An aneurysm is a protrusion of the wall of an artery. Unruptured cerebral aneurysms, which are not rare, are aneurysms that have never ruptured. They are found 4-6% of people in the general adult population. Rupture of the aneurysm leads to subarachnoid hemorrhage (SAH), a frequently fatal condition. Even with optimal treatment, only one of three patients who suffer SAH can recover from the illness and return to the previous level of social activity. Others survive but remain handicapped. Almost half of all patients with SAH die.

The annual rate of rupture of these aneurysms is not clearly known. In addition, treating an unruptured aneurysm to prevent rupture is not without risk, even under the care of the best neurosurgeons. Therefore, understanding the natural history and current treatment standards for unruptured aneurysms is imperative for better management of this disease entity.

According to a survey by the Japan Neurosurgical Society, more than 10,000 patients with unruptured cerebral aneurysms are treated in Japan every year by surgical clipping or endovascular coiling.

Number of intracranial aneurysms treated in Japan

Based on data from the Japan Neurosurgical Society, more than 10,000 patients with unruptured intracranial aneurysms (UCAs) undergo surgical intervention (clipping or coiling). And the number of treatment is increasing each year. In 2010, more than 16,000 UCAs were treated either by clipping or coiling in Japan and this number is close to twice compared to that of year 2000.

  Ruptured Cerebral Aneurysm Unruptured Cerebral Aneurysm
Year Clipping Endovascular Clipping Endovascular
2000 17,162   7,689  
2001 17,373 1,805 7,999 1,553
2002 17,396 1,934 8,540 1,486
2003 17,012 2,441 8,817 1,932
2004 16,668 2,698 8,588 2,019
2005 15,944 2,998 8,755 2,377
2006 15,635 3,463 8,839 3,053
2007 15,252 3,833 9,544 3,621
2008 14,679 4,136 10,116 3,909
2009 14,512 4,246 10,001 4,134
2010 13,607 4,440 10,846 5,162

Data shown here belong to Japan Neurosurgical Society.

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