Unmasking Cerebral Venous Sinus Thrombosis Induced by Vitamin B12 Deficiency.

This is the case of a healthy, 45-year-old right-handed man with no past medical issues who presented with mild drowsiness, language difficulty, right-sided weakness, and headache. Vital signs were unremarkable, and on examination, he was drowsy and found to have expressive aphasia and right upper and lower extremity flaccid paralysis. The patient was found to have cerebral venous thrombosis on imaging, as a result of his vitamin B12 deficiency from a vegan diet. The purpose of this clinical reasoning case is to instruct readers on the localization of symptoms, key imaging findings, approach to the diagnosis and etiologic considerations, and the relevance of biochemistry to the pathophysiology of this case.