AIM To define the longitudinal trajectory of gastrocnemius muscle growth in 6- to 36-month-old children with and without spastic cerebral palsy (SCP) and to compare trajectories by levels of gross motor function (Gross Motor Function Classification System, GMFCS) and presumed brain-lesion timing. METHOD Twenty typically developing children and 24 children with SCP (GMFCS levels I-II/III-IV = 15/9), were included (28/16 females/males; mean age at first scan 15.4 months [standard deviation 4.93, range 6.24-23.8]). Three-dimensional freehand ultrasound was used to repeatedly assess muscle volume, length, and cross-sectional area (CSA), resulting in 138 assessments (mean interval 7.9 months). Brain lesion timing was evaluated with magnetic resonance imaging classification. Linear mixed-effects models defined growth rates, adjusted for GMFCS levels and presumed brain-lesion timing. RESULTS At age 12 months, children with SCP showed smaller morphological muscle size than typically developing children (5.8 mL vs 9.8 mL, p < 0.001), while subsequently no differences in muscle growth were found between children with and without SCP (muscle volume: 0.65 mL/month vs 0.74 mL/month). However, muscle volume and CSA growth rates were lower in children classified in GMFCS levels III and IV than typically developing children and those classified in GMFCS levels I and II, with differences ranging from -56% to -70% (p < 0.001). INTERPRETATION Muscle growth is already hampered during infancy in SCP. Muscle size growth further reduces with decreasing functional levels, independently from the brain lesion. Early monitoring of muscle growth combined with early intervention is needed.

中文翻译：

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生命第一年内侧腓肠肌生长的纵向轨迹。

目的 定义患有和不患有痉挛性脑瘫 (SCP) 的 6 至 36 个月大儿童腓肠肌生长的纵向轨迹，并根据粗大运动功能水平（粗大运动功能分类系统，GMFCS）和推测的水平比较轨迹脑损伤时间。方法 纳入 20 名正常发育儿童和 24 名 SCP 儿童（GMFCS 级别 I-II/III-IV = 15/9）（28/16 女性/男性；首次扫描平均年龄 15.4 个月 [标准差 4.93，范围 6.24] -23.8]）。使用三维徒手超声重复评估肌肉体积、长度和横截面积 (CSA)，共进行 138 次评估（平均间隔 7.9 个月）。通过磁共振成像分类评估脑损伤时间。线性混合效应模型定义了生长速率，并根据 GMFCS 水平和推测的脑损伤时间进行了调整。结果 在 12 个月大时，患有 SCP 的儿童表现出比正常发育儿童更小的形态肌肉尺寸（5.8 mL vs 9.8 mL，p < 0.001），而随后在患有和不患有 SCP 的儿童之间没有发现肌肉生长差异（肌肉体积：0.65毫升/月 vs 0.74 毫升/月）。然而，GMFCS III 级和 IV 级儿童的肌肉体积和 CSA 生长率低于正常发育儿童以及 GMFCS I 级和 II 级儿童，差异范围为 -56% 至 -70% (p < 0.001)。解释 SCP 的婴儿期肌肉生长就已经受到阻碍。随着功能水平的降低，肌肉尺寸的增长进一步减少，与脑部病变无关。需要早期监测肌肉生长并结合早期干预。