The craniocaudal extension of posterolateral approaches and their combination: a quantitative anatomic and clinical analysis.

OBJECTIVE: The aim of this study was to describe quantitatively the properties of the posterolateral approaches and their combination.

METHODS: Six silicone-injected cadaveric heads were dissected bilaterally. Quantitative data were generated with the Optotrak 3020 system (Northern Digital, Waterloo, Canada) and Surgiscope (Elekta Instruments, Inc., Atlanta, GA), including key anatomic points on the skull base and brainstem. All parameters were measured after the basic retrosigmoid craniectomy and then after combination with a basic far-lateral extension. The clinical results of 20 patients who underwent a combined retrosigmoid and far-lateral approach were reviewed.

RESULTS: The change in accessibility to the lower clivus was greatest after the far-lateral extension (mean change, 43.62 +/- 10.98 mm2; P = .001). Accessibility to the constant landmarks, Meckel's cave, internal auditory meatus, and jugular foramen did not change significantly between the 2 approaches (P > .05). The greatest change in accessibility to soft tissue between the 2 approaches was to the lower brainstem (mean change, 33.88 +/- 5.25 mm2; P = .0001). Total removal was achieved in 75% of the cases. The average postoperative Glasgow Outcome Scale score of patients who underwent the combined retrosigmoid and far-lateral approach improved significantly, compared with the preoperative scores.

CONCLUSION: The combination of the far-lateral and simple retrosigmoid approaches significantly increases the petroclival working area and access to the cranial nerves. However, risk of injury to neurovascular structures and time needed to extend the craniotomy must be weighed against the increased working area and angles of attack.