Ocular counter-rolling in scuba divers with motion sickness.

OBJECTIVE: Motion sickness (MS) is a familiar condition to scuba divers. The purpose of this study was to compare otolith organ function of scuba divers who have MS to those without MS. METHOD: Video-oculography (VOG) goggles were used to measure video ocular counter-roll (vOCR) in 50 healthy scuba divers with no vestibular pathology. Divers with MS (n = 30) had Graybiel motion sickness (GMS) scores of ≥1 point, and divers without MS (n = 20) had GMS scores of 0. Divers with MS also completed the Motion Sickness Susceptibility Questionnaire short form (MSSQs). For all divers, otolith-ocular function of both ears was tested separately via vOCR testing, which was performed during 30° head tilt. An R-L side asymmetry ratio for vOCR values (%OCRA) was compared to divers' static OCR. RESULTS: MSSQs and %OCRA scores differed significantly (p<0.01and p<0.001, respectively) between divers with MS and divers without MS. Their %OCRA scores and severity of MS were significantly correlated. Female divers were more susceptible to MS. ROC analysis for %OCRA revealed that the AUC for divers with MS and divers without MS was 0.8967 (95% CI, 0.8114 to 0.9819), the specificity was 1.000, and the sensitivity was 0.700, with a cutoff value of 45.946. CONCLUSION: Physiological differences between R-L otolith organ function could affect the severity and susceptibility to MS. Female hormones may also increase susceptibility to MS. Thus, MS may be a physiological phenomenon induced by functional ear differences in the absence of pathology. As MS is caused by multiple factors, otolaryngologists need to consider various causative factors beyond those related to otolith organ function in scuba divers with MS.

Superior canal dehiscence syndrome associated with scuba diving.

A 28-year-old female diver presented with dizziness and difficulty clearing her left ear whilst scuba diving. Her pure-tone audiometry and tympanometry were normal. Testing of Eustachian tube function revealed tubal stenosis. Video-oculography revealed a predominantly torsional nystagmus while the patient was in the lordotic position. Fistula signs were positive. High-resolution computed tomography (HRCT) of the temporal bone revealed a diagnosis of bilateral superior semicircular canal dehiscence (SCDS). Cervical vestibular-evoked myogenic potential (cVEMP) testing showed that the amplitude of the cVEMP measured from her left ear was larger than that from the right. In electronystagmography (ENG), nose-pinched Valsalva manoeuvres caused eye movements to be mainly directed counterclockwise with a vertical component. Tullio phenomenon was also positive for both ears. SCDS patients tend to be misdiagnosed and misunderstood; common misdiagnoses in these cases are alternobaric vertigo (AV), inner ear barotrauma, and inner-ear decompression sickness. It is difficult to diagnose vertigo attacks after scuba diving as SCDS; however, when the patient develops sound- and/or pressure-induced vertical-torsional nystagmus, HRCT should be conducted to confirm a diagnosis of SCDS.

Quantitative analysis of inner-ear barotrauma using a Eustachian tube function analyzer.

OBJECTIVES: We investigated the relationship between Eustachian tube function and incidence of inner-ear barotrauma (IEBt) in recreational divers. METHODS: Sixteen patients who experienced a scuba diving injury affecting the inner ear and 20 healthy volunteers who had not experienced a diving injury participated. Healthy volunteers and divers with IEBt received impedance tests regularly to assess Eustachian tube function. Test results from these groups were compared. RESULTS: There were no significant differences between test results of IEBt divers and healthy volunteers. However, seven IEBt divers were judged to have irregular compliance curves on impedance testing. Seven of the 16 IEBt divers experienced vertigo. In nearly all of the IEBt divers with vertigo, hearing loss type was manifested as high-tone deafness, and IEBt symptoms appeared during diving. These symptoms were more serious especially when the diving depth was deeper. CONCLUSIONS: To prevent IEBt in scuba divers, we recommend a thorough Eustachian tube function evaluation. Any dysfunction should be treated before engaging in scuba diving. We need to assess more divers who have experienced IEBt and thoroughly examine how their injury happened.

A case of patulous Eustachian tube associated with dizziness induced by nasal respiration.

