11/07/2025
This post is part of the new series “Neurosurgery Compact” – short, high-impact insights for students, residents, and anyone passionate about neuro.
Intrudictory case:
A 64-year-old patient presents with a 7 mm aneurysm at the anterior communicating artery (AComA) – no family history of SAH, non-smoker.
What would you do?
The PHASES Score (see below) helps estimate the rupture risk of unruptured intracranial aneurysms using 6 evidence-based factors.
Risk factors:
Population, Hypertension, Age, Aneurysm Size, Location, Family history – see chart below!
Example:
AComA aneurysm, 7 mm, 64 y/o, no SAH family history = 6 points → ~1.2% annual rupture risk
Bottom line: The PHASES Score is a helpful tool for risk stratification and shared decision-making – but not a substitute for clinical judgment.
A full handbook with 40+ neurosurgical scores is coming soon – stay tuned!
Let me know in the comments which score or topic you'd like next!
Hashtags:
📊 PHASES Score – Risk Estimation for Rupture of Unruptured Intracranial Aneurysms
Purpose:
Estimation of the annual rupture risk in incidentally discovered intracranial aneurysms.
🔹 Parameters (Scoring):
Population
Japan or Finland: 3 points
Other populations: 0 points
Hypertension
Yes: 1 point
Age
≥70 years: 1 point
Aneurysm Size
7–9 mm: 3 points
10–19 mm: 6 points
≥20 mm: 10 points
Previous SAH (from another aneurysm)
Yes: 1 point
Aneurysm Location
Vertebrobasilar / PCoA / AComA: 2 points
Other locations: 0 points
🔍 Interpretation:
Total score: 0–20 points
→ Corresponds to an annual rupture risk ranging from 10%
Clinical use:
Supports decision-making between conservative monitoring and intervention, especially during neurovascular board discussions.
⚠️ Limitations & Criticism of the PHASES Score
Population Bias (Japan/Finland overrepresentation):
The score assigns 3 points for origin from Japan or Finland – based on cohort studies from countries with exceptionally high rupture rates.
This may not be applicable to other ethnic groups or populations.
No consideration of aneurysm morphology:
Important morphological features such as irregular shape, daughter sac, lobulation, wall characteristics, or growth behavior are not included, despite being known predictors of rupture – particularly in small aneurysms.
No dynamic relevance:
PHASES is a static model. Changes over time (e.g., aneurysm growth, newly diagnosed hypertension, or smoking) are not factored into the risk.
Age ≥70 = 1 point – paradoxical effect:
Elderly patients receive an additional risk point, although they often carry higher perioperative risks and might be preferably managed conservatively, especially for small aneurysms.
No reference to technical feasibility or treatment risk:
The score does not account for surgical or endovascular complexity, e.g., in fusiform aneurysms or unfavorable anatomical locations.
Limited predictive value for small aneurysms (
