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.     

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.     

Microsurgical junctional DREZ coagulation for treatment of deafferentation pain syndromes

BACKGROUND: In the treatment of intractable deafferentation pain, different procedures in the DREZ have proved most effective. For most of the spot-like techniques special equipment is mandatory. In this study the technique and the results of junctional DREZ coagulation for treatment of different pain syndromes with the help of bipolar forceps is presented. METHODS: In 40 patients with intractable deafferentation pain syndromes a junctional DREZ coagulation lesion along the entire dorsolateral fissure of the involved spinal cord segments was made using bipolar forceps. Etiologies of the pain included avulsion of the brachial plexus (21 cases), postherpetic pain (4 cases), phantom pain (3 cases), peripheral nerve injury (3 cases), reflex sympathetic dystrophy (2 cases), spinal cord transsection (1 case), and syringomyelia (6 cases). RESULTS: Of 21 patients who underwent junctional DREZ surgery for pain because of brachial plexus avulsion 10 (47.6%) had complete, 7 (33.3%) excellent, 3 (14.3%) good, and 1 (4.7%) fair pain relief (follow-up 20 to 120 months). In the group of 19 patients (follow-up 6 to 84 months) with pain syndromes other than postavulsion pain we achieved excellent results in 10 cases (52.6%), good in 8 (42.1%) and no pain relief in 1 case (5.3%). Transient sensory neurological disturbances lasting up to 8 weeks were observed in 6 (15%) cases; permanent sensory and motor deficit in 1 (2.5%) case. CONCLUSIONS: Clinical results of junctional coagulation DREZ lesion for the treatment of deafferentation pain syndromes are promising. There is no need for special equipment for creating DREZ lesions. The lesions are precisely placed with only a bipolar electrode. Postoperative complications are rare and transient. We believe that the junctional coagulation includes the entire dorsolateral sulcus and DREZ structures important for deafferentation pain.     

Conus medullaris nerve root avulsions

The association of avulsive lesions and pain has been well established in avulsions of the brachial plexus from the cervical spinal cord, but avulsive lesions of the conus medullaris have not previously been recognized or documented by direct observation. Six patients with intractable lower-extremity pain due to avulsion of nerve roots from the conus medullaris were treated by thoracolumbar laminectomy and dorsal root entry zone (DREZ) lesions. Patients with avulsion of lumbosacral roots from the conus medullaris have a characteristic clinical presentation. They are usually young men who, as a result of a motorcycle accident, have suffered multiple pelvic or long-bone fractures or traumatic amputation of part of the lower extremity. Early in their course there is pain not directly attributable to the injured part. The pain is described as intense and burning, with episodic radiation and electric shock-like sensations in the injured or phantom limb. If the leg is intact, there is usually a dermatomal pattern to the distribution of the pain and neurological deficit. A myelogram often reveals a traumatic pseudomeningocele similar to those seen in the cervical region after avulsion of the brachial plexus. Surgical exploration of the conus medullaris usually reveals the extent of nerve root avulsion, and an appropriate DREZ operation can be performed.     

Dorsal root entry zone lesions for post-amputation pain

Chronic pain following an amputation may involve the stump, the phantom limb, or both. Operations such as rhizotomy, cordotomy, stump revision, and dorsal column stimulation have been unsuccessful in treating this condition. This study evaluates the effectiveness of dorsal root entry zone (DREZ) coagulation for this pain problem. The authors studied 22 patients with amputations due to trauma, gangrene, or cancer. All developed post-amputation pain, underwent a DREZ procedure, and were followed from 6 months to 4 years after surgery. Overall, only eight (36%) of these 22 patients had pain relief. However, good results were obtained in six (67%) of nine patients with phantom pain alone, and in five (83%) of six patients with traumatic amputations associated with root avulsion. Poor results were obtained in patients with both phantom and stump pain, or stump pain alone. The DREZ procedure has a limited, but definite, place in the treatment of post-amputation pain.     

Dorsal root entry zone lesions for the treatment of brachial plexus avulsion injuries: a follow-up study

Dorsal root entry zone (DREZ) lesions have been shown to yield short term relief from the pain associated with a brachial plexus avulsion injury. Because of the propensity of pain to recur after neuroablative procedures, 39 patients with pain after a brachial plexus avulsion injury were observed for 14 months to 10 years after DREZ lesions were made. Fifty-four per cent of these patients were afforded good pain relief. Of 21 patients who had multiple small lesions made within the DREZ, 15 (72%) were afforded good pain relief.     

Thermocoagulation of the dorsal root entry zone for the treatment of intractable pain

The authors report the results of DREZ thermocoagulation in 35 patients since March 1980. This technique was applied not only in patients with deafferentation pain after brachial plexus avulsion, but also for postamputation phantom limb pain and pain caused by injury to the spine and spinal cord, by peripheral nerve lesions, and by multiple sclerosis. Independent of etiology, the duration of the pain syndrome, and the quality and projection of the pain, the overall results have been satisfactory and long-lasting.     

