Microsurgical junctional DREZ coagulation for treatment of deafferentation pain syndromes

Dorsal root entry zone lesioning for brachial plexus avulsion pain: a case series

STUDY DESIGN

Retrospective case series.

OBJECTIVES

Dorsal root entry zone (DREZ) lesioning can be performed in patients with intractable pain following brachial plexus avulsion (BPA). However, post-operative outcomes are variable and it is uncommonly used. We sought to determine the pain outcomes and complication profile of DREZ lesioning for BPA.

SETTING

Quaternary neurosurgical centre.

METHODS

All patients that had undergone DREZ lesioning for BPA pain over a 13-year period were included. Patients were assessed for outcome with regard to degree of pain relief and presence of complications.

RESULTS

Fourteen patients were reviewed, with a median post-operative follow-up duration of 27 months (1-145 months). Of these, ten were contactable for long-term telephone review, with a median post-operative duration of 37 months (11-145 months). At earliest review post-operatively, 12 of 14 patients (86%) had some level of pain relief: complete pain relief in four patients (29%) and partial pain relief in eight patients (57%). At most recent post-operative review, ten of 14 patients (71%) reported lasting significant pain relief: four (29%) had complete pain relief, six (43%) had partial pain relief and four (29%) had insignificant pain relief. Complications were predominantly sensory, including ataxia, hypoaesthesia and dysaesthesia. Four patients (29%) reported persistent motor complications at final follow-up.

CONCLUSIONS

DREZ lesioning is uncommonly performed. It remains a reasonable option for relief of refractory BPA pain in selected cases, though there is a significant complication rate. Future prospective studies may enable quantification of pre- and post-lesioning analgesic use, another important determinant of procedure success.

Long term results of Dorsal Root Entry Zone (DREZ) lesions for the treatment of intractable pain: A systematic review of the literature on 1242 cases

BACKGROUND

Different Dorsal root entry zone (DREZ) lesion techniques have been reported as effective treatment for intractable painful conditions, though with contradictory results. Overall, good results were reported especially in specific conditions, such as pain due to brachial plexus avulsion, spinal cord injuries and oncological pain management. However, data on long term results in different clinical conditions are still missing.

OBJECTIVE

This study aims to systematically review the pertinent literature to evaluate indications, clinical outcomes, and complications of DREZ lesion (DREZotomy), in chronic pain management.

METHODS

A systematic literature review was conducted according to the PRISMA statement. Papers on DREZotomy for chronic pain in cancer, brachial plexus avulsion, spinal cord injury, post herpetic neuralgia, and phantom limb pain were considered for eligibility. For each category we further identified two sub-group according to the length of follow up: medium term and long term follow up (more than 3 years) respectively.

RESULTS

46 papers, and 1242 patients, were included in the present investigation. When considering long term results DREZotomy provided favorable clinical outcomes in brachial plexus avulsion and spinal cord injury, in 60.8% and 55.8% of the cases respectively. Conversely, the success rate was 35.3% in phantom limb pain and 28.2% in post herpetic neuralgia. A poor clinical outcome was reported in over than 25% of the patients suffering from phantom limb pain, post herpetic neuralgia and spinal cord injury. The mean complications rate was 23.58%. While BPA and SCI patients presented stable improvement over time, good outcomes among PHN and PLP groups dropped by - 46.2%; and - 14.7% at long term follow up respectively.

CONCLUSION

DREZotomy seems to be an effective treatment for chronic pain conditions, especially for brachial plexus avulsion, spinal cord injury and intractable cancer/post-radiation pain. According to the low level of evidence of the pertinent literature, further studies are strongly recommended, to better define potential benefits and limitations of this technique.

Microscissor DREZotomy for post brachial plexus avulsion neuralgia: A single center experience

INTRODUCTION

Brachial neuralgia is a dreaded sequelae which substantially impairs the quality of life in patients with brachial plexus avulsion (BPA) injuries. Dorsal Root Entry Zone (DREZ) lesioning of the cervical spinal cord is the most utilized procedure for alleviating this painful condition. In this study, we share a single center experience of surgically managing post BPA neuropathic pain. The efficacy, results and complications of the modified technique of DREZ, called the Microscissor DREZotomy (MDZ) are discussed along with the review of relevant literature.

