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NMSP Exam 2 > Peripheral Nerve & Skeletal Muscle Part 2 > Flashcards

Peripheral Nerve & Skeletal Muscle Part 2 Flashcards

1
Q

What are some characteristics of traumatic neuromas?

A

Injury to nerve that regenerates slowly; axons continue to grow despite misalignment
- Small bundles of axons randomly oriented but surrounded by organized layers of Schwann cells, fibroblasts, and perineural cells

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2
Q

What are some kinds of compression or entrapment neuropathy?

A
  • Carpal tunnel syndrome: Median nerve; paresthesia of tip of thump and first 2 digits
  • Saturday night palse: Radial nerve when you fall asleep w upper arm raised
  • Ulnar nerve at elbow, peroneal nerve at knee
  • Morton neuroma
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3
Q

What is a main type of hereditary motor & sensory neuropathy?

A

Charcot-Marie-Tooth disease: Distal muscle atrophy, sensory loss, foot deformities

  • Muscle pain
  • Hand tremors
  • Cold hands & feet
  • Drop foot
  • Curled toes
  • High foot arches
  • Breathing difficulties
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4
Q

What are some characteristics of NMJ diseases in general?

A

Impairment of ACh release leading to painless weakness & fatigue
- Autoantibodies that inhibit key NMJ proteins are the most common cause

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5
Q

What is Myasthenia Gravis?

What associations do we see?

A

Immune mediated loss of ACh receptors
- Often have autoantibodies to AChR

Strong association b/w AChR autoAbs and thymic abnormalities (often thymus hyperplasia)

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6
Q

What are some sx of Myasthenia Gravis?

A

Fluctuating generalized weakness that worsens w exertion & over the course of the day
- Weakness begins w extraocular muscles, drooping eyelids, double vision

Note: Those w muscle specific tyrosine kinase exhibit more focal muscle involvement

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7
Q

What is tx for Myasthenia Gravis?

A
  • ACh-ase inhibitors (inc half-life of ACh)
  • Plasmapheresis & immunosuppressives
  • If thymoma, can get thymectomy
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8
Q

What is Lambert-Eaton Myasthenic Syndrome?

What are some sx and what is tx?

A

Antibodies block ACh release by inhibiting presynaptic calcium channel

  • Paraneoplastic process often d/t small cell carcinoma of the lung
  • Repetitive stimulation inc muscle response which is opposite of myasthenia gravis)

Tx: Drugs that inc ACh release

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9
Q

What are some characteristics of congenital myasthenic syndromes?

A

Present in the perinatal period w poor muscle tone, external eye weakness, breathing difficulties
- Others w milder form of disease may not come to clinical attention until adolescence or adulthood

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10
Q

D/Os caused by toxins

  • What does Botox do?
  • What is curare?
A
  • Botox- Clostridium botulinum blocks release of ACh

- Curare causes flaccid paralysis (muscle relaxant during certain surgeries)

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11
Q

What are 3 distinct morphologic changes seen in myopathic injuries

A

Segmental myofiber degeneration & regeneration

  • Creatinine kinase is released into blood (CK-MM)
  • Regenerating fibers are rich in RNA (basophilic staining)

Myofiber hypertrophy

Cytoplasmic inclusions

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12
Q

What are 3 inflammatory myopathies?

A
  • Dermatomyositis
  • Polymyositis
  • Inclusion body myositis
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13
Q

What is dermatomyositis?

What sx do we see? What antibodies do we see?

What pathologically causes this?

A
  • Damage to small blood vessels
  • Distinctive skin rash: Heliotrope discoloration of upper eyelids a/w periorbital edema
  • Telangiectasias in nail folds, eyelids, gums
  • Weakness and myalgias in proximal muscles
  • Dysphagia
  • Interstitial lung disease
  • Cardiac involvement

Autoantibodies: Anti-Mi2, anti-Jo1, anti-P155/P140

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14
Q

What does dermatomyositis inc the risk of?

What is the histo?

What do we see in the juvenile form?

A

Inc risk of visceral cancer; may be viewed as paraneoplastic

Histo: “Perifascicular atrophy”

Juvenile: Calcinosis & lipodystrophy

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15
Q

What do we see clinically and histologically in immune-mediated necrotizing myopathy?

What can inc the risk for it?

A

Sx: Subacute muscle weakness a/w significantly inc creatine kinase levels

Muscle bx will show necrosis & regeneration while inflammatory cell infiltrates are usually absent or minimal despite the autoimmune nature of the disease

Prior stain exposure can inc risk

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16
Q

What do we see in polymyositis?

What cell type is involved?

A

Adult onset, myalgia and weakness, no cutaneous features (ddx from dermatomyositis)
- Symmetrical proximal muscle involvement

CD8+ cytotoxic T-cells in the endomysium

17
Q

What is inclusion body myositis? Is it symmetric or asymmetric?

What do we see on histo?

