Muscle pathology and diseases are a high-yield topic for neurology examinations as many of these disorders have characteristic or pathognomonic findings that allow for easy test question making! For this topic, pathology slide interpretation will be a great skill to have! Luckily this chapter has dozens of high-quality images with which to practice.

Author: Brian Hanrahan MD

Chapter Multimedia Content

Table of Contents

Table of Contents

Acquired Myopathies

Idiopathic inflammatory myopathies

Polymyositis

  • A female-predominant disease seen in one’s adult years that presents with subacute symmetric proximal weakness and pain.
  • Can be associated with rheumatoid arthritis, HIV, or underlying malignancy.
  • Muscle biopsy shows endomysial and perivascular monocytic inflammation and necrosis with regeneration.

Dermatomyositis

  • A female-predominant disease which presents with subacute proximal weakness and pain.
  • Dermatologic manifestations include a heliotrope rash on eyelids and an erythematous rash of the face or neck.
  • Can be associated with connective tissue disease, malignancy, and interstitial lung disease.
  • Muscle biopsy shows perifascicular inflammation and atrophy with sparing of the central fascicle.
  • Anti-TIF1y positive patients have the highest rate of associated cancer.

Inclusion body myositis (IBM)

  • A male-predominant slowly progressive idiopathic inflammatory condition of patients over the age of 50.

  • Clinical features include asymmetric weakness of the finger flexors and the quadriceps muscles.

  • Muscle biopsy shows rimmed vacuoles, filamentous nuclear and cytoplasmic inclusions, and scant lymphoid infiltrates.

  • May be associated (70% sensitivity, 92% specificity) with autoantibodies to cytoplasmic 5′-nucleotidase 1A (cN1A; NT5C1A).

Immune-mediated necrotizing myopathy

  • Presents with proximal weakness and myalgia, and elevated CK.
  • Pathology with necrosis and dystrophic changes with fibrosis, but can also have capillary changes.
  • Patients often have concurrent connective tissue disease or malignancy.
  • Associated with some antibodies including Anti-SRP (signal recognition particle), or Anti-HMG-CoA reductase antibodies
    • Often associated with a history of statin use.
  • Responds to steroids, IVIG, and other immunosuppressants.
  • EMG findings:
    • Membrane irritability will lead to positive waves and fibrillations.
    • Low amplitude, decreased duration, polyphasic MUAPs with early recruitment.
      • Note that if symptoms are chronic, large, long MUAPs may be present!

Treatment

  • Polymyositis and dermatomyositis are responsive to immunosuppressive therapies (steroids, methotrexate, azathioprine, mycophenolate, etc.) while IBM is not.


 

Log in to View the Remaining 60-90% of Page Content!

 
 

New Subscriber? Use this form!

(Or, Click Here to learn about our institution/group pricing)
  • Full access to all site content, including responsive customer service, 600+ question bank, 35 text chapters, 50 EMG cases, 500+ diagnostic images, 100+ EEGs, and 700+ flashcards!
    Full access to all site content, including responsive customer service, 600+ question bank, 35 text chapters, 50 EMG cases, 500+ diagnostic images, 100+ EEGs, and 700+ flashcards!
    Full access to all site content, including responsive customer service, 600+ question bank, 35 text chapters, 50 EMG cases, 500+ diagnostic images, 100+ EEGs, and 700+ flashcards!
    You have selected a Group Membership. After a successful payment you will be able to invite up to %s additional members.
    Applying discount code. Please wait...
  • Credit / Debit Card Information

Table of Contents

Table of Contents