Occipital Arteriovenous Malformation and Visual Field Defect

Seo, Eui Kyo; Park, Hyeon Seon; Joo, Jin Yang; Lee, Kyu Chang

Abstract

The authors analyzed 38 consecutive cases with an occipital arteriovenous malformation(AVM) in regard to visual field defect. The incidence of occipital AVM was 10.4% among 367 patients with a cerebral AVM treated between 1975 and 1994 in our institute. Bleeding rate of occipital AVM in this series was 86.8%(EE cases) and it was significantly higher than that of AVM in other locations. Of 38cases, 15 patients(39.5%) had a visual field defect on admission and all of them were accompanied by intracerebral hematomas caused by the rupture of AVMs. The presence of visual field defect did not correlate with angioarchitecture in reference to pattern of nidus, feeding artery, and draining vein. Of 15 patients with visual field defect. 10 patients showed homonymous hemianopsia and five patients, homonymous quadrantanopsia. The size and location of intracerebral hematoma correlated well with hemispheric approach : 11, parietooccipital approach : 10, with six preoperative embolization and 1 postoperative gamma knife surgery. Fifteen patients underwent gamma knife surgery with five preoperative embolization. One patient underwent embolization only. The results of treatment were as follows : There were no mortality and morbidity except for visual field defect. We confirmed complete resection or obliteration of malformed vessels in 25 patients and reduction of the nidus size in eight patients. Five patients were not followed. After gamma knife surgery, two patients showed rebleeding during the follow up period. Among 23 patients who had no visual field defect before treatment, three patients showed visual field defect after treatment(one after microsurgical resection using occipital interhemispheric approach, two after preoperative embolization). In 15 patients with visual field defect before treatment, four patients showed improvement in their visual field defect after treatment(three after microsurgical resection using occipital interhemispheric approach, one after gamma knife surgery). The parietooccipital approach did not change the status of visual field in any of the ten parients. In occipital AVM, visual field defect was the most srious morbidity. Ruptured occipital AVM had a higher incidence of hemorrhage causing a visual field defect and had a higher indication of direct surgical approach than AVM of other location. In planning surgery of occipital AVM, one has to count microsurgical anatomy based on the visual pathway as well as clinical findings such as the angioarchitecture, location of intracerebral hematoma, and preopeative visual field.