Persistent geotropic direction-changing positional nystagmus: an independent disease entity? / 中华耳鼻咽喉头颈外科杂志

Persistent geotropic direction-changing positional nystagmus (DCPN) has been described in recent years as no latency or fatigability but a null plane when head is turned toward the affected side. Different from the canalolithiasis of horizontal semicircular canal, it is similar with cupulolithiasis, but the direction of nystagmus are opposite. Light cupula theory has been used to explain the characteristics of this unique nystagmus. In this paper, the characteristics, possible etiologies, pathogenesis, related diseases, diagnosis, treatment and prognosis of DCPN are reviewed.

The Light Cupula: An Emerging New Concept for Positional Vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common type of positional vertigo. A canalolithiasis-type of BPPV involving the lateral semicircular canal (LSCC) shows a characteristic direction-changing positional nystagmus (DCPN) which beats towards the lower ear (geotropic) on turning the head to either side in a supine position. Because geotropic DCPN in LSCC canalolithiasis is transient with a latency of a few seconds, the diagnosis can be challenging if geotropic DCPN is persistent without latency. The concept of “light cupula” has been introduced to explain persistent geotropic DCPN, although the mechanism behind it requires further elucidation. In this review, we describe the characteristics of the nystagmic pattern in light cupula and discuss the current evidence for possible mechanisms explaining the phenomenon.

The clinical features and efficacy of patients with geotropic direction-changing positional nystagmus / 中华耳鼻咽喉头颈外科杂志

Objective@#The purpose of this study was to observe the clinical characteristics of two types of geotropic direction-changing positional nystagmus, the transient(nystagmus time <1 min) and the persistent(nystagmus time > 1 min), and to evaluate the efficacy of the barbecue roll maneuver.@*Methods@#A total of 105 cases diagnosed by supine roll test were studied, which including 35 males and 70 females and the average age was (56.9±14.6)years. There were 70 transient geotropic DCPN and 35 persistent geotropic DCPN. The clinical characteristics and the immediate and one-week efficacy of the barbecue roll maneuver were discussed.@*Results@#The nystagmus disappeared at the null-point position and the nystagmus in supine position were opposite to the bowing (90° nose-down) position in persistent geotropic DCPN cases. While to the transient geotropic DCPN cases, there were no NP and no nystagmus in prone position. The ratio of the first onset of the two groups was 28.6% (persistent) and 72.9% (transient) respectively, and the difference was statistically significant (P<0.05). The immediate and one-week efficacy after barbecue roll maneuver were 91.4% and 80.0% in transient geotropic DCPN cases, and 0% and 42.9% in persistent geotropic DCPN cases, which were statistically significant different(P<0.05).@*Conclusions@#The light cupula hypothesis can mainly explain the clinical features of persistent geotropic DCPN cases; the barbecue roll maneuver is invalid to persistent geotropic DCPN cases which can be self-healing.

Persistent Positional Vertigo in a Patient with Sudden Sensorineural Hearing Loss: A Case Report

Because inner ear organs are interconnected through the endolymph and surrounding endolymphatic membrane, the patients with sudden sensorineural hearing loss (SSNHL) often complain of vertigo. In this study, we report a patient with SSNHL accompanied by persistent positional vertigo, and serial findings of head-roll tests are described. At acute stage, head-roll test showed persistent geotropic direction-changing positional nystagmus (DCPN), which led to a diagnosis of SSNHL and ipsilateral light cupula. Although vertigo symptom gradually improved, positional vertigo lasted for more than 3 weeks. At this chronic stage, persistent apogeotropic DCPN was observed in a head roll test, which led to a diagnosis of the heavy cupula. Although the mechanism for the conversion of nystagmus direction from geotropic to apogeotropic persistent DCPN is unclear, the change of specific gravity of the endolymph might be one of the plausible hypothetical explanations.