Quantitative study of the retrosigmoid suprameatal approach for petrous apex resection LI

Objective To evaluate the safety and feasibility of the retrosigmoid suprameatal approach (RSSMA) for petrous apex resection. Methods Ten human dry skull and 18 cadaverie skull specimens were collected and 3-dimensional CT scanning was performed with slice thickness of 1 mm. Craniotomy was performed on the specimens through a modified retrosigmoid approach, and the suprameatal tubercle (ST) and petrous apex (PA) were removed without damaging the trigerninal and facial nerves. The petrous bone was resected to the farthest lateral margin (FLM) that the approach could allow. CT-based and manual measurements were used to determine the lateral-middle line, superior-inferior, anterior-posterior lengths of the ST and PA. The superolateral lip of the internal auditory meatus (SLIAM) was defined as the landmarks for the measurement, and the distances from the SLIAM to the fundus, the common crus, and vestibule was determined. Results From thesuperior-inferior to the anterior-posterior and median-lateral directions, the resection rate of the PA increased to (26.6±6)%, (45±5)%, and (72±6)%, and the rate for the ST to (69±10)%, 100%, and 100%, respectively. The resection rate of the PA at the siphonal portion was (44±7)%. In the RSSMA, the distance from the SLIAM to the FLM (17.6±2.0 mm) was greater than the distances from the SLIAM to the vestibule (10.1±1.4 mm), the fundus (10.4±1.5 mm), and the common crus (10.6±1.1 mm). Conclusions The RSSMA may well protect the siphonal portion of the internal carotid artery from damages in PA resection. The FLM of the RSSMA is always lateral to the vestibule and the fundus of the internal auditory canal and the common crus, and therefore injuries to the vestibule, the semicircular canal and the common crus should be avoided. Key words: Retrosigrnoid suprameatal approach; Imaging anatomy; Petrous bone