[What should we call this group of disease? (author's transl)].

In past several years in Japan, there were many reports on a certain group of cases which were called by many names such as abnormal vascular network in the cerebral basal region, spontaneous occlusion of the circle of Willis, Cerebrovascular Moyamoya disease, cerebral juxabasal telangiectasia and so on. The characteristics of this group are; 1. Angiographically, they show a narrowing at the distal portion of the internal carotid artery, horizontal portions of the anterior and/or middle cerebral arteries with extensively developed perforators, i.e. abnormal vascular network. 2. Nowadays, it is becoming possible to give accurate diagnosis by only clinical information. 3. The cause is not known and so this group has not yet been recognized as a clinico-pathological entity. This group of the cases was first recognized and mainly investigated by Japanese neurosurgeons. But they have used many names as shown Table 1. Such a variety of the names seems to be troublesome for investigator and a single appropriate name should be used. From the Japanese and other country's reports, the name of this disorder can be divided into 5 categories as follows; Category 1: from the viewpoint of clinical symptoms and sign. Category 2: from the viewpoint of only abnormal vascular network on angiograms. Category 3: from the finding of the arterial narrowing. Category 4: from the both findings of the abnormal vascular network and arterial narrowing. Category 5: miscellaneous. The annual changes in usage frequency of various designation about this disorder has investigated and it disclosed the difference between Japan and other countries. The questionairre about the naming was sent to 306 investigators who had reported the cases. And the summary of their response as follow: 1) Most of them agree with determination of a single name. 2) Their most favorite name belongs to Category 2. This means that the most impressive finding was not the obstruction but the vascular network shown in angiograms. 3) The name "Abnormal vascular network" and "Moyamoya" mean the same phenomenon. In spite of having many disputation such as unacademic, not including the idea of arterial obstruction, and difficulty to understand for foreigners, but the name "Moyamoya" was pointed out by many investigators that it has many advantages such as being short and humorous, Moyamoya also has a meaning of unknown origin in Japanese, and already very popular worldwide. In my opinion, this group must not be called as "Moyamoya disease", but simply "MOYAMOYA".