Trigeminal neuralgia is caused by maxillary and mandibular nerve entrapment: greater incidence of right-sided facial symptoms is due to the foramen rotundum and foramen ovale being narrower on the right side of the cranium.

Trigeminal neuralgia (TN) is the most important disease of the trigeminal nerve. Vascular compression of the dorsal root of the trigeminal nerve by aberrant loop of blood vessels is currently accepted as the most common cause of TN. The right side of the face is affected by TN twice as often as the left side, but there are no anatomical reasons for the blood vessels loop to be more frequent on the right side of the cranial fossa. Additionally, vascular compression in asymptomatic patients and in TN patients without aberrant blood vessels has been reported, thereby arguing against the idea that vascular compression alone is responsible for TN. Anatomical and radiological studies have shown that the rotundum and ovale foramens on the right side of the human cranium are significantly narrower than on the left side. The rotundum and ovale foramens are crossed by the maxillary and mandibular nerves, respectively, and are the nerves most affected in TN. Based on demographic and epidemiological data of TN patients, and on anatomical findings in the foramens, we hypothesized that entrapment of the maxillary and mandibular nerves when they cross the ovale and rotundum foramens is a primary cause of TN and accounts for the higher incidence of TN on the right sided.