Clinico-electrical Characteristics of Lateral Temporal Lobe Epilepsy; Anterior and Posterior Lateral Temporal Lobe Epilepsy

Background and purpose: This study aimed to determine whether there are clinicoelectrical differences between anterior lateral temporal lobe epilepsy (ALTLE) and posterior lateral temporal lobe epilepsy (PLTLE), taking medial temporal lobe epilepsy (MTLE) as a reference.

Methods: We analyzed the historical information, ictal semiologies, and ictal EEGs of temporal lobe epilepsy patients with a documented favorable surgical outcome (Engel class I or II) at follow-up after more than one year. LTLE was defined when a discrete lesion on MRI or an ictal onset zone in invasive study was located outside the collateral sulcus. LTLE was further divided into ALTLE and PLTLE by reference to the line across the cerebral peduncle. Total 107 seizures of 13 ALTLE, 8 PLTLE and 21 MTLE patients were reviewed.

Results: Initial hypomotor symptom was frequently observed in PLTLE (P<0.001). Oroalimentary automatism (OAA) was not observed initially in PLTLE. Generalized tonic-clonic seizures occurred significantly earlier in PLTLE than in ALTLE or MTLE (P< 0.001). Ictal scalp EEG was not helpful in differentiating between ALTLE and PLTLE.

Conclusions: Frequent hypomotor onset, the absence of initial oroalimentary automatism, and early generalization are characteristic findings of PLTLE, although they are insufficient to differentiate it from ALTLE or MTLE.