Light Cupula:To Be Or Not to Be?

Benign paroxysmal positional vertigo(BPPV)represents the most common form of positional vertigo.It is caused by dislodged otoconia that freely float in the semicircular canals(canalolithiasis)or attach to the cupula(cupulolithiasis).A cupulolithiasis-type(or a heavy cupula-type)of BPPV implicating the lateral semicircular canal(LSCC)exhibits persistent ageotropic direction-changing positional nystagmus(DCPN)in a head-roll test.However,in some cases,unlike any type of BPPV,persistent geotropic DCPN cannot be explained by any mechanisms of BPPV,and don’t fit the current classifications.Recently,the notion of light cupula has been introduced to refer to the persistent geotropic DCPN.In this study,we looked at the clinical features of light cuplula and discussed the possible mechanisms and therapeutic strategies of the condition.The notion of light cupula is a helpful addition to the theory of peripheral positional vertigo and nystagmus.

Analysis of persistent geotropic and apogeotropic positional nystagmus of the lateral canal benign paroxysmal positional vertigo

Objective:This study aims to analyze the clinical characteristics of persistent geotropic and apogeotropic positional nystagmus of LC-BPPV in view of light and heavy cupula discussion.Material and method:The study group includes 184 patients with LC BPPV(98 apogeotropic,86 geotropic type)who have been examined between 2009 and 2020.Ninety-nine females and 85 males,aged between 16 and 92 years were included(Ageotropic 49.32±14.12,geotropic 44.49±13.90 years).Average slow phase velocity(SPV)of positional nystagmus was documented and those with persistent directionchanging positional nystagmus lasting more than a minute were grouped separately.Age,gender difference,side of involvement,and recurrence pattern were particularly reviewed.Chi-square and One way ANOVA tests were used to compare the difference between groups.Statistical significance was set at P<0.05.Results:Thirty-seven patients with apogeotropic nystagmus(30.7%;37/98)and 18 patients with geotropic nystagmus(20.9%;18/86)had persistent nystagmus(p?0.05).Comparison of slow phase velocity(SPV)of persistent and non-persistent geotropic and apogeotropic positional nystagmus of the affected side was significant(p?0.05).Comparison of average age,male to female ratio,side of involvement,and the recurrence rate in patients with persistent and non-persistent geotropic and apogeotropic type positional nystagmus groups were not significant(p=0.177,p=0.521,p=0.891,p=0.702).Conclusion:Persistent geotropic and apogeotropic positional nystagmus is mostly correlated with the size,amount,and position of otoconial debris.It is difficult to justify the light cupula as a new geotropic variant of cupular pathology.Patients with persistent positional nystagmus present similar therapeutic outcomes and recurrence rates.