Evaluation of the inion and asterion as neurosurgical landmarks for dural venous sinuses: osteological study on a sample of South African skull specimens.

BACKGROUND: Sub-Saharan neurosurgeons most likely need to perform invasive procedures without the latest imaging and navigation technology in the operating room. Therefore, these surgeons need to utilize other methods such as superficial surface landmarks for neuro-navigation. Bony landmarks, including the inion and asterion, are commonly used during invasive procedures to pinpoint the location of the confluence of sinuses and transverse-sigmoid sinus junction, respectively. The purpose of this study was to investigate whether the inion and asterion can be used as superficial landmarks for the confluence of sinuses and the transverse-sigmoid sinus junction, respectively, in a South African population.

METHODS: Fifty South African human skulls were used (25 male, 25 female). The Micro-focus X-ray Radiography and Tomography facility (MIXRAD) at Necsa scanned and created three- dimensional virtual images of the skull specimens. Reference points were then inserted on the images and the relation between bony landmarks and venous sinuses was documented.

RESULTS: The inion was directly related to the confluence of sinuses in 4% of the sample, whereas the asterion was directly related to the transverse-sigmoid sinus junction in 28% of the cases, on both the right and left sides.

CONCLUSIONS: This study confirmed that neither the inion, nor the asterion, are directly related the confluence of sinuses and transverse-sigmoid sinus junction, respectively. These bony landmarks are more likely to be located either inferior, or not related at all, to the investigated dural venous sinuses.