Transpetrosal Combined Supratentorial and Infratentorial Approach for Midline Vertebro-Basilar Aneurysms
Difficulties are often encountered in the surgical approach to vertebrobasilar aneurysms situated in the midline at the level of the middle third of the clivus. The subtemporal transtentorial approach reported by Drake (2) gives inadequate room for manipu
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Difficulties are often encountered in the surgical approach to vertebrobasilar aneurysms situated in the midIine at the level of the middle third of the c1ivus. The subtemporal transtentorial approach reported by Drake (2) gives inadequate room for manipulation of the lower side of the aneurysm neck, particularly when the aneurysm is large in size and fills the depths of the narrow operative field. A conventional lateral suboccipi· tal approach has a similar limitation for the upper side of the aneurysm neck. The transoral dival approach has the serious drawback of a high risk of postoperative infection. A combined supratentorial and infratentorial approach as described by Kasdon and Stein (4) allows wider exposure along the whole length of the divus, but the division of the sigmoid sinus is not always without risk. This paper presents an alternative method of exposure, by which the sigmoid sinus is preserved and a better view along the course of the vertebro-basilar trunk can be obtained. The approach consists of a combined subtemporal and lateral suboccipital craniotomy, removal of the bone at the postero-superior aspect of the petrous pyramid, and dural opening over the temporallobe being extended inferiorly along the anterior border of the sigmoid sinus by division of the superior petrosal sinus and tentorium. The technical details are described by the operation performed for a case with a midline situated right vertebral artery aneurysm (case 3).
Surgical Technique The patient was placed in the head-up lateral position with the head flexed and tilted laterally so as to bring the sagittal plane of the head parallel to the horizontal plane. A hook-shaped scalp inci sion was made starting from a point 5 em above the external auditory meatus extending down to a point l cm below and posterior to the tip of the mastoid process (Fig. IA). The sealp flap was refleeted. A small temporal bone flap and lateral suboccipital eranieetomy were made. The bone over the transverse sinus was removed and both eraniotomies were eombined. The bone over the sigmoid sinus and posterior half of the mastoid process was carefully shaved off using an air drill, until the sigmoid sinus was fully exposed. Then, the petrous bone of the floor of the middle fossa and the portion anterior to the sigmoid sinus were drilled off to expose 442
Modern Neurosurgery 1. Edited by M. Brock © Springer-Verlag Berlin· Heidelberg 1982
the terminal portion of the superior petrosal sinus and a narrow dural strip of approximately 1 cm in width along the anterior border of the sigmoid sinus. In order to avoid possible damage of the semicircular canals situated in the petrous pyramid, the removal of the bone in the supero-posterior aspect of the petrous pyramid was confmed to the thin layer necessary to expose a small area sufficient for dural inci sion (Fig. 1B). The microscope was then used and the dura over the temporallobe was opened. A vertical dural incision was extended inferiorly along the anterior border of the sigmoid sinus by divis
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