Dorsal Root Entry Zone (DREZ) Lesioning for Brachial Neuralgia
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.299139
Source of Support: None, Conflict of Interest: None
Keywords: Brachial plexus avulsion, brachialgia, deafferentation pain, DREZ, microscissor, rhizotomy
In 1965, Ronald Melzack and Patrick Wall proposed the most influential theory of perception of pain, popularly known as “The Gate control theory of pain”. This theory highlighted the role of dorsal horns of the spinal cord in the perception of pain, which acts like a gate, which facilitates or inhibits the pain impulses from peripheral receptors to the brain. This theory provided the anatomical basis for lesioning the dorsal root entry zone area for abrogating various painful conditions. Sindou et al., (1972) performed DREZ lesioning for neuropathic pain related to Pancoast tumor infiltrating the brachial plexus, using bipolar coagulation for the first time., This was followed by multiple studies using different techniques like radiofrequency ablation (Nashold 1979), laser (both CO2 and Argon lasers) and ultrasonic ablation techniques have been described in the literature.,, We describe here a novel technique of DREZ lesioning, developed at our institution by the senior author (DA) using micro scissors exclusively., This technique called the “Microscissor DREZotomy” (MDZ) does not require any expensive or special neurosurgical equipment and can be easily executed in resource constraint setups with bare minimum microsurgical instruments.
Anatomical basis of DREZ lesioning
Each dorsal spinal rootlet is formed of a peripheral and a central segment. Pial ring (PR) which is located about 1 mm outside the entrance of the rootlet into the posterolateral sulcus (PLS) represents the junction between these two segments [Figure 1]. The small diameter A (myelinated) and C (nonmyelinated) fibers are responsible for the transmission of the nociceptive information.,
Lamination of the fibers
The nerve fibers are randomly arranged in the peripheral segment. At the PR level, the small nociceptive fibers preferentially lie in the ventrolateral location, and the large myotactic fibers tend to occupy the center and the large lemniscal fibers are located dorsomedially prior entering DH via the tract of lissauer (TL). There is a complete rearrangement of the fibers while they enter the TL. The large caliber myelinated fibers with inhibitory nociceptive effects lie in the dorsomedian position and small caliber fibers with excitatory nociceptive effects occupy the ventrolateral position, projecting onto the Rexed lamina 1 to V., Therefore, the TL is the key pathway that transmits nociceptive information at least two segments above the DREZ. Thus, it is important to understand that the lesioning should begin up to two segments cranial to involved dermatomal level [Figure 1].
This video article demonstrates the technique of MDZ in a 52-year-old gentleman with right brachial neuralgia following BPA injury.
The patient was operated under general anesthesia in a prone position and head fixed with a Mayfield clamp after ensuring padding of all the pressure points, abdomen free from compression, avoiding excessive neck flexion thereby maintaining optimum airway pressure. Right C3-T1 hemilaminectomy through a posterior midline cervical incision is performed. Care should be exercised to avoid violating the facet joint during the bone removal thereby preventing future spinal instability. In cases undergoing repeat DREZ following failed attempts at the first surgery, it is prudent to perform complete laminectomy for better anatomical orientation and avoiding inadvertent facetal injury. After opening the dura, sharp arachnoid dissection is performed releasing fibrosis and untethering of the nerve roots, with careful preservation of the radicular vessels. The PLS is often difficult to delineate in the absence of dorsal nerve roots along with the fibrosis, following BPA, that leads to the obliteration of the PLS. The abnormal rotation of the cord due to the fibrous strands also adds to the difficulty. Hence, an imaginary line drawn connecting the normal rostral and caudal roots forms the PLS; also, the tiny radicular vessels entering into the spinal cord act as a useful guide to the sulcus. Identification of the segmental level and differentiation of ventral and dorsal nerve roots sometimes may require the use of intraoperative neuromonitoring, although we do not use it regularly. The MDZ lesioning is performed extending two levels above the affected spinal segment till the lowermost intact normal root (see the Video 1 and audio transcript):
Meticulous hemostasis is of paramount importance after opening the PLS so as to avoid postoperative scarring and adhesions leading to recurrence of the neuralgia. A subcutaneous suction drain may be placed for at least 24 h to prevent postoperative wound hematoma/seroma formation. Cervical collar application is rarely recommended. However, it may be advised in patients undergoing repeat surgery with complete cervical laminectomy.
