Figure 6. Onion-Bulb Formation on Electron Microscopy in Chronic Immune Sensory Polyradiculopathy (CISP)–Plus.

Electron micrographs taken from different nerves of patients with chronic immune sensory polyradiculopathy plus (CISP-plus) show evidence of chronic demyelination and abortive repair. The left column is at low magnification and the right column is at high magnification. (A, B) Dorsal lumbar rootlet biopsy shows frequent large onion-bulbs. (C, D) Fascicular sciatic nerve biopsy shows frequent but smaller onion-bulbs than were found in the dorsal roots. (E, F) Superficial radial nerve biopsy shows frequent regenerating nerve clusters. (G, H) Sural nerve biopsy shows rare small onion-bulbs. The chronic demyelinating changes occur at all levels but are most frequent and severe in proximal nerves (especially at the sensory root level).