Ulnar nerve compression occurs mainly at the elbow and wrist as cubital tunnel syndrome and Ulnar tunnel syndrome
A. Cubital Tunnel Syndrome
Compressed at the cubital tunnel which is the second most common compression neuropathy at the wrist
Anatomy
Roof: Formed by FCU fascia and Osborne ligament (travel from the medial epicondyle to olecranon)
Floor: Formed by posterior and transverse bands of MCL and elbow joint capsule
Walls: Formed by medial epicondyle and olecranon
Sites of compression
Compressed in a cubital tunnel
Bony abnormalities, ganglion, hypertrophic synovium, and distal transverse fibers of the arcade of Struthers (8 cm proximal to medial epicondyle)
Proximal to cubital tunnel
Formed by the arcade of stuthers and medial intermuscular septum
Distal to cubital tunnel
Through 2 heads of FCU (Osbourne canal) and Osborne fascia
Sometimes stretched by cubital valgus deformity or elbow flexed for a long period
Clinical features
- Numbness and tingling in the little finger and ulnar half of ring finger
- Increases when the patient lying with the elbow flexed (reading/ mobile use)
- Forment sign : (+) and other ulnar nerve tests
- Tinel percussion test: (+)
Investigation
NCV: Conduction velocity of less than 50m/sec across the elbow is typical threshold for diagnosis; larger decrease signifies worse prognosis
Treatment Options
Conservative measure
- Modification of postures
- Splinting of the elbow (mid-extension at night)
- FCU stretching
- NSAIDs
Operative measures
Indications for surgery:
- Intrinsic wasting
- Symptoms persistance
Options:
- A simple release of the roof of a cubital tunnel (In situ decompression)
- Anterior transposition of the nerve into a subcutaneous/ submuscular/Intramuscular plane or medial epicondylectomy
B. Ulnar Tunnel Syndrome
Compression in Guyon’s canal of ulnar nerve
Anatomy
Floor: Transverse carpal ligament, hypothenar muscle
Roof: Volar carpal ligament
Ulnar border: Pisiform and pisi-hamate ligament, abductor digiti minimi muscle belly
Radial border: Hook of hamate
Zones of Guyon’s canal
Zones | Location | Compression | Neurology |
---|---|---|---|
Zone 1 | Proximal to the bifurcation of nerve | Ganglia and hook of hamate | Mixed motor and sensory |
Zone 2 | Surrounds deep motor branch | Ganglia and hook of hamate | Motor only |
Zone 3 | Surrounds superficial sensory branch | Ulnar artery thrombosis/ aneurysm | Sensory only |
Deep motor branches
- Innervates all intercostal muscles and 3/4 lumbricals
- Adductor pollices, Hypothenar muscle, Medial head of FPB
Treatment Options
Non-operative
Activities modification, NSAIDs, and splinting
Operative
- Local decompression followed by addressing of underlying cause
- Tendon transfer:
- Indications:
- Correction of clawed finger
- Loss of power pinch
- Wartenberg sign (abduction of the small finger)
- Indications:
- Carpal tunnel release