Hemiplegic Migraine Diagnostic Criteria
Hemiplegic migraine is diagnosed when a patient has at least two attacks of fully reversible motor weakness (hemiparesis) as an aura symptom, accompanied by at least one other aura type (visual, sensory, or speech), with each aura symptom spreading gradually over ≥5 minutes, lasting 5-60 minutes (though motor symptoms may extend up to 72 hours), and followed by headache within 60 minutes. 1, 2
Core Diagnostic Requirements
The diagnosis follows ICHD-3 criteria for migraine with aura, but specifically requires motor aura as the distinguishing feature 3:
Essential Criteria:
- At least two attacks fulfilling the complete criteria
- Motor weakness (hemiparesis/hemiplegia) that is fully reversible
- At least one additional aura symptom from:
- Visual disturbances
- Sensory symptoms
- Speech/language impairment
- Brainstem symptoms
Temporal Characteristics (at least 3 of 6):
- Aura symptoms spread gradually over ≥5 minutes
- Two or more aura symptoms occur in succession
- Each aura symptom lasts 5-60 minutes (motor symptoms may persist up to 72 hours)
- At least one aura symptom is unilateral
- At least one aura symptom is positive (not just loss of function)
- Aura accompanied by or followed by headache within 60 minutes
Exclusion Requirement:
- Not better accounted for by another ICHD-3 diagnosis or secondary cause
Clinical Subtypes
Familial Hemiplegic Migraine (FHM): At least one first-degree or second-degree relative has identical attacks 4, 5
Sporadic Hemiplegic Migraine (SHM): No first-degree or second-degree relatives with identical attacks 4, 5
Critical Diagnostic Nuances
Duration Variability
While ICHD-3 specifies 5-60 minutes for typical aura symptoms, motor weakness in hemiplegic migraine frequently persists much longer 6. In clinical practice, motor symptoms lasting up to 72 hours are accepted, and some patients experience weakness for days to weeks 7, 6. One tertiary center study found median hemiparesis duration of 24 hours, with 51.6% of patients experiencing at least one episode exceeding 72 hours 6.
Atypical Presentations
Important caveat: The temporal progression of aura symptoms may be atypical in up to 25% of cases 6. Some patients present with motor symptoms that don't follow the classic gradual spread pattern, yet still represent true hemiplegic migraine after exclusion of other causes.
Associated Features That Increase Diagnostic Confidence
- Impaired consciousness during attacks
- Cerebellar ataxia (may be permanent in some genetic forms)
- Brainstem symptoms (diplopia, dysarthria, vertigo, tinnitus)
- Prolonged confusion or altered mental status
- Family history of similar attacks 4, 5
Essential Differential Diagnosis Exclusions
The diagnosis is clinical and requires systematic exclusion of stroke mimics 1, 2, 8, 9:
Must Rule Out:
- Ischemic stroke/TIA - Most critical differential, especially in older patients 8, 9
- Hemorrhagic stroke
- Epilepsy with Todd's paralysis
- Encephalitis
- Metabolic disorders (MELAS, CADASIL)
- Arteriovenous malformations
- Reversible cerebral vasoconstriction syndrome
Diagnostic Workup Strategy:
- Brain MRI (preferred over CT) - typically normal in hemiplegic migraine 1, 2
- CSF analysis if infection/inflammation suspected
- EEG to exclude epilepsy
- Avoid conventional cerebral angiography - contraindicated as it may provoke attacks 5
Genetic Testing Considerations
Three genes are implicated: CACNA1A, ATP1A2, SCN1A (and rarely PRRT2) 7, 1, 4. However, genetic testing can confirm but not exclude the diagnosis, as at least 25% of familial cases and most sporadic cases have no identified mutation 1, 4, 5.
Genetic testing is more likely positive when:
- Extensive weakness beyond typical duration
- Prominent brainstem manifestations
- Associated cerebellar ataxia
- Epilepsy or intellectual disability
- Strong family history 1
Key Diagnostic Pitfalls
Mistaking for stroke: Hemiplegic migraine frequently presents to emergency departments with stroke-like symptoms and elevated NIHSS scores 8, 9. The key is recognizing the pattern of recurrent, stereotyped attacks with full recovery and associated migrainous features.
Dismissing prolonged symptoms: Motor weakness lasting >72 hours doesn't automatically exclude hemiplegic migraine if the pattern is otherwise consistent 6.
Over-relying on imaging: Normal MRI doesn't rule out stroke in hyperacute phase, but in the context of recurrent stereotyped episodes with full recovery, supports hemiplegic migraine 1, 2.
Requiring genetic confirmation: Absence of known mutations doesn't exclude the diagnosis if clinical criteria are met 1, 5.