How to differentiate high ulnar nerve palsy versus low ulnar nerve palsy?
Answers
Hello
- brachial plexus:
- C8 and T1 nerve roots give rise to the medial cord which in turn, forms the ulnar nerve;
- ulnar nerve passes distally, just medial to axillary artery, pierces medial intermuscular septum halfway down the arm, passes back over
medial head of triceps, around posterior aspect of medial epicondyle, & enters forearm between two heads of FCU;
- anatomy and sites of compression in the cubital tunnel:
- just below elbow, it sends branches to FCU & ulnar half of FDP;
- it passes down forearm under FCU , & then into Guyon's canal;
- dorsal sensory branch:
- the nerve emerges from the medial border of the FCU about 5 cm proximal to the pisiform;
- supplies dorsoulnar aspect of the hand and the ulnar 1 1/2 fingers;
- terminal branches in the hand:
- guyon's canal:
- superficial cutaneous branch to ulnar portion of palm & volar surfaces of ulnar 1 1/2 fingers,
- deep motor branch passes adjacent to hook of hamate;
- deep branch, innervating hypothenar muscles & third & fourth lumbricales, adductor pollicis, all interossei, & deep head of FPB;
- references:
- The lateral root of the ulnar nerve.
- General Orthopaedics: The Anatomy of the Distal Ulnar Tunnel.
- The Dorsal Branch of the Ulnar Nerve: An Anatomic Study.
- Palmar cutaneous branch of the ulnar nerve.
- Distribution pattern of the deep branch of the ulnar nerve in the hypothenar eminence.
- A Neural Loop of the Deep Motor Branch of the Ulnar Nerve: An Anatomic Study.
- A variation in the path of the deep motor branch of the ulnar nerve at the wrist.
- Trauma to Ulnar Nerve: (see: nerve repair)
- combined lesions of the median and ulnar nerves:
- high ulnar nerve lesions
- low ulnar nerve injury
- division of ulnar nerve at wrist results in paralysis of all small muscles of hand except first & second lumbricales & most of thenar muscles;
- paralysis of adductor pollicis produces Froment's sign;
- when grasping piece of paper between thumb and index finger, FPL fires (IP joint flexion) since adductor does not work;
- if ulnar nerve is divided below mid-forearm, ulnar claw hand is produced; (low ulnar nerve lesions);
- w/ this lesion, 4th & 5th fingers are hyperextended at MP joints by long extensors but flexed at interphalangeal joints;
- this posture is sometimes called hand of benediction;
- if ulnar nerve lesion is above midforearm, clawing of ulnar two fingers does not occur, because extrinsic
muscles producing IP joint flexion are also denervated (see high ulnar nerve lesion);
- in complete claw hand, produced by low lesion of median nerve & ulnar nerves, MP joints are
extended & interphalangeal joints flexed by still-functional extrinsics;
- references:
- Repair of median and ulnar nerves. Primary suture is best.
- Epiperineurium-fascial stitches along the stumps of a transected nerve. An additional method for closing the gap in the nerve trunk.
- Experience with the free vascularized ulnar nerve graft in repair of supraclavicular lesions of the brachial plexus.
- The results of secondary microsurgical repair of ulnar nerve injury.
- Cubital Tunnel Syndrome:
- w/ severe cases of cubital tunnnel syndrome, there will be decreased two point sensory distribution of ulnar nerve
as well as muscle weakness and/or muscle wasting of intrinsic innervated by the ulnar nerve;
- clinical findings include positive Froment's test, wasting of first dorsal interosseous muscle, inability to
cross index and middle fingers, & clawing of ring & small fingers;
It is useful for you. ....