Vestibular Paroxysmia

Definition and epidemiology

Vestibular paroxysmia (VP) is defined by recurrent vertigo attacks that usually last seconds, feel the same each time for a given person, and start spontaneously or with particular head movements. Like trigeminal neuralgia and hemifacial spasm, it is thought to be a neurovascular compression syndrome, in this case affecting the eighth cranial (vestibulocochlear) nerve (Brandt et al., 2016). In 2016 the Bárány Society published criteria that define two levels of diagnosis, ‘definite’ and ‘probable’ vestibular paroxysmia (Strupp et al., 2016).

Its frequency in the population is unknown. Because published case series are small, VP is considered rare, affecting fewer than 1 in 2000 people; yet at one tertiary centre that assessed more than 17,000 dizzy patients, about 4% received this diagnosis. Mean age in case series is 48-51 years, and men and women are affected about equally. The condition has also been described in children, in whom spontaneous remission with age is often reported (Strupp et al., 2016). In a registry-based series of 146 patients, mean age was 49.8 years and about half were women (Steinmetz et al., 2022).

Symptoms and signs

Attacks may be spinning or non-spinning (rocking or swaying) vertigo. Most last between one second and one minute; in some people they last several minutes or lengthen as the disorder progresses. Frequency ranges from up to 30 attacks a day to a few a year, and the course is usually chronic (Strupp et al., 2016). In a large series patients reported 5-30 attacks a day; about two thirds of attacks started spontaneously and a quarter with head movement (Steinmetz et al., 2022). Attacks provoked by turning the head to one side while upright differ from those of benign paroxysmal positional vertigo (BPPV), which start on lying down, rolling over in bed or looking up (Strupp et al., 2016).

Around 70% of patients have no other symptoms during attacks. When there are accompanying symptoms, they are usually cochlear, such as mild tinnitus or sound sensitivity (hyperacusis) in one ear (Steinmetz et al., 2022). Vertigo and tinnitus together with hemifacial spasm suggest compression of the seventh and eighth nerves within the internal auditory canal. During an attack, horizontal-torsional nystagmus beating towards the affected ear may be seen. Between attacks the examination is usually normal, although about half of patients show mild to moderate unilateral vestibular hypofunction (Strupp et al., 2016).

Causes and risk factors

The accepted explanation is that attacks arise from abnormal discharges in the vestibulocochlear nerve caused by a vessel that touches or compresses it close to its entry into the brainstem. In a study of 20 patients, compression was shown in every case; the compressing vessel was the anterior inferior cerebellar artery (AICA) in 75%, and the contact lay 0-10.2 mm from the brainstem (Best et al., 2013). In another series of 32 patients, constructive interference in steady state (CISS) MRI showed at least one site of compression in all but one of the 23 patients scanned (Hüfner et al., 2008).

Contact between a vessel and the nerve does not on its own mean disease. A similar contact is seen on MRI in about 30% of people without symptoms (Strupp et al., 2016), and in 35% of a control group with trigeminal neuralgia (Best et al., 2013), so a causal link cannot be proven in every patient. Less often, a tumour or arachnoid cyst pressing on the nerve, or an enlarged, elongated basilar artery (vertebrobasilar dolichoectasia), can cause similar attacks, and multiple sclerosis plaques and brainstem infarcts must be excluded (Strupp et al., 2016). There is no epidemiological evidence for a genetic predisposition.

Audiological and clinical assessment

Diagnosis rests mainly on the history, and the Bárány Society criteria define two levels (Strupp et al., 2016):

• Definite vestibular paroxysmia: A) at least ten attacks of spontaneous spinning or non-spinning vertigo; B) duration less than 1 minute; C) stereotyped phenomenology in the individual patient; D) response to carbamazepine or oxcarbazepine; E) not better accounted for by another diagnosis.
• Probable vestibular paroxysmia: A) at least five attacks of spinning or non-spinning vertigo; B) duration less than 5 minutes; C) spontaneous or provoked by certain head movements; D) stereotyped phenomenology; E) not better accounted for by another diagnosis. Before treatment has been tried, only a probable diagnosis can be made.

