, sufferers experience "auras"—shimmering lights, blind spots, or tingling in the limbs that act as a surreal precursor to the pain. The Attack (The Storm): This is the peak, featuring debilitating throbbing (usually on one side of the head), extreme sensitivity to light and sound, and often nausea or vomiting. The Postdrome (The Migraine Hangover): Once the pain subsides, it leaves behind a state of exhaustion and cognitive "fog" that can last for 24 hours. The "Invisible" Burden The unique challenge of episodic migraine is the
Deep Report: What is Episodic Migraine? 1. Executive Summary Episodic Migraine (EM) is a neurological disease characterized by recurrent, disabling headache attacks occurring on fewer than 15 days per month . It is the most common form of migraine, affecting approximately 90% of the migraine population. Unlike its counterpart, Chronic Migraine (CM), EM allows for symptom-free intervals between attacks. However, EM is not merely "occasional headache"; it is a complex, genetically-influenced brain disorder involving neuronal hyperexcitability, vascular changes, and pain pathway dysregulation. Without proper management, a significant subset of patients with EM can transition to Chronic Migraine —a process known as chronification.
2. Definition & Diagnostic Criteria (ICHD-3) According to the International Classification of Headache Disorders, 3rd edition (ICHD-3), Episodic Migraine is defined by specific features, excluding other headache types. Core Criteria (Must meet A through D): A. At least 5 attacks fulfilling criteria B–D (for migraine without aura). B. Headache attacks lasting 4–72 hours (untreated or unsuccessfully treated). C. Headache has at least 2 of the following 4 characteristics:
Unilateral location Pulsating quality (throbbing, like a heartbeat) Moderate or severe pain intensity (inhibits or prohibits daily activity) Aggravation by routine physical activity (e.g., walking stairs) what is episodic migraine
D. During headache, at least 1 of the following :
Nausea and/or vomiting Photophobia (sensitivity to light) and phonophobia (sensitivity to sound)
E. Not better accounted for by another ICHD-3 diagnosis. Key Distinction from Chronic Migraine: It is the most common form of migraine,
Episodic Migraine: Headache days < 15 per month, and migraine days < 8 per month (for >3 months). Chronic Migraine: Headache days ≥ 15 per month, with ≥ 8 migraine days, for >3 months.
3. Pathophysiology: The Biology of an Attack EM is not a vascular disorder but a brain state disorder involving multiple neural networks. 3.1 The "Migraine Generator" — Hypothalamus The hypothalamus (especially the suprachiasmatic nucleus) is now considered the master trigger. It processes homeostatic signals (sleep, hunger, stress, circadian rhythm). Abnormal hypothalamic activation occurs 48–24 hours before the headache phase, explaining prodromal symptoms like yawning, food cravings, or fatigue. 3.2 Trigeminovascular System (TVS) The core pain pathway:
Activation: Cortical spreading depression (CSD) or brainstem triggers release of calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating peptide (PACAP) from trigeminal nerve endings around cranial blood vessels (meninges). Result: Vasodilation, plasma protein extravasation (sterile neurogenic inflammation), and mast cell degranulation. Signal transmission: Pain signals travel via trigeminal nerve → trigeminal nucleus caudalis (brainstem) → thalamus → cortex (somatosensory, insular, cingulate). Serotonin (5-HT): Fluctuates
3.3 Cortical Spreading Depression (CSD) In migraine with aura , CSD is a wave of neuronal depolarization moving across the cortex at 2–6 mm/min, followed by prolonged suppression of neural activity. CSD activates the trigeminovascular system and triggers aura (visual, sensory, or speech disturbances). 3.4 Key Molecules
CGRP: Elevated during EM attacks; infusion of CGRP triggers migraine-like headache in EM patients. Serotonin (5-HT): Fluctuates; drop in synaptic 5-HT may permit CSD and trigeminal activation. Glutamate: Excitatory neurotransmitter implicated in central sensitization.