OBJECTIVE: To determine the relationship between Eustachian tube function and inner ear function in patulous Eustachian tube (pET). METHODS: We encountered a patient with pET accompanied by dizziness that was induced by nasal respiration. Eye movements were recorded using video-oculography, and Eustachian tube function was assessed using a Eustachian tube function analyzer. Horizontal and vertical components of pupil position were assessed to test fixation, positional, and positioning nystagmus. Impedance testing with a Eustachian tube function analyzer was performed to confirm tympanometry results. We recorded these outcomes until the patient's symptoms improved. RESULTS: When pET improved, the patient's symptoms were alleviated. CONCLUSION: The present pET patient had mild vestibular symptoms. Therefore, pET patients with dizziness might be misdiagnosed with, for example, superior semicircular canal dehiscence, psychogenic vertigo, or Ménière's disease. For patients with few clinical symptoms or laboratory findings, clinicians need to consider dizziness-induced pET as a possible diagnosis.

Altered eustachian tube function in SCUBA divers with alternobaric vertigo.

OBJECTIVES: The number of people participating in sport self-contained underwater breathing apparatus (SCUBA) diving has increased tremendously, bringing with it a rise in diving accidents. Alternobaric vertigo (AV) is a common problem in SCUBA divers. We investigated the relationship between Eustachian tube function and incidence of AV in sport SCUBA divers. We also followed the progress of these divers after Eustachian tube function improved. METHOD: Forty-four patients who experienced a SCUBA diving accident affecting the middle ear (11 men and 33 women; mean ± SD: 37.5 ± 11.5 yr) and 20 healthy volunteer divers who did not experience an accident (6 men and 14 women; mean ± SD: 33.5 ± 13.9 yr) were compared. We divided the divers with an accident into two groups (those with AV vs. those without) and then compared the two groups. All patients regularly underwent Eustachian tube function tests (sonotubometry and impedance test). RESULTS: In sonotubometry and impedance testing, the mean duration (p < 0.001), amplitude (p < 0.002), and maximum air content (p < 0.05) of divers who experienced a diving accident were significantly different from those of healthy volunteers. However, these parameters in divers with AV did not differ significantly from those in divers without AV. In 7 of 15 divers, vestibular symptoms disappeared immediately after ascent. In the remaining eight divers, however, vertigo/dizziness persisted and even was observed at their first clinic visit. CONCLUSION: To prevent AV or barotraumas in SCUBA divers, we recommend a thorough Eustachian tube function evaluation. Any dysfunction should be treated before engaging in SCUBA diving.

Auditory-pupillary responses in patients with vestibular neuritis.

Pupillary dilation in response to sound stimuli is well established and generally represents a startle reflex to sound. We previously reported that auditory-pupillary responses (APRs) persist with bilateral deafness, and that the pathways mediating APRs involve not only the cochlea but also otolith organs, especially the saccule. Here, we evaluated the vestibulo-autonomic responses in vestibular neuritis (VN) by assessing APRs. Twelve young healthy volunteers without a history of hearing and equilibrium problems and 10 VN patients participated. To clarify the relationship between APRs and vestibular function, especially otolith function, we performed caloric and vestibular-evoked myogenic response testing on VN patients. In normal subjects, we examined APRs when delivering sound stimuli to both sides. In VN patients, we examined APRs when delivering stimuli simultaneously to both sides, to the affected side alone, and then to the unaffected side alone. With binaural stimulation, the pupillary index (PI) - the rate of dilation - of VN patients significantly differed from those of normal subjects. Moreover, in VN patients, PIs of the affected sides were significantly larger than those of the unaffected sides. Our study provides evidence that examining APRs may be useful for evaluating vestibulo-autonomic reflexes, especially otolith-autonomic reflexes.

[A study of the Eustachian tube function in patients with a scuba diving accident].

