Distal Trapezius Avulsion From Spine

Diagnosis of brachial plexus injury is based on clinical, electrophysiological and imaging findings. Neuroradiological studies used for the pre-operative diagnosis of root avulsion include CT-myelography and MRI. The accuracies of CT-myelography and MRI for diagnosing cervical root avulsion have been estimated to be 85 and 52%, respectively [13]. Post-traumatic meningocele may not always accompany a root avulsion, and the presence of a post-traumatic meningocele does not necessarily imply the presence of a root avulsion. Furthermore, supr-aclavicular exploration is not always reliable, because extradurally intact roots may be avulsed intradurally. Neuroradiologic findings may be supplemented with intraoperative electrodiagnostic studies, including nerve action potentials and somatosensory evoked potentials. Still, intradural surgical inspection remains the gold standard for the diagnosis of avulsed cervical roots.

Complete restoration of arm function is usually unrealistic following significant brachial plexus injury. Therefore, the surgeon must prioritize which functions to attempt to restore in cases involving multiple cervical roots and spinal nerves. Elbow flexion (musculocutaneous nerve) and shoulder abduction (suprascapular and axillary nerves) are generally considered the most beneficial functions for improving patient quality of life [14].

Proximal brachial plexus lesions may be classified as either post-ganglionic or pre-ganglionic and this is an important distinction when choosing the method of surgical repair. With post-ganglionic lesions, the continuity of the spinal-cervical root is maintained. In such cases where there is continuity of the spinal-cervical root with the spinal cord, a nerve graft may be useful. Studies using sural nerve to reconstruct the musculocutaneous nerve have helped to identify factors affecting the outcome of nerve graft surgeries in cases of post-ganglionic brachial plexus injury [13].

The time interval between brachial plexus injury and surgery should be emphasized as an important factor influencing the success of surgical intervention. In a retrospective study involving 54 cases of musculocutaneous nerve reconstructed with sural nerve grafts, reinnervation of the musculocutaneous nerve occurred in 75% of patients undergoing surgery within 6 months after injury, compared to a reinner-

vation rate of 25% with surgery more than 12 months following injury [15]. Factors that may be detrimental to the success of surgery after a prolonged post-injury interval include degeneration of muscle fibers, fibrosis or scar tissue formation and chronic degeneration of the distal nerve pathway. Length of nerve graft has not been found to be a significant factor in nerve graft repair of the musculocutaneous nerve, although a trend towards better outcomes with shorter grafts has been documented [13,15].

Samii proposed that the length of nerve graft required increases with the severity of injury. Therefore, poor outcomes with longer grafts may be due to the severity of injury, and not caused by the length of graft [15]. Revascularization of nerve grafts occurs from surrounding tissue, such that the increased length of a nerve graft should not be expected to increase ischemia [16].

In cases of pre-ganglionic injury, the avulsed nerve root cannot be used for the reconstruction of a nerve. In these instances, neurotization of the brachial plexus has been used in an attempt to restore function. Options for neurotization of the brachial plexus include the accessory, intercostal, phrenic and hypoglossal nerves [14,17,18].

Use of the accessory nerve is favored by some because, if transected distally, function of the trapezius is not significantly compromised [13]. The accessory nerve may be used either directly with the suprascapular nerve or in conjunction with a free sural nerve graft to reinnervate the musculocutaneous nerve. Use of the phrenic nerve is often discouraged due to possible loss of pulmonary function [13]. As with nerve grafts, outcome following neurotization of the brachial plexus is dependent upon the time interval between injury and surgery [18].

Recently, Carlsted [19] described ten patients who underwent re-implantation of ventral nerve roots into the spinal cord following pre-ganglionic brachial plexus injury. Regeneration and reconnection with muscle were demonstrated in nine of the ten patients, and three of the ten patients recovered some useful function. Co-contraction between antagonistic muscles limited recovery, although there was a decrease in difficulty with co-contractions over time. Again, early surgical intervention within the first month, if possible, was an important prognostic indicator. Direct re-implantation of

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