Cryptogenic Near-Complete Left Internal Carotid Artery Occlusion in a 20-Year-Old Male: A Diagnostic and Pharmacological Challenge.

Background Large vessel occlusions (LVO), particularly those involving the internal carotid artery (ICA), are exceedingly rare in young adults. These events typically prompt aggressive screening for underlying prothrombotic and metabolic disorders. Case presentation A 20-year-old male presented with severe headache, slurred speech, right-sided seizures, and hemiplegia. Magnetic Resonance Angiography (MRA) identified a near-complete occlusion of the intracranial segments of the left ICA. Despite the severe cerebrovascular event, comprehensive screening for metabolic and hypercoagulability factors remained unremarkable, which notably included a strictly normal baseline serum homocysteine level of 6.67 µmol/L. The patient was successfully managed with aggressive dual antithrombotic therapy alongside empirical folic acid supplementation. During regular clinical follow-ups every 2 months over a 2-year period, the patient demonstrated significant neurological recovery without any recurrent ischemic events. Conclusion This case underscores the diagnostic challenges associated with cryptogenic LVOs in young adults. It emphasizes the likelihood of spontaneous arterial dissection when metabolic anomalies are absent. Furthermore, the case discusses the pharmacological rationale for utilizing empirical metabolic interventions in cases of unexplained early-onset stroke.