Carpal Tunnel vs Cubital Tunnel vs Guyon's Canal: Ulnar vs Median Nerve
Upper Limb · 9 min read · 2026-03-07
Introduction
Hand numbness and weakness are among the most common complaints in clinical practice. Three compression neuropathies dominate: carpal tunnel syndrome (median nerve at the wrist), cubital tunnel syndrome (ulnar nerve at the elbow), and Guyon's canal syndrome (ulnar nerve at the wrist). Each produces a distinct clinical pattern that becomes unmistakable once you understand the anatomy.
Carpal Tunnel Syndrome (Median Nerve at the Wrist)
The median nerve passes through the carpal tunnel beneath the flexor retinaculum.
Sensory: Numbness and tingling in the thumb, index, middle, and radial half of the ring finger (palmar side). The thenar eminence is spared because the palmar cutaneous branch arises proximal to the tunnel.
Motor: Weakness of the thenar muscles — specifically opponens pollicis, abductor pollicis brevis, and the lateral two lumbricals. Late cases show thenar wasting.
Provocative tests: Phalen's test (wrist flexion), Tinel's at the wrist, Durkan's compression test.
Cubital Tunnel Syndrome (Ulnar Nerve at the Elbow)
The ulnar nerve runs through the cubital tunnel behind the medial epicondyle.
Sensory: Numbness in the little finger and ulnar half of the ring finger — both palmar and dorsal surfaces. The dorsal hand is also affected because the dorsal cutaneous branch arises proximal to Guyon's canal.
Motor: Weakness of intrinsic hand muscles — interossei (finger abduction/adduction), medial two lumbricals, adductor pollicis, and hypothenar muscles. Froment's sign positive. Claw hand deformity (paradoxically more pronounced in low ulnar lesions).
Key sign: Elbow flexion test reproduces symptoms. Tinel's at the cubital tunnel.
Guyon's Canal Syndrome (Ulnar Nerve at the Wrist)
The ulnar nerve passes through Guyon's canal at the wrist, superficial to the flexor retinaculum.
Sensory: Numbness in the little finger and ulnar ring finger — palmar surface only. Critically, the dorsal hand sensation is normal because the dorsal cutaneous branch has already branched off proximal to the wrist.
Motor: Similar to cubital tunnel but the pattern depends on which zone of Guyon's canal is compressed (motor only, sensory only, or mixed).
The Differentiating Algorithm
The Critical Question: Dorsal Hand Sensation
This single test separates cubital tunnel from Guyon's canal. If the dorsum of the hand (ulnar side) is numb, the lesion is at or above the elbow. If dorsal sensation is preserved, the compression is at the wrist in Guyon's canal.
Clinical Pearl
Patients with carpal tunnel syndrome often describe waking at night with numbness in "the whole hand." On careful questioning and examination, the thumb and index finger are always worse, and the little finger is spared. The subjective feeling of "whole hand numbness" is common but the objective findings are median nerve territory.
Summary
Median territory = carpal tunnel. Ulnar territory with dorsal hand involvement = cubital tunnel. Ulnar territory with dorsal hand spared = Guyon's canal. Three tests, three diagnoses.