Nerve
Ulnar nerve
Fine hand control and little-finger-side sensation
High-yield
Its deep hand branch supplies the interossei, medial lumbricals and adductor pollicis, among other muscles. The nerve enters the hand superficial to the flexor retinaculum, through a passage separate from the carpal tunnel.
Overview
This medial-cord branch runs past the inner elbow before reaching the hand through Guyon's canal. It supplies two forearm muscle territories and most of the small hand muscles used for finger positioning and firm pinch.
Learning this group? Read How to learn the brachial plexus.
Reference facts
- Root value
- Mainly C8-T1 through the medial cord, with a variable C7 contribution
- Course
- Descends medially in the arm, passes behind the medial epicondyle and between FCU heads, then enters Guyon's canal at the wrist
- Motor
- FCU and the ulnar FDP portion; most intrinsic hand muscles, including hypothenar muscles, interossei, lumbricals 3-4, adductor pollicis and usually deep FPB. Palmaris brevis receives the superficial branch
- Sensory
- Little finger and ulnar half of the ring finger, with adjacent medial palm and dorsal hand; exact boundaries and branch involvement vary
Clinical correlation
Loss of intrinsic muscle balance can claw the ring and little fingers. Clawing may look stronger after a distal lesion because the ulnar FDP remains active; a higher lesion can weaken that long flexor as well. This is the ulnar paradox.
Frequently asked questions
What are the roots of the ulnar nerve?
Mainly C8-T1 through the medial cord, with a variable C7 contribution.
What muscles does the ulnar nerve supply?
FCU and the ulnar FDP portion; most intrinsic hand muscles, including hypothenar muscles, interossei, lumbricals 3-4, adductor pollicis and usually deep FPB. Palmaris brevis receives the superficial branch.
What is the sensory distribution of the ulnar nerve?
Little finger and ulnar half of the ring finger, with adjacent medial palm and dorsal hand; exact boundaries and branch involvement vary.
What is the course of the ulnar nerve?
Descends medially in the arm, passes behind the medial epicondyle and between FCU heads, then enters Guyon's canal at the wrist.