Nerve Injuries Flashcards
What is the MRC classification used for? Describe it
For assessing the power of a particular muscle group: 5 - normal power 4 - weakness 3 - movement against gravity 2 - movement with gravity eliminated 1 - flicker of muscle 0 - no detectable movement
What is Erb’s palsy?
Lesion of the upper brachial plexus (C5/C6) at birth
- Abductors and external rotators are paralysed
- ‘Waiter’s tip’ position: arm held close to body, internally rotated
- Loss of sensation to C5/C6 dermatomes
What is Klumpke paralysis?
Lesion of the lower brachial plexus (C8/T1) - rare
- Loss of intrinsic muscles of hand
- Claw hand
- Loss of sensation in C8/T1 dermatomes
Describe the functions of the radial nerve
Origin: posterior cord of brachial plexus (C5-C8)
Motor to: extensors of elbow, wrist, and fingers
Sensory to: dorsal aspect of lateral 3 1/2 digits; specifically area between 1st and 2nd MCPJs
Describe the causes and pattern of injury to the radial nerve at the axilla
- Saturday night palsy
- Crutch palsy
Motor deficit:
- Loss of extension of forearm (triceps)
- Weakness of supination
- Loss of extension of hands and fingers - ‘wrist drop’
Sensory deficit:
- Lateral arm
- Posterior forearm
- Dorsal aspect of lateral 3 1/2 digits
Describe the causes and pattern of injury to the radial nerve at the mid-arm
- Mid-shaft humeral fracture (where nerve travels in radial groove)
- Prolonged tourniquet time
Motor deficit:
- Triceps function spared
- Weakness of supination
- Loss of extension of hands and fingers - ‘wrist drop’
Sensory deficit:
- Posterior forearm
- Dorsal aspect of lateral 3 1/2 digits
Describe the causes and pattern of injury to the radial nerve just below the elbow
- Fractures around elbow or forearm
- Tight cast
- Rheumatoid nodules
- Injections due to tennis elbow
- Posterior interosseous nerve syndrome
Motor deficit:
- Weakness of extension of hands and fingers
- Finger drop, partial wrist drop, and radial wrist deviation on extension (since the extensor carpi radialis longus and brachioradialis muscles are working)
Sensory deficit:
- None, as sensation is supplied by the superficial radial nerve
Describe the causes and pattern of injury to the radial nerve in the distal forearm
- Wartenburg’s syndrome
- Tight jewellery
Motor deficit: none
Sensory deficit:
- Numbness and tingling in radial half of dorsum of hand and dorsal aspect of lateral 3 1/2 digits
What is Wartenburg’s syndrome? What condition does it closely resemble? Which test may be positive
Radial nerve palsy due to nerve entrapment beneath the tendinous insertion of brachioradialis.
There is significant radial wrist pain, and close resemblance to symptoms in de Quervain’s tenosynovitis. Finkelstein’s test may be positive.
What is posterior interosseous nerve entrapment?
Compression of the deep motor branch of the radial nerve due to entrapment at the Arcade of Frohse (part of the Supinator).
Posterior interosseous neuropathy is purely a motor syndrome resulting in finger drop, and radial wrist deviation on extension.
What is Saturday night palsy?
From falling asleep with one’s arm hanging over the arm rest of a chair, compressing the radial nerve at the spiral groove.
Motor deficit:
- Loss of extension of forearm (triceps paralysis)
- Weakness of supination
- Loss of extension of hands and fingers - ‘wrist drop’
Sensory deficit:
- Lateral arm
- Posterior forearm
- Dorsal aspect of lateral 3 1/2 digits
What is the cause of a ‘claw-like hand’?
Damage to the ulnar nerve usually occurs at the elbow or the wrist.
What does the ulnar nerve supply?
The ulnar nerve supplies all of the interossei, half of the flexor digitorum profundus (FDP) and the lumbricals to the ring and little fingers.
Describe the ulnar paradox
A lesion at the wrist causes unopposed action of the extensors and the FDP, especially of the little and ring fingers, causing them to claw (the FDP is supplied just below the elbow and so a cut at the level of the wrist will not paralyse this).
Lesions at the elbow often have less clawing, since the ulnar half of FDP is now paralysed and the fingers are therefore straighter.
List the causes of a true claw hand
- Volkman’s contracture
2. Proximal lesions of the brachial plexus
What is the difference between ulnar claw and hand of Benediction?
