Pseudovestibular neuritis associated with isolated insular stroke

Abstract

Dear Sirs,Damage to the cerebellum or brainstem can often cause vestibular dysfunction. Although rare, central rotational vertigo following cerebral cortical lesions has also been reported [1,4,5,7]. However, no report has documented objective nystagmus associated with central rotational vertigo in cortical stroke. We describe a patient with rotational vertigo who showed mixed horizontal and torsional spontaneous nystagmus mimicking peripheral vestibulopathy in isolated insular infarction.A 51-year-old woman presented with sudden onset of word finding difficulty. She had history of Hashimoto thyroiditis. On admission, neurological examinations were unremarkable. Brain magnetic resonance imaging (MRI) revealed an acute infarction in the left insula. Small parts of the frontal operculum were also involved ( Fig. 1a). One day after symptom onset, her word finding difficulty had completely resolved and the Korean version of the Western Aphasia Battery was administered on the same day showed her overall language skills were normal (Aphasia Quotient = 82.0). However, the patient started to complain of rotational vertigo on the same day. Her vertigo occurred regardless of position change, which was not accompanied by nausea or vomiting. Neurological examinations on that day showed spontaneous right beating horizontal nystagmus. The line bisection test conducted on the second day of her vertigo onset showed bisection markers shifting to the left. Video-oculography performed 7 days after onset of vertigo revealed a right beating horizontal nystagmus mixed with a clockwise torsional component, which was augmented by horizontal head-shaking test (Fig. 1b). Head impulse test was normal. Bithermal caloric tests performed 8 days after vertigo onset revealed 18% canal paresis in the left ear. After that, her vertigo gradually resolved and she intermittently experienced rotational vertigo without any other symptoms, lasting 1 or 2 min, five times a month on average. Her electroencephalogram (EEG) taken during the course of the disease was normal. Follow-up bithermal caloric tests 6 months post stroke showed 14% canal paresis in the left ear. Her vertigo completely disappeared after 9 months post stroke. Follow-up computed tomography (CT) scan performed 17 months post stroke confirmed the lesion to be restricted to the left insula (Fig. 1c).The patient was admitted to our hospital, presenting with word finding difficulty, and her brain MRI showed acute infarction in the left insula. While her word finding difficulty disappeared 1 day after onset of stroke, she developed rotational vertigo. Her spontaneous nystagmus, i.e., a right beating horizontal nystagmus with a clockwise torsional component, suggested left vestibular neuritis (VN). However, normal head impulse test and small degree of canal paresis on bithermal caloric tests were not compatible with left VN, since typical unilateral VN shows positive head impulse test, and 25% or more difference of vestibular function between the affected and nonaffected

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