Is the substantia gelatinosa the target in dorsal root entry zone lesions? An autopsy report

The autopsy findings in a patient who died from a massive myocardial infarction 5 days after a cervical DREZ lesion for deafferentation pain are reported. The trauma had caused a substantial defect involving the ipsilateral Lissauer's tract and the substantia gelatinosa, as well as more medial parts of the posterior horn. The positive effect of the radiofrequency coagulation must have been caused by a lesion outside Lissauer's tract and the substantia gelatinosa.     

Current status of the DREZ operation: 1984

The DREZ operation was introduced in 1976 as a method to control deafferentation pain associated with brachial plexus injury. Since then, 250 DREZ operations have been done at Duke Medical Center. At present, the best results of pain relief occur in brachial and lumbosacral root avulsions, paraplegia, and postherpetic pain. Post-DREZ complications have been reduced by the introduction of new lesion techniques, including the recent use of the laser. The neural basis of deafferentation pain is still not solved, nor is the therapeutic effect of the DREZ lesion known.     

Microsurgical DREZ-lesion in the treatment of deafferentation pain

The lesion of the dorsal root entry zone (DREZL) of the spinal cord, recently introduced by Nashold and performed with radiofrequency or with laser, may be carried out with a microsurgical technique. Since 1978 up 1982 we have treated a series of 12 patients suffering from Pancoast's syndrome with a C8-T2 selective posterior rhizotomy (SPR). It has been observed that every deafferentative aspect of the pain was completely relieved. Such effect on the deafferentative aspect of the pain was most probably due to a lesion on the perforating vessels feeding the posterior grey horn. The lesion of this structure was therefore ischemic and this operation had to be indicate for the treatment of such pain. A series of 8 patients, suffering from cancer pain projected to anaesthetic areas, and 2 patients with benign post-thoracotomy pain, underwent to microsurgical DREZ lesion. The relief from pain was complete and no complications concerning pyramidal or posterior pathways involvement was observed. Preliminary good results suggest that a more selective lesion is possible with the microsurgical DREZ. It should be interesting a comparison between more large series of microsurgical DREZL and the more tested radiofrequency lesion.     

Subpial spinal evoked potentials in patients undergoing junctional dorsal root entry zone coagulation for pain relief

Summary Seven patients with complete avulsion of the brachial plexus underwent junctional coagulation lesions of the dorsal root entry zone (DREZ) for relief of intractable pain in the paralyzed arm. Intra-operative monitoring by recording spinal cord somatosensory evoked potentials (SEP) resulting from tibial nerve stimulation was done using subpial recording electrodes situated dorsal to the posterior median sulcus at the C4 and T2 segment. SEP on the normal side showed an initial positive wave and two negative waves followed by a group of high frequency waves of relatively high amplitude which continued into high frequency, low amplitude potentials. The conduction velocity of the fastest spinal evoked potential components were, on average, 86 m/s. Recordings from the side of avulsion revealed a steep positive potential of high amplitude which appeared in five patients prior to the creation of the DREZ lesion. This effect was assumed to be secondary to spinal cord damage caused by avulsion. During the DREZ coagulation the SEP from the unaffected side did not change. On the side of DREZ coagulation the velocity of the fastest fibres decreased. Four patients reported sensory deficits after the operation, which were transient in three. In one of these patients, the first two negative potentials disappeared. In the fourth patient, who had permanent sensory deficits, the positive steep potential appeared after generation of the lesion. Our results point to the usefulness of the subpial SEPs monitoring during microneurosurgical procedures on the spinal cord to provide further insight into evoked electrical activity of the normal and injured spinal cord, and to minimize post-operative neurological morbidity.     

Selective posterior rhizotomy at the posterior radiculomedullary junction in the treatment of hyperspasticity and pain in the lower limbs

