Michael Morgan, AVMs, and the Spetzler Grading System

Michael Morgan, a neurosurgeon from Sydney, Australia and specialist in arteriovenous malformations (AVM) spoke today.  He has seen approximately 600 patients with AVMs and operated on 529 of them.  In his hands, the risks of a surgical resection of a SM grade 1 AVM is less than the risks of gamma knife.  It is also more commonly definitive therapy.  It is far less risky than Onyx embolization.  However, Dr. Morgan is a unique surgeon and not every surgeon is going to be able to achieve similar results.

Other interesting points from his lecture:

• The risk of hemorrhage from AVMs with no prior history of hemorrhage is approximately 1% per year.
• The risk of hemorrhage from AVMs with a prior history of hemorrhage is approximately 6% per year.
• The risk of subsequent hemorrhage varies according to presenting symptoms: hemorrhage from an incidental AVM or a AVM that presents with seizures is less than an AVM that presents with hemorrhage.
• Contrary to common beliefs, the Spetzler-Martin Scale is remarkably accurate at defining the preoperative risk of surgery.
• Even in his expert hands, the risk of surgery of a Grade 5 AVM is upwards of 50%.
• He maintains strict blood pressure control in patients undergoing surgery for a higher risk AVM (SM grade 3+) with a goal MAP less than 70.
• AVMs which hemorrhage into the subarachnoid space can induce severe vasospasm.  Appropriate prophylactic measures should be undertaken in cases with subarachnoid spread of hemorrhage.

Spetzler Grading System
	Points
Size (cm)
Small (<3cm)	1
Medium (3-6cm)	2
Large (>6cm)	3
Eloquence
Non-eloquent	0
Eloquent	1
Venous Drainage
Superfical only	0
Deep	1

Spetzler Outcomes (%)
Grade	No Deficit	Minor Deficit	Major Deficit
1	100
2	95	5
3	84	12	4
4	73	20	7
5	69	19	12

The point – operate on Grades 1-3, think twice on Grades 4 and 5.

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