Deep Brain Stimulation Effectively Relieves Post-Stroke Neuropathic Pain
Abstract & Commentary
By Alan Z. Segal, MD, Assistant Professor, Department of Neurology, Weill-Cornell Medical College, Attending Neurologist, NewYork-Presbyterian Hospital. Dr. Segal is on the speaker's bureau for Boehringer-Ingelheim.
Synopsis: This study demonstrates that deep brain stimulation is an effective treatment in 70% of post-stroke neuropathic patients.
Source: Owen SL, et al. Deep Brain Stimulation for the Alleviation of Post-Stroke Neuropathic Pain. Pain. 2006;120:202-206.
Neuropathic pain following a stroke may be a significant source of added disability for patients already suffering from severe motor or cognitive deficits. Pain may include a burning hyperesthesia, as well as a dull ache in areas that are otherwise numb. Patients are often refractory to standard pharmacological treatments used for neuropathic pain.
Owen and colleagues studied 15 post-stroke patients who were treated with deep brain stimulators (DBS). Five patients had cortical strokes, while 10 had subcortical lesions, of which 8 were thalamic; one pontine and one capsular. On average, patients had pain for 5 years prior to surgery. Deep brain electrodes were placed in the periventricular gray matter (PVG), periaqueductal gray matter (PAG), and sensory thalamus (Ventroposterolateral nucleus-VPL).
During a one-week post-operative trial period, 3 patients did not feel they were achieving significant pain relief and, therefore, did not proceed to full implantation of the pacemaker. For the remaining 12, average follow-up was approximately 2 years. Nine patients preferred chronic stimulation of the PVG, one in the VPL and 2 preferred both electrodes to be activated. The visual analogue score (VAS) for pain was reduced by 48.8% overall (P < 0.001). Patients with subcortical strokes showed more benefit in VAS scores those with cortical strokes (54% vs 42%; P < 0.001).
Among the 12 patients, 7 stopped all analgesics and 5 changed from regular scheduled opioid use to an as needed basis. Owen et al note anecdotally that a deep aching type pain often remains despite relief of burning hyperesthesia. They postulate that this deep pain may become more noticeable as the more intolerable burning disappears.
Despite a lack of controls, DBS does appear to have more than a placebo effect. As Owen et al note, the effectiveness of DBS can also be confirmed with a blinded "N of one" study in which a single patient is asked to report pain levels as the stimulator is randomly turned on or off.
The mechanism of action of DBS is as yet unclear. PVG/PAG stimulation appears to be superior to direct thalamic stimulation, as these nuclei may have an indirect inhibitory effect on the thalamus. Alternatively, PVG/PAG stimulation may result in the release of endogenous opioids and, thus, may produce pain relief for up to 24 hours after the stimulator is turned off. Though more study is needed, these data are surely a bright light of encouragement for patients suffering from centrally mediated neuropathic pain.