BACKGROUND Familial hemiplegic migraine (FHM) is a rare type of migraine. Correct diagnosis is challenging for emergency physicians (EPs) due to its variable clinical picture, as well as its lack of diagnostic biological markers. OBJECTIVE To raise awareness among EPs regarding FHM's diverse clinical picture, and to highlight FHM's diagnostic criteria to facilitate an accurate and timely diagnosis of FHM in patients presenting to the emergency department (ED) with indicative symptomatology. METHODS A 24-year-old male student presented to the ED complaining of dizziness, general weakness, and blurred vision that had developed the previous night. The initial physical examination revealed drowsiness, slow speech production, and slight weakness with paresthesia in all limbs. Detailed communication with the patient's aunt revealed that he had experienced several similar attacks since the age of 12 years, and that there was also an extensive family history of the same symptoms. In addition, 2 h after arrival, the patient experienced severe throbbing headache, vomiting, severe dysphasia, and the weakness shifted to the right side. A computed tomography scan of the brain showed no anomalies. He was admitted with a tentative diagnosis of FHM. CONCLUSIONS A diagnosis of FHM should be considered if the patient's clinical features include headache and weakness, with a family history of similar symptomatology. However, atypical symptoms of FHM may present as recurrent episodes of unexplained encephalopathy. Crucial elements for making an accurate and timely diagnosis of FHM include a detailed knowledge of weakness-related diseases and an ability to consider FHM in the differential diagnosis, as well as obtaining a thorough family history with repeated neurologic assessments.