Foramen Vesalius - constant or variable foramen

Introduction/Objective. The foramen of Vesalius (FV) is a variable foramen located at the base of the skull, anteromedial to the foramen ovale, and lateral to the foramen rotundum. Through this foramen, passes one of the emissary veins, which establishes communication between the cavernous sinus and the pterygoid plexus. The aim of the study was to determine the incidence of this foramen in adults depending on gender, along with the number of foramina, distributions relative to the side of the skull and diameter of the foramen. Methods. A material used in the study were digital CT scans of adult paranasal cavities from the archives of the Radiology Center, archived in the PACS software system. We analyzed axial CT sections of 1 mm thickness. The research included 500 subjects (250 males and 250 females). Results. The foramen of Vesalius was present in 67.6% of respondents. In 50.9% cases, the foramen was bilateral and in 49.1% it was unilateral. The average oblique diameter of the foramen in men was 1.75 ? 0.59 mm and in women 1.56 ? 0.48 mm. In 22 subjects (6.51%) the foramina were doubled, and 2 (0.60%) were tripled. Conclusion. There was no statistically significant difference in the incidence of the foramen of Vesalius concerning gender. The mean diameter of the foramen was statistically higher in males. The presence of this foramen is important for neurosurgeons because, during the percutaneous trigeminal rhizotomy, the needle can pass through this foramen, injure the surrounding blood vessels, and lead to intracranial hemorrhage.

Anthropometric Evaluation of Foramen Ovale in Adult Dry Skulls of the Mysuru-based Population

Introduction The greater wing of sphenoid presents various foramina, of which the foramen ovale is one important foramen through which advanced surgical therapeutic and diagnostic procedures related to the middle cranial fossa are performed. Materials and Methods A total of 40 dried adult skulls of unknown gender and age, obtained from the Department of Anatomy of the JSS medical College, Mysuru, Kamakata, India. The length and the width of the foramen ovale were measured using digital sliding calipers (tiny deal 150 mm SS digital caliper with LCD display, Kristeel-Shimwa industries, Bombay, India). Results The mean length of the foramen ovale was 0.745 ± 0.31 cm on the right side (RS), and 0.68 ± 0.15 cm on the left side (LS). The mean width was 0.6 ± 0.17 cm on the RS, and 0.56 ± 0.14 cm on the LS. Conclusion The knowledge of variations in the length and breadth of the foramen ovale is of immense importance in neurosurgery during various invasive surgical procedures, such as percutaneous trigeminal rhizotomy, and in the biopsy of cavernous sinus tumors and of Meckel cave lesions.

Usefulness of a Virtual Reality Percutaneous Trigeminal Rhizotomy Simulator in Neurosurgical Training

BACKGROUND Simulation-based training may be incorporated into neurosurgery in the future. OBJECTIVE To assess the usefulness of a novel haptics-based virtual reality percutaneous trigeminal rhizotomy simulator. METHODS A real-time augmented reality simulator for percutaneous trigeminal rhizotomy was developed using the ImmersiveTouch platform. Ninety-two neurosurgery residents tested the simulator at American Association of Neurological Surgeons Top Gun 2014. Postgraduate year (PGY), number of fluoroscopy shots, the distance from the ideal entry point, and the distance from the ideal target were recorded by the system during each simulation session. Final performance score was calculated considering the number of fluoroscopy shots and distances from entry and target points (a lower score is better). The impact of PGY level on residents' performance was analyzed. RESULTS Seventy-one residents provided their PGY-level and simulator performance data; 38% were senior residents and 62% were junior residents. The mean distance from the entry point (9.4 mm vs 12.6 mm, P = .01), the distance from the target (12.0 mm vs 15.2 mm, P = .16), and final score (31.1 vs 37.7, P = .02) were lower in senior than in junior residents. The mean number of fluoroscopy shots (9.8 vs 10.0, P = .88) was similar in these 2 groups. Linear regression analysis showed that increasing PGY level is significantly associated with a decreased distance from the ideal entry point (P = .001), a shorter distance from target (P = .05), a better final score (P = .007), but not number of fluoroscopy shots (P = .52). CONCLUSION Because technical performance of percutaneous rhizotomy increases with training, we proposed that the skills in performing the procedure in our virtual reality model would also increase with PGY level, if our simulator models the actual procedure. Our results confirm this hypothesis and demonstrate construct validity.

Treatment of Idiopathic Trigeminal Neuralgia: Comparison of Long-term Outcome after Radiofrequency Rhizotomy and Microvascular Decompression

OBJECTIVE To evaluate the long-term outcome of patients after either percutaneous trigeminal rhizotomy or microvascular decompression (MVD) for idiopathic trigeminal neuralgia at a single institution. METHODS From 1977 to 1997, 316 radiofrequency lesion procedures and 378 MVDs were performed. Questionnaires were sent to all patients who were alive in 1981, 1982, 1992, and 1998. For all other patients, interviews were conducted with their relatives and general practitioners. A retrospective comparative analysis was performed with Kaplan-Meier probability curves as of the latest follow-up date. In addition, 80 patients who underwent MVD were examined postoperatively with quantitative sensory measurements by use of von Frey hairs. RESULTS Two hundred twenty-five patients who underwent MVD and 206 patients who underwent radiofrequency could be analyzed retrospectively in detail. Overall, there was a 50% risk for recurrence of pain 2 years after percutaneous radiofrequency rhizotomy. Conversely, 64% of patients who underwent MVD remained completely pain free 20 years postoperatively. Patients without sensory impairment after MVD were pain free significantly longer than patients who experienced postoperative hypesthesia or partial rhizotomy. CONCLUSION Because it is curative and nondestructive, MVD is considered the treatment of choice for trigeminal neuralgia in otherwise healthy people. In our study, it proved to be a more effective and long-lasting procedure for patients with typical trigeminal neuralgia than radiofrequency rhizotomy. Patients without postoperative sensory deficit remained pain free significantly longer, which is a strong argument against the “trauma” hypothesis of this procedure.

Blood Pressure Response during Percutaneous Rhizotomy for Trigeminal Neuralgia

We observed a consistent and marked hypertensive response during trigeminal rhizotomy with methohexital anesthesia in 11 consecutive patients. Percutaneous trigeminal rhizotomy should not be regarded as a benign surgical procedure in view of the potential morbidity associated with such acute hypertension. We recommend that patients undergoing this operation be continuously monitored.