Osseous changes in myopathy.

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The skeletal changes observed on radiographic examination in 38 cases of progressive muscular dystrophy (22 Duchenne type, 8 facioscapulohumeral, 8 juvenile), 17 cases of dystrophia myotonica and 6 of myotonia congenita are reported and are related to the findings of other authors. Constant findings in early cases of muscular dystrophy included narrowing of the shafts and rarefaction of the ends of long bones, impaired development of flat bones, and coxa valga. At a later stage of the disease, scoliosis, widespread decalcification with disorganisation of cancellous structure and loss of the lines of force were noted and sometimes progressed to gross distortion and disorganisation of the skeletal system. The severity of the changes depended upon the age of onset and the rate of progress of the disease. Similar appearances were noted in the wasted limbs of four patients who had suffered from poliomyelitis at an early age and in one case of dermatomyositis. It is concluded that the osseous changes in muscular dystrophy are not due to an associated genetic factor or to a “progressive osteomyopathy”. They can be entirely related to disuse, to the absence of the stresses and strains imposed upon the bones by muscular attachments in the normal individual, and to the development of abnormal postures of the body and extremeties as a result of muscular weakness and/or contractures. In the cases of dystrophia myotonica, bone changes were confined to the skull. The dimensions of the sella turcica and the thickness of the skull vault in these cases were compared statistically with those in 60 normal control subjects of comparable age and sex. The sella turcica was found to be significantly smaller and the skull vault significantly thicker in the dystrophic individuals. These changes became progressively more marked with age and increased duration of the disease. The measurements in six cases of myotonia congenita and in six unaffected relatives of myotonic individuals did not differ significantly from those in the normals on the one hand or from those in dystrophic patients on the other, but all six cases of myotonia congenita were comparatively young. Cranial hyperostoses, bridging of the sella turcica and intracranial calcification did not occur more often in the dystrophic cases than in the controls. The paranasal sinuses were large and the jaw was prognathous in two cases, but again it was not possible to say that these features were significantly more common in the patients. In confirmation of the work of other authors it can be said that reduction in size of the sella turcica and increase in thickness of the skull vault are constant features in cases of dystrophia myotonica. Cranial hyperostosis and some of the other features previously described may be due to a different gene, associated by chance in certain dystrophic families.