by Dr. Al Al-Alhaidari
What is Migraine?
Chronic migraine, defined as headache occurring more than 15 days a month for more than three months, is rare, affecting only about 3% of the migraine population.
What are the causes and pathophysiology?
Many factors for Migraine and there are multiple explanaitions for Migraine to replace older theories;
Cortical spreading depression — A causal association between migraine aura and headache is supported by evidence that both are linked to the phenomenon known as cortical spreading depression of Leão . Cortical spreading depression is a self-propagating wave of neuronal and glial depolarization that spreads across the cerebral cortex.
Trigeminovascular system — The pathophysiology of migraine involves activation of the trigeminovascular system, which consists of small caliber pseudounipolar sensory neurons that originate from the trigeminal ganglion and upper cervical dorsal roots.
Role of calcitonin gene-related peptide — The calcitonin gene-related peptide (CGRP) has a key role in migraine pathophysiology.
Sensitization — Sensitization refers to the process in which neurons become increasingly responsive to nociceptive and non-nociceptive stimulation: response thresholds decrease, response magnitude increases, receptive fields expand, and spontaneous neuronal activity develops . Peripheral sensitization in the primary afferent neurons and central sensitization within second order neurons in the trigeminal nucleus caudalis and higher order neurons in the central nervous system are thought to play a role within individual migraine attacks and, perhaps, even in the transformation of episodic migraine to chronic migraine.
GENETIC BASIS: Migraine is a syndromic disorder of the brain that is in most instances inherited. As with most common diseases, the genetic basis of migraine is likely to be complex and in some individuals may be based on the additive effect of more than one genetic source.
**MANAGEMENT:**The treatment of chronic migraine should focus on prophylactic therapy while avoiding migraine triggers and limiting the use of acute headache medications so as to avoid medication overuse headache . Prophylactic interventions may include pharmacotherapy, behavioral therapy, physical therapy, and other strategies..
First-line agents — In clinical practice, the same prophylactic medications used for episodic migraine are used for the prevention of chronic migraine. Thus, based mainly upon their efficacy when treating episodic migraine (see "Preventive treatment of episodic migraine in adults") and affordability, first-line prophylactic medications for chronic migraine include:
Second- and third-line agents — For patients with chronic migraine that is refractory to adequate trials of first-line agents, a number of other drugs are potential alternatives, including the following: