Schmidt R, Voit T
Department of Pediatrics, Heinrich-Heine University Düsseldorf, Germany.
Neuropediatrics. 1993 Feb;24(1):36-42. doi: 10.1055/s-2008-1071510.
Using real-time ultrasound imaging normal values were obtained for quadriceps muscle thickness and subcutaneous tissue depth in the first year of life from 120 normal infants. These values were corrected for weight and height by introduction of a "correcting factor". In addition, a "modified muscle index" was calculated by multiplying the ratio of muscle to subcutaneous tissue thickness with the correcting factor and showed a steady increase from birth (mean 2.1) to the end of the first year (mean 4.8). The study of 12 patients with spinal muscular atrophy type I (SMA I) revealed that 9 out of 12 SMA I patients failed to reach the 3rd percentile for the muscle to subcutaneous tissue ratio and 10 out of 12 were well below the 3rd percentile for the modified muscle index due to their muscle atrophy. Only the two youngest SMA I patients aged 4 and 6 weeks reached values on the 3rd percentile. In contrast, 10 patients with myopathy and one patient with holoprosencephaly showed values within the normal percentiles even in the presence of severe clinical muscle weakness and signs of atrophy on muscle histology. In the differential diagnosis of early onset myopathy, atrophy of the quadriceps muscle during the first months of life in the absence of markedly increased echodensity seems to be a pathognomonic finding for SMA.
通过实时超声成像，获取了120名正常婴儿出生后第一年股四头肌厚度和皮下组织深度的正常值。通过引入“校正因子”对这些值进行体重和身高校正。此外，通过将肌肉与皮下组织厚度的比值乘以校正因子计算出“改良肌肉指数”，该指数从出生时（平均2.1）到第一年末（平均4.8）呈稳步上升趋势。对12例I型脊髓性肌萎缩症（SMA I）患者的研究表明，12例SMA I患者中有9例肌肉与皮下组织比值未达到第3百分位数，12例中有10例因肌肉萎缩，改良肌肉指数远低于第3百分位数。只有两名最年幼的SMA I患者，年龄分别为4周和6周，达到了第3百分位数的值。相比之下，10例肌病患者和1例全前脑畸形患者即使存在严重的临床肌肉无力和肌肉组织学萎缩迹象，其值仍在正常百分位数范围内。在早发性肌病的鉴别诊断中，出生后最初几个月股四头肌萎缩且回声密度无明显增加似乎是SMA的一个特征性表现。
