Bilateral cortical stimulation for deafferentation pain after spinal cord injury. Case report

The relief of intractable pain after spinal cord injury (SCI) is very difficult to obtain, even with dorsal root entry zone lesioning, spinal cord stimulation, and thalamic stimulation. Using bilateral motor cortex stimulation (MCS) the authors successfully treated a woman who experienced deafferentation pain 4 years after sustaining an SCI. To the authors' knowledge, this is the first report of bilateral MCS for pain relief after SCI. The success they achieved using this method indicates that MCS could be a new treatment option for deafferentation pain following SCI.     

Motor cortex stimulation for phantom limb pain: comprehensive therapy with spinal cord and thalamic stimulation

The effects of spinal cord stimulation (SCS), deep brain stimulation (DBS) of the thalamic nucleus ventralis caudalis (VC) and motor cortex stimulation (MCS) were analyzed in 19 patients with phantom limb pain. All of the patients underwent SCS and, if the SCS failed to reduce the pain, the patients were considered for DBS and/or MCS. Satisfactory pain control for the long-term was achieved in 6 of 19 (32%) by SCS, 6 of 10 (60%) by DBS and 1 (20%) of 5 by MCS. SCS and DBS of the VC sometimes produced a dramatic effect on the pain, leading to a long pain-free interval and infrequent use of stimulation. The effects of both DBS of the VC and MCS were tested in four. One patient of them reported better pain control by MCS than by DBS, whereas two reported the opposite results. There is no evidence at present for an advantage of MCS over SCS and DBS of the VC in controlling phantom limb pain.     

Neurostimulation in the treatment of chronic pain

Different types of neurostimulation are proposed essentially in cases of chronic neuropathic pain, non controlled by anticonvulsivants and antidepressants. The aim is usually to activate a failing inhibitory system, involved in the transmission and the modulation of the nociceptive stimulus. The site of stimulation (transcutaneous, spinal cord, thalamic) is choosen according to the severity of pain and especially the degree of lemniscal dysfunction evaluated by clinical and electrophysiological data. Transcutaneous electrical stimulation and spinal cord stimulation are efficient for neurogenic pain secondary to partial deafferentation. When dysfunction or lesion extend to the pre-ganglionic portion, it's preferable to propose stereotactic thalamic stimulation or central gyrus stimulation. The analgesic effect concerns permanent burning pain in the context of sensitive deafferentation: after distal nervous lesions, radicular, plexular or spinal lesions or after stroke with ischemic lesions along the nociceptive pathways. These different methods must only be proposed if there is a frequent clinical and technical monitoring.     

Spinal epidural stimulation for central pain caused by spinal cord lesion]

Epidural spinal cord stimulation was carried out in 4 patients with denervation caused by spinal cord lesion, and we reviewed previously reported cases. Initial result showed at 1 week in 100% of our cases, but about 1/3 of the cases, even those with the same denervation caused by spinal cord lesion, had no pain relief at this stage in previously reported cases. In our cases, excellent pain relief was gained temporarily, even though the painful area and the spinal cord lesion were separated somatotopically in 2 cases (case 3, 4). Temporary success bore no relationship to quality and duration of pain. In all cases except case 1, a rapidly decreasing effectiveness was noted, and finally no pain relief was gained at all after 4, 3 and 5 months, respectively. In case 1 there was persistent pain relief estimated at 70-80% after 19 months, only when the spinal cord was stimulated. Epidural stimulation also produced sensations in the painful area. Spinal cord stimulation would suppress at least the dorsal horn neurons which were destroyed by various kinds of diseases. A decline in effectiveness with time would occur due to essential causes of the deafferentation pain, such as anatomical and regeneration factors.     

Recovery of pain control by intensive reprogramming after loss of benefit from motor cortex stimulation for neuropathic pain

