痙縮の定義をめぐる混乱

Definition of Spasticity

要旨　痙縮の定義が混乱している．そこで，Lance，島村，田中の定義など，和文文献で多く引用されている定義の相違点を分析した．混乱の要因として，相動性および緊張性伸張反射の区別，静止状態での持続的筋伸張による反射の解釈，rigidityとrigidospasticityの語法，折りたたみナイフ現象の解釈を挙げた．それらの分析を通じ，①腱反射亢進のみでは痙縮とはいえない．②相動性と緊張性の伸張反射は混在し，明確には分離できない．③痙縮筋の長さによっては，動きを伴わぬ持続的伸張でも反射が生じうる．④重度痙縮をrigidospasticityと称するのは一般的な語法とは言い難い．⑤折りたたみナイフ現象は痙縮とは異なる現象であると考察した．以上を踏まえ，Lanceに準じた私案を示した．痙縮とは，上位運動ニューロン症候群の一要素で，伸張反射増強の結果として腱反射亢進を伴って生じる，他動伸張時の速度依存性筋緊張亢進である．

Although the term “spasticity” refers to one of the most important concepts in physical medicine and rehabilitation, it is inconsistently defined, particularly in the Japanese literature.

Here, I have presented several definitions widely used throughout Japan and discussed differences among those proposed by Lance, Shimamura, and Tanaka. The use of the phrase “phasic and tonic stretch reflexes” and the meaning of “rigidity” were indicated to cause confusion regarding the definition.

Exaggerated tendon jerks without a reflex response during a continuous muscle stretch should not be included under spasticity. However, if tendon jerks are exaggerated, the increased stretch reflexes without muscle (or joint) movement should be termed “spasticity” rather than “rigidity.” Although some researchers use the term “rigidospasticity” to express severe spasticity, it differs from the original meaning.

According to the discussion, I agree with the definition proposed by Lance：“Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as one component of the upper motor neuron syndrome.” However, it is a mysterious phenomenon that depends not only on velocity but also on muscle length. Further review of its definition is required.