Nongalenic Arteriovenous Fistulas: History of Treatment and Technology

Kristen Upchurch, MD; Lei Feng, MD, PhD; Gary R. Duckwiler, MD; John G. Frazee, MD; Neil A. Martin, MD; Fernando Viñuela, MD

Disclosures

Neurosurg Focus. 2006;20(6) 

In This Article

Defining Features

Infrequency of Nongalenic AVFs

Nongalenic AVFs are rare lesions. They arise sporadically both as isolated phenomena and in congenital, non hereditary Wyburn-Mason syndrome; they also occur in inherited disorders such as the Rendu-Osler-Weber syndrome.[6,27,30,35] The infrequency of nongalenic AVFs can best be assessed in the context of more common AVMs by considering two single-institution experiences recorded during 10-year periods. At one tertiary care institution, five (1.6%) of 320 AVMs treated in a 10-year period were found to be nongalenic AVFs;[15] at another tertiary care center, in the same length of time, 12 (4.8%) of 251 cerebrovascular malformation cases (not including dura-based lesions) were diagnosed as nongalenic AVFs.[36] Given an AVM incidence of approximately 1 per 100,000 per year in unselected populations, the rarity of nongalenic AVFs is clear.[1]

Anatomy of Nongalenic AVFs

Nongalenic AVFs can be single or multiple, with a higher probability of multiple lesions occurring in patients with inherited syndromes.[6] The anatomical and physiological hallmark of the nongalenic AVF is the direct emptying of one or more feeding arteries into a large varix that has very high flow. This associated varix is a venous ectasia distal to the fistula that most likely develops due to the varix's high flow and often has mural calcification.[21,36,37,38,41] Nongalenic AVFs are always associated with such a varix and are sometimes associated with other vascular abnormalities such as AVMs or aneurysms. Such aneurysms typically are located at a bifurcation where a minor vessel branches off a major feeding artery immediately proximal to the fistula.[36]

The varix of a nongalenic AVF is typically extraparenchymal, with the fistula itself in a superficial cortical location and often obscured by the varix.[21,37] The location of the varix correlates with the arterial supply of the AVF, with frontal and medial parietal varices fed by the anterior cerebral artery, temporal and parietal convexity varices associated with the MCA, and occipital varices supplied by the posterior cerebral artery (Fig. 1).[21] More posteriorly located lesions are sometimes supplied by branches of the basilar artery.[21,36] The route of venous drainage depends on the location of the nongalenic AVF, with most interhemispheric and convexity varices draining into the superior sagittal sinus and many temporal and occipital AVFs re ported as draining into both the superior sagittal and transverse sinuses.[21]

Figure 1.

Schematics depicting the gross angioarchitecture of four cases of nongalenic AVFs from the 1992 UWO–UCLA series, demonstrating that frontal and medial parietal varices are typically fed by the anterior cerebral artery (Cases 1–3), whereas parietal convexity varices (Case 4) and temporal varices (not shown) are supplied by the MCA.

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