Neuromuscular

Behçet Syndrome: Neuropathy

Whole nerve views
Epineurium
Vessels
  Artery
  Endoneurial Microvessels
  Lymphocytic inflammation
  Neovasculariztion
  Vein
Axons
  Varied Axon Loss
  Wallerian degeneration
Fascicles
  Endoneurial Pallor
  Damaged Structure
  Infarction
  Perineurial Damage
  Schwann cells

History
41 year old female, 22 weeks pregnant, with onset of oral ulcers & motor sensory neuropathy during prior 8 weeks

Sural Nerve: Skip serial sections

Behçet Nerve Pathology
  Varied loss of Axons among fascicles
  Severely damaged fascicle with loss of axons & endoneurial cells (White Arrow)

Neurofilament stain

Behçet Nerve Pathology
  Perineurial Damage (Yellow Arrows)
  Lymphocytic inflammation around a small epineurial vessel (Black Arrow)
  Vein & Artery Damage (White Arrow)
  Endoneurial Pallor (Blue Arrow)

H&E stain

Behçet Nerve Pathology
  Varied loss of Axons among fascicles
  Severely damaged fascicle with loss of axons & endoneurial cells (White Arrow)
  Perineurial Damage (Yellow Arrows)

VvG stain

Behçet Nerve Pathology
  Varied loss of Axons among fascicles
  Severely damaged fascicle with loss of axons & endoneurial cells (White Arrow)
  Perineurial Damage (Yellow Arrows)

Gomori trichrome stain

Behçet Nerve Pathology
  Local Infarction: Varied loss of Non-myelinating Schwann cells among fascicles

NCAM stain

Vessel Pathology

Epineurial Veins: Damaged or Occluded

VvG stain

Epineurial Artery: Occluded

H&E and Neurofilament stain

Lymphocyte Inflammation


H&E stain
Inflammation
  Associated with: small epineurial vessel

H&E stain

Epineurial Neovascularization


UEA I stain
Epineurium
  Multiple, Small vessels

UEA I stain

Epineurium
  Multiple, Small vessels
  MCH-I upregulation by Epineurial connective tissue

MHC Class I stain

Endoneurial Microvessels: Dilated


Toluidine blue stain
Endoneurial Microvessels
  Size: Large
  Lumen: Large; Filled with RBCs
  Wall: Thin
Axons
  Loss of large & small Myelinated axons
  Remaining axons: Small
  Wallerian degeneration: Scattered ovoids

Toluidine blue stain

Behçet: Perineurial Pathology


VvG stain
Fascicles with Thick, Irregular Perineurium
  Axon loss: Intrafascicular variation

VvG stain

Fascicles with Non-uniform, Irregularly-stained Perineurium

C5b-9 stain

Wallerian Degeneration


VvG stain
Fascicles with Active Wallerian Degeneration
  Pale, Irregularly-stained Myelin (Above; Arrow)
  Acid phosphatase stains a few degenerating myelin sheaths (Below)

Acid Phosphatase stain

Nerve Ischemia, Local: Varied involvement of Cells in Different Fascicles

Also see: Rheumatoid Vasculitis

H&E stain
Fascicular involvement: Varied
  Left: Normal background staining of endoneurium
  Right: Endoneurial Pallor with mild subperineurial edema
    Wallerian Degeneration: Staining of myelin sheaths is lost
Vessels
  Occluded artery & Damaged veins


ATPase pH 4.3 stain
Fascicular involvement: Varied
  Left: Normal to dark background staining of endoneurium
  Right: Endoneurial Pallor
Epineurium
  Neovascularization: Many small, ATPase+ vessels


NCAM stain
Differential Fascicular involvement: Varied loss of non-myelinating Schwann cells
  Left: Diffuse distribution of non-myelinating Schwann cells in endoneurium
  Right: Reduced numbers of non-myelinating Schwann cells in endoneurium


VvG stain
Differential Fascicular involvement: Varied loss of Myelinated Axons
  Left: Mild loss of myelinated axons
  Right: Severe loss of myelinated axons
  Above: Intrafascicular variation in loss of myelinated axons


Neurofilament stain
Differential Fascicular involvement: Varied loss of Large & Small Axons (Above & Below)
  Left, Above: Mild loss of myelinated axons; Normal numbers of small axons
  Right, Above: Severe loss of all axons
  Below: Fascicles with intrafascicular variation in loss of axons

Neurofilament (Green) + NCAM (Red) stain

Damaged Fascicle
  Endoneurium: Collapsed & Lost
  Perineurium: Wavy & Irregular shape
  Surrounding Epineurium: Neovascularization
Compare to: Other fascicles in nerve

VvG stain

Schwann Cell Populations


NCAM (Green), P0 (Red)
Most Denervated Schwann Cells have not converted to a Denervated Phenotype
  Little co-staining of P0 & NCAM in Schwann cells


Neurofilament (Green), Myelin Basic Protein (MBP) (Red)
Immature Schwann cells on many remaining axons
  MBP stains on smaller axons with no myelin

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4/1/2024