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Neurology for RACP > Myopathy, myasthenia and neuropathy > Flashcards

Myopathy, myasthenia and neuropathy Flashcards

1
Q

10 patterns of myopathies

A
  1. Proximal “Limb‐Girdle” Weakness
  2. Distal Weakness
  3. Proximal Arm/Distal Leg (Scapuloperoneal) Weakness
  4. Distal Arm/Proximal Leg Weakness
  5. Ptosis with or without Ophthalmoplegia
  6. Prominent Neck Extensor Weakness
  7. Bulbar Weakness
  8. Episodic Weakness/Pain/Rhabdo
  9. Episodic Weakness Unrelated to Exercise
  10. Stiffness/Inability to Relax
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2
Q

Sites of myopathic pathology

A

Muscle Channel

  • Muscle Structure
  • Membrane proteins
  • Sarcomere proteins
  • Nuclear proteins
  • Muscle Metabolism
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3
Q

6 questions to address myopathy

A
  1. Patient’s symptoms and signs?
  2. Temporal evolution?
  3. Family history of a myopathic disorder?
  4. Precipitating factors that trigger episodic weakness or myotonia?
  5. Associated systemic signs or symptoms?
  6. Distribution of weakness?
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4
Q

Types of hereditary myopathies

A
  • Muscular dystrophies
  • Congenital myopathies
  • Myotonias
  • Channelopathies
  • Metabolic myopathies
  • Mitochondrial myopathies
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5
Q

Types of acquired myopathies

A
  • Inflammatory/Immune myopathies
  • Myopathies associated with systemic illness
  • Endocrine myopathies
  • Drug‐induced/toxic myopathies
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6
Q

Distal myopathies

A

• Late adult onset:

  • Welander
  • Markesbery/Udd

• Early adult onset:

  • Nonaka
  • Miyoshi (dysferlinopathy)
  • Laing
  • Desmin (myofibrillar) myopathy
  • Centronuclear myopathy
  • Myotonic dystrophy
  • Debrancher deficiency
  • Miyoshi (dysferlinopathy)
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7
Q

Stiffness/inability to relax

A

Improves with exercise:

-Myotonia – Na++ or Cl‐ channelopathies

Worsens with exercise:

  • Paramyotonia congenita – Na++ channelopathy

With fixed weakness:

  • Myotonic dystrophy (DM1)
  • Proximal myotonic myopathy (DM2)
  • Becker’s disease (AR Cl‐ channelopathy)
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8
Q

Myopathy genetics - X linked diseases

A

X‐linked - Duchenne MD, Becker MD, Emery‐Dreifuss

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9
Q

Myopathy genetics - Autosomal dominant disease

A

Autosomal dominant - FSH, LGMD, OPMD, Myotonic dystrophy, PP, PC, Thomsen’s disease, Central core myopathy

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10
Q

Myopathy genetics - Autosomal recessive disease and maternal transmissioon

A

Autosomal recessive: LGMD, Metabolic myopathies, Becker’s myotonia

Maternal transmission: Mitochondrial myopathies

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11
Q

Clinical features of myotonic dystrophy

A

CTG triplet repeat genetic mutation with anticipation with each generation

Myotonia

Weakness distal > proximal

Sternomastoid and temporalis wasting

Frontal balding

Diabetes/insulin resistance, hypogonadal, hypopituitary

Cataracts

Intellectual impairment, avoidant personality

Cardiac conduction defects-arrhythmias-yearly ECG

Cardiomyopathy- late

Respiratory and Swallowing difficulties

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12
Q

Differentials for recurrent weakness

A

Myasthenia, periodic paralysis, CIDP, (porphyria)

Metabolic defects

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13
Q

Differentials for recurrent myalgia

A

Connective tissue/rheumatoid disease, CIDP, myositis, metabolic defects

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14
Q

Differentials for recurrent rhabdomyolysis

A

Toxic, viral myositis, dystrophy, metabolic defects

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15
Q

Types of metabolic myopathies

A

Lipid storage disorder - develops with prolonged sustained exercise and fasting; most common familial form - Carnitine Palmitoyl Transferase; biopsy may be normal or have lipid accumulation

Glycogen storage disorder- occurs with brief intense exercise- McArdle’s myophosphorylase deficiency

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16
Q

Genetics of spinomuscular atrophy

A

Autosomal recessive gene due to loss of SMN1 on chromosome 5q

Variable penetrance with more severe disease due to loss of “back up” SMN2 genes

4 clinical phenotypes

SMA 1 (2 or 3 copies SMN2) -Severe, neonatal, respiratory failure, death in infancy

SMA 2 (3 copies) - never stand, death after 2yo

SMA 3 (4-8) - stand, death in adulthood

SMA 4 (less marked mutation) - can be adult onset, can ambulate lifelong, normal life expectancy

17
Q

Genetic therapies for DMD and SMA

A

Nusinersen, mRNA antisense for interon 7(SMA)

AVXS101 - viral vector replacement of SMA gene

Eteplirsen - mRNA antisense for exon 51, prevent splicing

18
Q

Clinical features of inflammatory myopathies

A
  • F>M
  • Weakness: proximal
  • Onset: subacute
  • Muscle enzymes: elevated
  • EMG: irritable myopathy
  • MRI: evidence of inflammation
  • Muscle biopsy: inflammation, necrosis, etc…
  • Responsive to immunosuppressive therapy
19
Q

