Effects of dorsal root entry zone lesion on spinal cord potentials evoked by segmental, ascending and descending volleys

Tight adhesions after spinal cord stimulation observed during dorsal root entry zone lesioning for pain after spinal root avulsion: illustrative cases

BACKGROUND

Patients often experience strong shooting pains after spinal root avulsion. The efficacy of spinal cord stimulation (SCS) for this type of pain is inconsistent; however, dorsal root entry zone (DREZ) lesioning (DREZ-lesion) has often proven to be an effective treatment modality. The authors report two cases in which DREZ-lesion was performed to treat pain after spinal root avulsion after implantation of SCS, but the operations were challenging due to strong adhesions.

OBSERVATIONS

The authors present two cases of patients with pain after spinal root avulsion in whom SCS implantation was only temporarily effective. Patients complained of persistent and paroxysmal shooting pains in the upper extremities. SCS removal and DREZ-lesion were performed, but adhesions in the epidural and subdural space contacting the leads were strong, making it difficult to expose the DREZ.

LESSONS

Although adhesions around the spinal cord can be caused by trauma, the authors believe that in these cases, the adhesions could have been caused by the SCS leads. There are few previous reports confirming the efficacy of SCS in treating pain after spinal root avulsion; therefore, caution is required when considering SCS implantation.

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.

Dorsal root entry zone approach in ventral and eccentric intramedullary tumors: A report of 2 cases

Intramedullary tumors constitute 2-4% of all the tumors affecting the central nervous system. They include low-grade astrocytomas and ependymomas in majority. Earlier, only biopsy or decompression used to be the best available options for these tumors, but with the upcoming technology and newer techniques, gross total excision with the aim of achieving complete removal has been the preferred treatment for these tumors. Usually, nearly all intramedullary tumors are approached from posterior midline myelotomy as this is the safest corridor to approach under neurophysiologic monitoring. But sometimes, if the tumor is exophytic, eccentric, or ventral to the cord, other routes of access may also be useful. These approaches are less frequently used these days and actually may be found useful in certain cases. Hence, they should not be termed “obsolete” and must be kept in mind for tumors in specific location. We describe a similar less commonly used dorsal root entry zone approach for near total excision of ventral and eccentric cervical pilocytic astrocytomas in two patients.

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.

Electrophysiologic and clinical data support the use of dorsal root entry zone myelotomy in syringosubarachnoid shunting for syringomyelia

BACKGROUND

The objectives of this study were to correlate preoperative changes in SEPs with clinical sensory dysfunction and to establish their importance in planning the microsurgical approach, either by DM myelotomy or by DREZ myelotomy, for patients with syringomyelia.

METHODS

In addition to conducting clinical sensory examination, we evaluated the N13 potential after median nerve stimulation and CPs after tibial nerve stimulation intraoperatively before performing myelotomy on patients with syringomyelia (N = 14).

RESULTS

Eleven patients with intact DS presented with unilateral PTD, and 9 had distressing unilateral dermatomal pain. Deep sensibility was affected in 3 patients (bilaterally in 1 patient) without PTD. Patients with PTD were likely to have spontaneous pain (P = .005). A significant correlation between preoperative PTD and the absence of the N13 potential was demonstrated on the right (P = .015) and left (P = .004) sides. In patients with PTD, DREZ myelotomy on the symptomatic side is suggested as the treatment of choice, whereas DM myelotomy might be superior in patients without PTD.

CONCLUSIONS

Absence of pain or temperature sensation in patients with syringomyelia is usually accompanied by same-sided loss of the N13 potential, suggesting damage to the DH gray matter. Deep sensibility is typically normal, and DREZ myelotomy with preservation of DCs is proposed as the treatment of choice. Conducted potentials are usually distorted in patients with normal pain or temperature sensation and affected vibration and posture sensation, suggesting damage to DCs and making DM myelotomy the treatment of choice. Electrophysiologic and clinical data support the use of DREZ myelotomy in syringosubarachnoid shunting for syringomyelia in patients whose DCs have an intact function.

