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NYCC MSP > Other Myopathies + Denervation > Flashcards

Other Myopathies + Denervation Flashcards

1
Q

What is the etiology of Myasthenia Gravis?

A

acquired autoimmune Dz: develop Ab’s to Ach receptors at neuromuscular junction
(15% have thymoma)

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2
Q

What demographic is primarily affected by Myasthenia Gravis?

A
  • younger women (20-30)
  • older men (>50)
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3
Q

What is the primary symptom of Myasthenia Gravis?

A

abnormal muscular fatigability & weakness

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4
Q

What are the clinical manifestations of Myasthenia Gravis?

A
  • can be very acute onset (days)
  • m. weakness & fatigue
  • Extraocular mm (ptosis, diplopia) fatigued w/ repeated H-pattern
  • facial changes (mask-like, snarl)
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5
Q

How do antibodies in Myasthenia Gravis affect the neuromuscular junction?

A
  • destruction of Ach receptors = less surface area
  • ^gap between n. ending & m.
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6
Q

In a patient presenting with symptoms of Myasthenia Gravis, what do you need to rule out first?

A

stroke

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7
Q

How would a thymoma cause Myasthenia Gravis?

A

residual thymus/benign tumor results in ^T-cells

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8
Q

What are the possible treatments for Myasthenia Gravis?

A
  • thymectomy
  • corticosteroids
  • methotrexate
  • anticholinesterase drugs
  • plasmapheresis (reduces anti-Ach receptor Ab’s)
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9
Q

What is another, better term for Myositis ossificans?

A

Heterotropic Bone Formation

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10
Q

What tissues does Myositis ossificans occur in?

A

muscle

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11
Q

What tissues does Heterotropic Bone Formation occur in?

A
  • most often in muscle
  • can occur in fascia, tendons, jt capsule, fat
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12
Q

What is Heterotropic Bone Formation?

A

metaplasia of soft tissue to bone following trauma (crushing; hip replacement)/contusion

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13
Q

Name the 3 stages of Heterotropic Bone Formation

A
  1. pseudosarcoma
  2. differentiation
  3. maturation
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14
Q

What is the time period for the pseudosarcoma stage of Heterotropic Bone Formation?

A

4-6 wks

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15
Q

What is the time period for the differentiation stage of Heterotropic Bone Formation?

A

2-3 mo

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16
Q

What is the time period for the maturation stage of Heterotropic Bone Formation?

A

variable

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17
Q

Where is the greatest damage during the pseudosarcoma stage of Heterotropic Bone Formation?

A

center of injury

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18
Q

Describe the pathogenesis of Heterotropic Bone Formation

A
  • trauma –> hematoma
  • ^^damage & cell death
  • holes appear in sarcolemma –> fluid accumulates
  • phagocytes make holes larger
  • damaged tissue liquefied & replaced by sheets of non-specific cells
  • after 15 days: ^^proliferation of mesenchymal tiss.
  • minimal osteoid formation
19
Q

What can aggravate the process of the pseudosarcoma stage of Heterotropic Bone Formation?

A

trauma, massage, stretching, surgery, ^activity, ultrasound

20
Q

How does Heterotropic Bone Formation appear histologically during the pseudosarcoma stage?

A

looks like neoplasia

21
Q

What can Heterotropic Bone Formation in the pseudosarcoma stage be mistaken for? Why?

A

Osteosarcoma
- rapid cell division in this stage
- hazy ossification in soft tissue looks like periosteal Rxn

22
Q

How would you differentiate Heterotropic Bone Formation from an Osteosarcoma?

A
  • HBF has a history of trauma
  • Zonal phenomenon is opposite of osteosarc. which ossifies from inside out
23
Q

Describe the pathogenesis of the differentiation stage of Heterotropic Bone Formation

A
  • mesenchymal cells differentiate into fibroblasts, chondroblasts, osteoblasts (metaplasia)
  • giant cells remove debris
  • periphery mineralizes
  • center remains as fluid-filled cyst (hematoma) or undifferentiated cells
24
Q

What is zonal phenomenon?

A

During differentiation stage of Heterotropic Bone Formation, mature bone develops around periphery
(center remains filled with fluid or undifferentiated cells)

25
Q

Describe the pathogenesis of the maturation stage of Heterotropic Bone Formation

A

develops periosteum separating from surrounding tissues

26
Q

What are the potential outcomes of the maturation stage of Heterotropic Bone Formation?

A
  • remain indefinitely
  • shrink and disappear
  • surgical removal (once matured)
27
Q

What determines that Heterotropic Bone Formation is in the maturation stage?

A

periosteum = mature bone (trabecular + cortical)

28
Q

What are the clinical manifestations of Heterotropic Bone Formation?

A
  • muscle pain
  • decreased ROM
  • hard, palpable lump deep in muscle
  • may be associated w/ neurologic dz
29
Q

What are the radiographic characteristics of Heterotropic Bone Formation?

A
  • hazy ossification in soft tissue early on
  • cortical bone seen in mature stage
30
Q

What is another name for Fibrodysplasia Ossificans Progressiva (FOP)?

A

Progressive Myositis Ossificans

31
Q

What is the etiology of Fibrodysplasia Ossificans Progressiva?

A
  • some cases inherited
  • no Hx of trauma
32
Q

What tissues are involved in Fibrodysplasia Ossificans Progressiva?

A

usually postural muscles (back & major jts)

33
Q

What age group is affected by Fibrodysplasia Ossificans Progressiva?

A

symptoms begin in early childhood (as early as age 2 or by adolescence)

34
Q

What is Fibrodysplasia Ossificans Progressiva?

A

progressive, sheet-like ossification of muscles causing severe functional disability

35
Q

What is the prognosis of Fibrodysplasia Ossificans Progressiva?

A

generally fatal due to loss of pulmonary function
(not treated - any soft tissue work will worsen condition)

36
Q

Denervation affects what fiber type(s)?

A

both type I and II

37
Q

What are some potential etiologies of Denervation?

A
  • diseases causing progressive muscle weakness and atrophy (ALS, spinal muscular atrophies)
  • traumatic (n. root avulsion)
  • compressive (carpal tunnel, peripheral neuropathies)
38
Q

Traumatic and compressive denervation involves ____ neurons

A

LMNs (i.e., peripheral neuropathies)

39
Q

What happens when skeletal muscle fibers become separated from LMNs (denervation)?

A

cells atrophy –> appear dark & angular histologically

40
Q

During denervation, what happens if reinnervation does not occur?

A

atrophy progresses and muscle fibers are replaced by adipose tissue

41
Q

Denervated fibers are initially ____, but as disease progresses they ____

A
  • scattered irregularly
  • cluster
42
Q

What may happen if denervation proceeds slowly?

A
  • reinnervation may keep pace
  • sprouting n. root endings make contact & synapse w/ m. fiber at previous motor end plate
43
Q

What happens as one motor neuron takes over a given field of fibers?

A

fiber type grouping

44
Q

If denervation occurs after fiber type grouping, ____ will occur

A

grouped atrophy

NYCC MSP (44 decks)

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