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MSK/Rheum path > Neuromuscular diseases > Flashcards

Neuromuscular diseases Flashcards

Anatomic locations of NM diseases; neurological signs/Sx distinguishing disorders affecting anterior horns, peripheral nerves, NMJ and muscle; Dx testing for NM diseases-electrodiagnosis;

1
Q

Define poly-neuropathies

A

diffuse diseases of peripheral nerves

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2
Q

Define focal neuropathies

A

diseases that affect individual nerves or only hte nerve roots or plexi

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3
Q

Define radiculopathies

A

weakness in muscles innervated by that nerve or a particular nerve or root or numbness in respective dermatomes

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4
Q

What are the symptoms of focal neuropathies?

A

only the anatomical territory innvervated by that nerve or nerve root involved in radiculopathies

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5
Q

Where do motor neuron diseases affect? Name 2

A

anterior horn cells (motor neurons);

spinal muscular atrophy, amyotrophic lateral sclerosis (may be upper neurons)

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6
Q

What else other than the anterior horn cells are affected in motor neuron diseases?

A

motor axons and muscle fibers innervated by them are secondarily affected

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7
Q

What is affected in peripheral neuropathies?

A

motor axons but various nerve fibers that carry Pain and Proprioceptive sensations;
Autonomic fibers

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8
Q

What types of problems do peripheral neuropathies cause?

A

sensory or autonomic problems

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9
Q

In a patient suffering from myopathy, what sign is present and what does this indicate?

A

Gower’s sign due to muscle weakness (common Sx) primarily in proximal muscles

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10
Q

Describe Gower’s sign/manuever

A

patient has trouble getting off the floor from proximal muscle weakness so must “climb over his legs”

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11
Q

What is the difference in poly-neuropathies and motor neuron diseases?

A

PNP=> distal muscle weakness/wasting WITH decreased sensations and depressed reflexes

MND=> NO sensory deficits as only motor axons are affected

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12
Q

A patient presents with inability to dorsiflex left foot but can on others suffers from what?

A

Mononeuropathy

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13
Q

Myasthenia gravis is what type of NM disease? Test for it?

A

NM transmission disease;

prolonged upward gaze will lead to droopy eyelids (ptosis) after a period of time

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14
Q

What does an EMG measure?

A

Summation of action potentials from muscle fibers of a motor unit called Motor Unit Action Potentials (MUAPs)

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15
Q

T/F A motor neuron and fibers that it innervates belong to only 1 type

A

True

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16
Q

What is a indication on histopathology that a muscle has lost its innervation?

A

dark staining with nonspecific esterase and the MUSCLE FIBERS BECOME ATROPHIC AND ANGULATED

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17
Q

What is type grouping

A

sprouting of axons from intact neurons take over and reinnverate damaged fibers leading to groups forming of both fiber types

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18
Q

What type of AP will be generated from type grouping?

A

larger due to more muscle fibers innervated by single motor neuron but AP number will be decreased

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19
Q

How do muscle fibers appear in myopathies?

A

NOT atrophic or angular but differ depending on the cause:
Necrotic => pale from autoimmune myopathy
Structural

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20
Q

How does the muscle act in myopathies?

A

ill/nonfxnal so APs are smaller but may be polyphasic due to asynchronous depolarization of individual fibers of motor unit

21
Q

Differentiate myopathies and neurogenic disorders with regards to motor units

A

myopathies do NOT have a decreased number of motor units but just provide weak response due to testing

22
Q

How do you characterize muscle disease?

A

decrease in number of muscle fibers per motor unit

23
Q

Define distal latency

A

time it takes for AP to travel from stimulus to response sight

24
Q

How is nerve conduction velocity calculated?

A

dividing the distance in centimeters by latency difference in milliseconds

M/sec

25
Q

Describe muscle weakness, sensation and reflexes with myopathies

A

weakness usually proximal and symmetrical; sensation and reflexes are normal

26
Q

How wil myopathies present on EMG?

