Cubital Tunnel Syndrome (Ulnar Neuropathy): Pathogenesis and clinical findings
Osteoarthritis
Rheumatoid arthritis
Diabetes mellitus (see Calgary Guide slide on Diabetic Neuropathy)
Degenerative bone & joint changes
Autoimmune damage to joints
Abnormal bone structure/lesions
Idiopathic
Hyperglycemia causes nerve damage (complex mechanisms)
Elbow trauma
Repetitive elbow flexion
Authors: Chris Oleynick Alexandros Mouratidis Yan Yu* Reviewers: Annalise Abbott Sean Crooks Davis Maclean Hannah Koury Jeremy LaMothe* Ian Auld* * MD at time of publication
Inflammation or edema in cubital tunnel (space between medial epicondyle of humerus and olecranon of ulna) where ulnar nerve is found
↓ size of the cubital tunnelà↑ pressure on internal contents (e.g. ulnar nerve)
Axonal conduction is interrupted
Myelin sheath is damaged
↓ blood supply to nerve
Weakness of adductor pollicus longus (works to adduct thumb)
↑ compensatory activity of flexor
pollicis longus with pinching
↓ activity of hypothenar muscles (which move the 5th digit)
↓ activity of 5th digit palmar interosseus muscles (which adduct the 5th digit)
Cubital Tunnel syndrome: compression neuropathy
Paresthesia
Abnormal sensations of skin (“pins & needles”, tingling, burning, and/or numbness) in ulnar nerve sensory distribution
ulnar nerve
↓ activity of muscles innervated by ulnar nerve (medial forearm flexors, hypothenar muscles, interossei muscles, adductor pollicis longus)
+ Tinel sign
over cubital tunnel (tapping at medial elbow causes discomfort and/or paresthesia)
Weak pinch & ↓ grip strength
+ Froment’s sign
(thumb hyperflexion compensates for weak pinch)
Hypothenar atrophy
+ Wartenburg’s sign
(involuntary, excess abduction of 5th digit)
of the
Altered sensation in areas innervated by ulnar nerve (medial forearm and wrist, 5th digit, and medial half of 4th digit)
+ elbow flexion test
(flexing elbow & extending wrist further ↓ volume of the cubital tunnelà paresthesia in ulnar nerve sensory distribution
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
First published January 12, 2017, re-published February 28, 2021 on www.thecalgaryguide.com