The authors report a series of 53 bedridden patients having harmful spasticity in one (6) or both (47) lower limb(s) and treated with selective posterior rhizotomy (SPR) in the dorsal root entry zone (DREZ). This severe spasticity was associated with irreducible flexion contracture in 49 cases and hyperextension in 3 others. 37 of these patients also had painful manifestations. The method was introduced in 1972 on the basis of anatomical studies of the DREZ in humans which showed a topographical segregation of the afferent roots according to their anatomico-functional destinations. The technique consists of a 2 mm deep DREZ microsurgical cut directed at a 45 degree angle into the posterior lateral sulcus just ventral to DREZ and Lissauer's tract of the spinal cord. The procedure was carried out at each sensory rootlet considered to be responsible for the harmful spasticity and pain. SPR interrupts selectively the lateral nociceptive and central myotactic afferent fibers curving toward Lissauer's tract and the anterior spinal cord, while sparing most of the medial lemniscal fibers curving toward the dorsal columns, as well as the fibers of the inhibitory circuitry of Lissauer's tract and dorsal horn. The results were evaluated after a 1 to 14 year follow-up. Mild to severe complications occurred in 25 patients (47.1%) and were responsible for death in 5 (9.4%). Both spasticity and spasm were significantly decreased or completely eliminated in 75% and 88.2% respectively; when present, pain was relieved without a total suppression of sensation in 91.6%. These benefits-combined with complementary orthopedic surgery in 23 patients--resulted in either a complete resolution or marked reduction of the abnormal postures and articular limitations (85.2% complete and 96.75 marked reduction). Because of the extreme severity of the pre-operative neurological deficits in almost all the patients in this series, surgery improved voluntary movements with a significant functional benefit in only 5 cases and vesico-sphincter function in none. Thanks to its valuable effects on hyperspasticity and pain, SPR in the DREZ made it possible for these very disable patients to be more comfortable in bed and wheel-chair and it allowed effective nursing and kinesitherapy to be resumed.     

Dorsal root entry zone lesions for the control of deafferentation pain: experiences in ten patients

Experiences with radiofrequency lesions of the dorsal root entry zone in 10 patients are reported. All of these patients suffered from central (deafferentation) pain. The early postoperative results were poor in the 2 patients with traumatic paraplegia and good in all 8 patients with pain in the cervical segments. Two patients treated with cervical DREZ lesions died. In 2 of the remaining 6 patients with cervical lesions, pain recurred. Four had a good result up to 30 months after operation.     

Dorsal root entry zone lesions (Nashold's procedure) in brachial plexus avulsion

Dorsal root entry zone coagulation (DREZ) lesions for pain were made in 41 patients at the National Hospitals during 1980 through 1983. In 34 patients the operation was an attempt to relieve pain due to avulsion of the brachial plexus. Of these patients, 95% were male and 91% had received their injury in road traffic accidents. The follow-up period is 4 to 44 months. Pain relief was good in 62%, fair in 24%, and poor in 14%. Postoperative motor or sensory changes occurred in 50% of the patients, but these were significant in only 12%. In later patients in this series, pre-, peri-, and postoperative monitoring of somatosensory evoked potentials was used. Evoked potential monitoring indicated subclinical posterior column damage ipsilateral to avulsion before DREZ lesion making in about 50% of the cases; in some cases, postoperative changes were detected.     

Results of DREZ coagulations for pain related to plexus lesions,spinal cord injuries and postherpetic neuralgia

Summary The results of 58 dorsal root entry zone (DREZ) thermocoagulation procedures in 51 patients are reported. The postoperative analgesic effect was judged by the patients as being good (more than 75% pain reduction), fair (25–75% pain reduction) or poor (less than 25% pain reduction). Of the 14 patients who underwent surgery for pain due to cervical root avulsion, 10 (77%) had permanently good (8) or fair (2) pain relief after a mean follow up period of 76 months, another 2 (15%) experienced recurrence to the pre-operative level (initially 1 good, 1 fair) after more than 2 and 4 years, respectively. Twenty two paraplegics were operated upon, 3 of whom twice, for intractable pain. After a mean observation time of 54 months, continuing pain relief was reported by 12 (55%) patients (11 good, 1 fair), and one (initially fair) had recurrent pain after 8 months. All 3 (early) re-operations remain successful for an average period of 75 months. Poor results were seen especially in cases of associated spinal cord cysts (5 out of 7), despite combined drainage, and in patients with diffuse pain distribution (5 out of 6). Continuous marked improvement for longer periods (mean follow up: 52 months) after DREZ lesions was reported only by 2 out of 10 patients with postherpetic neuralgia (12 procedures) and by 1 out of 5 with painful states due to radiation-induced brachial plexopathy (2), previous surgery (2) and malignant tumour infiltration of the brachial plexus (1). Three patients died postoperatively due to acute cardiac failure (2) and pulmonary embolism (1). Major complications, especially permanent gait disturbances were observed in 6 patients (12%) following primary procedures and in 2 out of 7 patients after re-operations, most of them suffering from postherpetic neuralgia. Minor neurological deficits were noted in 9 cases (18%). DREZ lesions revealed to be an effective procedure in patients with pain related to root avulsion and paraplegia. In contrast, it seems to be less successful for painful states due to other plexus lesions or postherpetic neuralgia.     

