Abstracts

Rationale: There is evidence that seizures do not propagate diffusely or randomly, but rather, in a preferred order to involve a specific set of brain regions. Also, patients with focal seizures tend to exhibit stereotyped behaviors. However, the relationship between the neuroanatomy of seizure propagation and stereotypy of ictal behaviors remains poorly understood. The current study was designed to study the stereotypy of ictal behavior in a group of patients with focal medial temporal lobe epilepsy (MTLE), and to determine if there is a specific electrographic correlate to the onset of any ictal behavior. Methods: In 55 seizures recorded with scalp or intracranial electrodes in 10 patients with verified MTLE, the type, duration, and order of exhibited behaviors were documented. Using T-test, ANOVA, frequency-cluster-matrix analysis, and rule-mining-test we measured the commonality and directionality of ictal behaviors. For electrophysiological analysis, we used Hilbert-transform, phase locking-value, modulation-index, coherence, and synchronization-likelihood. Results: 1) a specific somatotopical subset of behaviors occurs in MTLE; 2) ictal behaviors are related to each other in time; lip-smacking always precedes arm/hand movement or vocalization; 3) lip-smacking starts 59 10secs after the initial seizure onset in the MTL; and 4) the onset of lip-smacking is always associated with a strong synchrony between ipsilateral hippocampal and inferior-lateral temporal lobe (ILTL) activity in the theta band frequency domain. Conclusions: Our findings support the notion of behavioral and electrophysiological stereotypy across a population of patients with focal epilepsy, and suggest that MTL activity is insufficient to generate the ictal behavior of lipsmacking. Recruitment of the ILTL in the theta band frequency domain seems to correlate in time with the onset of lipsmacking.