Lumbar (L4) Intradural Motor Nerve Root Repair Using Collagen Tube Following Excision of Schwannoma: First Case Report

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1 JKAU: Med. Sci., Vol. 19 No. 4, pp: (2012 A.D. / 1433 A.H.) DOI: /Med Lumbar (L4) Intradural Motor Nerve Root Repair Using Collagen Tube Following Excision of Schwannoma: First Case Report Bassam M. Addas, FRCSC, Rakan F. Bokhari, MBBS and Rajiv Midha 1, FRCSC Department of Surgery, Division of Neurosurgery, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia 1 Department of Clinical Neurosciences, Division of Neurosurgery and Hotchkiss Brain Institute, University of Calgary Calgary, Alberta, Canada addasneuro@yahoo.ca Abstract. A report on a 38-year-old woman presented with intradural L4 nerve sheath tumor, causing progressive low back and right leg pain for 5 months duration. Intra-operatively, the tumor was found to arise from the entire extent or at least a sizable portion of the L4 spinal motor nerve root. This was confirmed by intra-operative electromyography which demonstrated contraction of both tibialis anterior and vastus medialis. Microanatomical separation of the involved nerve and the tumor was not possible. The proximal and the distal end of the fascicle were resected with the tumor. Primary repair of the transected nerve was not possible. A collagen nerve tube measuring 1.5 cm was used to bridge the gap. At a 4 year follow up, the patient did not have any sensory complaints or functional impairment. This case illustrates the safety of using a nerve guidance tubes in repairing short injury gaps in cauda equina motor nerve roots. Keywords: Collagen tube, Nerve roots, Schwannoma. Correspondence & reprint request to: Dr. Bassam M. Addas P.O. Box 80215, Jeddah 21589, Saudi Arabia Accepted for publication: 10 June Received: 03 April

2 142 B.M. Addas et al. Introduction The use of collagen tube to bridge short gaps of the injured peripheral nerves is a well established technique with favorable outcome [1-3]. The utilization of these tubes helped to avoid donor site morbidity and saved operative time. The use of the collagen tubes has never been reported in the English literature. This case demonstrates the safety of using the collagen tubes in the intradural space when required. Case Report A 38-year-old female presented with progressive low back pain radiating to the right leg and medial shin for the last 5 months. Standing and going up the stairs was difficult, as well as getting off from the sitting position. She denied any bowel or bladder symptoms. On clinical examination, the right quadriceps muscle was found to be slightly weaker (Medical Research Council Grade 4+) than the left. The right thigh circumference was 2 cm less on the right compared to the left side. She demonstrated some allodynia in the mid and distal anterior thigh in response to light touch and hypoesthesia to pinprick in the same distribution, which did not correspond to a clear dermatomal pattern. Straight leg raising and femoral stretch test were negative. Magnetic resonance imaging (MRI) of the lumbosacral spine revealed a homogenously enhancing well demarcated intradural mass at the level of L2 vertebra consistent with a nerve sheath tumor. Intraoperative exploration, following L1-2 laminectomy, revealed that the intradural mass was arising from a single nerve element (Fig. 1A). Both proximal and distal ends of the involved nerve element could be identified. Evoked electromyography (with as little as 0.5 ma of stimulation of the entering and exiting nerve) showed activity of the right tibialis anterior and vastus medialis muscles, consistent with L4 motor nerve root involvement. Under the operating microscope, and despite attempted microdissection, it was not possible to differentiate the nerve element from the tumor mass as no planes were discernable. The decision was made to transect the proximal and the distal end with the tumor to ensure a complete tumor removal (Fig. 1B).

3 Lumbar (L4) Intradural Motor Nerve Root Repair Using Collagen Tube 143 Fig. 1A. Intra-operative photograph illustrates the tumor, along with both proximal and distal portions of the involved nerve elements. Fig. 1B. Photograph showing the resected tumor with portion of the proximal and distal ends of the involved nerve elements. Giving the size of the nerve element (Fig. 2A) and the robust response elicited from the electromyography (EMG) it was felt that the resected nerve root could have substantial contribution to L4 innervated muscles. The decision was therefore made to repair the transected nerve ends. With a 1.5 cm gap, it was clear that a graft or a tube was needed to bridge that gap (Fig. 2B). A 3 mm internal diameter, NeuraGen (Integra Life Sciences Service, Plainsboro NJ, USA) collagen tube,

4 144 B.M. Addas et al. trimmed to be 18 mm in length, was used so that both proximal and distal ends of the nerve could be inserted for a distance of 1-2 mm inside the tube. TISSEEL (Fibrin Sealant; Baxter International Inc., Deerfield, IL USA) was used to hold both ends of the nerve within the tube (in place) to complete the repair (Fig. 2C). Fig. 2A. Intra-operative photograph demonstrates the short gap between the nerve ends following resection of the tumor. Fig. 2B. Intra-operative photograph shows the in situ deployment of the collagen nerve tube to determine the length of tube needed for the repair.

