Interhemispheric hygroma as a predictor of post-traumatic hydrocephalus after decompressive craniectomy: a...

Post-traumatic hydrocephalus (PTH) is a recognized complication following decompressive craniectomy (DC) for traumatic brain injury (TBI). Subdural hygroma has been implicated as a potential risk factor; however, prior studies have been limited by heterogeneous definitions and lack of distinction between hygroma subtypes. The role of interhemispheric hygroma (IHH) as a specific predictor of hydrocephalus remains unclear.

We conducted a systematic review in accordance with PRISMA 2020 guidelines. We searched PubMed (MEDLINE), Cochrane, and Scopus from inception to March 2025. We included studies evaluating hydrocephalus following DC for TBI and reporting data on subdural hygroma. We adopted a phenotype-specific approach, focusing on IHH as the primary exposure and clinically significant hydrocephalus (shunt-dependent or clearly defined clinical hydrocephalus) as the outcome. We assessed study quality using the Newcastle-Ottawa Scale. We performed the meta-analysis using study-level 2 × 2 data, with fixed-effect and random-effects models for primary and sensitivity analyses, respectively.

We included 14 studies comprising 1,621 patients in the qualitative synthesis. We included three studies with comparable definitions in the primary meta-analysis, demonstrating a strong association between IHH and hydrocephalus (pooled OR 6.75, 95% CI 3.4-13.41; I² = 9.8%). Sensitivity analyses incorporating additional heterogeneous studies confirmed the association, although with a lower effect size and increased heterogeneity. Studies relying on radiological definitions alone were excluded from pooled analysis but showed similar trends. Across studies, incidence of hydrocephalus varied widely depending on outcome definitions.

Interhemispheric hygroma is strongly associated with the development of clinically significant hydrocephalus following DC. A phenotype-specific analytical approach reduces heterogeneity and improves interpretability compared with prior studies. Recognition of IHH may facilitate early identification of patients at risk for PTH and support more targeted postoperative monitoring and management strategies.