Localization of transverse-sigmoid sinus junction using preoperative 3D computed tomography: application in retrosigmoid craniotomy.

In retrosigmoid craniotomy, neurosurgeons usually depend on surface landmarks and their experience to evaluate the position of transverse-sigmoid sinus junction (TSSJ) and place an appropriate initial burr-hole, which is not accurate each time because of variability in different craniums. The authors introduce a simple procedure based on 3D computed tomography (CT) to localize the TSSJ in retrosigmoid craniotomy. Eighteen patients who underwent retrosigmoid craniotomy were analyzed. On the internal view of skull in 3D CT image, a simulative burr-hole was placed on the margin of transverse-sigmoid sinus groove junction. Then, on the external view of skull in 3D CT image, the center of the simulative burr-hole was marked and a coordinate system was established based on a line connected the digastric point and the asterion. Then the coordinate of the burr-hole's center was measured in this coordinate system. In operation, the burr-hole was placed according to the coordinate measured previously and craniotomy was performed. The margin of TSSJ was exposed in each case. No damage of venous sinus was encountered. Post-operative skull base CT demonstrated a good match between the actual and predicted burr-hole and bone defects only existed along the cut line. This simple method could help in localizing the TSSJ and avoiding the risk of sinus injury and reducing the bone defect. It is sufficiently precise for practical application at surgical planning.