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NEUROLOGY > NMJ d/o > Flashcards

NMJ d/o Flashcards

1
Q

What are the skeletal fibres innervated by?

A

by motor neurones, whose cell bodies reside in the VENTRAL horn of the spinal cord

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2
Q

What is a motor end plate?

A

it is the synapse between the motor neurones and muscle

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3
Q

What occurs when the AP reaches the axon terminale?

A
  • AP moves along the nerve
  • voltage-gated Calcium channels open up, allowing the INFLUX of Calcium ions into the axone terminale
  • triggering the release of Ach in to the synaptic cleft from the vesicles
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4
Q

WHat occurs with the release of ACh into the synaptic cleft?

A

Acetylcholine binds to the Ach-receptor

  • opening up Na+/K+ channels
  • depolarization starts an AP at the motor end plate
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5
Q

What is the role of Acetylcholinesterase?

A
  • breaks down ACh into acetyl and choline

- choline will then be sequestered into vesicles in the pre-synaptic neurone

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6
Q

What is Curare?

A
  • aka T-tubocurarine
  • it blocks depolarization of the post-synaptic neurone by binding to the ACh-R and INHIBITING the binding of ACh
  • causes death by RESPIRATORY ARREST as no muscle contraction occurs
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7
Q

Name a pre-synaptic disorder.

A

Botulism

  • by Clostridium Botulinum (present in the SOIL)
  • seen in IV drug users (black tar heroin)
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8
Q

How does Cl.Botulinum bring about its action?

A
  • it cleaves the presynaptic proteins involved in Vesicle formation
  • blocking vesicle docking (preventing REUPTAKE of CHOLINE)
  • no more release of ACH > paralysis of the muscle fibre
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9
Q

How does Botulism present as?

A

-rapid weakness over 6 hrs (NO SENSORY loss)

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10
Q

What occurs in Lambert Eaton Myasthenic Syndrome (LEMS)?

A
  • Anti-bodies to presynaptic calcium channels leads to LESS vesicle release.
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11
Q

What is LEMS a/w?

A
  • underlying small cell lung carcinoma
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12
Q

How to rx LEMS?

A

3-4 diaminopyridine

Amifampridine

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13
Q

What is the most common D/O of the neuromusclular jxn? What brings about this condition?

A

-Myasthenia Gravis - an autoimmune condition with Antibodies to AChR
>reduces no. of FUNCTIONING receptors leading to FATIGUABILITY and WEAKNESS

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14
Q

What are the signs of M.G?

A
  • ptosis
  • rapid onset of respiratory d.o
  • lower back weakness
  • appears sad (B/L facial weakness)
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15
Q

When may the symptoms of Myasthenia Gravis begin to show?

A
  • when ACh receptors reduce to 30% of normal

- –reduced AChR may FLATTEN endplate folds

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16
Q

State the issues brought out by the ACh-Abs? (3)

A
  1. blocks Ach from binding to its receptors
  2. reduces the no. of FUNCTIONING Ach-R
  3. inflammatory cascade is brought on to the folds of the end plates; flattening it out
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17
Q

What specific gland is said to play a role in MG?

A
  • the thymus

- 75% have thyoma or Hyperplasia

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18
Q

When is the usual onset of Myasthenia Gravis in Males and Females?

A
  • M: 60s or 70s
  • F: 30s

F:M= 3:2

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19
Q

What is the pattern of weakness like in pts with MG?

A
  • FLUCTUATING

- worse at the END of the day

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20
Q

What is most common presentation of MG?

A
  • EXTRAocular weakness, facial and bulbar weakness

- PROXIMAL limb weakness

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21
Q

Why do MG pts lose weight?

A
  • as they get tired of chewing

- thus won’t be eating as much

22
Q

What is Myasthenic Crisis?

A
  • complication of MG
  • worsening of the condition results in respiratory failure
  • requiring mechanical intubation and ventilation
23
Q

What acute treatment is given for MG?

A
  • acetylcholine-esterase INHIBITOR (pyridostigmine)
  • IV Immunoglobulin
  • THYMECTOMY (even w.o abnormality)
24
Q

If symptomatic rx does

not work for MG…?

A
  • steroids (PREDNISOLONE or steroid sparing agents –AZATHIOPRINE/MYCOPLENOLATE
  • plasma exchange/immunoglobulin
25
Q

Why is prednisolone used for MG?

