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. Eval uation of autonomic changes might help elucidate the transition from interi ctal to ictal states. Methods: We studied twelve patients (eight females, f our males), from 19 to 62 years old with temporal lobe complex partial seiz ures (CPS). Dynamics of autonomic functions from oscillations in R-R interv al (RRI) using time-frequency mapping based upon a Wigner distribution duri ng pre-ictal, ictal and post-ictal periods. Oscillations in RRI at respirat ory frequencies (RF) (> 0.1 Hz) are parasympathetically mediated and at non respiratory frequencies (NONRF) (0.01-0.09 Hz) are under combined sympathet ic and parasympathetic influence. Results: CPS evoked marked autonomic imba lance and tachycardia. Spectral powers at both RF_RRI and NONRF_RRI increas ed 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 < 0.00 4). NONRF_RRI power reached a maximum at seizure onset and declined to a mi nimum before the seizure cessation (P < 0.05). Conclusion: Time-frequency a nalysis revealed that autonomic activation hallmarks clinical seizure onset for several minutes. After combined parasympathetic and sympathetic activa tion, rapid parasympathetic withdrawal occurred similar to 30 s before the seizure, and sympathetic activation peaks at seizure onset. Therefore, the transition from interictal to ictal states is relatively long and associate d with subclinical autonomic changes. (C) 1999 Elsevier Science B.V. All ri ghts reserved.