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BR 3rd Ed > Ch 5 - EDX: Myopathies > Flashcards

Ch 5 - EDX: Myopathies Flashcards

1
Q

What is dystrophin?

A

Protein found in the sacrolemma of normal muscle that provides mechanical support and structural integrity for the muscle membrane cytoskeleton

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2
Q

What does mutation of dystrophin lead to?

A

Muscle fiber necrosis. Patients present with clinical symptoms of myalgias, fatigue, and weakness.

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3
Q

What is myotonia?

A

Painless delayed relaxation of skeletal muscles following a voluntary contraction

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4
Q

What can exacerbate myotnia?

A

Cold
Dilantin
Procainamide
Calcium channel blockers

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5
Q

What is Arthrogryposis?

A

Fixed deformity of the extremities due to intrauterine hypomobility, myopathy, muscular dystophy or oligohydraminos

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6
Q

What is seen on NCS in myopathy?

A

SNAP: Normal
CMAP: Dec amp with significant muscle fiber atrophy. Normal latencies and conduction velocities

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7
Q

What is seen on EMG in myopathy?

A

Low amp
Short duration
Polyphasic MUAP with early recruitment
Resting activity depends on d/o

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8
Q

What is Quantitative EMG used for?

A

Detailed measurement of MUAPs and waveform duration using 20 MUAPs on screen set with a trigger and delay line

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9
Q

Which myopathies have fibs and positive sharp waves on EMG?

A
  • Polymyositis
  • Dermatomyositis
  • Inclusion body myopathy
  • Trichinosis
  • Toxic myopathies
  • Direct muscle trauma
  • Rhabdomyolysis
  • Acid maltase deficiency
  • Myotubular myopathy
  • Hyperkalemic periodic paralysis
  • Nemaline rod
  • Sarcoid myopathy
  • Muscular dystrophies
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10
Q

Which myopathies have complex repetitive discharges (CRD’s) on EMG?

A
  • Polymyositis
  • Dermatomyositis
  • Muscular dystrophies
  • Schwartz-Jampel syndrome • Inclusion body myopathy
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11
Q

Which myopathies have myotonic discharges on EMG?

A
  • Myotonic congenita
  • Myotonic dystrophy
  • Paramyotonia congenita
  • Hyperkalemic periodic paralysis
  • Acid maltase deficiency
  • Hypothyroid myopathy
  • Myotubular myopathy
  • Chloroquine myopathy
  • Diazocholesterol intoxication
  • Polymyositis
  • Dermatomyositis
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12
Q

What causes short duration small amplitude (SDSA) MUAPs on EMG?

A

Classic polyphasic potentials are due to loss of muscle fibers

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13
Q

What causes long duration large amplitude (LDLA) MUAPs on EMG?

A

Polyphasic potentials are due to collateral sprouting

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14
Q

What causes long duration unstable MUAPs on EMG?

A

These variable amplitude potentials are due to blocking of immature NMJs, which are formed at the beginning of collateral sprouting

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15
Q

What can be demonstrated on single fiber EMG in myopathy?

A

Increased jitter, FD, and blocking

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16
Q

Which disorders have type I fiber atrophy on muscle biopsy?

A
  • Myotonic dystrophy
  • Nemaline rod myopathy
  • Fiber type disproportion
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17
Q

Which disorders have type II fiber atrophy on muscle biopsy?

A
  • Steroid myopathy
  • Myasthenia gravis
  • Deconditioning
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18
Q

What is the etiology of Duchenne Muscular Dystrophy?

A

X-linked recessive (xp21), spontaneous

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19
Q

What is the onset of Duchenne Muscular Dystrophy?

A

3 to 5 years old

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20
Q

What is the course of Duchenne Muscular Dystrophy?

A

Severely progressive (death by 20s)

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21
Q

What is the clinical presentation of Duchenne Muscular Dystrophy?

A 
Proximal muscle weakness
Inc lumbar lordosis
Scoliosis
Calf pseudohypertrophy
Possible MR
Toe walking <5 years
Clumsy running <7 years
WC by 12 yo
Contractures: ITB first, Achilles tendon
Gower's sign
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22
Q

What is seen on muscle biopsy in Duchenne Muscular Dystrophy?

A

No dystrophin

Internal nuclei variation in fiber size

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23
Q

What are seen on labs in Duchenne Muscular Dystrophy?

A

Increased CPK and aldolase

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24
Q

When should surgery be done for scoliosis in Duchenne Muscular Dystrophy?

A

Before the vital

capacity is below 35% (usually due to a curve of >30°).

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25
Q

What is the etiology of Beck Muscular Dystrophy?

A

X-linked recessive

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26
Q

What is the onset of Becker Muscular Dystrophy?

A

Adulthood

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27
Q

What is the course of Becker Muscular Dystrophy?

A

Slowly progressive

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28
Q

What is the clinical presentation of Becker Muscular Dystrophy?

