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Takao Watanabe, Yoichi Katayama, Takao Fukushima and Tatsuro Kawamata

Object

The retrosigmoid intradural suprameatal approach with the patient in a semisitting position is an effective alternative to transpetrosal approaches for the treatment of petroclival meningiomas. The authors have made a simple modification to the retrosigmoid intradural suprameatal approach by using the lateral oblique position and preferentially dividing the tentorium with limited drilling of the suprameatal bone, which is termed the “lateral supracerebellar transtentorial approach.”

Methods

Twenty-six patients with petroclival meningiomas surgically treated via the lateral supracerebellar transtentorial approach were analyzed. All tumors had most of their bulk in the posterior fossa with some degree of extension into the middle fossa and/or Meckel cave. The patient is placed in the lateral oblique position, and a standard retrosigmoid craniotomy is performed. The tentorium medial to the trigeminal nerve is incised toward the free edge, which improves exposure to the petroclival region without extensive resection of the suprameatal petrous bone.

Results

Gross-total resection was achieved in 11 patients (42%). Ten patients (38%) underwent subtotal resection, and 5 patients (19%) underwent partial resection. There was no incidence of operative death, and the postoperative permanent morbidity rate was 15%. All patients except one did well postoperatively and were independent at the time of their last follow-up examinations.

Conclusions

The lateral supracerebellar transtentorial approach provides the simplest and safest access to the petroclival region. It offers an advantageous approach to petroclival meningiomas exclusively located in the posterior fossa with minimal extension into the Meckel cave and middle fossa.

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Masaru Inoue, Masaaki Fukushima, Kenji Tsutsumi, Shobu Shibata, Kazuo Mori and Takao Setoguchi

✓ The underlying mechanisms that lead to brain edema following ischemic insult have been subject to much debate. In this study, experimental cerebral infarction was produced in 25 dogs by injecting 1 or 2 silicone rubber cylinders through the cervical internal carotid artery. The animals were sacrificed 24 hours after embolization. Freeze-fracture studies were conducted on the plasma membrane of the capillary endothelium from 15 control and 25 ischemic dogs. No definite findings of tight junction opening were made in the ischemic preparations. Pinocytotic vesicles were seen as concave areas on the protoplasmic face (PF) of the plasma membrane and as protrusions on the extracellular face (EF). The average pinocytotic vesicle count per square micron was increased in ischemic animals. On the luminal side, it reached 22.0 ± 1.2/sq µ in the 50 PF samples and 29.5 ± 1.3/sq µ in the 50 EF samples in the experimental preparations, as compared to 7.2 ± 0.5 sq µ in the 50 PF samples and 9.0 ± 0.6 sq µ in the 50 EF samples in normal cortex. The average area of the vesicles was also enlarged in experimental animals: 4990.7 ± 798 sq nm in the 50 PF samples and 4762.8 ± 878 sq nm in the 50 EF samples, as compared to 3567.7 ± 570 sq nm in the 50 PF samples and 3404.5 ± 573 sq nm in the 50 EF samples in normal cortex (p > 0.01). These results indicate that transcellular transportation by pinocytotic vesicles plays an important role in the increase of capillary permeability observed in an ischemic model.