Which diagnostic test is essential to order for the patient showing signs of a stroke?

For a patient exhibiting signs of a stroke, ordering a CT scan or MRI is essential because these imaging techniques are crucial for diagnosing the type of stroke—whether it is ischemic (caused by a blockage) or hemorrhagic (caused by bleeding in the brain). Timely and accurate imaging can significantly influence treatment decisions, such as the administration of thrombolytics for ischemic strokes, which are most effective when given shortly after symptoms onset.

CT scans are typically the first-line imaging modality used in acute settings due to their availability and speed, allowing for the rapid exclusion of hemorrhagic stroke. An MRI may provide more detailed images and can be used if CT results are inconclusive, but in emergency situations, CT is preferred.

The other diagnostic tests do not provide the necessary information to assess a stroke effectively. X-rays do not visualize brain tissue or blood vessels effectively, ultrasound may be used in certain vascular assessments but is not the primary tool for diagnosing stroke, and ECG monitors heart rhythms which are important but do not directly identify stroke type or location. The priority in an acute stroke assessment is to determine the cause quickly and accurately to guide treatment.