Regenerating Clusters
    Thin myelination
Pseudo-onion bulb
Muscle pathology
  Fiber type groups
  Regenerated motor axon
Also see
  Collateral Sprouting


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 Clusters
  Pairs of axons within Schwann cell bands (Above & Below)
    Also see: Pseudo-onion bulbs
  Empty Schwann cell (Büngner) bands (Below)

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
    May be distributed individually (Above), or in clusters (Below)
  Thinly myelinated large axons may comprise: Most myelinated axons in a nerve
  Regenerated axons
    Size: Small
    Distribution: Present in clusters
    Myelin (Below): Contains both P0 & MBP
      Differs from myelin around normal smaller myelinated axons which contains mainly P0

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

  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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