Capsule formation can make secondary reconstruction of the dura mater unnecessary after cranial infection.

PURPOSE: Defects of the dura mater caused by surgical intervention are often reconstructed using artificial substitutes such as polytetrafluoroethylene membrane (Gore-Tex in commercial name). In cases where secondary infection develops after the initial operation, the artificial substitute used in the primary surgery needs to be removed, and the cranial defect should be covered with tissues abundant in blood supply. The present study discusses the necessity of secondary reconstruction of the dural defect in the recovery operation. METHODS: A retrospective study was conducted on 12 patients in whom artificial substitute was exposed because of necrosis of the overlying tissues due to infection or radiation. In recovery operations, the artificial substitute was removed, and the conditions of the underlying defects were evaluated. RESULTS: In all cases, capsule formation had developed to cover dural defects underneath the infected artificial substitutes. The capsules were transparent and watertight, presenting no leakage of cerebrospinal fluid. After coverage of the defect regions using free-flap transfer, no patient developed postoperative complications in follow-up periods of at least 6 months. CONCLUSIONS: Capsule formation occurs under artificial substitutes after replacement of the dura mater. Because the capsules retain the cerebrospinal fluid, replacement of the artificial materials is unnecessary in the secondary operation.