The scuba diving population has increased very much recently, bringing with it a rise in barotrauma. Ninety-seven patients with scuba diving-related accidents (34 males and 63 females; mean +/- SD: 36.6 +/- 10.3 years) and 39 healthy volunteers (9 males and 30 females; mean +/- SD: 41.1 +/- 16.9 years) without a history of Eustachian tube dysfunction participated in this study. All patients underwent audiometric measurements, including hearing testing, tympanometry, and Eustachian tube function testing (sonotubometry and impedance test). The tympanometry results of the majority of the patients were normal (Jerger A type), however, 83 of 97 patients (85.6%) were diagnosed as having Eustachian tube dysfunction: all patients had tubal stenosis. Compared with healthy volunteers, the Eustachian tube function in scuba diving patients was significantly lower. According to whether the affected parts were one ear or both ears, we classified these patients into 2 types, that is, the unilateral group and the bilateral group. The symptoms in the unilateral group were more serious than those in the bilateral group. In the unilateral group, the Eustachian tube functions of the affected ear did not always show lower than those of the healthy ear, so we thought that excessive positive pressure at the mesotympanum caused by the Valsalva maneuver might have affected not only the affected ear but also the healthy ear and have resulted in healthy ears being severely impaired by excessive positive pressure. To prevent scuba divers from pressure injury, we think that divers should have their Eustachian tube dysfunction accurately evaluated and any problems should be treated well.

Eustachian tube function in patients with Meniere's disease.

OBJECTIVE: The aim of the present study was to clarify the relationship between Eustachian tube function and inner ear function, especially with respect to the hearing ability of patients with Meniere's disease. METHODS: Patients with Meniere's disease underwent nystagmic examinations and audiometric measurements, including hearing tests, tympanometry, and Eustachian tube function tests (sonotubometry). We compared the audiometric examination results of normal subjects to those of patients with Meniere's disease. RESULTS: Twenty-five percent of patients with Meniere's disease exhibited Eustachian tube dysfunction, but 92% displayed normal tympanometry findings. Their sonotubometry durations and amplitudes were not significantly different from those of normal subjects. However, the patients' hearing level was significantly correlated to sonotubometry duration and amplitude. Our patients were classified according to the four stages of Meniere's disease: stage 1 (n=9); stage 2 (n=5); stage 3 (n=8); and stage 4 (n=2). The incidence of Eustachian tube dysfunction in these four groups of patients were 0% (0/9); 40% (2/5); 38% (3/8); and 50% (1/2), respectively. CONCLUSION: Our study provides evidence demonstrating that treatment of Eustachian tube dysfunction may be useful in preventing the hearing of Meniere's patients from becoming worse.

Auditory-pupillary responses in deaf subjects.

Pupillary dilation in response to sound stimuli is well established and is generally considered to represent a startle reflex to sound. We believe that the auditory-pupillary response represents not only a simple startle reflex to sound stimuli but also represents a reaction to stimulation of other sense organs, such as otolith organs. Eight young healthy volunteers without a history of hearing and equilibrium problems and 12 subjects with bilateral deafness participated in this study. Computer pupillography was used to analyze the auditory-pupillary responses of both eyes in all subjects. We found that auditory-pupillary responses occurred even in subjects with bilateral deafness and that this response was comparable to those of normal subjects. We propose that the auditory-pupillary response also relates to vestibular function. Thus, assessing the auditory-pupillary response may be useful for evaluating the vestibulo-autonomic response in patients with peripheral disequilibrium.

Positional and positioning down-beating nystagmus without central nervous system findings.

We report the clinical features of 4 cases with positional or positioning down-beating nystagmus in a head-hanging or supine position without any obvious central nervous system disorder. The 4 cases had some findings in common. There were no abnormal findings on neurological tests or brain MRI. They did not have gaze nystagmus. Their nystagmus was observed only in a supine or head-hanging position and it was never observed upon returning to a sitting position and never reversed. The nystagmus had no or little torsional component, had latency and tended to decrease with time. The positional DBN (p-DBN) is known to be indicative of a central nervous system disorder. Recently there were some reports that canalithiasis of the anterior semicircular canal (ASC) causes p-DBN and that patients who have p-DBN without obvious CNS dysfunction are dealt with anterior semicircular canal (ASC) benign paroxysmal positional vertigo (BPPV). There are some doubts as to the validity of making a diagnosis of ASC-BPPV in a case of p-DBN without CNS findings. It is hard to determine the cause of p-DBN in these cases.

Properties and axonal trajectories of posterior semicircular canal nerve-activated vestibulospinal neurons.

