Introduction: This case reviews a patient with moyamoya disease, a rare cause of altered mental status. It highlights the importance of maintaining clinical suspicion for uncommon causes of common presentations.

Case Report: A 64-year-old male presented with seizures and persistent altered mental status. Computed tomography demonstrated findings consistent with bilateral ischemia. Cerebral angiography was performed with no thrombus identified but moyamoya disease present.

Conclusion: Although rare, moyamoya should be considered as a potential cause of patients presenting with altered mental status. The case presented also highlights the importance of avoiding common diagnostic biases.