TEMPORAL-LOBE DEVELOPMENTAL MALFORMATIONS AND EPILEPSY - DUAL PATHOLOGY AND BILATERAL HIPPOCAMPAL ABNORMALITIES

Temporal lobe developmental malformations (TLDM) with focal cortical d ysplasia and balloon cells may coexist with mesial temporal sclerosis. The true incidence of this dual pathology is unknown. Our aim was to assess the frequency of amygdala (AM)-hippocampal abnormality in a hom ogeneous population with this specific developmental malformation. MRI -based volumetry of the AM and hippocampal formation (HF) in 30 patien ts with unilateral TLDM and intractable partial epilepsy was performed . A volume normalization process defined a normal range of HF and AM v olumes in control subjects, and enabled the detection of bilateral vol ume loss. Normalized volumes detected HF atrophy in 26 patients (nine unilateral and 17 bilateral) and AM atrophy in 18 patients (three unil ateral and 15 bilateral). Visual analysis detected unilateral HF abnor mality in 21 patients and bilateral abnormality in two. When compared with a group of patients with temporal lobe epilepsy and pure hippocam pal sclerosis (N = 92), where volumetry revealed bilateral HF atrophy in 18%, a significant difference in the frequency of bilateral HF atro phy was found (p < 0.0001). Dual pathology is frequent in patients wit h TLDM (87%), and the AM-HF abnormality is often bilateral (57%). Our data suggest that more widespread and potentially epileptogenic lesion s coexist with visibly detectable unilateral TLDM. This has implicatio ns for the selection of patients for temporal lobe surgery and may inf luence surgical strategies.