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My MRCP > Muscle & Nerve Disease > Flashcards

Muscle & Nerve Disease Flashcards

1
Q

Think about the way muscle diseases can present in a patient
Symptoms [5]
Signs [3]

A
  • Weakness
  • SOB from resp muscles
  • Poor swallowing or aspiration
  • Cardiomyopathy
  • Cramp, pain, myoglobinuria
  • Wasting or hypertrophy
  • Reduced tone & reflexes
  • Motor Weakness
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2
Q

What is myoglobinuria? [2]

A

Myoglobin leaked from muscles that are breaking down due to certain muscle diseases. [1]
It’ll appear after exercise as black urine [1]

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3
Q

List the classifications of muscle disorders? [6]

A
  • Dystrophies
  • Chanellopathies
    (ion channel problems -> unrelaxable or weak muscles)
  • Metabolic muscle diseases
  • Inflammatory muscle diseases
  • Congenital Myopathies
  • Iatrogenic
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4
Q

Drug induced muscle disease

Causes
LSD CHAP

A
  • Lipid lowering agents, e.g. statins, fibrates, nicotinic acid, ezetimibe.
  • Steroids.
  • Drugs of abuse, e.g. alcohol, heroin, cocaine.
  • Colchicine, chloroquine.
  • Hydroxychloroquine.
  • Amiodarone.
  • Perhexiline.
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5
Q

Causes of raised CK [4]

A

General marker for muscle damage

■ Intense periods of exercise.
■ Rhabdomyolysis following prolonged immobilisation.
■ Denervation.
■ Drug ingestion (especially statins).
■ Muscle disease

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6
Q

What investigations are common for muscular diseases? [5]

A
  • Creatine Kinase
  • Lactate
  • Ammonia
  • Electromyography to distinguish between deneravation, NMJ disorders and primary muscle disease.
  • Biopsy is crucial with enzymic stains and IHC.
  • Genetic Tests (Most muscular dystrophies are genetic)
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7
Q

List some muscular dystrophies? [3]

A
  • Duchenne’s MD & Becker’s MD
  • Facioscapulohumeral
  • Limb Girdle MD (Proximal limb weakness)
  • Emery Dreifuss MD
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8
Q

Give one example of a channelopathy and describe it [3]

A

Familial Hypokalemic Periodic Paralysis [1] causes episodes of sudden muscle weakness [1] lasting seconds -> days [1]

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9
Q

Give an example of a metabolic muscle disease [1]

A

Endocrinopathies such as Thyroid or Cushing’s disease can affect the muscles.

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10
Q

Inflammatory muscle disease

Split causes into pathophysiology [4]

A
  • Idiopathic myositis - polymyositis, dermatomyositis
  • Autoimmune-associated myositis - SLE, RA, Mixed CTS, Sjogrens
  • Infection associated myositis- viral, bacterial, parasitic
  • Other diseases associated with myositis - vasculitis, sarcoidosis
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11
Q

What is myasthenia gravis? [2]
Describe its key feature [3]
What can this key feature manifest as? [4]

A

Autoimmune disorder [1] resulting in insufficient functioning acetylcholine receptors. [1]

The key feature is muscle fatigability[1] - muscles become progressively weaker during periods of activity [1] and slowly improve after periods of rest [1]
extraocular muscle weakness:
1. diplopia
2. proximal muscle weakness: face, neck, limb girdle
3. ptosis
4. dysphagia

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12
Q

What causes myasthenia gravis? [2]

What is it associated with? [3]

A

An auto-antibody blocks ACh receptors in the NMJ. [1]

Its fatigable because early in the day you produce lots of ACh so it can compete with the antibody [1] but by the end of the day its depleted and the antibody wins out so you get weaker until you rest again [1]

Associations

  1. thymomas in 15%
  2. autoimmune disorders: pernicious anaemia, autoimmune thyroid disorders, rheumatoid, SLE
  3. thymic hyperplasia in 50-70%
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13
Q

What investigations can you do for Myasthenia Gravis? [5]

A
  • AutoAntibody Tests
    70% +ve, 40% positive for anti-MUSK abs
  • CT chest to exclude a thymoma
  • Electromyography
  • Tensilon test
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14
Q

How does an EMG test for Myasthenia Gravis? [2]

Explain how the Tensilon test is done [1]

A

Repetitive stimulation should make the muscle fatigue, evident as a reduced amplitude on an EMG.

Tensilon test
- IV edrophonium reduces muscle weakness temporarily

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15
Q

MG Tx [3]

Management of myasthenia crisis [2]

A
  • Acetlycholinesterase Inhibitors eg pyridostigmine
  • Immunosuppression prevents antibody production (Prednisolone or Azathioprine), high dose steroids may cause initial deterioration
  • Thymectomy can prevent antibody production, early intervention against future thymoma?

Management of myasthenia crisis:

  • Plasmapheresis
  • IvIg
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16
Q

Define Peripheral Neuropathy?

