Cervical carotid artery dissections (CCAD) are common in young adults with a mean age of 44 years and may account for as many as 20% of strokes in patients younger than 30 years. Trauma and primary diseases of the arterial wall such as fibromuscular dysplasia are the main predisposing factors. Some CCAD cases are diagnosed solely on clinical history and physical examination, and even imaging tools such as helical/multi-slice computed tomography (CT) and magnetic resonance imaging (MRI) sometimes are not sufficient to reach a diagnosis. We describe the case of an 18-year-old male who presented to our emergency department due to loss of consciousness 18 hours after a car accident. Previously he had been in no acute distress, with fluent speech, and able to follow 3-step commands. Helical CT showed a hypodense lesion in the left-middle cerebral artery territory, as well as hyperdensity of the M1 segment of the middle cerebral artery. Cerebral angiography depicted the left carotid artery dissection in the C1 segment. Physicians should consider this entity in "asymptomatic" patients during their first hours after head injury, among patients who later develop focal neurological symptoms and clinical deficits. Clinical suspicion followed by radiological findings allows early neurovascular treatment, trying to save viable brain tissue in the first hours post injury.