Variational Anatomy, Morphometric and Topographic-Anatomical Characteristics of the Intracranial Part of the Trigeminal Nerve

The aim of the study was to develop a technique for examining the intracranial part of the tri- geminal nerve using sectional material, to study the variational anatomy of its roots, morphometric characteris- tics and topographic-anatomical relationships of the nerve trunk with blood vessels, and the possibility of in vivo visualization using magnetic resonance imaging.

Material and methods. The study of the anatomical and topographic relationships between the trigeminal nerve trunk and blood vessels was conducted on 30 non- embalmed human cadavers (13 males and 17 females) of the second period of adulthood and elderly age (60–70 years). For this purpose, an original technique for opening the cranial vault was proposed. This approach allows for unilateral removal of the tentorium cerebelli, opening of the cerebellopontine cistern, preservation of the integrity of anatomical structures, and provides the opportunity to study their relationships in detail. The study of variational anatomy was carried out on 72 specimens (31 male, 41 female) of the brain obtained from individu- als of the second period of adulthood and elderly age.

Results. Three variants of the exit of the roots forming the trigeminal nerve trunk were demonstrated: in 63% of cases, separate emergence of two roots (sensory and mo- tor) was observed; in 32%, formation of a single root; and in 5%, two motor roots. Morphometric characteristics of the intracranial part of the trigeminal nerve were obtained (length and width of the trigeminal nerve trunk, anteroposterior and lateromedial dimensions of the trigeminal ganglion, length and width of the main branches of the trigeminal nerve (ophthalmic, maxillary, and mandibular nerves) before their entry into the foramina of the skull base. The topographic-anatomical relationships of the trigeminal nerve with the superior cerebellar artery and the superior petrosal vein were described.

Conclusion. An original dissection technique was devel- oped, allowing the study of the intracranial part of the trigeminal nerve while preserving the integrity of all ana- tomical structures. The conducted study clarified possible predisposing factors for the development of neurovas- cular conflict involving the trigeminal nerve trunk with the superior cerebellar artery and the superior petrosal vein. Three variants of the emergence of the trigeminal nerve roots were identified, with separate emergence of the sensory and motor roots being predominant. Using MRI, the possibilities of in vivo visualization of the tri- geminal nerve trunk and ganglion, as well as the study of their morphometric and topographic-anatomical rela- tionships, were demonstrated.

1. Tkach AV, Kutia SA, Tkach VV, Moroz GA. Modern ideas on trigeminal ganglion. Zhurnal nevrologii i psikhiatrii im SS Korsakova. 2022;122(12):143. (In Russ.). doi: 10.17116/jnevro2022122121143.

2. Ustyuzhantsev NE. [Topograficheskaya anatomiya koreshka troinichnogo nerva v bokovoi tsisterne mosta] Topographic anatomy of the trigeminal nerve root in the lateral cistern of the pons varolii Kazan Medical Journal. 2010;91(2):187–192. (In Russ.).

3. Eshraghi Y, Vitug SJ, Guirguis M. Interventional Treatment Options for Trigeminal Neuralgia. IntechOpen eBooks. 2019 Nov 13 [cited 2026 Mar 17]; Available from: https://www.intechopen.com/chapters/69871. doi: 10.5772/intechopen.89091

4. Gordon J, Piper K, George Z, Vakharia K, Bezchlibnyk YB, Harry Van Loveren. Anatomic Variations of Foramen Ovale as a Predictor of Successful Cannulation in Percutaneous Trigeminal Rhizotomies. Operative Neurosurgery. 2024; 26(3): 279–285. doi: 10.1227/ons.0000000000000975

5. Joo W, Yoshioka F, Funaki T, Mizokami K, Rhoton AL. Microsurgical anatomy of the trigeminal nerve. Clinical Anatomy. 2013; 27(1):61–88. doi: 10.1002/ca.22330

6. La Rocca G, Mazzucchi E, Pignotti F, Galieri G, Rinaldi P, Sabatino G. Advanced Dissection Lab for Neuroanatomy Training. Frontiers in Neuroanatomy. 2022; 15. doi: 10.3389/fnana.2021.778122.

7. Matsushima T, Rhoton AL, de Oliveira E, Peace D. Microsurgical anatomy of the veins of the posterior fossa. Journal of Neurosurgery. 1983; 59: 63– 105.

8. Murat Ulutaş, Suat Boyacı, Akın Akakın, Türker Kılıç, Aksoy K. Surgical anatomy of the cavernous sinus, superior orbital fissure, and orbital apex via a lateral orbitotomy approach: a cadaveric anatomical study. Acta Neurochirurgica. 2016; 158(11):2135–48. doi: 10.1007/s00701-016-2940-z

9. Ramesh VG, Ganapathy Premkumar. An anatomical study of the neurovascular relationships at the trigeminal root entry zone. Journal of Clinical Neuroscience. 2009; 16(7):934–6. doi: 10.1016/j.jocn.2008.09.011.

10. Rhoton AL. The Posterior Fossa Veins. Neurosurgery. 2000; 47(suppl_3): 69–92. doi: 10.1097/00006123-200009001-00012

11. Toda H, Goto M, Iwasaki K. Patterns and variations in microvascular decompression for trigeminal neuralgia. Neurologia Medico-Chirurgica. 2015; 55(5):432–41. doi: 10.2176/nmc.ra.2014-0393

12. Xiao Q, Peng H, Tang G, Yuan J, Peng G, Zhang C, et al. Individual surgical management of trigeminal schwannomas guided by an extended classification: a consecutive series of 96 clinical cases at a single institution. Neurosurgical Review. 2025; 48(1). doi: 10.1007/s10143-025-03404-5