METHODS

This retrospective analysis included all the patients undergoing MDZ for post BPA brachialgia over 5 years period (2012-2018) at our institution. The pain was quantified using the Numeric rating Scale (NRS) between 0 and 10 scale and was graded as 'Excellent' in patients with more than 75% pain relief, 'Good' with 50-75% relief, 'Fair' between 25% and 50% and 'Poor' if less than 25%.

RESULTS

A total of 56 patients underwent MDZ and a mean follow up of 32 months (range 18-69 months) available for 47 patients. Thirty three patients (70.4%) judged pain relief as Excellent, Five (10.6%) as Good, 3 (7%) as Fair and 6 (12%) having poor pain relief. Overall, in 38 (81%) patients long term analgesic effect (> 50%) was noted and 3 (7%) patients had more than 25% pain relief, making up an overall 41 (87%) of patients with some relief from pain.

CONCLUSION

MDZ is a safe, efficacious technique with good long term pain relief and quality of life. This technique entails utilization of routine surgical instruments and can be performed with ease even in resource limited settings.

Dorsal Root Entry Zone Lesioning for Brachial Plexus Avulsion: A Comprehensive Literature Review

Dorsal root entry zone (DREZ) lesioning is a neurosurgical procedure that aims to relieve severe neuropathic pain in patients with brachial plexus avulsion by selectively destroying nociceptive neural structures in the posterior cervical spinal cord. Since the introduction of the procedure over 4 decades ago, the DREZ lesioning technique has undergone numerous modifications, with a variety of center- and surgeon-dependent technical differences and patient outcomes. We have reviewed the literature to discuss reported methods of DREZ lesioning and outcomes.

DREZotomy in the treatment of deafferentation pain: review of results and analysis of predictive factors for success

BACKGROUND AND OBJECTIVES

The treatment of deafferentation pain by spinal DREZotomy is a proven therapeutic option in the literature. In recent years, use of DREZotomy has been relegated to second place due to the emergence of neuromodulation therapies. The objectives of this study are to demonstrate that DREZotomy continues to be an effective and safe treatment and to analyse predictive factors for success.

PATIENTS AND METHODS

A retrospective study was conducted of all patients treated in our department with spinal DREZotomy from 1998 to 2018. Bulbar DREZotomy procedures were excluded. A visual analogue scale (VAS) and the reduction of routine medication were used as outcome variables. Demographic, clinical and operative variables were analysed as predictive factors for success.

RESULTS

A total of 27 patients (51.9% female) with a mean age of 53.7 years underwent DREZotomy. The main cause of pain was brachial plexus injury (BPI) (55.6%) followed by neoplasms (18.5%). The mean time of pain evolution was 8.4 years with a mean intensity of 8.7 according to the VAS, even though 63% of the patients had previously received neurostimulation therapy. Favourable outcome (≥50% pain reduction in the VAS) was observed in 77.8% of patients during the postoperative period and remained in 59.3% of patients after 22 months average follow-up (mean reduction of 4.9 points). This allowed for a reduction in routine analgesic treatment in 70.4% of them. DREZotomy in BPI-related pain presented a significantly higher success rate (93%) than the other pathologies (41.7%) (p=.001). No association was observed between outcome and age, gender, DREZ technique, duration of pain or previous neurostimulation therapies. There were six neurological complications, four post-operative transient neurological deficits and two permanent deficits.

CONCLUSION

Dorsal root entry zone surgery is effective and safe for treating patients with deafferentation pain, especially after brachial plexus injury. It can be considered an alternative treatment after failed neurostimulation techniques for pain control. However, its indication should be considered as the first therapeutic option after medical therapy failure due to its good long-term results.

Efficacy and factors determining the outcome of dorsal root entry zone lesioning procedure (DREZotomy) in the treatment of intractable pain syndrome

BACKGROUND

Chronic pain is a disabling condition that adversely affects patient quality of life. The dorsal root entry zone lesioning procedure (DREZotomy) is a modality used to treat intractable pain caused by insults to neural structures. This study aimed to investigate the efficacy of and the factors that determine the outcome of microsurgical DREZotomy (MDT).

METHOD

All consecutive patients who underwent MDT for treatment of intractable pain during September 2008 to December 2016 were enrolled. Demographic data, clinical characteristics, intraoperative findings, and postoperative outcomes were analyzed.

