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Peripheral neuropathies Flashcards

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1
Q

6 mechanisms that can cause nerve malfunction

A 
Demyelination
Axonal degeneration
Compression
Infarction
Infiltration
Wallerian degeneration
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2
Q

Describe demyelination

A

Schwann cell damage leads to myelin sheath disruption

Results in marked slowing of conduction seen for examples in Guillain- Barre syndrome

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3
Q

Describe axonal degeneration

A
  • Axon damage causes the nerve fibre to die back from the periphery
  • Conduction velocity initially remains mortal because axonal continuity is maintained in surviving fibres
  • Axonal degeneration typically occurs in toxic neuropathies
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4
Q

Describe compression as cause of nerve malfunction

A

Focal demyelination at the point of compression causes disruption of conduction
Typically occurs in entrapment neuropathies e.g. carpal tunnel syndrome

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5
Q

Describe infarction as cause of nerve malfunction

A

Micro-infarction of vasa nervorum occurs in diabetes and arteritis such as polyarteritis nodosa and eosinophilic granulomatosis with polyangitis

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6
Q

Describe infiltration as a cause of nerve malfunction

A

Infiltration occurs by inflammatory cells in leprosy and granulomas such as sarcoid and by neoplastic cells (cancer)

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7
Q

What is Wallerian degeneration

A

Process that results when a nerve fibre is cut or crash and the distal part of the axon that is separated from the neurone’s cell body degenerates

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8
Q

Define neuropathy

A

A pathological process affecting a peripheral nerve or nerves

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9
Q

Define mononeuropathy

A

Process affecting a single nerve

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10
Q

Define mononeuritis multiplex

A

Means that several individual nerves are affected

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11
Q

Define polyneuropathy and classification

A

Diffuse, symmetrical disease usually commencing peripheral
Can be motor, sensory, sensorimotor and autonomic
Classified into demyelinating and axonal types
Widespread loss of tendon reflexes is typical, with distal weakness and distal sensory loss

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12
Q

Causes of mononeuritis multiplex

A 
WARDS PLC
Wegener’s granulomatosis 
Aids/Amyloid
Rheumatoid arthritis 
Diabetes mellitus 
Sarcoidosis
Polyarteritis nodosa 
Leprosy
Carcinoma
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13
Q

What is the most common mononeuropathy

A

Carpal Tunnel Syndrome

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14
Q

Pathophysiology of carpal tunnel syndrome

A

Pressure and compression on the median nerve as it passes through the carpal tunnel in the wrist

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15
Q

Epidemiology of carpal tunnel s

A

More in females as have narrower wrists (but smaller sized tendons)

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16
Q

Aetiology of carpal tunnel s

A

Usually idiopathic
>30 years old
Associated with:
Hypothyroidism, DM (risk factor), Pregnancy, amyloidosis, obesity, rheumatoid arthritis, acromegaly

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17
Q

Clinical presentation of carpal tunnel syndrome

A

Symptoms are intermittent and onset is gradual
Aching pain in the hand and arm (especially at NIGHT) - can wake patient up
Paraesthesiae (tingling or prickling) in thumb, index, middle & 1/2 ring fingers + palm (median nerve distribution)

Relieved by dangling the hand over the edge of the bed - “wake and shake”

  • May be sensory loss and weakness of abductor pollicis brevis (thumb abductor) +/- wasting of the thenar eminence (muscles at the base of thumb)
  • Light touch, 2-point discrimination and sweating may be impaired
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18
Q

Diagnosis of CTS

A

Electromyography (EMG)
Phalen’s test
Tinel’s test

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19
Q

What is seen in an electromyography in diagnosis of CTS

A

See slowing of conduction velocity in the median sensory nerves across the carpal tunnel
Prolongation of median distal motor latency
Helps confirm lesion site and severity

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20
Q

What is Phalen’s test

A

Patient can only maximally flex wrist for 1 minute

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21
Q

What is Tinels test

A

Tapping on the nerve at the wrist induces tingling - but non-specific

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22
Q

Treatment of CTS (CMS)

