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Robbins Pathology MSK (Chapters 24,25,26) > Chapter 26- Peripheral Nerves And Muscles > Flashcards

Chapter 26- Peripheral Nerves And Muscles Flashcards

1
Q

What are the portions of myelinated nerves separated by

A

Internodes called Nodes of Ranvier

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2
Q

What supplies the myelin sheat for each internode

A

Single schwann cell

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3
Q

What is the epineurium

A

Enclosed entire nerve

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4
Q

What is the perineurium

A

Multilayered, concentric connective tissue sheath that encloses each fascicle

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5
Q

What is the endometrium

A

Surrounds the individual nerve fiber

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6
Q

What is the result when there is Schwann cell demyelination

A

Segmental demyelination, with loss of myelin

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7
Q

What is the result when there is axonal degeneration

A

Primary involvement of the neuron and its axon

*May be followed by axonal regeneration and reinnervation of muscle

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8
Q

What is a denuded axon

A

Stimulus in the axon for remyelination

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9
Q

What is the length of neurons that have been remelinated following injury

A

Shorter than normal

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10
Q

What is the first thought when there is the appearance of onion bulbing of a neuron

A

There is degeneration of axon as it is losing and unraveling of the myelin

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11
Q

What is a traumatic neuroma

A

There is a trauma to the nerve, and rather than the repairing in the parallel normal fiber pattern, there is haphazard whirled proliferation that is prone to painful nodules

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12
Q

What are myelin ovoids

A

Schwann cell’s catabolize myelin and then later engulf the axon fragments, which produce small oval compartments

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13
Q

What is the result when muscles lose innervation due to axonal degeneration

A

Denervation atrophy

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14
Q

What are angulated fibers

A

Atrophic fibers are smaller and triangular shape when denervation atrophy

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15
Q

What are target fibers when there is axonal degeneration

A

Rounded zone of disorganized myofibers in center of the muscle fiber

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16
Q

What determines the muscle fiber type

A

The motor neuron, as all muscle fibers of a single unit are of the same type

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17
Q

What is steroid atrophy

A

During glucocorticoid therapy, type 2 muscles can atrophy

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18
Q

What is segmental necrosis

A

Destruction of a portion of myocyte, followed by myophagocytosis, which leads to the deposition of collagen and fat

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19
Q

During regeneration of muscle fibers, what changes are seen with regards to the nuclei

A

Regenerating portion has a large, internalized (central location) nuclei with Prominent nucleoli, and cytoplasm that is laden with RNA that is Red

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20
Q

What is mononeuritis pultiplex and what is a common cause

A

Several nerves damaged in a haphazard fashion

*Usually cause by vasculitis, such as polyarteritis nodosum.

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21
Q

What is the cranial nerve that can cause facial muscle paralysis

A

Cranial nerve 7

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22
Q

What is Bell’s palsy

A

One sided facial drooping

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23
Q

What is associated with causing Bell’s palsy

A
  • Upper respiratory infection

- Diabetes mellitus

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24
Q

What are the common causes for neurogenic bladder

A

Aka lack of control of urinary conditions due to an underlying issue

1) Nerve damage (seen in MS or parkinson, or DM)
2) Infection/injury of brain or SC
3) Heavy metal poisoning
4) Spina bifida and other congenital SC issues

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25
Q

What are the state of the reflexes and order or paralysis in Guillain-Barre

A

Deep tendon reflexes disappear

*Ascending paralysis

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26
Q

What are the common caused of GBS

A

*2/3 proceeded by acute influenza like illness

  • CMV
  • EBV
  • Mycoplasma
  • prior vaccination
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27
Q

What portion of the neuron tends to be affected by GBS

A
  • Perivenular and endometrial infiltration with inflammatory cells
  • segmental demyelination
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28
Q

Are antibodies present in GBS

A

Yes, they are antimyelin Abs

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29
Q

What are the cytoplasmic processes involved in GBS

A

Macrophages penetrate basement membrane of Schwann cells, particularly near the Nodes of Ranvier

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30
Q

What are the lab CSF values in the cause of GBS

A
  • Increased protein (due to permeability of spinal roots)

- Normal inflammatory cells (they are confined to the roots)

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31
Q

What are the common causes of death in GBS and what is the treatment

A

Respiratory paralysis
Autonomic instability
Cardiac arrest

*Treatment is plasmaphareisis or IVIg

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32
Q

How is chronic inflammatory demyelination get polyradiculneuropathy differentiated from GBS

A
  • It will respond to steroids

- symptoms will be present for >2 months

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33
Q

What is the classic histological finding in the case of chronic inflammatory demyelinating polyradiculoneuropathy

A

Onion bulbs

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34
Q

What are the characteristics at the neuron level in leprosy

A
  • Segmental demyelination
  • remyelination
  • Loss of both myelination and unmyelinated axons

-Endoneuronal fibrosis and multilayered thickening of perineural sheaths

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35
Q

Which neurons tend to be affected in leprosy

A

Cool extremities (lower temps for the Mycobacterium to growth)

