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

NCAM stain
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Vessel Pathology
Epineurial Veins: Damaged or Occluded

VvG stain
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Epineurial Artery: Occluded

H&E and Neurofilament stain
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Lymphocyte Inflammation

H&E stain
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Inflammation
Associated with: small epineurial vessel

H&E stain
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Epineurial Neovascularization

UEA I stain
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Epineurium
Multiple, Small vessels

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

MHC Class I stain
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Endoneurial Microvessels: Dilated

Toluidine blue stain
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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
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Behçet: Perineurial Pathology

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

VvG stain
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Fascicles with Non-uniform, Irregularly-stained Perineurium

C5b-9 stain
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Wallerian Degeneration

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

Acid Phosphatase stain
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Nerve Ischemia, Local: Varied involvement of Cells in Different Fascicles
Also see:
Rheumatoid Vasculitis

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

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

VvG stain
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Schwann Cell Populations
P0(r)sm.jpg)
NCAM (Green), P0 (Red)
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Most Denervated Schwann Cells have not converted to a Denervated Phenotype
Little co-staining of P0 & NCAM in Schwann cells
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1/9/2025