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Spinal Accessory nerve reconstruction using autologous sural nerve graft

    Overview

    Learn the Spinal Accessory nerve reconstruction using autologous sural nerve graft surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Spinal Accessory nerve reconstruction using autologous sural nerve graft surgical procedure.
    The spinal accessory nerve is the XIth cranial nerve and it traverses the posterior triangle where it is prone to injury in neck dissections for lymph node biopsies. Superiorly the nerve passes from the junction of the upper 1/3 and distal 2/3 of the sternocleidomastoid to the junction of the upper 2/3 and lower 1/3 of the trapezius in the lateral and posterior aspect of the posterior triangle. The nerve supplies the sternocleidomastoid then as it travels laterally it branches supplying a lateral branch to the upper lateral trapezius and a medial branch which passes posteriorly and inferiorly to supply the medial and lower trapezius. The XIth nerve passes to the neck in close proximity to the cervical plexus nerves, the supraclavicular nerves and the great auricular nerve. These sensory nerves may be affected in an iatrogenous injury following a neck dissection and the patient may present with dysaesthesia, hypoaesthesia or anaesthesia in the clavicle area and over the ipsilateral ear lobe. The examination should include looking for a Tinel’s sign at the point of potential injury.
    Damage to the XIth nerve distal to the sternocleidomastoid branch results in wasting and paralysis of the ipsilateral trapezius with drooping of the shoulder and loss of the definition of the posterior boundary of the posterior triangle resulting in neck and shoulder asymmetry.

    Indications

    Indications:
    The indications for surgical exploration are paralysis of the trapezius muscle following lymph node biopsy, neck dissection or following a stab injury to the neck.
    Symptoms and examination:
    Patients will frequently report pain at the site of nerve injury due to scar tether of the spinal accessory nerve and associated cutaneous branches including the great auricular nerve. Patients may report altered sensation over the lower ear in such cases. Tinel’s sign may be elicited on tapping over the course of the nerve in the posterior triangle. Wasting of the trapezius muscle is usually obvious with the affected shoulder lying lower than the unaffected side. It is usually this shoulder asymmetry that patients notice first and report to the examining clinician.
    Investigation:
    Neurophysiology involving electromyography of the affected side trapezius muscle may demonstrate denervation changes including increased insertional activity, fibrillation potentials and positive sharp waves.
    There is no role for imaging for the spinal accessory nerve. Ultrasound can demonstrate a neuroma but the branches are small and the scar tissue results in poor visualisation. I would recommend surgical exploration if the loss of function follows surgery or penetrating injury. MRI may demonstrate denervation oedema in the affected trapezius muscle.
    Non-operative management:
    Non-operative management can be employed when there is evidence of reinnervation on EMG, improving motor function and no pain. This scenario will only be seen when there has been a tractional injury to the spinal accessory nerve with axonopathy without nerve rupture. Recovery is usually early, rapid and progressive. Scar management with massage may reduce nerve tether. Pain implies scar entrapment, tether or discontinuity and should prompt exploration using nerve stimulation.
    Alternative operative management and contraindications:
    Neurolysis can be performed if there is continuity of the nerve and evidence of stimulation. If there is discontinuity or a neuroma in continuity without conduction then the damaged segment should be excised and grafted.
    Autologous nerve grafting remains the gold standard, however there is a role for using processed nerve allograft as a bridge in small gaps up to 5cm. The allograft is supplied frozen in various diameters and a typical spinal accessory nerve reconstruction would require a 2-3mm diameter allograft in the upper part of the posterior triangle. Trophic nerve stimulation may be used to assist recovery in the phase of reinnervation.
    Sural nerve harvest can be performed using endoscopic harvesting techniques to minimise the size of the lower leg scar and reduce donor site complications.
    If the proximal stump cannot be identified a nerve transfer to the distal stump can restore useful motor function. The lateral pectoral nerve has been described as a donor in such cases, however is there is insufficient distal nerve stump an interposition nerve graft may be required to bridge the defect.

    Setup

    The patient is carefully examined pre-operatively and the site of maximum tenderness is marked and any Tinel’s sign points are marked.
    Under general anaesthesia without neuromuscular blockade the patient is positioned supine with the head supported on a head ring and turned 30 degrees to the opposite side. the table is broken at the waist to achieve a 30 degree head up position to minimise any intra-operative venous bleeding.
    The neck is prepped and the whole upper limb is included in case of need to extend the dissection to view the upper trunk of the brachial plexus. (this is essential when exploring stab wounds).
    The head is wrapped in a “turban” double drape that allows high exposure of the posterior triangle and the arm is left free in a limb drape. Posteriorly the drapes are place behind the trapezius and secured with tapes.

