No abstract

The difficulty in the operation for basilar tip aneurysm is the restriction in surgical working space. To resolve this problem, aggressive skull base surgery has been reported, but these techniques are not prevalent. Pterional and subtemporal approaches are commonly used for basilar tip aneurysms. In an attempt to increase the surgical working space during the pterional approach, the anterior clinoid process and the roof of the optic nerve were removed extradurally to increase the mobilization of the intracranial internal carotid artery and optic nerve. The effects of removing the anterior clinoid process and microanatomy in the perioptic area were analyzed by cadaveric procedures in 10 cases (20 sides). With this procedure, the internal carotid artery can be retracted medially with a spatula 6.1 +/- 0.8 mm (mean +/- SD). The length and the area of dural fold in the bone defect region in the optic canal roof are 2.1 mm and 13.6 mm. In 10 clinical cases, this procedure allowed enough space to approach the basilar tip aneurysm without disturbing the internal carotid artery blood flow. The clinical outcome was satisfactory.

Abstract. The relations between angiographic manifestations and operative findings of hemifacial spasm were studied in 70 cases between 1988 and 2001. Vertebral angiography was performed, and Towne, straight AP, and lateral projections were routinely examined. The dominant anterior inferior cerebellar artery (AICA) directly compressed the facial nerve root exit zone in 26 cases, the dominant posterior inferior cerebellar artery (PICA) in 20, the AICA in 13, the PICA in 2, and the vertebral artery (VA) in 9. Compression by multiple vessels was observed in 11 cases. Anatomical variations of the affected AICA and PICA were classified into 3 groups according to their origins and distributions of blood supply: normal distribution of AICA and PICA in 18%, common trunk anomaly with domi nant AICA (basilar artery origin) in 48% and common trunk anomaly with dominant PICA (vertebral artery origin) in 34%. Analyses of the angiograms revealed significantly increased numbers of common trunk anomalies compared with cases with normal angiograms. In 18 of the 20 cases of unilateral common trunk anomalies, facial nerves were compressed by the dominant artery. Preoperative verte bral angiograms may clarify the offending vessels and their sites in most hemifacial spasm cases, thus increasing the safety of surgical interventions. (Keio J Med 52 (3): 189-197, September 2003)

This technical note describes a simple method for reducing the dead space created by craniotome due to the loss of bone dust and improving the cosmetic outcome following a craniotomy. After drilling the burr holes for the craniotomy, the bone between the holes is drilled away in a standard fashion except that multiple regions of about 1 cm in length are left intact. These intact regions are broken using a periosteal elevator and fixed like a bridge when the bone is replaced. The resulting bone flap is readily returned to its original position without making the dead space created by regular craniotomy. The amount of the dead space caused by losing the bone dust is reduced and a good cosmetic recovery is obtained. This technique is useful for both craniotomy and facial bone surgery, which requires cosmetic results.

An important consideration in neurosurgical procedures is avoiding retraction of the brain. Sindou and Fobe' reported on the usefulness of removing the roof of the external auditory meatus to avoid the excessive retraction of the temporal lobe or to prevent damage to the venous sinus and Labbe's vein while approaching the tentorial edge. this surgical approach is used for treatment at the tentorial notch, but in our surgical experience with cerebropontine angle lesions, it is also useful for posterior fossa lesions and upper clival lesions. In approaching acoustic neurinomas by the extended middle cranial fossa,24 we found this method to be useful in accessing not only a tentorial lesion but one situated lower than the tentorium. There has been some confusion about the extent of removal of the roof of the external auditory meatus. We report on the extent of bone removed in cadavers. METHODSWith a transtentorial transpetrosal approach to a lesion lower than the tentorium, the operative field is very deep and limited, but with a removal of the roof of the external auditory meatus, the entry zone is enlarged and the lesion is more easily accessible (Fig. 1). The 59 Skull Base Surgery, Volume 10, Number