Neuromuscular

PERINEURIUM

Description
Disorders
Normal

Perineurium: Disorders


Perineurium: Normal


Toluidine blue stain
Perineurium
  Structure: Lamellar
    Fewer fascicles in distal, smaller nerves
    Outer layers may merge with epineurial connective tissue
  Location: Surrounds all peripheral nerve fascicles
  Cells
    Basal lamina: Surrounds perineurial cells; Thicker than Schwann cell basal lamina
    Cytoplasm contents
      Filaments
      Pinocytic vesicles: More in outer perineurial layers
    Tight junctions: Link adjacent perineurial cells; More in inner perineurial layers
    Origin: May be endoneurial fibroblasts
  Molecular
    Stained by: C5b-9 antibodies
    Contains: Collagens I & III
  Function
    Part of Blood-Nerve barrier
    Regulates endoneurial melieu

Toluidine blue stain

Toluidine blue stain

VvG stain

Vessel within Perineurium

Toluidine blue stain

Perineurium: Thin


Perineurium: Thin & Narrow

Toluidine blue stain

Perineurium: Indistinct connective tissue layers

Toluidine blue stain

Perineurium: Narrow; Few fibrils

VvG stain

Perineurium: Wide & Thickened


Toluidine blue stain
Widened Perineurium: Increased numbers of connective tissue layers

Toluidine blue stain
Widened Perineurium: Perineurial cells often have multiple, small round, pinocytic vesicles

C5b-9 stain


Widened Perineurium: Less prominent on histochemical stains
Widened Perineurium: Little acid phosphatase stain in contrast to perineuritis


C5b-9 stain
Widened Perineurium: C5b-9 stain is dark & wide

Perineuritis

Anatomic Pattern: Variable involvement among fascicles
  Perineurial Damage: Several fascicles (Left)
  Wallerian degeneration with scattered endoneurial cells (Larger fascicle; Right)

Acid phosphatase stain

Perineurium: Structural Damage, Varied patterns


Gomori trichrome stain
Perineurium
  Widened around fascicle
  Some areas are pale

Gomori trichrome stain
Perineurium
  Widened around fascicle
  Some areas are more dense or dark-stained


H&E stain

H&E stain
Perineuritis
Perineurium (arrow):
  Rarified & Thickened
Inflammation: Epineurium



H&E stain
Another fascicle, Same nerve
Perineurium (arrow)
  Normal staining
  Moderately Thick
  No inflammation
Perineurium
  Widened around fascicle
  Some areas are light- or dark-stained
  Cellularity: Increased
Endoneurium
  Microvessels: Large; Darker stained
  Axons: Reduced numbers

H&E stain

VvG stain


H&E stain
Perineuritis: Perineurial pathology
  Connective tissue staining
    Increased (Above)
    Reduced (Below)

Gomori trichrome stain


Toluidine blue stain

Toluidine blue stain

Perineuritis: Perineurial structure is Abnormal

Layers: Widened or Condensed (Above)
Cellularity within layers is increased (Below)

Toluidine blue stain

Perineuritis: Inflammation


H&E stain

H&E stain
Perineuritis: Increased histiocytic cellularity in & near perineurium

Acid phosphatase stain

Acid phosphatase stain
Perineuritis: Histiocytic cells
  In perineurium & endoneurium
    Confluent red stained histiocytes, mainly in perineurium
    Endoneurial cells: May reflect Wallerian degeneration

Perineuritis: Cells around Endoneurial microvessels


Perineuritis: Abnormal epineurial & endoneurial vessels

Epineurial Vessels
  Artery, Large: Damaged structure; Interrupted internal fibril layer
  Smaller vessel (Botton right): Perivascular inflammatory cells

VvG stain

Endoneurial Microvessels
  Size: Moderately large
  Endothelial cells: Prominent

H&E stain

Perineurial Calcification


Perineurial Calcification: Dark-stained regions on Gomori trichrome

Gomori trichrome stain

H&E stain

Congo red stain
Calcification
  Irregular, lucent regions in perineurium
  Calcium granules may be free or within histiocytic cells

VvG stain
Calcium granules: Rounded; In perineurium

VvG stain

Perineurial Calcification: Ultrastructure

From: R Schmidt
Calcification
  Rounded or irregular bodies
  Layered (Targetoid): Some layers are osmiophilic
  Location: Between perineurial connective tissue layers

Toluidine blue stain

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12/23/2016