Time-frequency mapping of R-R interval during complex partial seizures of temporal lobe origin

Background: Activation of autonomic nervous system is common with seizures. No reliable biological markers of impending seizures have been found. Evaluation of autonomic changes might help elucidate the transition from interictal to ictal states. Methods: We studied twelve patients eight females, four males, from 19 to 62 years old with temporal lobe complex partial seizures CPS . Dynamics of autonomic functions from oscillations in R-R interval RRI using time-frequency mapping based upon a Wigner distribution during pre-ictal, ictal and post-ictal periods. Oscillations in RRI at respiratory frequencies (RF) (> 0.1 Hz) are parasympathetically mediated and at nonrespiratory frequencies NONRF (0.01-0.09 Hz) are under combined sympathetic and parasympathetic influence. Results: CPS evoked marked autonomic imbalance and tachycardia. Spectral powers at both RF-RRI and NONRF-RRI increased over the pre-ictal period. RF-RRI power then fell rapidly over the 30 s before seizure onset and remained markedly reduced during seizure P < 0.004). NONRF-RRI power reached a maximum at seizure onset and declined to a minimum before the seizure cessation (P < 0.05). Conclusion: Time-frequency analysis revealed that autonomic activation hallmarks clinical seizure onset for several minutes. After combined parasympathetic and sympathetic activation, rapid parasympathetic withdrawal occurred ~ 30 s before the seizure, and sympathetic activation peaks at seizure onset. Therefore, the transition from interictal to ictal states is relatively long and associated with subclinical autonomic changes. (C) 1999 Elsevier Science B.V. All rights reserved.