Foramen rotundum versus canal of the maxillary verve

The foramen rotundum, located in the greater wing of the sphenoid bone, transmits the maxillary nerve (V2) from the middle cranial fossa to the pterygopalatine fossa. Despite its designation as a foramen, this structure possesses measurable length, suggesting it functions as a canal. While cross-sectional dimensions have been documented, canal length remains underreported. This study aimed to evaluate the morphometric characteristics of the foramen rotundum canal (FRC) using cone-beam computed tomography (CBCT).

A retrospective study was conducted on CBCT scans of 45 adult patients (27 males, 18 females) acquired using an iCAT system. Multiplanar reconstructions were analysed using Planmeca Romexis software. Canal length was measured bilaterally from the intracranial to extracranial opening. Statistical analysis included paired and independent t-tests, Wilcoxon signed-rank and Mann-Whitney U tests, with significance set at p < 0.05.

Eighty-eight FRC measurements were analysed. Mean canal length was 4.07 ± 1.78 mm (range: 0.75-9.12 mm), with a coefficient of variation of 43.8%. The left side demonstrated significantly longer canals than the right (4.33 ± 1.77 mm vs. 3.81 ± 1.77 mm; p = 0.013). Males showed longer canals than females (4.22 ± 1.87 mm vs. 3.84 ± 1.65 mm), though not statistically significant (p = 0.325). One case with bilateral accessory foramina rotunda was identified and described separately.

The foramen rotundum demonstrates measurable canal-like dimensions with considerable variability and significant left-sided predominance. These findings support reconceptualising this structure as the FRC, with implications for skull base surgery and trigeminal interventions.