Abstracts

RATIONALE: It is well known that seizures alter autonomic nervous function, but quantitative studies correlating autonomic nervous system function with the temporal evolution of seizures are lacking. We studied changes in facial temperature, a sensitive index of autonomic function, during complex partial seizures. METHODS: Thermal images of six epileptic patients undergoing invasive surgical evaluation were obtained with an infrared camera placed 6 ft in front of the patient. Each thermal scan took 15 s to complete and was saved in digital format on a computer. Sets of five successive scans triggered with a validated detection algorithm (Epilepsia, 1998 39(6):615-627) were collected. Interictal scans were also obtained at hourly intervals. Only full frontal facial images were analyzed: these were available from three of the six subjects. Software was developed to segment the facial region on each thermal image and compute the median temperature of the facial pixels during seizures (Ts) and interictally (Tii). Three pairs of parameters were compared using the Kolmogorov-Smirnov and Student's t tests: 1.Ts and Tii; 2.Coefficients of variation CVs and CVii, across five scans, of Ts and Tii respectively; 3.Deviations es and eii, of Ts and Tii respectively, from a baseline signal Tb corresponding to circadian variations in median facial temperature. Baselines were constructed by connecting the median value of Tii in each two-hour window, and linearly interpolating to give Tb at the required scan times. RESULTS: A p value of 0.05 was considered significant in all statistical comparisons. For each of the three subjects, mean Ts was significantly lower than mean Tii by an average of 0.54 degrees C, mean CVs was not significantly different from mean CVii (except in one patient), and mean es was significantly lower than mean eii by an average of 0.31 degrees C. CONCLUSIONS: Facial temperature is reduced slightly but significantly during complex partial seizures. These changes have a close temporal correlation with ictal activity, suggesting a rapid activation of thermoregulatory systems.