One of the major concerns about AC, compared to DC, is that it does not provide enough space to allow for brain expansion and subsequent reduction in intracranial pressure. Previously, studies had shown that after a DC the brain herniation is only a few mm, in most cases within 5 mm 8, 9Also, our study data demonstrate a more substantial increase in brain volume in patients undergoing augmentative craniotomy (AC) than those undergoing decompressive craniotomy (DC). This suggests that AC is effective in managing brain swelling and providing adequate decompression.
The larger volume increase observed post-AC could be attributed to several factors 10. One key factor is the reduced elastic tension exerted by the soft tissues (skin and temporalis muscle) on the dura mater in AC. The elevation of the bone flap in AC reduces this tension, allowing for greater brain expansion and decompression. Additionally, the elevated bone in AC may exert a hemostatic effect by compressing the soft tissues, which helps mitigate the formation of epidural hematomas commonly seen in DC 11. This hemostatic effect further enhances the decompressive efficacy of AC by maintaining clearer surgical fields and reducing post-operative complications.
The significant increase in brain volume post-operatively in both groups confirms the effectiveness of surgical decompression in managing cerebral edema. However, the greater volume increase observed in the AC group (100 ± 51 mm³) compared to the DC group (72 ± 51 mm³) suggests a superior capacity of AC to accommodate brain swelling. This is a crucial finding as the ability to allow for greater brain expansion without compromising neurological function can be directly linked to improved patient outcomes.
The impact on midline displacement further supports this observation. Both techniques effectively reduced the midline displacement. Postoperative brain shift was found to be lower in the group undergoing AC than in patients undergoing DC, although not statistically significant. This finding supports that this technique has at least similar decompressive capacity as DC.
The superior performance of AC can be attributed to several biomechanical and physiological factors. One factor could be the reduced soft tissue tension. One of the key advantages of AC is the reduced elastic tension exerted by the soft tissues (skin and temporalis muscle) on the dura mater. In DC, the dura is directly exposed and subject to the pressure from the surrounding soft tissues, which can limit the extent of brain expansion. In contrast, AC involves the elevation of the bone flap, which creates a buffer zone that minimizes the compressive forces from the soft tissues, allowing for greater decompression. Another advantageous factor could be the hemostatic effect of elevated bone flap. The elevated bone flap in AC provides a hemostatic effect by compressing the soft tissues, which can help prevent the formation of epidural hematomas. Epidural hematomas are a common complication in DC due to extensive manipulation and exposure of the dura and surrounding tissues and reduce the volume available for brain expansion 12. By minimizing the risk of hematoma formation, AC ensures a cleaner surgical field and reduces the potential for post-operative complications, contributing to better overall outcomes. Finally the additional space created by the elevated bone flap in AC may facilitate better cerebral perfusion by reducing intracranial pressure more effectively. Improved perfusion can aid in the recovery of damaged brain tissue and enhance neurological function, which is critical in the acute management of traumatic brain injury and malignant middle cerebral artery ischemia 13.
The findings from this study have important clinical implications for the management of intracranial hypertension. AC should be considered a viable and potentially superior alternative to DC, particularly in cases where maximal decompression is essential. The enhanced brain volume accommodation and reduced risk of complications associated with AC make it an attractive option for neurosurgeons. Future research should focus on long-term outcomes of patients undergoing AC versus DC. While the immediate post-operative period is crucial for managing acute brain swelling, understanding the long-term neurological and functional outcomes will provide a more comprehensive assessment of the benefits of AC 14. Additionally, studies exploring the optimal flap elevation distance and techniques for minimizing soft tissue tension could further refine the AC procedure and enhance its efficacy. Investigating the molecular and cellular mechanisms underlying the differential responses to DC and AC may also yield valuable insights. Understanding how these surgical techniques influence cerebral perfusion, inflammation, and tissue repair could inform the development of adjunctive therapies to improve patient outcomes.