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MD2 Neuro > Neuromuscular Disease > Flashcards

Neuromuscular Disease Flashcards

1
Q

Associated features of neuromuscular disease

A

MOTOR: muscle weakness/wasting (diploplia, dyspnoea, dysphagia), stiffness, cramps, fasciculation, clumsiness, poor balance, falls

SENSORY: numbness, burning, tingling

NON-SPECIFIC: fatigue

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2
Q

Give 3 examples of conditions causing diplopia and ptosis

A

Myasthenia gravis

Ocular nerve palsy

Thyroid eye disease (although more commonly proptosis, not ptosis)

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3
Q

Give 2 examples of conditions causing dysphagia and dysarthria

A

Myasthenia gravis

MND

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4
Q

Clinical features of MND

A

Muscle wasting including tongue

Fasciculations

Tone

Generalised weakness (no pattern)

Reflexes preserved until late or exaggerated

Plantars may be upgoing

No sensory loss (may have sensory symptoms but on testing no signs)

Cranial nerves (except bulbar) spared

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5
Q

How is MND diagnosed?

A

On the basis of symptoms and signs, consistent laboratory findings (EMG) and the exclusion of other diagnoses

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6
Q

What is MND?

A

Gradually progressive disorder with evidence of upper and lower motor neuron involvement and intact sensation

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7
Q

Prognosis of MND

A

Life expectancy bulbar onset: 6-12 months

Life expectancy limb onset: 2-5 years

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8
Q

What are neuromuscular disorders?

A

Conditions that affect:

a) peripheral nervous system (motor and/or sensory nerves, including anterior horn and dorsal root ganglion cell disorders)
b) neuromuscular junction
c) muscle

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9
Q

What are the important features on Hx in neuromuscular disease?

A

Time course: are symptoms acute or chronic?

FHx of similar complaints (e.g. hereditary neuropathies, muscular dystrophy)

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10
Q

What symptoms are typically seen in carpal tunnel syndrome?

A

Affecting median nerve supplied digits (thumb, index and middle fingers)

Worse at night; have to shake hand to stop symptoms

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11
Q

What is a unilateral foot drop indicative of?

A

L5 radiculopathy or peroneal neuropathy

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12
Q

What is the best diagnostic test for carpal tunnel syndrome?

A

Nerve conduction studies

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13
Q

What is the distribution of symptoms and signs in neuromuscular disease?

A

Generalised

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14
Q

Distinguish between anterior horn cell diseases, neuropathy, myaesthenia gravis and myopathy in terms of muscle wasting, fasciculations, weakness, reflexes and sensation

A
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15
Q

Ix for suspected NM problem

A

Electrophysiology: distinguishes neuropathy from myopathy, axonal from demyelinating, sensory vs motor, NMJ disorder

Laboratory: FBE, ESR, vit B12, CXR, BSL, HbA1c, UEC, TFT, LFT, PEP (protein electrophoresis), anti-NF, ANCA, ENA, HIV, CK, heavy metal screen, VDRL (for syphilis), genetic tests

LP

Muscle biopsy, muscle MRI

And for difficult cases, consider: nerve biopsy, MRI of nerve

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16
Q

55 year old previously well building surveyor, on no medications, 6/12 ago noticed cramps in both legs worse after exercise

Increasing leg weakness over past 3/12 months with L foot drop; had noticed twitching in the muscles of both legs but no sensory complaints

No FHx of weakness

What are the clinical features of MND?

A

Non-specific cramps after exercise

Fasciculations (usually presents with weakness not twitching; remember twitchig is common normally, esp in calves)

Subacute progressive problem

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17
Q

55 year old previously well building surveyor, on no medications, 6/12 ago noticed cramps in both legs worse after exercise

Increasing leg weakness over past 3/12 months with L foot drop; had noticed twitching in the muscles of both legs but no sensory complaints

O/E: cranial nerve examination normal, no tongue wasting or fasciculations, few scattered fasciculations in UL muscles (deltoid and periscapular), no muscle wasting or weakness, brisk reflexes, no sensory loss, thin leg muscles, fasciculations in thighs only after exercise, weakness of hi flexion 4/5 and ankle dorsiflexion 3/5, plantars downgoing, normal sensation

What is the significance of the brisk reflexes?

