Trigeminal nerve stimulation (TNS) is a non-invasive form of neuromodulation that uses mild electrical pulses to influence brain activity. This therapeutic approach delivers targeted electrical signals to specific branches of the trigeminal nerve, located on the face. TNS employs a small, external device placed on the forehead, aiming to modify neural activity in various brain regions without surgical implantation.
How Trigeminal Nerve Stimulation Works
The trigeminal nerve is the largest cranial nerve, responsible for sensation in the face, scalp, teeth, and oral and nasal cavities, and controls chewing muscles. External trigeminal nerve stimulation (eTNS) typically targets its supraorbital branches, located just above the eyebrows on the forehead.
When these superficial branches are stimulated, they send electrical signals along the nerve pathways. These signals then travel to deeper brain structures, including the brainstem nuclei like the locus coeruleus and the nucleus solitarius, as well as the thalamus. The locus coeruleus, in particular, is a major source of norepinephrine, a neurotransmitter that plays a role in regulating arousal, attention, and mood.
The modulated signals from the trigeminal nerve can influence activity in various interconnected brain regions, such as the anterior cingulate cortex, which is involved in mood, attention, and decision-making. This “bottom-up” mechanism suggests that TNS can help regulate or “calm” brain activity in areas implicated in certain neurological and psychiatric conditions. Changes in brain blood flow have been observed within minutes of therapy, indicating a direct effect on these regions.
Conditions Treated With TNS
TNS has been investigated for several neurological and psychiatric conditions. One notable application is in treating Attention-Deficit/Hyperactivity Disorder (ADHD) in children. The external TNS system received U.S. Food and Drug Administration (FDA) marketing authorization in 2019 for pediatric patients aged 7 to 12 years. This device offers a non-drug alternative by sending therapeutic signals to brain areas involved in ADHD, helping to regulate attention, emotion, and behavior.
TNS also shows promise for individuals with drug-resistant epilepsy (DRE), where seizures are not adequately controlled by medication. Studies suggest TNS may reduce seizure frequency and can be delivered non-invasively. This approach offers a potential adjunctive therapy for patients who have not responded to traditional antiepileptic drugs.
TNS is also being explored as an adjunctive treatment for major depressive disorder (MDD), especially for cases resistant to standard medication. The trigeminal nerve projects to brain structures implicated in depression, like the nucleus tractus solitarius and locus coeruleus. Studies indicate that nightly TNS can lead to significant symptomatic improvement in mood and quality of life for adults with MDD. These findings suggest TNS could be a beneficial addition to existing treatment strategies.
The Stimulation Procedure
External trigeminal nerve stimulation (eTNS) is designed for at-home use. The device connects to a small, disposable patch that adheres to the patient’s forehead, typically placed just above the eyebrows to target the trigeminal nerve branches.
Treatment usually occurs during sleep, delivering low-level electrical pulses for about eight hours nightly. Users may feel a gentle tingling or pulsing sensation at the application site. A caregiver often manages the system, especially for pediatric patients. Initial effects may become noticeable after about four weeks of consistent use.
Associated Risks and Side Effects
Trigeminal nerve stimulation is well-tolerated, with most reported side effects being mild and temporary. Common side effects include skin irritation or redness at the electrode site, headaches, fatigue, drowsiness, increased appetite, trouble sleeping, or teeth clenching.
While TNS is non-invasive, it is not suitable for all individuals. Contraindications include patients with active implantable medical devices like pacemakers, neurostimulators, or insulin pumps. TNS is also not recommended for children younger than 7 years. Patients should discuss their medical history with a healthcare provider to determine if TNS is appropriate.