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stage 3 > Neurology: Nerve palsies and neuropathies > Flashcards

Neurology: Nerve palsies and neuropathies Flashcards

1
Q

What is the most common cause of facial nerve palsy?

A

Bell’s palsy (idiopathic syndrome)

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2
Q

What are the four groups of differential diagnoses for facial nerve palsy?

A

1) Central nerve
2) Peripheral
3) Neuromuscular
4) Muscular

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3
Q

How would central nerve (UMN) facial nerve palsy present and why?

A

Forehead sparing weakness - the upper part of the face is bilaterally represented cortically

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4
Q

What are other causes of peripheral facial nerve palsy/disease besides Bell’s palsy?

A

1) Acoustic neuroma (physical lesions of the cerebellopontine angle)
2) Basal meningitis
3) Ramsay hunt syndrome
4) Trauma
5) Diseases of the middle/inner eat
6) Mononeuritis multiplex

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5
Q

Which tumour can cause facial nerve palsy?

A

Acoustic neuroma (any physical lesions of the cerebellopontine angle)

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6
Q

What can cause bilateral facial nerve palsy?

A

Basal meningitis - infective or inflammatory causes including Lyme disease and sarcoidosis

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7
Q

What is Ramsay Hunt syndrome?

A

Herpes zoster of the facial nerve causing facial nerve palsy and skin/ear lesions and pain

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8
Q

Diseases of which organ can cause facial nerve palsy?

A

Middle/inner ear

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9
Q

How would neuromuscular and muscular mimics of facial nerve palsy be different from true nerve weakness?

A

Often bilateral and associated with weakness elsewhere

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10
Q

Which cranial nerves are located in the midbrain?

A

CN 1, 2, 3, 4

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11
Q

Which cranial nerves are located in the pons?

A

CN 5, 6, 7, 8

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12
Q

Which cranial nerves are located in the medulla?

A

CN 9, 10, 11, 12

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13
Q

What are the key features of Horner’s syndrome?

A

Ptosis, meiosis ± anhidrosis

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14
Q

What causes Horner’s syndrome?

A

Interruption of the sympathetic nerve supply to the eye

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15
Q

What are the types of causes of Horner’s syndrome?

A

1) Pre-ganglion causes
2) Post ganglionic causes
3) Central causes

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16
Q

What are three causes of Horner’s syndrome?

A

1) Pancoast tumour - affecting sympathetic nerve supply
2) Stroke
3) Carotid artery dissection

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17
Q

What is a red flag for carotid artery dissection?

A

Neck pain ± Horner’s syndrome

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18
Q

How does a surgical CN III palsy present?

A

1) Ipsilateral fixed dilated pupil (responds poorly to light)
2) Ipsilateral ophthalmoplegia with the classic down and out appearance (pupil in inferotemporal position) + ptosis
3) Pain - bc of underlying cause

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19
Q

What is a most common cause of a surgical CN III palsy?

A

Posterior communicating artery aneurysm

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20
Q

What is an Argyll-Robertson pupil and what condition is it associated with?

A

Small and irregular pupils bilaterally that do not respond to light but accommodation reflexes are intact - neurosyphilis (could also have poor balance due to tabes dorsalis)

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21
Q

How would opiate overdose present?

A

1) Bilateral miosis
2) Respiratory depression
3) Altered mental status

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22
Q

What is internuclear ophthalmoplegia?

A

Ocular movement disorder caused by a lesion of the medial longitudinal fasciculus blocking the connection between the contralateral sixth nerve nucleus and the ipsilateral third nerve nucleus

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23
Q

What does internuclear ophthalmoplegia cause?

A

Impaired horizontal gaze/double vision:
1) Ipsilateral impaired adduction in the eye
2) Contralateral nystagmus in the abducting eye
- Some patients may converge to a near target

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24
Q

What are the two most common causes of internuclear ophthalmoplegia?

A

1) Vascular e.g. stroke
2) Demyelination e.g. multiple sclerosis (more commonly bilateral)

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25
Q

What would an abducens nerve palsy cause?

A

Failure to abduct ipsilateral eye

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26
Q

How does an oculomotor nerve palsy present?

A

Ipsilateral down and out eye (unopposed activation of SO and LR) with ptosis ± pupillary dilation

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27
Q

Which muscles have their motor supply by the oculomotor nerve?

A

Levator palpebrae superioris and extraocular muscles (except superior oblique and lateral rectus)

28
Q

What is the pupillary action of the oculomotor nerve?

A

Parasympathetic supply to the sphincter pupillae muscles to mediate pupil constriction

29
Q

What is different about a surgical third nerve palsy?

A

Pupil involvement (dilated) - bc the parasympathetic (constrictive) fibres run on the outside of the nerve so external compression will impair function of these fibres, causing pupil dilation

30
Q

What is different about a surgical third nerve palsy?

A

Pupil involvement (dilated) - bc the parasympathetic (constrictive) fibres run on the outside of the nerve so external compression will impair function of these fibres, causing pupil dilation

31
Q

What are other causes of a surgical third nerve palsy?

A

Cavernous sinus lesions - infection, thrombosis, tumour infiltration

32
Q

What would be the investigation for a surgical third nerve palsy and why?

A

MRI - looking for aneurysm

33
Q

What investigation should be done in all cases of cranial nerve neuropathies and why?

A

Fundoscopy - to exclude papilloedema

34
Q

What investigation would you do in cases of pupil-sparing (non surgical) oculomotor nerve palsy and why?

