Individuals with recurring or severe head pain often wonder if advanced imaging, such as a Magnetic Resonance Imaging (MRI) scan, is necessary. The primary goal in evaluating headaches is to distinguish between a benign primary headache, which is not caused by an underlying structural problem, and a secondary headache, which is a symptom of another condition requiring urgent attention. Understanding the signs that indicate a possible structural issue determines when a physician should order an MRI.
Common Headaches That Do Not Require Imaging
The vast majority of headaches experienced by the general population are classified as primary headaches, meaning they are not the result of a separate medical issue. These types, including migraine and tension-type headaches, are typically diagnosed based on a detailed medical history and a neurological examination. Imaging is generally not required if the physical examination is normal and symptoms meet the established criteria for a primary headache disorder.
Tension-type headaches (TTH) are the most common form of primary headache, characterized by mild-to-moderate, non-pulsating pain that feels like a tight band around the head. Migraines cause moderate-to-severe throbbing pain, often on one side, and are frequently accompanied by sensitivity to light and sound, and sometimes nausea. Cluster headaches are also a primary disorder, involving multiple severe daily headaches.
These conditions are diagnoses of exclusion; a physician first rules out potentially serious secondary causes through a thorough clinical assessment. For a patient with typical primary headache symptoms and a normal neurological exam, the likelihood of finding a significant abnormality on an MRI is extremely low. Avoiding imaging in these common scenarios prevents unnecessary costs and potential patient anxiety from incidental findings.
Warning Signs Requiring Prompt Medical Imaging
Certain symptoms, referred to as “red flags,” strongly suggest a serious underlying condition, such as a tumor, hemorrhage, or infection, and require immediate medical evaluation and urgent imaging. The most serious is a “thunderclap headache,” which reaches its maximum intensity within one minute of onset. This abrupt, explosive pain is a classic sign of a subarachnoid hemorrhage, a life-threatening condition caused by bleeding around the brain.
A headache accompanied by new neurological deficits also warrants urgent investigation. Deficits include weakness, numbness, difficulty speaking, vision loss, or problems with balance that were not previously present. Any headache that is new and occurs in a patient over the age of 50 is concerning, as is a headache that progressively worsens over days or weeks.
Headaches presenting with systemic symptoms like unexplained fever, neck stiffness, or altered mental status may indicate a nervous system infection, such as meningitis or encephalitis. Furthermore, a new headache following a recent head injury, or one triggered by coughing, sneezing, or straining, raises suspicion for increased intracranial pressure or a structural lesion. Patients with a history of cancer or a weakened immune system who develop a new type of headache also require prompt imaging.
What an MRI Scan Reveals About Headaches
Magnetic Resonance Imaging (MRI) is a non-invasive procedure that uses strong magnets and radio waves to create highly detailed images of the brain and surrounding soft tissues. For headaches, the MRI primarily serves as a tool to rule out structural causes contributing to the pain. It is generally preferred over a Computed Tomography (CT) scan for non-emergent evaluations due to its superior ability to visualize soft tissue and detect subtle abnormalities.
An MRI scan is effective at detecting issues like brain tumors, which appear as masses or lesions affecting surrounding tissue. It can also reveal signs of inflammation, such as in multiple sclerosis, or structural anomalies like vascular malformations and certain types of aneurysms. Specialized MRI techniques can assess blood vessels, helping to diagnose conditions such as venous sinus thrombosis.
An MRI does not diagnose a primary headache disorder like migraine. Migraines and tension headaches are neurological disorders diagnosed clinically. The MRI’s purpose is to confirm that symptoms are not caused by a secondary structural problem that mimics a primary headache. A normal MRI result in a patient with chronic head pain is often reassuring because it indicates the absence of a serious structural disease.
Alternative Imaging and Diagnostic Procedures
While MRI provides detailed structural analysis, other diagnostic procedures are often used, particularly in acute or emergency settings. Computed Tomography (CT) scans use X-rays to create cross-sectional images of the brain. The CT scan is significantly faster than an MRI and is the initial imaging choice in an emergency, especially when a brain bleed is suspected. It is highly sensitive for detecting acute hemorrhage and is also superior for visualizing bone structures.
If a CT scan is negative for hemorrhage but suspicion for a subarachnoid hemorrhage remains high, a Lumbar Puncture (LP), or spinal tap, is often performed next. This procedure involves collecting cerebrospinal fluid (CSF) to check for blood or signs of infection. A lumbar puncture is also a definitive test for diagnosing meningitis. In cases of suspected vascular issues, CT Angiography (CTA), which uses contrast dye and CT technology to visualize blood vessels, may be performed.