Timing and Outcomes of Cranioplasty After Decompressive Craniectomy: A Systematic Review of Neurological Recovery, Complications, and Predictive Factors.

Background: The optimal timing of cranioplasty (CP) after decompressive craniectomy (DC) remains debated. Early reconstruction may enhance neurological recovery through restoration of cerebral perfusion and cerebrospinal fluid dynamics, yet concerns persist regarding postoperative complications. Objective: To evaluate the impact of early versus delayed cranioplasty on neurological outcomes and postoperative complications in adults following decompressive craniectomy. Methods: A systematic review was conducted in accordance with PRISMA guidelines (PROSPERO ID: CRD420251123808). PubMed, OVID, and Web of Science were searched for studies published between January 2017 and December 2025. Eligible studies compared early and delayed CP in adults and reported neurological outcomes and/or complications. Results: Twenty-one retrospective cohort studies including 8462 patients were analyzed. Neurological improvement was observed in both groups across multiple validated scales (GOSE, GOS, GCS, mRS, BI, FIM, NIHSS, MMSE). Early CP was consistently associated with superior recovery, including higher one-year Barthel Index improvement (74.1% vs. 54.8%), greater FIM gains (7.31% vs. 4.66%), and higher composite recovery rates (95.6% vs. 80.0%). No study demonstrated superior recovery with delayed CP. Infection, hydrocephalus, and seizure rates were comparable between groups. However, hematoma (21% vs. 10.4%) and hygroma (7.49% vs. 4.73%) were more frequent after early CP, although hematoma rates were influenced by a large database study. Bone flap resorption was less frequent with early CP (1.44% vs. 6.26%). Conclusions: Early cranioplasty is associated with improved neurological recovery but carries an increased risk of select complications, particularly hematoma and hygroma, representing a clinically relevant trade-off. Delayed CP does not demonstrate overall superior safety due to higher bone flap resorption. Timing should be individualized, and prospective multicenter studies with standardized definitions are needed.