We studied the axonal projections of vestibulospinal neurons activated from the posterior semicircular canal. The axonal projection level, axonal pathway, and location of the vestibulospinal neurons originating from the PC were investigated in seven decerebrated cats. Selective electrical stimulation was applied to the PC nerve, and extracellular recordings in the vestibular nuclei were performed. The properties of the PC nerve-activated vestibulospinal neurons were then studied. To estimate the neural pathway in the spinal cord, floating electrodes were placed at the ipsilateral (i) and contralateral (c) lateral vestibulospinal tract (LVST) and medial vestibulospinal tract (MVST) at the C1/C2 junction. To elucidate the projection level, floating electrodes were placed at i-LVST and MVST at the C3, T1, and L3 segments in the spinal cord. Collision block test between orthodromic inputs from the PC nerve and antidromic inputs from the spinal cord verified the existence of the vestibulospinal neurons in the vestibular nuclei. Most (44/47) of the PC nerve-activated vestibulospinal neurons responded to orthodromic stimulation to the PC nerve with a short (<1.4 ms) latency, indicating that they were second-order vestibulospinal neurons. The rest (3/47) responded with a longer (>/=1.4 ms) latency, indicating the existence of polysynaptic connections. In 36/47 PC nerve-activated vestibulospinal neurons, the axonal pathway was histologically verified to lie in the spinal cord. The axons of 17/36 vestibulospinal neurons projected to the i-LVST, whereas 14 neurons projected to the MVST, and 5 to the c-LVST. The spinal segment levels of projection of these neurons elucidated that the axons of most (15/17) of vestibulospinal neurons passing through the i-LVST reached the L3 segment level; none (0/14) of the neurons passing through the MVST extended to the L3 segment level; most (13/14) of them did not descend lower than the C3 segment level. In relation to the latency and the pathway, 33/36 PC nerve-activated vestibulospinal neurons were second-order neurons, whereas the remaining three were polysynaptic neurons. Of these, 33 second-order vestibulospinal neurons, 16 passed through the i-LVST, while 13 and 4 descended through the MVST and c-LVST, respectively. The remaining three were polysynaptic neurons. Histological analysis showed that most of the PC nerve-activated vestibulospinal neurons were located within a specific area in the medial part of the lateral vestibular nucleus and the rostral part of the descending vestibular nucleus. In conclusion, it was suggested that PC nerve-activated vestibulospinal neurons that were located within a focal area of the vestibular nuclei have strong connections with the lower segments of the spinal cord and are related to postural stability that is maintained by the short latency vestibulospinal reflex.

A case of acute disseminated encephalomyelitis presenting with vertigo.

We report a 37-year-old woman with acute disseminated encephalomyelitis (ADEM) who presented with progressive vertigo. A central nervous system disorder was initially suspected because gaze-evoked torsional nystagmus was observed and electrical nystagmography (ENG) revealed abnormal eye movements with saccadic ocular pursuit and pathological optokinetic nystagmus. Finally ADEM was diagnosed by the clinical symptoms and the characteristic patterns of brain MRI. It is rare for otolaryngologists to examine patients with ADEM. ADEM takes an acute course and can present a grave state and therefore needs early diagnosis, early treatment. We have to keep ADEM in mind in the diagnosis of vertigo.

Axonal pathways and projection levels of anterior semicircular canal nerve-activated vestibulospinal neurons in cats.

Using collision tests of orthodromically and antidromically generated spikes, we studied the axonal pathways, axonal projection levels, and soma location of anterior semicircular canal (AC) nerve-activated vestibulospinal neurons in decerebrate cats. AC nerve-activated vestibulospinal neurons (n=74) were mainly located in the ventral portion of the lateral vestibular nuclei and the rostral portion of the descending vestibular nucleus, which is consistent with previous studies. Of these neurons, 15% projected through the ipsilateral (i-) lateral vestibulospinal tract (LVST), 74% projected through the medial vestibulospinal tract (MVST), and 11% projected through the contralateral (c-) LVST. The vast majority (78%) of AC nerve-activated vestibulospinal neurons were activated antidromically only from the cervical segment of the spinal cord; 15% of neurons were activated from the T1 segment and only one neuron was activated from the L3 segment. AC nerve-activated vestibulospinal neurons may primarily target the neck muscles and thus contribute to the vestibulocollic reflex. Most of the c-LVST neurons were also activated antidromically from the oculomotor nucleus, suggesting that they are closely related to the control of combined eye-head movements.

Model experiments of BPPV using isolated utricle and posterior semicircular canal.

