title: Comparison of the transvermian and telovelar approaches to the fourth ventricle.
abstract: OBJECTIVE
  The two most common surgical routes to the fourth ventricle are the transvermian and telovelar approaches. The purpose of this study was to compare the microanatomy and exposures gained through these approaches.
  
  
  METHODS
  Ten formalin-fixed specimens were dissected in a stepwise manner to simulate the transvermian and telovelar surgical approaches. Stealth image guidance was used to compare the exposures and working angles obtained using these approaches. The transvermian and telovelar approaches provided access to the entire rostrocaudal length of the fourth ventricle floor from the aqueduct to the obex. In addition, both approaches provided access to the entire width of the floor of the fourth ventricle. The major difference between the two approaches regarded the exposure of the lateral recess and the foramen of Luschka. The telovelar, but not the transvermian, approach exposed the lateral and superolateral recesses and the foramen of Luschka. The transvermian approach, which offered an incision through at least the lower third of the vermis, afforded a modest increase in the operator's working angle compared with the telovelar approach when accessing the rostral half of the fourth ventricle.
  
  
  CONCLUSIONS
  The transvermian approach provides slightly better visualization of the medial part of the superior half of the roof of the fourth ventricle. The telovelar approach, which lacks incision of any part of the cerebellum, provides an additional exposure to the lateral recesses and the foramen of Luschka.
authors.affiliation: Department of Neurological Surgery, University of Florida, Gainesville, Florida 32610-0265, USA.
authors.forename: Necmettin
authors.initials: N
authors.lastname: Tanriover
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Ulm
authors.forename: Albert L
authors.initials: AL
authors.lastname: Rhoton
authors.forename: Alexandre
authors.initials: A
authors.lastname: Yasuda
mesh_terms: D002531:Cerebellum / Q000033:anatomy & histology / Q000098:blood supply / Q000601:surgery*; D002536:Cerebral Arteries / Q000033:anatomy & histology; D002550:Cerebral Veins / Q000033:anatomy & histology; D002831:Choroid Plexus / Q000033:anatomy & histology / Q000098:blood supply / Q000601:surgery*; D003399:Craniotomy / Q000379:methods*; D020546:Fourth Ventricle / Q000033:anatomy & histology / Q000098:blood supply / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000098:blood supply / Q000601:surgery*; D008866:Microsurgery; D038361:Neuronavigation