Abstracts

Dual pathology is the coexistence of a potentially epileptogenic lesion and hippocampal sclerosis (HS) in a person with epilepsy. Better understanding of dual pathology may improve understanding of the pathogenesis of epilepsy and lead to better surgical treatment. We compared features of epilepsy in all subjects with dual pathology (DP) and lesional epilepsy without HS (LES-noHS) enrolled in the Multicenter Study of Epilepsy Surgery Outcomes. Features of epilepsy and outcome following epilepsy surgery were assessed prospectively using standardized questionnaires. High quality cerebral MRI emphasizing mesial temporal structures was obtained following a uniform protocol. MRI was interpreted and coded by two blinded reviewers with good interobserver reliability. Volumetric studies not performed. 33 subjects had DP and 99 LES-noHS. DP was found in 4/29 subjects with developmental or migrational abnormalities, 4/31 with cerebral tumor, 1/21 with vascular malformation, 14/43 with focal encephalomalacia, and 11/16 with cerebral hemiatrophy (one DP and 7 LES-noHS subjects had multiple lesion types). Frequency of complex partial seizures (p=.052) or generalized tonic-clonic seizures (p=.44) in the three months prior to evaluation did not differ in DP and LES-noHS. Family history of epilepsy was uncommon in both groups. 13/33 DP and 5/98 LES-noHS subjects had experienced febrile convulsions (p=.00000064). Other unprovoked seizures prior to onset of epilepsy were rare in both groups. Mean age at first unprovoked seizure didn[rsquo]t differ in DP (13.1 yrs) and LES-noHS (16.3 yrs, p=.25). However, 11/33 with DP and 16/98 with LES-noHS had first unprovoked seizure prior to age 5 (p=.038). Mean duration of epilepsy was longer in DP (24.3 yrs) than in LES-noHS (18.1 yrs, p=.014). There was also a trend to longer intractable epilepsy in DP (13.7 yrs) than in LES-noHS (9.1 yrs, p=.065). Status epilepticus occurred in 11/31 DP and 15/98 LES-noHS subjects (p=.013). 24/33 DP subjects underwent epilepsy surgery. 15/24 (63%) were free of disabling seizures in the first two years following surgery. Febrile convulsions, seizure onset prior to age 5, longer epilepsy duration, and status epilepticus are associated with the presence of HS in patients with potentially epileptogenic cerebral lesions. This suggests that both early cerebral insult and effects of seizures over time increase risk of HS in lesional epilepsy. (Supported by RO1 NS32375 (NIH-NINDS) and MINCEP[reg] Epilepsy Care)