Anatomical study of the relatively safe needling angle of minimally invasive treatment for trigeminal neuralgia.

Trigeminal neuralgia affects approximately 182 in 100,000 Chinese, and the number keeps increasing these years. The role of surgery for patients with medically refractory trigeminal neuralgia is well established. Computed tomographic images provided by the First Affiliated Hospital of Jilin University were used to reconstruct the 3-dimensional skull models. We measured the positional relationship between oval foramen and trigeminal impression to analyze the relatively safe puncture angle for the internal carotid artery protection. Point O, A, and B are the projection of 3 points on plane C: the center of oval foramen, the medial edge of trigeminal impression, and the lateral edge of trigeminal impression, respectively. The length of OA was 11.02 mm (95% confidence interval [CI], 10.64-11.40 mm), and OB was 13.59 mm (95% CI, 13.20-13.98 mm). Angle study included the angle contained by the median sagittal plane and OA or OB, angle alpha or beta, and the angle contained by OA and OB, angle gamma. Angle alpha was 50.74 degrees (95% CI, 48.60-52.88 degrees). Angle beta was 6.62 degrees (95% CI, 4.02-9.22 degrees). Angle gamma was 44.12 degrees (95% CI, 41.95-46.29 degrees). So the ideal horizontal angle between the needle axis and the median sagittal plane ranges between angle alpha and beta, 6.62 to 50.74 degrees, and the best puncture angle should be 33.18 degrees. The depth of needling insertion after entering the oval foramen should be less than the minimum length of the 95% CI of OA and OB, 10.64 mm.