[Central nervous system activation in opioid dependent patients, evaluation with Fourier analysis of pupillary oscillations].

The aim of the present investigation was to determine whether Fourier analysis of pupillary oscillations permits detection of differences in the activation of the central nervous system of opioid-addicted patients. We analysed pupillary oscillations during the recording period of static pupillometry, which lasted 25.6 s. Using Fourier analysis, the spectrum was divided into five frequency bands (0.0-0.20, 0.21-0.40, 0.41-0.60, 0.61-0.80, 0.81-1.0 Hz); the total spectrum (0-1 Hz) was also assessed. Three groups of patients were selected: the group addicted to heroin (consuming exclusively heroin) consisted of 26 patients with a mean age of 25.0 +/- 6.3 years, the methadone substitution group of 20 patients with a mean age of 30.9 +/- 8.2 years, and the morphine substitution group of 20 patients with a mean age of 33.2 +/- 4.6 years. The 3 patient groups were compared with normal controls of similar age (25.1 +/- 4.6 years). In the frequency band of 0.0-0.20 Hz the morphine group showed significantly lower amplitudes than the heroin group. Also in the frequency band of 0.41-0.60 Hz the morphine group differed significantly from the other groups concerning lower amplitudes, reflecting deactivation. In the total spectrum of 0 to 1 Hz the differences between these two groups were significant. Comparison with normal controls also showed significant differences. The groups were further divided according to dose (high/low): Patients of the heroin group as well as those of the methadone and morphine groups who had consumed higher doses showed greater activation of the central nervous system. In conclusion the morphine group was more deactivated than the methadone and heroin group and patients who received higher doses of the substances showed greater central nervous activation. Thus, the measurement of central nervous activation by means of Fourier analysis of pupillary oscillations might be useful in monitoring substitution therapy.