USMLE Guide: Migraine

Introduction

This USMLE guide aims to provide a comprehensive overview of migraine, including its pathophysiology, clinical presentation, diagnosis, and management. Migraine is a common neurological disorder characterized by recurrent headaches that can be debilitating for affected individuals. Understanding the key aspects of this condition is crucial for medical professionals, especially those preparing for the USMLE exams.

I. Pathophysiology

Migraine is believed to involve a combination of genetic, environmental, and neurovascular factors. The primary pathophysiological mechanisms include:

• Cortical spreading depression (CSD): A wave of neuronal depolarization spreads across the cerebral cortex, accompanied by changes in cerebral blood flow and neuroinflammatory responses.
• Neurogenic inflammation: Activation of trigeminal sensory fibers leads to the release of vasoactive peptides (e.g., calcitonin gene-related peptide) causing vasodilation, plasma extravasation, and activation of pain pathways.

II. Clinical Presentation

The clinical presentation of migraine can vary among individuals, but the following features are commonly observed:

• Headache: Typically unilateral, pulsating, moderate to severe intensity, aggravated by routine physical activity, and lasts 4-72 hours.
• Associated symptoms: Nausea, vomiting, photophobia (sensitivity to light), phonophobia (sensitivity to sound), and osmophobia (sensitivity to smells) are often present.
• Premonitory symptoms: Prodromal phase may include mood changes, food cravings, neck stiffness, or increased yawning.

III. Diagnosis

The diagnosis of migraine is primarily clinical, based on the patient's history and symptomatology. However, specific criteria are outlined by the International Headache Society (IHS) for a definitive diagnosis of migraine, which include:

• At least five attacks fulfilling the following criteria:
  • Headache lasting 4-72 hours (untreated or unsuccessfully treated).
  • Headache having at least two of the following characteristics:
    • Unilateral location.
    • Pulsating quality.
    • Moderate or severe pain intensity.
    • Aggravation by routine physical activity.
  • During headache, at least one of the following:
    • Nausea and/or vomiting.
    • Photophobia and phonophobia.
  • Not better accounted for by another diagnosis.

IV. Management

The management of migraine involves both acute treatment for relieving symptoms during an attack and prophylactic measures to reduce the frequency and severity of future attacks. The main strategies include:

• Acute treatment options:
  • Analgesics: Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen sodium, are commonly used for mild to moderate attacks.
  • Triptans: Selective serotonin receptor agonists (e.g., sumatriptan) are effective for moderate to severe attacks.
  • Antiemetics: Drugs targeting nausea and vomiting, such as metoclopramide or prochlorperazine, can be added to the treatment regimen.
• Prophylactic treatment options:
  • Beta-blockers: Propranolol or metoprolol are often used as first-line agents.
  • Antiepileptic drugs: Valproic acid or topiramate can be considered for individuals with frequent or severe attacks.
  • Calcium channel blockers: Flunarizine is sometimes used as an alternative prophylactic agent.

Conclusion

Migraine is a complex neurological disorder with a significant impact on patients' quality of life. Understanding its pathophysiology, clinical presentation, diagnostic criteria, and management options is essential for medical professionals. This USMLE guide aims to provide a concise yet comprehensive overview, assisting students in preparing for the exam while enhancing their knowledge of this common condition.