Assessments of Subjective Visual Gravity and Spontaneous Nystagmus in Patients With Vestibular Neuritis

OBJECTIVE

This study aimed to assess the correlation between the spontaneous nystagmus (SN) and the subjective visual vertical/horizontal (SVV/SVH) among patients with vestibular neuritis (VN) at the different head positions.

STUDY DESIGN

Case-control study.

SETTING

Affiliated Sixth People's Hospital, Shanghai Jiao Tong University School of Medicine.

METHODS

This study evaluated the SVV/SVH in both healthy subjects and patients with VN. These evaluations were performed in 5 different head positions: upright, 45° tilt to the left, 90° tilt to the left, 45° tilt to the right, and 90° tilt to the right. Additionally, the intensity of SN, as measured by slow-phase velocity, was recorded.

RESULTS

In patients with VN, a significant correlation was observed between SN and SVV/SVH in an upright position. The intensity of SN was higher when the head was tilted 90° toward the affected side compared to other positions. The SVV/SVH displayed an ipsiversive shift, when the head was tilted toward both the lesion and unaffected sides, exhibiting a contraversive direction. Furthermore, the changes in position-induced SN were consistent with the displacements of SVV and SVH caused by head tilt.

CONCLUSION

The presence of SN in patients with VN was observed to vary across different head position. These variations could potentially be attributed to the diverse activation patterns of the mechanical properties of otolith organs that are induced by head tilts.

Characteristics of spontaneous nystagmus and its correlation to video head impulse test findings in vestibular neuritis

Objective

To explore the direction and SPV (slow phase velocity) of the components of spontaneous nystagmus (SN) in patients with vestibular neuritis (VN) and the correlation between SN components and affected semicircular canals (SCCs). Additionally, we aimed to elucidate the role of directional features of peripheral SN in diagnosing acute vestibular syndrome.

Materials and methods

A retrospective analysis was conducted on 38 patients diagnosed with VN in our hospital between 2022 and 2023. The direction and SPV of SN components recorded with three-dimensional videonystagmography (3D-VNG) and the video head impulse test (vHIT) gain of each SCC were analyzed as observational indicators. We examined the correlation between superior and inferior vestibular nerve damage and the direction and SPV of SN components, and vHIT gain values in VN patients.

Results

The median illness duration of between symptom onset and moment of testing was 6 days among the 38 VN patients (17 right VN and 21 left VN). In total, 31 patients had superior vestibular neuritis (SVN), and 7 had total vestibular neuritis (TVN). Among the 38 VN patients, all had horizontal component with an SPV of (7.66 ± 5.37) °/s, 25 (65.8%) had vertical upward component with a SPV of (2.64 ± 1.63) °/s, and 26 (68.4%) had torsional component with a SPV of (4.40 ± 3.12) °/s. The vHIT results in the 38 VN patients showed that the angular vestibulo-ocular reflex (aVOR) gain of the anterior (A), lateral (L), and posterior (P) SCCs on the ipsilesional side were 0.60 ± 0.23, 0.44 ± 0.15 and 0.89 ± 0.19, respectively, while the gains on the opposite side were 0.95 ± 0.14, 0.91 ± 0.08, and 0.96 ± 0.11, respectively. There was a statistically significant difference in the aVOR gain between the A-, L-SCC on the ipsilesional side and the other SCCs (p < 0.001). The aVOR gains of A-, L-, and P-SCC on the ipsilesional sides in 31 SVN patients were 0.62 ± 0.24, 0.45 ± 0.16, and 0.96 ± 0.10, while the aVOR gains on the opposite side were 0.96 ± 0.13, 0.91 ± 0.06, and 0.98 ± 0.11, respectively. There was a statistically significant difference in the aVOR gain between the A-, L-SCC on the ipsilesional side and the other SCCs (p < 0.001). In 7 TVN patients, the aVOR gains of A-, L-, and P-SCC on the ipsilesional side were 0.50 ± 0.14, 0.38 ± 0.06, and 0.53 ± 0.07, while the aVOR gains on the opposite side were 0.93 ± 0.17, 0.90 ± 0.16, and 0.89 ± 0.09, respectively. There was a statistically significant difference in the aVOR gain between the A-, L-, and P-SCC on the ipsilesional side and the other SCCs (p < 0.001). The aVOR gain asymmetry of L-SCCs in 38 VN was 36.3%. The aVOR gain asymmetry between bilateral A-SCCs and bilateral P-SCCs for VN patients with and without a vertical upward component was 12.8% and 8.3%, which was statistically significant (p < 0.05). For VN patients with and without a torsional component, the aVOR gain asymmetry of bilateral vertical SCCs was 17.0% and 6.6%, which was statistically significant (p < 0.01). Further analysis revealed a significant positive correlation between the aVOR gain asymmetry of L-SCCs and the SPV of the horizontal component of SN in all VN patients (r = 0.484, p < 0.01), as well as between the asymmetry of bilateral vertical SCCs and the SPV of torsional component in 26 VN patients (r = 0.445, p < 0.05). However, there was no significant correlation between the aVOR gains asymmetry of bilateral A-SCCs and P-SCCs and the SPV of the vertical component in 25 VN patients.

