Internal Carotid Artery in Endoscopic Endonasal Transsphenoidal Surgery

Abstract

The transsphenoidal approach to the pituitary is widely used in pituitary surgery. Even though there are some landmarks for internal carotid artery (ICA) on the wall of the sphenoid sinus, it is not rare to get the artery injured during surgery. We found that the most important landmark, carotid prominence, matched with ICA in merely 37.5% of subjects. In order to find a simple method to locate the artery, we made an anatomical measurement of the ICA and placed the results in a 3-dimensional coordinate system. The sphenoid sinus opening is both the center of the endoscope entry in the anterior sinus wall and the origin of the coordinate system containing 3 orthogonal axes: x, y, and z. The x axis follows the body of the endoscope(out of the sphenoid sinus) parallel to the sagittal plane while z is perpendicular to the sagittal plane. Most of the measurements were obtained in the initial operative plane, which is perpendicular to the sagittal plane and contains the sinus opening and the midpoint of the pituitary fossa. We calculated the coordinates of the midpoint of the pituitary fossa and 4 ICA-related points. The depth of an ICA and the distance between 2 ICAs are also helpful in locating ICA. According to our operation method, all the projective points of the medial edge of ICA on the posterior wall of the sphenoid sinus are lateral to the sphenoid sinus opening, and operating within 0-25 degrees medial to the endoscope body is believed to be safe from ICA injury.

The pterygoclival ligament: a novel landmark for localization of the internal carotid artery during the endoscopic endonasal approach

“…The risk of ICA injury is not eliminated even with the use of endoscopic Doppler or neuronavigation. 17,32,48 Although the protuberance of the paraclival ICA is visible in many cases after exposure of the contents of the sphenoid sinus, with poorly pneumatized sinuses, the localization of the ICA becomes difficult. Even with well-pneumatized sinuses, the paraclival ICA protuberance may be missing in 30%-50% of cases.…”

“…Even with well-pneumatized sinuses, the paraclival ICA protuberance may be missing in 30%-50% of cases. 32,48 Also, the carotid protuberance could lie medial or lateral to the paraclival ICA, which could be misleading. 48 The vidian canal is an excellent landmark to localize the lacerum ICA.…”

“…32,48 Also, the carotid protuberance could lie medial or lateral to the paraclival ICA, which could be misleading. 48 The vidian canal is an excellent landmark to localize the lacerum ICA. 27,28,36,44 It runs posterolaterally from its anterior end and reaches the anterolateral part of the foramen lacerum.…”

“…Furthermore, when the vidian canal is already invaded by the tumor, lack of any consistent landmark to localize the ICA renders tumor resection extremely risky. 47,48 Therefore, when possible, efficient ICA localization prior to the commencement of tumor resection is important. The pterygoclival ligament is a structure that is naturally encountered while drilling the floor of the sphenoid sinus during transclival or transpterygoid approaches.…”

The morphometry of the cavernous part of the internal carotid artery

“…Yilmazlar et al [26] reported a statistically significant difference in the medial and posterior intercarotid distances in studies done on MRI and cadavers. Zhang et al [28] and Carrabba et al [4] measured the intercarotid distances on CT scan and found them as to be 20.6 mm and 16.65 mm, respectively. The main difference between our study and these two studies was the large size of our patient population.…”