Ulnar nerve - Guyons canal syndrome

Guyons canal

Semi-rigid canal between the hook of the hamate and the pisiform bone. The roof of the canal is the transverse carpal ligament.

Causes

• Traumatic (often laceration by fracture fragment).
• Compression by ganglion, nerve sheath tumor, lipoma, joint arthropaty, rheumatoid cyst, ulnar artery aneurysm.
• Calcinosis in uremia or scleroderma.

Symptoms & signs

There are three types of syndromes depending on the exact site of lesion:

Type 1: Compression just proximal or within Guyon’s canal:

• All ulnar-innervated intrinsic hand muscles are affected.
• Sensory deficit in the distal ulnar part of the palm and palmar surfaces of 5th finger and medial half of the 4th finger.

Type 2: Compression within the canal.

• All ulnar-innevated intrinsic hand muscles are affected.
• No sensory loss.

Type 3: Compression distal to the canal.

• Paresis and atrophy of interossei, medial two lumbricals, adductor pollicis and deep head of flexor pollicis brevis.
• Hypothenar muscles are unaffected.
• No sensory loss.