The pterional-transsylvian approach: an analytical study.
OBJECTIVE
Splitting of the sylvian fissure (SF) improves exposure with the pterional (PT) approach. Traditionally, the choice of whether or not to split the SF and how far to open it has depended on the neurosurgeon's experience and preference rather than on quantifiable data. We undertook this study to evaluate the effects of progressive splitting of the SF on surgical exposure with the PT approach.


METHODS
A PT craniotomy was performed on nine sides of cadaver heads. Splitting the SF was divided into four steps: 1) dissection of the basal cisterns, 2) dissection of the sphenoidal compartment, 3) dissection of the operculoinsular compartment to the anterior ascendant ramus, and 4) dissection progressing 2.0 cm distal to the anterior ascendant ramus. The degree of the retraction and the relative position of the brain retractors were kept constant. After each step, we used a computerized tracking system to measure the area of surgical exposure of the circle of Willis, the angles of approach to the carotid bifurcation, and the distance between the frontal lobe and skull base.


RESULTS
Exposure of the circle of Willis, angles of approach to the carotid bifurcation, and linear distance between the frontal lobe and skull base all increased significantly as splitting of the SF progressed from Steps 1 to 2 and from Steps 2 to 3. There was no significant difference between Steps 3 and 4.


CONCLUSIONS
Exposure of the basal cisterns and circle of Willis by the PT approach is optimized when dissection of the SF reaches the anterior ascendant ramus. Further splitting of the SF provides no additional gain.
Figueiredo
Eberval Gadelha
EG
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, USA.
Deshmukh
Pushpa
P
Zabramski
Joseph M
JM
Preul
Mark C
MC
Crawford
Neil R
NR
Spetzler
Robert F
RF
D002102:Cadaver; D002535:Cerebral Aqueduct / Q000033:anatomy & histology* / Q000601:surgery*; D002941:Circle of Willis / Q000033:anatomy & histology* / Q000601:surgery*; D003399:Craniotomy / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D019635:Neurosurgical Procedures / Q000379:methods*; D017410:Practice Guidelines as Topic; D010818:Practice Patterns, Physicians'