Hemiplegic Migraine — The Migraine That Mimics a Stroke

1. What Is Hemiplegic Migraine?

Hemiplegic migraine (HM) is a rare type of migraine with aura (reversible neurological symptoms that precede or accompany the headache) where individuals experience temporary motor weakness, known as hemiplegia, on one side of the body as part of their attack ¹. This weakness can range from mild difficulty with coordination to complete paralysis of the affected side. It is always accompanied by at least one other typical aura symptom, such as visual disturbances, sensory changes (like tingling or numbness), or difficulty with speech ¹.

This condition is fundamentally a neurological disorder, driven by genetic factors that affect how brain cells communicate with each other, specifically through structures called ion channels ². It is not a psychological condition or a sign of underlying structural brain damage in most cases.

Plain Language Section

Hemiplegia: Temporary one-sided weakness. Aura: Reversible warning symptoms like vision changes.

Why It’s One of the Most Misunderstood Migraine Types

The dramatic and alarming nature of the body weakness often leads to confusion and misdiagnosis. When a person presents to an emergency department with one-sided paralysis and slurred speech, the immediate and appropriate focus is to rule out a stroke or a transient ischaemic attack (TIA), which is a “mini-stroke” where blood flow to part of the brain is briefly blocked. Because hemiplegic migraine is rare—estimated to affect approximately 1 in 10,000 people based on the landmark Danish epidemiological survey—many frontline doctors may not be familiar with it, leading to diagnostic delays and significant anxiety for the patient and their family ³.

The Urgency of Proper Diagnosis

A correct diagnosis is crucial for two main reasons. Firstly, it provides peace of mind and an explanation for what can be terrifying symptoms. Secondly, and more importantly, it guides appropriate treatment. Some medications used for other types of migraine are contraindicated (not recommended) in hemiplegic migraine due to a theoretical concern they could worsen blood flow issues in the brain ¹⁷. An accurate diagnosis ensures patients receive safe and effective care tailored to their specific condition, moving them away from repeated, stressful emergency room visits and towards a proactive management plan.

2. What Happens During a Hemiplegic Migraine?

An attack of hemiplegic migraine typically unfolds in stages, with the neurological aura symptoms appearing first, often followed by a headache. The progression and combination of symptoms are key to its diagnosis.

Key Symptoms: Temporary Paralysis or Weakness on One Side

The defining feature is fully reversible motor weakness ¹. This weakness often starts in the hand and arm and can gradually spread to the face and leg on the same side over minutes to hours. This gradual progression, known as the “migraine march,” is a key feature that helps distinguish it from a stroke, where symptoms are typically sudden and maximal at onset ².

Other Neurological Symptoms: Vision, Speech, and Confusion

In addition to weakness, at least one other aura symptom must be present for a diagnosis. These include ¹:

• Visual disturbances: This is the most common aura symptom. It can include positive phenomena (seeing things that aren’t there) like flashing lights, zig-zag lines (fortification spectra), or shimmering spots, as well as negative phenomena like blind spots (scotoma) or temporary loss of vision in part of the visual field.
• Sensory symptoms: Numbness or a pins-and-needles sensation (paraesthesia) that often starts in the fingers and spreads up the arm to the face before the weakness begins.
• Speech difficulties: This can manifest as dysarthria (slurred or difficult-to-understand speech due to muscle control issues) or aphasia (difficulty finding words, understanding language, or forming sentences).

In severe attacks, individuals may also experience confusion, drowsiness, memory problems, or even a decreased level of consciousness that can mimic more severe neurological emergencies ⁴.

Often Misdiagnosed as Stroke or TIA

The similarity of symptoms to a stroke cannot be overstated. Anyone experiencing these symptoms for the first time must seek immediate emergency medical attention by calling 000. A thorough neurological work-up, including brain imaging, is essential to exclude a stroke. Only once other serious causes have been ruled out can a diagnosis of hemiplegic migraine be considered ⁴.

