Five patients with chronic neuropathies of unknown etiology had increased numbers of Schwann cells in their sural nerves; the processes of these Schwann cells, oriented around axons, formed onion bulbs. The myelin content of the affected nerves, assessed by histologic methods and by measurement of the yield of myelin sulfatide, was markedly reduced. The nerves incorporated sulfatide labeled with radioactive sulfur (35S) into myelin during in vitro incubation with sodium sulfate S 35, and the specific activity of myelin sulfatide was higher than in nerves obtained from normal and disease controls. It is likely that there is heterogeneity of Schwann cell function within onion bulbs, with some Schwann cells not participating in myelin repair and others regenerating myelin briskly.
Pleasure DE, Towfighi J. Onion Bulb Neuropathies. Arch Neurol. 1972;26(4):289–301. doi:10.1001/archneur.1972.00490100019001
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