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36
Q

Which fibers tend to be affected in leprosy

A

Pain fibers, with the loss of sensation contributing to injury

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37
Q

What are the neurons that tend to be affected during infection with diptheria

A

Selective demyelination of axons that extend into the anterior and posterior roots, along with mixed sensorimotor nerves q

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38
Q

How does VZV cause damage to neurons

A

Infects the neuron, then causes the loss of the affected ganglion, leading to regional necrosis and hemmorhage

**Loss of the dorsal root sensory ganglion results in axonal degeneration of peripheral nerves

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39
Q

What kind of neuron damage is occuring in DM

A

Segmental demyelination with loss of small myelinated and unmyelinated fibers

*Also loss of autonomic fibers

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40
Q

Which thyroid dysfunction can result in neuropathy

A

Hypothyroidism

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41
Q

Which paraneoplastic syndromes can cause neuropathy

A

Small cell lung cancer

42
Q

Which neoplasms can cause neuropathy

A

B cell neoplasms (monoclonal gammopathies)

43
Q

What are the syndromes that B cell neoplasms can cause

A
  • Polyneuropathy
  • Orangomegaly
  • Endocrinopathy
  • Monoclonal gammopathy
  • skin changes
44
Q

Which nerve is affected in saturday night palsy

A

Radial nerve upper arm

45
Q

WHich nerve can be affected at the knee

A

Fibular nerve

46
Q

What is Morton neuroma

A
  • Metatarsalgia
  • Interdigital nerve @ intermetatarsal sites

*Perineural fibrosis is histological findings

47
Q

What is the most common inhereted peripheral neuropathy

A

Charcot-Marie-Tooth (CMT)

48
Q

What is the inheritance pattern and gene in CMT1

A

Autosomal dominant
-Chromosome 17, peripheral myelin protein (PMP22)

*Seen in the second decade of life

49
Q

What is the inheritance form of CMTX

A

X linked

50
Q

What is the inheritance pattern and gene present in CMT2

A

Autosomal dominant
Due to axonal injury

  • MDN2 gene, normal mitochondrial fusion
  • Seen in early childhood
51
Q

What is the mechanism of disease in the case of myasthenia gravis

A

There are antibodies that target the acetylcholine receptors

52
Q

What is the mechanism of disease in Lambert-Eaton

A

Antibodies block ACh release by inhibiting the presynaptic calcium channel

53
Q

In those patients with myasthenia gravis who do not have Abs to AChR, what are they to

A

Sarcolemmal protein muscle specific receptor tyrosine kinase

54
Q

What is the most common causes for Lambert-Eaton Myasthenic syndrome

A

Paraneoplastic conditions, with about 50 being from a small cell lung cancer

55
Q

What is the staining in the cause of myocytes undergoing regenerations

A

Basophilic staining, aka RED due to the height number of RNA

56
Q

When does dermatomyositis commonly occur

A

4th-6th decade

57
Q

What conditions has a distinctive lilac or helipotrope discoloration of upper eyelids and periprbital edema

A

Dermatomyositis

58
Q

Which lesions are commonly seen with dermatomyositis

A
  • Lilac with eyelids
  • telangiectasias of nail folds, eyelids, and gums
  • Groton lesions
59
Q

What are Groton lesions that are associated with dermatomyositis

A

Scaling erythematous eruptions or dusky patches over the knuckles, elbows, or knees

60
Q

Which muscles tend to be affected first with dermatomyositis

A

Proximal muscles (raising chair or climbing stairs)

61
Q

What conditions are those with dermatomyositis at an increased risk for

A
  • dysphagia (oropharyngeal and esophageal muscles)
  • Interstitial lung disease
  • Cardiac involvement

**Increased visceral cancer risk

62
Q

What are the autoantibodies that are commonly present in dermatomyositis

A

Anti-Mi2
Anti-Jo1
AntiP155/P140

63
Q

In those with dermatomyositis, which symptoms are expected in the presence of autoantibodies to:
-Anti-Mi2

A

Heliotrope rash and Groton papules

64
Q

In those with dermatomyositis, which symptoms are expected in the presence of autoantibodies to:
-anti-Jo1

A

Mechanic hands

65
Q

In those with dermatomyositis, which symptoms are expected in the presence of autoantibodies to:
-antiP155/P140

A

Paraneoplastic and juvenile cases

66
Q

What is the common histological findings in dermatomyositis

A

Perifascicular atrophy

*Atrophic fibers grouped at the periphery of fascicles

67
Q

In juvenile dermatomyositis, which organs are commonly affected

A
  • most common myopathy of children

- Involves the GI (mucosal ulcers, perforation)

68
Q

During polymyositis, which muscles are affected first

A

Symmetrical proximal muscle involvement

69
Q

What is the clinical features seen in a patient with polymyositis

A

Myalgia and weakness
Adult onset
No Cutaneous features

*Diagnosis of exclusion

70
Q

What are the histological findings in polymyositis

A

CD7 T cells in the endometrium, necrotic and regenerating fiber scattered through the fascicle

