Cerebral blood flow and somatosensory evoked response changes induced by spinal cord stimulation: preliminary follow-up observations.

A group of 6 patients undergoing cervical spinal cord stimulation (SCS) because of different pathologies was studied. Multipolar leads (QUAD-Medtronic) were inserted percutaneously; following an SCS test period, leads were connected to a multiprogrammable, fully implantable generator (ITREL II). Neither surgical nor other side effects were found. Regional cerebral blood flow (rCBF) (xenon-133 inhalation) was determined in the basal condition and after 30 min of SCS. Somatosensory-evoked potential (SSERs) from the legs were recorded in basal conditions and after 45 min of SCS. In 2 patients SSERs could not be evaluated due to electrical noise from SCS. CBF increased mainly in anterior regions in 4/6 patients (P300 improved in 1 of them and in another case), and was unchanged in 2 patients. rCBF was retested after a mean of 9.5 months of continuous SCS with the same parameters. rCBF returned to basal values in the 4 patients showing an early flow increase; in contrast, rCBF increased in the other 2 cases without early flow changes. These preliminary data seem to support the view of an acute effect of SCS on rCBF as well as on SSER, at least in some patients. Differences in long-term rCBF modifications might depend on either the underlying pathology or on the different neuronal system involved by SCS.