Neuromuscular

PERIPHERAL NERVE REGENERATION

Axons
  Regeneration
  Post-regeneration
    Regenerating Clusters
    Thin myelination
Pseudo-onion bulb
Muscle pathology
  Fiber type groups

REGENERATING CLUSTERS


Toluidine blue stain
Regenerating Axon Clusters (Arrow)
  Clusters of 2 to 12 axons
  Myelin thickness
    Thin for axon size
    Similar for all axons in cluster
  There is also axon loss
    Reduced numbers of large & small myelinated axons
    Büngner bands
  Clusters of regenerating axons often occur with chronic changes in muscle
    Partial denervation
    Fiber type grouping

Regenerating Clusters

Regenerating Cluster: Late
  All axons in cluster (Arrow) have nearly normal myelin sheath thickness


Toluidine blue stain

Ultrastructure: From Robert E Schmidt MD



Toluidine blue stain
Regenerating Clusters
  Thinly myelinated large axons have similar degrees of myelination


POST-REGENERATION
  Regenerated axons
    Usually thinly myelinated with short internodal length
    May be distributed individually (Above), or in clusters (Below)
  Thinly myelinated large axons may comprise: Most myelinated axons in a nerve
POST-REGENERATION
  Regenerated axons
    Size: Small
    Distribution: Present in clusters
    Myelin (Below): Contains both P0 & MBP
      Differs from myelin normal small myelinated axons which contains mainly P0

P0 green; Myelin Basic Protein (MBP) (Red); Both Yellow

POST-REGENERATION
  Regenerated axons: Scattered (Below; Arrows) among larger axons
  Myelinated axons: Reduced numbers

Toluidine blue stain: From Chunyu Cai
Thinly myelinated large axons: Scattered or Clustered

Toluidine blue stains of plastic nerve sections


POST-REGENERATION: Few thickly myelinated large axons

VvG stain

POST-REGENERATION: Reduced numbers of large axons

Neurofilament stain

POST-REGENERATION: Proliferation of non-myelinating Schwann cells

NCAM stain

Onion Bulb-like structures (Dark Arrow) & Redundant Schwann cell processes (White arrow) around thinly myelinated axons

Pseudo Onion bulb
Thinly myelinated large axon: Surrounded by a pseudo onion bulb (Multiple Schwann cell processes)

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10/9/2018