Angular Relationship Between the Foramen Ovale and the Trigeminal Impression: Percutaneous Cannulation Trajectories for Trigeminal Neuralgia.

The debilitating pain of trigeminal neuralgia often necessitates neurosurgical intervention via percutaneous transovale cannulation. While most percutaneous treatments of trigeminal neuralgia are successful, severe adverse events resulting from failure to properly cannulate the foramen ovale (FO) have been reported. With regard to specific targeting of particular trigeminal divisions (ie, V1, V2, V3, and combinations thereof), operative techniques have been described; however, these descriptions have not included specific angulation data. This anatomic study analyzed the angular relationship between the centroid and anteromedial- and posterolateral-most aspects of the FO and the boundaries of the trigeminal impression. The study is the first to detail the angular relationship between the FO boundaries and the boundaries of the trigeminal impression in dry human skulls relative to the coronal plane. The information may be used to prevent miscannulation and also target specific branches of the trigeminal nerve for optimal operative results.

Circularity, Solidity, Axes of a Best Fit Ellipse, Aspect Ratio, and Roundness of the Foramen Ovale: A Morphometric Analysis With Neurosurgical Considerations.

The structure of the foramen ovale of the sphenoid bone is clinically important, particularly with regard to surgical procedures that cannulate the foramen such as percutaneous trigeminal rhizotomy for the treatment of trigeminal neuralgia, percutaneous biopsy of parasellar lesions, and electroencephalographic analysis of the temporal lobe among patients undergoing selective amygdalohippocampectomy. Differences in the morphology of the foramen ovale (FO) have been reported to contribute to difficulties in the cannulation of the FO. Reports regarding the structure of the FO, however, use subjective and ambiguous descriptions of morphology, including "oval," "truly oval," "elongated oval," "elongated," "semicircular," "almond," "round," "rounded," "slit," "irregular," "D shape," and "pear." Therefore, it is necessary to describe the structure of the FO with reproducible objective morphometric data. This study analyzed 169 foramina to determine normative morphometric shape descriptions of the following: area, perimeter, circularity, solidity, axes of a best fit ellipse, aspect ratio, and roundness. The shape descriptors reported herein may aid in identification and description of structural variation in FO including bony projections encroaching upon the foramina and may improve surgical approaches to transovale cannulation.

Orientation of the Foramen Ovale: An Anatomic Study With Neurosurgical Considerations.

Unsuccessful cannulation of the foramen ovale (FO) continues to occur with both fluoroscopic technique and technique using computed tomography paired with navigational technology. Despite advances in stereotactic neurosurgical imaging and technique, anatomic variation of the FO occasionally prevents successful cannulation. Morphometric study of the FO has been limited to length, width, and area parameters; therefore, this report analyzed the orientation of the FO. A total of 139 crania (235 foramina ovalae) were photographed and assessed digitally by ImageJ software (NIH). Foramina were fit with a best fit ellipse. For orientation, the midsagittal plane was located by bisecting the basilar process of the occiput; the coronal plane was identified as perpendicular to the midsagittal plane. The angles between the major axis of the best fit ellipse of the FO and the midsagittal and coronal planes were measured. The angle formed between the major axis of the best fit ellipse of the FO and the coronal plane averaged 35.43° ± 9.74° (mean ± SD) on the left and 36.47° ± 7.60° on the right. The angle formed between the major axis of the best fit ellipse of the FO and the sagittal plane averaged 54.57° ± 9.74° on the left and 53.53° ± 7.60° on the right. No significant difference was found between FO orientation among the sexes. Understanding the orientation of the FO may aid in stereotactic neurosurgical planning and successful cannulation of the FO.