3. Types of Hemiplegic Migraine

Hemiplegic migraine is classified into two main types based on whether it runs in the family. The underlying biology and symptoms are the same; the classification only reflects the inheritance pattern.

Familial Hemiplegic Migraine (FHM)

In Familial Hemiplegic Migraine (FHM), the person has at least one first-degree (parent, sibling, child) or second-degree (grandparent, aunt/uncle) relative who also has a confirmed diagnosis of hemiplegic migraine ¹. FHM is an inherited genetic disorder caused by specific mutations that are passed down through families. To date, three main genes have been identified as primary causes of FHM, and genetic testing can often confirm the diagnosis in these families ⁵.

Sporadic Hemiplegic Migraine (SHM)

In Sporadic Hemiplegic Migraine (SHM), the person experiences all the symptoms of hemiplegic migraine but has no known family history of the condition ¹. It is believed that SHM is often caused by a new, spontaneous genetic mutation (called a de novo mutation, meaning it is new in the individual and not inherited from their parents). In other cases, the genetic cause remains unknown, suggesting that more genes related to hemiplegic migraine are yet to be discovered ².

What’s the Difference?

From a clinical perspective, there is no difference between FHM and SHM. The symptoms, the experience of an attack, the diagnostic process, and the management approaches are the same. The distinction is purely genetic and is used to guide family counselling and, in some cases, the search for a causative gene.

4. Symptoms in Detail

Understanding the specific characteristics of each symptom can help patients and doctors distinguish HM from other conditions.

Motor Weakness or Paralysis (Hemiplegia)

The one-sided weakness is the hallmark of this condition and must be present for a diagnosis ¹. It is always fully reversible, though the recovery time can vary. The weakness can be subtle, manifesting as clumsiness or heaviness, or it can be a complete paralysis (plegia) where the person cannot move their limb at all. It can affect fine motor skills, like writing or buttoning a shirt, as well as gross motor movements, like walking or lifting an arm.

Aura Symptoms: Visual, Sensory, and Speech Disturbances

Aura symptoms typically begin before the motor weakness and headache. The sequence often follows a characteristic “migraine march,” where symptoms evolve one after another over 5 to 60 minutes each ⁶. A common pattern is:

1. Visual aura begins first.
2. Sensory aura (tingling/numbness) follows, often “marching” up the limb.
3. Aphasic aura (speech difficulty) may develop next.
4. Motor aura (weakness) is often the last of the aura symptoms to appear.

Headache Phase: May Follow or Be Absent

A severe, throbbing headache, often on the opposite side of the head from the weakness, usually follows the aura phase. However, in some cases, the headache can be mild or even entirely absent. Nausea, vomiting, and extreme sensitivity to light (photophobia) and sound (phonophobia) are common during the headache phase, similar to other forms of migraine.

Duration and Recovery

According to the ICHD-3, the motor symptoms of an attack “generally last <72 hours; in some patients may persist for weeks” ¹. Most attacks resolve within 24-72 hours. However, prolonged attacks are possible, and full recovery of motor strength may take longer. While most people recover completely without lasting effects, severe and frequent attacks are associated with a small risk of long-term problems, underscoring the importance of preventive treatment ⁷.

5. What Causes Hemiplegic Migraine?

Hemiplegic migraine is primarily a genetic disorder affecting the brain’s “ion channels”—tiny pores on the surface of nerve cells (neurons) that control the flow of electrically charged particles (ions) like calcium and sodium. This control of electrical signals is fundamental to all brain function.

Genetic Mutations (CACNA1A, ATP1A2, SCN1A)

Decades of research have identified three main genes responsible for most identified cases of FHM ⁵:

• FHM1: Caused by mutations in the CACNA1A gene. This gene provides instructions for a calcium ion channel. Mutations here are thought to make it easier for neurotransmitters (chemical messengers) to be released in the brain, leading to hyperexcitability.
• FHM2: Caused by mutations in the ATP1A2 gene. This gene affects a vital cellular machine called the sodium-potassium pump, which is critical for cleaning up chemicals from around nerve cells after they fire. A faulty pump leads to a build-up of chemicals that can make brain cells overactive.
• FHM3: Caused by mutations in the SCN1A gene. This gene controls a sodium ion channel, which is essential for initiating the electrical signals in neurons. Mutations here can make it easier for nerve cells to fire, again leading to a state of hyperexcitability.

