上位頸髄硬膜外電気刺激による局所脳血流と脳波変化に関する実験的検討

Abstract

Currently there is considerable interest in electrical stimulation of the dorsal aspect of the cervical spinal cord as a potentially effective therapy for persistent vegetative patients. Despite the clinical attempts, the mechanism of spinal cord stimulation (SCS) remains obscure and there are scarce experimental data available regarding suitable conditions for SCS. To investigate this issue, the authors assessed change in local cerebral blood flow (LCBF) and electroencephalogram (EEG) in the cat following SCS. In 31 adult cats under isoflurane anesthesia, an electrode for SCS was implanted epidural- ly to the midline of the C2-C3 segment. Stimulation was performed at 25 Hz and 0.1 msec for 30 min. These animals were divided into five groups by the stimulation voltage : (1) 2 V (n=7), (2) 4V (n=7), (3) 6V (n=7), (4) 4V with intravenous injection of muscarinic cholinergic agents - atropine sulfate (n=5), and (5) sham-operated control (n=5) without stimulation. LCBF was measured by laser Doppler flowmetry through bilateral small burr holes at the parietal area during and 60 min after stimulation. All data from the EEG, electrocardiogram (ECG) and CBF monitors were collected sequentially by the MacLab system. At 2 V, LCBF increased only during SCS, then returned to the pre-stimulated level, while the increase continued until the end of the experiment at 4 and 6V. The increase in LCBF was not affected by atropine sulfate. EEG showed spike and wave or polyspikes after SCS in 2 animals of the 6V group, but not in the 2V and 4V groups, and moreover a moderate increase of the background activity at only 4V. The present data suggest that SCS at 4V can provide appropriate microcirculatory enhancement with less harmful influence which continues to increase 30 min after SCS, although the exact mechanism should be elucidated continuously. Within the limitation of animal experiments, this study could provide the logical basis for determining the condition of SCS.