Spinal cord stimulation modulates cerebral neurobiology: a proton magnetic resonance spectroscopy study.

INTRODUCTION: Although spinal cord stimulation (SCS) is a widely used treatment for chronic neuropathic pain secondary to spinal surgery, little is known about the underlying physiological mechanisms. METHODS: The primary aim of this study is to investigate the neural substrate underlying short-term SCS by means of (1)H MR spectroscopy with short echo time, in 20 patients with failed back surgery syndrome. RESULTS: Marked increase of γ-aminobutyric acid (GABA) and decrease in glucose in the ipsilateral thalamus were found between baseline situation without SCS and after 9' of SCS, indicating the key role of the ipsilateral thalamus as a mediator of chronic neuropathic pain. In addition, this study also showed a progressive decrease in glucose in the ipsilateral thalamus over time, which is in line with the findings of previous studies reporting deactivation in the ipsilateral thalamic region. CONCLUSIONS: The observation of GABA increase and glucose decrease over time in the ipsilateral thalamus may be the causal mechanism of the pain relief due to SCS or an epiphenomenon.

Feasibility of cerebral magnetic resonance imaging in patients with externalised spinal cord stimulator.

OBJECT: Spinal cord stimulation (SCS) is a well-known treatment option for intractable neuropathic pain after spinal surgery, but its pathophysiological mechanisms are poorly stated. The goal of this study is to analyse the feasibility of using brain MRI, functional MRI (fMRI) and Magnetic Resonance Spectroscopy (MRS) as tools to analyse these mechanisms in patients with externalised neurostimulators during trial period. METHODS: The authors conducted in an in vitro and in vivo study analysing safety issues when performing brain MRI, fMRI and MRS investigations in human subjects with externalised SCS. Temperature measurements in vitro were performed simulating SCS during MRI sequences using head transmit-receive coils in 1.5 and 3 T MRI systems. 40 Patients with externalised SCS were included in the in vivo study. 20 patients underwent brain MRI, fMRI and another 20 patients underwent brain MRI and MRS. RESULTS: A maximal temperature increase of 0.2°C was measured and neither electrode displacements nor hardware failures were observed. None of the patients undergoing the MRS sequences at the 1.5 or 3 T MRI scanners described any discomfort or unusual sensations. CONCLUSION: We can conclude that brain MRI, fMRI and MRS studies performed in patients with externalised SCS can be safely executed.

Retrograde C0-C1 insertion of cervical plate electrode for chronic intractable neck and arm pain.

OBJECTIVE: Spinal cord stimulation is an effective treatment for chronic neuropathic pain after spinal surgery. In addition to the most common placement of electrodes at the thoracic level for low back and leg pain, electrodes can also be placed on a cervical level in patients with chronic neck and upper limb pain. Surgical insertion of plate electrodes via an orthodromal direction requires a partial laminectomy. Therefore, the authors describe a surgical technique using retrograde insertion of a plate electrode to avoid laminectomy. METHODS: Six patients with uncontrolled neck and upper limb pain despite optimal analgesic medication were treated with a surgical electrode placed at the C1-C2 level via a retrograde placement technique without laminectomy. RESULTS: All patients received stimulation paresthesias at the desired regions and reported significant pain reduction in the neck and arm regions. CONCLUSION: This retrograde placement of plate electrodes enables cervical lordosis to be overcome and results in adequate stimulation of the upper cervical region, which is mandatory to reduce neck and shoulder pain without laminectomy.