Sudden-onset vertigo with nausea and/or vomiting is a common clinical symptom of AVS,10 usually first diagnosed and treated in the Emergency Department of Neurology. There are two types of AVS, central vestibular vertigo and peripheral vestibular vertigo, distinguishable by several clinical methods, such as HINTS (Head Impulse, Nystagmus, Test of Skew) and the STANDING (SponTAneous Nystagmus, Direction, head Impulse test, standiNG) algorithm.11,12,13,14 Brain CT and MRI scans are the most reliable auxiliary examinations to distinguish between central and peripheral vestibular vertigo. Cases with sudden-onset vertigo associated with PSTN and imbalance are rare. In this study, Patient 1 had no history of prodromal infection and presented with sudden-onset vertigo associated with PSTN and imbalance after the relief of the BPPV episode, suggesting that the canalith repositioning procedure may be effective. After three CCRM treatments, vertigo, PSTN, and imbalance were alleviated completely, suggesting that this treatment was effective. The following ten patients were also cured after having the same procedure, which confirmed the effectiveness of CCRM for sudden-onset vertigo associated with PSTN and imbalance.
All patients included in this study were excluded for central vestibular vertigo by brain CT and MRI scans. Three of them were diagnosed with BPPV and treated by the canalith repositioning procedure just before sudden-onset vertigo associated with PSTN and imbalance. After several CCRM treatments, all patients presented with the same clinical manifestations as classic BPPV and atypical symptoms of BPPV, such as persistent dizziness, feeling of floating when walking, blurred vision, and head cloudiness.15,16,17,18 The canalith repositioning procedure is an effective therapeutic method for BPPV but not for other types of peripheral vestibular vertigo. The above evidence suggests that sudden-onset vertigo associated with PSTN and imbalance is a unique clinical manifestation of BPPV when central vestibular vertigo is excluded.
The etiology and pathogenesis of sudden-onset vertigo associated with PSTN and imbalance are unclear. Epley et al., initially, observed a sudden conversion of positional nystagmus to a rapid form of spontaneous nystagmus that persists irrespective of the head position. It occurs due to the obstruction of the semicircular canal by free-floating otoliths within the semicircular canal. This phenomenon was defined as canalith jam, a rare complication of the canalith repositioning procedure for posterior semicircular canal canalithiasis.19,20 Canalith jam, caused by the blockage of free-floating particles within a canal, is a complication of BPPV after the canalith repositioning procedure or can develop spontaneously. The potential pathogenic mechanisms of canalith jam are as follows: (1) Canalith jam blocks the flow of the endolymph or the movement of the cupula. (2) Canalith jam results in a negative pressure between the cupula and the jamming point and transiently reduce the vestibulocochlear reflex.21 (3) Canalith jam in a narrow point of the canal blocks the flow of the endolymph and the cupula displacement. The otolithic clump plugs the canal, exerting permanent transcupular pressure that causes persistent spontaneous nystagmus.22 Only a few studies have reported canalith jam. In 2001, von Brevern et al. examined a patient with persistent vertigo and oscillopsia with spontaneous nystagmus beating to the left, and the vestibular function examination showed right horizontal palsy, suggesting horizontal canal plugging. These findings indicated that transient spontaneous nystagmus with unilateral canal palsy was probably due to the plugging of the horizontal canal.23 In 2014, Chang et al. and Ko et al. reported cases with canalith jam in the horizontal semicircular canal following the canalith repositioning procedure.21,24 In 2018, Comacchio et al. reported a case with a canalith jam in the left horizontal semicircular canal.22 No cases with canalith jam in the posterior semicircular canal were reported after the first report by Epley et al. In this study, 3 out of 11 patients had the same clinical manifestations as described by Epley et al. The otoliths fell off and entered the posterior semicircular canal, resulting in canalith jam in the semicircular canal and abnormal endolymphatic flow, which eventually led to severe vertigo, PSTN, and imbalance. The CCRM treatment enables the reposition of otoliths back to the utricle. The relief of vertigo, nystagmus, and imbalance in patients with sudden-onset vertigo associated with PSTN and imbalance after the CCRM treatment could be explained by the pathogenesis of canalith jam. Trauma can induce secondary BPPV. One patient had a history of stumble and trauma before PSTN and imbalance in this study. The symptoms were relieved after the CCRM treatment, indicating that the onset of symptoms was associated with otoliths. In addition, when performing the Epley maneuver and DHH maneuver for bilateral posterior and anterior semicircular canals during the first CCRM treatment, vertigo and nystagmus presented at head positions on both sides, suggesting that otolithiasis in the unilateral or bilateral multiple semicircular canals may be another pathogenic mechanism of sudden-onset vertigo associated with PSTN and imbalance.
