In gratitude of the loyal support of our members, the CNS is offering complimentary 2021 Annual Meeting registration to all members! Learn more.

  • The Comprehensive Anatomy of the Foramen Ovale as it relates to Percutaneous Stereotactic Radiofrequency Rhizotomy: A Cadaveric Study of Dry Skulls

    Final Number:
    584

    Authors:
    Smruti K. Patel MD; Adel El-Nashar; Almaz Kurbanov; Kisenya Zervera; Ryan Hatch; Enoch Kan; Jeffrey T. Keller PhD; Andrew W. Grande MD

    Study Design:
    Laboratory Investigation

    Subject Category:
    Pain

    Meeting: 2018 ASSFN Biennial Meeting

    Introduction: Trigeminal neuralgia is a serious condition resulting in lancinating, episodic facial pain. Percutaneous stereotactic radiofrequency rhizotomy is frequently used to treat trigeminal neuralgia. A thorough understanding of the microsurgical anatomy of the foramen ovale and surrounding structures is required for efficient, effective and safe use of this technique. This study was undertaken to define the anatomical variations of the foramen ovale (FO) and to assess cannulation difficulty, as well as the potential risk of injury to surrounding structures.

    Methods: Bilateral foramina from 174 adult human dry skulls (348 foramina) were analyzed in both an anatomic and surgical orientation using photographs obtained from standardized projections. Measurements were obtained of multiple variables including shape, size, presence of adjacent structures, and the morphometric variability effect on cannulation.

    Results: From the anatomic exocranial view, 6 distinct anatomical shapes of the foramen ovale were identified as well as 5 anomalous variants. From the surgical view, 6 distinct procedural shapes were identified. When the surface area (SA) of the FO was measured in the surgical view, there was a significant loss of SA compared to the anatomic exocranial view. On average, the SA lost was 18.5 5.7%. Morphometrically, we found significant variability in foramen size, and obstruction of the foramen in up to 7.8% from a calcified pterygoalar ligament. Importantly, we found that 8% of foramina were very difficult to cannulate and the risk of inadvertent cannulation of the foramen lacerum was 12%.

    Conclusions: We determined that there is significant variability in the shape and size of the FO, which we believe impacts the ability to safely and effectively cannulate this structure. Preoperative imaging with a 3D head CT may be of value in predicting difficulty of cannulation and guide treatment decisions when considering the use of a percutaneous approach over microvascular decompression or radiosurgery.

    Patient Care: Our research helps improve patient care by highlighting the need to study pre-operative anatomy for each individual patient and consider neuronavigation in patients with variable skull base anatomy in order to prevent complications and improve efficacy of treatment when performing a percutaneous stereotactic radiofrequency or balloon rhizotomy.

    Learning Objectives: By the conclusion of this session, participants should be able to: 1) Recognize that there are variables sizes and shapes of the foramen ovale that must be recognized as not all patients may be good candidates for PSR based on variable anatomy and 2) Understand that there are multiple danger/high risk zones of injury during PSR or balloon rhizotomy and that anatomic variations of surrounding neurovascular structures are important to recognize when cannulating the foramen ovale to prevent complications

    References: 1. Chakravarthi K, Babu S. An anatomical study of the pterygo-alar bar and porus crotaphitico buccinatorius. Int J Health Sci. 2012;1:3-9. 2. Chouke KS, Hodes PJ. The ptergoalar bar and its recognition by roentgen methods in trigeminal neuralgia. Am J Roentgenol Radium Ther. Feb 1951;65(2):180-182. 3. Kanpolat Y, Savas A, Bekar A, Berk C. Percutaneous controlled radiofrequency trigeminal rhizotomy for the treatment of idiopathic trigeminal neuralgia: 25-year experience with 1,600 patients. Neurosurgery. Mar 2001;48(3):524-532; discussion 532-524. 4. Newton TH, Potts DG. Radiology of the skull and brain. Saint Louis,: Mosby; 1971. 5. Priman J, Etter LE. The pterygospinous and pterygoalar bars. Med Radiogr Photogr. 1959;35:2-6. 6. Ray B, Gupta N, Ghose S. Anatomic variations of foramen ovale. Kathmandu Univ Med J (KUMJ). Jan-Mar 2005;3(1):64-68. 7. Strojnik T, Smigoc T. Percutaneous trigeminal ganglion balloon compression rhizotomy: experience in 27 patients. The Scientific World Journal. 2012;2012(2012):1-5. 8. Tatli M, Sindou M. Anatomoradiological landmarks for accuracy of radiofrequency thermorhizotomy in the treatment of trigeminal neuralgia. Neurosurgery. Jul 2008;63(1 Suppl 1):ONS129-137; discussion ONS137-128. 9. Tew JM, Jr., Keller JT. The treatment of trigeminal neuralgia by percutaneous radiofrequency technique. Clin Neurosurg. 1977;24:557-578. 10. Tubbs RS, May WR, Jr., Apaydin N, et al. Ossification of ligaments near the foramen ovale: an anatomic study with potential clinical significance regarding transcutaneous approaches to the skull base. Neurosurgery. Dec 2009;65(6 Suppl):60-64; discussion 64.

We use cookies to improve the performance of our site, to analyze the traffic to our site, and to personalize your experience of the site. You can control cookies through your browser settings. Please find more information on the cookies used on our site. Privacy Policy