INTRODUCTION: Motor cortex stimulation (MCS) may serve as an adjunct in managing neuropathic pain after other conservative and interventional methods have failed. However, the magnitude and duration of the benefit are highly variable, with a significant percentage of patients losing pain relief over time. We investigated whether intensive reprogramming could recapture the beneficial effects of MCS. METHODS: Six patients who had previously undergone MCS implantation for neuropathic pain but had lost benefit were brought back for 1-5 days of intensive reprogramming. Four patients were evaluated as inpatients while the others were seen as outpatients during multiple visits over several days. Several hours a day were spent with each patient. Patients completed visual analog scale (VAS) ratings at intervals throughout the reprogramming period to judge effectiveness of stimulation. Pre- and postadjustment VAS were compared using a paired t test. RESULTS: The patients' average age was 50 years (range 26-71). The diagnoses were trigeminal neuropathic pain (2 patients), complex regional pain syndrome I (2), phantom limb pain (1) and poststroke pain (1). The mean duration of pain was 6 years. The MCS benefit had initially lasted for a mean of 7.16 months (range 2-18 months). After reprogramming, 5 of 6 patients experienced improvement in pain. Average VAS scores decreased from 7.44 to 2.28 (p < 0.001) in those patients who responded to reprogramming. The average stimulation parameters in these patients were 5 V amplitude (range 1.7-10), 313 micros pulse width (range 240-390) and frequency of 84 Hz (range 55-130). Three patients experienced seizures during reprogramming. The mean seizure threshold was 8.9 V. No patient experienced seizures at their therapeutic settings. Pain control has been maintained after discharge. CONCLUSION: Intensive reprogramming can recapture the benefit of MCS in patients who have lost pain control. The use of broad dipoles using two contacts rather than one contact of the 1 x 4 electrode array improved the ability to recapture beneficial stimulation. There is a significant risk of seizures during aggressive reprogramming.     

Motor cortex stimulation for post-stroke pain: comparison of spinal cord and thalamic stimulation

We analyzed the effects of spinal cord stimulation (SCS), deep brain stimulation (DBS) of the thalamic nucleus ventralis caudalis (VC) and motor cortex stimulation (MCS) in 45 patients with post-stroke pain. Satisfactory pain control was obtained more frequently as the stimulation site was moved to higher levels (7% by SCS, 25% by DBS and 48% by MCS). A painful sensation was sometimes produced by stimulation of the VC as well as the post-central, pre-central and pre-frontal cortices. Such a sensation occurred less frequently as the stimulation site was moved to higher levels (50% at the VC, 39% at the post-central cortex, 6% at the pre-central cortex and 3% at the pre-frontal cortex). These findings imply that abnormal processing of nociceptive information develops at the level of deafferentation and spreads to higher levels to a varying extent. This may be one of the reasons why satisfactory pain control was obtained more frequently as the stimulation site was moved to higher levels.     

The effect of DREZ (dorsal root entry zone) lesions on intractable pain in patients with spinal cord injury

Some patients with spinal cord injury complain of a severe intractable pain. This intractable pain places new hurdles on the road to return to the ordinary daily life in these patients. The effective therapy for the intractable pain has not been established. Dorsal root entry zone (DREZ) lesion was originally reported by Nashold et al to alleviate deafferented pain syndrome. Three male and one female patients with intractable pain following spinal cord injury were treated with DREZ-lesions. One month after operation, all 4 patients obtained good pain relief. However, at a follow-up period till February 1989 (ranging 11 months from 2 years and 6 months), 2 patients had subjective pain relief. When other therapies on intractable pain following spinal cord trauma are not effective, the DREZ-lesion might be considered.     

Augmentative treatment of chronic deafferentation pain syndromes after peripheral nerve lesions.

Deafferentation pain syndromes developing after peripheral nerve lesions are difficult to treat. According to the follow-up (mean: 39.5 months) of 6 patients suffering from causalgic pain we will present our method of augmentative therapy in chronic neuropathic pain caused by peripheral nerve lesions, i.e., peripheral nerve stimulation (PNS), spinal cord stimulation (SCS) and chronic intrathecal opioid infusion. None of the patients showed intraoperative or follow-up complications. Evaluated by visual analogue scales all patients reported a good to excellent pain relief (75-100%). (1) Regarding the favourable long-term results of PNS, this method should be considered in cases of mononeuropathic pain syndromes. (2) Neuropathic pain syndromes which are not assignable to a singular nerve lesion, can often be managed effectively by SCS. (3) In contrast to the widespread opinion, deafferentation pain syndromes of central or peripheral origin can be treated satisfactorily by intrathecal opiate administration.     