RESULTS

The 40 included patients underwent MDT for relief of intractable pain caused by 27 brachial plexus injuries (BPIs), 6 spinal cord injuries, 3 neoplasms, and 4 other causes. A significant reduction in pain was observed post-MDT for both average (p < 0.001) and maximal pain (p < 0.001). Favorable outcome (≥50% pain reduction) was observed in 67.5% of patients, with the best outcome in BPI-related pain. In multivariate analysis, injury of the spinal nerve root (root avulsion or injury) was significantly associated with good average pain relief (OR, 5.8; 95% CI, 1.2-27.5; p = 0.026) and pain freedom (OR, 5.0; 95% CI, 1.12-22.30; p = 0.035). Electrical pain (OR, 6.49; 95% CI, 1.20-35.19; p = 0.030) and lower number of painful dermatomes (OR, 1.30; 95% CI, 1.01-1.67; p = 0.039) were significantly associated with good maximal pain relief.

CONCLUSIONS

MDT is an effective procedure for treatment of intractable pain in well-selected patients, particularly in cases with brachial plexus avulsion pain. Injury of the spinal nerve root (brachial plexus avulsion and cauda equina injury) was associated with good average pain relief and pain freedom, and electrical pain and lower number of painful dermatomes were associated with good maximal pain relief. The results are useful in the selection of candidates for DREZotomy and prediction of surgical outcome.

Correlation of preoperative MRI with the long-term outcomes of dorsal root entry zone lesioning for brachial plexus avulsion pain

OBJECT Lesioning of the dorsal root entry zone (DREZotomy) is an effective treatment for brachial plexus avulsion (BPA) pain. The role of preoperative assessment with MRI has been shown to be unreliable for determining affected levels; however, it may have a role in predicting pain outcomes. Here, DREZotomy outcomes are reviewed and preoperative MRI is examined as a possible prognostic factor. METHODS A retrospective review was performed of an institutional database of patients who had undergone brachial plexus DREZ procedures since 1995. Preoperative MRI was examined to assess damage to the DREZ or dorsal horn, as evidenced by avulsion of the DREZ or T2 hyperintensity within the spinal cord. Phone interviews were conducted to assess the long-term pain outcomes. RESULTS Between 1995 and 2012, 27 patients were found to have undergone cervical DREZ procedures for BPA. Of these, 15 had preoperative MR images of the cervical spine available for review. The outcomes were graded from 1 to 4 as poor (no significant relief), good (more than 50% pain relief), excellent (more than 75% pain relief), or pain free, respectively. Overall, DREZotomy was found to be a safe, efficacious, and durable procedure for relief of pain due to BPA. The initial success rate was 73%, which declined to 66% at a median follow-up time of 62.5 months. Damage to the DREZ or dorsal horn was significantly correlated with poorer outcomes (p = 0.02). The average outcomes in patients without MRI evidence of DREZ or dorsal horn damage was significantly higher than in patients with such damage (3.67 vs 1.75, t-test; p = 0.001). A longer duration of pain prior to operation was also a significant predictor of treatment success (p = 0.004). CONCLUSIONS Overall, the DREZotomy procedure has a 66% chance of achieving meaningful pain relief on long-term follow-up. Successful pain relief is associated with the lack of damage to the DREZ and dorsal horn on preoperative MRI.

Neuropathic pain after brachial plexus avulsion--central and peripheral mechanisms

REVIEW

The pain that commonly occurs after brachial plexus avulsion poses an additional burden on the quality of life of patients already impaired by motor, sensory and autonomic deficits. Evidence-based treatments for the pain associated with brachial plexus avulsion are scarce, thus frequently leaving the condition refractory to treatment with the standard methods used to manage neuropathic pain. Unfortunately, little is known about the pathophysiology of brachial plexus avulsion. Available evidence indicates that besides primary nerve root injury, central lesions related to the abrupt disconnection of nerve roots from the spinal cord may play an important role in the genesis of neuropathic pain in these patients and may explain in part its refractoriness to treatment.

CONCLUSIONS

The understanding of both central and peripheral mechanisms that contribute to the development of pain is of major importance in order to propose more effective treatments for brachial plexus avulsion-related pain. This review focuses on the current understanding about the occurrence of neuropathic pain in these patients and the role played by peripheral and central mechanisms that provides insights into its treatment. Pain after brachial plexus avulsion involves both peripheral and central components; thereby it is characterized as a mixed (central and peripheral) neuropathic pain syndrome.