Pain relief from dorsal root entry zone lesions made with argon and carbon dioxide microsurgical lasers

Argon and carbon dioxide microsurgical lasers were used to produce lesions in the dorsal root entry zone (DREZ) experimentally in six cats and surgically in 21 patients who had denervation pain syndromes. The technique of producing lesions, the histological and physiological changes seen in the cat spinal cord, and the results of treatment in the clinical series are discussed. Lesions were produced within the DREZ without new involvement of the dorsal column system or corticospinal tract in all but one patient. Based on their subjective evaluation, two-thirds of the patients were relieved of more than 50% of their preoperative pain. These experimental results and clinical experience suggest that the argon and carbon dioxide lasers effectively produce localized microsurgical lesions in the DREZ. The concept that an abnormality involving either neurons in the substantia gelatinosa or internuncial fibers in Lissauer's tract is responsible for pain in patients with primary sensory nerve deafferentation is discussed.     

Pain following traumatic lesions of the brachial plexus (radicular avulsions and truncular lesions)

Pain in avulsions lesions of the brachial plexus is related with deafferentation; experimental studies demonstrate that spontaneous discharges can be recorded with micro electrodes in the dorsal horn, after division of the dorsal roots. These discharges ("firing") are related with the loss of control of the inhibitory effects of the large caliber sensory fibers. This pathophysiological concept drawn from the Melzack and Wall's theory (gate control) allows a good meaning of the paradoxical results observed after neurotization (via accessory or intercostal nerves), namely immediate relief of pain, observed in several cases after surgery. This theory helps to explain the efficiency of the neurostimulation techniques (by inhibition of the "firing") and of the technique of "dorsal root entry zone coagulation" in the avulsed area, on the spinal cord, by direct destruction of the hyperactive cells in the posterior horn. These technical advances and early return to work and to community offer the best prospect of relief of pain. Incidence of intractable pain problem is less than 10% after 10 years.     

Trigeminal nucleus caudalis dorsal root entry zone: a new surgical approach.

New radiofrequency lesion dorsal root entry zone (DREZ) electrodes for relief of facial pain were designed based on a neuroanatomic study in man of the trigeminal nucleus caudalis at the cervicomedullary junction. The human brainstems of 3 normal postmortem specimens were sectioned with measurements and relationships of the trigeminal nucleus caudalis, segmental tracts, spinocerebellar tracts and dorsal columns. Two right-angle DREZ electrodes were made by Radionics for producing DREZ lesions in the trigeminal nucleus caudalis to treat deafferentation facial pain.     

Biomechanical characteristics of spinal cord tissue--basis for the development of modifications of the DREZ (dorsal root entry zone) operation

Mechanical properties of the spinal cord tissue--biological basis for the development of the modality of the DREZ surgery lesioning technique Succesful treatment of the chronic neurogenic pain of spinal cord and cauda equina injury origin remains a significant management problem. The mechanism of this pain phenomenon has been shown to be related to neurochemical changes that lead to the state of hypereactivity of the second order dorsal horn neurons. The DREZ surgery (Dorsal Root Entry Zone lesion), designed to destroy anatomy structures involved in pain generating thus interrupting the neurogenic pain mechanism, as a causative procedure in treating this chronic pain, has been performed by using different technical modalities: Radiofrequency (RF) coagulation technic, Laser, Ultrasound and Microsurgical DREZotomy technic. The purpose of the study was to assess the possibility for the establishment of the lesioning technic based on the natural difference in the mechanical properties between the white and gray cord substance. We experimentally deteminated mechanical properties of the human cadaveric cord white versus gray tissue for the purpose of testing possibility of selective suction of the dorsal horn gray substance as a DREZ lesioning procedure. Based on the fact of the difference in tissue elasticity between white and gray cord substance we established a new and simple DREZ surgical lesioning technique that was tested on cadaver cord. For the purpose of testing and comparing the size and shape of the DREZ lesion axchieved the DREZ surgery has been performed on cadaver cord by employing selective dorsal horn suction as a lesioning method. After the procedure cadaver cord underwent histological fixation and analysis of the DREZ lesions achieved. Our result revealed that the white cord substance with longitudinal fiber structure had four time higher dynamical viscosity than gray substance of local neuronal network structure (150 PaS versus 37.5 PaS) that provided possibility for the safe and selective suction of the gray substance of the dorsal horn. Technic includes incision of the dorsolateral sulcus according to Sindous Microsurgical DREZotomy technic than suction under visual control of the dorsal horn gray matter using succer adopted from the lumbar puncture nidle. Operative experimental testing and hystological analysis confirmed expected size and shape of the DREZ lesion performed by dorsal horn suction as DREZ lesioning technique. The utility, selectivity and safety of this technic has been provided by the natural mechanical properties of the cord tissue itself. Application of the Dorsal horn suction as a DREZ lesioning in humans confirmed this technic as a safe and reliable DREZ lesioning method.