4 Types of immune mediated myopathies

A

Polymyositis (PM)

Dermatomyositis (DM)

Immune-mediated necrotizing myopathy (IMNM)

Inclusion body myositis (IBM):

20
Q

Anti-HMG-CoAR induced myopathies

A

Biopsy: necrotizing in 80%

Nearly 100% proximally weak

75% with myalgias

Maximum CK ~10,000

Requires immunosuppressive therapy to treat

Myopathy associated with statin exposure (~70%)

Progresses despite discontinuing statins

21
Q

Diagnosis of inclusion body myositis

A

Degenerative disease of muscle due to cytoplasmic aggregates TDP43

Inclusions 20% of histology; mostly perifascicular inflammation

Anti-NTC51 abs highly specific, titre predicts severity also

Poor response to steroid therapy

22
Q

Cancers commonly associated with dermatomyositis

A

Ovarian

Lung

Pancreas

NHL

Stomach

23
Q

Diagnosis of cancer in DM

A

anti-p155 antibody has high specific and good NPV for cancer detection in DM

24
Q

Treatment for myasthenia gravis

A

IVIg for exacerbation

Pyridostimine (Not effective in MuSK positive patients)

Corticosteroids

Plasmapheresis for crisis

Thymectomy

Other immunosuppressives (marginally effective)

25
Q

Differentials for myasthenia gravis

A

CNIII, CNIV and/or CNVI palsies - PCOM aneurysm, diabetes, cavernus sinusitis/thrombosis, lymphatomous meningitis, sarcoid etc.

Miller fischer variant of Guillain Barre syndrome

Thyroid ophthmalopathy

Myotonic dystrophy and occulopharyngeal muscular dystrophy

Chronic progressive external ophthalmoplegia (CPEO) or Kearns Sayre syndrome

26
Q

Diagnosis of myasthenia gravis

A

Presentation of variable ptosis and ophthalmoplegia, facial, jaw and neck weakness and proximal limb weakness (including respiratory muscles) with demonstrated fatiguability

EMG - decrement in amplitude in repetitive muscle stimulation

  • Ice pack test and Tensilon testing

ACh-R- antibodies- specific, not sensitive, titre does not reflect severity

Anti-MuSK antibodies- present in absence of ACh-R antibodies, specific to non-occular, generalised MG

27
Q

10 Types of neuropathy presentation

A

Symmetric proximal and distal weakness with sensory loss

Asymmetric proximal and distal weakness with sensory loss

Asymmetric distal weakness with sensory loss

Asymmetric distal weakness without sensory loss

Symmetric distal weakness without sensory loss

Focal proximal weakness without sensory loss

Symmetric sensory loss with distal LMN weakness and UMN weakness

Symmetric distal sensory loss without weakness

Asymmetric proprioceptive sensory loss without weakness

Additional autonomic symptoms and signs

28
Q

Differentials for distal and proximal motor weakness with sensory loss

A

CIDP or GBS

Lead poisoning, botulism, acute intermittent porphyria

Possible paraproteinaemic neuropathy (MM, Waldenstrom’s, POEMs, lymphoma, amyloid)

NCS - motor slowing, conduction block with dispersion, increased F wave latencies, reduced sensory nerve action potentials (SNAP)

29
Q

Symmetric distal motor and sensory or sensory only neuropathy differentials

A

Diabetes Mellitus

Alcohol

Drugs

Toxins

Amyloidosis

Metabolic disorders (Fabry’s, etc.)

CMT

Cryptogenic sensory neuropathy

HSAN (hereditary)

30
Q

Asymmetric distal weakness with sensory loss mononeuropathy differential (single nerve)

A

Compression/entrapment mononeuropathies and radiculopathies

31
Q

Asymmetric distal weakness with sensory loss multifocal mononeuropathy

A

Vasculitis

Cryoglobulinaemia

Amyloidosis

Sarcoidosis

Infectious (Hep B, C, HIV,CMV, lyme disease, leprosy)

Hereditary neuropathy with pressure palsies (HNPP)

Tumour infiltration

32
Q

Distal symmetric motor and sensory neuropathy with UMN signs

A

Sub-acute degeneration of the spinal cord (B12, copper deficiency/zinc excess, vitamin E deficiency)

Inherited disorders - Freiderich’s ataxia, adrenmyeloneuropathy, MLD

33
Q

Asymmetric distal proprioceptive loss (ganglionopathy/neuronopathy)

A

B6 Toxicity

Sjogrens

Paraneoplastic?/cancer

HIV sensory neuronopathy

Cisplatin based chemotherapeutics

34
Q

Asymmetric distal motor only pattern

A

Progressive muscular atrophy

Multifocal motor neuropathy

Multifocal acquired motor axonopathy (MAMA)

Juvenille monomelic amyotrophy

35
Q

Distal and proximal motor only pattern

A

Spinal musclar atrophy

36
Q

Neuropathies with associated autonomic disturbance

A

Diabetes Mellitus

Amyloidosis

Guillain Barre syndrome

Vincristine induced

Porphyria

HIV associated autonomic neuronopathy

Hereditary sensory autonomic neuropathy

Idiopathic pan dysautonomia

37
Q
A

Neurology for RACP (4 decks)

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