gms | German Medical Science

Objective: Intracranial AVMs are rare congenital malformations with posterior fossa AVMs representing only 7 to 15% of all intracranial AVMs. These infratentorial AVMs are often considered as potentially hazardous as they are thought to present more often with hemorrhage and are associated with poor outcome. Furthermore, posterior fossa AVMs may harbor AVM-associated aneurysms more frequently. In this study, we examine the incidence, angioarchitecture, hemorrhage rate and outcome of supra- and infratentorial AMVs in our neurovascular center.

Method: We retrospectively analyzed all patients with cerebral AVMs presenting to our neurovascular center between 2005 and 2015. Patients were analyzed regarding location and angioarchitecture of the AVM including the presence of AVM-associated aneurysms, bleeding events, and outcome during follow-up. Outcome was assessed using the modified Ranking Scale (mRs) and stratified into favorable (mRS 0-2) and non-favorable (mRs 3-6).

Results: 316 patients with cerebral AVMs were admitted to our center. 104 of 251 (41.6%) patients with a supratentorial AVM and 45 of 65 (69.2%) patients with an AVM of the posterior fossa presented with a hemorrhage initially (p<0.001). Of 149 (47.2%) patients with a symptomatic hemorrhage 97 (65.1%) patients showed a good clinical status at admission (WFNS I-III), whereas 50 (33.6%) patients had a worse clinical status (WFNS IV-V). Infratentorial AVMs had lower Spetzler-Martin-Grades (p=0.003) mostly due to the fact that they were smaller (95.1% <3 cm nidus-diameter, p=<0.001). Associated aneurysms were more frequent in posterior-fossa AVMs (38.5 % vs. 20.7 %, p=0.004) and were associated with an increased risk of hemorrhagic presentation (30.9% vs. 18.7%, p=0.013). Analyzing only posterior-fossa AVMs, the presence of an associated aneurysm just failed to reach statistical significance as predictor for hemorrhage (46.7% vs. 20.0%, p=0.055). Outcome was poor in 18 of 99 (18.2%) patients with supratentorial ruptured AVM and 15 of 43 (34.9%) patients with infratentorial ruptured AVM, respectively (p=0.030). Seven patients were lost to follow-up. The risk of a new hemorrhage-associated deficit was significantly higher in posterior fossa-AVMs (p=0.001).

Conclusions: Posterior fossa AVMs are associated with an increased hemorrhage rate and represent a predictor for poor outcome. These differences may be based on anatomical conditions or the presence of associated aneurysms.