Neuromuscular

Age: Muscle & Nerve

Muscle
  Child
  Adult
  Aging
    Morphology
    Sarcopenia
Nerve
NMJs

From Bramwell: Atlas of Clinical Medicine

Children: Muscle Features

  • Muscle fibers
    • Size: Smaller than adult
    • Types
      • 1st year: More 2C fibers (Up to 3%)
      • General: Type 2 fibers 5% smaller than type 1
  • Nuclei
    • Larger
  • Capillaries
    • Lower #/Muscle fiber
    • 1st 3 years: Many fibers with no adjacent capillary

Adults: Muscle Features

  • Nuclei
    • Small
    • Round
  • Capillaries
    • All muscle fibers have adjacent capillary
 
NORMAL MUSCLE
Age
(Years)
Mean fiber
Diameter
(μM)
Birth 12 to 15
1 18
3 20
6 27
8 35
10 40
12 45
15 50
Adult 50 to 60

Aging (> 65 years): Muscle Changes 1

  • Type 2 muscle fibers
  • Mitochondrial
    • SDH+ muscle fibers: More frequent
    • COX- muscle fibers: More frequent
    • Complex I: Reduced activity 2
    • mtDNA: Reduced levels; More damage 3
  • Nuclei
    • Shape: More irregular
    • Size: Often increased
  • Strength correlations
    • Muscle mass: Correlates with
      • Bioavailable testosterone levels
      • Muscle fiber size
    • Type 2 muscle fiber size
    • NOT: Age per se
  • Iron content: Increased
  • Sarcopenia

Increased age (> 85 years): Common features in muscle

Nuclear shapes: Irregular

H&E stain

H&E stain
Muscle fiber size: Varied

Gomori trichrome stain

ATPase ph 4.3 stain
Type 2 fibers small

ATPase ph 4.6 stain
Fiber types: Non-random distribution

ATPase ph 9.4 stain

Acid phosphatase stain
Lipofuscin: Punctate sub-sarcolemmal regions

Esterase stain
Internal architecture
  Mildly irregular
  Pale (Type 2) fibers small

NADH stain

Age: Nerve changes


Age: Neuromuscular Junction Changes

NMJs: Rat

Age: 2 Months

Silver-Esterase stain

Age: 18 Months

Silver-Esterase stain

Age: 28 Months

Silver-Esterase stain

Return to Neuromuscular

References
1. J Am Geriatr Soc 2010;58:20692075
2. Muscle Nerve 2017;56:122-128
3. Cells 2019;8(12)

12/2/2019