Herpes Zoster Ophthalmicus Initially Diagnosed As Cluster Headache, Complicated by Delayed Eruption.

Herpes zoster ophthalmicus (HZO) manifests as a consequence of the reactivation of the Varicella-zoster virus (VZV) and primarily affects the ophthalmic division of the trigeminal nerve. Identification of the vesicular eruption is central to the diagnostic process; however, the delayed manifestation of this cutaneous phenomenon poses a challenge to timely and accurate diagnosis. This report elucidates the case of a 61-year-old Japanese male with painful trigeminal neuropathy attributed to VZV that was initially diagnosed as cluster headache, mainly due to the delayed cutaneous eruption. Contrary to the expected pattern of cluster headache presentations, there was no discernible fluctuation in headache severity. The transient improvement of symptoms following interventions tailored for cluster headache management, including pure oxygen inhalation and subcutaneous sumatriptan injection, inadvertently contributed to a delay in accurate diagnosis. The importance of distinguishing HZO from cluster headache is emphasized, particularly in cases involving elderly patients or those with persistent cephalo-ophthalmalgia without the characteristic fluctuation of symptoms. In cases where clinical suspicion of HZO is raised, cerebrospinal fluid analysis should be performed. This approach is consistent with the overall goal of facilitating a prompt and accurate diagnosis.