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Neurology > Muscle Disorder > Flashcards

Muscle Disorder Flashcards

1
Q

What are general clinical features of myopathies?

A

Usually proximal weakness
Loss of tone secondary to disease of muscle
Loss of muscle bulk from proximal wasting
Preserved reflexes

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2
Q

When do you get enlarged muscles?

A

Pseudohypertrophy from muscle infiltration of fat in muscular dystrophies - exacerbates the weakness

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3
Q

What do you see on EMG with myotonia?

A

Sustained contraction/slow relaxation - for a few seconds often during attempted relaxation

Rhythmic discharges, high frequency, elicited by a sharp tap on muscle belly

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4
Q

When do you get pain in muscle disease

A

Rare presentation

Can get it in severe inflammatory myopathy

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5
Q

What is elevated in many dystophies

A

CK - marker of muscle fibre damage

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6
Q

What do you see on EMG with myopathies?

A

Short-duration spiky polyphasic muscle action potentials

Occasionally spontaneous fibrillation

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7
Q

What are polymyositis and dermatomyositis?

A

Chronic inflammation of muscles

Inflammation of muscles and of the skin

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8
Q

Causes of polymyositis?

A

Unknown - may involve viruses and autoimmune factors (autoantibodies found in 25% of patients)

25% associated with connective tissue disease
10% underlying carcinoma - especially in dermatomyositis

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9
Q

Clinical features of polymyositis

A

Usually presents in 40-50 s
Proximal muscle weakness!!
Pain and tenderness in less than half of patients

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10
Q

Clinical features of dermatomyositis

A

Muscle weakness, pain etc

Macular erythema on face
Gottron’s papules - over dorsal aspects of fingers
Nail-fold haemorrhages
Photosensitivity

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11
Q

What will muscle biopsy show in polymyositis

A

Muscle fibre necrosis with inflammatory infiltrate

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12
Q

Treatment of polymyositis

A

Corticosteroids and other immunosuppressive drugs

Treat carcinoma and associated connective tissue disease

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13
Q

Prevalence of Duchennes Muscular Dystrophy

A

1/3000 male infants - x-linked recessive condition

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14
Q

Pathology of duchennes muscular dystrophy

A

Absence of dystrophin -skeletal muscle protein

Affects skeletal and cardiac muscle

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15
Q

Presentation of DMD

A

No abnormality at birth - obvious by age 4, wheelchair bound by 10 years old

Initially proximal weakness with calf pseudohypertrophy

Normally death by age 20 from respiratory failure or cardiomyopathy

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16
Q

Sign present in DMD

A

Gower’s sign - child needs to use hands to stand up

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17
Q

Investigations for DMD

A

Often done clinically
CK grossly elevated
EMG = myopathic
Muscle biopsy shows fatty infiltration and lack of staining for dystrophin

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18
Q

Management of DMD

A

No cure
Physiotherapy to prevent contractures
Respiratory support - portable

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19
Q

Features of Becker’s Muscular dystrophy

A

X-linked recessive

Similar to DMD but much milder and dystrophin is depleted rather than absent

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20
Q

Presentation of Beckers MD

A

Weakness only becomes apparent in young adults - cramps with exercise

Cardiomyopathy problems are worse than skeletal muscle problems and predispose to arrhythmias

Cardiac problems lead to death

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21
Q

Features of facioscapulohumeral dystrophy

A 
Autosominal dominant 
Onset age 10-40 
Affects face, shoulder and pelvic girdle 
Winged scapular and foot drop 
Muscle hypertrophy is rare 
20% require wheelchair
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22
Q

What do myotonic dystrophies present with?

A

Tonic muscle spasm/delayed relaxation (myotonia)

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23
Q

Features of Myotonic dystrophy

A

Dystrophia Myotonica

Onset in 20s

Progressive distal-onset muscle weakness
Weakness and thinning of facial muscles and sternocleidomastoid muscles

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24
Q

Associated features of myotonic dystrophy

A 
Male frontal baldness
Gynaecomastia and testicular atrophy 
Cataracts
Cardiomyopathy and conduction defects 
Mild intellectual impairment and sleep disturbance 
DM 
Bronchiectasis
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25
Q

What is McArdle’s Syndrome?

