Regenerating Clusters
    Thin myelination
Pseudo-onion bulb
Muscle pathology
  Fiber type groups


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

  Regenerated axons: Usually thinly myelinated with short internodal length
  Thinly myelinated large axons may comprise
    Most myelinated axons in a nerve (Above) or
    Scattered axons (Below; arrows)
  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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