By: Fiza Nadeem
The Role of the Vagus Nerve in Epilepsy
What is vagus nerve?
According to the Cleveland Clinic (2022), the vagus nerves are part of the parasympathetic system and carry signals between the body, heart, and digestive system. These nerves play a vital role in sensory and motor functions such as heart rate, immune system responses, digestion, mood, skin sensations, muscle sensations, mucus, saliva production, taste, speech, and urine. (Cleveland Clinic, 2022)
Location of vagus nerve
The vagus nerve runs from the brain to large intestines, making them the longest cranial nerve. The left vagus nerve goes down the left side of the body while the right vagus nerve goes down the right side of the body. These nerves go through our body and exit from the medulla oblongata in the lower brainstem. Once they have excited from the medulla oblongata, the nerves connect with the neck, chest, lungs, heart, digestive tract, and abdomen. (Cleveland Clinic, 2022)
Vagal nerve branches
The right and left vagal nerves form a vagal trunk by joining together, connecting at the esophageal hiatus and opening where the esophagus passes into the abdominal cavity. The vagal trunk itself includes the anterior (which is the front) and posterior (which is the back) gastric nerve that goes into the abdomen. The vagal nerve branches include inferior ganglion branches that send nerves to the throat and voice box. The superior ganglion branch sends nerves to the spine and ear. On the other hand, the vagus nerve branch connects the nerves to the lungs, heart, and esophagus (Cleveland Clinic, 2022)
Signs of vagus nerve issues
Depending on the cause and the part of the nerve that is damaged, it can cause different symptoms. One may experience symptoms such as acid reflux, changes to heart rate, changes in blood sugar, changes in blood pressure, fizziness, fainting, loss of appetite, weight loss that cannot be explainable, nausea, vomiting, difficulty swallowing, loss of gag reflex, and bloating. (Cleveland Clinic, 2022)
The vagus nerve stimulation (VNS)
The stimulation uses electrical impulses to simulate a person’s left vagus nerve by implanting a small device in the chest. There is a wire that is running under the skin and it connects the device and the nerve. Through the device, electrical signals are sent through the left vagus nerve to the brain. These electrical signals are painless and mild. The impulses sent by the electrical signals play a role in calming down the irregular electrical activity in the brain. (Cleveland Clinic, 2022)
What is the Vagus nerve stimulation used to treat (VNS)?
According to the United States Food and Drug Administration (FDA), vagus nerve stimulation can be used in the treatment of epilepsy and depression. At the moment, it is under investigation for being considered as a treatment for other issues such as pain, rheumatoid arthritis, post traumatic stress disorder (PTSD), inflammatory bowel disease (IBD), and cluster headaches. (Cleveland Clinic, 2022).
Vagus nerve stimulation for Epilepsy
Vagus nerve stimulation (VNS) is a nonexperimental surgical option for patients with epilepsy, especially the patients who are hesitant to undergo a neurosurgical procedure (Milby et al., 2009) ). The procedure for the vagus nerve stimulation consists of (1) helical electrode placed on the left cervical vagus nerve, and (2) stimulation is provided by neurocybernetic prosthesis that is implanted in the upper chest (Krahl, 2012).
Various studies give the suggestion that the maximum protection from seizures can occur when the stimuli is administered at 20-30 hertz although patients (Krahl, 2012). There are trials which have indicated that the device reduces the degree of occurrence of a partial seizure (Krahl, 2012). Additionally, patients have achieved a greater than 50% reduction when it comes to the seizure frequency (Krahl, 2012).
Overall, as we can see, the vagus nerve is a significantly important nerve in the body due to the role it plays in the parasympathetic nervous system, sensory functions, and motor functions. Due to the vital role it plays in the human body, the damage caused to the vagus nerve is detrimental. It causes issues such as changes in heart rate, blood pressure, blood sugar, loss of one’s appetite, weight loss, nausea, amongst other issues. However, treatment options such as vagus nerve stimulation (VNS) exist for patients with epilepsy since it is considered a nonexperimental surgical option. It can be considered an effective option since empirical evidence has demonstrated reduced frequency to seizures. It is important to note that the treatment of vagus nerve stimulation (VNS) is being considered for other conditions in ongoing studies. Thus, it allows researchers to expand knowledge in regard to the topic of the vagus nerve and decide if it benefits society for the greater good.
References
Cleveland Clinic. (2022). Vagus nerve: Gastroparesis, vagus nerve stimulation & syncope. Cleveland Clinic. https://my.clevelandclinic.org/health/body/22279-vagus-nerve
Krahl, S. (2012). Vagus nerve stimulation for epilepsy: A review of the peripheral mechanisms. Surgical Neurology International, 3(2), 47. https://doi.org/10.4103/2152-7806.91610
Milby, A. H., Halpern, C. H., & Baltuch, G. H. (2009). Vagus nerve stimulation in the treatment of refractory epilepsy. Neurotherapeutics, 6(2), 228–237. ISSN 1878-7479, https://doi.org/10.1016/j.nurt.2009.01.010.
