Symptomatic intracranial embolic foreign-body reactions after endovascular neurointerventional procedures: A retrospective study in a tertiary hospital

•Polymer-embolization during endovascular procedures may lead to foreign-body reaction•Symptomatic reactions are uncommon complications of neurointerventional procedures•Asymptomatic fluctuation of lesions and symptomatic rebounds may occur over time•Diagnostic angiographies might have lower risk than therapeutic procedures•This entity’s early recognition enables making proper diagnosis-treatment decisions Polymer-coats may peel-off the surface of catheters and devices during endovascular procedures and might lead to brain inflammatory foreign-body reactions. We conducted a retrospective, descriptive, single-centre study including all patients with symptomatic intracranial oedematous and contrast-enhancing lesions after any neurointerventional procedure performed in our hospital between 2013 and 2019. From a total of 7446 neurointerventional procedures, 11 cases were identified (9 female, 2 male, median age 47 year-old), with an incidence of 0.14 %. The procedures were therapeutic in all: ten aneurysm embolization/isolation, one acute ischaemic stroke recanalization. Intracranial coils, stent or both were placed in all. Symptoms appeared during the following one day to fourteen months (median of 4.2 weeks). Brain MRI showed oedematous, contrast-enhancing lesions scattered through the vascular territory of the canalized vessel. Brain biopsy confirmed the diagnosis in one case and was supportive in another one. Eight patients received immunosuppression. No treatment was started in two. After a median time of follow-up of 3.5 years, five patients are totally asymptomatic. One patient presents slight weakness. Four patients have remote symptomatic seizures, but they have comorbid lesions (previous stroke, intracranial haemorrhage, biopsy needle-track’s gliosis). Follow-up MRI showed significant improvement in all the cases, with complete resolution in five. Non-symptomatic lesion fluctuation was observed in three cases. Two patients experienced symptomatic rebounds. Intracranial embolic foreign-body symptomatic reactions are uncommon complications of neurointerventional procedures. Diagnostic angiographies might have lower risk of polymer-embolization than therapeutic procedures. This entity’s early recognition enables making proper diagnosis and treatment decisions.