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Medicine Phase 2a Neuro > Peripheral neuropathies > Flashcards

Peripheral neuropathies Flashcards

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
Q

Median nerve branch: Anterior interosseous nerve lesion clinical presentation

A

Weakness of lexion of the distal phalanx of the thumb and index finger

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26
Q

Nerve roots of ulnar nerve

A

C7-T1

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27
Q

Cause of ulnar nerve compression

A

Vulnerable to elbow trauma
Compression at the epicondylar groove or where nerve passes between 2 heads of flexor carpi ulnaris (cubital tunnel syndrome)

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28
Q

Signs of ulnar nerve compression

A

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

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29
Q

Treatment of ulnar nerve compression

A

Rest and avoiding pressure on the nerve

Night time soft elbow splinting may be required

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30
Q

Nerve roots of radial nerve

A

C5-T1

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31
Q

Causes of damage to radial nerve

A

Compression against the humerus

32
Q

Signs of damage to radial nerve

A

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
Q

Muscles affected from damage to radial nerve

A

Brachioradialis
Extensors
Supinator
Triceps

34
Q

Sensation felt from damage to brachial plexus

A

Pain/parathesiae and weakness in affected arm in a variable distribution

35
Q

Causes of brachial plexus damage

A 
Trauma
Radiotherapy e.g. for breast carcinoma
Prolonged wearing of a heavy rucksack
Neuralgic amyotrophy
Thoracic outlet compression (also affects vasculature)
36
Q

Nerve roots of phrenic nerve

A

C3, 4, 5

37
Q

Test of phrenic palsy

A

Orthopnoea (shortness of breath when lying flat) with raised hemidiaphragm on CXR

38
Q

Causes of phrenic palsy

A 
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
Q

Nerve roots of lateral cutaneous nerve (of the thigh)

A

L2-3

40
Q

Presentation of palsy of lateral cutaneous nerve (of the thigh)

A

Meralgia paraesthetica:

Antero-lateral burning thigh pain from entrapment under the inguinal ligament

41
Q

Nerve roots of sciatic nerve

A

L4-S3

42
Q

Cause of damage to sciatic nerve

A

Pelvic tumours or fractures to pelvis or femur

43
Q

Clinical presentation of damage to sciatic nerve

A

Affects hamstrings and all muscels below the knee - resulting in foot drop
Loss of sensation below the knee laterally

44
Q

Nerve roots of common peroneal nerve

A

L4-S1

Orginates from the sciatic nerve just above the knee

45
Q

Cause of damage to common peroneal nerve

A

Trauma or sitting cross-legged

damaged as it winds around the fibular head

46
Q

Signs of common peroneal nerve damage

A

Foot drop
Weak ankle dorsiflexion/eversion
Sensory loss over dorsum (top) of foot

47
Q

Nerve roots if tibial nerve

A

L4-S3

Originates from the sciatic nerve just above the knee

48
Q

Clinical presentation of tibial nerve damage

A

Inability to stand on tiptoe (plantarflexion), invert the foot or flex the toes
Sensory loss over the sole

49
Q

Describe polyneuropathies

A

Disorders of peripheral or cranial nerves, whose distribution is symmetrical and widespread
Distal weakness and sensory loss

50
Q

Classification of polyneuropathies

A

By course - acute or chronic
By function - sensory, motor, autonomic or mixed
By pathology - demyelination, axonal degeneration or both

51
Q

Example of polyneuropathies (state is mostly motor or sensory)

A 
-Mostly motor:
Guillain-Barre syndrome
Lead poisoning
Charcot-Marie-Tooth syndrome
-Mostly sensory:
Diabetes mellitus
Renal failure
Leprosy
52
Q

Describe classification of Guillain-Barre syndrome

A

An cute, predominantly motor, demyelinating neuropathy whereas chronic alcohol abuse leads to a chronic, initially sensory then mixed, axonal neuropathy

53
Q

Types of causes of polyneuropathies

A 
Metabolic
Vasculitides
Malignancy
Inflammatory
Infections
Nutritional
Inherited syndromes
Drugs/toxins
54
Q

Metabolic causes of polyneuropathies

A

Diabetes mellitus, Renal failure, Hypothyroidism, Hypoglycaemia

55
Q

Vasculitides causes of polyneuropathies

A

Polyarteritis nodosa
Rheumatoid arthritis
Wegeners granulamatosis

56
Q

Malignancy causes of polyneuropathies

A

Paraneoplastic syndromes

Polycythaemia rubra vera

57
Q

Inflammatory causes of polyneuropathies

A

Guillain-Barre syndrome

Sarcoidosis

58
Q

Infectious causes of polyneuropathies

A

Leprosy
HIV
Syphilis
Lyme disease

59
Q

Nutritional causes of polyneuropathies

A

Decreased:
Vitamins B12; B1; E; B6
Folate

60
Q

Inherited polyneuropathies

A

Charcot-marie-tooth

Porphyria

61
Q

Drugs/toxins that can cause polyneuropathies

A 
Lead
Arsenic
Alcohol
Vincritstine
Cisplatin
Metronidazole
62
Q

Diagnosis of polyneuropathy

A

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
Q

Diagnosis of polyneuropathy - what is likely cause if the was diarrhoea and vomiting before admission

A

Guillain-Barre syndrome

64
Q

Diagnosis of polyneuropathy - what is likely cause if the patient present with weight loss

A

Cancer

65
Q

Diagnosis of polyneuropathy - what is likely cause if patient presents with arthralgia

A

Connective tissue disorder

Arthralgia = pain in a joint

66
Q

Clinical presentation of Sensory neuropathy

A

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
Q

Clinical presentation of Motor neuropathy

A

Often progressive
Weak or clumsy hands
Difficulty walking e.g. fals and stumbling
Difficulty breathing e.g. reduced vital capacity
LMN lesion

68
Q

Cause of brainstem problems

A
  • Tumour
  • MS
  • Trauma
  • Aneurysm
  • Vertebral artery dissection resulting in infarction
  • Infection - cerebellar abscess from ear
69
Q

Describe LMN neuropathy presentation

A

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
Q

Causes of autonomic neuropathies

A 
Sympathetic and parasympathetic neuropathies may be isolated or part of a generalised sensorimotor peripheral neuropathy
DM
Guillain- Barre Syndrome
Sjogrens syndrome
HIV
SLE
71
Q

Clinical presentation of sympathetic neuropathy

A

Postural hypotension - faints on standing, eating or hot bath
Ejaculatory failure - Shoot
Reduced sweating

72
Q

Clinical presentation of parasympathetic neuropathy

A

Erectile dysfunction - Point
Constipation
Nocturnal diarrhoea
Urine retention

73
Q

Diagnosis of polyneuropathy

A

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
Q

What does ESR stand for?

A

Erythrocyte sedimentation rate

75
Q

Treatment of Polyneuropathy

A

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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