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

Ch 5 - EDX: Myopathies Flashcards

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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
What is the etiology of Beck Muscular Dystrophy?
X-linked recessive
26
What is the onset of Becker Muscular Dystrophy?
Adulthood
27
What is the course of Becker Muscular Dystrophy?
Slowly progressive
28
What is the clinical presentation of Becker Muscular Dystrophy?
* Proximal weakness * Calf pseudohypertrophy * Cardiomyopathy * Less mental retardation than DMD
29
What is seen on muscle biopsy of Becker Muscular Dystrophy?
Decreased dystrophin | 15% to 85%
30
What is seen in labwork in Becker Muscular Dystrophy?
Increased CPK
31
What is the etiology of Myotonic dystrophy?
Autosomal dominant
32
What is the onset of Myotonic dystrophy?
Infancy
33
What is the clinical presentation of Myotonic dystrophy?
``` Distal > proximal myotonia with sustained grip Hatchet face Frontal balding Poor vision/Ptosis Hypertrichosis Impotence MR Cardiac/Endocrine ABN ```
34
Describe the appearance of hatchet face.
Wasting of the temporalis and | masseter
35
What are clinical features specific to Congenital myotonic dystrophy?
“Shark mouth” appearance Facial diplegia Possible club foot
36
What is seen on muscle biopsy in Myotonic Dystrophy?
Type I fiber atrophy Type II hypertrophy | No dystrophin involvement
37
What medications can be used in treatment of Myotonic Dystrophy?
Procainamide Dilantin Quinine (PDQ)
38
What is etiology and onset of Central Core Disease?
Autosomal dominant | Infancy
39
What is clinical presentation of Central Core Disease?
``` • Floppy infant/hypotonia • Proximal weakness • Congenital hip dislocation • Delayed milestones • Associated with malignant hyperthermia ```
40
What is seen on muscle biopsy in Central Core Disease?
Central cores in Type I fibers | Absent mitochondria
41
What is the etiology and onset of Nemaline Rod Myopathy?
Autosomal dominant/ Recessive | Infancy
42
What is clinical presentation of Nemaline Rod Myopathy?
* Floppy infant/hypotonia * Diffuse weakness * Facial involvement * Narrowed long face * High arched palate * Foot drop
43
What is the typical cause of death in Nemaline Rod Myopathy?
Respiratory failure
44
What is seen on muscle biopsy in Nemaline Rod Myopathy?
Rod-shaped bodies on Gomori trichrome stain
45
What is the etiology and onset of Centronuclear myotubular myopathy?
X-linked recessive | Infancy
46
What is the clinical presentation of Centronuclear myotubular myopathy?
``` Floppy infant/hypotonia • Ptosis • Extra ocular muscle involvement • Facial diplegia • Dysphagia • Respiratory insufficiency ```
47
What is seen on muscle biopsy in Centronuclear myotubular myopathy?
Central location | of fiber nuclei, forming chains
48
What is the etiology and onset of Fiber Type Disproportion?
Variable inheritance | Infancy
49
What is the clinical presentation of Fiber Type Disproportion?
* Floppy infant/hypotonia * Hip contractures * Hip dislocations
50
What is seen on muscle biopsy in Fiber Type Disproportion?
Numerous small Type I and normal to | large Type II fibers
51
What is the etiology of Polymyositis/ Dermatomyositis?
Autoimmune Connective tissue disorder Infection Cancer
52
What is the clinical presentation of both Polymyositis/ Dermatomyositis?
• Symmetrical proximal weakness: Hips followed by shoulders • Neck flexion weakness • Myalgias, dysphagia, dysphonia
53
What is the clinical presentation specific to Dermatomyositis?
Periorbital violet rash and edema Gottron’s sign: Red-purple patches over the knuckles, elbows, knees
54
What is seen in lab work of Polymyositis/ Dermatomyositis?
Increased CPK, ESR, aldolase, | SGOT, SGPT, LDH
55
What is seen on muscle biopsy in Polymyositis/ Dermatomyositis?
Necrosis of the Type I | and II fibers. Perifascicular atrophy
56
What is the etiology of Inclusion Body Myositis?