Changes in Spontaneous Dorsal Horn Potentials after Dorsal Root Entry Zone Lesioning in Patients with Pain after Brachial Plexus Avulsion

OBJECTIVES: This study investigated spontaneous dorsal horn potentials in patients with pain after brachial plexus avulsion and determined the effect of dorsal root entry zone (DREZ) lesioning on these potentials and on pain levels. METHODS: Electrospinography (ESG) recordings were undertaken in seven patients using a noninvasive electrocorticography strip electrode. Measurements were taken from the DREZ on the intact side of the spinal cord before lesioning of the injured DREZ and from the injured DREZ before and after lesioning. RESULTS: DREZ lesioning had a significant positive effect on pain at 12 months postoperatively. At 15.0 Hz, the mean ESG power from the injured DREZ before lesioning was significantly higher than that from the intact DREZ. In addition, the mean ESG power from the injured DREZ after successful DREZ lesioning was significantly lower than that from the intact DREZ and that from the injured DREZ before lesioning. CONCLUSIONS: The ESG power from the injured DREZ increases in patients with pain after brachial plexus avulsion compared with that of the intact DREZ; this increase is reduced by successful DREZ lesioning.

Treatment of neuropathic deafferentation pain using DREZ lesions; long-term results

INTRODUCTION

Deafferentation pain secondary to spinal cord injury, brachial plexus avulsion and other peripheral nerve injuries is often refractory to conventional treatments. This study evaluates the long-term efficacy of spinal DREZ (Dorsal Root Entry Zone) lesions for the treatment of neuropathic pain syndromes caused by deafferentation.

PATIENTS AND METHODS

A series of 18 patients with refractory deafferentation pain treated with radiofrequency DREZ lesions is presented. The immediate and long-term efficacy was measured with the Visual Analogue Scale (VAS) before and after treatment, the patient's subjective evaluation, the percentage of patients returning to work and the reduction in pain medication.

RESULTS

Pain on the VAS significantly decreased from 8.6 preoperatively to 2.9 (p<.001) at discharge. Over the long-term, with a mean follow-up of 28 months (6-108) pain remained at 4.7 on the VAS (p<0.002). The percentage of patients with moderate to excellent pain relief was 77% at discharge and 68% at the last follow-up. Pain medication was reduced in 67% of the patients and 28% returned to work. The best results were obtained in patients with brachial plexus avulsion, with a significant long-term pain relief in all cases.

CONCLUSIONS

Radiofrequency DREZ lesion is an effective and safe treatment for refractory neuropathic pain caused by deafferentation.

High cervical spinal cord stimulation after failed dorsal root entry zone surgery for brachial plexus avulsion pain

BACKGROUND

Many patients had intractable pain after brachial plexus avulsion. This article describes a feasible method of high cervical SCS for a patient who failed in DREZ surgery to treat the pain.

CASE DESCRIPTION

A 70-year-old man had right brachial plexus avulsion after a car accident 15 years ago. He complained of chronic spontaneous pain over his right upper limb since then. Two DREZ surgeries failed to relieve the pain. The pain was successfully controlled by high cervical SCS.

CONCLUSION

Stimulating the high cervical spinal cord is effective for treating intractable pain after brachial plexus avulsion, which the DREZ surgery failed to relieve.

Destructive procedures for the treatment of nonmalignant pain: a structured literature review

OBJECT

Nonmalignant pain has been treated in the past century with ablative, or more appropriately, destructive procedures. Although individual outcomes for these procedures have previously been described in the literature, to the authors' knowledge this is the first comprehensive and systematic review on this topic.

METHODS

A US National Library of Medicine PubMed search was conducted for the following ablative procedures: cingulotomy, cordotomy, DREZ (also input as dorsal root entry zone), ganglionectomy, mesencephalotomy, myelotomy, neurotomy, rhizotomy, sympathectomy, thalamotomy, and tractotomy. Articles related to pain resulting from malignancy and those not in peer-reviewed journals were excluded. In reviewing pertinent articles, focus was placed on patient number, outcome, and follow-up.