These mutations all lead to a common outcome: they make the brain more susceptible to a phenomenon called Cortical Spreading Depression (CSD) ¹⁰. It is important to note that a large-scale genetic study (an exome-wide study, which looks at all protein-coding genes) from the UK Biobank found that, in the general population, carrying a variant in one of these genes was associated with migraine, but not with an increased risk of epilepsy ⁸.

Triggers

Like other migraine types, HM attacks can be set off by certain triggers. Identifying and managing these is a key part of prevention. For more on this, see our page on avoiding migraine triggers. Common triggers include:

• Stress: Both emotional and physical stress are very common triggers.
• Minor head trauma: For some people with HM, even a slight knock to the head can trigger a severe episode.
• Sleep changes: Both too much and too little sleep can be a trigger.
• Certain foods or smells.
• Hormonal fluctuations in women, particularly around menstruation.

The Role of Cortical Spreading Depression

The underlying biological mechanism for migraine aura is believed to be Cortical Spreading Depression (CSD). This is a slow-moving wave of intense nerve cell activity, followed by a period of suppressed activity, that spreads across the surface of the brain (the cortex) at a rate of about 3-5 mm per minute ⁹. In hemiplegic migraine, the genetic mutations make it much easier for CSD to be triggered and to spread. As this wave moves across different functional areas of the brain, it causes the progressive symptoms of the aura:

• When it crosses the visual cortex, it causes visual disturbances.
• When it crosses the somatosensory cortex, it causes tingling and numbness.
• When it crosses the motor cortex, it causes the temporary weakness or paralysis seen in an attack ¹⁰.

6. Hemiplegic Migraine vs. Stroke

Symptom Similarities and Differences

The overlap in symptoms is significant, which is why a stroke must always be ruled out first. The following table highlights key differences that doctors look for.

Why Immediate Evaluation Is Necessary

Because a stroke is a true medical emergency where “time is brain” and every minute counts, you should never try to self-diagnose. Always call for an ambulance and go to the hospital if you or someone else experiences sudden one-sided weakness, numbness, or speech difficulty, even if you have a known diagnosis of hemiplegic migraine. Doctors need to perform urgent tests to confirm that the event is not a stroke.

When It’s Safe to Suspect Migraine — and When It’s Not

Once a person has a confirmed diagnosis of hemiplegic migraine and has experienced several typical attacks, they and their doctor may become more comfortable identifying a recurrent episode and make a migraine management plan together. However, any change in the pattern, severity, or duration of symptoms—or the appearance of new symptoms like fever or neck stiffness—should prompt an immediate medical review.

7. Getting a Diagnosis

Diagnosing hemiplegic migraine is a process of “diagnosis of exclusion,” meaning doctors must first meticulously rule out other serious conditions that can mimic its symptoms.

Medical History and Symptom Pattern

A detailed description of the attacks is the most important tool for diagnosis. Your doctor will ask about the precise sequence of symptoms, their duration, and how they progress. Keeping a detailed diary of your attacks is invaluable. For more on this, visit our page on headache and migraine diaries.

Family History and Genetic Testing

Your doctor will take a detailed family history, asking about migraine and other neurological conditions in your parents, siblings, and other relatives. As mentioned, genetic testing is available for the three main FHM genes and can confirm a diagnosis in many families. However, genetic testing does not always detect an abnormality in one of the known genes, as other genes are likely involved ⁵. In Australia, genetic testing is a specialised service and is generally not covered by the PBS (Pharmaceutical Benefits Scheme) or Medicare; it is often performed through academic research centres or private specialist genetic services.

