A120 The muesli sign for detecting non-ischemic cerebral enhancing (NICE) lesions after endovascular treatments

<h3>Introduction</h3> Non-ischemic cerebral enhancing (NICE) lesions are a known complication of neuroendovascular procedures attributed to foreign body emboli. Their detection currently depends on contrast-enhanced MRI, limiting early identification. <h3>Aim of study</h3> To propose and evaluate the ‘Muesli sign’ as a non-contrast MRI marker for NICE lesions in routine non-contrast follow-up imaging. <h3>Method</h3> In this retrospective multicenter study, 57 patients with diagnosed NICE lesions after neuroendovascular treatments were reviewed by two independent neuroradiologists and the presence of the Muesli sign, defined as nodular T2 hypointensities within cerebral edema on non-contrast MRI, was evaluated. <h3>Results</h3> The Muesli sign was present in 72.5% of cases (29/40) with any available T2-weighted imaging, with excellent interrater agreement (Cohen’s κ = 0.79). Detection was most reliable on thick-slice 2D FLAIR sequences (72% consensus sensitivity), compared to 3D FLAIR (61%) and T2 spin-echo sequences (54%). <h3>Conclusion</h3> The Muesli sign shows promise as imaging marker to identify patients with NICE lesions on non-contrast follow-up MRI, potentially enabling earlier and widespread identification of patients affected by cerebral foreign body embolization after neuroendovascular procedures. Recognizing this sign could improve postprocedural monitoring and guide further diagnostic or therapeutic steps. <h3>Conflict of Interest</h3> No