Prediction of functional outcome using the novel asymmetric middle cerebral artery index in cryptogenic stroke patients

Background
Etiology is unknown in approximately one-quarter of stroke patients after evaluation, which is termed cryptogenic stroke (CS). The prognosis of CS patients is largely undetermined. We created a novel index from transcranial Doppler parameters including mean flow velocity (MV) and pulsatility index (PI) and investigated whether the calculation of asymmetry in the novel parameter can predict functional outcomes in CS patients.
Methods
We made the middle cerebral artery (MCA) index (%) as a novel parameter, which was calculated as 100 X (MCA MV + MCA PI X 10) / (MCA MV–MCA PI X 10). The MCA asymmetry index (%) was also calculated as 100 X (|Rt MCA index–Lt MCA index|) / (Rt MCA index + Lt MCA index) / 2. Poor functional outcomes were defined as modified Rankin Scale score (mRS) ≥3 at 3 months after stroke onset.
Results
A total of 377 CS patients were included. Among them, 52 (13.8%) patients had a poor outcome. The overall MCA asymmetry index was two-fold higher in CS patients with a poor outcome (10.26%) compared to those with a good outcome (5.41%, p = 0.002). In multivariable analysis, the overall MCA asymmetry index (OR, 1.054, 95% CI, 1.013–1.096, p = 0.009) and the cutoff value of the overall MCA asymmetry index >9 were associated with poor outcomes at 3 months (OR, 3.737, 95% CI, 1.530–9.128, p = 0.004).
Conclusion
We demonstrated that the novel asymmetric MCA index can predict short-term functional outcomes in CS patients.

### 背景
约四分之一的卒中患者在完成相关评估后仍无法明确病因，此类卒中被称为隐源性卒中（cryptogenic stroke, CS）。隐源性卒中患者的整体预后尚不明确。本研究基于经颅多普勒超声（transcranial Doppler, TCD）参数构建了一项新型指标，纳入平均血流速度（mean flow velocity, MV）与搏动指数（pulsatility index, PI），并探讨该新型指标的不对称性计算是否可预测隐源性卒中患者的功能预后。
### 方法
本研究将大脑中动脉（middle cerebral artery, MCA）指标（%）设为新型参数，其计算公式为100 ×（MCA平均血流速度 + MCA搏动指数 × 10）/（MCA平均血流速度 – MCA搏动指数 × 10）。大脑中动脉不对称指数（%）的计算公式为100 × |右侧大脑中动脉指标 – 左侧大脑中动脉指标| / [（右侧大脑中动脉指标 + 左侧大脑中动脉指标）/ 2]。将卒中发病3个月时的改良Rankin量表（modified Rankin Scale, mRS）评分≥3定义为功能预后不良。
### 结果
本研究共纳入377例隐源性卒中患者，其中52例（13.8%）出现不良预后。预后不良组患者的整体大脑中动脉不对称指数为10.26%，较预后良好组的5.41%升高一倍（p=0.002）。多变量分析显示，整体大脑中动脉不对称指数（优势比[OR]=1.054，95%置信区间[CI]=1.013~1.096，p=0.009）以及整体大脑中动脉不对称指数>9的临界值，均与卒中发病3个月时的不良预后相关（OR=3.737，95%CI=1.530~9.128，p=0.004）。
### 结论
本研究证实，新型大脑中动脉不对称指数可有效预测隐源性卒中患者的短期功能预后。