1. During the operation, the pachymeninx was mended tightly, and the skull base reconstructed.

2. Methods During the operation, the cranial flap were kept floating on the pachymeninx of bone window repaired carefully.

3. Methods During the operation, the cranial flap was floated on the bone window between the pachymeninx and periosteum with bone tip unfixed.

4. The operation mode needs operate with two hands, having the disadvantages of easy brain tissue losing, the irregular cutting edge of the pachymeninx and long time needed.

5. The utility model relates to a safety surgical knife for pachymeninx.