A 
Wrist splint at night
Local steroid injection
Decompression surgery (carpal tunnel ligament is cut to reduce pressure)
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23
Q

Spinal roots of median nerve

A

C6-T1

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24
Q

What muscles are supplied by the median nerve

A 
LOAF
2 Lumbricals
Opponens pollicis
Abductor pollicis brevis
Flexor pollicis brevis
(nerve of percision grip)
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25
Median nerve branch: Anterior interosseous nerve lesion clinical presentation
Weakness of lexion of the distal phalanx of the thumb and index finger
26
Nerve roots of ulnar nerve
C7-T1
27
Cause of ulnar nerve compression
Vulnerable to elbow trauma Compression at the epicondylar groove or where nerve passes between 2 heads of flexor carpi ulnaris (cubital tunnel syndrome)
28
Signs of ulnar nerve compression
Weakness/wasting of medial wirst flexors, interossei, medial 2 lumbricals Wasting of hypothenar eminence (base of little finger) thus weak little finger abduction Sensory loss over medial (ulnar) 1.5 fingers and ulnar side of hand Flexion of 4th and 5th DIP joint is weak
29
Treatment of ulnar nerve compression
Rest and avoiding pressure on the nerve | Night time soft elbow splinting may be required
30
Nerve roots of radial nerve
C5-T1
31
Causes of damage to radial nerve
Compression against the humerus
32
Signs of damage to radial nerve
Test for wrist and finger drop with elbow flexes and arm pronated Sensory loss is variable (dorsal aspect of the root of the thumb most reliably affected)
33
Muscles affected from damage to radial nerve
Brachioradialis Extensors Supinator Triceps
34
Sensation felt from damage to brachial plexus
Pain/parathesiae and weakness in affected arm in a variable distribution
35
Causes of brachial plexus damage
``` Trauma Radiotherapy e.g. for breast carcinoma Prolonged wearing of a heavy rucksack Neuralgic amyotrophy Thoracic outlet compression (also affects vasculature) ```
36
Nerve roots of phrenic nerve
C3, 4, 5
37
Test of phrenic palsy
Orthopnoea (shortness of breath when lying flat) with raised hemidiaphragm on CXR
38
Causes of phrenic palsy
``` Lung cancer Myeloma Thymoma (tumour of thymus) Cervical spondylosis/trauma Phrenic nucleus lesion e.g. MS Thoracic surgery C3-5 zoster HIV Muscular dystrophy ```
39
Nerve roots of lateral cutaneous nerve (of the thigh)
L2-3
40
Presentation of palsy of lateral cutaneous nerve (of the thigh)
Meralgia paraesthetica: | Antero-lateral burning thigh pain from entrapment under the inguinal ligament
41
Nerve roots of sciatic nerve
L4-S3
42
Cause of damage to sciatic nerve
Pelvic tumours or fractures to pelvis or femur
43
Clinical presentation of damage to sciatic nerve
Affects hamstrings and all muscels below the knee - resulting in foot drop Loss of sensation below the knee laterally
44
Nerve roots of common peroneal nerve
L4-S1 | Orginates from the sciatic nerve just above the knee
45
Cause of damage to common peroneal nerve
Trauma or sitting cross-legged | damaged as it winds around the fibular head
46
Signs of common peroneal nerve damage
Foot drop Weak ankle dorsiflexion/eversion Sensory loss over dorsum (top) of foot
47
Nerve roots if tibial nerve
L4-S3 | Originates from the sciatic nerve just above the knee
48
Clinical presentation of tibial nerve damage
Inability to stand on tiptoe (plantarflexion), invert the foot or flex the toes Sensory loss over the sole
49
Describe polyneuropathies
Disorders of peripheral or cranial nerves, whose distribution is symmetrical and widespread Distal weakness and sensory loss
50
Classification of polyneuropathies
By course - acute or chronic By function - sensory, motor, autonomic or mixed By pathology - demyelination, axonal degeneration or both
51
Example of polyneuropathies (state is mostly motor or sensory)
