PURPOSE Patients with Hirayama disease (HD) present with a larger range of neck flexion and show signs of cervical spine instability. Cervical spine stability largely relies on cervical spine muscles. The purpose of this study was to compare the cross-sectional areas (CSAs) of cervical spine muscles between patients with HD and healthy controls, providing some insights into whether there is cervical spine muscle weakness and incongruence in HD patients. METHODS In this retrospective study, cervical spine muscles CSAs of 44 HD patients, as well as that of 44 age- and sex-matched healthy counterparts, were measured on the T2-weighted axial MR images. The ratios of cervical spine muscles CSA to the corresponding vertebral body areas, defined as R-CSAs, and the flexor/extensor CSA ratios were computed and compared between two groups. RESULTS Compared with healthy counterparts, R-CSAs of total cervical spine muscles, total extensors, superficial extensors, and deep flexors were significantly lower in HD patients. HD patients also demonstrated a significantly greater superficial flexor/superficial extensor CSA ratio than the healthy counterparts, indicating a mismatch between superficial flexors CSA and superficial extensors CSA in HD patients. CONCLUSIONS In this pioneering study, HD patients had decreased size in most cervical spine muscles and a mismatch between CSAs of superficial flexor and that of superficial extensors. These results indicate generalized weakness and incongruence of cervical spine muscles, which may predispose cervical spine of HD patients to a less stable situation. These slides can be retrieved under Electronic Supplementary Material.

中文翻译：

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平山病患者颈椎肌无力吗？MRI上有关肌肉横截面积的形态学研究。

目的平山病（HD）患者的颈部屈曲范围更大，并显示出颈椎不稳的迹象。颈椎的稳定性在很大程度上取决于颈椎肌肉。这项研究的目的是比较HD患者和健康对照者的颈椎肌肉横截面积（CSA），从而为HD患者是否存在颈椎肌无力和不一致提供一些见识。方法在这项回顾性研究中，对44例HD患者以及44例年龄和性别相匹配的健康人群的颈椎CSA进行了T2加权轴向MR图像测量。计算两组颈椎肌肉CSA与相应椎体区域的比率，即R-CSAs，然后计算屈肌/伸肌CSA比率。结果与健康人相比，HD患者的总颈椎肌肉，总伸肌，浅伸肌和深屈肌的R-CSAs明显降低。HD患者还表现出比健康人明显更高的浅屈肌/浅伸肌CSA比率，表明HD患者中浅屈肌CSA和浅伸肌CSA之间不匹配。结论在这项开创性研究中，HD患者的大多数颈椎肌肉尺寸减小，浅表屈肌和浅表伸肌CSA不匹配。这些结果表明颈椎肌肉普遍无力和不一致，这可能使HD患者的颈椎处于不稳定状态。这些幻灯片可以在电子补充材料下找到。