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AVM Grading Systems

Two main grading systems are often used to determine the severity of Arteriovenous Malformations (AVMs): the Spetzler-Martin Grading System and the Supplementary Spetzler-Martin Grading System.

  1. Spetzler-Martin Grading System

This grading system is used to predict the risk of surgical complications based on three AVM characteristics, each assigned a score from 1 to 3:

  • Size of the AVM: Small (< 3 cm) = 1 point; Medium (3-6 cm) = 2 points; Large (> 6 cm) = 3 points
  • Location: Non-eloquent areas = 0 points; Eloquent areas (areas of the brain responsible for major functions like movement, sensation, or speech) = 1 point
  • Presence of deep venous drainage: Absent = 0 points; Present = 1 point

The total score can range from 1 to 5, with higher scores predicting higher surgical risk:

  • Grade I (1 point): Minimal surgical risk
  • Grade II (2 points): Low surgical risk
  • Grade III (3 points): Moderate surgical risk
  • Grade IV (4 points): High surgical risk
  • Grade V (5 points): Very high surgical risk, often deemed inoperable
  1. Supplementary (or Lawton-Young) Spetzler-Martin Grading System

This system was developed to improve the predictive accuracy of the original Spetzler-Martin Grading System. It adds two additional characteristics:

  • Patient’s age: Younger than 20 = 0.1 points; 20-40 = 0.2 points; Older than 40 = 0.3 points
  • Hemorrhagic presentation: Absent = 0 points; Present = 0.1 points

The sum of these two additional points is added to the original Spetzler-Martin score, with the total ranging from 1 to 6. Higher scores correspond to higher surgical risk.

Clinical Significance

These grading systems assist in surgical decision making. Patients with lower grades (I and II) are usually suitable surgical candidates, as they have a lower risk of surgery-related neurological deficits. In contrast, patients with higher grades (IV and V) are at a high risk of surgical complications and are usually managed conservatively or with non-surgical methods like stereotactic radiosurgery or embolization.

However, these are just guidelines, and individual patient factors and the neurosurgeon’s experience and expertise must also be considered. Some patients with higher grade AVMs may still benefit from surgery, particularly if their risk of hemorrhage without surgery is high.