頭蓋底陷入症および大孔付近の骨異常

Basilar Impression and other Anomalies in the Region of the Foramen Magnum

I．大孔付近の骨異常総論

1．大孔付近の部位的素因について

　大孔付近は，頭部と頸部とのつなぎ目の部分としていろいろな点から異常の起こりやすい条件をそなえている。すなわち，①発生学的には，神経管の閉鎖，後頭骨・脊椎の発生などにさいして，この部には特殊な条件があり（神経管の閉鎖がこの部ではもつともともおくれる，後頭骨，上部頸椎の発生が複雑であるなど^{7）18）36）}）そのため「発生の過誤」がおこりやすい。②発生および生後の発育にあたつて，神経幹の生長速度と頭蓋．脊柱の生長速度との間にずれを生じた場合などに，その「しわよせ」がこの部に集中しやすい。

　19 cases of basilar impression were reported. Associated developmental anomalies in these cases were assimilation of the atlas (17/19 cases), Chiari-Arnold syndrome (12/19) and Klippel-Feil syndrome (10/19).

　The basilar impression is divided into 4 types according to the part of impression of the rim of the foramen magnum, the anterior (2/19 cases), the lateral (6/19), the anterolateral (7/19) and the total (4/19). All these cases underwent suboccipital decompression with laminectomy of C¹, and C²(and C³ occasionally). The results were excellent, 14 cases being completely or nearly completely recovered and 5 cases being markedly improved.

　The etiology, symptom otology- and diagnostics were discussed. The radi ological examinations including craniometric data were described in detail. A new line, "the orbitooccipital line, "which connects the infraorbital point on the film side and the most caudal point of the occipital bone in the lateral view, was proposed.