``` -Mostly motor: Guillain-Barre syndrome Lead poisoning Charcot-Marie-Tooth syndrome -Mostly sensory: Diabetes mellitus Renal failure Leprosy ```
52
Describe classification of Guillain-Barre syndrome
An cute, predominantly motor, demyelinating neuropathy whereas chronic alcohol abuse leads to a chronic, initially sensory then mixed, axonal neuropathy
53
Types of causes of polyneuropathies
``` Metabolic Vasculitides Malignancy Inflammatory Infections Nutritional Inherited syndromes Drugs/toxins ```
54
Metabolic causes of polyneuropathies
Diabetes mellitus, Renal failure, Hypothyroidism, Hypoglycaemia
55
Vasculitides causes of polyneuropathies
Polyarteritis nodosa Rheumatoid arthritis Wegeners granulamatosis
56
Malignancy causes of polyneuropathies
Paraneoplastic syndromes | Polycythaemia rubra vera
57
Inflammatory causes of polyneuropathies
Guillain-Barre syndrome | Sarcoidosis
58
Infectious causes of polyneuropathies
Leprosy HIV Syphilis Lyme disease
59
Nutritional causes of polyneuropathies
Decreased: Vitamins B12; B1; E; B6 Folate
60
Inherited polyneuropathies
Charcot-marie-tooth | Porphyria
61
Drugs/toxins that can cause polyneuropathies
``` Lead Arsenic Alcohol Vincritstine Cisplatin Metronidazole ```
62
Diagnosis of polyneuropathy
History - clear on time course, symptoms and any preceding or associated events Ask on travel, alcohol and drug use, sexual infections and family history Nerve thickening (that is palpable) Examine other systems (e.g. alcoholic liver disease)
63
Diagnosis of polyneuropathy - what is likely cause if the was diarrhoea and vomiting before admission
Guillain-Barre syndrome
64
Diagnosis of polyneuropathy - what is likely cause if the patient present with weight loss
Cancer
65
Diagnosis of polyneuropathy - what is likely cause if patient presents with arthralgia
Connective tissue disorder | Arthralgia = pain in a joint
66
Clinical presentation of Sensory neuropathy
Numbness (pin and needles) Affects extremities 1st Difficulty handling small objects such as buttons Signs of trauma (e.g. finger burns or joint deformity) Diabetic and alcohol neuropathies - painful
67
Clinical presentation of Motor neuropathy
Often progressive Weak or clumsy hands Difficulty walking e.g. fals and stumbling Difficulty breathing e.g. reduced vital capacity LMN lesion
68
Cause of brainstem problems
- Tumour - MS - Trauma - Aneurysm - Vertebral artery dissection resulting in infarction - Infection - cerebellar abscess from ear
69
Describe LMN neuropathy presentation
Wasting and weakness is most marked in the distal muscle of the hands and feet - foot or wrist drop Reflexes are reduced or absent
70
Causes of autonomic neuropathies
``` Sympathetic and parasympathetic neuropathies may be isolated or part of a generalised sensorimotor peripheral neuropathy DM Guillain- Barre Syndrome Sjogrens syndrome HIV SLE ```
71
Clinical presentation of sympathetic neuropathy
Postural hypotension - faints on standing, eating or hot bath Ejaculatory failure - Shoot Reduced sweating
72
Clinical presentation of parasympathetic neuropathy
Erectile dysfunction - Point Constipation Nocturnal diarrhoea Urine retention
73
Diagnosis of polyneuropathy
FBC, ESR (, glucose, U&E, LFT, TSH, B12 ANA (antinuclear antibodies), ANCA (Antineutrophil cytoplasmic antibody), anti-CCP (Anti-cyclic citrullinated peptide) CXR Urinalysis Lumbar puncture and specific gene testing for inherited neuropathies
74
What does ESR stand for?
Erythrocyte sedimentation rate
75
Treatment of Polyneuropathy
Treat the cause Foot care and shoe choices (important in sensory neuropathies to minimise trauma) Splinting of joints (help prevent contractures in prolonged paralysis) For vasculitic causes - steroids/immunosuppressants may help Treat neuropathic pain with Oral Amitriptyline

Medicine Phase 2a Neuro (28 decks)

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