Radial Mononeuropathy Workup

Updated: Jul 19, 2021
  • Author: Nasheed I Jamal, MD; Chief Editor: Nicholas Lorenzo, MD, CPE, MHCM, FAAPL  more...
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Workup

Imaging Studies

A study showed that ultrasound examination can localize radial neuropathy more rapidly than standard electrophysiological testing. [21, 22] Visualization of the superficial radial nerve with high-resolution sonography has recently been reported. [23, 24]

Occasionally, imaging of the elbow region or the humeral area is indicated to determine if any mass or bony lesions are compressing the nerve. Plain radiographs may show bony causes of compression, such as fractures, dislocations, callus formations, or osteophytes. MRI is particularly helpful for soft tissue evaluation and more direct imaging of the nerve. [18]

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Laboratory Studies

Blood tests can be used to identify underlying conditions that may cause or contribute to generalized neuropathy and may include:

  • Comprehensive metabolic panel

  • Blood glucose and HbA1c

  • Vitamin B12

  • Thyroid panel

  • Heavy metal blood levels

  • Infectious workup

  • Autoimmune disorders: antinuclear antibody (ANA)

  • Serum protein electrophoresis (SPEP)

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Procedures

Nerve conduction studies and needle electromyography (EMG) are essential for specific localization and to rule out a more generalized process. Nerve conduction studies of both the superficial radial sensory and radial motor nerves should be performed. For the radial motor study, stimulation sites include the forearm, the elbow, below the spiral groove, and above the spiral groove.

Needle EMG is used to differentiate among posterior interosseus neuropathy, radial neuropathy at the spiral groove, radial neuropathy in the axilla, a posterior cord lesion, C7 radiculopathy, and a central lesion. Muscle selection often includes the triceps, brachioradialis, extensor carpi radialis, extensor digitorum communis, extensor carpi ulnaris, and extensor indicis proprius.

Nerve and skin biopsies to evaluate nerve damage are rarely needed.

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Staging

Various grading systems have been used by physicians for classifying peripheral nerve injuries including the Seddon classification (1972) and the Sunderland classification (1978).

The Seddon classification groups nerve injuries into three categories. [25]

1. Neuropraxia

  • Transient complete motor paralysis with minimal sensory involvement that commonly results from mechanical pressure. Spontaneous recovery often occurs when the offending pressure is removed.

2. Axonotmesis

  • More severe than neurapraxia and results from the disruption and loss of continuity of the axon with preservation of the supporting connective tissue structures including the endoneurium, perineurium, and epineurium. It is characterized by loss of both motor and sensory function. Complete recovery depends on removal of the insult and axon regeneration.

3. Neurotmesis

  • This is the most severe level of injury characterized by complete transection of the peripheral nerve leading to complete loss of sensory and motor function. Spontaneous recovery of function is unlikely and suboptimal without surgical intervention.

The Sunderland classification groups nerve injuries into five degrees. Grade 1 and grade 2 correspond to neurapraxia and axonotmesis, respectively. Grades 3, 4, and 5 correspond to increasing levels of neurotmesis severity. Grade 3 refers to loss of axonal and endoneurial continuity. Grade 4 involves loss of axonal, endoneural, and perineurial continuity. Grade 5 corresponds to loss of axonal, endoneurial, perineural, and epineural continuity. [26]

 

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