Onion bulb formation
Onion bulb formation is seen in hypertrophic neuropathies such as Charcot-Marie-Tooth type 1A (CMT1A) and chronic inflammatory demyelinating polyneuropathy (CIDP). It is the result of proliferation of Schwann cells and deposition of collagen 1.
The nerve roots appear bulbous tapering as they extend along the nerve, with the following signal characteristics 2:
- T2: hyperintense in most cases
- T1 C+ (Gd): usually demonstrate enhancement
- 1. Oh SJ. Color Atlas of Nerve Biopsy Pathology. CRC Press. (2001) ISBN:1420039806. Read it at Google Books - Find it at Amazon
- 2. Duggins AJ, McLeod JG, Pollard JD et-al. Spinal root and plexus hypertrophy in chronic inflammatory demyelinating polyneuropathy. Brain. 1999;122 ( Pt 7) (7): 1383-90. doi:10.1093/brain/122.7.1383 - Pubmed citation