Ix?

A

Brisk reflexes are an UMN sign and suggests amyotrophic lateral sclerosis (commonly upper AND lower MND)

Ix: CK, NCS/EMG

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18
Q

55 year old previously well building surveyor, on no medications, 6/12 ago noticed cramps in both legs worse after exercise

Increasing leg weakness over past 3/12 months with L foot drop; had noticed twitching in the muscles of both legs but no sensory complaints

CK 859 (N is 50-200)

NCS/EMG: normal nerve conduction in motor and sensory nerves, but evidence of active and chronic denervation on needle EMG and fasciculations

Why is CK elevated in MND?

A

Due to the trophic effect of nerves on muscle; if this trophic effect is removed due to the death of the neuron, the CK will rise

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19
Q

What is the most common MND?

A

Amyotrophic lateral sclerosis (disorder of upper and lower motor neurons)

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20
Q

What clinical syndrome is amyotrophic lateral sclerosis associated with in some patients?

A

Fronto-temporal dementia (FTLD)

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21
Q

What is the peak age of onset for FTLD?

A

55-70 years

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22
Q

How does FTLD arise?

A

90% sporadic

10% familial (in some families linked to a mutation of the SOD1 gene on Ch 21; recently discovered link in some families to mutations in the gene responsible for the production of the protein TDP 43 and in others to C9orf72)

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23
Q

How is MND diagnosed?

A

Based on characteristic symptoms and signs: gradually progressive disorder with evidence of upper and lower motor neuron involvement and intact sensation

Consistent laboratory findings: EMG

But ultimately, Dx of EXCLUSION

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24
Q

What is the most common mimic for MND?

A

Widespread radiculopathies of the spine

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25
Q

What is the prognosis for MND?

A

Terminal illness in most cases

Course depends on presentation: average life expectancy bulbar onset is 6-12/12, average life expectancy with limb onset is 2-5 years

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26
Q

Common clinical manifestations of MND

A

Can affect all skeletal muscles causing weakness, dysphagia, anarthria, dyspnoea and respiratory failure

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27
Q

What is hereditary spastic paraplegia?

A

Inherited disorder caused by mutations in the spastin gene (although many other mutations exist)

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28
Q

What is adrenomyeloneuropathy?

A

X-linked disorder which results in the deposition of excess LCFAs in the CNS

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29
Q

What is primary lateral sclerosis?

A

Similar to ALS but with no LMN signs

Best prognosis but very difficult to diagnose (no EMG markers)

Clinical features include progressive UMN weakness

30
Q

35 year old previously well lawyer, on no medications, 6/12 ago began noticing episodic diplopia which was worse towards the end of the day, now increasing exertional dyspnoea over past 1/12 but no sensory complaints

No FHx of weakness

O/E: mild ptosis (L>R) with failure to adduct the L eye, speech becomes slurred during latter part of Hx taking, proximal weakness in shoulder girdle muscles not evident initially but appears with repetitive trials

List 2 post-synaptic and 2 pre-synaptic disorders of NMJs

A

Post-synaptic: myasthenia gravia (Abs against ACh receptors), MuSK myasthenia (Abs against MuSK)

Pre-synaptic: Lambert Eaton Myasthenic Syndrome (LEMS; Abs against Ca2+ channels), botulism

31
Q

What neoplasm is associated with LEMS? What is the mechanism?

A

Small cell lung Ca (it is a paraneoplastic syndrome)

32
Q

In what patient populations is botulism seen? How does it present?

A

IVDUs (abscess with botulinum spores)

Presents with acute neuromuscular weakness which usually starts at the top and works down; neurological emergency (must be recognised early)

33
Q

How long does it take for botulinum toxin to break down?

A

~6/12

34
Q

How is botulism treated?

A

Anti-botulinum toxin, THEN debride

Metronidazole

35
Q

List 6 clinical features that should make you suspect myasthenia gravis

A

Hx of fatigueability

Early involvement of EOMs and lid-opening muscles

Dysarthria

No muscle wasting

Weakness increasing with repetitive exercise

Reflexes and sensation unaffected

36
Q

Describe the pathophysiology of myasthenia gravis

A

AutoAbs which cross react with ACh receptors at NMJs

High association with thymic hyperplasia or thymoma

37
Q

Describe the pathophysiology of MuSK myasthenia?

