Mechanism of trigeminal neuralgia: an ultrastructural analysis of trigeminal root specimens obtained during microvascular decompression surgery.
OBJECTIVE
Recent progress in the understanding of abnormal electrical behavior in injured sensory neurons motivated an examination, at the ultrastructural level, of trigeminal roots of patients with trigeminal neuralgia (TN).


METHODS
In 12 patients biopsy specimens of trigeminal root were obtained during surgery for microvascular decompression. Pathological changes in tissue included axonopathy and axonal loss, demyelination, a range of less severe myelin abnormalities (dysmyelination), residual myelin debris, and the presence of excess collagen, including condensed collagen masses in two cases. Within zones of demyelination, groups of axons were often closely apposed without an intervening glial process. Pathological characteristics of nerve fibers were clearly graded with the degrees of root compression noted at operation. Pain also occurred, however, in some patients who did not appear to have a severe compressive injury.


CONCLUSIONS
Findings were consistent with the ignition hypothesis of TN. This model can be used to explain the major positive and negative symptoms of TN by axonopathy-induced changes in the electrical excitability of afferent axons in the trigeminal root and of neuronal somata in the trigeminal ganglion. The key pathophysiological changes include ectopic impulse discharge, spontaneous and triggered afterdischarge, and crossexcitation among neighboring afferents.
Devor
Marshall
M
Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Israel. marshlu@vms.huji.ac.il
Govrin-Lippmann
Ruth
R
Rappaport
Z Harry
ZH
D000328:Adult; D000368:Aged; D001369:Axons / Q000473:pathology; D001706:Biopsy; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000473:pathology; D008854:Microscopy, Electron; D008866:Microsurgery; D008875:Middle Aged; D009186:Myelin Sheath / Q000473:pathology; D009408:Nerve Compression Syndromes / Q000473:pathology / Q000601:surgery; D009410:Nerve Degeneration / Q000473:pathology; D013126:Spinal Nerve Roots / Q000473:pathology* / Q000601:surgery; D014276:Trigeminal Nerve / Q000473:pathology* / Q000601:surgery; D014277:Trigeminal Neuralgia / Q000473:pathology* / Q000601:surgery