A

Damage to nerves outside the CNS.
It can affect sensory axons, motor axons and ANS fibres

Can either be disease of a spinal root, single peripheral nerve or generalised peripheral neuropathy

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17
Q

What could cause a lesion to a single peripheral nerve?

A
  • Compression or entrapment

- Vasculitis to the vessels supplying the nerve

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18
Q

What could cause generalised peripheral neuropathy? [6]

A 
Metabolic: DM, alcohol
Toxic Drugs
Infections e.g. HIV
Inherited
Paraneoplastic (e.g. prostate)
Inflammatory demyelinating such as Guillain barre (acute) or Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)
B12 deficiency
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19
Q

Define Guillain Barre Syndrome [3]

Describe 3 key features

A

Immune mediated [1] demyelination of the peripheral nervous system [1] often triggered by an infection
(because the viral antigen is very similar to myelin) [1]

Causes rapid onset muscle weakness/wasting (ascending), areflexia and sensory changes
around 65% of patients experience back/leg pain in the initial stages of the illness

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20
Q

What tests can be done for peripheral neuropathies? [5]

A
  • Blood Tests (particularly for inflammatory conditions)
  • Genetic Analysis
  • Nerve Conduction Studies e.g. EMG
  • Lumbar Puncture for CSF analysis
  • Nerve Biopsy
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21
Q

What is the main type of anterior horn cell disorder? [1]

A

Motor Neuron Disease (Amyotrophic Lateral Sclerosis - ALS)

Its a progressive loss of motor neurons (Upper & Lower)

22
Q

How does ALS present? [6]

A 
Mixed upper and lower motor neuron signs:
# LMN - Fasciculations, Wasting, weakness
# UMN - Increased Tone, Hyperreflexia
# Theres no sensory involvement
# No ocular or sphincter involvement
  • Frontotemporal dementia
  • Stumbling spastic gait, foot drop
  • Weak grip, weak shoulder abduction
23
Q

Whats the prognosis for Motor Neuron Disease? [1]

A

3 yrs median survival post-diagnosis

24
Q

how do we diagnose ALS? [2]

A

Electromyography [1] showing denervation changes in >3 body regions [1]

25
Q

How would you treat ALS? [5]

A

Supportive treatment:

  • PEG Tube
  • Drooling: PROPANTHELINE or AMITRYPTILINE
  • Spasticity: baclofen
  • Respiratory failure: NIV
  • Physiotherapy, OT

Also Riluzole:
- Licensed for improving lifespan in ALS 3m
SE: LFTs increased, vomiting, tachycardia, somnolence, headache, vertigo

26
Q

What is Lambert-Eaton myasthenia syndrome?

What is its key feature [1]

A

Caused by antibody directed against presynaptic voltage gated calcium channel in the PNS

Associated with underlying malignancy SCLC 75%

Repeated muscle contractions lead to increased muscle strength

27
Q

Lambert Eaton Syndrome
What is this condition associated with? [1]
Describe 4 other symptoms

A

Has an association with small cell lung cancer

Other symptoms:
limb-girdle weakness (affects lower limbs first)
hyporeflexia
autonomic symptoms: dry mouth, impotence, difficulty micturating
ophthalmoplegia and ptosis not commonly a feature (unlike in myasthenia gravis)

28
Q

Describe the causative organisms that can trigger GBS [4]

A
  • Most common Campylobacter jejuni (GE infections)
  • Mycoplasma pneuonia
  • Haemophilus influenza
  • CMV, HIV
29
Q

What is Miller Fisher syndrome [3]

A

Associated with ophthalmoplegia, areflexia and ataxia

30
Q

Miller Fisher syndrome

  • Difference between GBS? [1]
  • What antibodies are found in 90% of cases? [1]
A

Usually presents as a descending paralysis rather than ascending as seen in other forms of Guillain-Barre syndrome

Anti-GQ1b antibodies

31
Q

GBS

Symptoms [5]

A
  • Progressive ascending muscle weakness up to 4w after trigger
  • Proximal muscles > distal so respiratory, CN VII affected
  • Deep tendon jerks are typically lost
  • Back and limb pain
  • Sensory disturbance
  • Autonomic dysfunction: sweating, tachycardia, BP changes
32
Q

GBS diagnostic criteria (and signs) [7]

Investigations [2]

A
  • Progressive weakness of all 4 limbs and areflexia is needed for dx
  • Progression over days
  • Near symmetry of symptoms
  • Sensory features are mild
  • CN involvement e.g. bilateral facial weakness
  • Recovery starts 2w after period of progression finished
  • Absence of fever at onset

Investigations

  • CSF protein increased, CSF WCC low
  • EMG showing slow conduction
33
Q

Chronic inflamamtroy demyelinating polyneuropathy

A

Antibody mediated inflammation results in segmental demyelination of peripheral nerves
* Similar to GBS but more insidious onset over weeks to months
* CSF has high protein content

34
Q

GBS Tx [3]

A

Tx: plasmapheresis, immunoglobulin, artificial ventilation

35
Q

Charcot marie tooth syndrome
AKA
Ax
Px [2]

