OBJECTIVE Percutaneous stereotactic radiofrequency rhizotomy (PSR) is often used to treat trigeminal neuralgia, a serious condition that results in lancinating, episodic facial pain. Thorough understanding of the microsurgical anatomy of the foramen ovale (FO) and its surrounding structures is required for efficient, effective, and safe use of this technique. This morphometric study compares anatomical and surgical orientations to identify the variations of the FO and assess cannulation difficulty. METHODS Bilateral foramina from 174 adult human dry skulls (348 foramina) were analyzed using anatomical and surgical orientations in photographs from standardized projections. Measurements were obtained for shape, size, adjacent structures, and morphometric variability effect on cannulation. The risk of potential injury to surrounding structures was also assessed. RESULTS The authors identified 6 distinctive shapes of the FO and 5 anomalous variants from the anatomical view, and 6 shapes from the surgical view. In measurements of surface area of this foramen obtained using the surgical view, loss (average 18.5% ± 5.7%) was significant compared with the anatomical view. Morphometrically, foramen size varied significantly and obstruction from a calcified pterygoalar ligament occurred in 7.8% of specimens. Importantly, 8% of foramina were difficult to cannulate, thus posing a 12% risk of inadvertent cannulation of the foramen lacerum. CONCLUSIONS Significant variability in the FO’s shape and size probably affected its safe and effective cannulation. Preoperative imaging by 3D head CT may be helpful in predicting ease of cannulation and in guiding treatment decisions, such as a percutaneous approach over microvascular decompression or radiosurgery.
Bibliographical noteFunding Information:
We sincerely thank the Anatomy Bequest program for the skulls examined from the collection of the Department of Anatomy, University of Minnesota (UM), Minneapolis, MN; and UM students Kisenya Zervera, Ryan Hatch, and Enoch Kan for their work in the laboratory experiments and skull measurements. We acknowledge Mary Kemper and Tonya Hines from Glia Media Medical Communications for their assistance with medical editing and illustrations.
© AANS 2020, except where prohibited by US copyright law.
- Foramen ovale
- Percutaneous stereotactic radiofrequency rhizotomy
- Pterygoalar bar
- Pterygospinous ligament
- Trigeminal nerve
- Trigeminal neuralgia
PubMed: MeSH publication types
- Journal Article