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Ulnar Nerve Palsy
· Rule out median, radial and brachial neuritis
· Wasting of the muscles of the hands, hypothenar eminence and partial clawing of the 4th and 5th fingers, sparing of the thenar eminence, ulnar paradox
· Proceed to tests for finger abduction and Froment’s sign (weakness of the adduction of the thumb)
· Test finger flexion of the 5th finger for flexor digitorum profundus involvement; test for wrist flexion at the ulna side and look for the tendon of the flexor carpi ulnaris
· Rule out median nerve (thenar eminence and ext rot thumb, pen touch test and Oschner clasping test) and radial nerve
· Sensory testing in the medial 1 ½ fingers; test T1 sensory loss
· Examine the wrist and elbows (feel for thickened nerve, wide carrying angle))
· Thickened nerve (cf with Pb for radial and Acromeg etc for median)
Sir, this patient has got a isolated left ulnar palsy as evidenced by a left ulnar claw hand with wasting of the small muscles of the hands with dorsal guttering as well as wasting of the hypothenar eminence. There is sparing of the thenar eminence.
There is weakness of finger abduction and Froment’s sign is positive. There is preservation of the flexion of the DIPJ of the 4th and 5th fingers; when the hand is flexed to the ulna side against resistance, the tendon of the flexor carpi ulnaris is palpable. This is associated with reduced sensation to pinprick in the medial 1/1/2 fingers. There are no associated median or radial nerve palsies and T1 involvement.
In terms of aetiology, there is a scar at the wrist associated with a marked ulnar claw hand, demonstrating the ulna paradox. I did not find any signs to suggest leprosy such as thickened nerves, hypopigmentation patches or finger resorption.
Both coarse and fine motor function of the hand is preserved.
In summary, this patient has a left ulna claw hand due to a traumatic injury to the left wrist.
What is the anatomical course of the ulnar nerve?
· It provides motor to all muscles of the hands except the LOAF; flexor carpi ulnaris and flexor digitorum profundus to the 4th and 5th fingers.
· Sensory to the ulna 1 ½ fingers
· Begins from the medial cord of the brachial plexus (C8 and T1)
· No branches in the arm
· Enters the forearm via the cubital tunnel (medial epicondyle and the olecranon process) and motor supply to the flexor carpi ulnaris and ulna half of the flexor digitorum profundus
· It gives off a sensory branch just above the wrist and enters Guyon’s canal and supplies the sensory medial 1½ fingers and hypothenar as well as motor to all intrinsic muscles of the hands except LOAF.
What is the level of lesions and its clinical correlation?
· Wrist – Hypothenar eminence wasting, Froment’s positive, weakness of finger abduction, pronounced claw and loss of sensation
· Elbow – less pronounced claw and loss of terminal flexion of the DIPJ and loss of flexor carpi ulnaris tendon on ulna flexion of the wrist
How do you differentiate ulnar nerve palsy vs a T1 lesion?
Motor – wasting of the thenar eminence in addition for T1
Sensory – loss in T1 dermatomal distribution
What is the ulna claw hand?
It refers to the hyperextension of the 4th and 5th MCPJ associated with flexion of the IPJs of the 4th and 5th fingers as a result of ulnar nerve palsy.
It is due to the unopposed long extensors of the 4th and 5th fingers in contrast to the IF and MF which are counteracted by the lumbricals which are served by the median nerve.
What is the ulnar paradox?
It means that the ulnar claw deformity is more pronounced for lesions distally e.g. at the wrist as compared to a more proximal lesion e.g. at the elbow.
This is because a more proximal lesion at the elbow also causes weakness of the ulnar half of the flexor digitorum profundus, resulting in less flexion of the IPJs of the 4th and 5th fingers.
What is Froment’s sign?
Patient is asked to grasp a piece of paper between the thumbs and the lateral aspect of the index finger. The affected thumb will flex as the adductor pollicis muscles are weak. (Patient is trying to compensate by using the flexor pollicis longus supplied by median nerve)
What are the causes of an ulnar nerve palsy?
· Compression or entrapment (Cubital tunnel at the elbow and Guyon’s canal at the wrist)
· Trauma (Fractures or dislocation – cubitus valgus leads to tardive ulnar nerve palsy)
· Mononeuritis multiplex
· Infection – leprosy
· Ischaemia – Vasculitis
· Inflammatory - CIDP
How would you investigate?
· Blood Ix to rule out DM if no obvious cause
· X-rays of the elbow and wrist (both must be done to rule out double crush syndrome) (KIV C-spine and CXR)
· EMG(axonal degeneration for chronic) and NCT(motor and sensory conduction velocities useful for recent entrapment as well as chronic) to locate level and monitor
How would you manage?
· Education and avoidance of resting on elbow
· OT, PT
· Medical – NSAIDs and Vit B6
· Surgical decompression with anterior transposition of the nerve
NB: LOAF – lateral 2 lumbricals, opponens pollicis, abductor pollicis brevis and flexor pollicis brevis