RESULTS

A total of 146 articles was included in the review. The large majority of studies (131) constituted Class III evidence. Eleven Class I and 4 Class II studies were found, of which nearly all (13 of 15) evaluated radiofrequency rhizotomies for different pain origins, including lumbar facet syndrome, cervical facet pain, and Type I or typical trigeminal neuralgia. Overall, support for ablative procedures for nonmalignant pain is derived almost entirely from Class III evidence; despite a long history of use in neurosurgery, the evidence supporting destructive procedures for benign pain conditions remains limited.

CONCLUSIONS

Newly designed prospective standardized studies are required to define surgical indications and outcomes for these procedures, to provide more systematic review, and to advance the field.

Microsurgical anatomy of dorsal root entry zone of brachial plexus

The purpose of this study was to describe microsurgical anatomy of the dorsal root entry zone (DREZ) and provide an anatomic basis for the approach of DREZ lesion in treating radiculopathy of brachial plexus avulsion injuries. We studied 100 dorsal cervical roots and DREZ/posterior horn complexes in 20 adult cadavers. At each root level the following data were recorded: widths of laminectomy, numbers of posterior rootlets, angle of the inferior rootlets with the spinal cord, and distance from posterior median sulcus to posterolateral sulcus. On cross-sectional plane, the length and width of dorsal horn and the angle between longitudinal axis of dorsal horn and sagittal plane of spinal cord were measured. The results showed that the spinal cord segment and the entry of dorsal roots from C5 to T1 were exposed clearly after laminectomy from C4 to C7. The average number of roolets of C5-T1 roots was about 7.76 and C6 has the most. From up to down, the angle from the inferior rootlet to spinal cord of C5-T1 diminished gradually. The average distance from posterior median sulcus to posterolateral sulcus was 2.95 mm. The average length, width, and angle of posterior horn were 3.47 mm, 1.346 mm, and 35.9 degrees , respectively. Our study demonstrated that the spinous process and lamina of the C4 to C7 vertebrae should be resected to expose the C5-T1 when DREZ lesions are employed to treat pain after brachial plexus avulsion. The lesion-making apparatus should be inserted at an angle of 30 degrees -40 degrees , the width of lesion should be less than 1.2 mm and the lesion depth less than 3.1 mm.

Pain syndromes after missile-caused peripheral nerve lesions: part 1--clinical characteristics

OBJECTIVE

To report on the clinical characteristics of pain and factors influencing pain intensity in patients with missile-caused nerve injuries.

METHODS

The prospective study included 326 patients with clinically significant pain syndromes including complex regional pain syndrome Type II, deafferentation pain, reinnervation pain, and neuralgic pain. Diagnostic procedures were analyzed, factors influencing the pain intensity were identified, and the patients' characteristics, pain characteristics, and other clinical symptoms and signs were compared between different types of pain syndromes.

RESULTS

The rate of painful injuries ranged from 17.3 to 22.9% for mixed nerves and from 2.6 to 4.6% for motor nerves. Peripheral nerve block and sympathetic block were useful and safe adjuvant diagnostic procedures, obtaining pain relief in 66.7% of patients with neuralgic pain and in 90.1% of patients with complex regional pain syndrome Type II. Pain started 2.6 days after injury in patients with complex regional pain syndrome Type II and 11.9 days after injury in patients with painful nerve adhesions (analysis of variance, P < 0.001). Permanent pain was more frequent (79.1%) than paroxysmal pain, superficial pain was more frequent (55.2%) than deep pain, and burning pain was the most frequent pain descriptor (43.6%). Ten factors were found to significantly influence the pain intensity (binary logistic analysis), including three independent predictors (multivariate analysis): type of pain syndrome (P < 0.001), multiple nerve damage in the injury site (P = 0.022), and onset of pain in the first two days after injury (P = 0.031).

CONCLUSION

Pain syndromes after missile-caused nerve injury differ significantly regarding time of pain onset, pain characteristics, and other symptoms and signs. The type of pain syndrome, multiple nerve damage, and early onset of pain are independent predictors of initial pain intensity. Although medical history and physical examination are the main diagnostic keys, nerve exploration preceded by a nerve block and sympathetic block are safe and useful adjuvant diagnostic procedures.

Pain syndromes after missile-caused peripheral nerve lesions: part 2--treatment

OBJECTIVE

To analyze treatment procedures and treatment outcomes of painful missile-caused nerve injuries and factors influencing the outcome.