The prevalence of neuropathic pain after non-traumatic spinal cord lesion

STUDY DESIGN: Retrospective register study. OBJECTIVE: To investigate the predictive value of the following parameters for the development of neuropathic pain after non-traumatic spinal cord lesion: that is age at onset of spinal cord disease, gender, completeness of lesion, level of lesion, and aetiology. SETTING: A unit for patients with post-acute traumatic and non-traumatic spinal cord lesions in the greater area of Stockholm, Sweden. METHOD: All patients with non-traumatic spinal cord lesions visiting the unit between 1995 and 2000 were classified according to the following: that is neuropathic pain at or below lesion level according to IASP criteria, age at time of the onset of the spinal cord symptoms, injury level, complete/incomplete injury, and aetiology. Results were analysed with chi(2) - analysis and logistic regression. RESULTS: In total, 38% had neuropathic pain, 15% had pain predominantly at the level of lesion, and 23% predominantly below the level of lesion. Of those with pain, 67% reported that the pain affected daily life. Women reported neuropathic pain below the level of lesion more often (40%) than men (13%). The prevalence was particularly high (64%) for patients with malignant spinal cord diseases. Neither age at onset of the spinal cord symptoms, nor complete/incomplete injury nor injury level had significant influence on the prevalence. CONCLUSION: Neuropathic pain is common among patients with acquired non-traumatic spinal cord lesions regardless of aetiology, often causing severe problems in daily life.     

Appetite suppression and weight loss incidental to spinal cord stimulation for pain relief

Spinal cord stimulation (SCS) uses electrical stimulation of the dorsal columns of the spinal cord to prevent the perception of intractable neuropathic pain signals, but its mechanisms and consequences of use are poorly understood. Two overweight female patients who were implanted with SCS systems (Precision™; Advanced Bionics/Boston Scientific, Valencia, CA) reported better than 50% relief of their chronic back and leg pain. Unexpectedly, SCS stimulation was also associated with a tingling sensation in the viscera and a reduction in appetite. Both patients were thus able to reduce food intake at mealtimes and had lost about 9 kg in the first 4 months of SCS use, despite denying changes in exercise habits. The mechanism by which SCS can reduce the desire for food is unknown, but this and similar neuromodulation techniques may hold promise for weight loss in patients who fail other treatments or are not healthy enough for surgery. All data were collected in medical practice. Dr. Foster is an employee of Advanced Bionics/Boston Scientific.     

Spinal cord stimulation does not change peripheral skin blood flow in patients with neuropathic pain

BACKGROUND AND OBJECTIVE: Spinal cord stimulation has been used successfully for many years in the management of neuropathic pain. Nociceptive pathways are closely integrated into many autonomic reflexes. The aim was to test the hypothesis that pain relief caused by spinal cord stimulation is related to changes in peripheral skin blood flow. METHODS: Twelve patients with spinal cord stimulators implanted as a treatment for neuropathic pain were entered into the study. Laser Doppler perfusion scanning was used as a direct method for selective measurement of changes in skin (peripheral) blood flow. Measurements were taken before and after the onset of spinal cord stimulation over the site of its sensory projection. The degree of pain relief due to spinal cord stimulation and the skin temperature of each patient were also recorded. RESULTS: Apart from one patient, spinal cord stimulation did not change skin blood flow in a statistically significant manner. CONCLUSIONS: Pain relief due to spinal cord stimulation is not related to changes of skin blood flow.     

Dual lead spinal cord stimulation using octad lead for central post-stroke pain

Spinal cord stimulation (SCS) has become the preferred option for neurosurgical management of several intractable pains. To evaluate effects of dual lead SCS using two quad leads for central post-stroke pain (CPSP), we retrospectively reviewed eight consecutive patients with CPSP who underwent SCS. Six (75%) of eight patients obtained more than 50% pain relief during test stimulation, and the efficacies continued for about 12 months in five (83%) of six patients. There were no significant complications. SCS is less invasive neurostimulation treatment and provides pain relief for some cases of CPSP.     

Motor cortex stimulation in patients with deafferentation pain: activation of the posterior insula and thalamus

OBJECT: The mechanisms underlying deafferentation pain are not well understood. Motor cortex stimulation (MCS) is useful in the treatment of this kind of chronic pain, but the detailed mechanisms underlying its effects are unknown. METHODS: Six patients with intractable deafferentation pain in the left hand were included in this study. All were righthanded and had a subdural electrode placed over the right precentral gyrus. The pain was associated with brainstem injury in one patient, cervical spine injury in one patient, thalamic hemorrhage in one patient, and brachial plexus avulsion in three patients. Treatment with MCS reduced pain; visual analog scale (VAS) values for pain were 82 +/- 20 before MCS and 39 +/- 20 after MCS (mean +/- standard error). Regional cerebral blood flow (rCBF) was measured by positron emission tomography with H2(15)O before and after MCS. The obtained images were analyzed with statistical parametric mapping software (SPM99). RESULTS: Significant rCBF increases were identified after MCS in the left posterior thalamus and left insula. In the early post-MCS phase, the left posterior insula and right orbitofrontal cortex showed significant rCBF increases, and the right precentral gyrus showed an rCBF decrease. In the late post-MCS phase, a significant rCBF increase was detected in the left caudal part of the anterior cingulate cortex (ACC). CONCLUSIONS: These results suggest that MCS modulates the pathways from the posterior insula and orbitofrontal cortex to the posterior thalamus to upregulate the pain threshold and pathways from the posterior insula to the caudal ACC to control emotional perception. This modulation results in decreased VAS scores for deafferentation pain.     