Neurological Exams, Imaging, and Rule-Outs

• Neurological Examination: A doctor will perform a full neurological exam during an attack to assess the extent of the weakness and other deficits, and also between attacks to ensure there are no lasting problems.
• Brain Imaging: An MRI or CT scan of the brain is essential during a first-ever attack to rule out a stroke, tumour, inflammation, or other structural brain problem.
• Other Tests: An EEG (electroencephalogram), a test that measures electrical activity in the brain, may be used to rule out seizure activity, which can sometimes present with similar symptoms. Blood tests are also standard to check for metabolic or inflammatory causes.

8. Treatment and Management

Management of HM is twofold: treating acute attacks when they occur and, most importantly, implementing a preventive strategy to reduce their frequency and severity.

Acute Treatments: What Can and Cannot Be Used

Treating the acute phase of a hemiplegic migraine attack is complex. See our page on acute medications for general information.

What is Contraindicated: Triptan medications (e.g., sumatriptan, rizatriptan) are contraindicated in hemiplegic migraine according to Australian product information ¹¹. This is based on their blood-vessel-constricting (vasoconstrictive) mechanism and a long-standing theoretical concern that they could increase the risk of stroke, although real-world data on this risk is limited ¹⁷. Ergotamine medications are also avoided for similar reasons.

What Can Be Used: Simple pain relievers like paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs – e.g., ibuprofen, naproxen) may help the headache. Anti-nausea medications are often used. In a hospital setting, intravenous medications may be required for severe, prolonged attacks.

Preventive Medications

The primary goal of treatment is prevention. This can reduce attack frequency and severity, improve quality of life, and may prevent long-term complications ⁷.

For Adults:

• First-line options: Medications that stabilise nerve cell activity are often used. These include calcium channel blockers (like verapamil) and certain anti-epileptic drugs (like topiramate, valproate, or lamotrigine) ².
• Emerging Therapies: Newer migraine-specific preventive treatments that target the CGRP (calcitonin gene-related peptide – a key chemical messenger in migraine pain) pathway are supported by case reports in hemiplegic migraine. While promising, the evidence for these drugs in HM remains limited, and their use requires specialist oversight ¹².
• Australian Healthcare Coverage: In Australia, CGRP monoclonal antibodies (fremanezumab, galcanezumab, and eptinezumab) are available on the PBS for chronic migraine (15 or more headache days per month). Their prescription requires an Authority Required (Streamlined) script, and treatment must be initiated by a neurologist, though a GP can continue prescribing in consultation with the specialist. Patients must have failed treatment with at least three other oral preventive medications to be eligible ¹³.
• Botulinum toxin (Botox): For people with hemiplegic migraine who also meet the criteria for chronic migraine, injections of onabotulinumtoxinA may be an effective preventive option. It is subsidised by the PBS under specific criteria established by the MSAC (Medical Services Advisory Committee), an independent committee that evaluates new medical services for government funding ¹⁴.

For Children: Treatment for children with hemiplegic migraine follows similar principles, but medication choices and dosages must be carefully managed by a paediatric neurologist (a doctor who specialises in brain and nervous system disorders in children). Lifestyle and trigger management are especially important first steps.

Non-Drug Approaches: Lifestyle, Diet, Stress Management

• Identify and Manage Triggers: Keep a detailed diary to identify patterns. For more on this, see our page on avoiding migraine triggers.
• Maintain a Regular Schedule: Consistent sleep, meals, and hydration are key pillars of migraine prevention.
• Manage Stress: Techniques like mindfulness, biofeedback, and cognitive-behavioural therapy (CBT) can be very effective.
• Australian Healthcare Support: In Australia, your GP can prepare a GP Chronic Condition Management Plan (GPCCMP). Under the framework effective from July 2025, this plan provides Medicare rebates for up to five appointments with allied health professionals (such as a physiotherapist, psychologist, or dietitian) per calendar year ¹⁵.

9. Living with Hemiplegic Migraine

Impact on Work, Driving, and Daily Life

Living with an unpredictable and disabling condition can have a major impact on education, work, and social life. The need to avoid triggers might mean significant lifestyle adjustments.

