Peripheral Nerve Injuries Workup

Updated: Oct 05, 2018
  • Author: Christine B Novak, PT, MS, PhD; Chief Editor: Murali Poduval, MBBS, MS, DNB  more...
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Workup

Imaging Studies

Imaging studies are appropriate in cases of suspected nerve tumors, though false-negative and false-positive findings are possible in magnetic resonance imaging (MRI) evaluation of nerve tumors.

Imaging studies are appropriate in cases of suspected brachial plexus avulsion injury to evaluate for avulsion of the nerve roots from the spinal cord. Computed tomography (CT) myelography can be used to investigate for suspected brachial plexus avulsion injury, though it has largely been replaced with MRI in this setting.

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Other Tests

Electrodiagnostic studies are useful in detecting nerve injury, nerve compression, or both, as well as in identifying early stages of recovery. [8]

Electromyography (EMG) is performed at least 4 weeks after nerve injury. EMG testing done earlier than this may yield false-negative findings because it takes 4-6 weeks for muscle fibrillations to become apparent. Evidence of denervation is indicated by the presence of fibrillations in the muscle. Reinnervation is signaled by the presence of motor unit potentials (MUPs).

Nerve conduction studies are particularly useful in identifying secondary compression sites that may be present. If the nerve is compressed at an entrapment site, such as the carpal tunnel or the cubital tunnel, axonal regeneration may be impeded and thus limit reinnervation. In cases of brachial plexus injury, nerve conduction studies can help determine the presence of an avulsion injury. Intact normal distal sensory nerve conduction and motor denervation are diagnostic of an avulsion injury.

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