Iotrolanによる脳症の1例

A case of Iotrolan encephalophathy

I．はじめに

　ダイマー型非イオン性造影剤であるIotrolan（イソビスト^®）は，現在，脳室・脳槽・脊髄造影に広く用いられている．従来使用されたモノマー型非イオン性造影剤のMetrizamide（アミパーク^®）の髄腔内投与においては，重篤な副作用としての脳症の発生がしばしば報告されていた^{1,2,5,6,9,11,12,14）}．これに対し，Iotrolanは，種々の点に改良が加えられ，大幅に安全性が向上している．脳症や髄膜炎の発生は極めて稀であり，文献的にわずかに2例の報告をみるにすぎない^10,13）．

　今回われわれは，Iotrolanによるシャント造影施行同日夕より発熱，意識障害などを来たし，Iotrolan脳症と診断した例を経験した．加療により比較的急速に軽快した．文献的考察を含め，報告する．

A case of Iotrolan encephalopathy is reported.

A66-year-old woman, suffering from subarachnoid hemorrhage, was admitted to our department on Janu-ary 17th, 1995. After an operation for aneurysmal clipp-ing and ventriculo-peritoneal shunt, she was discharged with no neurological deficiency. CT scan revealed ven-tricular enlargement and slight periventricular lucency.

She was re-admitted on January 4th, 1996. She was suffering from nausea, vomiting, right hemiparesis, right hemi-hypesthesia and disturbance of conscious-ness. CT scan demonstrated right thalamic bleeding and bilateral ventricular hemorrhage. Further ventricu-lar enlargement was also revealed. With medical treat-ment, her symptoms were relieved gradually. But dis-orientation and memory disturbance continued. Shuntography with Iotrolan was performed on February 2nd, 1996. The ventriculo-peritoneal shunt was demonstrated to be occluded on the abdominal side. The volume of Iotrolan used was about 8cc. She became very restless on the night of the ex-amination. Her temperature was up to 38. CT on February 4th demonstrated brain penetration of the Io-trolan. Revision of ventriculo-peritoneal shunt, admini-stration of steroids and hydration was performed. CSF findings demonstrated no abnormalities. Her symptoms were relieved gradually.

Iotrolan is a non-ionic contrast media of dimer type, composed of C₃₇ H₄₈ I₆ N₆ O₁₈- Its distinctive features are low distributing coefficient and high affinity with water. Contrasting several reports of Metrizamide ence-phalopathy, only 2 cases of Iotrolan encephalopathy were reported. Iotrolan is reported to be much safer than Metrizamide.

We were able to find brain penetration by Iotrolan. It is expected to be a characteristic radiological finding of encephalopathy induced by contrast media.

The mechanism of Iotrolan encephalopathy is obscure. Several theories concerning Metrizamide ence-phalopathy are proposed. These are ①inhibition of hexokinase, ②inhibition of acethylcholinesterase, ③im-munological mechanism and ④vascular disturbance. Io-trolan has no 2-deoxy-glucose structure. The inhibition theory of hexokinase is least expected. Related matters are circulatory disturbance of liquor, dehydration, ex-cessive contrast media, advanced age, diabetes mellitus, hypertension, epileptic patients and patients taking phe-nothiazines.

Prompt therapy is important. Removal of contrast media, hydration and administration of steroids should be performed as early as possible.