In each part of this question, list clinical examination findings for each of the two underlined conditions that would help you to distinguish between them:

  • A myopathy or a neuropathy as being the cause of weakness in all limbs of a patient

[Click here to toggle visibility of the answers]

College Answer

Myopathy

  • Wasting is late sign
  • Usually proximal weakness
  • Reflexes preserved until late
  • Normal sensory exam
  • May be muscle tenderness

Neuropathy

  • Wasting earlier
  • May be fasciculations
  • Often peripheral distribution
  • Loss of reflexes
  • May be abnormal sensory exam

Discussion

This comes down to basic common sense.

If the nerves are healthy, and the muscles are to blame,

  • The sensory supply should be preserved
  • The reflexes should be preserved
  • Weakness should be proximal - that is where the bigger muscles are, and the weakness there will be more obvious.
  • There should be no fasciculations

Also...

  • There may be myocardial involvement (skeletal myopathies tend to be associated with cadiomyopathy)
  • The muscles involved may be painful and tender(as in myositis)

This question has been repeated. Its doppelganger, Question 3.1 from the first paper of 2010, has a much better-organised college answer.

References

References

Chapter   57   (pp. 617)  Neuromuscular  diseases  in  intensive  care by George  Skowronski  and  Manoj  K  Saxena

UpToDate: An approach to the patient with muscle weakness

Young, G. Bryan, and Robert R. Hammond. "A stronger approach to weakness in the intensive care unit." Critical care 8.6 (2004): 416.

Dhand, Upinder K. "Clinical approach to the weak patient in the intensive care unit." Respiratory care 51.9 (2006): 1024-1041.