New Type of Treatable Vertigo Identified

Pauline Anderson

May 23, 2018

Investigators have identified a new type of vertigo that may be treatable.

This recurrent spontaneous vertigo (RSV) is not accompanied by neurologic symptoms and doesn't satisfy the diagnosis of Ménière disease (MD), vestibular migraine (VM), vestibular neuritis (VN), or other related conditions. But it stands out in that it's characterized by prolonged headshaking nystagmus (HSN) and a marked susceptibility to motion sickness.

In their new paper, researchers describe the first study documenting HSN in a subgroup of patients with RSV of unknown cause.

"We proved that a group of patients with benign recurrent vertigo have a distinct disease entity other than vestibular migraine or Meniere's disease," senior author Ji-Soo Kim, MD, PhD, professor of neurology, Seoul National University College of Medicine, and chief at the Dizziness Center at the Seoul National University Bundang Hospital, Korea, told Medscape Medical News.

To identify this new entity, clinicians can administer a simple headshaking maneuver, said Kim. He called the maneuver "a valuable tool" in patients experiencing unexplained recurrent spontaneous vertigo and motion sickness.

The study was published online May 23 in Neurology.

Two Phases of HSN

Vertigo can be caused by serious conditions, such as tumors, or fairly benign conditions, such as MD. However, in some patients, physicians are unable to find any cause of the vertigo. 

 

Headshaking may hold some clues. According to Kim, repetitive headshaking for 15 to 20 seconds may induce nystagmus, or rapid and uncontrollable eye movements. 

"In normal circumstances, there would be no headshaking nystagmus, since the vestibular input from both sides of the labyrinth would be symmetric," explained Kim.

"However, if a vestibular loss occurs in one ear, the input from the damaged ear would attenuate, and the vestibular imbalance may be greater as the gap between the damaged and normal ear would accumulate through headshaking," he added.

There are two phases of HSN. After headshaking, the nystagmus peaks quickly and then slowly subsides. This is referred to as the primary phase. A weaker nystagmus may then develop, slowly building before slowly decreasing.

Of 338 patients presenting at the Dizziness Center with RSV and no identifiable cause, about 10% (n = 35) had HSN. These patients were compared with 35 others at the clinic who did not have HSN.

Motion Sickness

All patients underwent a comprehensive evaluation of audio-vestibular function in addition to routine neurologic examinations and were asked about family history of dizziness and vertigo.

Investigators also used the Motion Sickness Susceptibility Questionnaire (MSSQ), which is a sum of total sickness score during childhood (MSSQ-A) and during adulthood over the last 10 years (MMSQ-B).

When considered necessary, patients also had brain MRIs with or without magnetic resonance (MR) angiography. None of the participants had a history of migrainous headaches, tinnitus, ear fullness, asymmetric hearing loss, or cerebellar diseases.

The characteristics of dizziness did not differ between those with and without HSN. Although the MSSQ-A score was similar between the groups, patients with HSN showed higher MSSQ-B scores than those without (median, 19 vs 0; P = .015).

In each patient with HSN, researchers determined the time constant (TC) — a parameter widely used in physics and engineering. In this case, the TC was calculated as an indication of the duration of the HSN; the longer the TC, the longer the HSN persists.

For comparison, the investigators measured the TC of HSN in 30 patients with VN, 30 patients with VM, and another 30 patients with unilateral MD, all of whom were randomly selected from a dizziness registry.

All patients underwent three-dimensional video-oculography. In some patients, researchers also carried out other tests, including the rotary chair test.

During this chair test, patients sit in a computerized chair wearing infrared video goggles that record eye movements. While the chair rotates at variable velocities, eye movements are recorded, and researchers can evaluate the vestibulo-ocular reflex (VOR).

New Version of Spontaneous Vertigo

The analysis showed that the estimated TC of the primary phase of HSN in the HSN group  at 12 seconds (95% confidence interval [CI], 12 - 13 seconds) was much longer than that of patients with VN (5 seconds; 95% CI, 4 - 5 seconds), VM (5 seconds; 95% CI, 5 - 6 seconds), and MD (6 seconds; 95% CI, 5 - 6 seconds).

