title: Surgical outcomes after classifying Grade III arteriovenous malformations according to Lawton's modified Spetzler-Martin grading system.
abstract: OBJECTIVE
  We aimed to evaluate microsurgical outcomes after classifying Grade III arteriovenous malformations (AVMs) according to Lawton's modified Spetzler-Martin grading system.
  
  
  METHODS
  Of 131 patients with Grade III AVMs, 55 had undergone microsurgery between 1995 and 2010. The 55 AVMs were classified as follows: Grade III-/S1E1V1, Grade III/S2E0V1, Grade III+/S2E1V0, or Grade III*/S3E0V0. The surgical obliteration rate, morbidity rate, and functional outcomes for each subtype were compared before surgery and after follow-up. Additionally, factors related with morbidity were investigated from demographic and morphological characteristics.
  
  
  RESULTS
  We observed 18 Grade III-, 16 Grade III, 20 Grade III+, and 1 Grade III* AVMs. Complete resection was achieved in 49 patients (obliteration rate, 89.1%). Incomplete resection rates were higher for Grade III (12.5%) and III+ (15.0%) AVMs than that for Grade III- (5.6%) AVMs. Seven patients (12.7%) presented postoperative deficits, of which 3 (5.4%) experienced disabilities. Patients with Grade III+ (25.0%) had higher morbidity rates than those with other subtypes. Modified Rankin scale scores at the last follow-up indicated unfavorable outcomes for Grades III (18.8%) and III+ (25.0%) AVMs. AVM size (≥3 cm) and non-hemorrhagic type were associated with the occurrence of postoperative deficits (p<0.05).
  
  
  CONCLUSIONS
  The modified classification of Grade III AVMs was useful to predict surgical morbidity and clinical outcomes. We recommend that microsurgery should be used to treat Grade III- AVMs, but should be considered carefully for the treatment of Grades III and III+.
authors.affiliation: Department of Neurosurgery, Severance Hospital, Stroke Center, Yonsei University College of Medicine, 50-1, Yonsei-ro, Seodaemoon-gu, Seoul 120-752, Republic of Korea.
authors.forename: Hong Jun
authors.initials: HJ
authors.lastname: Jeon
authors.affiliation: Department of Neurosurgery, Severance Hospital, Stroke Center, Yonsei University College of Medicine, 50-1, Yonsei-ro, Seodaemoon-gu, Seoul 120-752, Republic of Korea.
authors.forename: Keun Young
authors.initials: KY
authors.lastname: Park
authors.affiliation: Department of Neurosurgery, Severance Hospital, Stroke Center, Yonsei University College of Medicine, 50-1, Yonsei-ro, Seodaemoon-gu, Seoul 120-752, Republic of Korea.
authors.forename: So Yeon
authors.initials: SY
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Severance Hospital, Stroke Center, Yonsei University College of Medicine, 50-1, Yonsei-ro, Seodaemoon-gu, Seoul 120-752, Republic of Korea. Electronic address: leejw@yuhs.ac.
authors.forename: Jae Whan
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Severance Hospital, Stroke Center, Yonsei University College of Medicine, 50-1, Yonsei-ro, Seodaemoon-gu, Seoul 120-752, Republic of Korea.
authors.forename: Seung Kon
authors.initials: SK
authors.lastname: Huh
authors.affiliation: Department of Neurosurgery, Severance Hospital, Stroke Center, Yonsei University College of Medicine, 50-1, Yonsei-ro, Seodaemoon-gu, Seoul 120-752, Republic of Korea.
authors.forename: Kyu Chang
authors.initials: KC
authors.lastname: Lee
mesh_terms: D000328:Adult; D003399:Craniotomy; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000145:classification* / Q000601:surgery*; D008297:Male; D008866:Microsurgery; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D016634:Radiosurgery; D012720:Severity of Illness Index; D016896:Treatment Outcome; D055815:Young Adult
keywords: Cerebral arteriovenous malformation; Microsurgery; Modified Spetzler–Martin grading scale; Treatment outcome