Foramen ovale puncture, lesioning accuracy, and avoiding complications: microsurgical anatomy study with clinical implications

Abstract

F oramen ovale puncture was first described by Här-tel in 1914 18 as a percutaneous route to the Meckel cave to treat trigeminal neuralgia. Microvascular decompression induces little or no hypesthesia and is usually the treatment of choice for young patients without comorbidities.3 However, less invasive techniques, including FO puncture, are preferred Object. Foramen ovale (FO) puncture allows for trigeminal neuralgia treatment, FO electrode placement, and selected biopsy studies. The goals of this study were to demonstrate the anatomical basis of complications related to FO puncture, and provide anatomical landmarks for improvement of safety, selective lesioning of the trigeminal nerve (TN), and optimal placement of electrodes.Methods. Both sides of 50 dry skulls were studied to obtain the distances from the FO to relevant cranial base references. A total of 36 sides from 18 formalin-fixed specimens were dissected for Meckel cave and TN measurements. The best radiographic projection for FO visualization was assessed in 40 skulls, and the optimal trajectory angles, insertion depths, and topographies of the lesions were evaluated in 17 specimens. In addition, the differences in postoperative pain relief after the radiofrequency procedure among different branches of the TN were statistically assessed in 49 patients to determine if there was any TN branch less efficiently targeted.Results. Most severe complications during FO puncture are related to incorrect needle placement intracranially or extracranially. The needle should be inserted 25 mm lateral to the oral commissure, forming an approximately 45° angle with the hard palate in the lateral radiographic view, directed 20° medially in the anteroposterior view. Once the needle reaches the FO, it can be advanced by 20 mm, on average, up to the petrous ridge. If the needle/radiofrequency electrode tip remains more than 18 mm away from the midline, injury to the cavernous carotid artery is minimized. Anatomically there is less potential for complications when the needle/radiofrequency electrode is advanced no more than 2 mm away from the clival line in the lateral view, when the needle pierces the medial part of the FO toward the medial part of the trigeminal impression in the petrous ridge, and no more than 4 mm in the lateral part. The 40°/45° inferior transfacial-20° oblique radiographic projection visualized 96.2% of the FOs in dry skulls, and the remainder were not visualized in any other projection of the radiograph. Patients with V1 involvement experienced postoperative pain more frequently than did patients with V2 or V3 involvement. Anatomical targeting of V1 in specimens was more efficiently achieved by inserting the needle in the medial third of the FO; for V2 targeting, in the middle of the FO; and for V3 targeting, in the lateral third of the FO.Conclusions. Knowledge of the extracranial and intracranial anatomical relationships of the FO is essential to understanding and avoiding complications during FO puncture. These data suggest that better rad...

Percutaneous Procedures for the Treatment of Trigeminal Neuralgia

“…Much effort has been devoted to improving visualization and navigation to the foramen ovale. 89 Although fluoroscopy has been the imaging modality of choice, newer studies have demonstrated the potential usefulness of computed tomography, Dynacomputed tomography, and neuronavigation systems, especially for patients with anatomic variants that may prevent successful access with traditional means. [90][91][92][93] In 1 study of RFT, guidance with computed tomography fluoroscopy allowed for successful engagement of the foramen ovale on the first attempt, all requiring less than 40 seconds.…”

Morphology and Location of Surface Landmarks of Foramen Ovale in Kenyans

“…A comparison our results against population data provided by Hwang et al (2005), Onswuke et al (2010), Ambica et al (2012) and Peris-Celda et al (2013) showed that our measurements are significantly different from other populations. The results of these studies are summarized in Table II below.…”

Anatomical Study of Percutaneous Trigeminal Compressive Balloon Positioning on Merged 3-D Rotational X-Ray and Preprocedural Magnetic Resonance Imaging

“…The abducens and trochlear nerves can be damaged by rhizotomy instrumentation and penetration into the temporal lobe or brainstem can also occur [20]. Reviewing cadaveric studies can help guide against these complications [15].…”

“…The risk for serious injury to adjacent neural and vascular structures from aberrant placement of the percutaneous trigeminal cannula must be considered [15][16][17][18]. Many complications have been reported after percutaneous balloon rhizotomy, but the most frequent are masticatory muscle weakness and dysesthesias, both of which typically improve in the postoperative period [19].…”

“…We now use a custom 4-inch 14-gauge blunted needle with a stylet. The needle is guided through the cheek with the surgeon's hand in the patient's mouth, protecting from the medial breach of the needle into the oropharynx, targeting a visualized point 3 cm anterior to the external auditory meatus and in line with the medial aspect of the ipsilateral pupil [15]. Bone is encountered and sequential X-rays guide minor positioning adjustments until the cannula is within the foramen ovale and has punctured Meckel's cave.…”