To describe a rare case of embolic stroke propagation through a persistent trigeminal artery (PTA) and highlight its clinical relevance in patients with ipsilateral carotid artery disease.

The persistent trigeminal artery is an uncommon embryonic carotid–basilar anastomosis, typically detected incidentally on vascular imaging. In the presence of ipsilateral atherosclerotic disease, however, this variant can create a potential pathway for artery-to-artery embolic migration between anterior and posterior circulations. Recognition of this mechanism is essential for understanding atypical stroke patterns and guiding management.

A descriptive single-patient case report was developed based on clinical presentation, multimodal neuroimaging, and a focused review of the literature.

A man in his sixties with hypertension, prior right middle cerebral artery infarct, and cardiomyopathy with an implantable cardioverter-defibrillator presented with acute left facial droop and dysarthria (NIH Stroke Scale = 4). MRI revealed multifocal infarcts spanning both anterior and posterior territories. CTA of the brain demonstrated a persistent right trigeminal artery and new calcified emboli in the right M3 branches. CTA of the neck showed progression of right internal carotid artery stenosis to 65–70% from 15% one year earlier. No cardiac or vertebrobasilar embolic source was identified. Dual antiplatelet therapy was initiated and vascular surgery consultation obtained for the management of symptomatic carotid disease. The infarcts pattern and absence of alternative etiologies support artery-to-artery embolism via the PTA as the likely mechanism.

This case underscores a rare but clinically meaningful embolic pathway in which a persistent trigeminal artery allows emboli to transfer between circulatory territories in the context of ipsilateral carotid disease. Awareness of such vascular variants is crucial for accurate etiologic attribution and optimal secondary stroke prevention.