  • endomysial mononuclear infiltrate (differentiated that dermatomyositis)
  • *Random distribution of affected fibers
71
Q

What is the clinical features of inclusion body myositis

A

Slowly progression of muscle weakness, especially in the quadriceps and distal UE

*Starts with the distal muscle and extensors of knees and flexors of wrists and fingers (asymmetric)

72
Q

Rimmed vacuoles are seen in which condition

A

Aka inclusions with reddish granular rimming

Highlighted by Basophilic granules around the periphery, endpmysial fibrosis seen in inclusion body myositis

73
Q

What is the treatment for inflammatory myopathies

A

Usually responds poorly to steroids

74
Q

Chloroquine and hydroxychloriquine commonly affect which part of the body

A

*Used in the treatment of malaria

Causes lysosomal storage myopathy, leading to slowly progressing muscle weakness due to type 1 fiber disruptions

75
Q

Alcohol binge drinking can have what effect on muscles

A

Rhabdomyolysis

76
Q

What is the gene affected in DMD

A

Xp21, which codes of dystrophin

77
Q

What is the level of dystrophin in the case of DMD

A

Absent

78
Q

What is the level of dystrophin in the case of BMD

A

Decreased amount of DMD

79
Q

Which complication tends to arise in those with DMD or BMD

A

Cardiac manifestations

80
Q

What i sthe state of muscle size in those patients with DMD

A

Enlarged due to increased bulk that turns to fat and connective tissue

81
Q

What is myotonia seen during myotonic dystrophy

A

Sustained contraction of a group of muscle

*Can be elicited by percussion on the thenar eminence

82
Q

What is the genetic component seen during myotonic dystrophy

A

CTG trinucleaotide repeats leading to DMPK

83
Q

What are the symptoms in a patient with myotonic dystrophy

A
  • Stiffness, difficulty releasing grip
  • Skeletal muscle weakness
  • cataracts
  • Endocrinopathy
  • Cardiomyopathy
84
Q

Which condition can be described with:

  • Ring fiber
  • Sarciplasmic mass
  • Hatchet face
A

Myotonic dystrophy

85
Q

Patients with emery dreifuss muscular dystrophy (EMD) have mutation in which gene

A

EMD1 (x linked)
EMD2 (AD)

*Both code for nuclear lamina proteins

86
Q

What is the triad seen in those patients with emery dreifuss musclar dystrophy (EMD)

A

1) Slowly progressing hymeroperoneal weakness
2) Cardiomyopathy with conduction defects
3) Early contractures of the Achilles’ tendon, spine, and elbows

87
Q

What is the most common disease of lipid or gylcogen metabolism

A

Carnitin palmitolytransferase 2

88
Q

What are the symptoms seen in those with carnitine palmitolytransferase 2

A

Episodic muscle damage with exercise and fasting

89
Q

What are the lab values that will be seen in those with mitochondrial myopathies

A

Weakness, increased serum creatinine kinase, rhabdomyolysis

90
Q

What are the muscle commonly seen to be affected in those with mitochondrial myopathies

A

Extraocular muscle involvment

*Chronic regressive external ophthalmologist common

91
Q

What is the mutation in Levers

A

Point mutation in mitochondrial DNA leading to hereditary optic neuropathy

92
Q

What is the conditions being caused by Leigh syndrome

A

Subacute necrotizing encephalopathy

93
Q

What is the condition being caused during Barth syndrome

A

Infantile x linked cardio skeletal myopathy

94
Q

What is the condition being caused during Kearns-Sayre syndrome

A

Weakness of the extraocular muscles

Deletions or duplication of the mitochondrial DNA

*Also will ahve ophthalmoplegia, pigmentary degeneration of retina, complete heart block

95
Q

What does red, trichromatic stains showing “ragged” fibers mean

A

Aka aggreagated of abnormal mitochondria under the sarcolemma with distortion of myofibrils

**aka parking Lot inclusions

96
Q

What is the congenital cause of floppy infant due to

A

Spinal muscular atrophy

97
Q

What are some of the symptoms seen in spinal muscular atrophy

A 
Congenital:
-Myotonia
-Myopathy
-muscular dystrophies
Encephalopathy
98
Q

Muscular trophy destroys what component

A

Anterior horn cell of the SC

99
Q

What is the gene factor affected in spinal muscular atrophy

A

Survival motor neuron 1 (SMN1)

100
Q

What is the most common form of spinal muscular atrophy

A

Wernig Hoffman (SMA type 1)

  • onset at birth, floppy baby and death <3 yo
  • Truncal weakness and loss of chewing swallowing, and breathing
101
Q

Which gene and product is the result of malignant hyperthermia

A

RYR1 mutation, leading to events in the calcium channel

Robbins Pathology MSK (Chapters 24,25,26) (7 decks)

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