Neuromuscular

CHRONIC PARTIAL DENERVATION OF MUSCLE

Internal nuclei
Necrotic & Clustered muscle fibers
Pseudomyopathic changes
Pyknotic nuclear clumps
Regenerating axon clusters
Split muscle fibers
Fiber type grouping

PSEUDOMYOPATHIC CHANGES


H&E stain

Gomori Trichrome stain
  • Endomysial connective tissue: Increased
  • Internal nuclei: One or several in muscle fibers
  • Pyknotic nuclear clumps
  • Grouped atrophy of muscle fibers
    • Groups are less well demarcated than in ongoing denervation
    • Increased endomysial connective tissue is especially prominent in these regions
  • Small muscle fibers may be rounded or angular
  • Hypertrophic muscle fibers: Common

SPLIT MUSCLE FIBERS

INTERNAL NUCLEI


H&E stain

NADH stain

H&E stain
  • "Split" muscle fibers probably result from partial fusion of regenerating fibers
  • These split muscle fibers are very large (hypertrophic)
  • Split muscle fibers often have internal nuclei

NECROTIC & CLUSTERED MUSCLE FIBERS


H&E stain
  • A hypertrophied muscle fiber may become necrotic (left)
  • Several different muscle fibers regenerate in its place and cluster within the old basal lamina

PYKNOTIC NUCLEAR CLUMPS

Also see
Pyknotic nuclear clumps: Morphology

H & E stain

H & E stain
 

H&E stain

Pyknotic nuclear clumps: High magnification

Congo red stain

Congo red stain

Pyknotic nuclear clumps: May also contain lipofuscin

H&E stain

Congo red stain

Pyknotic nuclear clumps: Grouped atrophy

H&E stain

H&E stain

Congo red stain

Pyknotic nuclear clumps: Stain dark with esterase & NADH

NADH stain

Esterase stain
Angular fibers: Esterase
Esterase stain

Pyknotic nuclear clumps: With lipofuscin

Acid phosphatase stain

Acid phosphatase stain

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12/22/2014