Single-unit analysis of the spinal dorsal horn in patients with neuropathic pain

Despite the key role played by the dorsal horn of the spinal cord in pain modulation, single-unit recordings have only been performed very rarely in this structure in humans. The authors report the results of a statistical analysis of 64 unit recordings from the human dorsal horn. The recordings were done in three groups of patients: patients with deafferentation pain resulting from brachial plexus avulsion, patients with neuropathic pain resulting from peripheral nerve injury, and patients with pain resulting from disabling spasticity. The patterns of neuronal activities were compared among these three groups. Nineteen neurons were recorded in the dorsal horns of five patients undergoing DREZotomy for a persistent pain syndrome resulting from peripheral nerve injury (i.e., nondeafferented dorsal horns), 31 dorsal horn neurons were recorded in nine patients undergoing DREZotomy for a persistent pain syndrome resulting from brachial plexus avulsion (i.e., deafferented dorsal horns), and 14 neurons were recorded in eight patients undergoing DREZotomy for disabling spasticity. These groups were compared in terms of mean frequency, coefficient of variation of the discharge, other properties of the neuronal discharge studied by the nonparametric test of Wald-Wolfowitz, and the possible presence of bursts. The coefficient of variation tended to be higher in the deafferented dorsal horn group than in the other two groups. Two neurons displaying burst activity could be recorded, both of which belonged to the deafferented dorsal horn group. A significant difference was found in term of neuronal behavior between the peripheral nerve trauma group and the other groups: The brachial plexus avulsion and disabling spasticity groups were very similar, including various types of neuronal behavior, whereas the peripheral nerve lesion group included mostly neurons with "nonrandom" patterns of discharge (i.e., with serial dependency of interspike intervals).

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.

Treatment of Refractory Pain after Brachial Plexus Avulsion with Dorsal Root Entry Zone Lesions

OBJECTIVE

Significant numbers of patients experience intractable pain after brachial plexus root avulsions. Medications and surgical procedures such as amputation of the limb are often not successful in pain treatment.

METHODS

Forty-seven patients with intractable pain after traumatic cervical root avulsions were treated with dorsal root entry zone coagulation between 1980 and 1998. The dorsal root entry zone coagulation procedure was performed 4 months to 12 years after the trauma, and patients were monitored for up to 18 years (average follow-up period, 14 yr).

RESULTS

Immediately after surgery, 75% of patients experienced significant pain reduction; this value was reduced to 63% during long-term follow-up monitoring. Nine patients experienced major complications, including subdural hematomas (n = 2) and motor weakness of the lower limb (n = 7). Improved coagulation electrodes with thermistors that could produce smaller and more-accurate lesion sizes, which were introduced in 1989, significantly reduced the number of complications.

CONCLUSION

Central deafferentation pain that persists and becomes intractable among patients with traumatic cervical root avulsions has been difficult to treat in the past. Long-term follow-up monitoring of patients who underwent the dorsal root entry zone coagulation procedure in the cervical cord indicated that long-lasting satisfactory relief is possible for the majority of individuals, with acceptable morbidity rates.

Sympathectomy for causalgia: experience with military injuries

BACKGROUND

Causalgia is a rare disease in civilian practice, and most reports regarding causalgia in the literature are from major extended wars. To increase awareness of this syndrome, our wartime experience with this disease is presented.

METHODS

The charts of patients with causalgia referred to two university hospitals for treatment from 1985 to 1989 were retrospectively studied. Characteristics of the cause, clinical manifestations, and the response to therapy were evaluated.

RESULTS

Among 1,564 patients with peripheral nerve injuries, there were 54 cases (3.4%) of causalgia. All of the patients, except five, were injured in battle by high-velocity bullets or missiles. Upper extremities were involved in 28 patients (52 %) and lower extremities in 26 patients (48%). The most common presenting symptoms were as follows: burning pain, 100%; wet extremity, 100%; cold extremity, 93%; sensitivity to cold, 89%; paresthesia, 78%; and color changes in the extremities, 55%. In 48 patients (89%), pain was relieved by sympathetic block (3 patients had permanent cure). Six patients had no response to the blocks (11%). Of 45 patients who had temporary relief, all underwent sympathectomy. All of these patients had complete relief of symptoms in the immediate postoperative period and for follow-up from 1 to 6 years.

CONCLUSION

Causalgia is essentially a war casualty disease. The condition is associated with burning pain, hyperesthesia, and symptoms of sympathetic overactivity. Sympathectomy is effective and the treatment of choice, particularly for patients who respond temporarily to sympathetic blocks.