運動ニューロンの系統性変性疾患（Motor Neuron Disease）の2剖検例

MOTOR SYSTEM DISEASE:REPORT OF TWO CASES

I．はじめに

　中枢神経系の変性性萎縮性疾患のなかに原因の明らかでない，一定の機能単位を構成する部位に病変の選択性を示す疾患群がある。これらの疾患群は系統疾患（Systematische Atrophien-Spa—tz, Systemerkrankungen-Spielmeyer）として総括され，その共通の特徴として1）病変過程が基本的に萎縮性病変であること，2）病変過程の進行が緩除で，臨床経過は数年から数10年にわたることがあること，3）病変が一定の機能を営む解剖学的単位，すなわち一定の系統に選択性を示すこと，4）病変部位の対称性，5）病因として内因性因子の潜在の強く疑われることが指摘されている^22）。この種の系統疾患としてPicksche　Atrophie, Huntingtonsche Chorea, Spasti—sche Spinalparalyse, Spinale Muskelatroph—ie, Bulbäre Muskelatrophie, Amyotrophis—che Lateralsklerose, Spinozerebellare Atro—phie a）　Friedreich, b）　Nonne-Pierre-Ma—rie, Spino-olivo-pont-zerebellare Atrophie， Dentatum-Bindearm Atrophie, Neurale Mus—kelatrophie （Hypertrophische Neuritis）があげられている^22）。これらの疾患のうち変性萎縮病変が運動ニューロンに選択性を示す場合はmotor neuron disease, motor system diseaseとして別に総括されている^14）。motor neuron diseaseを含む系統性変性疾患の病因はまだ明らかにされていない。したがつてその分類は主として病変の局在によるものであるが，病変の局在の系統性はがならずしも明瞭ではなく，相互の疾患の間に移行が認められ，また病変過程のFormale Geneseについても意見が分かれている。

Two autopsy cases of motor neuron disease were described. Case 1 was a woman aged 31 with progressive clinical course of 19 mo-nths duration characterized by muscular atro-phy and paralysis of the four limbs. Histopa-thological studies on the nervous system dis-closed an evidence of cellular degeneration in the ventral horn cells of the spinal cord and in the hypoglossal nuclei. A mild degree of myelin sheath degeneration was observed also in the anterolateral columns of the spin-al cord. This case was classified as progres-sive spinal muscular atrophy because of dege-nerative processes in the nervous sytem with selective involvement of the lower motor ne-uron associated with amyotrphy. Case 2 was a man aged 47, who had a progressive clini-cal course of 31 months' duration with chief symptoms of muscular atrophy, paralysis of the extremities and bulbar signs. Histopath-ological picture in the nervous system was characterized by diffuse demyelination of the anterolateral columns of the spinal cord, deg-eneration of the anterior horn cells, involve-ment of tne cranial mortor nuclei and nerves, destruction of extrapyramidal motor nuclei and by cellular degeneration in mild degree of cerebral cortex. This case was considered to be of amyotrophic lateral sclerosis because of combined degeneration of both the upper and lower motor system associated with mus-cular denervation atrophy.

In both cases, the process was essentially degenerative with selective invoivement of the motor neuron system. Topographical stu-dies, however, revealed unusual concommitants, involvement of the upper neuron in the Case 1 and of extrapyramidal motor nuclei in the Case 2. It is considered that the topogra-phical subentities of the motor system disea-se merely represent extremes and are not mutually exclusive. No factors of etiological significance was demonstrated.