Raeder's Syndrome: An Uncommon Cause of Partial Horner Syndrome Secondary to Petromastoid Inflammation.

We report the case of a 58-year-old woman who initially presented with left-sided headache, facial discomfort, and a partial Horner syndrome affecting her left eye. Imaging revealed inflammatory changes within the petromastoid air cells, consistent with petrous apicitis. The clinical and radiological features were aligned with Raeder's syndrome, the rare cause of painful partial Horner syndrome. This case highlights the importance of early recognition of this uncommon but treatable medical condition.