Ulnar claw:
- Lesion of ulnar nerve at wrist
- Paralysis of medial two lumbricals
- Unopposed extension at MCPJs
- Unopposed flexion at IPJs
Hand of Benediction:
- Lesion of medial nerve at elbow or wrist
- Paralysis of lateral half of FDP and lateral two lumbricals
- Inability to perform flexion at MCPJs and IPJs of index and middle finger
- Apparent when patient asked to make fist
How can ulnar nerve function be tested?
Froment’s test:
Ask patient to grip a piece of paper between thumb and index finger of a closed fist
+ve Froment’s sign: patient flexes DIPJ using flexor pollicis (supplied by median nerve) rather than adductor pollicis to grip paper
Describe the functions of the ulnar nerve
Motor to: • Medial two lumbricals • Adductor pollicis brevis • Interossei • Hypothenar eminence: abductor digiti minimi, flexor digiti minimi • Flexor carpi ulnaris • Ulnar part of FDP
Sensory to: medial 1½ fingers
What signs in the hand indicate ulnar nerve palsy?
- Loss of sensation to medial 1 1/2 fingers
- Interossei wasting on dorsum of hand
- Weakness of finger abduction and adduction
- Claw hand - more severe in distal lesions
- Radial deviation of wrist
What muscles does the median nerve supply?
First two lumbricals and thenar eminence: L - lumbricals (medial two) O - opponens pollicis A - abductor pollicis brevis F - flexor pollicis brevis
What is carpel tunnel syndrome?
Compression of the median nerve as it passes under the flexor retinaculum
List 5 conditions associated with carpal tunnel syndrome
Associations:
- Pregnancy
- Rheumatoid arthritis
- Hypothyroidism
- Acromegaly
- Trauma
More common in females - most commonly idiopathic in menopausal women
How does carpal tunnel syndrome typically present?
- Pain and numbness in median nerve distribution
- Worse at night
- Relieved by skating hands
- Triggered by activities that increase compression, e.g. prolonged flexion of wrist (typing, knitting) - Weakness and wasting of muscle of thenar eminence (late sign)
What is the distribution of pain and sensory deficit with carpal tunnel syndrome?
- Pain and paraesthesia in median nerve distribution
2. Sparing of small patch of skin over thenar eminence - supplied by superficial branch of median nerve
What test is useful in diagnosing carpel tunnel syndrome?
Tinnel’s test - tapping median nerve at wrist to reproduce symptoms
List the differentials of pain and tingling in a median nerve distribution
- Carpal tunnel syndrome
- Cervical rib
- Spondylosis (C6/C7)
How can diagnosis of carpal tunnel syndrome be confirmed?
EMG studies across wrist - shows delayed conduction of nerve impulses
How is carpal tunnel syndrome treated?
Mild cases - conservative Rx
- Splints
- Local steroid injections
Symptomatic cases with reduces nerve conduction
1. Surgical decompression by division of flexor retinaculum
Pain will improve, however numbness and wasting may not
What is Dupuytren’s contracture?
A disorder where there is fibrosis and thickening of the palmar fascia.
- Begins as single nodule
- Later bands of thickened tissue which may adhere to skin
- Progressive contracture - usually ring, then little, then all fingers fully flexed
Can be bilateral
Feet may be affected
What are the risk factors for Dupuytren’s contracture?
- Male gender
- Middle to elderly age
- Heredity (AD inheritence)
- Alcohol
- Drugs, e.g. phenytoin
- Cirrhosis
- Diabetes
How is Dupuytren’s contracture treated?
Operative
- Fasciectomy
+/- skin graft
Condition often recurs
What is the differential diagnosis for a fixed flexed finger?
- Dupuytren’s contracture
- Trigger finger
- Skin contracture (old laceration, scar or burn)
What is a ganglion and where is it most commonly seen?
A cystic swelling, most commonly seen on dorsum of wrist.
Possibly due to cystic mucoid degeneration of joint capsule or tendon sheath
A patient presents with a painless lump at the back of the wrist which frequently catches on watches and clothing. What is your differential diagnosis?
1. Ganglion NB: they can be painful! 2. Lipoma 3. Fibroma 5. Sebaceous cyst
How would you treat a ganglion?
- Aspiration and injection with hydrocortisone (commonly recurs)
- Surgical excision
