External Trigeminal Nerve Stimulation Explained
External trigeminal nerve stimulation, or eTNS, is one type of neuromodulation, which means leveraging electrical, magnetic, chemical and mechanical modalities to target parts of the nervous system implicated in nervous system hyperactivity. Studies show that neuromodulation can reduce pain and episode occurrence for people with recurring migraine and other chronic conditions. eTNS specifically targets the trigeminal nerve, the largest cranial nerve.
What is the role of the trigeminal nerve in migraine?
Hyperactivation of the trigeminal cranial nerve system is the root of almost all cases of migraine, according to the Association of Migraine Disorders.
The trigeminal nerve is a system of three branches controlling sensory and motor functions in the forehead, eyes and upper eyelid, cheeks, lips, nostrils and gums. This nerve system also controls sensations in parts of the mouth and muscles in the jaw used for chewing.
In response to external stimuli such as temperature, pain and touch, the trigeminal nerve sends electrical signals to the brain from the face to enable sensory and motor control.
In people with migraine, the trigeminal nerve system is hyperactivated, and the entire nervous system is also hypersensitive. When overly sensitive trigeminal nerve endings are stimulated by external triggers, electrical signals travel from the nerve endings to the brain stem, linked to the nerves of the brain cortex and the dura, the protective layer that surrounds the brain.
In people with migraine, these electrical signals set off a wave of abnormal synaptic activity in the brain called cortical spreading depression: a period of excitation in cortical neurons, followed by a slowing of this cortical activity.
This wave of activity sets in motion a cascade of effects that cause migraine symptoms. One is vasoconstriction, which temporarily reduces blood flow to the brain, contributing to head pain. Inflammation and swelling of the cortex resulting from CSD also contributes to head pain. Synaptic misfiring also affects the ocular nerve, which causes the odd visual sensations experienced by people who have migraine with aura. Additionally, nerves connected to the gastrointestinal system are impacted, contributing to the nausea felt during a migraine attack.
How does eTNS treat migraine?
eTNS devices apply gentle, electrical pulses to the trigeminal nerve, which extends through the head and face, to regulate nervous system responses that trigger migraine. Though several studies show the efficacy of eTNS and other forms of neuromodulation, scientists are still researching the mechanisms of action on the nervous system.
eTNS sends an electrical current through electrodes placed against the forehead to target the supraorbital branch of the trigeminal nerve, responsible for feeling in the scalp, upper eyelid and forehead. From the supraorbital branch, nerve fibers carry information to regions of the brain stem, specifically the trigeminal nuclei, which processes sensory information from the trigeminal nerve.
When eTNS stimulates the brain stem, it may act positively on the locus coeruleus and raphe nuclei regions of the brain stem, which are linked to arousal and the release of neurotransmitters — particularly serotonin, noradrenaline and dopamine. eTNS may lessen migraine occurrence, length and pain because it causes an enhanced release of noradrenaline and serotonin.
The benefits of eTNS for migraine patients
eTNS has several benefits that make it an effective treatment option for migraine. One, it’s a precision therapy that targets the specific pain pathways implicated in migraine transmission and dysfunction. As such, eTNS tends to cause fewer reactions and harmful effects elsewhere in the body, compared to medication therapies.
Secondly, neuromodulation has been proven to be a safe treatment option for migraine. Most migraine neuromodulation therapies are non-invasive and have no serious adverse effects. Any minor adverse effects associated with neuromodulation are fully reversible, typically with cessation of treatment.
A third major benefit is that eTNS can be used alongside other migraine therapies, including medication and lifestyle changes. That’s why neuromodulation is an appealing option for people who have found some success with other therapies and want to enhance their treatment routine. Many patients also express a preference for non-medication options to alleviate or control migraine attacks.
CEFALY and RelivionⓇ are two leading eTNS devices cleared by the FDA. CEFALY is available without a prescription, while Relivion requires a prescription. CEFALY targets the trigeminal nerve, while Relivion targets both the trigeminal and occipital nerves.
