Release of segmental amino acid neurotransmitters in response to peripheral afferent and motor cortex stimulation: a pilot study

Management of chronic limb pain with spinal cord stimulation

BACKGROUND

Spinal Cord Stimulation (SCS) is a treatment option for chronic pain patients. The most common indication for SCS is the failed back syndrome with leg pain. In the last decade, advances in our understanding of appropriate stimulation programming, lead placement and the physiology of SCS, have led to changes in multi-site stimulation, and stimulation with differing programs. In the past, low back, axial neuropathic type pain was not responsive to SCS. With dual electrode arrays, and dual stimulation with alternating programs of stimulation, steering of stimulation paresthesia, and versatile programmable stimulation parameters, SCS has become a more versatile form of analgesia.

PURPOSE

To describe the current treatment rational for SCS and the results of that treatment.

RESULTS

The SCS is most efficient in patients with neuropathic pain of the extremities and less efficacious in patients with axial pain.

CONCLUSION

SCS is the most effective treatment for limb pain not amenable to surgical decompression. The success of SCS in this chronic pain group is 80% successful in treatment of leg pain, and much less effective in treatment of axial pain.

Neuroaugmentation in the management of sacroiliac joint pain. Report of two cases

STUDY DESIGN

A report of two cases of severe sacroiliac pain that were resistant to conventional management techniques. Both patients had undergone lumbar fusion. This appeared to be a predisposing factor.

OBJECTIVE

To define the source of pain in these patients by performing a series of diagnostic blocks under fluoroscopic guidance to determine if these patients were candidates for neuroaugmentation.

SUMMARY OF BACKGROUND DATA

Mild to moderate sacroiliac joint pain can be managed conservatively with analgesics, anti-inflammatory drugs, and physical therapy. Severe sacroiliac joint pain can be incapacitating and more challenging to manage. Fluoroscopically guided intra-articular local anesthetic-steroid injections, followed by joint manipulation, can be effective, intracapsular injections of glycerin, glucose, and phenol also may be beneficial in some patients. The use of neuroaugmentation to manage pain of synovial origin has not been reported previously. Sacral nerve root stimulation in particular has been used to manage urinary bladder dysfunction and pain, but not sacroiliac joint pain.

METHODS

Two patients with severe sacroiliac joint pain were treated by implanting a neuroprosthesis at the third sacral nerve roots. The patients had undergone lumbar fusion for back pain that developed as a result of work-related injuries. Stimulation was tried for 1 week with bilateral, percutaneously implanted, cardiac pacing wires at the third sacral nerve roots.

RESULTS

Both patients experienced relief of approximately 60% of their pain during the trial period. Therefore, a neuroprosthesis (Medtronics, MN) was implanted permanently bilaterally at the third sacral nerve root in both patients. The use of analgesics was reportedly the same after implantation, but significantly more effective, and the patients' daily living activities were more tolerable.

CONCLUSIONS

Two cases of refractory sacroiliac joint pain are reported that were managed with permanently implanted neuroprostheses at the third sacral nerve roots. The authors suggest that neuroaugmentation can be a reasonable option in selected patients with refractory sacroiliac pain.

Epidural electrical stimulation of the motor cortex in patients with facial neuralgia

Chronic facial neuralgias often do not respond sufficiently to standard treatment methods. Alternative modalities are needed for long-term reduction of pain in such cases. The present preliminary report describes two patients with trigeminal and glossopharyngeal neuralgia, respectively, treated with standard methods without obtaining satisfactory pain relief. Electrical stimulation of the motor cortex contralateral to the pain area was employed in both cases and proved able to produce a long-term facial pain reduction. Alleviation of pain occurred after activation of the flat quadripolar electrode placed epidurally on the precentral cortical area and lasted as long as the stimulator was working. By changing the polarity of the electrodes, it was possible to induce tingling sensations and muscle activation not only contralaterally to the stimulated motor cortex, but also in the ipsilateral part of the face. No stimulator-independent pain reduction resulted from long-term use of the stimulation device. During a follow-up period of 18 months, a sufficient and relatively stable analgesic effect of electrostimulation was observed. One major complication of motor cortex stimulation during the follow-up period was a single generalized epileptic seizure in one of the patients.

Reduction in thermal hyperalgesia by intrathecal administration of glycine and related compounds

We have previously shown in animal models that enhanced segmental glycine release is produced by neuroaugmentation techniques commonly used to control pain in humans. Our current hypothesis is that glycine administered intrathecally reduces the pain response evoked by the hotplate analgesia meter method. Neuropathic rats created by unilateral partial ligation of the sciatic nerve were treated with intrathecal infusion of glycine, strychnine, MK-801, or 5-7 DKA at 0.1 mumol for 2 hours at a rate of 10 microliters/min. Time required for limb withdrawal at 42 degrees C was significantly increased after glycine administration but not altered by strychnine, a specific glycine receptor antagonist. Administration of the NMDA receptor antagonist, MK-801, blocked the influence of glycine, with a less obvious antagonistic response from 5.7 DKA. Our results provide evidence that glycine and related compounds significantly modify thermal hyperalgesia, and may operate primarily through the NMDA receptor complex.

Reduction in the mechanonociceptive response by intrathecal administration of glycine and related compounds

We have previously reported that enhanced glycine release is produced by epidural spinal cord stimulation, a clinical method for treating neuropathic pain. Our current hypothesis is that glycine administered intrathecally reduces neuropathic pain as measured by the Randall-Selitto method. Neuropathic rats created by unilateral partial ligation of the sciatic nerve were treated with intrathecal infusion of glycine, strychnine, MK-801, or 5,7-DKA at 0.1 mumol, or artificial CSF for 2 hours at a rate of 10 microliters/min. Force required to produce the pain response was significantly increased after glycine administration and reduced using strychnine, a specific glycine receptor (Gly l) antagonist. Strychnine blocked the response to glycine when infused together. Administration of the non-specific NMDA receptor MK-801 antagonist and 5,7-DKA, a specific glycine-NMDA receptor (Gly 2) antagonist, however, failed to block the response to glycine. Our results provide evidence for the use of glycine and related compounds to treat neuropathic pain.

Time course of energy perturbation after compression trauma to the spinal cord: an experimental study in the rat using microdialysis

Changes occurring in the extracellular fluid (ECF) concentration of energy-related metabolites were investigated in a well-characterized model of compression trauma to the spinal cord. Microdialysis probes were inserted into exposed grey matter of the dorsal horn at the level of Th 7-8, and perfused with mock cerebrospinal fluid. The trauma was produced 2 hours later by compression of the cord with a 9-, 35-, or 50-g load for 5 min. Microdialysis samples (10-minute fractions) were collected for another 2 hours following decompression. The trauma was associated with an accumulation of lactate, inosine, and hypoxanthine, and an increase in the lactate/pyruvate ratio in the ECF, indicating a profound disturbance in energy metabolism. These changes were related to the severity of spinal cord injury as well as to the spinal cord blood flow (SCBF) reductions and neurological deteriorations previously determined. Following decompression, all ECF metabolites normalized within 20-40 min after mild (9 g) to moderate (35 g) trauma. After severe trauma (50 g), resulting in complete ischemia during compression, followed by irreversible paraplegia, there was a partial recovery of ECF inosine and hypoxanthine, whereas the increase in lactate and the lactate/pyruvate ratio persisted. The results suggest that penumbra conditions prevail during the early posttraumatic period when the degree of trauma results in severe neurological deterioration and that ECF lactate levels in the spinal cord is a sensitive indicator of secondary ischemia after compression injury.