MRI should be used with caution in diagnosing vestibular paroxysmia

Magnetic resonance imaging (MRI) demonstrates blood vessels clearly in the cerebellopontine angle and internal auditory meatus. There is even a classification system to describe the exact location and relation of the blood vessel and the nerve. Unfortunately, this is of doubtful clinical significance. Even higher Tesla MRI machines are not able to distinguish between ordinary persons and patients.

Vestibular paroxysmia
A vascular loop seen on MRI. May this be the cause of vestibular paroxysmia?

According to Dr Anne-Marie Du Plessis, neuro radiogist, unless requested in the background of a clinical setting, it may be confusing if reported. MRI should not be ordered to confirm vestibular paroxysmia. At most, it should be ordered to exclude other pathology.

What is vestibular paroxysmia

Vestibular paroxysmia is a chronic vestibular disorder. It is characterised by the occurrence of numerous spells or episodes of short-lasting vertigo lasting seconds to a few minutes at most. It can even occur daily. The episodes of vertigo have a spontaneous onset, but in some cases, head movements may trigger symptoms. Patients may also complain of motion intolerance. In some instances, auditory symptoms like hyperacusis, tinnitus, hearing loss and facial nerve hemifacial nerve spasm may be present.

Diagnosing vestibular paroxysmia

In the majority of cases, the diagnosis is suspected based on the clinical presentation. With examination, some hypofunction of the vestibular nerves may be seen with nystagmus beating away from the affected side. Nystagmus may be elicited with hyperventilation.  If lucky, and the patient is seen during an episode, a nystagmus beating to the affected side may be present.

It is essential to exclude other conditions that may share some of the symptomatology. In order to confirm a diagnose, it is important to note a positive response to a sodium canal blocker. MRI is not used to confirm this condition, and it is merely used to exclude other conditions such as vestibular schwannoma, arachnoid cysts and multiple sclerosis.

Vestibular paroxysmia
Vestibular paroxysmia. Permission from Prof Michael Strupp et al.

How common is it, and which patients become symptomatic?

Vestibular paroxysmia is a rare condition. There is not much published data on this condition, but it is estimated that it occurs in about 50 per 100 000 of the population. It occurs equally in male and female patients, and up to date, no genetic susceptibility has been recognised. In a tertiary centre in Munich, Germany, vestibular paroxysmia was seen in 4% of the 17 000 patients seen at the vertigo and dizziness clinic.

Although it typically occurs around 50 years of age, anyone from children to the elderly may be unfortunate to suffer from it. Luckily in children and many patients, it may spontaneously go into remission.

What causes vestibular paroxysmia?

Vestibular paroxysmia occurs when a blood vessel, usually the anterior inferior cerebellar artery (AICA), causes abnormal irritation of the underlying cochleovestibular nerve with which it is in direct contact. This microvascular compression syndrome only occurs in some patients. In elderly patients, blood vessels changes such as atherosclerosis and damage to the nerve, as in previous vestibular neuritis, are believed to act as a trigger for the development of vestibular paroxysmia.

MRI is not sensitive enough to distinguish between regular contact, as is seen in nearly every person and pathological irritation seen in symptomatic patients.

 What about surgery?

Some patients may, despite the fact that they respond to medication, consider surgery. If the side is known, surgery may be an option. The late American professor of neurosurgery, Peter Jannetta, first described the procedure. The offending blood vessel is carefully separated from the cochleovestibular nerve, and a piece of Teflon is inserted. This is a risky procedure and should be considered as a last resort.

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