The PHASES score is a clinical calculator used to estimate the 5-year risk of rupture for intracranial aneurysms. The acronym PHASES stands for Population, Hypertension, Age, Size of aneurysm, Earlier subarachnoid hemorrhage from another aneurysm, and Site of aneurysm. This scoring system is applicable to patients with unruptured intracranial aneurysms. 

The clinical utility of the PHASES score is to aid clinicians in decision-making regarding the management of unruptured intracranial aneurysms. It helps to stratify patients into different risk categories and thus guide treatment strategies, which can range from conservative management to surgical intervention.

The PHASES score may not be applicable to patients with ruptured aneurysms, fusiform aneurysms, or aneurysms associated with arteriovenous malformations. It is also less reliable in patients with multiple aneurysms or in those with a family history of aneurysmal subarachnoid hemorrhage.

PHASES score for intracranial aneurysm rupture risk

# Criteria
 ## (P) Population
A. North American, European (other than Finnish) (+0)
B. Japanese (+3)
C. Finnish (+5)
## (H) Hypertension
D. No (+0)
E. Yes (+1)
## (A) Age
F. < 70 years (+0)
G. >= 70 years (+1)
## (S) Size of aneurysm
H. < 7.0 mm (+0)
I. 7.0-9.9 mm (+3)
J. 10.0-19.9 mm (+6)
K. >= 20 mm (+10)
## (E) Earlier subarachnoid haemorrhage from another aneurysm
L. No (+0)
M. Yes (+1)
## (S) Site of aneurysm
N. Internal carotid artery (+0)
O. Middle cerebral artery (+2)
P. Anterior cerebral arteries, posterior communicating artery, or posterior circulation (+4)

# Conditions
- score <= 2
- score == 3
- score == 4
- score == 5
- score == 6
- score == 7
- score == 8
- score == 9
- score == 10
- score == 11
- score >= 12
- score == 0