A

Abs binding to MuSK cause the subunits of the ACh receptor to deaggregate and lose function

38
Q

Ix for Dx of myasthenia gravis and MuSK myasthenia, and expected findings

A

Tensilon test: short acting ACh-ase antagonist

Blood test for autoAbs to ACh receptor, MuSK (positive in 50% of cases of pure ocular myasthenia gravis, positive in 90% of cases of generalised myasthenia gravis, 70% of seronegative cases positive for anti-MuSK Abs)

CT chest: look for thymoma

EMG studies: repetitive stimulation, single fibre EMG, post-exercise facilitation (post-tetanic potentiation)

39
Q

What is the relationship between thymoma and myasthenia gravis?

A

Poorer; even if thymus is normal, removal improves prognosis if done when patient is young

40
Q

MuSK

A

Muscle-specific kinase

41
Q

How is the Tensilon test performed?

A

IV injection of short-acting drug (edrophonium) increases ACh concentration at the NMK and can temporarily reverse weakness due to myasthenia gravis

Good idea to be blinded: use a dummy saline syringe as well

42
Q

SEs of tensilon

A

Can become bradycardic

43
Q

Distinguish between electrophysiology study findings with repetitive stimulation in myasthenia gravis vs normal

A

Normal: no decrement in amplitude of muscle response with repetitive nerve stimulation

NMJ disorder: decrement

44
Q

Distinguish between electrophysiology study findings with post-exercise facilitation in LEMS and normal patients

A

Exercise consists of 10 secs maximal contraction of the target muscle and then electrophysiological readings are taken

Normal: no change in compound muscle action potentials (CMAP) post-exercise

LEMS: change in amplitude (wider) of CMAP post-exercise

45
Q

Mx of myasthenia gravis

A

ACh antagonists

Plasma exchange

IVIG

Immunosuppression with steroids, azathioprine

Thymectomy

46
Q

65 year old type 2 diabetic, on no medications, complains of poor balance and feelings in soles of feet like “walking on cotton wool”

O/E: poor balance on walking, wide-based gait, Romberg’s positive, weakness of dorsiflexion bilaterally, absent ankle reflexes, stocking loss of pain and temperature sensation with sensory level just below both knees

How are neuropathies categorised?

A

Inherited or acquired

Acute or chronic

Mononeuropathy, multifocal, generalised

Motor, sensory or mixed

47
Q

What is the most common type of neuropathy? How do they present?

A

Focal mononeuropathies

Symptoms are consistent with anatomy of neve involved

48
Q

What are the main categories of causes of focal mononeuropathies? Give examples of each

A

Compressive (most common): carpal tunnel syndrome, ulnar neuropathy

Infection: leprosy

Inflammatory: Bell’s palsy

Infiltrative: cancer, amyloid

Ischaemic: diabetes (3rd nerve palsy)

49
Q

Dx of focal mononeuropathies

A

NCS/EMG to localise lesion and confirm Dx

50
Q

Presentation of focal mononeuropathies

A

Focal symptoms and signs

51
Q

What is mononeuritis multiplex? Include definition, cause

A

Multifocal neuropathies (multiple mononeuropathies)

Multiple peripheral nerves affected rather than generalised (e.g. ulnar and tibial)

Cause almost always ischaemic (e.g. DM, vasculitis including Churg-Strauss syndrome) but occasionally infective (e.g. AIDS, CMV, sarcoid, leprosy)

52
Q

How are generalised peripheral neuropathies classified?

A

Acute or chronic

53
Q

What is the most common neurological defect in generalised peripheral neuropathy?

A

Sensorimotor: distal weakness and glove and stocking sensory loss (can be accompanied by severe pain, esp in diabetics, amyloid, etc)

54
Q

List 3 causes of acute demyelinating polyneuropathy

A

Guillain-Barre syndrome

AIDS seroconversion phase (can also cause GBS)

Lymphoma

55
Q

List 4 causes of acute axonal polyneuropathy

A

Glue sniffers neuropathy (due to N-hexane toxicity)

Vasculitis

Thiamine deficiency

Acute intermittent porphyria

56
Q

How does an acute polyneuropathy present?

