Radial neuropathies

Radial neuropathies are conditions caused by acute or chronic injury to the radial nerve. Clinical presentations vary with the mechanism, site, and extent of nerve injury. The radial nerve arises from the posterior cord of the brachial plexus, which comprises cervical roots C5–T1. Within the upper extremity, the radial nerve has lateral cutaneous sensory branches and innervates extensors. When injured, radial neuropathies are therefore characterized by sensory symptoms of pain, paresthesia, and numbness, as well as motor symptoms of weakness of extension at the elbow, wrist (“wrist drop”), and/or fingers. Several risk factors are associated with subtypes of radial neuropathies, including crutch use, intoxication, fracture of the humerus or radius, use of tight watch bands or handcuffs, and repetitive pronation and supination. The patient history and examination, including Tinel's sign, may be sufficient for diagnosis in some cases, but x-ray is necessary in the presence of trauma, and electrodiagnostics, though less useful than in carpal tunnel syndrome, may be considered if symptoms persist. Conservative management, consisting of local corticosteroid injections and counseling to reduce risk factors, is typically the treatment of choice in nontraumatic cases. Surgical decompression, with approach varying by location, may be considered in refractory cases.

• Risk factors vary according to the location of the injury:
  • Axilla: improper crutch use (crutch palsy)
  • Mid-arm:
    • Fracture of humerus (radial nerve runs in spiral groove)
    • Compression of the radial nerve due to draping of arm over furniture (saturday night palsy) or pressure on the axilla or upper medial arm; more likely in the setting of intoxication, anesthesia, or sleep (honeymoon palsy)
  • Elbow: radial tunnel syndrome (controversial diagnosis ) due to chronic compression within the radial tunnel
  • Deep forearm: posterior interosseous nerve syndrome (a syndrome characterized by weakness of muscles in the extensor compartment of the forearm) due to fracture of the radial head or chronic soft tissue compression
  • Superficial forearm or wrist: superficial radial nerve compression, called “cheiralgia paresthetica,” often due to tight wristwatches or handcuffs or repetitive pronation and supination

References:^[1][2][3]

The higher (more proximal) the lesion, the greater the number of extensor muscles involved!

References:^[1][2][3][4]

• History:
  • Inquire about risk factors, including substance use, trauma, and causes of compression.
  • Ask the patient to describe the timeline of symptoms, history of similar symptoms, and associated symptoms such as joint pain.
• Physical examination: Focus the exam on the most proximal location of injury, if known (see “Clinical Features”)
• Instrumental diagnostics: x-ray, electromyography (EMG), nerve conduction studies, ultrasound, MRI

References:^[2][3][5]

• The treatment of choice depends on the severity and persistence of symptoms.
• Conservative therapy
  • Rest
  • NSAIDs
  • Local glucocorticoid injections (if needed)
  • Physical therapy
• Surgical therapy in severe and treatment-resistant cases: nerve decompression, neurorrhaphy, nerve transplantation, tendon transfer ^[6]
• Orthopedic repair of fractures, dislocations, or other traumatic injuries

References:^[2][6]