    Operation – 1

    A-B Previous transverse neck incision for lymph node biopsy
    C Ear lobe
    D Wasted lateral trapezius
    This is a view of the right posterior triangle. The patient’s head is upper left and the shoulder lower right of the photograph. The point of maximum tenderness is 1cm proximal to the midpoint of this scar.

    The posterior border of the sternocleidomastoid is marked to identifty the course of the spinal accessory nerve (XI). The original transverse surgical scar is marked.

    The skin is opened proximal and distal to the old surgical scar using “Z” extensions.
    Exploration for a nerve injury in scar is not advised. Proximal and distal ends should be identified in normal tissue and traced into the zone of injury.
    The skin is elevated and careful spreading of the subcutaneous issues identifies the great auricular nerve which leaves the interval between trapezius posteriorly and sternocleidomastoid anteriorly and runs proximally across the upper sternocleidomastoid to supply sensation on the lower ear.

    The great auricular nerve is tagged with a blue sloop which provides gentle traction to assist neurolysis with minimal nerve handling.

    The nerve stimulator conforms that this is a sensory nerve. The sloop lifts the nerve away from the underlying muscle so that there is no confusing direct cross stimulation at high stimulation threshold testing.

    Neurolysis along the nerve deep posterior to sternomastoid identifies this as the great auricular nerve. The interval is now identified where the rest of the cervical plexus, the supraclavicular nerves and the XIth cranial nerve enter the posterior triangle. This areas can now be explored further.
    SCM – Sternocleidomatoid muscle.

    The cervical plexus is identified and tagged with sloops.
    The upper blue sloop marks the great auricular nerve.
    The yellow sloop marks the cervical plexus.
    The lower blue sloop marks the supraclavicular nerves.
    The upper white sloop marks the proximal stump of the injured XIth cranial nerve that is petering out in scar just proximal to the old surgical scar.
    The lower white sloop marks the distal XIth nerve as it passes laterally along the anterior border of the trapezius muscle.

    The upper white sloop demonstrates the spinal accessory nerve stump proximally retracted and tethered in scar. This matched the site of maximum tenderness of clinical examination approximately 15mm proximal to the transverse posterior triangle scar.

    Neurolysis of the proximal spinal accessory nerve stump.

    Confirming that there is no functional connect with the trapezius after neurolysing the proximal spinal accessory nerve stump and identification of an end neuroma tethered in scar.
    A – marks the end neuroma tethered in scar

    Following resection of the proximal stump neuroma and debridement. The microsurgical background supports the proximal and distal nerve ends ready for gap measurement.

    The close up view demonstrates a gap of almost 40mm in the spinal accessory nerve following debridement and inspection of the nerve ends under the operating microscope.
    A graft of approximately 6cm will be used to minimise tension during neck movements.
    The options for graft include autologous sensory nerves from the cervical plexus, sural nerve or processed nerve allograft.
    The decision in this cases was for autologous sural nerve harvest as the cervical plexus function was intact and the evidence to support motor regeneration with processed nerve allograft is limited for pure motor nerves currently. The sural nerve remains the gold standard for this size of defect.

    The leg is prepped and draped with a thigh tourniquet inflated after exsanguination.
    The course of the sural nerve is marked.
    The sural nerve lies on a line between the midpoint of the gastrocnemius at the distal aspect of the popliteal fossa and a point mid way between the postertior aspect of the Achilles tendon and the posterior aspect of the lateral malleolus at the level of the ankle joint.
    The skin is incised in the distal part of this marked line just above the ankle joint line.
    The short saphenous vein is identifed and this gives a guide to the position of the sural nerve which runs with it.

    The sural nerve is identified and a Mixter used to pass a sloop around the nerve for retraction to assist dissection and minimise handling of the nerve.

    Retrieval of the sloop around the sural nerve for retraction.

    Dissection of the sural nerve continues distally and then proximally using Jamieson scissors. The sloop is used to retract the nerve during dissection. Branches of the short saphenous vein crossing the nerve should be cauterised with bipolar diathermy.

    A – Sural nerve
    B – Short saphenous vein

    Once the sural nerve is identified the skin is incised further along the line of the nerve and the dissection is continued proximally.
    Here the nerve is being dissected from the loose perivascular connective tissue around the short saphenous vein.

    A ruler is used to measure the required length of donor nerve graft.

    The nerve is marked at its distal end to allow reversal when sutured into the recipient area. Because this is a sensory nerve it has side branches. Reversal ensures that each endoneurial tube at the proximal co-aptation has an exit at the distal co-aptation site. Without reversal there is a risk of axonal escape as regenerating nerve fibres leave through side branches, reducing the axon density at the distal co-aptation.

