Herpes zoster neuritis involving superior and inferior parts of the vestibular nerve causes ocular tilt reaction

Abstract

A 43-year-old woman presented with peripheral facial nerve palsy, rotational vertigo, and hearing loss due to herpes zoster neuritis of the right seventh and eighth cranial nerves. Neuro-ophthalmologic examination showed a horizontal rotatory spontaneous nystagmus (fast phase) to the left and an ocular tilt reaction (OTR) to the right, a pattern of head tilt, skew deviation, ocular torsion, and tilt of perceived vertical. Ocular torsion was binocular but asymmetric with a predominant intorsion of the contralateral hypertropic eye (17° vs 7°). Since a complete OTR is rare in peripheral, but common in central vestibular disorders, involvement of the vestibular nucleus (due to a zoster meningoencephalitis) was first assumed. However, MRI scan (T1-weighted 2D-FLASH sequence) revealed contrast enhancement in both parts (pars superior and inferior) of the right vestibular nerve due to viral inflammation. The following conclusions can be drawn from the correlation of the neuro-ophthalmologic syndrome and MRI findings: (1) the horizontal component of spontaneous nystagmus is secondary to a horizontal semicircular canal paresis; (2) the rotatory component of the spontaneous nystagmus and the tonic OTR are secondary to a combined paresis of the anterior canal, the posterior canal, and the otoliths; and (3) the asymmetry of ocular torsion indicates incomplete loss of vestibular function with predominant involvement of the anterior semicircular canal.