The Role of Ultrasound in Surgical Decision-making for Iatrogenic Spinal Accessory Nerve Injuries A Paradigm Shift Alper Cesmebasi, MD1,2, Jay Smith, MD3, Robert J Spinner, MD1 1 Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA 2 Department of Anatomical Sciences, St George’s University, Grenada, West Indies 3 Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN, USA 32nd Annual Meeting of the American Association of Clinical Anatomists 10 June 2015 test

Background Iatrogenic spinal accessory nerve (SAN) injury is a well-described complication with surgical procedures of the posterior cervical triangle Most commonly associated with cervical lymph node biopsy Affects 3-6% of all patients Major cause for malpractice litigation Early diagnosis and management are crucial to restore shoulder stability and function

Methods Patients with suspected iatrogenic SAN transection injury within the posterior cervical triangle were prospectively studied with high resolution US between December 2012 and November 2014 Patients also underwent a thorough neurologic examination and electrodiagnostic testing Operative findings were correlated with the US results

Ultrasonographic Examination Performed in the sitting position with the patient’s head turned to the contralateral side The upper trapezius was identified with the transducer in an anatomic sagittal plane along the anterior edge of the trapezius (at the junction of the middle and lateral thirds) The SAN branch to the trapezius was identified A small (<1mm diameter) oval, hypoechoic structure emerging deep to the anterior edge of the upper trapezius SAN was followed in short-axis proximally through the posterior cervical triangle to the posterior aspect of the sternocleidomastoid (SCM)

Ultrasonographic Examination Findings were interpreted as either “Transections”: Direct visualization of discontinuity Presence of terminal neuromas Denervative changes in upper trapezius “Probable” Absence of sonographically documented nerve discontinuity and/or terminal neuromas Tortuous course of SAN Generalized enlargement of SAN

Sonographic Video

Results (History) Six patients with clinically suspected iatrogenic SAN injures Affected side: 4 right, 2 left Hx of lymph node biopsy (n=5) or peripheral schwannoma removal (n=1) Preoperative electrophysiologic studies showed severe neuropathy in all patients

Results (US/ IntraOp) Time interval (injury to US): 8.4 months (2-17 mo) Findings: 4 complete transection, 2 “probable” Transection confirmed intraoperatively in all patients (n=6) Tx: Direct repairs (n=4), interpositional nerve grafting (n=2)

Intraoperative Photos

Spinal Accessory Nerve The SAN is formed by the fusion of cranial and spinal contributions Enters the posterior cervical triangle from the posterior edge of the SCM, inferior to the junction of its upper and middle thirds Within the triangle, the SAN courses deep to the superficial cervical fascia and adjacent to spinal accessory chain lymph nodes This relationship leaves the SAN prone to injury

Spinal Accessory Nerve Injury Injury within the posterior cervical triangle results in: Trapezius weakness Decreased shoulder abduction from scapular instability Chronic shoulder pain and/or cosmetic disfiguration A 3-6 month observation period is recommended prior to surgical exploration In the setting of SAN transection, this observation period compromises patient’s outcome

Diagnostic Procedures Electrodiagnostic examination is the most sensitive procedure in detecting nerve conduction impairment Con: Unable to provide structural information Voluntary motor unit potentials still noted in transected nerves due to cervical branch innervation Imaging studies (US) may visualize nerve damage

Peripheral Nerve Sonography Role of US in peripheral nerve injury imaging is well established Provides quick, realtime evaluation Studies using US have been able to accurately identify the course and variations of the SAN Nerve injury and scar tissue may be easily identified as hypoechoic masses in the superficial layer of the posterior cervical triangle

Ultrasound in SAN Injury US visualized SAN transection in 4 patients In the remaining two patients, technical limitations precluded direct visualization Enlarged lymph nodes Extensive (dense) scarring Surgical artifacts (staples, clips, etc) Evaluating for secondary signs can aid in correctly diagnosing nerve transections Denervation atrophy of the trapezius Undulating SAN course Generalized enlargement of SAN

Secondary Signs of SAN Injury

Conclusions High resolution US shows great promise in the management of iatrogenic SAN injuries Development of technique and operator training in the visualization of SAN transection lesions, US can improve patient outcomes Identification of transected SAN early on by US will represent a paradigm shift in patient care by hastening surgical intervention

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