European Journal of Cardiovascular Medicine

The skull foramina exist as the ossification of the skull base occurs around preexisting vessels and cranial nerves. After the 8^th week of gestation, the cartilage development begins around the already apparent vessels and nerves. The cartilaginous ossification of the greater sphenoidal wing begins at the 15^th gestational week and until the 22^nd week; the FO appears in the greater wing of the sphenoid[1]. The foramen ovale is present in the infratemporal surface of the greater wing of sphenoid and it is an important foramen which transmits the mandibular division of the trigeminal nerve, lesser petrosal nerve, emissary veins, and accessory meningeal vessels.  The mandibular nerve which traverses the foramen ovale and trigeminal ganglion that is situated in the Meckel’s cave are targeted by neurosurgeons and pain physicians in patients with trigeminal neuralgia [2].

The foramen is an important landmark for middle cranial fossa surgery as well as diagnostic procedures, such as electroencephalographic analysis of the seizure for patients undergoing selective amygdalohippocampectomy, microvascular decompression by percutaneous trigeminal rhizotomy for trigeminal neuralgia, and percutaneous biopsy of cavernous sinus tumours[1,3]. The morphology and morphometry of foramen ovale are different among various subgroups of human population. These morphometric details are lacking in the Indian population to the best of our knowledge. Trigeminal rhizotomy procedures which are done for treating trigeminal neuralgia necessitate an in-depth knowledge about the foramen ovale[2,4]. Percutaneous ballon compression, radiofrequency rhizotomy, and glycerol rhizotomy, performed via transovale cannulation for the treatment of trigeminal neuralgia, have been facilitated by a variety of localization modalities. Fluoroscopy is a particularly common method for transovale cannulation.  The present study conducted to add addition knowledge which may help to neurosurgeons in surgeries performing through transovale, anatomists, forensic surgeons and anthropologists.

We have conducted present study in multiple medical and dental institutions, we have collected the adult dry skulls from first years medical and dental students. We have examined all the skulls carefully and we have not separated according to gender. We have used digital vernier callipers for measurements. We have excluded damaged skulls where base of skull was damaged. We have measured the length and breadth of the skull carefully. We have measured the anteroposterior diameter or length and transverse diameter or width of the foramen ovale of both sides and average. Each dimension was measured, while mean figures were recorded. Area of the foramen ovale was calculated using the formula: (π × L × B)/4 or (3.142 × L × B)/4[1,5,6].

In present study we have observed the morphology of foramen ovale, we found the oval shape foramen ovale in 82.33% cases, in right side it was found in 83.33% foramens and left it was 81.33% foramens.  Round shape found in 12.33% cases, right side it was 13.33% foramens and left side it was 11.33% foramens. Almond shape were in 3.66% cases, right side it was 2.66% and left it was 4.66% foramens. Irregular found in 1.66% cases, right side it was 0.66% foramens and left side 2.66% foramens (Table 1). As part of morphometric evaluation, we measured the length of foramen ovale was on left side was 8.24+1.86 mm and right it was 8.96+1.44mm. The breadth of foramen ovale was on left side was 5.74+1.06 mm and right it was 5.32+0.84mm. The area of foramen ovale was on left side was 37.13+1.54 mm and right it was 37.41+0.94mm(Table 2).

The cerebral surface of each greater wing of sphenoid bone forms part of the middle cranial fossa of the skull containing numerous foramina and fissures, which accommodate several vessels and nerves. Foramen ovale is located in the posterior part of the greater wing for the transmission of the mandibular nerve, the accessory meningeal artery, lesser petrosal nerve and an emissary vein. This foramen is normally located in the greater wing of the sphenoid bone, posterior and lateral to the foramen rotundum and it opens into the infratemporal fossa through its other opening on the lateral surface of greater wing[7]. In present study we have observed the shapes of foramen ovale, out of all shapes oval shape were majority and next to it round, almond and irregular taken place respectively. We also measured the length and breadth of foramen ovale, calculated area of foramen also.

In study of Prakash KG [1] of 82 adult skulls, the values for the right side was 7.64 ± 1.194 mm, 5.128 ± 0.827 mm, and 30.808 ± 7.545 mm² and for the left side the values was 7.561 ± 1.123 mm, 5.244 ± 0.950 mm, and 31.310 ± 8.262 mm², respectively, for the mean length, width, and area of the FO. The shape of foramen was typically ovale in most of the skulls (56.70%) with some bony variations such as spine, tubercles, bony bridge/bar, and confluence.

1. Prakash KG, Saniya K, Honnegowda TM, Ramkishore HS, Nautiyal A. Morphometric and Anatomic Variations of Foramen Ovale in Human Skull and Its Clinical Importance. Asian J Neurosurg. 2019 Nov 25;14(4):1134-1137. doi: 10.4103/ajns.AJNS_243_19. PMID: 31903352; PMCID: PMC6896638.
2. Shankar, Gowri1; Muthukumaravel, N.1,. A Morphological and Morphometric Study of Foramen Ovale in Dry Skulls of Indian Population. National Journal of Clinical Anatomy 8(1):p 38-42, Jan–Mar 2019. | DOI: 10.1055/s-0039-1688892.
3. Kantola VE, McGarry GW, Rea PM. Endonasal, transmaxillary, transpterygoid approach to the foramen ovale: Radio-anatomical study of surgical feasibility. J Laryngol Otol. 2013;127:1093–102. 
4. Stozitzky Munoz N, Rueda-Esteban RJ. Morphometric study of five constant skull base foramina in the Muisca population of the Tibanica anthropological collection of the Universidad de Los Andes Int J Morphol. 2016;34:1313–1317.
5. Gerber AM. Improved visualization of the foramen ovale for percutaneous approaches to the gasserian ganglion: Technical note. J Neurosurg. 1994;80:156–9.
6. Osunwoke EA, Mbadugha CC, Orish CN, Oghenemavwe EL, Ukah CJ. A morphometric study of foramen ovale and foramen spinosum of the human sphenoid bone in the Southern Nigerian population. J Appl Biosci. 2010;26:1631–5.)