OBJECTIVES: This study was aimed to experimentally investigate the effect of returned otoconia on the utricular using isolated utricles. The effect of interposed otoconia in models of canalolithiasis and cupulolithiasis were also investigated using isolated posterior semicircular canal (PSC). METHODS: Bullfrogs were used. The utricles (Experiment I) and PSC (Experiment II) were removed in Ringer solution. Experiment I-a: The otoconia were carefully removed from the utricular macula with gentle flush of Ringer solution. Before and after the otoconial removal, sinusoidal rotatory stimulation (0.1 Hz, 135 degrees ) was given to record utricular compound action potentials (CAPs). Experiment I-b: (1) Instantaneous changes in the utricular potentials when the otoconial mass was positioned on the macula were recorded. (2) Utricular CAP changes in response to sinusoidal rotation immediately and 10 min after the otoconial positioning were recorded. Experiment II: PSC CAPs due to sinusoidal rotatory stimulation in normal specimen, canalolithiasis and cupulolithiasis models were recorded. RESULTS: Experiment I-a: The utricular CAPs in response to sinusoidal rotation showed sinusoidal oscillation. However, this oscillation disappeared after the otoconial removal. Experiment I-b: (1) The utricular potentials transiently increased for 3-4 s after positioning the otoconial mass. (2) The utricular CAPs increased in seven specimens and decreased in four. Ten minutes after the CAPs were almost the same as immediately after otoconial positioning. Experiment II: In cupulolithiasis model, the PSC CAPs decreased in all specimens. CONCLUSIONS: The otoconia played an essential role as a transducer of acceleration to the utricular macula. Otoconia returned to the utricular macula change utricular reactivity and hence are the possible cause of dizziness after physical therapy. PSC responses to sinusoidal rotation were suppressed in cupulolithiasis model.

Properties of horizontal semicircular canal nerve-activated vestibulospinal neurons in cats.

Axonal pathways, projection levels, and locations of horizontal semicircular canal (HC) nerve-activated vestibulospinal neurons were studied. The HC nerve was selectively stimulated. Vestibulospinal neurons were activated antidromically with four stimulating electrodes, inserted bilaterally into the lateral vestibulospinal tracts (LVST) and medial vestibulospinal tracts (MVST) at the C1/C2 junction. Stimulating electrodes were also positioned in the C3, T1, and L3 segments and in the oculomotor nuclei. Most HC nerve-activated vestibulospinal neurons were located in the ventral portion of the medial, lateral, and the descending nuclei. Among the 157 HC nerve-activated vestibular neurons, 83 were antidromically activated by stimulation at the C1/C2 junction. Of these 83 neurons, axonal pathways of 56 HC nerve-activated vestibulospinal neurons were determined. Most (48/56) of these had axons that descended through the MVST, with the remainder (8 neurons) having axons that descended through the ipsilateral (i-) LVST. Laterality of the axons' trajectories through the MVST was investigated. The majority of vestibulospinal neurons (24/28) with axons descending through the contralateral MVST were also antidromically activated from the oculomotor nucleus, whereas almost all vestibulospinal neurons (19/20) with axons descending through the i-MVST were not. Most HC nerve-activated vestibulospinal neurons were activated antidromically only from the C1/C2 or C3 segments. Only one neuron that was antidromically activated from the T1 segment had an axon that descended through the i-LVST. None of the HC nerve-activated vestibulospinal neurons were antidromically activated from the L3 segment. It is likely that the majority of HC nerve-activated vestibulospinal neurons terminate in the cervical cord and have strong connections with neck motoneurons.

Changes in the Tullio phenomenon and the fistula sign in the course of endolymphatic hydrops.

We performed electronystagmography with caloric stimulation and studied vestibular evoked myogenic potentials (VEMPs) associated with changes in the Tullio phenomenon and the fistula sign during the clinical course of a patient with endolymphatic hydrops. The Tullio phenomenon and the fistula sign disappeared in association with a reduction in the caloric response, which implicates the ampullary function of the lateral semicircular canal. Even when no VEMP could be detected for the affected ear, the Tullio phenomenon and fistula signs were observed; thus, either these phenomena had a lower response threshold than the VEMPs, or saccular receptors were not involved in the Tullio phenomenon.