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.

Pseudo-spontaneous nystagmus in horizontal semicircular canal canalolithiasis.

Benign paroxysmal positional vertigo (BPPV) involving horizontal semicircular canal (HSCC) is characterized by direction-changing positional nystagmus (DCPN) in a supine roll test, and the occurrence of spontaneous nystagmus in HSCC BPPV has been reported recently. The aim of this study is to investigate the characteristics of pseudo-spontaneous nystagmus (PSN) in patients with HSCC canalolithiasis, and evaluate the effect of the presence of PSN on treatment outcome.Between April 2014 and January 2016, 75 and 59 patients with HSCC canalolithiasis and cupulolithiasis, respectively, were enrolled. Spontaneous and positional nystagmus were examined.PSN was observed in 31 of 75 patients (41%) with HSCC canalolithiasis, and 55 of 59 patients (93%) with HSCC cupulolithiasis. PSN persisted during the period of observation, which was at least 1 minute in all patients with PSN. In HSCC canalolithiasis, direction-reversing nystagmus was observed in 58 patients (25 bilateral and 33 unilateral). Nine of 25 patients with bilateral direction-reversing nystagmus, and 22 of 33 patients with unilateral direction-reversing nystagmus showed PSN. None of 17 patients without direction-reversing nystagmus showed PSN. The direction of PSN corresponded to that of direction-reversing nystagmus in all 22 patients with unilateral direction-reversing nystagmus. The proportion of patients who recovered after 1 session of repositioning maneuver was not significantly different between patients with and without PSN (P = .867).PSN was observed more commonly in HSCC cupulolithiasis than canalolithiasis. The pathophysiologic mechanism underlying PSN can be explained by natural inclination of HSCC and medial to lateral orientation of the HSCC cupular axis in cupulolithiasis, and by spontaneous reversal of initial positional nystagmus (direction-reversing nystagmus) generated by short-term adaptation of vestibulo-ocular reflex in canalolithiasis. The presence of PSN in HSCC canalolithiasis may not affect the treatment outcome.

Characteristics of hearing loss in patients with herpes zoster oticus.

Patients with herpes zoster oticus (HZO) may commonly show symptoms associated with 7th and 8th cranial nerve (CN VII and CN VIII) dysfunction. The aim of this study is to investigate the characteristics of hearing loss in patients with HZO and discuss possible mechanisms.Ninety-five HZO patients who showed at least one of the symptoms of CN VII and CN VIII dysfunction between January 2007 and October 2014 were included in this study. Hearing loss was defined when the mean thresholds of pure tone audiometry (PTA) in speech frequency (0.5 kHz + 1 kHz + 2 kHz/3) or isolated high frequency (4 kHz + 8 kHz/2) were greater than 10 dB in the affected ear compared with the healthy ear, and a total of 72 patients were classified as the hearing loss group.The difference of mean PTA thresholds between affected and healthy ears was significantly greater in the high frequency range than in low range (20.0 ±â€Š11.5 dB vs. 12.9 ±â€Š15.7 dB, P = 0.0026) in patients with hearing loss (n = 72). The difference between affected and healthy ear was significantly greater in patients with vertigo (n = 34) than those without vertigo (n = 38) in both the high (P = 0.033) and low (P = 0.024) frequency ranges. In contrast, the differences between affected and healthy ears were not significantly different between patients with facial palsy (n = 50) and those without facial palsy (n = 22) in both the high (P = 0.921) and low (P = 0.382) frequency ranges.In patients with HZO, hearing loss is more severe in the high frequency range than in the low frequency range. Hearing impairment is more severe in patients with vertigo than in those without vertigo in both the high and low frequency ranges, even though the degree of hearing impairment is not significantly different between patients with and without facial palsy. These findings indicate that the mechanisms of viral spread from CN VII to CN VIII may differ between vestibular and audiologic deficits.