Audiological and vestibular assessment aims to identify the affected side where possible and to exclude other causes of similar attacks:

• Pure-tone and speech audiometry: usually normal; any hearing loss is generally mild and unilateral, and less marked than in Ménière’s disease (Strupp et al., 2016).
• Auditory evoked potentials and vestibular tests: in a series of 20 patients assessed with auditory evoked potentials, cervical vestibular evoked myogenic potentials (cVEMP), caloric testing and video-oculography, findings were normal in 25%, showed clear unilateral loss of function in 45%, and in 30% showed a mixture suggesting both reduced and increased function in the same nerve (Best et al., 2013).
• Hyperventilation test: about a third of patients show non-specific hyperventilation-induced nystagmus, and the subjective visual vertical (SVV) may deviate by 3-6 degrees (Steinmetz et al., 2022).
• Positional tests: the Dix-Hallpike and supine roll tests are used to exclude BPPV.
• MRI: thin-slice CISS or FIESTA sequences of the internal auditory canal and cerebellopontine angle can show the compression. In one study, however, sensitivity was 100% and specificity only 65%; MRI alone does not make the diagnosis and must be interpreted with the clinical and neurophysiological findings (Best et al., 2013). MRI is also needed to exclude tumours, cysts, MS plaques and infarcts.

The differential diagnosis includes Ménière’s disease (attacks of 20 minutes to 12 hours) and Tumarkin’s otolithic crises, vestibular migraine, vertebrobasilar transient ischaemic attacks, paroxysmal brainstem attacks in multiple sclerosis or after stroke, episodic ataxia types 1 and 2, panic attacks, perilymph fistula and superior semicircular canal dehiscence (SSCD), BPPV and central positional nystagmus, orthostatic hypotension, and cerebellopontine angle masses such as vestibular schwannoma (Lopez-Escamez et al., 2015; Strupp et al., 2016).

Treatment and audiological rehabilitation

Treatment decisions and the choice of drug rest with the doctor. Because a response to carbamazepine or oxcarbazepine is one of the criteria for a definite diagnosis, these drugs are used both to reduce attacks and to support the diagnosis (Strupp et al., 2016). The diagnostic specificity of a response has not been established, however, as these drugs can help other paroxysmal disorders too. In a study following 32 patients for a mean of 31 months, treatment reduced attack frequency to 10% and attack intensity to 15% of baseline (Hüfner et al., 2008). In the randomised, double-blind, placebo-controlled crossover Vestparoxy trial, attacks roughly halved on oxcarbazepine compared with placebo (ratio 0.53), and adverse effects were the commonest reason for stopping (Bayer et al., 2018).

For people who cannot tolerate these drugs, other antiepileptic drugs are discussed as alternatives. In the small number of patients who do not respond to medication, the last resort is microvascular decompression surgery, which separates the vessel from the nerve; it is also used in rare cases where a non-vascular mass compresses the nerve (Brandt et al., 2016). The risks and expected benefit of surgery should be discussed in detail with the surgeon.

Before treatment the audiologist documents baseline findings with pure-tone and speech audiometry, acoustic reflexes, auditory evoked potentials and a vestibular test battery, teaches the patient to keep an attack diary, and helps to track changes in attack frequency during treatment. The long-term outlook is generally good: in a registry study of 146 patients, about three quarters of those with definite VP were attack-free after a mean follow-up of 4.8 years, and more than half of these remained attack-free without medication (Steinmetz et al., 2022).

Impact on quality of life and advice

Short attacks do not necessarily mean a small impact on daily life. Dizziness that strikes without warning dozens of times a day can be a safety problem on stairs, when driving or when working at height. Fear of attacks can lead people to avoid certain movements and social situations, and unexplained symptoms in the period before diagnosis can add to anxiety.

Practical advice: keep an attack diary, noting the date, time and length of each attack, what you were doing when it started, and whether tinnitus or a change in hearing came with it; this is very valuable both for diagnosis and for judging the response to treatment. When an attack starts, sit down or hold on to something stable. If you have started medication, tell your doctor about any other medicines you take and any side effects you notice, and do not stop it on your own. Ask your doctor when you can return to activities such as driving or working at height. Knowing that in most people the attacks lessen or stop over the years can ease anxiety.