Ulnar neuropathy

Background

Nerves of the left upper extremity.

Transverse section across distal ends of radius and ulna.

• 2nd most common focal mononeuropathy
• Results from compression of ulnar nerve either at elbow (cubital tunnel) or wrist (Guyon's canal)
  • Compression at elbow more common
• Ulnar nerve provides cutaneous sensation to the 5th digit and ulnar side of 4th digit and motor innervation to flexor carpi ulnaris, flexor digitorum profundus, hypothenar, interossei, and adductor pollicis muscles
• Etiology: Intrinsic/extrinsic compression, trauma, more rarely infectious or vasculitis

Risk Factors

• Male > Female
• Increasing age
• Smoking
• Cyclists (handlebar palsy)

Clinical Features

History

• Paresthesias, numbness, and pain in 4th and 5th digits
• Symptoms often worse with repetitive elbow flexion
• Grip weakness, weak thumb adduction
• Severe cases with muscle atrophy and clawing of fingers

Physical

• Sensation testing - deficits in ulnar distribution
• Strength testing - weak abduction and adduction of the fingers and thumb
  • Specifically adductor pollicis weakness resulting in positive Froment sign
• Tinel test at elbow and/or wrist (nonspecific)

Differential Diagnosis

• C8/T1 nerve root lesion
• Medial cord brachial plexus lesion
• Diabetic neuropathy
• Amyloidosis
• Peripheral nerve tumor

Upper extremity peripheral nerve syndromes

Median Nerve Syndromes

• Carpal tunnel syndrome
• Pronator teres syndrome
• Anterior interosseous neuropathy

Ulnar Nerve Syndromes

• Ulnar neuropathy

Radial Nerve Syndromes

• Radial neuropathy at the spiral groove (ie. "Saturday night palsy")
• Posterior interosseous neuropathy

Proximal Neuropathies

• Suprascapular neuropathy
• Long thoracic neuropathy
• Axillary neuropathy
• Spinal accessory neuropathy
• Musculocutaneous neuropathy

Other

• Brachial plexopathy
  • Parsonage-Turner syndrome
• Cervical radiculopathy

Evaluation

Workup

• No imaging necessary if no history of trauma
  • XR/CT if considering hook of hamate fracture
  • US can reveal nerve thickening, hypoechoic texture, or anatomic compression
    • Maximum diameter at medial epicondyle >2.4 mm (81% sensitive, 91% specific)
• Labs unlikely to be revealing in absence of systemic symptoms

Diagnosis

• Clinical diagnosis
  • EMG and/or nerve conduction study can confirm in outpatient setting

Management

• NSAIDs
• Activity modification
• Splinting to limit elbow flexion to 45 to 90 degrees
  • Often recommended at night although efficacy data and compliance are variable

Disposition

• Discharge
• Primary care, sports med, or ortho follow up

See Also

• Peripheral nerve syndromes

References

• Latinovic R, Gulliford MC, Hughes RA. Incidence of common compressive neuropathies in primary care. Journal of Neurology, Neurosurgery & Psychiatry. 2006 Feb 1;77(2):263-5.
• Radiculopathy, Plexopathy, and Mononeuropathies of the Upper Extremity. In: Berkowitz AL. Berkowitz A.L.(Ed.),Ed. Aaron L. Berkowitz.eds. Clinical Neurology and Neuroanatomy: A Localization-Based Approach. McGraw Hill; 2016. Accessed September 06, 2021. https://accessmedicine-mhmedical-com.proxy.medlib.uits.iu.edu/content.aspx?bookid=1984&sectionid=147771511
• Gilchrist JM, Dandapat S. Neuromuscular Mimics of Entrapment Neuropathies of Upper Extremities. HAND. 2020 Sep;15(5):599-607.
• Beekman R, Schoemaker MC, Van Der Plas JP, Van Den Berg LH, Franssen H, Wokke JH, Uitdehaag BM, Visser LH. Diagnostic value of high-resolution sonography in ulnar neuropathy at the elbow. Neurology. 2004 Mar 9;62(5):767-73.