部分二重脊髓和脊髓结构乳生

PARTIAL DIPLOMYELIA AND MYELODYSPLASIA

本文報告一例部分的二重脊髓和脊髓結構亂生。一個55天的女嬰,枕骨局部缺損、小腦腦膜膨出、側腦室和第3腦室擴張積水,延髓、脊髓頸部和胸部上段的背部有狹長的空洞,間與中央管相連。胸髓中段比較正常。中段以下和腰髓上端,中央管高度擴張積水。在第2腰節至第1骶節,脊髓背部出現畸增的後角,中央管也見歧分,形成二重脊髓。在第3腰節和第1骶節,左右二半有2次完全分立,中間一度長合。分立時左右二半間有纖維組織和血管侵入。重出的脊髓左右不全對稱。在腰髓下段内部結構亂生,背部一度出現5個畸坩後角。第1骶節以下歧出的脊髓又行併合,左右也不對稱,左側較大。2個中央管伸至骶髓下端。在重出部分的附近有異位的感覺細胞,它們的纖維似進入畸增的後角。二重脊髓和脊髓結構亂生可由於神經管閉合延綏,左右神經襞背緣支離,向前迴捲,接合底板。脊髓重出和亂生的形態取决於二侧神經襞支離的程度、迴捲的深淺、各部生長的快慢,以及結締組織的侵入的方式。左右的分立可以完全或不完全;歧生的結構可以對稱或不對稱。畸增的部分各成單位,在神經襞上似屬一體。

A case of partial diplomyelia and myelodysplasia involving the lower part of the spinal cord is reported.The patient,a 55-day old baby girl,was born with a defect on the occipital bone.She had myelomeningocele,hydrocephalus,syringobulbia and syringomyelia of the cervical and thoracic segments.The mid-thoracic region was comparatively normal;below that level the central canal was markedly dilated(hydromyelia).Complete redu-plication of the spinal cord occurred twice at levels of the third lumbar and the first sacral segment with connective tissues and blood vessels in between.The two cords were not symmetrical,especially in their dorsal half.As many as five supernumerary posterior horns were found on a single level(extreme myelodysplsia).The lower sacral cord appeared essentially normal;nevertheless,its two halves were asymmetrical,the left side being larger.Besides,it had two central canals extending to its lower end.As to the cause of diplomyelia and myelodysplasia,several factors are involved.The closure of the neural tube may be delayed arid the edges of the neural folds may be rugged.The folds may roll inwards approximating each other and become fused with the floor plate,giving rise to two medul-lary tubes which may be separate or fused,symmetrical or asymmetrical.The pattern and degree of the anomalies were conditioned by the depth of infolding and degree of ruggedness of the folds,the manner of their fusion and the extent of mesenchyme invasion into the tube.The supernumerary dorsal horns have generally associated aberrant sensory cells in their vicinity.These abnormal structures apparently develop from a unit in the neural fold.