Vestibular Paroxysmia

Vestibular paroxysmia is a vestibular syndrome of brief, recurrent attacks of vertigo or dizziness lasting seconds to a few minutes. It was formerly called disabling positional vertigo. Prevalence is about 3 to 4 percent of patients in a dizziness clinic, and it is more common in middle aged adults.

The attacks are thought to result from neurovascular compression of the eighth cranial nerve at the root entry zone, by an artery (usually the anterior inferior cerebellar artery) or vein. This produces ephaptic discharges, a nerve irritation analogous to trigeminal neuralgia.

Other causes: arachnoid cysts, vestibular schwannoma or other cerebellopontine angle lesions, and vascular loops with vertebrobasilar dolichoectasia.

Diagnostic criteria require:

• At least ten attacks of spontaneous spinning or non-spinning vertigo
• Duration less than 1 minute
• Stereotyped phenomenology in a particular patient
• Response to carbamazepine or oxcarbazepine
• Exclusion of other diagnoses

The disorder runs a chronic course with remissions.

• Brief (seconds to 1 minute, rarely longer) recurrent attacks of vertigo or dizziness occurring spontaneously or provoked by head turning, hyperventilation or particular head positions, many times per day (even up to 30 to 100 per day).
• Attacks are stereotyped and can be accompanied by unilateral tinnitus, hearing fluctuation or hypoacusis, aural fullness, and occasional nystagmus during the attack.
• Between attacks, the patient is normal, though a minority have mild chronic vestibular deficits (about 30 percent with a mild vestibular loss on caloric testing).
• Nausea is uncommon, and symptoms may be reproduced by hyperventilation for 1 to 2 minutes.
• No associated neurological deficit or hearing loss between attacks (progressive hearing loss indicates other causes).
• Unlike benign paroxysmal positional vertigo, the attacks are not consistently positional and are not triggered by the Dix-Hallpike manoeuvre; unlike Ménière disease, the attacks are very short and frequent.

• Diagnosis is based on clinical criteria. The response to carbamazepine confirms the diagnosis (a therapeutic trial).
• Neuro otological examination is usually normal. Hyperventilation for up to 2 minutes can provoke nystagmus (inhibitory or excitatory, typically towards the affected side). Video oculography during attack, if captured.
• MRI of the brain with high resolution 3D constructive interference in steady state (CISS) or fast imaging employing steady state acquisition (FIESTA) T2-weighted sequences of the cerebellopontine angle and internal auditory canal. It shows neurovascular contact between the eighth nerve and a vessel, which is found in many people without symptoms and so is not diagnostic. It also excludes tumour, cysts and demyelination.
• Audiometry is usually normal or shows mild asymmetrical hearing loss.
• Caloric testing and video head impulse testing show mild unilateral vestibular hypofunction in some. Auditory brainstem response shows prolonged interpeak latency.
• Exclude benign paroxysmal positional vertigo, Ménière disease, vestibular migraine, transient ischaemic attack, epilepsy, cardiac arrhythmia, panic disorder, and perilymph fistula.

• First line pharmacological treatment is a sodium channel blocker. Carbamazepine 200 to 600 mg daily in two to three divided doses. Start 100 to 200 mg once or twice daily, and increase by 100 to 200 mg every few days to the lowest effective dose, usually 200 to 400 mg daily; maximum 1,200 mg daily. Response is in about 80 to 90 percent within days, usually with a dramatic reduction in attack frequency.
• Alternatively, oxcarbazepine 300 to 900 mg daily in two divided doses (start 150 to 300 mg twice daily). It is better tolerated, with less drug interaction and fewer side effects. Check sodium.
• Monitor for drowsiness, dizziness, ataxia, rash, hyponatraemia, leucopenia, and abnormal liver tests. Screen for HLA-B*1502 in patients of Asian ancestry before starting carbamazepine. Check the full blood count, sodium and liver function at baseline and periodically.
• Continue treatment for at least 6 months to 1 year, then taper gradually. Relapses occur in some, who need further treatment.
• Alternatives when carbamazepine or oxcarbazepine are not tolerated: phenytoin 200 to 300 mg daily, lamotrigine 25 to 200 mg daily (slow titration), gabapentin 300 to 1,800 mg daily, topiramate, valproate, or eslicarbazepine.
• Patient education and reassurance; avoiding triggers (rapid head movements and hyperventilation); stress reduction.
• Surgery (microvascular decompression of the vestibulocochlear nerve via a retrosigmoid craniotomy) is for refractory or medication intolerant cases with confirmed vessel compression on imaging. Success is about 70 to 80 percent.
• Surgical risks include hearing loss (up to 10 to 20 percent), facial nerve injury, cerebrospinal fluid leak and other complications. Consider surgery only after medical failure and careful selection.
• Vestibular rehabilitation is helpful in patients with residual deficits or persistent imbalance.
• Follow up: clinical review at 4 to 6 weeks to assess response and tolerability, and every 6 to 12 months afterward. Repeat MRI if new features appear.
• Prognosis: favourable with medication. The condition is chronic with remissions and relapses.