METHODS

The study included 326 patients with clinically significant pain syndromes, including complex regional pain syndrome Type II, deafferentation pain, reinnervation pain, and neuralgic pain. Treatment modalities included drug therapy, nerve surgery, sympatholysis, and dorsal root entry zone operation. Pain intensity was assessed before and after the treatment using a visual analog scale, and treatment outcome was defined as successful (pain relief >70%), fair (pain relief between 50 and 69%), or poor (pain relief <50%). The outcome was compared between different pain syndromes and different treatment modalities.

RESULTS

A successful outcome was achieved in 28.6% of patients with deafferentation pain, in 76.9% of patients with complex regional pain syndrome Type II, and in 87.9 to 100% of patients with other pain syndromes (P = 0.002). Each type of pain syndrome required a specific treatment algorithm, but average pain relief was similar for all definitive treatment modalities (range, 81-88%; P > 0.05). Ten factors were found to significantly influence the treatment outcome, but only three factors were independent predictors of a successful outcome: type of pain syndrome (P < 0.001), severity of nerve injury (P < 0.001), and absence of pain paroxysms (P = 0.03).

CONCLUSION

The treatment outcome of painful nerve injury depends on several factors, including the type of pain syndrome, severance of nerve injury, and absence of pain paroxysms. Drug therapy (carbamazepine, amitriptyline, or gabapentin) should be recommended, at least as a part of treatment, for patients with reinnervation pain, deafferentation pain, and complex regional pain syndrome Type II. Nerve surgery should be recommended for patients with posttraumatic neuralgia, either as the first treatment choice (acute nerve compression or intraneural foreign particles) or after unsuccessful pharmacological treatment (other causes of neuralgic pain).

Concepts of nerve regeneration and repair applied to brachial plexus reconstruction

Brachial plexus injury is a serious condition that usually affects young adults. Progress in brachial plexus repair is intimately related to peripheral nerve surgery, and depends on clinical and experimental studies. We review the rat brachial plexus as an experimental model, together with its behavioral evaluation. Techniques to repair nerves, such as neurolysis, nerve coaptation, nerve grafting, nerve transfer, fascicular transfer, direct muscle neurotization, and end-to-side neurorraphy, are discussed in light of the authors' experimental studies. Intradural repair of the brachial plexus by graft implants into the spinal cord and motor rootlet transfer offer new possibilities in brachial plexus reconstruction. The clinical experience of intradural repair is presented. Surgical planning in root rupture or avulsion is proposed. In total avulsion, the authors are in favor of the reconstruction of thoraco-brachial and abdomino-antebrachial grasping, and on the transfer of the brachialis muscle to the wrist extensors if it is reinnervated. Surgical treatment of painful conditions and new drugs are also discussed.

The trigeminal tract and nucleus procedures in treatment of atypical facial pain

BACKGROUND

Atypical facial pain (AFP) is a throbbing pain situated deep in the eye and malar region, often radiating to the ear, neck, and shoulders. The pain generally is not within any dermatomal or anatomical boundaries. Atypical facial pain is distinct from trigeminal neuralgia and its variants. Therefore, the treatment of AFP should be specified. There is also no consensus in the treatment of AFP. Two different treatment procedures on the trigeminal tract and nucleus in a series of cases with AFP are presented.

METHODS

Between 1989 and 2005, 17 patients with AFP, in whom previous therapies had failed, underwent computed tomography (CT)-guided percutaneous trigeminal tractotomy-nucleotomy (TR-NC). One patient with unfavorable response to TR-NC underwent trigeminal dorsal root entry zone (DREZ) operation.

RESULTS

In the series with AFP, pain relief was achieved in all of the 17 cases. TR-NC provided maximum to inadequate degrees of pain relief in 16 of 17 patients. Dorsal root entry zone operation provided partial relief in 1 case. Neither mortality nor serious permanent complication was observed in the series.

CONCLUSION

Neurosurgical procedures such as TR-NC or trigeminal DREZ operation may be effective in the treatment of intractable AFP. The primary choice of operation should be TR-NC because this procedure is minimally invasive. Trigeminal DREZ operation, which affects a larger spread area, may follow if TR-NC fails. The indications and procedure of choice should be individually tailored, depending on the type of pain, underlying pathology, and experience of the surgeon.