A

Deficiency of myophosphorylase in skeletal muscle

Symptoms begin in teens

Fatigue and severe pain during exercise

Continued exercise causes contractures

DX - absence of rise in venous lactate during forearm exercise test

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26
Q

Diseases/deficits associated with myopathy

A

Cushings (proximal)
Thryrotoxicosis (severe proximal shoulder>pelvic)
Hypothyroidism (muscle pain and stiffness)

Calcium and vit D deficiency - proximal myopathy

Acute and chronic hypokalaemia

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27
Q

Drugs which cause myopathies

A 
Steroids (cushings)
Lithium 
Fibrates
AZT 
Vincristine 
Cholorquine
Statins 
Alcohol
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28
Q

What is malignant hyperpyrexia?

A

Widespread skeletal muscle rigidity with hyperpyrexia

Following general anaesthesia or other neuroleptic drugs

Due to a defect in SR calcium-release channel

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29
Q

Young woman with opthalmoplegia + bilateral ptosis

A

MG

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30
Q

Young woman with opthalmoplegia + proptosis

A

Thyroid eye disease

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31
Q

Young woman with opthalmoplegia + brainstem symptoms

A

MS

32
Q

EMG incremental increase after repetitive stimulation

A

LEMS - Lambert-Eaton Myasthenic Syndrome

33
Q

EMG incremental decrease after repetitive stimulation

A

MG - Myasthenia Gravis

34
Q

What is myasthenia gravis?

A

An acquired autoimmune disorder

Producing antibodies against post-synaptic acetylcholine receptor

35
Q

How does MG present?

A

Proximal weakness and fatiguability of skeletal muscles (therefore worst after use and at the end of the day)

Most frequently affects proximal limbs, ocular and bulbar muscles

Muscle wasting rare and sensory exam is normal

36
Q

What abnormality is found in many MG patients?

A

Thymus dysfunction

Hyperplasia found in 70% of patients

37
Q

Two groups of MG patients?

A

Young women, 20-35years - acute, severely fluctuating - more generalised, HLA-68 and HLA-DR3 association

Older men 60-75 years - more ocularbulbar presentation

38
Q

Ocular symptoms in MG

A

Ptosis and diplopia

39
Q

Other important weakness symptoms

A

Neck and trunk axial weakness

Respiratory muscle weakness

40
Q

Other head problems

A

Weak jaw and face
Dysarthria
Dysphonia
Dysphagia

Cranial muscles affected

41
Q

Diagnosis test in MG

A

Tensilon/Edrophonium Test
Fast-acting anti-cholinesterase
IV bolus with atropine (prevent cardiac side effects)
Weakness improves within seconds and only lasts for 2-3minutes

Now only used after other clinical tests if confirmation still needed

42
Q

Investigations in MG x5

A

1) Acetylcholine receptor antibodies - 85% of patients
2) EMG - incremental decrease after repetitive stimulation
3) Muscle autoantibodies
4) Thymus imaging - CT or MRI
5) Spirometry to check VC due to ventilation failure

43
Q

Prognosis of MG

A

Can have fluctuating course
Can get acute respiratory exacerbations following infection or drugs - ventilation needed

Can remit permanently after thymus removal or with immunosuppressive treatment

44
Q

Medical management of MG x4

A

Oral acetylcholinesterases - pyridostigmine - lasts about 3-5 hours - only symptomatic

Immunosuppression - corticosteroids (prednisolone) - excellent response in 70% of patients

IV - immunoglobulin - in acute exacerbation or if resp involvement

Azathioprine - steroid sparing agent

45
Q

Surgical treatment of MG

A

Thymectomy - in patients with thymic hyperplasia this improves prognosis

In thymoma - remove a possibly malignant tumour - will not improve MG

46
Q

Intervention treatment of MG

A

Plasmapheresis - acute exacerbation or resp. involvement

Only lasts a few days therefore needs repeating

47
Q

What is Lambert-Eaton Myasthenic Syndrome?

A

Rare
Antibodies to presynaptic voltage-gated calcium channels at NMJ
Therefore failure of Ach release

48
Q

What is the cause of LEMS in many cases?

A

Non-metastatic manifestation of malignancy especially small cell carcinoma of lung

49
Q

Presentation of LEMS

A

Proximal limb weakness, especially lower limbs

Ocular and Cranial muscles typically spared

Initial improvement in power following exercise

Reflexes absent

Sometimes autonomic involvement

50
Q

Treatment of LEMS

A

Try and treat primary tumour

Guanethidine hydrocholride and 4AP - may enhance Ach release

Steroids and plasmapheresis may help

51
Q

3 rarer types of Myasthenia

A

Congenital MG - weakness as newborns - often problems with Ach release

Neonatal MG - antibodies across placenta - resolves after delivery

Penicillamine-induced myasthenia

52
Q

What toxin can damage NMJ?