A

MUAPs small and short duration while being polyphasic

27
Q

Differentiate muscular dystrophy from myotonic dystrophy

A

Both are hereditary and progressive weakness diseases but

MYOTONIC dystrophy patients have a difficult time relaxing muscles (myotonia)

28
Q

A floppy baby suffering from a congenital myopathy may be deficient in what enzyme?

A

Maltase deficiency leading to infantile acid maltase deficiency

29
Q

Define Duchenne’s muscular dystrophy

A

XLR-childhood disorder that is caused by a deletion of the dystrophin gene

30
Q

Clinical Manifestations of DMD

A

progressive muscle weakness;
pseudohypertrophy;
abnormal heart;
Low IQ

31
Q

What is the effect on muscle from DMD?

A

necrosis; atrophy; segmental fiber over contraction

32
Q

How does muscle atrophy occur in DMD patients?

A

lack of dystrophin in muscle membrane allows secondary calcium entrance that triggers necrosis and atrophy

33
Q

Differentiate BMD from DMD

A

milder that may present later in life due to the protein undergoing a point mutation and not a deletion

34
Q

What type of genetics are associated with myotonic dystrophy?

A

Autosomal dominant with increased CGT repeats of DNA on chromosome 19

ANTICIPATION => increased repeat expansions and more severe phenotypes in younger generations

35
Q

What typically causes inflammatory myopathies?

A

ACQUIRED
AI;
polymyositis, dermatomyositis, inclusion body, sarcoidosis;
infections (trichinosis)

36
Q

What causes metabolic myopathies?

A

enzyme deficiencies that blocks metabolic pathways depriving muscle with energy for contraction and relaxation and to maintain membrane integrity

37
Q

A patient suffering from a disorder of glycogen metabolism tried to workout but had extreme muscle pain. A test revealed myoglobinuria. What is the patient suffering from?

A

Metabolic myopathy causing rhabdomyolysis that could be McArdle’s disease

38
Q

What enzyme is deficient in McArdle’s disease?

A

muscle phosphorylase deficiency

39
Q

What type of labs will be present in McArdle’s disease?

A

even after extreme ischemic exercise, lactate is not present when it should be as glycogenolysis uses it for energy

40
Q

How do endocrine disorders present?

A

proximal muscle weakness and biopsies show non-specific findings and ONLY type II muscle fiber atrophy

41
Q

Hyperparathyroidism is an endocrine myopathy. What is the presentation?

A

severe weakness resembling amyotrophic lateral sclerosis

42
Q

Hypoparathyroidism is a endocrine myopathy. How might it present?

A

muscle spasms but NOT weakness;
very high serum creatine kinase levels;

obese patients w/ hyperlipidemia and high serum creatine may also have similar findings

43
Q

Toxic myopathies are associated with what typically?

A 
Muscle fiber atrophy;
vacuolization;
myofibrillary degeneration;
Mt dysfxn
fiber necrosis
44
Q

Define myasthenia gravis

A

acquired disease characterized by fluctuating muscle weakness that worsens with activity due to Abs binding and destroying muscle Ach receptors

double vision and proximal limb weakness along with difficulty swallowing and breathing

45
Q

What test helps with Diagnosis of myasthenia gravis? and how does it work?

A

edrophonium (or tensilon) test => short acting anti-cholinesterase drug that produces rapid improvement of weakness from ptosis even after upward gaze

46
Q

When measuring AP in myasthenia gravis patients, how will they present?

A

APs get smaller at slow stimulation rates

47
Q

How will patients with botulism or Eaton Lambert syndrome present with nerve stimulation?

A

APs are small and get smaller with slow stimulation rates but…

Large increment in amplitude during fast stimulations

48
Q

With regards to receptors, what is the difference in Eaton Lambert syndrome and myasthenia gravis?

A

ELS affects from the NM transmission on the nicotinic receptors and affects the autonomic ganglia synaptic muscarinic receptors

MSK/Rheum path (22 decks)

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