Non-ischemic cerebral enhancing lesions secondary to endovascular aneurysm therapy: nickel allergy or foreign body reaction? Case series and review of the literature.

INTRODUCTION: Delayed onset of non-ischemic cerebral enhancing (NICE) lesions is a rare complication of intracranial aneurysms' endovascular therapy (EVT). The purpose of this study is to report this rare complication and its potential pathophysiology in a single-center case series and review the relevant literature. METHODS: After retrospective review of all patients managed by EVT at our institution from January 1, 2012 to December 31, 2014, 2 out of 374 patients (0.5 %) with such a complication were identified. Skin patch testing was performed with all endovascular devices used in the two patients and with the European baseline series, including nickel. All previously published cases in the English literature were reviewed based on exhaustive PubMed and Embase research. RESULTS: Patient no. 1 developed NICE lesions 1 month after balloon-assisted coiling of a ruptured anterior communicating artery aneurysm. Patient no. 2 developed NICE lesions 12 months (the longest delay reported to date for such a complication) after the treatment of a right carotid-ophthalmic aneurysm by loose coiling and flow diversion. Patient no. 2 demonstrated nickel skin reactivity, but none of the two patients presented allergic reaction to the devices used during interventions. CONCLUSIONS: Based on our observations and review of the literature, we hypothesize that delayed non-ischemic cerebral enhancing lesions after EVT are more likely related to foreign body emboli rather than nickel allergy. The two presented cases demonstrate the potential for recurrence and prolonged fluctuation of NICE lesions, warranting long-term follow-up for all patients presenting this complication.