The Spiked Helmet Sign: A Concerning Electrocardiographic Finding.

We present the case of an 18-year-old man, with a history of subarachnoid hemorrhage, who is found to have the spiked helmet sign on electrocardiogram during a hospital admission for severe respiratory infection. The spiked helmet sign is a poorly understood electrocardiographic finding that mimics other electrocardiographic pathologies, and is associated with critical illness and high mortality. (Level of Difficulty: Beginner.).