A
  • Proximal weakness
  • Calf pseudohypertrophy
  • Cardiomyopathy
  • Less mental retardation than DMD
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29
Q

What is seen on muscle biopsy of Becker Muscular Dystrophy?

A

Decreased dystrophin

15% to 85%

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30
Q

What is seen in labwork in Becker Muscular Dystrophy?

A

Increased CPK

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31
Q

What is the etiology of Myotonic dystrophy?

A

Autosomal dominant

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32
Q

What is the onset of Myotonic dystrophy?

A

Infancy

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33
Q

What is the clinical presentation of Myotonic dystrophy?

A 
Distal > proximal myotonia with
sustained grip
Hatchet face
Frontal balding
Poor vision/Ptosis
Hypertrichosis
Impotence
MR
Cardiac/Endocrine ABN
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34
Q

Describe the appearance of hatchet face.

A

Wasting of the temporalis and

masseter

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35
Q

What are clinical features specific to Congenital myotonic dystrophy?

A

“Shark mouth” appearance
Facial diplegia
Possible club foot

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36
Q

What is seen on muscle biopsy in Myotonic Dystrophy?

A

Type I fiber atrophy Type II hypertrophy

No dystrophin involvement

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37
Q

What medications can be used in treatment of Myotonic Dystrophy?

A

Procainamide
Dilantin
Quinine (PDQ)

38
Q

What is etiology and onset of Central Core Disease?

A

Autosomal dominant

Infancy

39
Q

What is clinical presentation of Central Core Disease?

A 
• Floppy infant/hypotonia
• Proximal weakness
• Congenital hip dislocation
• Delayed milestones
• Associated with malignant
hyperthermia
40
Q

What is seen on muscle biopsy in Central Core Disease?

A

Central cores in Type I fibers

Absent mitochondria

41
Q

What is the etiology and onset of Nemaline Rod Myopathy?

A

Autosomal dominant/ Recessive

Infancy

42
Q

What is clinical presentation of Nemaline Rod Myopathy?

A
  • Floppy infant/hypotonia
  • Diffuse weakness
  • Facial involvement
  • Narrowed long face
  • High arched palate
  • Foot drop
43
Q

What is the typical cause of death in Nemaline Rod Myopathy?

A

Respiratory failure

44
Q

What is seen on muscle biopsy in Nemaline Rod Myopathy?

A

Rod-shaped bodies on Gomori trichrome stain

45
Q

What is the etiology and onset of Centronuclear myotubular myopathy?

A

X-linked recessive

Infancy

46
Q

What is the clinical presentation of Centronuclear myotubular myopathy?

A 
Floppy infant/hypotonia
• Ptosis
• Extra ocular muscle
involvement
• Facial diplegia
• Dysphagia
• Respiratory insufficiency
47
Q

What is seen on muscle biopsy in Centronuclear myotubular myopathy?

A

Central location

of fiber nuclei, forming chains

48
Q

What is the etiology and onset of Fiber Type Disproportion?

A

Variable inheritance

Infancy

49
Q

What is the clinical presentation of Fiber Type Disproportion?

A
  • Floppy infant/hypotonia
  • Hip contractures
  • Hip dislocations
50
Q

What is seen on muscle biopsy in Fiber Type Disproportion?

A

Numerous small Type I and normal to

large Type II fibers

51
Q

What is the etiology of Polymyositis/ Dermatomyositis?

A

Autoimmune
Connective tissue disorder
Infection
Cancer

52
Q

What is the clinical presentation of both Polymyositis/ Dermatomyositis?

A

• Symmetrical proximal weakness: Hips
followed by shoulders
• Neck flexion weakness
• Myalgias, dysphagia, dysphonia

53
Q

What is the clinical presentation specific to Dermatomyositis?

A

Periorbital violet rash and edema
Gottron’s sign: Red-purple patches
over the knuckles, elbows, knees

54
Q

What is seen in lab work of Polymyositis/ Dermatomyositis?

A

Increased CPK, ESR, aldolase,

SGOT, SGPT, LDH

55
Q

What is seen on muscle biopsy in Polymyositis/ Dermatomyositis?

A

Necrosis of the Type I

and II fibers. Perifascicular atrophy

56
Q

What is the etiology of Inclusion Body Myositis?

A

Unknown

57
Q

What is the clinical presentation of Inclusion Body Myositis?

A

Asymmetric, slowly progressive, painless weakness in proximal
and distal muscles

58
Q

What is associated with Inclusion Body Myositis?

A

Polyneuropathy

59
Q

What is the age distribution of Inclusion Body Myositis?

A

Adults 45 to 55 years

and peaks at 70 years

60
Q

What is seen in lab work of Inclusion Body Myositis?

A

Increase in CK muscle

61
Q

What is on muscle biopsy in Inclusion Body Myositis?