Microsurgical lesioning in the dorsal root entry zone for pain due to brachial plexus avulsion: a prospective series of 55 patients

OBJECT

Most patients with preganglionic lesions after brachial plexus injuries suffer pain that is hard to control through medication or neuromodulation. Lesioning in the dorsal root entry zone (DREZ) is undeniably effective. Fifty-five patients who had undergone the so-called microsurgical DREZotomy (MDT) procedure were studied with the two following objectives: 1) to describe the anatomical lesions observed during MDT in correlation with sensory deficits and pain features; and 2) to analyze the results in the 44 patients who were followed for more than 1 year (mean 6 years).

METHODS

The observed lesions were severe: 79.6% of ventral and 78.2% of dorsal roots from C5-T1 were impaired. Damage extended to all five roots in 42% of patients. Strong arachnoiditis was present in 38.2%, pseudomeningoceles in 31%, spinal cord distortion and/or atrophy in 49%, and abundant gliotic tissue and/or microcavitations within the dorsal horn at the avulsed segments in 36.4% of cases. Sensory deficit corresponded to the entire territory of the dorsal root lesions in 52% of patients, but was larger in 30% most certainly due to the associated extrarachidian lesions. At the last evaluation after MDT, 66% of patients showed excellent (total relief without medication) or good (total relief with medication) pain relief and 71% experienced an improvement in activity level.

CONCLUSIONS

Apart from other indications not addressed in this article, MDT can be performed to treat refractory pain due to brachial plexus avulsions. The long-term efficacy of this procedure strongly indicates that pain after brachial plexus avulsion originates from the deafferented (and gliotic) dorsal horn.

Ablative procedures for chronic pain

The advent of neuroaugmentative techniques has reduced the application of neuroablative procedures, especially as regards pain of functional origin. Although intracranial ablative procedures are now rarely performed, spinal ablative procedures, such as anterolateral cordotomies or midline myelotomies, remain important in the management of cancer pain. These procedures produce immediate and satisfactory pain relief with acceptable complication rates. An important future trend will be the application of radiosurgery guided by functional imaging (eg,fMRI, PET) to place such intracranial lesions as cingulotomies or medial thalamotomies.

Clinical and electrophysiological expression of deafferentation pain alleviated by dorsal root entry zone lesions in rats

OBJECT

The aims of this study were to construct an animal model of deafferentation of the spinal cord by brachial plexus avulsion and to analyze the effects of subsequent dorsal root entry zone (DREZ) lesions in this model. To this end, the authors measured the clinical and electrophysiological effects of total deafferentation of the cervical dorsal horn in rats and evaluated the clinical efficacy of cervical DREZ lesioning.

METHODS

Forty-three Sprague-Dawley rats were subjected to total deafferentation of the right cervical dorsal horn by performing a posterior rhizotomy from C-5 to T-1. The clinical effects of this deafferentation, namely self-directed mutilations consisting of scraping and/or ulceration of the forelimb skin or even autotomy of some forelimb digits, were then evaluated. As soon as some of these clinical signs of pain appeared, the authors performed a microsurgical DREZ rhizotomy ([MDR], microincision along the deafferented DREZ and dorsal horn). Before and after MDR, single-unit recordings were obtained in the deafferented dorsal horn and in the contralateral (healthy) side. The mean frequency of spontaneous discharge from the deafferented dorsal horn neurons was significantly higher than that from the healthy side (36.4 Hz compared with 17.9 Hz, p = 0.03). After deafferentation, 81.4% of the rats developed clinical signs corresponding to pain following posterior rhizotomy. Among these animals, scraping was observed in 85.7% of cases, ulceration (associated with edema) in 37.1%, and autotomy in 8.5%. These signs appeared a mean 5.7 weeks (range 1-12 weeks) after deafferentation. Thirteen rats benefited from an MDR; nine (69%) experienced a complete cure, that is, a total resolution of scraping or ulceration (a mean 4.6 weeks after MDR). In contrast, only one of 11 sham-operated animals showed signs of spontaneous recovery (p = 0.01).

CONCLUSIONS

These results emphasize the role of the spinal dorsal horn in the genesis of deafferentation pain and suggest that dorsal horn deafferentation by cervical posterior rhizotomy in the rat provides a reliable model of chronic pain due to brachial plexus avulsion and its suppression by MDR.