Neuromuscular

Acute Immune Neuropathies

AIDP
AMN
AMSAN
Demyelination
  Active
  Macrophage-mediated

Acute Immune Demyelinating Polyneuropathy (AIDP)


H&E stain
Endoneurium: Granular myelin remnants
Perineurium, Epineurium & Vessels: Normal

H&E stain


Gomori trichrome stain
Myelin remnants: More staining with VvG than Gomori trichrome

VvG stain

Large & Small Axons
  Relatively preserved compared to myelin loss
  Focal loss in some endoneurial areas

Neurofilament stain


Acid phosphatase stain
Histiocytic cells: Associated with myelin remnants

Acid phosphatase stain

CD163 stain

Stages of Macrophage (Histiocyte)-mediated Myelin Stripping (Active Demyelination) 1,2


Macrophage
  Adherent to Schwann cell basal lamina
  Outside myelin sheath

Macrophage mediated demyelination: Macrophage process
  Macrophage is inside Schwann cell basal lamina
  Macrophage process extends under outer myelin layer (Arrows)
  Also see; Active demyelination
Macrophage mediated demyelination: Macrophage process
  Histiocyte processes: Extend between layers of myelin (Arrows)

Electron micrograph: From Robert Schmidt MD

Demyelination: Schwann cells containing Myelin & Lipid debris

Myelin debris: Multiple partially degraded myelin fragments in phagocytic cells


Toluidine blue stain
Lipid debris & droplets
  Multiple round regions in phagocytic Schwann cells
  Phagocytic Schwann cell: Basal lamina surrounds cell

Demyelinated Axons: Surrounded by cell processes


Electron micrographs: From Robert Schmidt MD
Demyelinated axons (Arrows)
Axons, without myelin, surrounded by phagocytic cells (Histiocytes)
Axon cytoplasm is dark, containing closely spaced neurofilaments.
Phagocytic cells contain myelin debris, lipid droplets & inclusions.

Demyelinated axons
  Patially surrounded by Schwann cell basal lamina (Above, Arrow)
  May be near cells containing myelin debris

Demyelinated axons
Demyelinated axon
  Surrounded, in part, by Schwann cell basal lamina and some Schwann cell processes
  A macrophage (Top; Right) is located outside the basal lamina

Subperineurial edema


Toluidine blue stain
Subperineurial edema: Separation between endoneurium & perineurium
Endoneurial vessels & Endothelial cells: Large

Toluidine blue stain


Toluidine blue stain
Differential fascicular involvement: More loss of myelin in some fascicles than others

Toluidine blue stain

Acute Motor > Sensory Axonal Neuropathy with serum IgG binding to GalNAc-GD1a ganglioside

Sensory nerve: Axons relatively preserved


Toluidine blue stain
Subperineurial edema

Toluidine blue stain


Gomori trichrome stain
Differential fascicular involvement: More loss of myelinated axons in some fascicles than others

VvG stain

Few phagocytic cells

Acid phosphatase stain

Large & Small axons: Preserved numbers

Neurofilament stain

C5b-9 stain: Reduced on perineurium
Patient
Control


VvG stain
Polyglucosan bodies: Located in axons in intramuscular nerve

PAS stain

Acute Motor-Sensory Axonal Neuropathy (AMSAN)

From: Chunyu Cai, Dallas

Gomori trichrome stain
Differential fascicular involvement: More loss of myelinated axons in some fascicles than others


H& E stain
Subperineurial edema


H& E stain
Wallerian Degeneration: Myelin ovoids

Trichrome stain

Wallerian Degeneration: Phagocytic cells associated with myelin debris

Myelin ovoids

Loss of myelinated axons

Myelinated axons: Reduced numbers

Macrophages (Arrow)
  Marginated in vessel
  Extravasated in endoneurium

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9/26/2022