A

HbA1c - to look for diabetes (major cause)

35
Q

How does giant cell arteritis present?

A

Unilateral temporal headache and amaurosis fugax

36
Q

What investigation should be done in suspected GCA?

A

ESR

37
Q

What is Guillain-Barré syndrome (GBS)?

A

Ascending inflammatory demyelinating polyneuropathy

38
Q

What causes GBS?

A

1) Post-infection
2) Idiopathic (60%)

39
Q

How soon after infection does GBS present?

A

Typically 1-3 weeks

40
Q

Give 3 examples of infections that can lead to GBS?

A

Campylobacter, mycoplasma, EBV

41
Q

How does GBS present?

A

1) Progressive ascending symmetrical limb weakness/paralysis (affecting lower limbs first)
2) Paraesthesia may precede motor symptoms
3) LMN signs in lower limbs - hypotonia, flaccid paralysis, areflexia
4) Cranial nerve signs e.g. ophthalmoplegia, LMN facial nerve palsy (bilateral), bulbar palsy
5) Type 2 respiratory failure due to resp muscle weakness e.g. CO2 flap, bounding pulse
6) Autonomic dysfunction e.g, arrhythmia, labile BP

42
Q

What investigations are done in GBS?

A

1) Spirometry - to check for reduced FVC
2) Bloods - ABG (to check for type 2 resp failure) and anti-ganglioside antibodies
3) Lumbar puncture

43
Q

Which antibodies are present in GBS bloods?

A

Anti-ganglioside antibodies

44
Q

What does lumbar puncture show in GBS?

A

Albuminocytological dissociation
1) Raised protein
2) Normal cell counts + glucose

45
Q

What are conservative measures in GBS management?

A

1) Monitoring of ventilation - serial spirometry and ABG ± ventilation (intubation and admission to ICU) if FVC dangerous reduced
2) VTE prophylaxis - TEDs, LMWH
3) Protection of pressure areas

46
Q

What is medical management of GBS?

A

1) Intravenous immunoglobulin (IVIG)
2) If ineffective - plasmapheresis

47
Q

What is Miller Fisher syndrome?

A

A variant of GBS

48
Q

How does Miller Fisher syndrome present and which antibodies are positive?

A

Ataxia, ophthalmoplegia, areflexia - anti-GQ1b antibodies

49
Q

Which measure is used to monitor respiratory involvement in GBS?

A

Forced vital capacity (the volume of air exhaled following maximum inhalation)

50
Q

What is sensory peripheral neuropathy?

A

Damage to the peripheral sensory nerves responsible for causing symptoms of weakness, numbness and pain - large differential diagnosis

51
Q

What are the most common causes of sensory peripheral neuropathies?

A

ABCDE:
1) Alcohol toxicity
2) B12/folate deficiency
3) Chronic renal failure
4) Diabetes
5) Everything else - vasculitis and paraneoplastic

52
Q

How do sensory peripheral neuropathies present?

A

1) Gradually developing sensory disturbance and pain in a glove-and-stocking distribution with foot involvement preceding hand involvement - length dependent
2) If large fibres affected - paraesthesia and proprioceptive ataxia
3) If small unmyelinated fibres affected - burning, allodynia and hyperalgesia

53
Q

What are potential consequences of vitamin B12 deficiency?

A

1) Peripheral neuropathy
2) Subacute combined degeneration of the cord
3) Optic neuropathy
4) Dementia/encephalopathy

54
Q

What is diabetic amyotrophy?

A

1) Uncommon variant neuropathy seen in patients with poorly controlled diabetes
2) More common in older males with type 2
3) May be precipitated by sudden improvement in diabetic control
4) The response to medication is often poor, though most cases are self limiting (though often with some residual disability)

55
Q

How does diabetic amyotrophy present?

A

1) Prominent pain in the back, hips and proximal thigh muscles
2) May develop with progressive weakness and wasting

56
Q

How does diabetic polyneuropathy present?

A

1) Affects all sensory modalities with numbness and tingling
2) Followed by proprioceptive balance issues
3) Later followed by motor features

57
Q

What is the most common cause of foot drop?

A

Disease or trauma affecting the common peroneal nerve (often as it loops over the head of the fibula on the lateral aspect of the knee joint)

58
Q

Injury to which nerve most commonly causes foot drop?

A

Common peroneal nerve

59
Q

What is the key clinical feature of foot drop?

A

Weakness or paralysis of dorsiflexion and eversion (motor findings)

60
Q

What are other causes of foot drop?

A

1) L5 root lesion
2) Distal motor neuropathy
3) Small cortical lesions - other UMN features may be present
4) Uncommonly - intrinsic cord disease, partial sciatic nerve disease and myopathy may also mimic foot drop

61
Q

How would distal motor neuropathy present?

A

1) Foot drop
2) Loss of all movements of the foot
3) Glove and stocking sensory disturbance

62
Q

Lesion at which spinal root would cause foot drop?

A

L5

63
Q

How would an L5 root lesion (radiculopathy) present?

A

1) Foot drop + loss of inversion (as well as dorsiflexion and eversion) - bc inversion is a tibial nerve function and not lost in patients with a common peroneal nerve lesion
2) Sensory loss over L5 dermatome
3) Sciatica-type shooting leg pain may be present + acute onset back pain (compression of L5 nerve root on MRI)

64
Q

What is the most common cause of L5 radiculopathy?

A

Lumbosacral disc herniation

65
Q

How do you test for impairment of motor function in muscles served by the L5 nerve root?

A

Power of dorsiflexion of the big toe

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