Morphological changes of deep neck muscles in Hirayama disease

English Keywords:Hirayama disease(HD)  Cervical paraspinal muscles  Morphometry

English Abstract:

  【Abstract】 Objectives: To clarify the deep neck muscle changes in patients with Hirayama disease, further understand its pathogenesis, and provide possible new ideas for the treatment of Hirayama disease. Methods: Retrospectively analyze the neutral cervical MRI of 38 Hirayama disease patients and 38 healthy sex-age matched people as control group. The anteroposterior and transverse diameters of the spinal cord at the most severe level in patients with Hirayama disease(in control group, spinal cord diameters were measured at C5/6 level) and then calculate the ratio of the anteroposterior and transverse diameters were measured. Also the deep muscles(the flexor deep consists mainly of the longus capis and longus cervicalis, and the extensor deep consists of the multifidus and semisspinalis cervicalis) of C3-7 intervertebral disc and the corresponding vertebral cross-sectional area(CSAs), and calculated the relative cross-sectional area(R-CSA) and the ratio of the cross-sectional area of deep flexors to deep extensors(CSADFs/CSADEs) were measured(The cross-sectional area of the paraspinal muscles was directly proportional to muscle strength, so it could reflect changes in muscle strength). At the same time, the signal values of deep flexors and deep extensors were obtained and the signal/noise ratio(SNR) of the signals of deep flexors and deep extensors was calculated. Finally, R-CSA and CSADFs/CSADEs were compared between the two groups. Results: The spinal cord of Hirayama disease patients was compressed and deformed, and the ratio of the anterior and posterior diameter to the transverse diameter decreased(0.32±0.06 vs 0.53±0.82). Compared with the healthy control group(C3/4, 0.47±0.15; C4/5, 0.29±0.10; C5/6, 0.22±0.07; C6/7, 0.19±0.48), the CSADFs/CSADEs(C3/4, 0.66±0.18; C4/5, 0.48±0.14; C5/6, 0.45±0.22; C6/7, 0.34±0.15) of Hirayama disease patients increased significantly(P＜0.05); the R-CSADFs and SNR of Hirayama disease patients also increased significantly(P＜0.05); while the R-CSADEs decreased significantly(P＜0.05). Conclusions: The imbalance of deep flexor and extensor strength in patients with Hirayama disease may cause repeated excessive flexion of the neck in patients with Hirayama disease, which may compress the spinal cord. Correcting the sagittal imbalance of the cervical spine is a possible idea for the treatment of Hirayama disease.