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Patients with massive brain swelling undergo external decompressive craniectomy to manage intracranial pressure. Following supratentorial craniectomy, and after the brain swelling is relieved, cranioplasty is performed. Although feasibility of the surgery is usually assessed by CT scanning in a supine position, it is sometimes difficult to determine whether the surgery can be performed safely. Although nine patients underwent a decompressive craniectomy during the study period, only six patients could undergo brain CT-first in a supine position and next in a lateral decubitus position with the surgical side upward-before cranioplasty. On CT images, the distance from the midline to the brain surface was measured on the image where brain bulging was maximal, and the bulging was calculated by comparing the image with the distance measured on the contralateral side. In all cases, brain bulging decreased with this change in position. The decrease ranged from 5.5-9.2mm(mean 7.1mm). Patients with brain bulging of 2.8-3.6mm in the lateral decubitus position needed no additional procedure, or only required drainage of a very small amount of cerebrospinal fluid(CSF)from the brain surface. Those with brain bulging of 5.1-12mm showed ventricular dilatation on CT images, and required ventricular puncture or spinal CSF drainage to decrease brain bulging for cranioplasty. We believe that the lateral decubitus position, with the surgical side upward, ameliorates the local brain shift induced by gravity. A lateral position during CT simulates the surgical head position for cranioplasty and can help to assess whether cranioplasty is feasible.

Extradural removal of the anterior clinoid process (ACP) is useful and essential for approaching aneurysmal and tumor lesions in and around the cavernous sinus. A safe, rapid and less invasive technique is beneficial for this basic skull base surgery. We developed a new technique by sharply cutting the ACP together with the part of the sphenoid ridge bone followed by complete replacement. A series of patients with either basilar top or internal carotid artery aneurysms underwent the present technique. After frontotemporal craniotomy, the lateral frontal and anterior middle cranial fossae are exposed extradurally. The bone was cut using a cutting steel burr from the sphenoid ridge to the superior orbital fissure and to the optic canal. By sharply separating the meningo-orbital band between the dura propria and the periorbital fascia, the ACP is exposed. The cutting burr runs underneath the ACP. By leaving a very thin sheet of bone, the entire bone piece was elevated after fracturing the thin bone using a chisel. By severing the carotid ring, the internal carotid artery is freed and mobile either laterally or medially to obtain an ample basal cistern. After operation, the once removed clinoid process is replaced in situ using a titanium plate screw. Extradural en bloc removal and in situ replacement of the ACP can be safely done by this cutting procedure. This can provide a good cosmetic result without causing enophthalmos or transient oculomotor palsy.

A unique transposition technique in microvascular decompression for hemifacial spasm (HFS) was employed in patients with compression by either the peripheral artery or the main trunk of the vertebral artery. Complete transposition that secured free space between the offending artery and the root exit zone (REZ) was accomplished by introducing GORE-TEX tape around the artery and suturing it to the petrous dura. An adequate working space, as if operating in a shallow basin, was essential. Throughout the procedure, it was not necessary to use a brain retractor. Instead, a gentle wrapping retraction technique using a sucker was employed over the brain covered by a sheet of Gelfoam (Pfizer Japan Inc., Tokyo) and cotton. All patients showed complete cure of HFS immediately after surgery with this technique. The difficulty of transposing the vertebral artery can be overcome by well-designed surgical strategy and skillfulness.