title: Moving toward the petroclival region: a model for quantitative and anatomical analysis of tumor shift.
abstract: OBJECTIVE
  The authors quantitatively assessed the effects of balloon inflation as a model of tumor compression on the brainstem, cranial nerves, and clivus by measuring the working area, angle of attack, and brain shift associated with the retrosigmoid approach.
  
  
  METHODS
  Six silicone-injected cadaveric heads were dissected bilaterally via the retrosigmoid approach. Quantitative data were generated, including key anatomical points on the skull base and brainstem. All parameters were measured before and after inflation of a balloon catheter (inflation volume 4.8 ml, diameter 20 mm) intended to mimic tumor compression.
  
  
  RESULTS
  Balloon inflation significantly shifted (p < 0.001) the brainstem and cranial nerve foramina (mean [+/- standard deviation] displacement of upper brainstem, 10.2 +/- 3.7 mm; trigeminal nerve exit, 6.99 +/- 2.38 mm; facial nerve exit, 9.52 +/- 4.13 mm; and lower brainstem, 13.63 +/- 8.45 mm). The area of exposure at the petroclivus was significantly greater with balloon inflation than without (change, 316.26 +/- 166.75 mm2; p < 0.0001). Before and after balloon inflation, there was no significant difference in the angles of attack at the origin of the trigeminal nerve (p > 0.5).
  
  
  CONCLUSIONS
  This study adds an experimental component to the emerging field of quantitative neurosurgical anatomy. Balloon inflation can be used to model the effects of a mass lesion. The tumor simulation created "natural" retraction and an opening toward the upper clivus. The findings may be helpful in selecting a surgical approach to increase the working space for resection of certain extraaxial tumors.
authors.affiliation: Neurosurgery Research Laboratory, Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Sam
authors.initials: S
authors.lastname: Safavi-Abbasi
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Zabramski
authors.forename: Pushpa
authors.initials: P
authors.lastname: Deshmukh
authors.forename: Cassius V
authors.initials: CV
authors.lastname: Reis
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Bambakidis
authors.forename: Nicholas
authors.initials: N
authors.lastname: Theodore
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
authors.forename: Robert F
authors.initials: RF
authors.lastname: Spetzler
authors.forename: Mark C
authors.initials: MC
authors.lastname: Preul
mesh_terms: D020295:Brain Stem Neoplasms / Q000473:pathology* / Q000601:surgery*; D002102:Cadaver; D002404:Catheterization; D003388:Cranial Fossa, Posterior / Q000033:anatomy & histology* / Q000601:surgery*; D003391:Cranial Nerves / Q000473:pathology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008866:Microsurgery / Q000379:methods; D008953:Models, Anatomic; D009408:Nerve Compression Syndromes / Q000473:pathology / Q000601:surgery; D019635:Neurosurgical Procedures / Q000379:methods*