Citations

Background and Objectives: Peripheral nerve stimulation (PNS) may provide analgesia for neuropathic pain syndromes in that nerve distribution. PNS electrode placement using ultrasound (US) guidance for upper extremity pain syndromes has not been reported. Existing anchoring technology may allow permanent implantation without significant migration. Methods: Three cadaver midhumeral fresh frozen upper extremity specimens were studied. US scanning was performed, targeting electrode placement at the radial, ulnar, and median nerves. Leads were anchored in the superficial fascia. The targeted nerves were exposed by careful dissection. Visual inspection for gross nerve damage, and electrode proximity to the nerve was performed. After confirmation of adequate lead placement, 2 extremities were sutured and placed in a continuous passive motion (CPM) machine for 21 hours to simulate activity. Each electrode was assessed for migration. Results: Acceptable locations for US-guided electrode placement were: radial nerve approximately 10-14 cm superior to the lateral epicondyle; median nerve approximately 6 cm below the antecubital fossa; and ulnar nerve approximately 9 to 13 cm above the medial epicondyle. One electrode was placed at each site without difficulty. After careful exposure, visual inspection showed no gross nerve damage. Each electrode had at least 2 electrical contacts within 2 mm of the nerve sheath. At CPM termination, only the median nerve electrode on 1 cadaver extremity had migrated significantly. Conclusions: This new minimally invasive approach to lead placement requires further study to determine implantation criteria, optimal locations, anchoring techniques, and electrode design to define best clinical practice.

A peripheral nerve or spinal cord injury is a rare but significant complication of regional anesthesia. Evaluation of acute nerve injury includes a focused history and examination to localize the lesion. Confirmatory testing should include electromyography and appropriate imaging. In most cases magnetic resonance imaging (MRI) is preferred to computed tomography (CT) or ultrasound given the better resolution of the nerves and soft tissue. Most cases of peripheral nerve injury will improve and resolve without deficit. In mild cases reassurance and observation is all that is necessary. In more severe cases, if the deficit is progressive or complete, surgical exploration should be considered. If there is no recovery by 2 to 5 months then referral to a peripheral nerve surgeon should be considered. The prognosis for cauda equina or spinal cord lesions is more guarded. Recovery from these is commonly incomplete. Early diagnosis and intervention is the key to preventing catastrophic neurological outcomes.