Anatomic variations of foramen ovale.

OBJECTIVES Foramen ovale is of great surgical and diagnostic importance in procedures like percutaneous trigeminal rhizotomy for trigeminal neuralgia, transfacial fine needle aspiration technique in perineural spread of tumour and electroencephalographic analysis for seizure. This study presents the anatomic variations in dimensions, appearance and number of foramen ovale. METHODS We studied 35 dried human skulls available in the Department of Anatomy, Manipal college of Medical Sciences, Pokhara, Nepal. Variations in appearance and number of foramen ovale were noted. Length and width of foramen ovale was measured. Comparison with other races and differences between right and left sides were also discussed. RESULTS Out of 70 sides in 35 adult skulls, mean length and width of foramen ovale was 7.46+/-1.41 mm and 3.21+/-1.02 mm on right side and 7.01+/-1.41 mm and 3.29+/-0.85 mm on left side. Shape of foramen ovale was typically oval in 43, (22 on right, 21 on left) almond shape in 24 (Fig.1, arrowhead; 11 right, 13 left), round in 2(1 right, 1 left) and slit-like in 1(Fig.1, arrow). Bilateral oval foramen was observed in 15 and bilateral almond was in 7. Out of 70 sides in 35 adult skulls 3 (2 left, 1 right) sides had spine on the margin of the foramen (Fig.2, arrow), 3 (2 left, 1 right) had tubercle protruding from the margin (Fig. 3, arrow), 2 (1 left, 1 right) sides had bridge like bony spur dividing the foramen into two compartments(Fig. 2, arrowhead), 9 (5 left, 4 right) had bony plate on the margin of foramen ovale (Fig. 4, arrow). Variant foramen ovale was observed in 24.2%. CONCLUSION Anatomical variations in size and shape of foramen ovale could be explained by developmental reasons. Considering the immense surgical and diagnostic importance of foramen ovale, this study was worthwhile.