Clinical Characteristics And Recurrence Mechanism Of Traumatic Benign Paroxysmal Positional Vertigo

Part Ⅰ Treatment and Prognosis of Traumatic Benign Paroxysmal Positional Vertigo:a Meta-AnalysisObjective:The etiology of benign paroxysmal positional vertigo(BPPV)is very complex.50%to 70%of the patients have no obvious etiology,which is called primary or idiopathic BPPV(i-BPPV).In addition,part of BPPV cases are secondary,which secondary to craniocerebral trauma,neck trauma,otorhinolaryngology or oral and maxillofacial surgery or neurosurgery and other types of trauma,known as traumatic BPPV(t-BPPV).t-BPPV accounts for 8.5%to 20%of all BPPV cases.However,there is no definite definition of t-BPPV.i-BPPV occurs mostly in the elderly and females.Unilateral single semicircular canal BPPV is the most common type.It is relatively easy to reposition and has a low recurrence rate.Compared with i-BPPV,t-BPPV has several distinctive features,including similar sex ratio,younger onset age peak,higher incidence of bilateral BPPV,higher incidence of multiple semicircular canal(MSC)involvement,greater difficulty in repositioning treatment and higher recurrence rate.However,some other studies suggest that t-BPPV is not significantly different from i-BPPV in terms of the difficulty of reposition and recurrence rate.Although vertigo or dizziness are common symptoms after trauma and BPPV is also a common vertigo disease after trauma,clinical research on t-BPPV is poor and unsystematic.Cohort studies about comparision of the characteristics of t-BPPV and i-BPPV are less.To this end,we use meta-analysis method to include all cohort studies that meet the inclusion criteria and increase the sample size of the study in order to obtain reliable conclusions about the difference between t-BPPV and i-BPPV in treatment and prognosis,so as to guide clinical treatment and prognosis evaluation.The main purpose of this study is to analyze the difference between t-BPPV and i-BPPV in the repositioning difficulty and recurrence rate,and the secondary purpose is to analyze the difference between t-BPPV and i-BPPV in the proportion of MSC-BPPV and bilateral BPPV.Methods:A literature search was performed in the databases including Pubmed,Embase,CENTRAL to compare t-BPPV and i-BPPV.The search strategy was composed of combinations of the keywords including ’benign paroxysmal positional vertigo’,’traumatic’ and ’idiopathic’.All literatures were published up to January 21,2019,with no restriction of publication language.All studies were examined to exclude irrelevant articles through browse of titles and abstracts and full-text reading.Additionally,references of the included literatures on the searching tails were retrieved manually.The literature search process was carried out by two independent investigators.All studies fulfilling the following criteria were included:(1)type of study must be retrospective or prospective cohort study comparing t-BPPV and i-BPPV groups;(2)the diagnosis of BPPV must be clear and conformed to one of the following:(a)proper positioning test maneuvers specially described or mentioned;(b)diagnosis relied on experienced neurologists or otolaryngologists;(3)the time interval between the occurrence of trauma and typical positional vertigo or the diagnosis of BPPV must be clearly stated up to 3 months.(4)outcomes about numbers of patients who needed>2 repositioning maneuvers and who had recurrent attacks were stated by the studies;(5)follow-up time was no less than 6 months.Date extraction was performed by two independent reviewers and consensus was reached on all details by discussion.All statistical process of our meta-analysis was performed using software RevMan 5.3.3.Relative risk(RR)and its 95%confidence interval were used to evaluate the difference of treatment and prognostic characteristics between t-BPPV and i-BPPV(the main observational indicators were the repositioning difficulty and the recurrence rate,and the secondary observational indicators were the proportion of MSC-BPPV and bilateral BPPV).Results:Six articles included in this meta-analysis,including 865 t-BPPV patients and 3027 i-BPPV patients,were retrospective cohort studies.By using meta-analysis method,the repositioning difficulty,recurrence rate,proportion of MSC-BPPV and proportionof bilateral BPPV were compared between t-BPPV and i-BPPV.In terms of the repositioning difficulty,six papers were included.According to the forest plots(I2=93%,P<0.000001),the heterogeneity wassignificant.The RR value calculated using random-effect model was 3.27(95%CI:1.88-5.69,p<0.0001),suggesting that there was a significant difference between t-BPPV and i-BPPV in the repositioning difficulty.In the sensitivity analysis,consistent results were obtained after removing every study one by one,reflecting the reliability of our conclusion above.After removal of the study of Pisani et al.,the heterogeneity became insignificant(X2=1.89,p=0.76,I2=0%),but after removal of each of the other studies,there was little change in heterogeneity,suggesting that the source of high heterogeneity in this meta-analysis was from study of Pisani et al.In terms of recurrence rate,six literatures were