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.

Carotico-clinoid foramina and a double optic canal: A case report with neurosurgical implications.

BACKGROUND: The lesser wing of the sphenoid is a clinically important structure, particularly with regard to its anatomical relationship with neurovascular structures including the optic nerve, ophthalmic artery, and internal carotid artery. Anterior clinoidectomy, a neurosurgical procedure utilized to access paraclinoid aneurysms and neoplasms, is often complicated by the presence of anatomical variants including the carotico-clinoid foramen and the accessory optic canal. CASE DESCRIPTION: A rare case report is presented documenting the simultaneous occurrence of bilateral carotico-clinoid foramina and a unilateral accessory optic canal. CONCLUSION: The presence of an accessory optic canal may be misconstrued as a carotico-clinoid foramen or pneumatization of the anterior clinoid process, lesser sphenoidal wing, or optic strut. The case report documents two clinically important variant structures occurring ipsilaterally, each with the potential to masquerade as the other radiographically and present complications to both neurosurgeons and radiologists. Knowledge of the unique combination of anatomical variants presented in this report may prevent adverse surgical events during anterior clinoidectomy procedures including hemorrhage of the ophthalmic artery or internal carotid artery and subsequent vision loss or death.