OBJECTIVE MRI volumetry could be used as an alternative to invasive tests of shunt function. In this study, the authors aimed to assess the difference in ventricular volume (VV) before and after surgery and at different performance levels (PLs) of the shunt. METHODS This study was a randomized, double-blind trial with a crossover design. The study sample consisted of 36 patients (25 men, 11 women) with a median age of 76 years. All patients had idiopathic normal pressure hydrocephalus (iNPH) and received a Strata shunt at the regional hospital in Östersund, Sweden, with an initial PL of 1.5. Participants underwent MRI with volumetric sequences before surgery and four times postoperatively: at 1 month before randomization to either PL 1.0 (n = 15) or 2.5 (n = 17); at 2 months before crossover to PL 2.5 or 1.0; at 3 months before lowering the PL to 0.5; and finally, at 3 months and 1 day after surgery before resetting the PL to 1.5. VV was measured semiautomatically using quantitative MRI. Both the patient and the examiner of clinical tests and volumetry were blinded to the PL. RESULTS VV changed significantly between the presurgical level (median 129 ml) and the different shunt settings, i.e., PL 1.0 (median 115 ml), 1.5 (median 120 ml), and 2.5 (median 128 ml; p < 0.001). A unidirectional change in VV was observed for all participants between PL 1.0 and PL 2.5 (median 12 ml, range 2.1-40.7 ml, p < 0.001). No significant change was noted in VV after 24 hours at PL 0.5. Eight participants had asymptomatic subdural effusions at PL 1.0. CONCLUSIONS The consistent decrease in VV after shunt surgery and between PL 2.5 and 1.0 supports the idea that MRI volumetry could be a noninvasive method for evaluating shunt function in iNPH, preventing unnecessary shunt revisions. However, further studies on retest variability of VV as well as verification against advanced testing of shunt function are needed before a clinical implementation of this method can be performed. Clinical trial registration no.: NCT04599153 (ClinicalTrials.gov).

中文翻译：

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正常压力脑积水分流调整的体积效应：一项随机、双盲试验。

客观 MRI 容积测定可用作分流功能侵入性测试的替代方法。在这项研究中，作者旨在评估手术前后以及不同分流性能水平 (PL) 下心室容积 (VV) 的差异。方法 本研究是一项采用交叉设计的随机、双盲试验。研究样本包括 36 名患者（25 名男性，11 名女性），中位年龄为 76 岁。所有患者均患有特发性正常压力脑积水 (iNPH)，并在瑞典厄斯特松德地区医院接受了 Strata 分流术，初始 PL 为 1.5。参与者在手术前和术后接受了四次体积序列 MRI：随机分组前 1 个月，PL 1.0 (n = 15) 或 2.5 (n = 17)；交叉至 PL 2.5 或 1.0 前 2 个月；在将 PL 降低至 0.5 之前 3 个月；最后，在手术后 3 个月零 1 天，将 PL 重置为 1.5。使用定量 MRI 半自动测量 VV。患者和临床测试和容量测定的检查者都对 PL 不知情。结果 VV 在术前水平（中位 129 ml）和不同分流设置之间显着变化，即 PL 1.0（中位 115 ml）、1.5（中位 120 ml）和 2.5（中位 128 ml；p < 0.001）。所有参与者在 PL 1.0 和 PL 2.5 之间观察到 VV 的单向变化（中位数 12 ml，范围 2.1-40.7 ml，p < 0.001）。24 小时后，PL 为 0.5 时，VV 没有显着变化。8 名参与者在 PL 1.0 时出现无症状硬膜下积液。结论 分流手术后 VV 持续下降以​​及 PL 2.5 和 1.0 之间支持以下观点：MRI 容积测定可能是评估 iNPH 分流功能的无创方法，防止不必要的分流修正。然而，在临床实施该方法之前，需要对 VV 的重新测试变异性进行进一步研究，并验证分流功能的高级测试。临床试验注册号：NCT04599153 (ClinicalTrials.gov)。