Enhancing brain lesions after endovascular treatment of aneurysms

Abstract

Complications of endovascular therapy of aneurysms mainly include aneurysm rupture and thromboembolic events. The widespread use of MR imaging for follow-up of these patients revealed various nonvascular complications such as aseptic meningitis, hydrocephalus, and perianeurysmal brain edema. We present 7 patients from 5 different institutions that developed MR imaging-enhancing brain lesions after endovascular therapy of aneurysms, detected after a median time of 63 days. The number of lesions ranged from 4-46 (median of 10.5), sized 2-20 mm, and were mostly in the same vascular territory used for access. Three patients presented with symptoms attributable to these lesions. After a median follow-up of 21.5 months, the number of lesions increased in 2, was stable in 1, decreased in 3, and disappeared in 1. The imaging and clinical characteristics suggested a foreign body reaction. We could find no correlation to a specific device, but a possible source may be the generic hydrophilic coating.

Fig 1.

A 54-year-old woman with a right supraclinoid ICA unruptured aneurysm treated with a flow diverter. Axial DWI on postoperative day (POD) 1 (A), contrast-enhanced T1-weighted and T2-FLAIR at 4 months (B), and 9 months after procedure (C). POD 1 MR image shows a few asymptomatic DWI lesions in the frontal lobe. Four-month follow-up MR shows subcortical enhancing lesions in both the frontal and parietal lobes, far more numerous than the DWI lesions seen in POD 1. The enhancing lesions and the perilesional edema persist in the 9-month follow-up MR imaging, which is not the expected evolution for ischemic lesions. Foreign body reaction was the presumed diagnosis after all clinical and laboratory work-up was negative for infection.

Fig 2.

A 32-year-old woman with an unruptured left MCA aneurysm treated with balloon-assisted coiling. Axial FLAIR and axial T1-weighted contrast-enhanced MR images at 6 months (A) and 11 months (B) follow-up show multiple enhancing cortico-subcortical lesions in the distal MCA territory surrounded by vasogenic edema. Combined antibiotic therapy was initiated after (A) with only partial improvement in the next follow-up. Note how the middle temporal gyrus lesion disappears over time while the middle frontal lesions only decrease in number.

Fig 3.

A 51-year-old woman with an asymptomatic intradural left cavernous ICA aneurysm treated with a flow diverter. Axial contrast-enhanced T1-weighted, T2-FLAIR, and DWI brain MR images at 3 months (A) and 6 months (B). A, Representation of 1 of the rim-enhancing lesions in the frontal operculum, with significant perilesional edema and restricted diffusion. An infectious cause was ruled out on clinical grounds and a foreign body reaction was considered as the most possible cause. The patient received 6 weeks of combined oral antibiotic therapy and remained asymptomatic. B, At 6-month follow-up, the lesions show a solid pattern of enhancement, with no restricted diffusion and only partial improvement of the edema. This was considered to represent the evolution of an aseptic abscess into a foreign body granuloma. The lesions and the surrounding edema decrease slowly in size but at 2-year follow up still exist (not shown).