A Case of Wallenberg Syndrome Presenting With Thunderclap Headache and Delayed Diagnosis Due to Negative Findings on Two MRI Examinations.

Wallenberg syndrome is a lateral medullary infarction characterized by various neurological symptoms, including sensory disturbances, vestibular symptoms, and autonomic dysfunction. However, its initial presentation can vary, and the possibility of false-negative magnetic resonance imaging (MRI) findings can make diagnosis challenging. We report the case of a 65-year-old woman who developed a sudden, severe frontal headache and presented to the emergency department 2 hours later. She complained of headache accompanied by nausea; however, no other neurological abnormalities were observed. An initial brain MRI and a follow-up MRI performed 8 hours later showed no abnormalities; however, her headache persisted, and she developed vertigo, right facial sensory disturbance, and dysphagia, prompting reevaluation. MRI revealed an acute infarction in the right lateral medulla, leading to a diagnosis of Wallenberg syndrome. Throughout the course, no findings suggestive of vertebral artery dissection were observed. The patient was treated with dual antiplatelet therapy and continued rehabilitation. Due to persistent dysphagia, she was transferred to a rehabilitation hospital on the 27th hospital day. This rare case suggests that thunderclap headaches can be an initial manifestation of Wallenberg syndrome. Furthermore, our case highlights that even if the initial MRI is negative, Wallenberg syndrome should be considered in the differential diagnosis, particularly in patients with progressive neurological symptoms.