ons54 | VOLUME 66 | OPERATIVE NEUROSURGERY 1 | MARCH 2010 www.neurosurgery-online.com CRANIAL BASE Surgical Approach Sam Safavi-Abbasi, MD, PhD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Jean G. de Oliveira, MD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Pushpa Deshmukh, PhD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Cassius V. Reis, MD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Leonardo B.C. Brasiliense, MD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Neil R. Crawford, PhD Division of Neurological Surgery, and Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Iman Feiz-Erfan, MD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Robert F. Spetzler, MD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Mark C. Preul, MD Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona Reprint requests: Mark C. Preul, MD, c/o Neuroscience Publications, Barrow Neurological Institute, 350 W. Thomas Road, Phoenix, AZ 85013. Email: neuropub@chw.edu Received, July 3, 2008. Accepted, May 18, 2009. Copyright © 2010 by the Congress of Neurological Surgeons O riginally, the far-lateral approach was described as an inferolateral extension and modification of the simple suboccipital retrosigmoid craniotomy to increase the exposure of neurovascular structures in this region. 1-4 Several modifications with more lateral extensions have been described and debated extensively, 5-12 and excellent anatomic studies have evaluated the transcondylar, supracondylar, and paracondylar variants of the far-lateral approach. 4,13-15 However, the craniocaudal extensions of posterolateral approaches have not been the subject of attention thus far. In this study, we evaluated and compared the merits of the basic posterolateral approaches, the retrosigmoid and far-lateral routes, and, in partic- ular, their combination. Our focus was the cran- iocaudal rather than the lateral extension of these approaches that has not been evaluated compre- hensively before. We relate our quantitative anatomic findings with the clinical decision making regard- ing the extension of the approach and manage- ment of various lesions through a combined retrosigmoid and far-lateral (CRSFL) approach. PATIENTS AND METHODS Anatomic Study The arterial and venous systems of 6 cadaveric heads with no known brain pathology were injected with col- 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 pos- terolateral 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 mm 2 ; P = .001). Accessibility to the constant land- marks, Meckel’s cave, internal auditory meatus, and jugular foramen did not change sig- nificantly 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 mm 2 ; P = .0001). Total removal was achieved in 75% of the cases. The average postopera- tive 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. KEY WORDS: Far-lateral approach, Petroclival region, Quantitative anatomic study, Retrosigmoid approach Neurosurgery 66[ONS Suppl 1]:ons54-ons64, 2010 DOI: 10.1227/01.NEU.0000354366.48105.FE ABBREVIATIONS: CPA, cerebellopontine angle; CRSFL, combined retrosigmoid and far-lateral; GOS, Glasgow Outcome Scale