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Concept: Horizontal semicircular canal

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Spontaneous nystagmus, which has been considered a typical sign of acute vestibulopathy, has recently been reported in benign paroxysmal positional vertigo involving the lateral semicircular canals (LC-BPPV) without unilateral vestibulopathy (pseudo-spontaneous nystagmus, PSN), but research about its clinical application is still limited. Here we investigate the frequency and characteristics of PSN in LC-BPPV patients, and estimate its prognostic value.

Concepts: Medical terms, Semicircular canal, Prognosis, Ear, Canal, Pathologic nystagmus, Benign paroxysmal positional vertigo, Horizontal semicircular canal

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OBJECTIVE: The relatively low success rate of the treatment maneuver for horizontal semicircular canal (HSC) benign paroxysmal positional vertigo (BPPV) may be caused by the difficulty determining the affected side. We developed a 180-degree supine roll test (SRT) by modifying the 90-degree SRT to increase diagnostic accuracy and evaluated its significance. STUDY DESIGN: A prospective study. SETTING: Tertiary referral center. PATIENTS: A total of 122 patients with HSC-BPPV performed both the 90- and 180-degree SRTs. INTERVENTIONS: The affected side was determined by the 90- and 180-degree SRTs. The bow and lean (BL) test was also performed in cases with ambiguous or opposite results on both SRTs. MAIN OUTCOME MEASURE: A comparison of the difference in slow phase velocity (SPV) of nystagmus among the 90- and 180-degree SRTs and BL test. RESULTS: The maximum SPV of nystagmus during the 180-degree SRT was significantly greater than that during the 90-degree SRT. The SPV difference was less in the 180-degree SRT than that in the 90-degree SRT. Although the 180-degree SRT showed fewer meaningful results (n = 65) than the 90-degree SRT (n = 71), the affected side was determined by the 180-degree SRT in 15 cases with ambiguous results on the 90-degree SRT. Among 10 cases showing opposite results, 7 were identified by the BL test. Five (71.4%) of 7 cases had consistent affected sides with the 180-degree SRT. CONCLUSION: The 180-degree SRT can be an additional method when it is difficult to determine the affected side from the 90-degree SRT.

Concepts: Measurement, Semicircular canal, Arithmetic, Ear, Determinacy, Pathologic nystagmus, Benign paroxysmal positional vertigo, Horizontal semicircular canal

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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.

Concepts: Semicircular canal, Explanation, Ear, The Current, Pathologic nystagmus, Characteristic, Benign paroxysmal positional vertigo, Horizontal semicircular canal

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The labyrinth has two functional parts: the cochlea for audition and the vestibular system for equilibrioception. In the latter, the semicircular ducts and the otolithic organs are sensitive to rotational and linear accelerations of the head, respectively. The labyrinthine morphology influences perception accuracy, hence the adaptation to a specific locomotor pattern. The aim of this study is to determine the relationship between locomotion and semicircular canal morphology using geometric morphometrics, and to explain these links with existing functional models. The influence of factors other than functional constraints on labyrinthine morphology is discussed. The left bony labyrinth of 65 specimens was extracted virtually. Five extant hominoid species with various locomotion modes were sampled. A set of 13 landmarks was placed on the semicircular canals. After a Procrustes fit, their coordinates were analyzed using a principal component analysis. It was found that labyrinthine morphology is significantly distinct between species. More specifically, the differences involve a posterolateral projection of the lateral semicircular canal and the rotation of this canal relative to the vertical canals. This rotation occurs in the sagittal plane, which is consistent with previous studies based on traditional morphometrics. Among extant hominoids, the shape of the canals potentially discriminates species based on posture. This result could be used to reconstruct the locomotor pattern of fossil hominoids.

Concepts: Vestibular system, Principal component analysis, Semicircular canal, Inner ear, Posterior semicircular canal, Horizontal semicircular canal, Labyrinth, Knossos

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To demonstrate positional nystagmus during a head-roll test in two patients with lateral semicircular canal (LSCC) cupulolithiasis who presented with spontaneous detachment of otoliths from the LSCC cupula, and to confirm that otoliths may adhere to both the utricle and canal sides of the cupula.

Concepts: Semicircular canal, Horizontal semicircular canal

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We report a new syndrome, which we are calling head-jolting nystagmus, that expands the differential diagnosis of head movement-induced paroxysmal vertigo.

Concepts: Medical terms, Medical diagnosis, Semicircular canal, Differential diagnosis, Horizontal semicircular canal

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A short clinical course and frequent recurrence are common features of persistent geotropic direction-changing positional nystagmus with neutral position (positional nystagmus of light cupula: PNLC) and cupulolithiasis of the lateral semicircular canal. It is suggested that PNLC is caused by light debris attached to the cupula of the lateral semicircular canal.

Concepts: Semicircular canal, Horizontal semicircular canal

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Persistent direction-changing positional nystagmus (DCPN) during the supine head-roll test is a typical finding of cupulopathy. The aim of this study was to introduce a simple method of evaluating patients with cupulopathy (light cupula and heavy cupula), which is performed in a seated position, and investigate its diagnostic utility and use for lateralization.

Concepts: Semicircular canal, Horizontal semicircular canal

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The aim of this paper was to evaluate prospectively, in a group of patients affected by VN, a diagnostic protocol employing C-VEMPs, O-VEMPs and vHIT together. The diagnosis of vestibular neurolabyrinthitis was based on the clinical history, absence of associated auditory or neurological symptoms, and a neuro-otological examination with an evaluation of lateral semicircular canal function using the Fitzgerald-Hallpike caloric vestibular test and ice test. Our series revealed an incidence of 55 % of superior and inferior vestibular neurolabyrinthitis, 40 % of superior vestibular neurolabyrinthitis and 5 % of inferior vestibular neurolabyrinthitis. These data, however, comprised different degrees of vestibular involvement considering the evaluation of each single vestibular end-organ with potential different prognosis. Four patients had only deficits of the horizontal and superior semicircular canals or their ampullary nerves. The implementation of C-VEMPs, O-VEMPs and vHIT in a vestibular diagnostic protocol has made possible to observe patients with ampullary VN, unidentifiable with other types of vestibular exams. The effect of age seems to have some impact on the recovery. When recovery firstly involves the utricular and saccular nerves and subsequently the ampullary nerves, it may be reasonable to expect a more favorable and successful outcome.

Concepts: Medical terms, Diagnosis, Neurology, Vestibular system, Semicircular canal, Canal, Horizontal semicircular canal, Superiority complex

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Lateralization of horizontal semicircular canal benign paroxysmal positional vertigo (HSC-BPPV) is very important for successful repositioning. The directions of lying-down nystagmus (LDN) and head-bending nystagmus (HBN) have been used as ancillary findings to identify the affected sites. This retrospective study was performed to evaluate the lateralizing values of LDN and HBN using clinical and laboratory findings for lateralizing probabilities in patients with HSC-BPPV.

Concepts: Semicircular canal, Pathologic nystagmus, Benign paroxysmal positional vertigo, Horizontal semicircular canal