seizure focus and presence of structural pathology. In patients with TLE, executive dysfunction is relatively subtle but may be more pronounced in those with an early seizure onset. These findings are consistent with past research indicating that executive dysfunction is present in patients with FLE and TLE. However, our research extends the literature by demonstrating that the nature, extent, and disease-specific correlates of executive dysfunction differ between the patient groups. (Supported by an Epilepsy Foundation Research Fellowship Award and a NIMH Training Grant T32-MH18399.)