A

Slowly progressive muscle weakness most severe in quadriceps & distal UE

  • Starts w distal muscles esp extensors of knees and flexors of wrist and fingers
  • Asymmetric
  • Dysphagia

Rimmed vacuoles seen on histo

18
Q

Tx for all inflammatory myopathies (dermatomyositis, polymyositis, inclusion body myositis)

A

Corticosteriods is first line

If steroid resistant, use immunosuppressives

Third line: IVIG. others

Note: Inclusion body myositis usually responds poorly to steroids or immunosuppressive tx

19
Q

What can toxic myopathies be caused by? (5)

A
  • Statins
  • Chloroquine and hydroxychloroquine
  • ICU myopathy esp cortocosteroids
  • Thyrotoxic myopathies
  • Alcohol
20
Q

Dysfxnal gene in malignant hyperthermia?

A

Ryanodine receptor-1 gene
- RYR1

19q13.2

21
Q

What are 2 X-linked muscular dystrophies? What gene are they caused by?

A

Both caused by lack of dystrophin, Xp21

Duchenne

  • More severe phenotype (NO dystrophin
  • Sx before 5yo, death between 25-30yo
  • Dystrophin expressed in heart and CNS

Becker
- Nearly normal lifespan but have cardiac disease (dec amount of dystrophin)

22
Q

What is pseudohypertrophy in DMD and what is muscle replaced by?

A

Enlargement of muscles of lower leg a/w weakness, inc bulk d/t inc muscle fibers initially but later in disease this is replaces by fat and connective tissue

23
Q

What is myotonic dystrophy?

A

Multisystem disorder; skeletal muscle weakness, cataracts, endocrinopathy, cardiomyopathy

  • Myotonia: Sustained involuntary contraction of muscles, can be elicited by percussion on thenar eminence
  • Stiffness and difficulty releasing grip

Gait disturbances then atrophy of facial muscles leading to ptosis, “hatchet face”

24
Q

What inheritance pattern is myotonic dystrophy passed on by? What do we see genetically?

What do we see on histo?

A

Autosomal dominant

CTG trinucleotide repeat

Myotonic dystrophy protein kinase (DMPK)

On histo can see “ring fiber”

25
Q

Important to note about emery-dreifuss muscular dystrophy?

A

OFTEN A DISTRACTOR ON EXAMS

Humeroperoneal weakness, cardiomyopathy, contractures of Achilles tendon, spine, elbows

26
Q

What are some diseases of lipid of glycogen metabolism?

A
  • Carnitine palitoyltranferase II deficiency
  • McArdle disease
  • Acid maltase deficiency (including Pompe disease)

Sx w exercise or fasting; slowly progressive

27
Q

What are some sx of mitochondrial myopathies and what are they d/t?

What can we see in histo?

A

Weakness, inc serum CK, rhabdomyolysis

  • Extraocular involvement commonly seen
  • Chronic progressive external ophthalmoplegia

Often see “ragged red fibers” on histo

Maternal inheritance

28
Q

What are 4 mitochondrial myopathies?

A
  • Leber optic neuropathy
  • Leigh syndrome (subacute necrotizing encephalopathy)
  • Barth syndrome (cardioskeletal)
  • Kearns-Sayre syndrom (extraocular muscles_
29
Q

What is spinal muscular atrophy?

What is the name of the most common disorder?

A

Generalized hypotonia (“floppy infant”)

Anterior horn cells are destroyed d/t SMN1 deficiency (survival motor neuron 1)

Large zones of atrophic myofibers mixed w scattered normal or hypertrophies myofibrils

Wernig-hoffman is most common: Weakness of truncal and extremity muscles w swallowing & breathing difficulties
- Onset <6mo w death at <3yo

30
Q

What are sx of ion channel myopathies?

What is a common genetic mutation and what disorder does this cause?

A
  • Epilepsy
  • Migraine
  • Movement DO w cerebellar dysfxn
  • Periph nerve disease
  • Muscle disease

RYR1 mutation leads to malignant hyperthermia
- Tachycardia, tachypnea, muscle spasms, hyperpyrexia

31
Q

What is tuberous sclerosis complex and what clinical signs do we see?

A
  • Harartomas
  • Renal angiomyolipomas
  • Pulmonary lymphangioleiomyomatosis
  • Cardiac rhabdomyomas
  • Cutaneous lesions like angiofibromas and subungal fibromas
32
Q

What is Von Hippel-Lindau disease and what clinical signs do we see?

A
  • Hemangioblastomas
  • Cysts of pancreas, liver, kidney
  • Renal cell carcinoma
  • Pheochromocytoma
  • Polycythemia
33
Q

What is neurofibromatosis type 1 and what clinical signs do we see?

A
  • Neurofibromas
  • Optic nerve gliomas
  • Lisch nodles (pigment spots in iris)
  • Cafe au lait spots
34
Q

What is neurofibromatosis type 2 and what clinical signs do we see?

A
  • Bilateral schwannomas (CNVIII)

- Multiple meningiomas and ependymomas of spinal cord

NMSP Exam 2 (6 decks)

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