5 Lumbar (L4) Intradural Motor Nerve Root Repair Using Collagen Tube 145 Fig. 2C. Intra-operative photograph shows the collagen tube after being glued to both proximal and distal ends of the transected L4 nerve root. Post-operatively the patient showed slight further limitation in her right quadriceps muscle testing (MRC Grade 4), which improved over the following few days, back to the level of her pre-operative examination. At 4 years follow up, the patient did not have any sensory complaints or functional impairment. The examination showed normal sensory and motor power. There were no signs or symptoms suggestive of intradural foreign body reaction. Discussion Repair of cauda equina motor nerve roots has been previously reported, either by direct suture technique or by using a graft repair. Lang and associates described intraspinal (S1-S3) nerve root repair following trauma with modest recovery of motor function, 2-3/5 by MRC scale [4]. The use of guidance tube for nerve repair is a well known technique that has been applied for minor and major peripheral nerves with a satisfactory degree of success [2-3]. Nerve guidance tubes for nerve repair have demonstrated similar results to a nerve graft repair when used to bridge gaps of 3 cm or less [3]. According to the author s knowledge, the repair of intradural spinal nerves using nerve guidance tubes has not been reported in the English literature. The nerves of the cauda equine, therefore present a unique

6 146 B.M. Addas et al. opportunity for using guidance tube repair, under appropriate circumstances. After they originate from the conus medullaris at the L1 lumbar level, the nerves of the cauda equina travel within the thecal sac for several centimeters before they acquire a dural sleeve and follow their usual course as they emerge through their respective foramen. When a tumor arises from these spinal nerve roots, it usually grows along the nerve element and if the distal intradural portion or the intra-foraminal portion is not involved by the tumor, a complete gross total resection can be easily achieved. Most of these intradural tumors arise from the sensory division of the nerve root; a division that can be sacrificed with accepted degree of morbidity, if any. Moreover, reconstructing these sensory roots is not useful as the injury is pre-ganglionic, hence, precluding successful central regeneration. When the tumor, albeit rarely, involve a motor division, an attempt should be made to save the non-involved portions of the motor division and only resect the involved nerve. However, intradural nerve roots lack perineurium, thus making it technically impossible to achieve sparing of a portion of the involved motor division if a gross total resection is the objective. In this circumstance, to avoid leaving residual tumor, transecting the proximal and distal ends of the nerve is required to assure a complete resection of the tumor. Although a small gap usually results following the resection, it is not small enough to allow a primary repair and a graft is needed to bridge the gap. Although the tumor size was 3 cm in length, the nerve gap following the tumor resection was only 1.5 cm, which may be due to the longstanding nature of this tumor that allowed stretching and elongation of the nerve of origin. In our case the involved element was sizable and showed a motor contribution to the tibialis anterior and vastus medialis muscles. Because it is very difficult to predict the post-operative neurological deficit that may arise following transecting such a nerve, it was elected to perform a nerve repair. The patient did not show any sustained worsened post-operative neurological deficit along the distribution of L4 myotome, and long-term follow-up suggested that the intradural repair of the L4 nerve achieved clinical success.

7 Lumbar (L4) Intradural Motor Nerve Root Repair Using Collagen Tube 147 In summary, the present case report documents the safety of using a nerve guidance tubes to repair short injury gaps in the intradural segments of spinal motor nerve roots. References [1] Dahlin LB, Lundborg G. Use of tubes in peripheral nerve repair. Neurosurg Clin N Am 2001; 12(2): [2] Dellon AL, Mackinnon SE. An alternative to the classical nerve graft for the management of the short nerve gap. Plast Reconstr Surg 1988; 82(5): [3] Weber RA, Breidenbach WC, Brown RE, Jabaley ME, Mass DP. A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans. Plast Reconstr Surg 2000; 106(5): [4] Lang EM, Borges J, Carlstedt T. Surgical management of lumbosacral plexus injuries. J Neurosurg (Spine) 2004; 1(1):

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9 Lumbar (L4) Intradural Motor Nerve Root Repair Using Collagen Tube 149.