September 30, 2019
In the wake of these promising early findings, study investigator Shin C. Beh, MD, assistant professor of neurology, University of Texas, Southwestern Medical Center, Dallas, encourages clinicians to try novel neuromodulatory approaches like vagus nerve stimulation for their VM patients.
"It's safe, with not much risk to the patient. I'd say go for it; try it out," he told Medscape Medical News.
The study was published online September 25 in Neurology.
Common Cause of Vertigo
VM is the most common neurologic cause of vertigo. All patients with VM have vertigo as a manifestation of migraine, but they may or may not have headache and, if they do, it is often less severe than pain associated with typical migraine.
The cause of VM, which affects 1% to 2.5% of the population, is primarily linked to genetics. Compared with other migraine types, it is much more common among women than men.
Analgesics may not be effective for acute VM. Antiemetics and medications that quiet down the entire vestibular system are sometimes used, said Beh, but these may cause sedation and impair engagement in daily activities. In addition, although triptans may be useful, the evidence for their use in VM is inconclusive.
VNS has been shown to be safe and effective for acute migraine. The US Food and Drug Administration has cleared the hand-held gammaCore (electroCore) for migraine, as well as cluster headache, in adults.
The retrospective study included 18 patients (16 women and two men), with a mean age of 45.7 years, diagnosed with VM. The diagnostic criteria include at least five episodes of moderate or severe vestibular symptoms. Some patients in the study described these episodes as a spinning or rocking sensation.
The criteria also require that 50% or more of these episodes be associated with at least one of three migrainous features. These include migraine headache, photophobia and phonophobia, and visual aura.
Study participants were all patients Beh was seeing in his clinic. Of the 18 participants, 14 were in the midst of an acute VM attack.
"They happened to show up to clinic with an attack and had no medication on hand. The best solution I could come up with was to offer the stimulation," he said.
Quick, Safe, Noninvasive
Prior to VNS treatment, patients graded the severity of their vertigo/dizziness and headache, if present, using a visual analog scale (VAS) with 0 representing no symptoms and 10 the worst imaginable.
Although some participants were on pharmacologic migraine prevention, none had taken any migraine abortives, antiemetics, or vestibular suppressants within 24 hours of the intervention.
Under supervision, patients used the device to deliver bilateral 120-second electrical stimulations to the right front and then to the left front of the neck.
"It's quick — 2 minutes on each side," said Beh. "It doesn't cause any sedation."
Patients graded their vertigo/dizziness/headache using the same VAS 15 minutes after VNS treatment.
"The most significant finding was that the vertigo got better," said Beh.
In the 14 participants who were having a VM attack, 13 reported the vertigo improved and one reported no benefit. Of those who experienced improvement, two had complete resolution and several described at least a 50% improvement in vertigo severity.
The mean vertigo intensity was 5.2 before VNS and 3.1 after treatment. The mean reduction in vertigo intensity was 46.9%.
Only five patients experienced a headache with their VM attack. One experienced complete resolution after stimulation and four reported at least a 50% improvement in headache intensity.
Mean headache severity was 6 prior to VNS and 2.4 after treatment. Mean reduction in headache intensity was 63.3%.
Four of the 18 participants who just had interictal dizziness reported no benefit from the treatment.
Beh believes that the stimulation may work through nuclei located in the brain stem.
"One of the nuclei, the nucleus tractus solitarius, is of particular interest because the trigeminal system, vestibular system, and vagal system all connect through that nucleus," he said.
But there's evidence that the effect may not be limited to the brain stem. Beh cited research suggesting that VNS causes changes in multiple areas of the brain, including the thalamus, parietal lobes, and temporal lobes, which are areas involved in the processing of vestibular information.
"I think what's happening is that by stimulating the vagus nerve, you're altering the activity within the vestibular system. By doing that, you shut down the spreading processes of a migraine, so whatever electrical dysfunction was causing the migraine, stimulating the vagus nerve somehow manages to shut that down," he said.
Aside from patients reporting slight discomfort on the neck during the stimulation, there were no side effects of the intervention, said Beh.
"This is very safe and very well tolerated. None of my patients complained about anything negative. The muscles of the face might pull a little bit, but that's about it."
Beh hopes to carry out larger studies to test VNS for rescue treatment of vestibular migraine, and possibly for prevention. Such studies would need to have a sham-control design, he said.
Commenting on the findings for Medscape Medical News, Ji-Soo Kim, MD, PhD, professor, department of neurology, Seoul National University College of Medicine, who, along with colleagues, recently identified a new and possibly treatable type of vertigo known as recurrent spontaneous vertigo. This disorder is not accompanied by neurologic symptoms and does not meet diagnostic criteria for vestibular migraine, Ménière disease, or vestibular neuritis.
"Even though I don't have any experience with VNS, this study may provide a promising opportunity to develop a noninvasive therapy for vestibular migraine," said Kim.
"This advantage seems to balance the limitation of a retrospective design on a small number of patients," he added.
Beh and Kim have reported no relevant financial disclosures.