Muscle atrophy to the first dorsal web space is indicated by the arrow on a man’s right hand that is experiencing progressive weakness.
A 56-year-old man presents with several months of progressive weakness of the right hand. He works in construction and has had difficulty grasping objects. On examination, atrophy to the first dorsal web space is seen, as shown in the image.
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Entrapment neuropathy of the ulnar nerve can occur at the elbow, forearm, or wrist. Nerve entrapment around the elbow, or cubital tunnel syndrome, is the second most common compression neuropathy in the upper extremity, following carpal tunnel syndrome.
The ulnar nerve passes in a groove, or the cubital tunnel, at the posterior aspect of the medial epicondyle. The nerve undergoes compression, traction, and friction within the tunnel during elbow motion. The ulnar nerve can elongate by up to 8 mm with elbow flexion. Nerve compression at the elbow may also result from elbow fractures, arthritis, and cubitus varus or valgus elbow deformities.
Patients with cubital tunnel syndrome have paresthesia of the small finger and ulnar half of the ring finger. Elbow pain that radiates into the proximal forearm is often present. Symptoms can worsen at night when patients flex their elbow during sleep. Occupations or sporting activities that require repetitive elbow flexion with a valgus stress can also cause symptoms.
Physical examination findings may include muscle atrophy of the first dorsal web space, clawing of the small and ring fingers, weakness with grasping objects, and weakness with intrinsic muscle testing. A positive Tinel sign is noted when tapping over the nerve at the elbow causes pain and paresthesia of the ring and small finger. Ulnar nerve paresthesia caused by flexing the affected elbow as much as possible for 60 seconds is sensitive for cubital tunnel syndrome. Other tests for cubital tunnel syndrome include Froment sign, Wartenberg sign, Jeanne sign, and Masse sign.
It is important to differentiate nerve entrapment at the wrist (ulnar tunnel syndrome caused by direct compression in Guyon canal) and cubital tunnel syndrome. Weakness of the flexor digitorum profundus of the small finger and numbness to the dorsal ulnar side of the wrist are unique examination findings of cubital tunnel syndrome.
Initial treatment of cubital tunnel syndrome consists of activity modification, night splints to limit elbow flexion, elbow pads to reduce contact irritation, and nonsteroidal anti-inflammatory drugs. Patients that work with a keyboard at a desk should elevate their chair and lower the keyboard to reduce elbow flexion.
If patients do not have relief after 4 to 6 weeks of conservative treatment, or if they present initially with muscle weakness or atrophy, electrodiagnostic studies are recommended. Electromyography and nerve conduction studies help determine whether there is abnormal or slow nerve conduction caused by entrapment.
Surgical indications may include persistent weakness, paresthesia, and decreased nerve conduction velocities on electromyography. Surgical techniques include in situ decompression, anterior submuscular transposition, and medial epicondylectomy.
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
- Gellman H. Compression of the ulnar nerve at the elbow: cubital tunnel syndrome. Instr Course Lect. 2008;57:187-197.
- Wheeless CR III. Cubital tunnel syndrome. In: Wheeless CR III, Nunley JA II, Urbaniak JR, eds. Wheeless’ Textbook of Orthopaedics. http://www.wheelessonline.com/ortho/cubital_tunnel_syndrome. Updated May 31, 2012. Accessed December 15, 2015.