Acta Neuropathologica

, Volume 114, Issue 2, pp 187–194 | Cite as

Novel fibroblastic onion bulbs in a demyelinating avian peripheral neuropathy produced by riboflavin deficiency

  • Z. Cai
  • P. C. BlumbergsEmail author
  • J. W. Finnie
  • J. Manavis
  • P. D. Thompson
Original Paper


The finding of novel fibroblastic onion bulb-like structures in peripheral nerves is reported for the first time in avian riboflavin deficiency. Day old broiler meat chickens were fed a riboflavin deficient diet (1.8 mg/kg) and were killed on postnatal days 6, 11, 16, 21 and 31, whereas control chickens were fed a conventional diet containing 5.0 mg/kg riboflavin. The fibroblastic onion bulb-like structures were found in sciatic and brachial nerves from day 11 onwards and consisted of long cytoplasmic processes of hypertrophied fibroblasts surrounding demyelinated, remyelinated and normally myelinated axons. The fibroblast cytoplasmic processes often enveloped more than one nerve fibre to produce a unique compound-like onion bulb structure. These onion bulb-like structures occurred early in the course of segmental demyelination at the same time as tomacula formation and became increasingly more prominent in the later stages of demyelination and remyelination. The molecular basis of formation of these unique structures requires further study as to the basis of the attraction of the fibroblast processes to nerve fibres associated with myelinating Schwann cells. The model may also be useful in investigating the role of endoneurial fibroblasts in endoneurial fibrosis as the early fibroblastic response in the onion bulbs is distinct from the more usual fibroblastic deposition of collagen in end-stage peripheral nerve disease.


Avian riboflavin deficiency Peripheral nerves Demyelination Fibroblastic onion bulbs 



We thank Inghams Enterprises, Adelaide, for the support of this study.


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Z. Cai
    • 1
    • 2
  • P. C. Blumbergs
    • 1
    • 2
    • 3
    Email author
  • J. W. Finnie
    • 1
  • J. Manavis
    • 1
  • P. D. Thompson
    • 2
  1. 1.Hanson Institute Centre for Neurological Diseases Institute of Medical and Veterinary ScienceAdelaideAustralia
  2. 2.Department of Neurology and University Department of MedicineRoyal Adelaide HospitalAdelaideAustralia
  3. 3.Department of PathologyThe University of AdelaideAdelaideAustralia

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