後頭・頭頂葉梗塞により多彩な視覚異常を呈したpseudoxanthoma elasticumの1例

A CASE OF PSEUDOXANTHOMA ELASTICUM SHOWING VARIOUS HETEROPTICS DUE TO INFARCTION OF RIGHT PARIETO-OCCIPITAL LOBE

　抄録　右後頭・頭頂葉梗塞により多彩な視覚異常を呈した弾力線維性仮性黄色腫の1例を報告した。患者は48歳，男性で，脳血管造影で右内頸動脈閉塞，右後交通動脈の動脈瘤状拡張，右頭頂後頭動脈と鳥距動脈の閉塞を認めた。CTでは右後頭葉に低吸収域を認め，MRIにより右根状回と前襖状回に病巣を明確に描出しえた。左下同名4半盲部に幻視，視野残存部に多彩な錯視，更にpalinopsiaを認めた。Tachisto-scopeで画像が残像として残り，4半盲部に点滅しながら移動した。錯視は梗塞発症後早期より認められたのに対し，幻視は約1カ月後より穂められ，両者は視野欠損の改善とともに周辺部より改善傾向を示した。またフェニトイン投与により幻視は改善したが，錯視は悪化し，両者は発生メカニズムを異にすると思われた。dynamic CTではprimary visual cortexの血流は患側の右では健側に比しむしろ増加しており，視野欠損部の幻視は側副血行路の発達という病理学的修復過程を反映しているものと推察された。これに対し，錯視は障害部位での視覚路の不完全損傷による視覚の不安定性に由来するものと考えられた。

A case of pseudoxanthoma elasticum showing various heteroptics due to infarction of the right parieto-occipital lobe was reported. The patient was 48-year-old male. Angiography revealed an obstruction of the right internal carotid artery,aneurysmal dilation of the right posterior com-municating artery, and obstructions of the right parieto-occipital artery and calcarine artery. A low density area was found in right occipital lobe by CT. MRI clearly indentified lesions in the right cuneus and precuneus. Pseudopsia in the left ho-monymous quadrantanopsia, various types of visual illusion in the remaining visual field, and more-over, palinopsia were existed. Visual illusion was recognized in the early stage after the onset, while the pseudopsia was recognized about one month after the onset. Both abnormalities tended to im-prove from the peripheral region with the im-provement of the defect in the visual field. Admi-nistration of phenytoin resulted in an improve-ment in the pseudopsia but it resulted in an aggra-vation in the visual illusion. Thus, the mechanisms of development of this phenomena were thought to be different from each other. It was found by dynamic CT that the blood flow in the primary visual cortex was rather increased in the affected site in comparison with that in the healthy site. It was speculated that the pseudopsia in the defec-tive region of the visual field reflected a patholo-gical repair process represented by a development of the collateral circulation. On the other hand, the visual illusion was thought to originate from visual unstability due to incomplete damage of the visual pathway at the affected site.