What Are the Symptoms of Hemiplegic Migraine?
Hemiplegic migraine produces a distinct combination of motor, sensory, visual, and headache symptoms that develop in phases.
A rare and severe subtype of migraine with aura, hemiplegic migraine is characterized by a brief period of one-sided paralysis or weakness (hemiplegia) during the aura phase. The International Headache Society states that less than 0.01% of people in general suffer from hemiplegic migraine (IHS, 2022). Since hemiplegic migraine's transient motor weakness closely resembles a stroke, a timely and precise diagnosis is essential. Hemiplegic migraine can be familial (inherited through genetic mutations) or sporadic (occurring without a family history).
Motor Aura Symptoms
Motor symptoms are the defining feature of hemiplegic migraine and distinguish hemiplegic migraine from all other migraine subtypes.
- Temporary weakness or paralysis on one side of the body, affecting the arm, leg, or face
- Heaviness or difficulty controlling movement on the affected side
- Motor symptoms typically develop gradually over 20 to 30 minutes
- Motor weakness can last from 1 hour to several days in severe cases, significantly longer than other aura types
Visual and Sensory Aura Symptoms
- Zigzag lines, flashing lights, or blind spots in the visual field
- Numbness or tingling starting in the hand and spreading toward the face
- Sensory symptoms typically develop before or alongside motor weakness
Speech and Cognitive Symptoms
- Difficulty finding words or speaking clearly (aphasia)
- Slurred speech
- Confusion or disorientation during the attack
- Difficulty understanding spoken language in some cases
Headache Phase Symptoms
- Moderate to severe throbbing head pain, usually on the side opposite to the motor weakness
- Nausea and vomiting
- Photophobia (sensitivity to light) and phonophobia (sensitivity to sound)
- Headache may be mild or absent in some hemiplegic migraine attacks
Severe Attack Symptoms
In rare and severe cases, hemiplegic migraine can produce additional neurological symptoms.
- Prolonged confusion or altered consciousness
- Fever accompanying the neurological symptoms
- Coma lasting hours to days in extremely rare cases
- These severe symptoms are more common in familial hemiplegic migraine caused by specific genetic mutation
What Causes Hemiplegic Migraine?
Genetic Causes
Familial hemiplegic migraine (FHM) is caused by mutations in specific genes that affect ion channel function (the mechanism by which electrical signals pass between nerve cells) in the brain.
- FHM Type 1: Caused by mutations in the CACNA1A gene, which affects calcium channels in nerve cells. FHM Type 1 is the most common genetic subtype
- FHM Type 2: Caused by mutations in the ATP1A2 gene, which affects sodium-potassium pumps in nerve cells
- FHM Type 3: Caused by mutations in the SCN1A gene, which affects sodium channels and is also associated with epilepsy
- A family history of hemiplegic migraine is present in approximately 50% of cases
Neurological Mechanism
- Hemiplegic migraine is caused by an abnormally prolonged and widespread cortical spreading depression (a slow wave of electrical suppression spreading across the brain cortex)
- The prolonged cortical spreading depression in hemiplegic migraine extends into motor cortex regions, causing the temporary weakness or paralysis that defines the condition
- Elevated CGRP (calcitonin gene-related peptide) levels drive neuroinflammation and amplify the severity of hemiplegic migraine attacks
Common Triggers
- Physical trauma or head injury, even minor
- Emotional stress or sudden emotional shock
- Vigorous physical exertion
- Bright or flickering lights
- Sleep deprivation
- Certain contrast dyes used in imaging
How Is Hemiplegic Migraine Diagnosed?
Hemiplegic migraine is diagnosed clinically based on symptom history and the exclusion of other serious neurological conditions, particularly stroke.
Diagnostic Criteria
- At least two attacks involving fully reversible motor weakness on one side of the body.
- There may be at least one additional aura symptom, such as speech difficulties, sensory abnormalities, or visual disturbances.
- Symptoms that cannot be explained by a stroke, transient ischemic attack, or other neurological disorder
Investigations Required
- Brain MRI: To rule out stroke, bleeding, or structural brain abnormalities during or after an attack
- CT scan: Used in emergency settings to rapidly exclude intracranial bleeding
- Genetic testing: Recommended for individuals with a family history of hemiplegic migraine to identify specific gene mutations
- EEG (electroencephalogram): May be performed to rule out epilepsy, particularly in FHM Type 3
What Are the Risks Associated With Hemiplegic Migraine?
Stroke Risk
- Hemiplegic migraine symptoms closely mimic ischemic stroke (a stroke caused by a blood clot), making misdiagnosis a significant risk
- While hemiplegic migraine itself does not directly cause stroke in most cases, the increased use of vasoconstrictive medications during attacks raises theoretical vascular concerns
- Triptans and ergotamines are generally avoided in hemiplegic migraine due to their vasoconstrictive (blood vessel narrowing) properties
Risk of Permanent Neurological Damage
- In rare cases, prolonged hemiplegic migraine attacks lasting several days are associated with temporary cerebellar atrophy (shrinkage of the cerebellum, the brain region controlling balance and coordination)
- Permanent neurological deficits are extremely rare but have been reported in individuals with frequent severe attacks
Risk of Misdiagnosis
- Hemiplegic migraine is frequently misdiagnosed as stroke, epilepsy, or multiple sclerosis due to overlapping symptoms
- Misdiagnosis leads to inappropriate treatment and delayed access to effective migraine-specific management
- A neurologist experienced in headache disorders should be involved in confirming the diagnosis
How Is Hemiplegic Migraine Treated?
Acute Treatment
- NSAIDs such as ibuprofen and naproxen sodium are used for pain relief during hemiplegic migraine attacks
- Because of its impact on calcium channel function, the calcium channel blocker verapamil is occasionally used acutely.
- In a few studies, intranasal ketamine has been beneficial for severe hemiplegic migraine attacks.
- Due to potential vasoconstrictive risks, triptans and ergotamines are typically avoided; however, some neurologists use triptans cautiously in certain situations.
Preventive Treatment
- Calcium channel blockers such as verapamil and flunarizine are the most commonly used preventive medications for hemiplegic migraine
- Lamotrigine (an antiepileptic medication) is used preventively, particularly in FHM Type 3 associated with SCN1A mutations
- Acetazolamide has shown benefit in some familial hemiplegic migraine cases
- CGRP inhibitors are being investigated for hemiplegic migraine but are not yet standard treatment due to limited clinical trial data in this specific subtype
When Should You See a Doctor?
Seek immediate emergency medical attention if:
- One-sided weakness, paralysis, or speech difficulty occurs for the first time
- Symptoms do not resolve within 60 minutes
- Confusion, altered consciousness, or fever accompanies neurological symptoms
- A severe sudden headache described as the worst headache of life occurs alongside weakness
Seek non-emergency neurological evaluation if:
- Hemiplegic migraine attacks are increasing in frequency or severity
- Current treatments are not adequately controlling attacks
- Genetic counseling is being considered due to a family history of hemiplegic migraine
Conclusion
Hemiplegic migraine is a rare but serious migraine subtype characterized by temporary one-sided motor weakness that closely mimics stroke. Hemiplegic migraine is caused by genetic mutations affecting ion channels in the brain and an abnormally prolonged cortical spreading depression extending into motor regions. Accurate diagnosis, careful exclusion of stroke, and avoidance of triptans and ergotamines are essential management principles. Calcium channel blockers and lamotrigine are the primary preventive options, and all individuals with hemiplegic migraine should be managed by a neurologist experienced in headache disorders.
