Clinical Testing- Ulnar nerve Dr.Roopchand.PS Senior Resident Academics Department of Neurology
Introduction:• A mixed nerve.• Main branch of the medial cord of the brachial plexus.• Root value is C7 C8 T1• Main supply to the small muscles of hand.• Also called musicians nerve.
• ARM – crosses the axilla beneath the pectoralis minor – medial to the brachial artery in upper arm – distal arm it enters a groove between the medial humeral epicondyle and the olecranon process. – The cubital tunnel: Aponeurosis between the olecranon and medial epicondyle forms the roof of an osseous fibrous canal the floor of which is formed by the medial ligament of the elbow joint.
• ELBOW: – passes between the humeral and ulnar heads of the flexor carpi ulnaris to rest on the flexor digitorum profundus. – Immediately distal to the elbow joint • Br to flexor carpi ulnaris • Br to flexor digitorum profundus III and IV• FOREARM: – descends beneath the flexor carpi ulnaris – palmar cutaneous branch at distal forearm – supplies the skin over the hypothenar eminence.
– then gives of dorsal cutaneous branch. – supplies the dorsal ulnar aspect of the hand and the dorsal aspect of the 5th finger and half of the 4th finger.• WRIST: – enters the wrist lateral to the tendon of the flexor carpi ulnaris muscle. – gives of the superficial terminal branch – skin of the distal part of the ulnar aspect of the palm and the palmar aspect of the fifth and half of the 4th finger. – passes between the pisiform carpal bone medially and the hook of the hamate carpal bone laterally: canal of Guyon
• Passes as deep muscular branch supplies: – Palmaris brevis (C8–T1). – Abductor digiti minimi (C8–Tl) – Opponens digiti minimi (C8–T1) – Flexor digiti minimi (C8–T1) – Lumbricals III and IV (C8–T1) – Interosseous muscles (C8–Tl) – Adductor pollicis (C8–T1) – Deep head of the flexor pollicis brevis (C8–Tl)
NERVE LESIONS:• Lesions above the Elbow: – May present as triad neuropathy. – sleeping with the arm hanging over a sharp edge or the head of a sleeping partner compressing the nerve against the humerus, crutches or tourniquets, arteriovenous fistulas in dialysis patients, aneurysms, hematomas, nerve tumors, and other masses. – Supracondylar fractures of the humerus – Ulnar entrapment neuropathy in the midarm: compression by the medial intermuscular septum
• “claw-hand”• Paresis or paralysis of the ulnar flexion• Impaired extension at the interphalangeal joints.• Impaired adduction and abduction of the second to 5th fingers.• Impaired abduction and opposition of the fifth finger.• Froment’s thumb sign : adductor pollicis weakness- proximal phalanx of the thumb is extended and the distal phalanx is flexed when a paper grasped between thumb and index finger is pulled.• Sensory abnormalities.
• Martin-Gruber anastomosis: a median-ulnar communication. – the crossing of fibers from the median to the ulnar nerve usually occurs 3 to 10 cm distal to the medial humeral epicondyle. – median fibers ultimately innervate the intrinsic hand muscles. – The overall incidence of Martin-Gruber anastomoses is approximately 17%. – Four types exsists.
• Cubital Tunnel Syndrome: lesion at the elbow – most commonly compressed at the elbow in the cubital tunnel. – Narrowing of tunnel during flexion, thickening of aponeurotic arch, ganglion cyst, mass lesions, fibrous bands, bony spurs… – More in patients with renal disease undergoing dialysis and during general anesthesia. – Tardy ulnar nerve palsy: ulnar nerve palsy occurring long after original injury. – A reliable sign of ulnar entrapment by the flexor carpi ulnaris muscle is the ulnar extension manoeuvre, in which increased paresthesias in the fourth and fifth digits follow 3 minutes of elbow and wrist flexion in ulnar deviation.
Cubital tunnel synd Vs tardy ulnar palsy:• No evidence of joint deformity or prior trauma• Frequent occurrence of bilateral symptoms and signs of ulnar neuropathy• A taut, palpably enlarged nerve in the ulnar groove• Electrophysiologic (electromyographic) localization to the cubital tunnel• Operative findings of a swollen, taut, hyperemic nerve, distally limited by the proximal border of the aponeurosis joining the two heads of the flexor carpi ulnaris muscle.
• Ulnar neuropathy at the elbow often spares the flexor carpi ulnaris• involvement of flexor carpi ulnaris more often correlates with the severity of the neuropathy.• Involvement related to the internal topography of the nerve, severity of compression, level of compression.• preferentially compress the nerve fascicle to distal hand muscles
• Lesions in the Forearm: – Causes: hypertrophied flexor carpi ulnaris muscle, fibrous and fibrovascular bands, hematomas, and handcuffs. – flexor carpi ulnaris and the flexor digitorum profundus iand II muscles are often spared
Lesions at the Wrist and in the Hand:• Flexor carpi ulnaris and the flexor digitorum profundus III and IV are spared.• Compression of the nerve as it enters the hand.• Compression of the proximal part of the terminal motor branch(with in Guyons canal)• Distal compression of the terminal motor br.
• Common causes: – Ganglion, occupational neuropathy, laceration, ulnar artery aneurysm, carpal bone fracture.• Palmaris brevis spasm syndrome: following the prolonged use of a computer mouse and keyboard.• Lesions of the Dorsal Cutaneous Branch of the Ulnar Nerve – Handcuff palsy, Pricer palsy• Pseudoulnar Nerve Palsy: isolated hand weakness apparently in an ulnar distribution that is due to• contralateral cerebral infarction in the white matter of the angular gyrus of the inferior parietal lobe