Predictive value of somatosensory evoked potentials for long-lasting pain relief after spinal cord stimulation: practical use for patient selection

OBJECTIVE: Spinal cord stimulation (SCS) has been used for more than 30 years in patients with intractable neuropathic pain, and global success rates have varied from 40 to 70%, according to reported series. Patient selection is currently based on a preliminary percutaneous test, which is useful but invasive, increases the risk of infection, and has yielded false-positive and false-negative results. In this study, we evaluated an alternative method of predicting the effectiveness of SCS before deciding whether to implant laminotomy electrodes-specifically, assessment of neural conduction in the dorsal columns with the use of somatosensory evoked potentials (SSEPs). Thus, we examined the value of preoperative central conduction time (CCT) of SSEPs to stimulation at the level of the painful area as a possible predictor of patient outcome after SCS. METHODS: Ninety-five patients were evaluated during a mean follow-up period of 18.8 months. Patients were classified into four categories according to the location of the lesion responsible for pain: 28 patients had lesions of the peripheral nerves, 27 had radicular lesions, 8 had root avulsions, and 32 had cord lesions. The SCS electrode was implanted through an interlaminar opening at the upper part of the painful territory without performing a percutaneous screening test. Clinical and social markers of pain relief (i.e., Visual Analog Scale scores, analgesic drug intake, work status) were evaluated prospectively 2 months after implantation and then annually. RESULTS: The global success rate in our study group, with success defined as at least 50% long-term pain relief, was 54.7% (52 of 95 patients). Statistical analyses showed a clear influence of preoperative CCT on SCS outcome. Thus, the success rate was nil in patients with significantly abnormal CCT, whereas it was 75.4% in patients with normal preoperative SSEPs. Significant differences between the two groups of patients also were observed with regard to medication intake and work status. CONCLUSION: Preoperative SSEPs provide an objective prediction of patient outcome after SCS. We suggest that if a patient's CCT is abolished or significantly altered, the patient should not undergo SCS.     

Improved Dexterity after Chronic Electrical Stimulation of the Motor Cortex for Central Pain: A Special Relevance for Thalamic Syndrome

Objectives: To demonstrate that motor cortex stimulation (MCS) could improve motor function in patients with neuropathic pain. Methods: In this prospective clinical study of 38 patients referred for MCS as treatment for their neuropathic pain, we collected any declaration of improvement in motor performance that could be attributed to MCS. Results: Ten patients (26%) declared a benefit in their motor function. Eight presented objective evidence of recovered dexterity for rapid alternating movements. A minor proportion had improvement in dystonic posture (n = 2), but none had detectable increased motor strength or tonus changes. Overall, 73% of the patients with limb ataxia declared a benefit after MCS. In 6 out of 10 patients (60%), the anatomic lesion responsible for pain was restricted to the lateral aspect of the thalamus. All of them had either clinical or electrophysiological evidence of lemniscal dysfunction (proprioceptive ataxia). No correlation was found between the scores of pain relief and the modification of motor status. The correlation between thalamic lesions and benefits in motor performance was significant (Fisher's exact test, two-tailed, p = 0.0017). Conclusions: Up to 26% of patients estimated that MCS improved their motor outcome through recovered dexterity and in cases of lateral thalamic lesions.     

Implantable technology for pain management

Neuropathic pain is a well-recognized chronic pain condition. This can have a significant impact on patients' quality of life. Neuromodulation is defined by the International Neuromodulation Society as ‘the therapeutic alteration of activity in the central or peripheral nervous system either electrically or pharmacologically’. Electrical stimulation can be performed at the motor cortex, deep brain, spinal cord, dorsal root ganglion, peripheral nerve and peripheral nerve field. Pharmacological modulation is achieved by directly infusing drugs to the central nervous system. Although neuromodulation has become increasing popular, it is still currently believed to be underused in treating neuropathic pain. This modality has provided us with a non-pharmacological approach to manage patients with neuropathic pain. Patients should have been assessed by a multidisciplinary team before undergoing neuromodulation. This review highlights the present and future management of patients with chronic intractable pain using neuromodulation.     