Video Link: https://www.youtube.com/watch?v=0-UFel1XoYY
Video timeline with audio transcript:
0:08 to 0:31 Introduction and technical details of the procedure: MDZ exclusively disrupts the second-order nociceptive fibers of the Rexed laminae-2 (substantia gelatinosa rolandi) located in the dorsal horn of the spinal cord. Topographically, it is located approximately 2 mm from the surface of the spinal dorsal column.
0:32 to 1:20 History and examination: A 55- year-old gentleman sustained RTA 2 years back following which he developed complete weakness of right upper limb (UL). Three months after the accident, he started complaining of right brachialgia. Pain was intermittent stabbing type, associated with tingling sensation and sleepless nights. Examination revealed LMN weakness involving right UL with the complete loss of sensation in right C5-8 & T1 distribution. EMG/NCV findings were suggestive of right pan brachial plexopathy.
1:21 to 1:38 Imaging: MRI cervical spine showing pseudomeningocele of the lower cervical nerve roots corresponding to the avulsed nerve roots.
1:39 to 1:46 Patient positioning and skin incision: Patient positioned prone and vertical midline skin incision is marked from C2 to T1.
1:47 to 2:12 Midline skin incision is deepened till the level of spinous processes. Unilateral muscles are detached from the lamina subperiosteally exposing right-sided hemilamina followed by C3–D1 hemilaminectomy using high-speed cutting drill.
2:13 to 2:23 Dura opened and tacked with silk sutures.
2:24 to 2:34 An intermediate segment of PLS without the roots is well appreciated in between the intact upper and lower nerve roots.
2:35 to 3:40 DREZ lesioning. Dorsal roots are retracted medially using a blunt hook, and an incision of 2–3 mm deep and oriented 35° medially and ventrally is given in the PLS using fine tip micro scissors (2 mm marked from its tip with a permanent marker) in the plane of cervical DH. With the help of microscissors, the PLS is opened up like a book up to the Rexed lamina II of the DH.
3:41 to 3:48 Meticulous hemostasis is followed by watertight dural closure. Wound closure done in layers. Postoperative period was uneventful with excellent pain relief.
This patient had complete pain relief in the postoperative period and was off medications postoperatively at 1 year follow up. At our institution, 58 patients underwent MDZ for post BPA neuralgia. Significant pain relief (defined as >50% pain relief) was achieved in 81% at a mean follow-up of 31 months. Most studies have reported 15–30% complication rates following DREZ lesioning with paresthesias as the most frequently encountered complication.,,,,,, In our experience, complications were noted in 18% of cases which included both sensory-motor disturbances, although 6% patients recovered from transient sensory symptoms. CSF leak in one patient resolved with lumbar drain without any sequelae.
DREZ lesioning is the most effective method of alleviating the intractable post BPA neuralgia irrespective of the technique used. These patients often suffer from depression and suicidal tendencies due to the extreme pain. Appropriate patient selection and preoperative counseling is of paramount importance. It is seen that patients suffering from intermittent sharp shooting type of pain have excellent relief following DREZ. Surgical failures can be often attributed to inadequate and incomplete lesioning requiring repeat surgery. Late recurrences following an initial pain relief do occur, mandating prolonged follow up. It might be necessary to have assisted at least five cases prior to performing DREZ independently, in order to shorten the learning curve. MDZ is a new addition to the existing techniques in the armamentarium of the neurosurgeon.
Microscissor DREZotomy represents an elegant technique with equal efficacy and better safety profile. This technique can be performed even in peripheral centers with limited resources using minimum and basic neurosurgical equipment.
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