A

Botulinum toxin from clostridium botulinum

Condition similar to v.severe MG

53
Q

What is MND

A

A neurodegenerative condition causing progressive weakness and eventually death - within 1-5years

Death usually from respiratory failure or aspiration

54
Q

Annual incidence of MND

Overall incidence

A

2/100,000

6/100,000

55
Q

Usual age of presentation of MND

A

50-75 years

56
Q

Which presentation has shorter life expectancy?

A

Bulbar involvement - aspiration pneumonia more common

57
Q

Pathogenesis of MND

A

Neurodegeneration of UMN, LMN and cranial nerve motor nuclei and nerves

58
Q

Prevalence of frontal symptoms in MND

A

5% have frontotemporal dementia

40% have some measurable frontal lobe impairment

59
Q

Pathology of MND - cellularly

A

Protein aggregation may be involved
RNA processing proteins in cytoplasmic inclusions - TDP-43 and FUS

Oxidative neuronal damage and glutamate mediated excitotoxicity have been implicated

60
Q

Causes of MND

A

5-10% are familial (mutations in SOD-1, TDP-43 and FUS)

Usually sporadic

Guam incidence is higher may be due to environment (Cycad nut) or familial

61
Q

4 clinical patterns seen in MND

A

1) Amyotrophic Lateral Sclerosis
2) Progressive Muscular Atrophy
3) Progressive Bulbar or pseudobulbar palsy
4) Primary Lateral Sclerosis

62
Q

Features of ALS

A

UMN and LMN involvement
Therefore weakness, UMN signs (hyperreflexia, spasticity) and LMN signs (fasciculations, wasting)

One limb and then gradually to other

LMN signs usually develop after the presentation of asymmetric spastic paraparesis

63
Q

Features of Progressive Muscular Atrophy

A

Purely LMN
Therefore weakness, wasting, fasciculations
Usually starts in one limb and spreads to involve adjacent spinal segments

64
Q

Features of progressive bulbar or pseudobulbar palsy (corticobulbar palsy)

A

20%
Initially just CN involvement until MND merges

talking and swallowing affected

Bulbar = LMN - wasting and tongue fasciculation, absent jaw jerk and gag reflex, quiet/hoarse/nasal voice

Pseudobulbar = UMN - slow tongue movements, slow deliberate speech, increased reflexes, pseudobulbar affect (mood incongruent weeping or giggling)

65
Q

Features of primary lateral sclerosis

A 
Rare 1-2% 
Only UMN affected
Loss of Betz cells in cortex 
Legs usually affected first
Progressive tetraparesis and PBP 
Cognition not affected
66
Q

Features not present in MND which distinguish it from MS

A

No sensory loss

No sphincter dysfunction

67
Q

Features not present in MND which distinguish it from MG

A

No opthalmoplegia

68
Q

DX of MND

A

No diagnostic test

Tests to exclude other pathology - eg. MRI

69
Q

DDX of ALS

A

Cervical spondylosis - as combination of UMN from radiculopathy and anterior horn cell loss - LMN

Spinal tumours, LMN at level of pathology and UMN below lesion

Hyperthyroidism - wasted fasciculating muscles but secondary to myopathy with brisk reflexes

70
Q

DDX of Progressive muscular atrophy

A

Only LMN
Poliomyelitis
Post-polio syndrome
Neuropathy

71
Q

DDX of PBP

A

Cerebrovascular disease can cause PSP as well as UMN limb signs

MS - usually pseudobulbar palsy but also eye and other brainstem syndromes

72
Q

DDX of BP

A

MG

Tumours causing lower cranial nerve lesions

73
Q

Medical treatment of MND

A

No curing treatment

Riluzole (antiglutamergic) prolongs life by 3 months - side effects = raised LFT (mainly in ALS)

Drooling - propantheline and amitriptyline

Baclofen or Tizanidine - for spasticity

74
Q

Management of MND

A

Blended food, NG tube, percutaneous catheter gastrostomy

Analgesia for pain

Non-invasive ventilation for respiratory failure - shown to improve survival by about 7months

75
Q

Do you get cerebellar symptoms in MS

A

yes

76
Q

When do you use gadolinium enhancement with neuromuscular stuff

A

Shows active lesion in MRI for MS

77
Q

DNA cause of myotonic dystrophy

A

trinucelotide CTG triplet repeat in UTR of DMPK genen

Neurology (10 decks)

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