Implantable technology for pain management

Neuropathic pain is a well-recognized chronic pain condition. This can have a significant impact in patients' quality of life. Neuromodulation is defined by the International Neuromodulation Society as ‘the therapeutic alteration of activity in the central or peripheral nervous system either electrically or pharmacologically’. Electrical stimulation can be performed at the motor cortex, deep brain, spinal cord, dorsal root ganglion, peripheral nerve and peripheral nerve field. Pharmacological modulation is achieved by directly infusing drugs to the central nervous system. Although neuromodulation has become increasing popular, it is still currently believed to be underused in treating neuropathic pain. This modality has provided us with a non-pharmacological approach to manage patients with neuropathic pain. Patients should have been assessed by a multidisciplinary team before undergoing neuromodulation. This review highlights the present and future management of patients with chronic intractable pain using neuromodulation.     

DREZ lesions for relief of pain related to spinal cord injury

Fifty-six patients with intractable pain following a spinal cord injury were treated with dorsal root entry zone (DREZ) lesions. After a follow-up period ranging from 6 months to 6 years, 50% of patients had good pain relief. Certain pain syndromes tended to respond better to DREZ lesions than did others. Patients with pain extending caudally from the level of the injury and patients with unilateral pain were most likely to obtain pain relief from the procedure; diffuse pain and predominant sacral pain did not respond as well.     

Spinal cord stimulation in chronic pain: a review of the evidence

This review looks at the evidence for the effectiveness of spinal cord stimulation in various chronic pain states. Spinal cord stimulation can only be effective when appropriate dorsal column fibres in the spinal cord are preserved and able to be stimulated. Spinal cord stimulation has been shown to have little to offer for patients with some diagnoses. Although 50 to 60% of patients with failed back surgery syndrome obtain significant pain relief with this technique, the strength of the evidence available is insufficient to clearly advocate its use in all patients with this condition. Though limited in quantity and quality, better evidence exists for its use in neuropathic pain, complex regional pain syndrome, angina pectoris and critical limb ischaemia. There is a lack of high quality evidence relating to spinal cord stimulation due to difficulties in conducting randomized controlled trials in this area. Serious methodological problems are encountered in blinding, recruitment and assessment in nearly all published trials of spinal cord stimulation. Suggestions regarding appropriate methodologies for trials which would produce better quality evidence are summarized.     

Efficacy of motor cortex stimulation in the treatment of neuropathic pain: a randomized double-blind trial

OBJECT: In this study the authors used a double-blind protocol to assess the efficacy of motor cortex stimulation (MCS) for treating neuropathic pain. METHODS: Eleven patients with unilateral neuropathic pain (visual analog scale [VAS] score 8-10) of different origins and topography were selected for MCS. A 20-contact grid was implanted through a craniotomy centered over the motor cortex contralateral to the painful area. The motor cortex strip was identified using neuroimages, somatosensory evoked potentials, acute electrical stimulation, and corticocortical evoked potentials. Subacute therapeutic stimulation trials allowed the authors to determine the most efficient pair of contacts to use for long-term MCS. The grid was replaced with a 4-contact electrode connected to an internalized stimulator. Bipolar stimulation at a 40-Hz frequency, 90-micro sec pulse width, amplitude 2-7 V, and 1 hour in "ON" and 4 hours in "OFF" mode was used. Pain was evaluated using the VAS, Bourhis, and McGill pain scales applied each month for 1 year. At Day 60 or 90, the stimulators were turned to OFF mode for 30 days in a randomized, double-blind fashion. The statistical tool used was the Wilcoxon test. RESULTS: Three patients did not report improvement in the subacute trial and were excluded from long-term MCS; the remaining patients underwent long-term stimulation. Significant improvement of pain was induced by MCS (p < 0.01); this persisted during the follow-up period. Turning stimulation to OFF mode increased pain significantly (p < 0.05). Improvement at 1 year was >or= 40% (40-86%) in all cases. CONCLUSIONS: Motor cortex stimulation is an efficient treatment for neuropathic pain, according to an evaluation facilitated by a double-blind maneuver. Subacute stimulation trials are recommended to determine the optimum motor cortex area to be stimulated and to identify nonresponders.