Case of the Week

Background:

• Clinically, migraine headaches are categorized by the presence or absence of an aura phenomenon. While visual auras are most common, patients can also present with motor and sensory aura that can be classified as hemiplegic migraine and may occur sporadically or in individuals with autosomal dominant familial hemiplegic migraine.
• The mechanism of migraine with aura is not completely understood, though current theories suggest an initial neurovascular cortical spreading depression with cortical hypoactivity, vasoconstriction and hypoperfusion causing the aura followed later by vasodilation, and rebound hyperperfusion contributing to headache.
• Due to the dynamic nature of hemiplegic migraine, perfusion imaging plays a key role in diagnosis. Arterial spin-labeling (ASL) is an MR imaging sequence uniquely qualified to assess migraine headache because it is repeatable, allows for absolute quantification of cerebral blood flow, does not require intravenous contrast administration, and lacks ionizing radiation associated with CT and CT perfusion (CTP).

Clinical Presentation:

• According to the International Classification of Headache Disorders, 3^rd Edition, criteria, hemiplegic migraine diagnosis requires:
  • The presence of aura.
  • Fully reversible symptoms (motor weakness and visual, sensory, speech/language symptoms).
  • At least 3 of the following: gradual onset (at least 5 minutes) of at least 1 aura symptom, 2 or more aura symptoms in succession, each individual aura symptom lasts 5–60 minutes, at least 1 aura symptom is unilateral, at least 1 aura symptom is positive, and aura is accompanied, or followed within 60 minutes, by headache.
  • At least 2 attacks fulfilling the above requirements.

Key Diagnostic Features:

• Diagnosis can be made clinically by obtaining a thorough history and physical exam, by a positive family history (familial hemiplegic migraine), and with imaging.
• In the early aura or vasoconstriction phase, MRI may demonstrate unilateral cerebral hypoperfusion on ASL not limited to a specific vascular territory, asymmetric prominence of deoxygenated blood in cerebral veins on SWI, and normal DWI. CTP may demonstrate mild Tmax delay, and increased TTP and MTT in the affected cerebral hemisphere. CTA and MRA may demonstrate narrowing of distal cerebral arteries.
• In the later headache or vasodilation phase, MRI may demonstrate hyperperfusion on ASL and possible mild cerebral cortical edema.
• Patients with history of chronic migraine headaches may demonstrate more than expected T2 hyperintense lesions in the cerebral white matter.

Differential Diagnoses:

• Cerebral ischemia/infarction (search for a culprit flow-limiting stenosis or vessel occlusion on CTA/MRA and evaluate for core infarct and penumbra with CT/CTP and/or MRI/bolus perfusion-weighted imaging with dynamic susceptibility contrast).
• Seizure with Todd paralysis (characteristic presentation, past medical history of seizures/epilepsy, and possible cerebral hyperperfusion during ictus or hypoperfusion after ictus).
• Artifact (ineffective labeling due to susceptibility artifact or vessel tortuosity in the ASL labeling plane can lead to loss of signal)

Treatment:

• Treatment options include the same abortive and preventive medication used for typical migraine with aura, though most cases resolve spontaneously with full recovery.