実験的脳梗塞の経時的変化—CTおよび組織学的検討

SEQUENTIAL CHANGES OF EXPERIMENTAL CEREBRAL INFARCTION:CT AND HISTOLOGICAL STUDY

　抄録　視床梗塞モデル犬を用い，6時間の血流遮断後血流を再開通させることにより作製した出血性梗塞犬について，脳梗塞巣の経時的変化をCT所見と組織像を対比させて検討した。CT所見では低吸収域は2時間目ですでに認められ，以後次第に周囲との境界をはっきりさせつつ6週間目まで観察された。造影剤増強効果は2時間目と，7日から14日目頃までの2度の時期に認められた。組織像では，2時間目では既存の毛細血管や小静脈より赤血球の漏出が見られた。これが，同時期の造影剤増強効果の機序を示唆する所見と考えられた。2日目から5日目までは病巣辺縁部から大食細胞の進出が始まっていた。7日目から14日目頃は，神経細胞，手細血管，小静脈は崩壊消失していたが，病巣辺縁部から中心に向かって新生血管が多数出現しており，幼若な新生血管からの造影剤の漏出がこの時期の造影剤増強効果出現の機序ではないかと考えられた。3週間目頃より病巣辺縁部より，新生血管も崩壊し始め，空胞化が進行して来た。6週間目には中央にわずかな索状物を残して空洞化していた。

Using the canine thalamic infarction model, it was found that hemorrhagic infarction can be pro-duced at a high frequency following recirculation after 6 hours of vascular occlusion. In the current study, sequential changes of histological findings and CT findings in the infarctic foci were inves-tigated.

Low absorption areas in the CT scans were ap-parent already by the 2 hours of recirculation. Thereafter, the boundary with the periphery be-came more distinct and was visible through the 6th week. Contrast enhancement could be seen 2 hours after recirculation and between 7 and 14 days thereafter.

In histological study, leakage of red blood cells from the capillaries and small venules in the focus could be seen 2 hours after recirculation. This finding is thought to indicate that the mechanism of contrast enhancement is extravasation during this period. Macrophages began to infiltrate the focus front the surrounding tissue between the 2nd and 5th day. Between the 7th and 14th day, des-truction of nerve cells and capillaries was seen, together with the formation of small cavities, but many small vessels from the peripheral tissue head-ing toward the focus were regenerated. It is thought likely that the contrast enhancement seen during this period was due to leakage of the con-trast medium from these newly regenerated ves-sels. From around the 3rd week, destruction of the regenerated vessels from the periphery of the focus began and cavity formation progressed. By the 6th week, only a small amount of fibrous neural material remained and the cavity was well-formed.