Differential Involvement during Latent Herpes Simplex Virus 1 Infection of the Superior and Inferior Divisions of the Vestibular Ganglia: Implications for Vestibular Neuritis

Abstract

Controversy still surrounds both the etiology and pathophysiology of vestibular neuritis (VN). Especially uncertain is why the superior vestibular nerve (SVN) is more frequently affected than the inferior vestibular nerve (IVN), which is partially or totally spared. To address this question, we developed an improved method for preparing human vestibular ganglia (VG) and nerve. Subsequently, macro-and microanatomical as well as PCR studies were performed on 38 human ganglia from 38 individuals. The SVN was 2.4 mm longer than the IVN, and in 65% of the cases, the IVN ran in two separate bony canals, which was not the case for the SVN. Anastomoses between the facial and cochlear nerves were more common for the SVN (14/38 and 9/38, respectively) than for the IVN (7/38 and 2/38, respectively). Using reverse transcription-quantitative PCR (RT-qPCR), we found only a few latently herpes simplex virus 1 (HSV-1)-infected VG (18.4%). In cases of two separate neuronal fields, infected neurons were located in the superior part only. In summary, these PCR and micro-and macroanatomical studies provide possible explanations for the high frequency of SVN infection in vestibular neuritis.IMPORTANCE Vestibular neuritis is known to affect the superior part of the vestibular nerve more frequently than the inferior part. The reason for this clinical phenomenon remains unclear. Anatomical differences may play a role, or if latent HSV-1 infection is assumed, the etiology may be due to the different distribution of the infection. To shed further light on this subject, we conducted different macro-and microanatomical studies. We also assessed the presence of HSV-1 in VG and in different sections of the VG. Our findings add new information on the macro-and microanatomy of the VG as well as the pathophysiology of vestibular neuritis. We also show that latent HSV-1 infection of VG neurons is less frequent than previously reported.KEYWORDS HSV-1 latency, human, vestibular ganglia, vestibular neuritis V estibular neuritis (VN) is a common cause of an "acute unilateral vestibulopathy." The main clinical symptoms of VN are acute onset of prolonged severe spinning vertigo with spontaneous horizontal torsional nystagmus toward the unaffected ear, postural imbalance, and nausea (1). Its annual incidence is reported to be 3.5 to 15.5 per population of 100,000 (2, 3). It is the third most common cause of peripheral vestibular

Are viral-infections associated with Ménière’s Disease? A systematic review and meta-analysis of molecular-markers of viral-infection in case-controlled observational studies of MD

“…Beyond the clinical setting, experimental investigations would be of chief importance for understanding how CMV and other viral pathogens might influence or else relate to the pathophysiology of MD. With regards to experimental investigations of viral-infection in MD-models, the beginnings of such investigations have been conducted, although such investigations are particularly difficult given the lack of understanding of MD in general [69–72]. In the last decade or so, models of particular components of MD pathophysiology have become more accessible due to increased efficiency and cost-effectiveness afforded by simple genetic models such as that of the Phex mouse for modelling EH [73].…”

Acute Bilateral Superior Branch Vestibular Neuropathy

“…Our case presents a clinical picture most compatible with acute BVH with preservation of hearing given the absence of a central nervous system lesion, hearing loss, or history of ototoxicity exposure. VN is typically unilateral and damages the superior vestibular nerve much more frequently than the inferior vestibular nerve ( 8 ). We propose our case is best explained as a bilateral VN, given that the pattern of damage has clearly damaged both superior vestibular nerves—as evidence from the reduction of VOR gain from each horizontal and superior semicircular canals and the utricle, with preservation of function in the posterior semicircular canal and saccule.…”

Decreased 25-Hydroxyvitamin D Levels in Patients With Vestibular Neuritis

“…Herpes simplex virus type 1 DNA has also been detected in human vestibular ganglia at the time of autopsy. These viruses (herpes simplex virus types 1 and 2 and herpes zoster virus) have a propensity for invading sensory neurons, establishing latency within the nucleus of ganglion cells and becoming reactivated under some condition (36, 39, 40). The local inflammatory reaction of the inner ear caused by prior or concurrent infection may hypothetically be regulated/inhibited by normal levels of vitamin D, similar to suppression of the production of pro-inflammatory cytokines in patients with congestive heart failure (41) and in experimental bowel disease (42).…”