Sentinel Headache Two Days Before Onset of Subarachnoid Hemorrhage (Left Vertebral Artery Dissection): A Case Report

This record provides the official English translation of the case report originally published on Jxiv. The study documents a sentinel occipital headache that occurred two days before the onset of subarachnoid hemorrhage caused by left vertebral artery dissection. Sentinel headache prior to subarachnoid hemorrhage has been described in previous literature, but cases with precise chronological documentation are rare. In this case, the prodromal occipital pain was objectively recorded in an official medical certificate issued by a secondary emergency hospital, and the patient also recalled multiple intermittent episodes of similar headache occurring over several months to approximately one year before onset. The availability of both objective documentation and long-term pre-onset recollection provides clinically meaningful insight into the early phase of vertebral artery dissection, including the potential progression of micro-dissection. This English version preserves the structure, content, and clinical significance of the original Japanese report and is intended for international accessibility and citation.