Neuromodulation therapy for post–stroke pain

Abstract

We have reported that 5 Hz cervical spinal cord stimulation (SCS) increased cerebral blood flow and induced muscle twitches in the upper extremities, and minimally conscious state patients showed a remarkable recovery of consciousness and motor function in the upper extremities compared with that in the lower extremities. From the findings of our previous study, we have applied 5 Hz cervical SCS in combination with conventional 20 Hz cervical SCS to induce paresthesia over the painful area in poststroke pain patients. We report a new SCS technique for post– stroke pain and motor weakness. Twenty–two poststroke pain patients underwent pharmacological evaluation and dual–lead SCS trials or implantation. For the pharmacological evaluation, ketamine, morphine, and thiopental tests were carried out. Using a Touhy needle, a four or eight–contact flexible cylinder–type electrode was inserted into the epidural space of the cervical or thoracic vertebrae. The patients received 5 Hz cervical SCS to induce muscle twitches for five minutes in one session, and five sessions per day were carried out. In addition, patients underwent 20Hz cervical SCS to induce paresthesia as much as they required. During the 20 Hz SCS test period in the 22 patients, pain relief was estimated as excellent (≧60% VAS score reduction) in six patients, good (30 – 59% reduction) in nine patients, fair (10 – 29% reduction) in four patients, and poor (<10% reduction) in three patients. Three patients with poor estimated pain relief were not treated with chronic SCS. Twenty–four months after chronic SCS in 19 patients, pain relief was estimated as excellent in three patients, good in nine patients, and fair in seven patients. The %VAS score reduction 24 months after chronic SCS and the results of the ketamine test showed a significant correlation (r=0.670, p=0.001) by Pearson’s correlation coefficient test. However, the %VAS score reduction and the thiopental (r=0.291, p=0.227) and morphine (r=0.327, p=0.172) tests showed no significant cor relation. In patients treated with a combination of cervical 5 Hz and 20 Hz SCS, the motor function of the upper extremities recovered remarkably. The pharmacological evaluation of poststroke pain is a useful tool for the selection of candidates for SCS, and low–dose ketamine drop infusion method is useful for increasing the effect of SCS. The combination of 5 Hz and 20 Hz SCS is a new neuro-