    The proximal end of the sural nerve is cut above the proximal wound edge between branch points under moderate tension. This allows retraction away from the surgical scar and reduces the risk of a painful neuroma with tether (neurostenalgia) developing.

    The donor site is sutured with an absorbable subcuticular suture and local anaesthetic infiltrated.
    Steristrips are applied and an occlusive dressing.

    A bulky wool and crepe bandage is applied to the leg to support the wound and provide moderate compression.
    The leg tourniquet is then released.

    Whilst the leg is closed the microsurgical graft can be sutured in place in the neck.

    The positioning of the operating microscope set up in the neck is difficult for an assistant and can be easily performed by a single surgeon.

    The reversed sural nerve autograft is positioned in the neck and the proximal neurorraphy is sutured under the operating microscope using a 9’0 nylon suture and microinstruments.

    Operation – 2

    Usually 3 well placed sutures are sufficient for the co-aptation.

    It is important that the graft is positioned to fully cover the proximal recipient nerve stump and that the sutures are not under tension and are well spaced. Too much tension causes fascicular distortion and is more likely to result in scar at the neurorraphy site and poor axonal regeneration across the suture line.

    The graft is cut to the required length allowing some redundancy for a tension free reconstruction, allowing for range of motion of the neck. The distal neurorraphy is completed in the same fashion as the proximal with well spaced low tension 9’0 interrupted sutures placed using microinstruments with operating microscope magnification.

    A fibrin tissue glue is used to support the neurorraphy at each end.
    There are two solutions, fibrinogen and an activator. They are mixed at the tip of the cannula producing a fibrin clot.

    The wound is closed with repair of the platysma and subcuticular absorbable suture closure.

    The closed wound has local anaesthetic infiltration.

    Steristrips apllied to the wound.

    Occlusive dressing applied to the neck wound.

    Post Operative

    Following surgery the patient is nursed 30 degrees head up and monitored for neck swelling. The patient can be discharged the same day as long as there are no problems at either surgery site.
    The leg should be elevated at rest for 1 week.
    The bulky dressings around the leg can be reduced and the wounds inspected at both sites and the occlusive dressings replaced.
    The wounds should be kept clean and dry for 10 days after which showering is possible.
    Scar massage can then be commenced with a moisturising cream to help scar maturation and reduce sensitivity.
    Clinical follow up at 6 weeks should assess for any complications at the donor sire and ensure that the patient understands the expected time frame for reinnervation over the next 6-12 months.
    Clinical follow up at 4 months should demonstrate deep muscle squeeze tenderness from the early reinneravtion through the graft.
    Visible contraction should be present by 6 months and muscle bulk recovering by 12 months.
    Further improvements in bulk and strength may then be expected for a further 2 years.

    Recommended Reading

    Nerve grafting success depends on a number of factors:
    The quality of the proximal nerve stump
    The duration of denervation
    The distance form the injury site to the muscle
    The length of the graft
    The type of graft used
    The quality of the repair
    The quality of the bed
    Age is not a barrier to successful reinnervation through a graft although the brain plasticity required for relearning in mixed motor and sensory nerves may be a factor influencing outcome. The very young brain in infants and children is more plastic than in adults.

    References:
    Vastamaki M, Solonen KA. Accessory nerve injury. Acta Orthop Scand 1984; Jun;55(3):296-9
    Park SH, Esquenazi Y, Kline DG, Kim DH. Surgical outcomes of 156 spinal accessory nerve injuries caused by lymph node biopsy procedures. J Neurosurg Spine 2015;Oct;23(4):518-25. doi: 10.3171/2014.12.SPINE14968. Epub 2015 Jun 26
    Butler DP, Johal KS, Wicks CE, Grobbelaar AO. Objective sensory and functional outcomes at the donor site following endoscopic-assisted sural nerve harvest. J Plast Aes Recon Surg 2017; May;70(5):659-665. doi: 10.1016/j.bjps.2017.02.022. Epub 2017 Feb 28
    Safa B, Buncke G. Autograft Substitutes: Conduits and Processed Nerve Allografts.Hand Clinics 2016 May;32(2):127-40. doi: 10.1016/j.hcl.2015.12.012.
    Maldonado AA, Spinner RJ. Lateral pectoral nerve transfer for spinal accessory nerve injury. J Neurosurg Spine 2017; Jan;26(1):112-115. doi: 10.3171/2016.5.SPINE151458. Epub 2016 Jul 29

    Reference

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