Short-Term Changes in Lumbar Cerebrospinal Fluid Opening Pressure After Cranioplasty: A Retrospective Observational Study

Objective: To characterize short-term changes in lumbar cerebrospinal fluid (CSF) opening pressure after cranioplasty in patients with cranial defects and to explore factors associated with postoperative pressure reduction. Methods: This retrospective observational study included 55 adult patients who underwent cranioplasty after decompressive craniectomy. Lumbar CSF opening pressure was measured within 1 week before and within 1 week after cranioplasty. The primary outcome was the postoperative change in lumbar CSF opening pressure, defined as postoperative pressure minus preoperative pressure. Pressure changes were also classified as increased (≥20 mm H 2 O), stable (-20 to <20 mm H 2 O), or decreased (≤-20 mm H 2 O). Paired comparisons, nonparametric group comparisons, correlation analysis, and exploratory logistic regression were performed. Results: The cohort included 37 men and 18 women, with a median age of 57.0 years. Traumatic brain injury was the primary disease in 44 patients, and 40 patients had hydrocephalus. Overall, postoperative lumbar CSF opening pressure was higher than the preoperative value [median: 140.0 versus 120.0 mm H 2 O; median change: 30.0 mm H 2 O (-20.0 to 72.5); Wilcoxon signed-rank test, P =0.002]. Pressure increased in 31 patients (56.4%), remained stable in 9 (16.4%), and decreased in 15 (27.3%). Higher preoperative pressure was associated with a greater tendency toward postoperative pressure reduction (Spearman rho=-0.571, P <0.001). In an exploratory logistic model, older age and higher preoperative pressure were associated with postoperative pressure decrease. Conclusions: Cranioplasty was associated with heterogeneous short-term changes in lumbar CSF opening pressure, with an overall increase but a distinct subgroup showing postoperative pressure reduction. Reassessment of CSF pressure after cranioplasty may be useful when staged CSF diversion is considered. These findings should be interpreted cautiously because lumbar opening pressure is not equivalent to continuous intracranial pressure monitoring.