A

HEREDITARY MOTOR AND SENSORY NEUROPATHY TYPE I
Ax:
- autosomal dominant (but some X-linked varieties)
Px:
- neuronal degeneration of genes that
- code the proteins involved in structure or function of nerve axons or myelin sheaths

36
Q

Charcot marie tooth syndrome

Presentation [4]

A
  • onset at puberty with peroneal atrophy
  • causing leg weakness, foot drop and variable loss of sensation
  • champagne bottle leg appearance (peroneal atrophy)
  • foot deformity (high arches and hammer toes)
37
Q

CMT syndrome
Ix [3]
Mx [4]
Prognosis

A

Ix: EMG, nerve biopsy, genetic testing excl. other causes of neuropathy
Mx: physio, OT, orthotics, analgesia
Pro: normal life expectancy

38
Q

Autonomic neuropathy

Classification [2]

A

Primary:
- Autoimmune autonomic ganglionopathy
- Parkinsonian syndromes
Secondary causes

39
Q

Secondary causes of autonomic neuropathy [8]

A
  • DM
  • amyloidosis
  • Guillain Barre
  • Sjogren’s, SLE
  • HIV, leprosy
  • Toxins
  • porphyria
  • paraneoplastic
40
Q

Autonomic neuropathy: Presentation [7]

A
  • Sympathetic failure:
    1. postural hypotension (fainting on standing/eating/hot bath)
    2. reduced sweating
  • Parasympathetic failure:
    1. constipation
    2. nocturnal diarrhea
    3. urinary retention
41
Q

Autonomic neuropathy: investigation [4]

A
  • Confirm postural hypotension with lying/standing BP
  • ECG shwoing variation of >10bpm with respiration is abnormal
  • Cystometry, bladder pressure studies
  • Pupil tests
42
Q

What is motor neuron disease?

A

Selective loss of motor neurons in the motor cortex, cranial nerve nuclei and anterior horn cells
BUT NO sensory loss or sphincter disturbance (ddx from polyneuropathy/MS)
NEVER affects eye movements

43
Q

Classification of MND

A
  • ALS
  • Progressive bulbar palsy: fastest progressing; only affects CN IX to XII
  • Progressive muscular atrophy
  • Primary lateral sclerosis
44
Q

Progressive muscular atrophy [3]

A
  • anterior horn cell lesion only
  • so NO UMN signs
  • affects DISTAL before proximal and better prognosis than ALS
45
Q

Primary lateral sclerosis [4]

A
  • loss of Betz cells in motor cortex
  • causes mainly UMN signs
  • with marked spastic leg weakness and pseudobulbar palsy
  • no cognitive decline
46
Q

Myotonic dystrophy

Inheritance pattern

A

Ax:

  • autosomal dominant Cl- channelopathy (DM1 = chromosome 9, DM2 = chromosome 3)
    • Genetics: anticipation (CTG repeats increase causing increasing severity with each generation)
47
Q

Myotonic dystrophy
Onset
Presentation [3]
Non-neurological symptoms [7]

A
  • onset at 25y/o w/ distal onset weakness (hand or foot drop)
  • weak sternomastoid and myotonia (tonic muscle spasm)
  • facial weakness and muscle wasting giving haggard appearance
  • bilateral late onset cataracts
  • male frontal baldness
  • DM
  • testis or ovary atrophy
  • cardiomyopathy, heart block, post-anaesthetic death
  • reduced cognition
48
Q

Myotonic dystrophy mx [6]

A
  • Genetic counselling
  • Mexiletine
  • Phenytoin
  • Acetazolamide
  • NIV for sleep apnoea
  • Cardiac pacing (heart block)
49
Q

Muscular dystrophies

Define
Hx and signs
Ix
Tx

A
  • Genetic abnormality affecting muscle protein components.
  • Hx/Exam: Gowers sign, progressive muscular wasting, waddling gait, calf muscle pseudohypertrophy, scoliosis, respiratory and cardio complications
  • Ix: muscle biopsy, increased CK, EMG, Genetics
  • Supportive treatment with no curative therapies.
50
Q

What is XP21 dystrophy

A

x-linked recessive conditions
mutation of dystrophin gene at locus Xp21
Muscle fiber necrosis, replaced with adipose and connective tissue

Duchenne muscular dystrophy
Becker muscular dystrophy- reduced severity of phenotype

51
Q

MuSK - what is the pathophysiology behind anti-MUSK antibiotics involved in Myasthenia Gravis?

A

Muscle specific kinase - tyrosine kinase receptor expressed selectively in skeletal muscles that helps to cluster post-synpatic proteins. Anti-MuSK abs may active complement inducing lysis of the post-synaptic membrane

52
Q

Guillian Barre syndrome

Pathophysiology [2]

A
  • Immune responses to ganglioside-like epitopes on the surface of triggering infectious agents cross- react with gangliosides displayed on nerve cells
  • resulting in macrophage-mediated attack of either the Schwann cell or the axolemma.

My MRCP (43 decks)

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