Initial intraventricular involvement and early intracerebral hematoma retraction: The "ventricular washout".

Introduction: Intraventricular hematoma (IVH) occurs in approximately 40% of acute intracerebral hemorrhage (ICH) patients and is significantly associated with worse clinical outcomes. According to cerebrospinal fluid dynamics, some blood within the ventricles may circulate through the subarachnoid spaces, leading to its apparent "disappearance" on follow-up imaging. We aim to investigate the association between initial IVH involvement and significant early ICH retraction at follow-up imaging.

Methods: Data are from the MCAHP (Multiphase CT Angiography Hematoma Prediction) Study, which included consecutive patients with acute ICH investigated with multimodal CT imaging. Patients who underwent surgery before follow-up imaging were excluded. IVH severity was assessed using the IVH score. The primary outcome was significant early ICH retraction, defined as volume decrease (⩾3 ml or ⩾15%) between the initial and follow-up scans. Secondary outcomes included early absolute and relative ICH decrease. Associations between outcomes and initial IVH involvement or IVH score were assessed with logistic regression adjusted for age, baseline NIHSS, initial ICH volume, and onset-to-CT time.

Results: Overall, 177 ICH patients were included. The median age was 71 years (IQR = 59-80), 71 (40.1%) patients were female, and 64 (36.2%) presented with initial IVH involvement. Patients with initial IVH, compared to those without, had a larger initial ICH volume (28.5 ml [IQR = 12.7-52.5] vs. 18.9 ml [IQR = 8.1-30.6], p < 0.001) and different ICH location (deep = 54.7% vs 47.8%; lobar = 35.9% vs 46.0%; infratentorial = 7.3% vs 6.2%; p < 0.001). Early ICH retraction was observed in 33 (18.6%) patients: 21 (32.8%) with initial IVH and 10 (10.6%) without initial IVH. There was a significant association between early ICH retraction and initial IVH involvement (adjusted odds ratio [aOR] 4.02 [95% CI = 1.72-9.41]) and IVH score (aOR 1.14 [95% CI = 1.05-1.23] per 1-point increase). Similar results were observed for secondary outcomes.

Conclusion: Initial IVH involvement is associated with early ICH retraction - "intraventricular washout." This might result in an underestimation of hematoma expansion occurrence and severity in these patients, with potential implications when evaluating the predictive performance of hematoma expansion markers/scores and the radiological efficacy of hemostatic treatments.