Role of the petrous ridge and angulation of the trigeminal nerve in the pathogenesis of trigeminal neuralgia, with implications for microvascular decompression
Vascular compression is the main pathogenetic factor in apparently primary trigeminal neuralgia; however some patients may present with clinically classical neuralgia but no vascular conflict on MRI or even at surgery. Several factors have been cited as alternative or supplementary factors that may cause neuralgia. This work focuses on the shape of the petrous ridge at the point of exit from the cavum trigeminus as well as the angulation of the nerve at this point.
Patients with trigeminal neuralgia that had performed a complete imagery workup according to our protocol and had microvascular decompression were included as well as ten controls. In all subjects, the angle of the petrous ridge as well as the angle of the nerve on passing over the ridge were measured. These were compared from between the neuralgic and the non-neuralgic side and with the measures performed in controls.
In 42 patients, the bony angle of the petrous ridge was measured to be 86° on the neuralgic side, significantly more acute than that of controls (98°, p = 0.004) and with a trend to be more acute than the non-neuralgic side (90°, p = 0.06). The angle of the nerve on the side of the neuralgia was measured to be on average 141°, not significantly different either from the other side (144°, p = 0.2) or from controls (142°, p = 0.4). However, when taking into account the grade of the conflict, the angle was significantly more acute in patients with grade II/III conflict than on the contralateral side, especially when the superior cerebellar artery was the conflicting vessel.
This pilot study analyzes factors other than NVC that may contribute to the pathogenesis of the neuralgia. It appears that aggressive bony edges may contribute—at least indirectly—to the neuralgia. This should be considered for surgical indication and conduct of surgery when patients undergo MVD.
KeywordsTrigeminal neuralgia Trigeminal nerve Microvascular decompression surgery Pathophysiology Neuroimaging
Andrei Brinzeu: substantial contributions to the conception and design, and acquisition of data, and analysis and interpretation of data; statistical analysis; drafting the article or revising it critically for important intellectual content; and final approval of the version to be published. Chloé Dumot: substantial contributions to the acquisition of data and analysis of data, proofing the article, and approval of the final version to be published. Marc Sindou: substantial contributions to the conception and design and interpretation of data, drafting the article, and revising it critically for important intellectual content; revising the article; and approval of the final version to be published.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in this study were in accordance with the ethical standards of the institutional research committee (Comithee d’ethique de l’etablissement, Hopital Neurologique de Lyon) and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
This was an imagery study performed with clinical data collected from patient files collected prospectively. For this type of study, formal consent is not required. All patients, however, gave informed consent for the procedure and the study.
- 9.Leal PRL, Hermier M, Froment JC, Souza MA, Cristino-Filho G, Sindou M (2010a) Preoperative demonstration of the neurovascular compression characteristics with special emphasis on the degree of compression, using high-resolution magnetic resonance imaging: a prospective study, with comparison to surgical findings, in 100 consecutive patients who underwent microvascular decompression for trigeminal neuralgia. Acta Neurochir 152:817–825CrossRefPubMedGoogle Scholar
- 11.Leal PRL, Hermier M, Souza MA, Cristino-Filho G, Froment JC, Sindou M (2011) Visualization of vascular compression of the trigeminal nerve with high-resolution 3T MRI: a prospective study comparing preoperative imaging analysis to surgical findings in 40 consecutive patients who underwent microvascular decompression for trigeminal neuralgia. Neurosurgery 69:15–25 discussion 26CrossRefPubMedGoogle Scholar
- 18.Sindou M, Howeidy T, Acevedo G (2002) Anatomical observations during microvascular decompression for idiopathic trigeminal neuralgia (with correlations between topography of pain and site of the neurovascular conflict). Prospective study in a series of 579 patients. Acta Neurochir 144:1–12 discussion 12-13CrossRefPubMedGoogle Scholar
- 19.Sindou M, Leston J, Howeidy T, Decullier E, Chapuis F (2006) Micro-vascular decompression for primary Trigeminal Neuralgia (typical or atypical). Long-term effectiveness on pain; prospective study with survival analysis in a consecutive series of 362 patients. Acta Neurochir 148:1235–1245 discussion 1245CrossRefPubMedGoogle Scholar
- 20.Sindou M, Leston J, Decullier E, Chapuis F (2007) Microvascular decompression for primary trigeminal neuralgia: long-term effectiveness and prognostic factors in a series of 362 consecutive patients with clear-cut neurovascular conflicts who underwent pure decompression. J Neurosurg 107:1144–1153CrossRefPubMedGoogle Scholar