A

-leads to remission and marked improvement in 70% of patients with OCULAR and generalized weakness

26
Q

Why is azathioprine used for MG?

A
  • It’s an immunosuppressant, dampening the prodn of Abs by the immune system
27
Q

Primary causes of death by MG? (2)

A
  • respiratory failure (in the elderly)

- aspiration pneumonia

28
Q

What are the different types of muscle fibres? (3)

A

TYPE I- slow oxidative
TYPE IIa- fast oxidative (aerobic metabolism)
TYPE IIb- fast glycolytic

29
Q

Which muscle fibre type is easily fatigued?

A

type IIb

30
Q

What are fasciculations and what precipitates it?

A
  • visible, fast and spontaneous TWITCH

- seen in healthy muscleswith stress, caffeine, fatigue

31
Q

Why do fasciculations occurs?

A
  • when a denervated muscle becomes hyperexcitable

- occurs as a sign of motor neurone disease, not MUSCLE.

32
Q

Define myotonia.

A
  • the delayed relaxation/sustained contraction of the muscle
  • hard to stop one shaking their hands
33
Q

State 4 signs of muscle disease.

A
  1. muscle wasting
  2. hyporeflexia,
  3. muscle WEAKENING
  4. myalgia
34
Q

When may myotonia occur?

A
  • usually hereditary

- involves chloride channels

35
Q

Name 2 immun-mediated musclular d/os?

A

POLYMYOSITIS

DERMATOMYOSITIS

36
Q

How does polymyositis present as? (3)

A
  • symmetrical
  • progressive, PROXIMAL weakness
  • develops over weeks to months
37
Q

What is serum finding of Polymyositis?

A
  • raised CK

- responds to Steroid

38
Q

How is Dermatomyositis different?

A
  • clinically similar but a/w skin lesions
  • “heliotrope rash” on face (red rash on swollen eyelids)
  • —50% have underlying MALIGNANCY
39
Q

What is Inclusion Body Myositis?

A
  • degenerative muscle condition
  • progressive weakness in 6th decade of life
  • thumb is spared
  • relentless Muscle wasting
40
Q

What is the commonest muscular dystrophy? What genetic anomaly results in this?

A
  • MYOTONIC DYSTROPHY
  • —autosomal dominant ; trinucleotide repeat d.o
  • —> multisystem involvement
41
Q

How does myotonic dystrophy present as?

A
  • myotonia, weakness, ptosis, frontal balding, cardiac defects
42
Q

What are muscular dystrophies? (3)

A
  • INHERITED
  • NON-inflammatory (unlike myositis)
  • no central or peripheral nerve problem
43
Q

Name 2 muscular dystrophies.

A
  • Duchenne

- BECKER Muscular dystrophy

44
Q

Name 3 infective causes of muscular d.o..

A
  • coxsacchie
  • Trypanosomiasis Cistercercosis (pork)
  • borrelia
45
Q

What is rhabdomyolysis?

A
  • dissolution of muscle
  • damage to the skeletal muscle >leakage of large quantities of toxic intracellular contents in to plasma . occurs w/ CRUSH injuries, toxins, post convulsions, extreme exercise
46
Q

What is the triad of rhabdomyolysis?

A
  • myalgia, muscle weakness, myoglobinuria

- Acute renal failure (reduced urine and dark red urine) and DIC

47
Q

What are the first few signs of Myasthenia Gravis?

A
  • ocular conditions

diplopia and ptosis

48
Q

Name causes of NMJ disruption.

A
  1. Mysathenia Gravis- Abs to the Ach-R in POST-synaptic cleft
  2. LAMBERT-EATON $- Abs to the voltage-gated calcium channels
  3. ORGANOPHOSPHATE poisoning- inhibition to ACh-E
49
Q

Drugs that may cause symmetrical, often proximal muscular weakness.

A
  • illicit drugs (COCAINE, Heroine)
  • alcohol
  • corticosteroids
  • others: HMG-CoA Reductase, ziduvodine, colchicine, penicillinamine, anti-malarial drugs, contraceptives, diuretics
50
Q

What are some medical (and cosmetic) uses of botulinum toxin? -

A
  • muscle dystonia
  • dysphonia
  • SWEATING
  • muscle TWITCHING around the eyes
51
Q

What autoimmune conditions is Myasthenia Gravis a.w?

A
  • DM
  • thyroid d.o
  • pernicious anemia
  • rheumatoid
  • SLE

NEUROLOGY (36 decks)

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