ABSTRACT NUMBER: ESOC2026A1155 A DIAGNOSTIC AMBIGUITY BETWEEN FUNCTIONAL NEUROLOGICAL DISORDER AND ACUTE ISCHAEMIC STROKE (CRYPTOGENIC STROKE SECONDARY TO PATENT FORAMEN OVALE)

Abstract Background and aims Patent-Foramen-Ovale-(PFO), a persistent flap-like opening between the atrial septa, is found in approximately 25% of the adult population. While typically benign, it is identified in nearly 50% of young patients (60 years or younger) with cryptogenic-Stroke-(CS)—ischemic events of undetermined origin despite extensive evaluation. Methods A woman in her early 40s with a history of Spina-Bifida and Fibromyalgia presented with a one-week history of expressive aphasia, memory impairment, and progressive left-sided sensory loss. Initial neurological examination was largely unremarkable (NIHSS 2), but urgent neuroimaging revealed complex findings. A CT-brain identified a high-density focal lesion in the left frontal lobe, while MRI head demonstrated scattered frontoparietal acute lacunar infarcts and evidence of old cerebral microbleeds-(CMBs). Results Initially the patient was treated with DAPT. Interval MRI at six weeks demonstrated a significant disease progression, with new multifocal infarcts and microhaemorrhages. Exhaustive "young-stroke" investigations were normal apart from bubble-echocardiogram confirming a PFO. The coexistence of recurrent ischemic infarcts and microhaemorrhages in a young patient necessitates the exclusion of rare small-vessel-disease. While the PFO suggests an embolic source, the progressive microvascular changes have prompted further investigation into Cerebral-Autosomal-Dominant-Arteriopathy-with-Subcortical-Infarcts-and-Leukoencephalopathy-(CADASIL) via NOTCH3 testing and CNS vasculitis. Conclusions This case demonstrates the complexity of differentiating overlapping pathologies, specifically PFO, CADASIL, and CNS vasculitis. While MRI confirmed multifocal infarcts and microhaemorrhages, recurrence despite therapy suggests PFO-related-embolism may not be the sole cause. Future management relies on NOTCH3 testing for CADASIL and utilizing RoPE/PASCAL scores to determine the necessity of PFO-closure within a multidisciplinary framework. Conflict of interest Nothing to Disclose