TCs of the VOR were longer during the rotary chair test in patients with HSN.

Among the 35 patients with HSN, 7 showed vigorous long-lasting HSN. In 5 patients, HSN could be induced even with headshaking of only 2 to 5 seconds.

Researchers call the new condition recurrent spontaneous vertigo with head-shaking nystagmus (or RSV-HSN). 

While benign recurrent vertigo has in the past been regarded as just a variant of VM or MD, these new findings suggest that a faulty "velocity-storage mechanism" may play a role, write the investigators, adding that this mechanism stores activity related to slow-phase eye velocity.

This characteristic HSN may be from a hyperactive and asymmetric velocity-storage mechanism, the authors note, and they assume that this may be responsible for intermittent attacks of vertigo in these patients.

Kim said this may help explain the severe motion sickness in some of these patients.

"As the nystagmus was generated even with a brief duration of headshaking, we believe the hyperactive and biased velocity storage mechanism may play a role in some patients suffering from debilitating motion sickness," he said.

Preventive medication was prescribed in the 57% of patients who had frequent and severe vertigo symptoms and included nimodipine, betahistine, propranolol, flunarizine, baclofen, nortriptyline, and acetazolamide in various combinations.

While taking the prophylactic medication, about 30% of the patients reported partial, and 5% reported complete, recovery from symptoms.

During a median follow-up of 12 years from symptom onset (range, 2 - 58 years), symptoms resolved or improved in more than half the patients. No patients developed VM, MD, or cerebellar dysfunction during that time.

Identification Test?

Although "rather neglected" as a test in patients with dizziness, a headshaking maneuver can help identify this new type of treatable dizziness, said Kim.

While the patient sits in a dark room, an examiner moves the patient's head forward and then shakes the head horizontally. The patient then opens his or her eyes and a video recording is taken of eye movements.

Kim stressed that the length of HSN is important in distinguishing this new entity from VN, VM, or MD — and offered some tips.

This new condition should be suspected if HSN:

  • Occurs quickly — within just 2 to 5 seconds of the headshaking;

  • Lasts longer than about 20 seconds; or

  • Is present even if results of other vestibular tests, including the rotatory chair test, are all normal.

If this condition is suspected, Kim recommends considering medications, such as baclofen, that suppress the velocity-storage mechanism.

The investigators aim to test the effect of such drugs to see whether this changes the clinical course in these patients.

Expands Testing Protocols

In an accompanying editorial, Alexandre Bisdorff, MD, PhD, Clinique du Vertige, Esch-sur-Alzette, Luxembourg, and Jorge Kattah, MD, Illinois Neurological Institute, Peoria, praise the authors' "astute clinical observation skills."

Such skills allowed the researchers "to identify this new diagnostic entity for which imaging is unhelpful, as is so often the case in vestibular medicine," write Bisdorff and Kattah.

Identifying this new entity "reduces the group of so-far undiagnosed patients," they add.

Those with this new type of vertigo "have a clear interictal marker of central vestibular dysfunction, which is easy to recognize in a standard clinical vestibular workup," write the editorialists.

Commenting on the study for Medscape Medical News, Anna DePold Hohler, MD, associate professor of neurology, Boston University School of Medicine, Massachusetts, said the findings are valuable and represent an important diagnostic step forward.

"It may help to improve diagnostic and treatment options, ultimately improving quality of life for our patients," she said.

The results also should spur healthcare providers to "expand their testing protocol to include head-shaking techniques," added Hohler.

The study was supported by the National Research Foundation of Korea. Kim serves as an associate editor of Frontiers in Neuro-Otology and is on the editorial boards of the Journal of Clinical Neurology, Frontiers in Neuro-Ophthalmology, Journal of Neuro-Ophthalmology, Journal of Vestibular Research, Journal of Neurology, and Medicine. Bisdorff and Hohler have disclosed no relevant financial relationships. Kattah has been a consultant for Questcor and in 2012 loaned research equipment from his unit to Otometrics Co, Tastrup, Denmark (equipment no longer in use).

Neurology. Published online May 23, 2018. Abstract, Editorial

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