This week’s article is more of a common occurrence than most of the others. It is something I have had described, but have not experienced personally. I have been told the pain is so excruciating and sensitivity to sights or sounds are heightened. An individual might form an aura for the duration of the attack, manifesting as a bright light, scent, or hallucination. About 1 in 4 households have someone with this neurological disease; the primary age group are those between the ages of 20 and 50. The World Health Organization ranks this as one of the top 20 most disabling illnesses. If you haven’t guessed already – the topic for this week is migraine.
Migraines are a disorder in the brain involving the vasculature of the CNS. The current understanding for the pathophysiology of a migraine is still a conjecture and requires more research to gain a better understanding. The big players in this pathway include the trigeminal nerve, the Middle Meningeal Artery (MMA) and other cerebral arteries, and the brainstem and cortex of the CNS. The trigeminal nerve is a cranial nerve responsible for receiving sensory signals from the face. The nerve is divided into three branches. One branch specifically, the opthalmic, innervate the upper areas of the skull associated with migraine pain such as the temple and forehead. Activation of the trigeminal nerve leads to the release of neurotransmitter calcitonin gene-related peptide (CGRP) and Neuropeptide Y (NPY) – two proinflammatory molecules. CGRP is a major presence in trigeminal system and is thought to initiate vasodilation of cranial vessels such as MMA. A resulting sensory signal is sent to the brainstem and the cortex for perception of the pain.
Several medications exist which attempt to decrease the nociception and the vasodilation which occur during a migraine. These include triptans, gepants, and glutamate inhibitors. Triptans target 5-HT, a serotonin receptor on cranial blood vessels. Triptan is a 5-HT agonist which increases vasodilation, and inhibits the release of pro-inflammatory molecules such as CGRP. Gepants are CGRP antagonists which act by decreasing vasoconstriction. Lastly, glutamate receptors target the neurons involved in the pathway. Tropiramate is one antagonist which decreases the activation of neurons by decreasing intracellular calcium levels. Low calcium levels does not allow a neuron to depolarize and to continue the signal. The drugs developed attempt to alleviate the pain and vasoconstriction of a person with migraines, but many side effects lead to individuals opting not to take the medications.
Research on migraines has tried to explain the contributing factors of migraines. As is the case with all of the neurological diseases, there is still a need for more research and a better understanding of the mechanisms. The current knowledge is used in the drug therapies for migraines, but there is room for improvement. Individuals with acute migraines may be able to tough it out, but a better quality of life could be obtained for those with chronic migraines with more sound research.