Regarding driving, Australian drivers must follow the national Assessing Fitness to Drive standards. These guidelines state that for conditions causing sudden impairment, a person must be assessed by their doctor. Notification requirements for your licence are enforced by state and territory authorities. You must discuss your specific situation with your doctor and may need to notify your local licensing authority ¹⁶.

Safety Considerations During an Episode

During an attack, the person’s safety is the top priority. They may be confused or unable to move, so it’s important to ensure they are in a safe place where they cannot fall or injure themselves. Having a clear, written action plan is invaluable. This should include emergency contact information, a letter from a neurologist explaining the diagnosis, and clear instructions for family or colleagues on when to call for an ambulance.

Supporting Children or Family Members with FHM

For families with FHM, it can be deeply distressing to watch a loved one, especially a child, go through an attack. Providing a calm, reassuring, and supportive environment is key. Educating schools and workplaces about the condition is vital for creating an accommodating and understanding atmosphere. An individualised healthcare plan should be developed with the child’s school.

10. Myths and Misunderstandings

No, It’s Not “Just a Migraine”

Hemiplegic migraine is far more than a bad headache. It is a serious neurological event. The term “migraine” can sometimes lead to the condition being downplayed or dismissed, but the motor and neurological symptoms are profound and temporarily disabling.

Why Weakness and Paralysis Are Real — and Reversible

The weakness is not a psychological reaction or “in your head”; it is a real physical event caused by a temporary disruption of brain function (CSD). Emphasising to friends, family, and even healthcare providers that the symptoms, while frightening, are reversible is crucial for fostering understanding and appropriate responses.

Challenges with Medical Recognition and Response

Because it is rare, patients may encounter healthcare providers who are unfamiliar with hemiplegic migraine. This can lead to repeated, stressful, and sometimes dismissive emergency evaluations. Carrying clear information about your diagnosis, such as a neurologist’s letter, a copy of the ICHD-3 criteria, or wearing a medical alert bracelet, can facilitate better and faster care.

11. Prognosis and Long-Term Outlook

Recovery From Attacks

The vast majority of individuals recover fully from each attack with no lasting damage. The frequency of attacks can vary widely between individuals and over a person’s lifetime, from a few attacks in a lifetime to several per month.

Risk of Permanent Deficits (Rare)

While the symptoms of an attack are, by definition, fully reversible, there are very rare reports of patients experiencing permanent neurological problems, such as cognitive issues or problems with coordination (ataxia), following exceptionally severe or frequent attacks ⁴. Some imaging studies have shown that severe attacks can be associated with brain swelling that, over many years, may lead to brain atrophy (shrinkage) ⁷. This highlights why effective preventive treatment is so important.

Will It Get Better Over Time?

The natural course of hemiplegic migraine can change over a person’s lifetime. For many, but not all, the frequency and severity of attacks tend to decrease with age, particularly after 50. However, this is not guaranteed, and proactive management remains essential throughout life.

12. Conclusion

Raising Awareness of a Rare Migraine Type

Hemiplegic migraine is a challenging and often frightening disorder that remains poorly understood by the public and even within parts of the medical community. It is a stark reminder that migraine is not just a headache but a complex neurological disease. Raising awareness is essential for ensuring people receive a swift, accurate diagnosis and the appropriate care they need.

Advocating for Better Recognition and Treatment

As research continues to unravel the genetic and molecular basis of hemiplegic migraine, new and more targeted treatments are on the horizon. At Headache Australia, we advocate for continued research, improved access to genetic testing, and better coverage for advanced treatments for all Australians living with severe and disabling migraine disorders.

What to Do If You Suspect Hemiplegic Migraine

• Seek Urgent Medical Care: If you or someone you know experiences one-sided weakness for the first time, treat it as a medical emergency and call 000.
• Consult a Neurologist: A neurologist with expertise in headache medicine is the best person to diagnose and manage this condition.
• Keep a Symptom Diary: Track your attacks in detail to help your doctor understand your condition. See our guide to headache and migraine diaries.
• Connect for Support: You are not alone. Headache Australia provides resources and information to help you navigate your journey.

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