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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
What is McArdle's Syndrome?
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
26
Diseases/deficits associated with myopathy
Cushings (proximal) Thryrotoxicosis (severe proximal shoulder>pelvic) Hypothyroidism (muscle pain and stiffness) Calcium and vit D deficiency - proximal myopathy Acute and chronic hypokalaemia
27
Drugs which cause myopathies
``` Steroids (cushings) Lithium Fibrates AZT Vincristine Cholorquine Statins Alcohol ```
28
What is malignant hyperpyrexia?
Widespread skeletal muscle rigidity with hyperpyrexia Following general anaesthesia or other neuroleptic drugs Due to a defect in SR calcium-release channel
29
Young woman with opthalmoplegia + bilateral ptosis
MG
30
Young woman with opthalmoplegia + proptosis
Thyroid eye disease
31
Young woman with opthalmoplegia + brainstem symptoms
MS
32
EMG incremental increase after repetitive stimulation
LEMS - Lambert-Eaton Myasthenic Syndrome
33
EMG incremental decrease after repetitive stimulation
MG - Myasthenia Gravis
34
What is myasthenia gravis?
An acquired autoimmune disorder | Producing antibodies against post-synaptic acetylcholine receptor
35
How does MG present?
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
What abnormality is found in many MG patients?
Thymus dysfunction Hyperplasia found in 70% of patients
37
Two groups of MG patients?
Young women, 20-35years - acute, severely fluctuating - more generalised, HLA-68 and HLA-DR3 association Older men 60-75 years - more ocularbulbar presentation
38
Ocular symptoms in MG
Ptosis and diplopia
39
Other important weakness symptoms
Neck and trunk axial weakness | Respiratory muscle weakness
40
Other head problems
Weak jaw and face Dysarthria Dysphonia Dysphagia Cranial muscles affected
41
Diagnosis test in MG
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
Investigations in MG x5
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
Prognosis of MG
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
Medical management of MG x4
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
Surgical treatment of MG
Thymectomy - in patients with thymic hyperplasia this improves prognosis In thymoma - remove a possibly malignant tumour - will not improve MG
46
Intervention treatment of MG
Plasmapheresis - acute exacerbation or resp. involvement Only lasts a few days therefore needs repeating
47
What is Lambert-Eaton Myasthenic Syndrome?
Rare Antibodies to presynaptic voltage-gated calcium channels at NMJ Therefore failure of Ach release
48
What is the cause of LEMS in many cases?
Non-metastatic manifestation of malignancy especially small cell carcinoma of lung
49
Presentation of LEMS
Proximal limb weakness, especially lower limbs Ocular and Cranial muscles typically spared Initial improvement in power following exercise Reflexes absent Sometimes autonomic involvement
50
Treatment of LEMS
Try and treat primary tumour Guanethidine hydrocholride and 4AP - may enhance Ach release Steroids and plasmapheresis may help
51
3 rarer types of Myasthenia
Congenital MG - weakness as newborns - often problems with Ach release Neonatal MG - antibodies across placenta - resolves after delivery Penicillamine-induced myasthenia
52
What toxin can damage NMJ?
Botulinum toxin from clostridium botulinum Condition similar to v.severe MG
53
What is MND
A neurodegenerative condition causing progressive weakness and eventually death - within 1-5years Death usually from respiratory failure or aspiration
54
Annual incidence of MND | Overall incidence
2/100,000 | 6/100,000
55
Usual age of presentation of MND
50-75 years
56
Which presentation has shorter life expectancy?
Bulbar involvement - aspiration pneumonia more common
57
Pathogenesis of MND
Neurodegeneration of UMN, LMN and cranial nerve motor nuclei and nerves
58
Prevalence of frontal symptoms in MND
5% have frontotemporal dementia | 40% have some measurable frontal lobe impairment
59
Pathology of MND - cellularly
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
Causes of MND
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
4 clinical patterns seen in MND
1) Amyotrophic Lateral Sclerosis 2) Progressive Muscular Atrophy 3) Progressive Bulbar or pseudobulbar palsy 4) Primary Lateral Sclerosis
62
Features of ALS
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
Features of Progressive Muscular Atrophy
Purely LMN Therefore weakness, wasting, fasciculations Usually starts in one limb and spreads to involve adjacent spinal segments
64
Features of progressive bulbar or pseudobulbar palsy (corticobulbar palsy)
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
Features of primary lateral sclerosis
``` Rare 1-2% Only UMN affected Loss of Betz cells in cortex Legs usually affected first Progressive tetraparesis and PBP Cognition not affected ```
66
Features not present in MND which distinguish it from MS
No sensory loss | No sphincter dysfunction
67
Features not present in MND which distinguish it from MG
No opthalmoplegia
68
DX of MND
No diagnostic test | Tests to exclude other pathology - eg. MRI
69
DDX of ALS
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
DDX of Progressive muscular atrophy
Only LMN Poliomyelitis Post-polio syndrome Neuropathy
71
DDX of PBP
Cerebrovascular disease can cause PSP as well as UMN limb signs MS - usually pseudobulbar palsy but also eye and other brainstem syndromes
72
DDX of BP
MG | Tumours causing lower cranial nerve lesions
73
Medical treatment of MND
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
Management of MND
Blended food, NG tube, percutaneous catheter gastrostomy Analgesia for pain Non-invasive ventilation for respiratory failure - shown to improve survival by about 7months
75
Do you get cerebellar symptoms in MS
yes
76
When do you use gadolinium enhancement with neuromuscular stuff
Shows active lesion in MRI for MS
77
DNA cause of myotonic dystrophy
trinucelotide CTG triplet repeat in UTR of DMPK genen

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