included.According to the forest plots(I2-62%,p=0.02),the heterogeneity was significant.The RR value calculated using random-effect model was 2.91(95%CI:2.04-4.14,p<0.00001),suggesting that the recurrence rate of t-BPPV was significantly different from that of i-BPPV.In the sensitivity analysis,consistent results were obtained after removing every study one by one,reflecting the reliability of our conclusion above.After removal of the study of Ahn et al,the heterogeneity became insignificant(X2=4.00,p=0.41,I2=0%),but after removal of each of the other studies,there was little change in heterogeneity,suggesting that the source of high heterogeneity in this meta-analysis was from study of Ahn et al..In terms of the proportion of MSC-BPPV,four papers were included.According to the forest plots(I2=59%,p=0.06),the heterogeneity was significant.The RR value calculated using random-effect model was 2.91(95%Cl:1.55-5.47,p=0.0009),suggesting that there was a significant difference between t-BPPV and i-BPPV in the proportion of MSC-BPPV.In the sensitivity analysis,consistent results were obtained after removing every study one by one,reflecting the reliability of our conclusion above.After removal of the study of Liu et al,the heterogeneity became insignificant(X2=1.75,p=0.42,I2= 0%),but after removal of each of the other studies,there was little change in heterogeneity,suggesting that the source of high heterogeneity in this meta-analysis was from study of Liu et al..In terms of the proportion of bilateral BPPV,five papers were included.According to the forest plots(I2=28%,p=0.24).the heterogeneity was insignificant.The RR value calculated using fixed-effect model was 3.37(95%CI:1.86-6.10,p<0.0001),suggesting that there was a significant difference between t-BPPV and i-BPPV in the proportion of bilateral BPPV.Conclusions:The meta-analysis showed that there were significant differences between t-BPPV and i-BPPV in four aspects:difficulty of repositioning treatment,recurrence rate,proportion of MSC-BPVV and proportion of bilateral BPPV.Compared to i-BPPV,t-BPPV need more repositioning maneuvers to treat,and the recurrence rate,proportion of MSC-BPVV and proportion of bilateral BPPV are higher.In view of the above characteristics of t-BPPV,we should be more patient and meticulous in clinical examination,and instruct patients to follow up regularly.For t-BPPV patients with frequent recurrences,vestibular function,especially otolith function,should be improved.This meta-analysis has many limitations,therefore,in the future,we need to design more rigorous prospective cohort studies to further explore the treatment and prognostic characteristics of t-BPPV.Part Ⅱ Otolith dysfunction in recurrent benign paroxysmal positional vertigo after mild traumatic brain injuryObjective:The pathogenesis of recurrence of traumatic benign paroxysmal positional vertigo(BPPV)is poorly understood by far.One study speculated that the frequent recurrences may be due to microscopic hemorrhages or tissue shearing,resulting in biochemical changes that may reactivate the production of new otoconial clots,but this hypothesis lacked of microscopic evidences to support.A murine traumatic BPPV study showed that long-term gradual detachment of otoconia analysing with scanning electron microscopy resulted in recurrent BPPV attacks,so secondary otolith dysfunction,expecial utricular dysfunction may be a potential pathogenesis of recurrence of traumatic BPPV.Therefore,we tried to evaluate the value of secondary otolith dysfunction using vestibular evoked myogenic potential(VEMP)test in the pathogenesis of recurrence of BPPV after mild traumatic brain injury(mTBI).Methods:We reviewed 42 patients with BPPV after mTBI.According to recurrence,patients were divided into two groups.The non-recurrent group included 27 patients who had no recurrence,while the recurrent group included 15 patients who had at least one recurrence during a minimum 1 year follow-up.Both cervical VEMP(cVEMP)and ocular VEMP(oVEMP)tests were performed on all of them.Results:Between the recurrent and non-recurrent BPPV group after mTBI,the differences in age,sex ratio,BPPV type,ratio of multiple-canal BPPV,BPPV side or ratio of bilateral BPPV were not significant(p>0.05).We detected abnormal cVEMP responses in 4(26.7%)patients in the recurrent BPPV group after mTBI and 5(18.5%)patients in the non-recurrent BPPV group after mTBI,and there was no significant difference between both groups.We detected abnormal oVMEP responses in 9(60.0%)patients in the recurrent BPPV group after mTBI and 6(22.2%)patients in the non-recurrent BPPV group after mTBI,and there was a significant difference between both groups.Conclusions:Our study shows that abnormal cVEMP responses in 4(26.7%)patients in the recurrent BPPV group after mTBI and 5(18.5%)patients in the non-recurrent BPPV group after mTBI,and there was no significant difference between both groups(p>0.05).oVEMP abnormalities in recurrent BPPV group after mTBI are significantly higher than those in non-recurrent BPPV group after mTBI.Therefore,we can conclude that secondary utricular dysfunction may be a potential pathogenesis of recurrence of traumatic BPPV.