Onion bulb structures, toluidine blue stain.
Hypertrophic changes with onion-bulb formation occur most commonly as a result of recurrent segmental demyelination and are most often seen in hereditary neuropathies (such as the fairly common Charcot-Marie-Tooth disease). The schwann cell doesn&amp;#8217;t wrap around the axon properly and as a result, you get these strange involutions in the histological section.