A

Rimmed or cytoplasmic/ basophilic vacuoles
Eosinophilic
inclusion bodies

62
Q

What is the etiology of McArdle disease (Type V metabolic myopathy)?

A

Autosomal recessive

Myophosphorylase deficiency

63
Q

What is the onset of McArdle disease (Type V metabolic myopathy)?

A

<15 years of age

64
Q

What is the clinical presentation of McArdle disease (Type V metabolic myopathy)?

A
  • Exercise intolerance
  • Easy fatigability
  • Muscle stiffness
  • Cramping
  • Second-wind phenomenon
65
Q

What can happen with exercise in McArdle disease (Type V metabolic myopathy)?

A

Strenuous exercise can precipitate myolysis (possibly cause renal failure and death)

66
Q

What is the etiology of Pompe’s disease (Type III metabolic myopathy)?

A

Autosomal recessive

Acid maltase deficiency

67
Q

What is the onset of Pompe’s disease (Type III metabolic myopathy)?

A

Infant to adult

68
Q

What is the clinical presentation of Pompe’s disease (Type III metabolic myopathy)?

A
  • Hypotonia
  • Tongue enlargement
  • Cardiomegaly
  • Hepatomegaly
  • Respiratory insufficiency
  • Death by 2 years of age
  • A milder form may affect adults
69
Q

What is the etiology of Hyperkalemic Periodic Paralysis?

A

Autosomal dominant

Multiple secondary causes

70
Q

What is the onset of Hyperkalemic Periodic Paralysis?

A

Childhood–second decade

71
Q

What is the clinical presentation of Hyperkalemic Periodic Paralysis?

A 
• Proximal muscle weakness
• Paresthesias of the lips and lower limbs
• Myotonia
• Attacks last 10 to 60 min
• May be aborted with exercise
• Exacerbated with cold exposure and
rest following exercise
72
Q

What is seen on labwork of Hyperkalemic Periodic Paralysis?

A

High K+ during the attack

73
Q

What the treatment of Hyperkalemic Periodic Paralysis?

A

High carbohydrate diet

74
Q

What the etiology of Hypokalemic Periodic Paralysis?

A

Autosomal dominant

Multiple secondary causes

75
Q

What the onset of Hypokalemic Periodic Paralysis?

A

Starts in early second decade

76
Q

What the clinical presentation of Hypokalemic Periodic Paralysis?

A 
• Weakness starts in the legs and
spreads proximally
• Attacks last 12 to 24 hours
• Myotonia seen in the eyelids
• Exacerbated with rest after exercise,
stress, and a high carbohydrate diet
77
Q

What is seen on labwork of Hypokalemic Periodic Paralysis?

A

Low potassium
Muscle biopsy
normal

78
Q

What is the treatment of Hypokalemic Periodic Paralysis?

A

K+ supplement

79
Q

What are different names for Myotonia Congenita?

A

Thomsen’s disease

Little Hercules

80
Q

What is the etiology and onset of Myotonia Congenita?

A

Autosomal dominant

Birth–adulthood

81
Q

What is the clinical presentation of Myotonia Congenita?

A
  • Severe spasms exacerbated by the cold
  • Improves with warmth and exercise
  • Muscle hypertrophy
  • Myotonia
  • No weakness
82
Q

What are treatments for Myotonia Congenita?

A

Procainamide
Dilantin,
quinine (PDQ)

83
Q

What is the etiology and onset of Paramyotonia congenita (Eulenburg)?

A

Autosomal dominant

Birth–adulthood

84
Q

What is the clinical presentation of Paramyotonia congenita (Eulenburg)?

A
  • Stiffness
  • Weakness
  • Fatigue
  • Myotonia
  • Exacerbated with cold and exercise
85
Q

What is the treatment of Paramyotonia congenita (Eulenburg)?

A

Warm extremities

86
Q

What is the etiology of steroid myopathy?

A

Corticosteroid proteolysis effect

87
Q

What is the clinical presentation of steroid myopathy?

A

• Proximal muscle weakness
• Risk is increased if on 30 mg / day
• Preferentially affects the hip girdle
muscles

88
Q

What is seen on muscle biopsy of steroid myopathy?

A

Type II atrophy

89
Q

What is the clinical presentation of statin myopathy?

A

• Proximal weakness and pain
• Worse with exercise
• Lipophilic statins are more likely to produce muscular effects,
than are relatively hydrophilic agents

90
Q

What are liophilic statins?

A

Simvastatin
Atorvastatin
Lovastatin

91
Q

What are hydrophilic statins?

A

Pavastatin
Rosuvastatin
Fluvastatin)

92
Q

What are treatments of statin myopathy?

A

Stop statins, or stop medications that
interfere with Cy-P450: macrolide antibiotics, verapamil, diltiazem,
cimetidine, etc.

BR 3rd Ed (92 decks)

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