Cerebral foreign body reaction after carotid aneurysm stenting

Abstract

Flow diverter stents are new important tools in the treatment of large, giant, or wide-necked aneurysms. Their delivery and positioning may be difficult due to vessel tortuosity. Common adverse events include intracranial hemorrhage and ischemic stroke, which usually occurs within the same day, or the next few days after the procedure. We present a case where we encountered an unusual intracerebral complication several months after endovascular treatment of a large left internal carotid artery aneurysm, and where brain biopsy revealed foreign body reaction to hydrophilic polymer fragments distally to the stent site. Although previously described, embolization of polymer material from intravascular equipment is rare. We could not identify any other biopsy verified case in the literature, with this particular presentation of intracerebral polymer embolization--a multifocal inflammation spread out through the white matter of one hemisphere without hemorrhage or ischemic changes.

Keywords: Cerebral aneurysm; cerebrovascular disease; endovascular; flow diverter stent; foreign body reaction.

Figure 1.

Plain noncontrast head CT at initial admission three months after elective stenting of the left paraophthalmic aneurysm. The image shows a diffuse edema of the white matter of the ipsilateral hemisphere with a decreased demarcation of the sulci.

Figure 2.

Cerebral MRI performed immediately after the CT scan. T2-weighted sequence (a), apparent diffusion coefficient (ADC) map (b), diffusion weighted sequence (c), and postgadolinium-T1 sequence (d). There is an increased signal on the T2-weighted sequence and increased diffusion on the ADC map, consistent with vasogenic edema in the white matter of the left hemisphere, most apparent frontally and parieto-occipitally. The patchy contrast enhancement is poorly visible due patient motion artifacts.

Figure 3.

T2-weighted (a) and postgadolinium-T1 (b) MRI one week later and after a course of high dose methylprednisolone, showing unchanged white matter edema on the T2 weighted sequence, but a significantly reduced contrast enhancement on the T1 sequence.

Figure 4.

T2-weighted (a) and postgadolinium-T1 (b) MRI 3 months later and after discontinuation of methylprednisolone, showing a slight change in the distribution of the edema in the left hemisphere now appearing more cranially, with a corresponding increase in contrast enhancement.

Figure 5.

T2-weighted (a) and postgadolinium-T1 (b) MRI at 15 months of follow-up on a low dose of oral prednisone and azathioprine, showing a marked improvement and only a dural contrast enhancement frontally in the left hemisphere, at the site of the brain biopsy.

Figure 6.

Photomicrograph of a hematoxylin and eosin stained sample of the frontal lobe showing a non-polarizable foreign material surrounded by multinucleated foreign-body type macrophage inside a small meningeal vessel. The adjacent brain parenchyma contains a well-demarcated microabscess filled with neutrophilic granulocytes and multinucleated macrophages.