神経・筋疾患における四肢軟部組織撮影—その診断的意義について

SOFT TISSUE RADIOGRAPHY OF EXTREMITIES IN NEUROMUSCULAR DISEASE : IMPORTANCE OF ITS DIAGNOSTIC VALUE

I．はじめに

　四肢軟部組織撮影法は神経・筋疾患において，これまで散発的に行なわれたのみで，神経学的立場に基づく体系的・レ線学的研究は行なわれていない。しかし本法は補助検査法として，筋電図や筋生検などには求められない利点，すなわち先ず痛みや組織に対する侵襲を必要としない点でこれらとは異なった利点をもち，皮下脂肪の多寡に拘わらず，萎縮筋の全貌が把握でき，経過を追ってくり返し検討できる可能性を有する。そこで筆者は本法を系統的に筋萎縮性諸疾患について観察し，その診断的意義について検討を加えた。

Most neuromuscular disease displays various grades of decrease or increase of muscle mass with fatty infiltrations. In neuromuscular disease, soft tissue radiography of extremities has not been so frequently used as mammography. Since absorption coefficients for X-ray of muscle and fat tissue are very close with very slight difference, technical difficalties has been the reason.

Two hundreds and eighty-one cases reported in this paper are consisted of 82 cases of muscle dis-ease, 60 cases of motor neuron disease, 108 cases of peripheral and central nervous system disease,and 31 cases of related disorders. Fifty-three cases are followed-up by repeated examination of various intervals.

Radiological findings are classified into four types ; normal, atrophic, hypertrophic and malnutritional. In atrophic muscle, a distinct variation of radio-lucent shadows of intermuscular and interstitial fat have been observed as fatty striations contrasted to muscle fibers within muscle substance. In muscles, radiological details of abnormal fatty infiltrations may vary considerably according to the pathological nature of muscle affection, atrophic or hypertrophic, myopathic or neuropathic.

In myopathic atrophic muscle, muscle mass is reduced with extensive fine fatty striations. These striations may gather to form some irregular and intensive fatty infiltrative area. These findings are different in grade at various parts so that radio-logical pictures are not always symmetric. True or pseudo- hypertrophic muscle findings are often observed in some muscles or muscle groups. In neuropathic atrophic muscle, muscle mass is reduced as well as myopathic atrophic muscle. But these fatty striations are shorter and wider than those in myopathic atrophic muscle. Compensatory hypertrophic muscle findings are observed occasion-ally but less and milder than these of myopathic muscular atrophy. In malnutritional muscle, both muscle mass and subcutaneous fat are reduced with-out fatty striations within muscle substance.

In contrast to these atrophic muscles, true hyper-tropic muscle as in myotonia congenita reveals bulky muscle mass and fine fatty striations are usually reduced. Pseudohypertrophic muscle is normal in size but fine fatty striations are increased moderately in number. In the third type as ob-servable in some congenital myopathy, muscle mass and fatty striations are more increased than others. These radiological findings are discussed in relation to clinical and neurological considerations.

From these results, soft tissue radiography of extremities is experienced useful as diagnostic aid for neuromuscular diseases. It provides insight into the gross appearance of muscle and fat in atrophic or hypertrophic muscles and also the ex-tent and progression of the disease process when repeatedly applied.