gms | German Medical Science

Objective: To assess long-term efficacy of deep brain stimulation (DBS) for chronic neuropathic pain in consecutive patient.

Method: Patients with chronic neuropathic pain which was refractory to medication underwent bifocal thalamic implantation of DBS electrodes. Targets were the centromedian parafascicular nucleus (CM-Pf) and somatosensory thalamus (either nucleus ventralis postereolateralis, VPL, or ventralis postereomedialis, VPM) Electrodes were implanted by CT-stereotactic surgery and externalized for 4-14 days to assess the effect of the two targets and to decide whether chronic stimulation could be administrated. Therefore DBS electrodes were either removed or a pulse generator was implanted. Assessment of pain included VAS scores and patient self rating. Patients were followed up regularly at annual visits on a long-term basis.

Results: Over a period of 16 years, a total of forty patients (20 women, 20 men; mean age of surgery 53.8 years, range 24-73 years) underwent bifocal implantation of thalamic DBS electrodes. Etiologies included central pain after stroke or hemorrhage (11 patients), complex regional pain syndrome (10 patients), atypical facial pain (5 patients), post Zoster pain (4 patients), post-amputation pain (2 patients), myelon injury (2 patients), and others. There were no surgical complications. Impulse generators were implanted in 33/40 patients for chronic stimulation, while 7 patients did not achieve adequate benefit during test stimulation. Three patients were lost to follow-up in the long-term follow-up, and in five patients the neurostimulation system was explanted due to infection. On a long-term basis, 20/33 had chronic CM-Pf stimulation and 13/33 had VPL/VPM stimulation. In three patients, the target was changed over the years or both electrodes were stimulated in parallel. The properties of marked/ excellent vs moderate/ minor vs no improvement was similar with both targets in the long-term follow-up according to patient self-rating.

Conclusions: Thalamic DBS is a useful treatment option in selected patients with severe and medically refractory neuropathic pain. While some patients achieve greater benefit with CM-Pf stimulation (which is thought to represent the paleospinothalamic projection associated with the sensation of unpleasant of pain), others prefer somatosensory thalamic stimulation (which relates to the neospinothalamic pathway transferring the most immediate pain experience. Bifocal implantation is helpful to select the optimal stimulation target in the individual patient.