Effectiveness of tonic and burst motor cortex stimulation in chronic neuropathic pain.

Motor cortex stimulation (MCS) is an intracranial, invasive method for treatment of chronic pain. Main indications for MCS are central post stroke pain, neuropathic facial pain, phantom limb pain and brachial plexus or spinal cord injury pain. Spinal cord stimulation (SCS) with burst waveform has been proved to be more effective than tonic mode in chronic pain. Necessity to replace depleted batteries of motor cortex tonic stimulators gave us an opportunity of applying burst stimulation. The objective of the pilot study was to evaluate the effects of burst stimulation applied on motor cortex in patients with chronic pain syndromes as well as comparison to tonic mode. We have evaluated 6 patients (females N=3, males N=3) belonging to the group of 14 cases (females N=5, males N=9) who had undergone surgical procedure of MCS in years 2005-2017. Selected for the study were 6 patients with thalamic pain N=3, with facial pain N=3 (anaesthesia dolorosa and neuropathic trigeminal neuralgia). The patients were subjected to both modes of stimulation then they chose which one was better in relieving pain: tonic or burst. Pain intensity was assessed with the visual analogue scale (VAS) before the replacement of implanted pulse generator (IPG) and after the stimulation with tonic and burst modes. In the study, 5 out of 6 patients with MCS found burst mode more effective than tonic mode. Baseline VAS score in patients that had at least 3 months depleted battery of tonic IPG was 95 mm. After implantation of a new IPG mean VAS score on tonic stimulation was 72 mm, on burst 53 mm. The most preferred option of MCS in selected group of patients was burst stimulation. This study has shown, that the burst stimulation of cerebral cortex is a promising modality when tonic stimulation is not sufficient in refractory, neuropathic pain.