A

Rapidly increasing diffuse weakness and/or sensory loss occurring over days

57
Q

What are the 7 categories of causes of chronic axonal polyneuropathy? Provide at least one example for each

A

Genetic: HMSN type II

Metabolic: DM, hypothyroidism

Toxin: EtOH, drugs, prescription Rx, heavy metals (arsenic/As, Pb)

Nutritional: thiamine, B12 deficiency, B6 excess

Paraneoplastic: Anti-Hu

Immune: abnormal paraprotein, Sjogren’s

Ischaemic: DM, vasculitis

58
Q

What are the 3 categories of causes of chronic demyelinating polyneuropathy? Provide at least one example for each

A

Genetic: HMSN type I, HNPP (Hereditary neuropathy with liability to Pressure Palsy)

Immune: inflammatory (e.g. CIDP - Chronic Inflammatory Demyelinating Polyneuropathy) or non-inflammatory (e.g. IgM anti-MAG neuropathy)

Paraneoplastic: POEMS syndrome

59
Q

POEMS syndrome

A

Polyneuropathy

Organomegaly

Endocrinopathy

Monoclonal gammopathy

Skin changes (e.g. hyperpigmentation)

60
Q

Classic changes on nerve conduction study in axonopathy, inherited demyelinating neuropathy and acquired demyelinating neuropathy

A

Axonopathy: low amplitude CMAPs, normal conduction velocity

Inherited demyelinating: slow conduction velocity, no block

Acquired demyelinating: slow conduction velocity, conduction block

61
Q

What disease process is shown in this histopathology specimen?

A

Small fibre neuropathy

62
Q

What disease process is shown in this histopathology specimen?

A

Axonal neuropathy

63
Q

What disease process is shown in this histopathology specimen?

A

Demyelinating disease (e.g. chronic inflammatory demyelinating polyneuropathy, CIDP)

64
Q

18 year old previously well young man, Hx of increasing weakness over last 6/12 which is most noticeable when getting out of chairs, walking up stairs and using the hair dryer

On no medications

No sensory complaints, does not fluctuate during the day

No FHx of weakness

O/E: waddling gait, can’t rise from squat without help, proximal weakness in shoulder girdle and hip girdle muscles

Dx? What are the different types?

A

Myopathy: inherited, metabolic, ion channel mutations or acquired

65
Q

List 6 inherited causes of myopathy

A

Myotonic dystrophy

Facio-scapulo-humeral dystrophy

Duchenne’s dystrophy

Becker’s dystrophy

Limb-girdle dystrophies

PROMM (proximal myotonic myopathy)

66
Q

List 2 metabolic causes of myopathy

A

Glycogen storage disease type V (McArdle)

Carnitine palmitoyltransferase II deficiency (CPT II deficiency)

67
Q

What ion channel mutations can cause myopathy?

A

Periodic paralyses: hypo K+, hyper K+, paramyotonia

68
Q

What are the 3 categories of causes of acquired myopathy? Give examples of each

A

Drugs: alcohol, statins

Endocrine/metabolic: hypothyroidism, hypokalaemia

Inflammatory: polymyositis, dermatomyositis, inclusion body myositis

69
Q

18 year old previously well young man, Hx of increasing weakness over last 6/12 which is most noticeable when getting out of chairs, walking up stairs and using the hair dryer

Ix?

A

Electrophysiology: needle EMG for myopathy and myotonia

CK: if elevated almost always indicates a myopathy (can be 500-1000 in MND)

FHx (genetic testing): e.g. myotonic dystrophy has a triplet repeat at Ch 9, DMD has loss of dystrophin gene on X chromosome

Muscle biopsy

70
Q

What findings on histopathology are characteristic of muscular dystrophies?

A

Varying muscle fibre size

Regenerating and degenerating fibres

Increased fibrosis

71
Q

What muscle membrane proteins can be visualised with special stains and for what myopathies is this technique used to aid Dx?

A

Dystrophin: Duchenne’s, Becker’s

Dysferlin: limb girdle dystrophies

Sarcoglycans: limb girdle dystrophies

72
Q

What features are seen on muscle biopsy in myositis?

A

Inflammatory cell infiltrate with T (polymyositis, inclusion body myositis) and B (dermatomyositis) lymphocytes

Degenerating and regenerating muscle cells

MD2 Neuro (9 decks)

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