Involvement of the visual pathway is not a risk factor of visual field deficits in patients with occipital arteriovenous malformations: an fMRI study

Abstract

Occipital arteriovenous malformations (AVMs) are still one of neurosurgery’s most intriguing and challenging pathologies. In this study, we reviewed our series of patients with occipital AVMs admitted in Beijing Tiantan Hospital from June 2013 through January 2015 and attempted to evaluate the risk factors of visual field deficits (VFDs) in these patients at presentation. Forty-two consecutive patients with occipital AVMs were included in our study. Patient parameters (age, sex, and history of hemorrhage) and AVM characteristics (size, side, venous drainage, Spetzler-Martin grade, and diffuseness) were collected. VFDs were quantified using an Octopus perimetry. Conventional MRI, blood oxygen level dependent fMRI (BOLD-fMRI) of the visual cortex, and diffusion tensor imaging (DTI) of the optic radiation were performed. The least distances from the AVM to the optic radiation (AVM-OR) and from the AVM to the visual cortex (AVM-VC) were measured. Univariate analyses were used to correlate initial VFDs with patient parameters, AVM characteristics, AVM-OR, and AVM-VC distances. VFDs were identified in 14 patients, among which 12 patients presented with a history of hemorrhage and 2 patients presented with nonhemorrhagic chronic headache. VFDs were more common (P = 0.000003) in patients with ruptured AVMs. VFD frequency was not associated with patient age, sex, and AVM characteristics (size, side, venous drainage, S-M grade, and diffuseness). Unlike other lesions involving the optic radiation and visual cortex, the frequency of VFDs in occipital AVMs did not correlate with the AVM-OR and AVM-VC distances (P = 0.640 and 0.638, respectively). A history of hemorrhage is an independent risk factor of VFDs in occipital AVMs. Most unruptured occipital AVMs may present with chronic headache and seizures other than VFDs. The distances from the AVMs to the optic radiation and the visual cortex are not associated with preexisting VFDs. Our results prompt us to probe into the plasticity of the visual pathway in patients with this congenital vascular anomaly.