Is the nystagmus pattern in hemi-labyrinthectomized subjects during positional alcohol nystagmus 2 similar to that found in patients with cupulolithiasis in the lateral semicircular canal?

Light cupula phenomenon: a systematic review

Geotropic direction-changing positional nystagmus (DCPN) is transient in lateral semicircular canal (LSSK) canalolithiasis; it usually cuts off within a minute and fatigues. However, a “light cupula” mechanism has been described for patients with positional vertigo who exhibit a persistent geotropic DCPN without delay or fatigue. When the cupula becomes lighter than the surrounding endolymph, deflection may occur in the cupula under the influence of gravity. The person experiences dizziness and persistent positional nystagmus can be observed while remaining in that position.

In this review, studies investigating the “light cupula phenomenon,” which is a newly defined phenomenon in the literature, were compiled. A systematic literature search was conducted on the light cupula phenomenon in PubMed and Google Scholar databases to illuminate the clinical side of this new phenomenon and reveal its distinctive features. Turkish and English articles published between 2010 and 2021 were scanned; the thesis, reviews, and books were excluded from the study. Forty-eight articles were included in the study.

Mechanisms underlying light cupula has been explained as the “heavier endolymph hypothesis” with increased endolymph specific gravity due to an acute attack such as labyrinth hemorrhage, insufficient inner ear perfusion, or inflammation in the inner ear; “lighter cupula hypothesis” based on alcohol acting on the cupula earlier and making it lighter than the endolymph; “light particle hypothesis” due to the buoyancy of light debris, which are degenerative, swollen, and inflammatory cells in the endolymph adhering to the cupula and the “altered endolymph/perilymph density ratio hypothesis” that the difference in density between perilymph and endolymph causes light cupula. The pathophysiology of the light cupula phenomenon is still unclear, but it can be thought that all the different hypotheses may be effective in this phenomenon. Therefore, nystagmus characteristics and clinical course should be considered in patients for a more effective diagnosis and treatment process. In addition, the results of the studies show that light cupula may not be an uncommon disease and that some patients with geotropic DCPN can often be misdiagnosed as canalolithiasis LSCC-BPPV.

Positional alcohol nystagmus and serum osmolality: New insights into dizziness associated with acute alcohol intoxication

Positional alcohol nystagmus (PAN) is characterized by positional direction-changing nystagmus. Although the buoyancy cupulopathy, which implies that the cupula becomes lighter or heavier than the endolymph due to different diffusion rates of alcohol, has been accepted as possible mechanism of PAN, the evidence supporting this hypothesis is weak. The aim of present study is to investigate the possibility of serum osmolality change following alcohol intake as a cause of PAN. Nine healthy adults were recruited voluntarily. Positional nystagmus was examined before and every 1 hr after alcohol intake until 7 hr. Serum osmolality was measured before and 1 and 7 hr after alcohol intake. Before ingesting alcohol, no subject showed positional nystagmus, and mean serum osmolality was 285.9 ± 4.4 mOsm/kg. At 1 hr after drinking, mean serum osmolality increased to 302.9 ± 8.9 mOsm/kg, and all subjects exhibited geotropic positional nystagmus. At 7 hr after drinking, mean serum osmolality decreased to 289.1 ± 9.4 mOsm/kg, and all subjects showed ageotropic positional nystagmus. Change in serum osmolality following alcohol ingestion and subsequent change in specific gravity in the perilymph and endolymph may be a cause of PAN.

Conversion between geotropic and apogeotropic persistent direction-changing positional nystagmus

CONCLUSION

Clinical features in the course of conversion differed between patients with SSNHL and cupulopathy, which indicates that the pathophysiology of persistent geotropic or apogeotropic DCPN and the mechanism of the change in nystagmus direction may differ between the two groups.

OBJECTIVE

The aim of this study is to investigate clinical characteristics of 10 patients with persistent DCPN who exhibited a conversion of nystagmus direction between geotropic and apogeotropic, and discuss possible mechanisms.

METHODS

Using video-oculography, serial examinations of nystagmus in a head-roll test were performed.

RESULTS

Of these 10 patients, five had sudden sensorineural hearing loss (SSNHL) and the remaining five had cupulopathy. In SSNHL, direction of nystagmus changed from geotropic to apogeotropic in three patients and from apogeotropic to geotropic in two patients. In cupulopathy, persistent apogeotropic DCPN always preceded persistent geotropic DCPN. The change in nystagmus direction occurred earlier in patients with cupulopathy (1 or 2 days after vertigo onset) than in patients with SSNHL (4-23 days after vertigo onset). While the null plane was consistently identified on one side, regardless of the nystagmus direction in cupulopathy, it was not always identified on the side of hearing loss in SSNHL.

Vestibular findings in patients with persistent geotropic positional nystagmus: the 'light cupula' phenomenon

CONCLUSIONS

Persistent geotropic nystagmus indicates a condition of a light cupula, which is accompanied by vestibular disability and a high incidence of pathological findings in the vestibular tests. The prevalence of migraine is high.

OBJECTIVES

To examine subjective symptoms and characteristics of nystagmus in patients with persistent geotropic nystagmus using vestibular tests, as well as possible correlations to migraine in this group.

METHODS

We enrolled 20 patients with a mean age of 53 years. The slow phase velocity (SPV) of the geotropic nystagmus and the nystagmus with the patient's head in the supine (S) and prone (P) positions was recorded. All patients completed caloric tests, subjective visual horizontal (SVH), and vestibular evoked myogenic potential (VEMP). All tests were repeated at follow-up (FU).

RESULTS

SPV of the geotropic nystagmus directed to the left was 5.5°/s and that to the right was 3.5°/s. In 72% of patients, nystagmus in the P position was opposite to that in the S position. The vestibular tests were pathologic in about 60% of patients. At FU geotropic nystagmus was found in 40% of patients, but was significantly less intense. The vestibular test results remained at the same level at FU. Recurrent vertigo was reported in 78% of the patients. In all, 40% of the patients suffered from migraine.