Migraine is a complex neurological disorder classified as a primary headache condition, meaning the headache itself is the disease rather than a symptom of another medical problem. There is no single, definitive diagnostic test, such as a blood test or a scan, that can confirm a migraine diagnosis. The diagnosis relies entirely on a comprehensive clinical assessment where a healthcare provider analyzes a patient’s medical history and current pattern of symptoms. This process recognizes a recurrent pattern of specific neurological symptoms that meet established criteria for a migraine attack.
Recognizing the Specific Signs of a Migraine
Migraine attacks are distinct from common headaches and typically progress through four potential phases: prodrome, aura, attack, and postdrome. The prodrome phase can begin hours or days before the head pain starts, involving subtle changes like neck stiffness, fatigue, mood changes, or increased thirst and yawning.
The aura phase follows for about a third of individuals, presenting as transient, reversible nervous system symptoms. Visual disturbances are the most common, such as bright spots, flashes of light, or zig-zag lines, but aura can also include sensory symptoms like “pins-and-needles” or difficulty speaking. Aura symptoms typically last between 5 and 60 minutes.
The main attack phase usually lasts between four and 72 hours if left untreated. The pain is often moderate to severe, with a pulsating or throbbing quality, and frequently affects one side of the head.
During the attack, associated symptoms are prominent, including nausea, sometimes with vomiting, and hypersensitivity to light (photophobia) and sound (phonophobia). After the pain subsides, the postdrome phase, often called the “migraine hangover,” can leave a person feeling drained, fatigued, and unable to concentrate for up to a day or more.
The Clinical Criteria Used for Diagnosis
A formal diagnosis of migraine is made by a healthcare professional by matching a patient’s reported symptoms to established guidelines, primarily the International Classification of Headache Disorders, 3rd edition (ICHD-3). This system requires a history of recurrent episodes that meet specific criteria for frequency, duration, and symptom profile. For instance, a diagnosis of migraine without aura typically requires at least five lifetime attacks lasting 4 to 72 hours.
These attacks must exhibit at least two of four specified pain characteristics: unilateral location, pulsating quality, moderate or severe intensity, and aggravation by or causing avoidance of routine physical activity. Additionally, the attack must be accompanied by at least one non-headache symptom, such as nausea and/or vomiting, or both photophobia and phonophobia.
The ICHD-3 criteria are used to distinguish migraine from other primary headache disorders, such as tension-type headaches, which do not include nausea or vomiting as diagnostic features. The clinician’s role involves collecting a detailed history to confirm this pattern of recurrent episodes. The criteria help ensure the patient’s symptoms are not better explained by another diagnosis.
Diagnostic Tests to Rule Out Other Conditions
While there is no positive test for migraine, medical imaging and laboratory work are sometimes ordered to exclude secondary headaches. Secondary headaches are those caused by an underlying structural or systemic issue, such as a brain tumor, aneurysm, infection, or hemorrhage. Tests like Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans are not used to confirm a migraine but rather to ensure a potentially serious cause is not being missed.
A healthcare provider looks for “red flag” symptoms that suggest the need for immediate imaging. These include the sudden onset of the “worst headache of life” (thunderclap headache), a new headache occurring after age 50, or a headache accompanied by fever, stiff neck, or new neurological signs like weakness or difficulty with coordination.
In the absence of these warning signs and with a clear history of stable, recurrent migraine symptoms, imaging is generally not necessary. If imaging is performed, MRI is typically preferred over CT because it offers a more detailed view of brain tissue and does not involve radiation exposure. The primary purpose of these tests remains one of exclusion, serving as a safety measure to rule out life-threatening conditions.
The Importance of Symptom Tracking
Because migraine diagnosis relies entirely on clinical history and symptom patterns, patients must track their episodes. A detailed migraine diary provides the objective data necessary for a physician to apply the clinical diagnostic criteria accurately. Key information to record includes:
- The date, time of onset, total duration, and severity rating of the attack.
- Specific characteristics of the pain (e.g., pulsating or pressing) and its location.
- All associated symptoms, including nausea, vomiting, and sensitivity to light or sound.
- Potential triggers, such as sleep patterns, specific foods, or menstrual cycles.
- The use and effectiveness of any medications.
This detailed record allows the healthcare provider to confirm the recurrent nature of the condition and formulate an effective, personalized treatment plan.