Spetzler-Martin Grade III arteriovenous malformations: surgical results and a modification of the grading scale.
OBJECTIVE
To analyze surgical results for the highly variable Spetzler-Martin Grade III arteriovenous malformations (AVMs), to demonstrate that outcomes vary among the different types of Grade III lesions, and to introduce a simple modification of the grading scale that might improve its usefulness for these AVMs.


METHODS
In a consecutive series of 174 brain AVMs resected from 174 patients during a period of 4.8 years, 76 AVMs (45.2%) were Grade III. There were 35 small AVMs (S1V1E1) (46.1%), 14 medium/deep AVMs (S2V1E0) (18.4%), and 27 medium/eloquent AVMs (S2V0E1) (35.5%). No large Grade III AVM (S3V0E0) was treated.


RESULTS
Complete AVM resection was accomplished for 74 patients (surgical obliteration rate, 97.4%). Three patients (3.9%) experienced permanent, treatment-associated, neurological morbidity, and three patients died (surgical mortality rate, 3.9%). Good outcomes (Rankin scale scores of <or=2) were observed for 59 patients (78.7%). Surgical risks (new deficit or death), according to the Grade III type, were 2.9% for small AVMs (S1V1E1), 7.1% for medium/deep AVMs (S2V1E0), and 14.8% for medium/eloquent AVMs (S2V0E1).


CONCLUSIONS
Grade III AVMs are a heterogeneous group, with each type possessing different surgical risks, and the Spetzler-Martin grading scale should be modified accordingly. Grade III- AVMs (S1V1E1) have a surgical risk similar to that of low-grade AVMs and can be safely treated with microsurgical resection. Grade III+ AVMs (S2V0E1) have a surgical risk similar to that of high-grade AVMs and are best managed conservatively. Grade III AVMs (S2V1E0) have intermediate surgical risks and require judicious selection for surgery. Grade III* AVMs (S3V0E0) are either exceedingly rare, with a surgical risk that is unclear, or theoretical lesions with no clinical relevance.
Lawton
Michael T
MT
Department of Neurological Surgery, University of California, San Francisco 94143-0112, USA. lawtonm@neurosurg.ucsf.edu
D000293:Adolescent; D000328:Adult; D000368:Aged; D001925:Brain Damage, Chronic / Q000209:etiology / Q000401:mortality; D002648:Child; D003131:Combined Modality Therapy; D004621:Embolization, Therapeutic; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000145:classification / Q000401:mortality / Q000601:surgery*; D008297:Male; D008866:Microsurgery; D008875:Middle Aged; D009460:Neurologic Examination; D010348:Patient Care Team; D011183:Postoperative Complications / Q000209:etiology / Q000401:mortality; D016634:Radiosurgery; D012189:Retrospective Studies; D012306:Risk