Peripheral Neuropathies & mononeuropathies Flashcards
Peripheral neuropathies that cause predominantly motor loss?
1) Guillain-Barre - demyelinating neuropathy
2) Diptheria - infective neuropathy
3) Lead poisoning - toxic neuropathy
4) Charcot-Marie-Tooth (hereditary sensorimotor neuropathy) - degenerative neuropathy
Peripheral neuropathies that cause predominantly sensory loss?
1) Diabetes - metabolic/infarctive neuropathy
2) Alcoholism - secondary to both direct toxic effects and reduced vitamin absorption; sensory symptoms typically present prior to motor symptoms - toxic neuropathy
3) Carpal Tunnel Syndrome - Compressive Neuropathy
4) Vitamin B12 deficiency
Clinical symptoms of a sensory neuropathy?
1) Numbness - pins and needles (burning?)
2) Affects extremities first (glove and stocking pattern)
3) Difficulty holding small objects
4) Signs of trauma - joint deformation or finger burns may indicate sensory loss
5) Diabetic and alcoholic neuropathy
Clinical symptoms of a motor neuropathy?
1) Often progressive - may be rapid
2) Weak or clumsy hands
3) Difficulty in walking - falls and stumbling
4) Difficulty in breathing - reduced vital capacity
What else do neuropathies present with?
LMN lesions:
1) Wasting and weakness most marked in the distal muscle of the hands and feet - foot or wrist drop
2) Reflexes are absent
What is a mononeuropathy?
- A process affecting a single nerve - lesions of individual peripheral or cranial nerves.
- Causes are usually local such as trauma, entrapment e.g. compression/tumour.
- Carpal tunnel syndrome is the most common mononeuropathy.
- Mononeuritis complex os used if 2 or more peripheral nerves are affected - when caused tend to be systemic - WARDS PLC:
1) Wegener’s granulomatosis
2) AIDS/Amyloid
3) Rheumatoid arthritis
4) Diabetes Mellitus
5) Sarcoidosis
6) Polyarteritis nodosa
7) Leprosy
8) Carcinoma
What is Carpal Tunnel Syndrome? Epidemiology?
- Most common mononeuropathy and entrapment neuropathy.
- Results from compression and pressure on the median nerve as it passes through the carpal tunnel in the wrist.
- More common in females than males as women have narrower wrists but similar sized tendons to men.
Aetiology of CTS?
1) Usually idiopathic
2) Usually over 30 years
3) Associated with: Hypothyroidism, amyloidosis, rheumatoid arthritis, Diabetes Mellitus, pregnancy (third trimester, obesity, acromegaly.
RISK FACTOR: DIABETES MELLITUS
Clinical presentation of CTS? Ddx?
1) Symptoms are intermittent and onset is gradual
2) Aching pain in hand and arm (bad at night can wake patient)
3) Paraesthesia - pins and needles in thumb, index, middle and ring fingers AND palm (median nerve distribution)
4) Relieved by dangling hand over edge of bed - ‘wake and shake’
5) May be sensory loss and weakness with thumb abductor, wasting in thenar eminence (muscles of thumb base)
6) Light touch, 2 point discrimination and sweating may be impaired
Ddx: MS, MND, peripheral neuropathy
Diagnosis of CTS?
1) Electromyography - See slowing of conduction velocity in median sensory nerves, prolongation of median distal motor latency, confirms lesion site and severity.
2) Phalen’s test - can only maximally flex wrists for 1 minute
3) Tinel’s test - tapping on nerve at wrist induces tingling (non-specific)
Treatment of CTS?
1) Wrist splint at night
2) Local steroid injection (HYDROCORTISONE)
3) Decompression surgery
Median nerve lesions? (C6-T1)
Median nerve is the nerve of precision grip - supplies 2LOAF: 2 Lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis.
Wrist lesions: Lacerations or CTS - weakness of abductor pollicis brevis (thumb abductor) and sensory loss over radial 3.5 fingers and palm.
Anterior interosseous nerve (medial nerve branch) lesion:
Due to trauma, weakness of flexion of the distal phalanx of thumb and index
Proximal lesions e.g. compression at elbow: May show combined defects
Ulner nerve lesion? (C7-T1)
- Vulnerable to elbow trauma
- Most often, compression occurs at the epicondylar groove or at the point where the nerve passes between the 2 heads of flexor carpi ulnaris (true cubital tunnel syndrome)
Presentation:
1) Weakness/wasting of: Medial wrist flexor, medial 2 lumbricals (claw hand), Interossei (cannot cross fingers)
2) Wasting of hypothenar eminence (base of little finger) + weak little finger abduction
3) Sensory loss over medial 1.5 fingers and ulnar side of hand
4) Flexion of 4th and 5th DIP joint is weak
5) With lesions at the wrist, claw hand is more marked
Treatment:
1) Rest and avoiding pressure on the nerve
2) Night time soft elbow splinting may be required
Radial nerve lesion? (C5-T1)
1) This nerve opens the fist
2) May be damaged by compression against humerus
Signs: Test for wrist and finger drop with elbow flexed and arm pronated
Sensory loss is variable - dorsal aspect of the root of the thumb (snuff box) is most reliably affected.
Muscles involved: Brachioradialis, Extensors, Supinator, Triceps (BEST)
Phrenic nerve lesions? (C3, 4, 5)
C3,4,5 keeps diaphragm alive!
Consider phrenic palsy is orthopnoea (SOB when lying flat) with raised hemidiaphragm on CXR.
Causes:
1) Lung cancer
2) Myeloma/thymoma
3) Cervical spondylosis/trauma
4) Multiple sclerosis
5) Thoracic surgery
6) C3-5 zoster
7) HIV
8) Muscular dystrophy
