Intraoperative Neuromonitoring (IONM) for Brachial Plexus Injuries

The brachial plexus is an essential core of innervation for upper limbs compris…

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The brachial plexus is an essential core of innervation for upper limbs comprising the nerve roots C5 to T1. Injury to the brachial plexus can occur via neuromas or trauma, causing stretching, compression, or severing of nerves and resulting in symptoms of pain, paresthesia, and muscle weakness of the upper limbs. Brachial plexus repair procedures are becoming increasingly relevant due to the most common etiology of motor vehicle accidents. Treatments such as neurolysis, nerve grafts, and nerve transfers benefit greatly from intraoperative neuromonitoring (IONM) to maximize functional restoration postoperatively while minimizing risk.
In less extreme cases where a nerve in the brachial plexus is only stretched or compressed instead of damaged, neurolysis of neural scar tissue or tumor resection can be performed to remove the source of mechanical irritation. For more severely damaged nerves, nerve grafts or nerve transfers may be necessary. Nerve grafts involve the removal of the section of damaged nerve fiber and replacement with part of a nonessential nerve elsewhere in the body to promote neural regeneration. In contrast, nerve transfers seek to reinnervate a severed nerve by reconnecting it to a nonessential nerve in its proximity. Palliative procedures such as dorsal root entry zone (DREZ) lesioning may also be considered in pain management cases for more severe cases of brachial plexus avulsion.
Electromyography (EMG) and somatosensory evoked potentials (SSEPs) can be used clinically and intraoperatively for diagnostic purposes in cases of brachial plexus injuries where studies have found utility in using neural stimulation to localize areas of traumatic lesions and to determine the degree of denervation and remaining neural function. Intraoperatively, EMG can help map out surrounding neural structures for accurate identification during these procedures. At the same time, SSEPs and motor evoked potentials (MEPs) can aid in determining the effectiveness of the surgical procedure by using stimulation to confirm nerve conduction after a nerve graft or transfer. SSEPs and MEPs can also minimize the risk of further injury to the brachial plexus, especially for lesioning and sectioning procedures such as DREZ lesioning, where it has been documented that significant IONM changes can be related to postoperative neurological deficits or tumor dissection. The well-rounded utility of IONM in cases of brachial plexus injury can be valuable in evaluating the neuronal function for diagnostic and surgical purposes and thus in determining further courses of action for patient treatment.
  1. Jahangiri FR, Brachial Plexus Mapping. American Society of Neurophysiological Monitoring (ASNM) annual meeting proceedings. May 2014. Chicago, IL.