The above reported four patients with horizontal semicircular canalith jam underwent vestibular function test. Three of them presented with horizontal semicircular canal palsy,22,23,24 and the remaining one showed reduced vestibular function.21 After the head-shaking and canalith repositioning maneuvers, horizontal semicircular canal palsy disappeared, and the vestibular function returned to normal. Four out of 11 patients underwent vestibular function tests. Three patients showed right horizontal semicircular canal palsy, and one showed left horizontal semicircular canal palsy. These findings suggested that the canalith jam resulted in abnormal vestibular function. After consultation with an otolaryngologist, the four patients with abnormal vestibular function were diagnosed with VN. The CCRM treatment, instead of corticosteroids, was used. All patients recovered after the CCRM treatment. BPPV cannot be excluded when patients with peripheral vestibular vertigo but not cochlear symptoms present with abnormal vestibular function.
VN is the third most common peripheral vestibular neuropathy (after BPPV and Manière’s disease). The main clinical manifestations of VN are vertigo, nausea, and gait imbalance. The etiology and pathogenesis of VN are unknown, though possibly caused by inflammation, labyrinthine ischemia, and type 1 herpes zoster infection.3,4,5 Patients with atypical BPPV (i.e., sudden-onset vertigo and abnormal vestibular function) may be misdiagnosed as VN; therefore, the term “AUPVP” is used in the international classification of vestibular disorders.3,6 As the clinical manifestations of peripheral AVS without cochlear symptoms do not meet the diagnostic criteria of classic BPPV,25,26 the canalith repositioning procedure was not performed in patients. The diagnosis was made based on clinical manifestations and vestibular function examination. Patients with severe vertigo but not cochlear symptoms are often diagnosed with VN. BPPV originating from the posterior semicircular canal often develops as a sequela in patients with VN.22 Türk et al. reported 44 patients with BPPV secondary to VN.27 Mandalà et al. found that the BPPV episode occurred in 5 out of 51 patients with VN during follow-up. H-A Kim, et al. found that 51 cases of patients with VN had at least one otolith-related test abnormality in their study, the causality of abnormal otolith function in the pathogenesis of VN was not analyzed further.28
The above studies suggested that VN and BPPV may share the same etiology and pathogenesis. Moreover, BPPV after VN predominantly affected VN patients who did not fully recover from the disease.29 It should be further investigated whether BPPV following VN diagnosed before was a sequela of VN, or presented with unique manifestations of BPPV and gradually developed typical BPPV. The clinical manifestations of patients in this study were same as those of VN patients. The symptoms were alleviated entirely after the CCRM treatment. The favorable responses after the CCRM treatment in these patients implied that the etiology and pathogenesis of AUPVP(VN) were related to canalith jam in the semicircular canal or otolithiasis in the unilateral or bilateral multiple semicircular canals, but not inflammation, labyrinthine ischemia, or viral infection. Further clinical studies are needed to verify this hypothesis.
No previous study has reported the effectiveness of the CCRM treatment for sudden-onset vertigo associated with PSTN and imbalance. This study used this method because it could not determine whether a single semicircular canal or multiple semicircular canals were involved and which side was involved. The canalith repositioning procedure for the bilateral posterior and anterior semicircular canals was effective for patients with peripheral vestibular vertigo but not cochlear symptoms. Clinicians need to know when, how, and to whom the canalith repositioning procedure should be performed. Also, patients with peripheral vestibular vertigo but not cochlear symptoms should be treated with the canalith repositioning procedure to exclude BPPV. The canalith repositioning procedure should also be performed before diagnosing bilateral vestibulopathy,30 persistent postural perceptual dizziness,31 and presbyvestibulopathy.32 Considering the heterogeneous manifestations of BPPV, the term “otolithiasis” instead of BPPV should be used.