Direction-fixed positional nystagmus following head-roll testing:how is it related with a vestibular pathology?

Objective:The goal of this study is to analyze the clinical view of patients with direction-fixed positional nystagmus(DFPN)following head-roll maneuver.Methods:Sixty patients with DFPN were reviewed retrospectively.Patients were categorized into 3 groups according to the direction of nystagmus based on rotation side.Associated problems were documented,and cumulative data were compared between groups.One-way analysis of variance(ANOVA test)was used for statistical analysis(P<0.05).Results:Thirty-three patients(55%)had stronger nystagmus beating towards the direction of head-roll(Group-A).Three patients developed geotropic LC-BPPV.Fourteen patients had inner ear disease.Sixteen patients(27%)had stronger nystagmus beating against the direction of head roll(Group-B).Nine patients had inner ear disease.None of the patients tested with head-shaking had change of direction of nystagmus.Eleven patients(18%)had DFPN with equal velocity during right or left head-roll maneuver(Group-C).Of those,nine patients had inner ear disease.None of the patients had change of direction of nystagmus.Comparison of the incidence of associated problems(migraine,vestibular neuronitis,Meniere’s disease etc.)in each group was not statistically significant(P˃0.05).Conclusion:Patients with DFPN should be followed for a possibility of vestibular pathology since vestibular problem was documented for more than half of the patients in the follow-up.On the other hand,DFPN could be related with a temporary reason(thermal,physical or drug effect etc.)in some patients who do not exhibit any associated disease.Head-shaking testing is recommended to expose the lateral canal BPPV.But the incidence is low.

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.