Author carried out this study for clarifying topographical characteristics and verifying scale of natural phenomenon in the places indicated by the “Shizensaigaidenshohi” (monument of natural disaster). The followings are the major results.

1) Clarification of topographic characteristics where a “Shizensaigaidenshouhi” stands or indicates.

Most of the place where “Shizensaigaidenshouhi” (monument of natural disaster, simply referred to as “the monument” in this article) stands or indicates, locates not only in very low areas (e.g. flood plain), but also in a

higher areas (e.g. natural levee). This is because the monument building was not reasoned by heavy rainfall or flood itself, but by the damage of lives or properties which exist in higher areas.

2) Verification of scale of natural phenomenon which brought disaster where a “Shizensaigaidenshouhi” stands or indicates.

Past flood depth inferred by the description of the subject monuments was slightly low or equal to that estimated by modern hazard map. In early and middle of the 20th century, many flood disaster happened and the relevant monuments were built thereafter, but in the late 20th century, the number of severe floods which recorded in the monuments decreased. However, frequency of heavy rainfall is increasing recently. This suggests flood disasters likely to be recorded in the monuments would occur again in the near future.

These results show that location of a “Shizensaigaidenshouhi” stands or indicates prefers a

higher areas as people lives more in such areas compered to lower land and also show that past flood depth inferred by the description of the subject monuments was compatible with that estimated by modern hazard map.

Map symbol “Shizensaigaidenshohi” is recently introduced to the basic topographic maps, and the new topographic maps therefore provide people with new map reading experience, which might raise people's awareness of disaster prevention as existence of “Shizensaigaidenshohi” is deeply relating to topography.

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  Objective : The authors present the anatomical and angiographical details that enable surgeons to quickly locate middle cerebral artery (MCA) aneurysms and to gain proximal control without unnecessary delay or premature rupture.
  Materials and Methods : The anatomical dissections were performed in 10 adult cadaveric heads from 1993 to 2011 at the Department of Neurological Surgery, University of Florida. The angiographic and the surgical data were derived from 93 MCA aneurysms operated on by Hung Tzu Wen (HTW) from 1996 to 2012 at the Hospital das Clínicas, University of São Paulo and Hospital Samaritano, Brazil.
  Results : MCA aneurysms arise most frequently from the M1 segment and less frequently from M2. From a practical viewpoint, the M1 extends from the carotid bifurcation to the MCA genu (on the basal surface of the cerebrum) with specific topographical relationships along the way, and the M2 extends from the MCA genu to the sylvian or “M” point (on the lateral surface), also with specific topographical relationships. The key for the angiographical analysis of an MCA aneurysm is to establish its topographical relationship to the genu of the MCA. If it is proximal to the genu, it is important to estimate its distance to the carotid bifurcation and to the MCA genu. If it is distal to the MCA genu, it is important to estimate its distance to the genu and to the sylvian point ( “M” point). Also, it is important to evaluate the direction of the dome of the aneurysm, as it indicates the structures to which the dome is attached. The key for locating an MCA aneurysm intraoperatively is the relationship between the MCA genu and the tip of the pars triangularis. The tip of the pars triangularis is a reliable intraoperative landmark (even when it is obscured by severe subarachnoid hemorrhage) and it is located just distal to the MCA genu and approximately 2 cm distal to the sharp transition between the basal and the lateral surfaces of the cerebrum. Once the pars triangularis is identified, the MCA genu can also be quickly estimated and identified, and thereby so will the aneurysm.
  Conclusion : The carotid bifurcation, genu of the MCA, and the “M” point on the AP view carotid angiography, and the sylvian triangle on the lateral projection constitute the cardinal landmarks for locating MCA aneurysms angiographically. Correlating the angiographic location of the aneurysm to the pars triangularis of the inferior frontal gyrus constitutes the key for then locating the MCA aneurysm intraoperatively.

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