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Vagus nerve stimulation (VNS) is a surgical treatment of epilepsy. The cervical course of left vagus nerve originates from jugular foramen and descends at deep lateral side along with left common carotid artery (CCA), then changes to superficial anterior side, and this location varies by individual. Ultrasound could preoperatively identify the anatomical assessment of vagus nerve, which could be helpful for surgeons. In this study, we tried to evaluate preoperative vagus nerve location with ultrasound. From January 2012 to October 2022, every patient who underwent VNS in our institution was enrolled. With ultrasound, vagus nerve crossing point from deep lateral to superficial anterior was classified into 3 types according to location based on sternocleidomastoid (SCM), when crossing point was in upper half of SCM: high type, when within bottom third quarter of SCM: middle type, and when lower than bottom fourth quarter of SCM: low type. We enrolled 23 patients who underwent VNS. Mean age (±SD) was 28.4±12.9, and 13 patients (57%) were male. Two patients (8.7%) were high type, 5 patients (21.7%) were middle type, and 16 patients (69.6%) were low type. Of all patients, intraoperative vagus nerve locations corresponded with preoperative ultrasonography findings. The crossing point of left vagus nerve from deep lateral to superficial anterior side varied by individual and ultrasound could preoperatively identify the location. Preoperative anatomical knowledge of vagus nerve with ultrasound is essential for VNS surgeons. [ABSTRACT FROM AUTHOR]

Neuromodulation therapy for epilepsy is the third treatment option after medical treatment with antiepileptic drugs and surgical treatment, such as epileptic focal resection. In addition to vagus nerve stimulation(VNS), deep brain stimulation(DBS)and responsive neurostimulation(RNS)have been approved in several countries. These therapies consist of an implantable device and stimulating electrodes. These therapies have great potential to reduce seizure frequency and severity, improve patients' quality of life, and maintain therapeutic efficacy. When VNS was first introduced, electrical stimulation was set at regular intervals. However, current devices have introduced closed-loop therapy, in which stimulation is performed by detecting seizures. Multi-mode stimulation settings have also been introduced in VNS to adjust patient's seizure characteristics based on the time of the day when seizures are most likely to occur. This review describes the third therapeutic approach for the treatment of epilepsy based on recent research reports.

Vagus nerve stimulation (VNS) is used for treatment of refractory epilepsy and depression, particularly in western countries. In our country, VNS is covered by insurance for treatment of refractory epilepsy. In this study, we discuss the findings of previous studies that have reported VNS for depression, based on a history of VNS. Additionally, we have briefly described the mechanisms underlying the effects of treatment options used for depression.

Migraine and cluster headache are common headache disorders that impact patients' quality of life. The pharmacotherapy for acute headache attacks is sometimes ineffective, and the adherence to preventive medications is low due to their side effects and/or lack of efficacy. Recently, several non-invasive neuromodulation devices for primary headache disorders have been launched and attracted the attention of patients and physicians because of their practicality, safety, and the possibility of becoming new treatment options. In this review, we describe external trigeminal nerve stimulation (eTNS), non-invasive vagal nerve stimulation (nVNS), and single-pulse transcranial magnetic stimulation (sTMS) which have been well studied in recent randomized sham-controlled trials and open-label studies. We also describe their mechanisms of action and adverse events.

Previously, we reported a case of brainstem cavernous hemangioma showing false positive responses to electromyographic tracheal tube (EMG tube). We concluded that the cause was spontaneous respiration accompanied by vocal cord movement. We report a case of left vertebral artery aneurysm showing evoked potentials on bilateral electrodes by the left vagus nerve stimulation to EMG tube. An 82-year-old woman underwent clipping of a left unruptured vertebral artery-posterior inferior cerebellar artery aneurysm. General anesthesia was induced with remifentanil, propofol and suxamethonium, and was maintained with oxygen, air, remifentanil and propofol. We monitored somatosensory evoked potentials, motor evoked potentials, and electromyogram of the vocal cord. When the manipulation reached brainstem and the instrument touched the left vagus nerve, evoked potentials appeared on bilateral electrodes. EMG tube is equipped with two electrodes on both sides. We concluded that the left vagus nerve stimulation generated evoked potentials of the left laryngeal muscles, and they were simultaneously detected as potential difference between two electrodes on both sides. EMG tube is used to identify the vagus nerve. However, it is necessary to bear in mind that each vagus nerve stimulation inevitably generates evoked potentials on bilateral electrodes.

For treatment of epilepsy in patients of adolescence and adulthood, we always take into account all the 3 aspects of 1) diagnosis of seizure type and epilepsy syndrome, 2) existence of comorbidity and 3) interaction between concomitant drugs, and thus an appropriate treatment approach is individualized. The first line antiepileptic drug (AED) used for focal seizure or epilepsy is carbamazepine, and the first line AED for generalized seizure or epilepsy is valproic acid. If monotherapy with these drugs is insufficient, it is recommended to change to another drug or to add other drugs. For add-on therapy, the interaction between drugs should be considered. If polytherapy with these drugs is insufficient, diagnosis are again carefully checked, and further examination for resective epilepsy surgery or vagus nerve stimulation is considered.

Subcutaneous injection and nasal spray of sumatriptan are known to be useful for the treatment of acute phase of cluster headache. Although nasal spry of zolmitriptan is not available in Japan, it is also reported to be effective for the acute phase of cluster headache. In addition, high flow oxygen is also reported to abort the attack of cluster headache. For preventive treatment of cluster headache, calcium channel blocker (verapamil) and steroids are recommended. In addition to these medications, some of refractory chronic cluster headache patients are reported to be respond to the occipital nerve block, deep brain stimulation, vagus nerve stimulation and occipital nerve stimulation. Furthermore, recent report revealed that stimulation of the sphenopalatine ganglion is effective for acute pain relief and attack prevention. This review will introduce the recent treatment for cluster headache including these nerve stimulations.

Vagus nerve stimulation is the first electrical stimulation therapy for epilepsy. While its clinical use was approved by the European Union in 1994 and by the United States in 1997, it was approved last year and coverage by public insurance started last July in Japan. Owing to less invasiveness and broad indication, it is expected that vagus nerve stimulation will be increasingly used in Japan as well. Its efficacy for refractory partial seizures in patients older than 13 years was validated by two randomized control trials. Although it has been used for children and generalized seizures broadly, the efficacy for these subpopulations of patients has not been validated by randomized control trials, necessitating those studies in the near future. Afferent neural impulses generated by vagus nerve stimulation transmit to the solitary tract nucleus, then via multiple pathways including the monoamine system, vagus nerve stimulation affects the excitability of the cortical neurons. It likely exerts the anti-epileptic and anti-seizure effects using these pathways, but the detailed mechanisms underlying the effect remains to be elucidated further in future.