| Objectives: The objective of the study was to further understanding of the etiology of congenital muscular torticollis by dissceting and finding out the histological characteristics of fetal sternocleidomastoid muscle and to compare fetus SCM with pathological changes of congenital muscular torticollis.Methods: Fifty-eight aborted or induced fetus were collected. According to the gestational age, the fetal specimens were divided into five groups:(1) 18-19 weeks, 4 cases;(2) 20-21 weeks, 15 cases;(3) 22-23 weeks, 10 cases;(4) 24-25 weeks, 22 cases;(5) 26-28 weeks, 7 cases. CMT pathological specimens were harvested from 58 cases under 1 year old in the Shenzhen Children’s Hospital. All cases were confirmed clinically and pathologically. Fetal sternocleidomastoid, trapezius muscle, rectus femoris and CMT were anatomized and collected. These specimens were observed under the hematoxylin and eosin(HE) staining, Masson staining and the immunohistochemical method(Max Vision) of CD45 and were compared between SCM and trapezius muscle, rectus femoris and CMT.Results: Of 58 fetuses, the bilateral size of SCM in 53 cases showed basically symmetrical, five out of 58 fetuses had bilateral SCM development asymmetry, the abnormality rate was 8.6%. One case showed the bilateral SCM asymmetrically developed, and one case mastoid head was swollen on the right side, three cases were found asymmetric development of bilateral mastoid head. The bilateral size of trapezius muscle and the rectus femoris specimen in 58 fetus showed no abnormalities. The fetus SCM muscle fibers showed development complete and no obvious SCM muscle sheath was anatomized and discovered while gestational age was more than 18 weeks.Sternocleidomastoid muscle showed sparse fibers, poor continuity, disorganized muscle cell, large with lightly stained nucleus than trapezius and rectus femoris in HE and Masson staining. A portion of the muscle fibers had more naive mesenchymal in sternocleidomastoid then in trapezius and rectus femoris which stained blue in Masson staining. As gestational age increases, SCM, trapezius and rectus femoris development growed gradually, but the development of SCM was slower than the trapezius and rectus femoris. HE and Masson staining in CMT found a large proliferation of fibrous connective tissue, varying sizes and dyeing of muscle cells. Some muscle cells showed atrophy and degeneration. Diffusing proliferation was found in fibrosis of CMT in which normal muscle bundle structure was destroyed. Immunohistochemistrical CD45 expression in SCM, trapezius and rectus femoris had significantly differences among different fetal age groups. In the same fetus, the right side of SCM had obvious expression then left SCM. Among SCM, trapezius, rectus femoris and CMT, positive cell number varied. CD45 positive cells had higher numbers in SCM and CMT than the trapezius, rectus femoris. No different CD45 positive cell was found bewteen fetus SCM and CMT.Conclusion:(1) By studying the fetus SCM, trapezius and rectus femoris, certain percentage of fetal development asymmetry and dysplasia are found on the SCM, the abnormal ratio is 8.6% among 58 cases.(2) Histologically, it is found out more stroma, immature, retarded muscle fibers and more interstitial component in SCM than in trapezius and rectus in the same fetus. Slow maturation of SCM is found when different periods of fetal are compared.(3) Comparative study of CD45 shows more CD45 positive cells in interstitial of SCM than the trapezius muscle and the rectus femoris. This finding suggests that the origin of the embryonic development of SCM is special. CD45-positive cells are found in CMT lesions, which suggests abnormal differentiation and maturation in CMT interstitial. |
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