Week 6 Overview of Neuromuscular Disorders Flashcards

1
Q

Define the components of the motor unit

A
  1. Anterior horn cell
  2. Peripheral nerve (axonal part)
  3. Peripheral nerve (myelin part)
  4. Neuromuscular junction (presynaptic & postsynaptic)
  5. Muscle
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2
Q

Know which components of the motor unit are affected in neurogenic, junctional and myopathic disorders

A
  • Neurogenic: anterior horn cell, peripheral nerve-axonal and myelin part
  • Neuromuscular junction disorders: Neuromuscular junction
  • Myopathic disorders: muscle
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3
Q

What do you look at to differentiate between neurogenic, junctional, and myopathic disorders? And to localize the problem.

A
  1. muscle weakness distribution
  2. presence of sensory function abnormality
  3. presence or absence of reflexes
  4. presence or absence of fatigability/diural variation
  5. mode of spread of weakness
  6. presence or absence of cramps or fasiculations
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4
Q

List the diagnostic laboratory tests and what type of disorders they are abnormal in.

A
  1. Serum CPK: elevated in myopathic disorders
  2. Nerve conduction studies: abnormal in neurogenic diseases
  3. Repetitive nerve stimulation studies: abnormal in neuromuscular junction disorders
  4. electromyographic evaluation
  5. muscle or nerve biopsy: to diagnose muscle or neurogenic disorders
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5
Q

What is the etiology and age of onset of Amyotrophic lateral sclerosis (ALS)?

A

This is a anterior horn cell disorder

  • etiology is unknown, sporadic.
  • age of onset: mid/late years of life
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6
Q

What are the clinical features of ALS?

A
  • purely motor with asymmetric, predominantly distal, proximal, or bulbar muscle weakness
  • sparing of extra ocular and sphincter muscles
  • cramps and fasciculations common
  • progression of disease: muscle atrophy and wasting, respiratory and swallowing impairment
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7
Q

What are the typical findings of diagnostic tests in ALS?

A
  • CPK normal to slightly increased
  • nerve conduction normal
  • EMG and muscle biopsy show denervation and reinnervation features
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8
Q

What is the etiology and of Guillain Barre Syndrome (GBS)?

A

This is a peripheral nerve disorder, demyelinating neuropathy
-etiology: immune mediated

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9
Q

What are the clinical features of GBS?

A

Classical form:

  • starts in lower extremities and moves up to involve upper extremities and some CNs
  • mild sensory complaints
  • predominant motor weakness and disability
  • respiratory muscle involvement common, rapid progression
  • autonomic symptoms secondary to autonomic nerve involvement
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10
Q

What are the typical findings of diagnostic tests in GBS?

A
  • abnormal nerve conduction studies

- cellular infiltrates indicative of inflammatory disorder in nerve biopsy

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11
Q

What is the etiology of myasthenia Gravis?

A

Autoimmune. Antibodies against nicotinic acetylcholine receptors.
Age of onset: various

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12
Q

What are the clinical features of myasthenia gravis?

A
  • symptoms begin in extra ocular and cranial nerve innervated muscles followed by proximal muscle weakness
  • fatigability worsened by activity
  • diurnal variations characteristic
  • ptosis, double vision, dysphagia, nasal voice, weakness of jaw closure, neck extensors with proximal muscle weakness, respiratory muscle involvement
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13
Q

What are the typical findings of diagnostic tests in myasthenia gravis?

A

Abnormal repetitive stimulation tests
elevated nicotinic Ach receptor antibody titer
abnormal thymic tissue

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14
Q

What is the etiology of Lambert-Eaton Myasthenia Syndrome (LEMS)? What is age of onset?

A
  • Autoimmune, paraneoplastic, secondary to small cell lung cancer
  • age of onset: mid-late years
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15
Q

What are the clinical features of LEMS?

A

-patients present with fatigue, proximal muscle weakness, and autonomic dysfunction (cholinergic hypo function)

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16
Q

What is the etiology of inflammatory myopathy?

A

Autoimmune. Common associated with various collagen vascular diseases. Can be manifestation of remote cancer.

17
Q

What are the clinical features of inflammatory myopathy?

A

Characteristically: neck flexors , proximal muscle weakness. Dysphagia, skin rash (dermatomyositis). Progressive if not treated.