Anatomy and clinical importance of the extracranial clivus and surrounding structures

The aim of this study was to reveal the clinical importance of measurements taken from the pharyngeal tubercle (PT) to various anatomical structures around the extracranial clivus. Twenty-six adult dry Anatolian skulls were examined. The extracranial clivus and PT were used as landmarks from which various distances were measured using a digital caliper accurate to 0.01 mm. The following mean distances from the PT were observed; foramen lacerum (FL) (L: 17.15 mm, R: 17.4 mm); medial external margin of the carotid canal (CC) (L: 26.7 mm, R: 27.5 mm); anterior tip of occipital condyle (OC) (L: 16.4 mm, R: 16.3 mm); anterior margin of foramen magnum (FM) (10.8 mm); foramen ovale (FO) (L: 25.9 mm, R: 29.1); medial margin of the jugular fossa (JF) (L: 25.4 mm, R: 25.7 mm); medial external margin of the hypoglossal canal (HC) (L: 20.0 mm, R: 19.9 mm). Mean bilateral distances were: LFO-RFO: 45.34 mm; LFL-RFL: 20.1 mm; LCC-RCC: 52.1 mm; LOC-ROC: 17.6 mm; LJF-RJF: 45.2 mm; LHC-RHC: 33.5 mm. The following mean distances were observed from the FM: FM-OC (L: 8.3 mm, R: 9.3 mm); FM-HC (L: 17.8 mm, R: 17.4 mm). Also the mean distance of OC-HC were observed (L: 11.7 mm, R: 11.4 mm). Present measurements suggest that the PT can be used as an anatomical landmark during surgery involving clival pathology. However, the anatomy and variations of the extracranial clivus and surrounding structures must be taken into consideration.