Retrosigmoid Craniotomy and Intradural Variations: Role of Patient-Specific Preoperative Imaging to Identify Landmarks and Relevant Structures

Abstract

There are several landmarks to safely identify the limits of the retrosigmoid approach and its intradural variations, however, little has been discussed about how those landmarks may vary among patients. We provided a review of patient positions, surface landmarks for the retrosigmoid craniotomy, and structures to recognize for transmeatal, suprameatal, suprajugular and transtentorial extensions. The position of the dural sinuses in relation with the zygomatic-inion line, and digastric notch line is readily identified on MRI. For transmeatal drilling, the position of the semicircular canals, vestibular aqueduct and jugular bulb is best evaluated on CT. For suprameatal drilling, the labyrinth and the position and integrity of the carotid canal are relevant to plan the anterior extension of the approach. For transtentorial extension, it is desirable to identify incisural structures. For suprajugular drilling, the position of the jugular bulb, invasion of venous structures, and integrity of the roof of the jugular foramen must be checked preoperatively. The retrosigmoid approach is the workhorse of posterior skull base surgery. By recognizing patient-specific variations in known landmarks, the approach may be tailored prevent complications.