Unknown
57
What is the clinical presentation of Inclusion Body Myositis?
Asymmetric, slowly progressive, painless weakness in proximal and distal muscles
58
What is associated with Inclusion Body Myositis?
Polyneuropathy
59
What is the age distribution of Inclusion Body Myositis?
Adults 45 to 55 years | and peaks at 70 years
60
What is seen in lab work of Inclusion Body Myositis?
Increase in CK muscle
61
What is on muscle biopsy in Inclusion Body Myositis?
Rimmed or cytoplasmic/ basophilic vacuoles Eosinophilic inclusion bodies
62
What is the etiology of McArdle disease (Type V metabolic myopathy)?
Autosomal recessive | Myophosphorylase deficiency
63
What is the onset of McArdle disease (Type V metabolic myopathy)?
<15 years of age
64
What is the clinical presentation of McArdle disease (Type V metabolic myopathy)?
* Exercise intolerance * Easy fatigability * Muscle stiffness * Cramping * Second-wind phenomenon
65
What can happen with exercise in McArdle disease (Type V metabolic myopathy)?
Strenuous exercise can precipitate myolysis (possibly cause renal failure and death)
66
What is the etiology of Pompe's disease (Type III metabolic myopathy)?
Autosomal recessive | Acid maltase deficiency
67
What is the onset of Pompe's disease (Type III metabolic myopathy)?
Infant to adult
68
What is the clinical presentation of Pompe's disease (Type III metabolic myopathy)?
* Hypotonia * Tongue enlargement * Cardiomegaly * Hepatomegaly * Respiratory insufficiency * Death by 2 years of age * A milder form may affect adults
69
What is the etiology of Hyperkalemic Periodic Paralysis?
Autosomal dominant | Multiple secondary causes
70
What is the onset of Hyperkalemic Periodic Paralysis?
Childhood–second decade
71
What is the clinical presentation of Hyperkalemic Periodic Paralysis?
``` • 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
What is seen on labwork of Hyperkalemic Periodic Paralysis?
High K+ during the attack
73
What the treatment of Hyperkalemic Periodic Paralysis?
High carbohydrate diet
74
What the etiology of Hypokalemic Periodic Paralysis?
Autosomal dominant | Multiple secondary causes
75
What the onset of Hypokalemic Periodic Paralysis?
Starts in early second decade
76
What the clinical presentation of Hypokalemic Periodic Paralysis?
``` • 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
What is seen on labwork of Hypokalemic Periodic Paralysis?
Low potassium Muscle biopsy normal
78
What is the treatment of Hypokalemic Periodic Paralysis?
K+ supplement
79
What are different names for Myotonia Congenita?
Thomsen's disease | Little Hercules
80
What is the etiology and onset of Myotonia Congenita?
Autosomal dominant | Birth–adulthood
81
What is the clinical presentation of Myotonia Congenita?
* Severe spasms exacerbated by the cold * Improves with warmth and exercise * Muscle hypertrophy * Myotonia * No weakness
82
What are treatments for Myotonia Congenita?
Procainamide Dilantin, quinine (PDQ)
83
What is the etiology and onset of Paramyotonia congenita (Eulenburg)?
Autosomal dominant | Birth–adulthood
84
What is the clinical presentation of Paramyotonia congenita (Eulenburg)?
* Stiffness * Weakness * Fatigue * Myotonia * Exacerbated with cold and exercise
85
What is the treatment of Paramyotonia congenita (Eulenburg)?
Warm extremities
86
What is the etiology of steroid myopathy?
Corticosteroid proteolysis effect
87
What is the clinical presentation of steroid myopathy?
• Proximal muscle weakness • Risk is increased if on 30 mg / day • Preferentially affects the hip girdle muscles
88
What is seen on muscle biopsy of steroid myopathy?
Type II atrophy
89
What is the clinical presentation of statin myopathy?
• Proximal weakness and pain • Worse with exercise • Lipophilic statins are more likely to produce muscular effects, than are relatively hydrophilic agents
90
What are liophilic statins?
Simvastatin Atorvastatin Lovastatin
91
What are hydrophilic statins?
Pavastatin Rosuvastatin Fluvastatin)
92
What are treatments of statin myopathy?
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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