Non-Inflammatory myopathies - Bertorini

Question 1

Neuromuscular diseases consist of what 4 categories?

Answer 1

• Motor neuron disease
• Peripheral neuropathy
• Disorders of NMJ
• Primary disorders of muscle fibers

Question 2

List the NMJ diseases?

Answer 2

Myasthenia Gravis

Lambert-Eaton Syndrome

Question 3

List the types of myopathies?

Answer 3

• Congenital Myopathies
• Muscular Dystrophies
• Myotonic Dystrophies
• Metabolic Myopathy
• Endocrine Myopathy
• Toxic Myopathy
• Inflammatory Myopathy

Question 4

List the 2 types of Muscular dystrophies?

Answer 4

X-linked (Duchenne’s)

Becker’s

Question 5

“Floppy infants” what type of myopathy?

Answer 5

Congenital Myopathy

Question 6

Metabolic myopathy?

Answer 6

McArdle’s Disease

Question 7

Alcoholics associated with what type of neuromuscular disease?

Answer 7

Peripheral neuropathy

Question 8

Which neuromuscular disease is associated with distal muscle involvement?

Answer 8

Peripheral neuropathy

Question 9

Muscle weakness + sensory involvement. Which type?

Answer 9

Peripheral Neuropathy

Question 10

Elevated CK in which type of neuromusclar disease?

Answer 10

Myopathies

Question 11

Which neuromuscular disease is associated with slowed conduction velocity?

Answer 11

Peripheral neuropathy

Question 12

What 2 types of neuromuscular diseases have similar muscle biopsies?

List these features?

Since muscle biopsies are the same, what else will be the same?

Answer 12

Motor neuron disease & peripheral neuropathy

Will have denervation repesented by:

1. Atrophic angular target fibers
2. Fiber type grouping
3. Group atrophy

EMG findings will be the same for these 2 groups

Question 13

What does fiber type grouping mean? Which neuromuscular disease(s) is/are they associated with?

Answer 13

More muscle fibers innervated by a single motor neuron

Seen with motor neuron diseases and peripheral neuropathy

Question 14

Myopathies associated with what 2 findings on muscle biopsy?

Answer 14

Disseminated necrosis, inflammation

Question 15

Which neuromuscular disease is associated with normal muscle biopsy?

Answer 15

NMJ diseases

Question 16

Steppage gait (foot drop) seen in what neuromuscular disease?

Answer 16

Peripheral neuropathy

Question 17

Which 2 neuromuscular diseases have similar EMG findings? List these features?

Answer 17

Motor neuron diseases, peripheral neuropathy

EMG shows:

1) Decreased # of motor units (action potentials)
2) Increased amplitude (due to fiber type grouping)

Question 18

EMG findings of myopathies (3)?

Answer 18

• Normal # of motor units (action potentials) but shorter in duration
• Decreased amplitude (less # of muscle fibers per motor unit)
• Polyphasic

Question 19

Muscle weakness of pelvic girdle associated with what neuromuscular diseases?

Answer 19

Myopathies (specifically muscular dystrophies)

Question 20

Polyphasic findings on EMG. What neuromuscular disease? What is the reason for these findings?

Answer 20

Myopathies

Polyphasic means muscler fibers of a motor unit are not in sync, not firing all at once.

Question 21

Deletion of dystrophin? What disease?

Answer 21

X-linked (Duchenne’s) muscular dystrophy

Question 22

Genetic difference between X-linked and Becker’s muscular dystrophy? Which one is worse?

Answer 22

Becker’s is a mutation in dystrophin

X-linked is a deletion = much worse

Question 23

Mode of inheritence of Duchenne’s?

Answer 23

X-linked recessive

Question 24

Only neuromuscular disease that has sensory involvement?

Answer 24

Peripheral neuropathy. Probably asked this question about 3 different times now

Question 25

Main difference between muscular dystrophies and myotonic dystrophies?

Answer 25

Muscular dystrophy = muscle weakness

Myotonic dystrophy = muscle weakness + difficulty relaxing muscle (myotonia)

Question 26

Coke colored urine after exercise + muscle cramps. What disease?

What enzyme will be elevated?

What’s causes color in the urine?

Answer 26

McArdle’s disease,

High CK

Myoglobin in urine

Question 27

McArdle’s disease is associated with what deficiency? What is the effect of this defiency?

Answer 27

Muscle phosphorylase defiency

Glycogen cannot break down during exercise to produce ATP, lactate and pyruvate necessary for oxidative phosphorylation

Question 28

In McArdle’s, what enzyme remains “normal” during exercise? Is this a good thing?

Answer 28

Lactate will not increase. Normally, it should. This lack of increase indicates that glycogen is not being used as energy source when it is supposed to (anaerobic).

Question 29

Muscle biopsy of McArdle’s

Answer 29

Muscle necrosis and phosphorylase deficiency

Question 30

What is the ischemic exercise test? When is it used?

Answer 30

Used in glycogen storage diseases, because of lack of normal rise of serum lactate during exercise in glycogenesis.

Question 31

Myasthenia gravis is associated with autoantibodies against what?

Answer 31

Postsynaptic AcH receptors on postsynapse of NMJ

Question 32

What tests (2) would you order to confirm diagnosis of myasthenia gravis?

Answer 32

Ach receptor antibody test, Repetitive stimulation test

Question 33

Myasthenia gravis classically involves what organ? What occurs in this organ as a result?

Answer 33

Eye, causes ptosis and diplopia

Question 34

Describe muscle weakness seen in myasthenia gravis? What drug improves these symptoms?

Answer 34

muscle weakness that worsens with use and improves with rest

• symptoms improve with anticholinesterase agents

Question 35

If patient has a thymectomy and their symptoms improve, what neuromuscular disease are you thinking of?

Answer 35

Myasthenia gravis, can be associated with thymic hyperplasia or thymoma

Question 36

What disease is associated with autoantibodies against presynpatic Ca2+ channels? What occurs at these channels?

Answer 36

Lambert-Eaton Syndrome, will not allow Ca2+ into the presynapse, thus no Ach is release into the synpase

Question 37

Describe main difference in muscle weakness features b/t myasthenia gravis and lambert-eaton?

Answer 37

Myasthenia gravis - muscle weakness worsens with use and improves with rest. Eyes usually involved

Lambert eaton - Proximal muscle weakness that improves with use; eyes usually spared

Question 38

What 2 tests would you like to do to confirm lambert eaton?

Answer 38

Repetitive stimulation test, EMG/NCV (nerve conduction velocities)

Question 39

If you perform repetitive stimulation test and muscle function improves, is it myasthenia gravis or lambert eaton? Describe mechanism?

Answer 39

Lambert eaton improves with repetitive stimulation bc each stimulatory effect causes more calcium to want to flow into presynapse through channels that are being competitively inhibited. Flow of Ca2+ in, causes AcH to be release into synapse, causes muscle to work.

Repetitive stimulation in myasthenia gravis will actually worsen the symptoms, bc each successive stimulation will cause less and less AcH to be release into synapse, thus the already blocked AcH receptors wont respond to the low levels.

Question 40

What cancer most commonly causes Lambert-Eaton?

% affected?

Answer 40

Roughly 40-50% of patients with Lambert - Eaton were caused by small cell lung cancer.

Question 41

What drug type won’t improve Lambert-Eaton?

Answer 41

Acetylcholinesterase inhibitors. Enzyme has nothing to act on. Theres not Ach being released anyways so they cant prevent the breakdown of something that isnt there

Question 42

Treatment for Lambert Eaton?

Answer 42

3-4 aminopiridine (stimulates AcH release) and immunosuppression