Conclusion

There is a correlation between the three-dimensional direction and SPV characteristics of SN and the aVOR gain of vHIT in VN patients. These direction characteristics can help assess different SCCs impairments in patients with unilateral vestibular diseases.

The effects of continuous administration of diazepam on the recovery of lesion-induced nystagmus in unilaterally labyrinthectomised rats

BACKGROUND

Diazepam, a gamma-aminobutyric acid type A receptor agonist, is classified as a vestibular suppressant and is effective in treating acute vertigo. However, its effects on vestibular compensation (VC) remain unclear.

OBJECTIVES

We examined the effects of continuous administration of diazepam on the frequency of spontaneous nystagmus (SN) after unilateral labyrinthectomy (UL) as an index of the initial process of VC in rats.

MATERIALS AND METHODS

Diazepam was continuously administered at doses of 3.5 and 7.0 mg/kg/day, intraperitoneally, via an osmotic minipump. The frequency of SN beating against the lesion side after UL was measured. Potassium chloride (KCl) solution (1 M) was injected intratympanically to induce SN beating to the injection side.

RESULTS

Continuous administration of diazepam significantly and dose-dependently decreased the frequency of SN after UL, and also reduced the x intercept of the nonlinear regression curve of the decline in UL-induced SN with time in rats. However, the continuous administration of diazepam did not affect the frequency of intratympanic KCl-induced SN in the rats.

CONCLUSION

These findings suggested that continuous administration of diazepam accelerates the initial process of VC; however, it does not suppress the nystagmus-driving mechanisms in rats.

[Further exploration of the classification and clinical value of head-shaking nystagmus]

Objective:To investigate the classification of head shaking nystagmus（HSN） and its clinical value in vestibular peripheral diseases. Methods:Clinical data of 198 patients with peripheral vestibular disorders presenting with HSN were retrospectively analyzed. Video Nystagmograph（VNG） was applied to detect spontaneous nystagmus（SN）, HSN, and Caloric Test（CT）. The intensity and direction of SN and HSN as well as the unilateral weakness（UW） and direction preponderance（DP） values in caloric test was analyzed in patients. Results:Among the 198 patients with vestibular peripheral disease, there were 105 males and 93 females, with an average age of（49.1±14.4） years （range: 14-87 years）. One hundred and thirty seven patients were diagnosed as Vestibular Neuritis（VN）, 12 as Meniere's Disease（MD）, 41 as sudden deafness（SD） and 8 as Hunt's syndrome accompanied by vertigo. Among them, there were 116 patients in the acute phase, including 68 cases（58.6%） with decreased HSN, 4 cases（3.4%） with increased HSN, 5 cases（4.3%） with biphasic HSN, 38 cases（32.8%） with unchanged HSN, and 1 case（0.9%） with perverted HSN. There were 82 cases in the non-acute phase, 51 cases（62.2%） with decreased HSN, 3 cases（3.6%） with increased HSN, 9 cases（11.0%） with biphasic HSN, and 19 cases（23.2%） with unchanged HSN. In biphasic HSN, the intensity of phase I nystagmus was usually greater than that of phase II, and the difference was statistically significant（P<0.01）. There was no correlation between HSN type and course of disease or DP value. The intensity of HSN was negatively correlated with the course of disease（r=-0.320, P<0.001） and positively correlated with DP value（r=0.364, P<0.001）, respectively. The intensity of unchanged nystagmus and spontaneous nystagmus were（8.0±5.7） °/s and（8.5±6.4）°/s, respectively. There was no statistically significant difference in the intensity of nystagmus before and after shaking the head. Conclusion:HSN can be classified into five types and could be regarded as a potential SN within a specific frequency range （mid-frequency）. Similarly, SN could also be considered as a common sign of unilateral vestibular impairment at different frequencies. HSN intensity can reflect the dynamic process of vestibular compensation, and is valuable for assessing the frequency of damage in peripheral vestibular diseases and monitoring the progress of vestibular rehabilitation.

Vestibular rehabilitation improves spontaneous nystagmus normalization in patients with acute unilateral vestibulopathy

Introduction

Spontaneous nystagmus (SN) can be observed after acute unilateral vestibulopathy (AUVP). The slow phase eye velocity of the SN progressively decreases in darkness as the result of rebalanced neurophysiological activity between both vestibular nuclei, a process that can take several months. Although this compensatory process can occur spontaneously, there is poor evidence that vestibular rehabilitation (VR) can facilitate the process.

Methods

We documented the natural time course of SN reduction in patients with AUVP, as well as the effects of VR by means of a unilateral rotation paradigm. In a retrospective study (Study 1: n = 126 AUVP patients), we compared the time course of the SN reduction in patients with VR (n = 33) and without VR (n = 93). In a prospective study (Study 2: n = 42 AUVP patients), we compared the effects of early VR (n = 22; initiated within the first two weeks of symptoms onset) or late VR (n = 20; initiated after the second week of symptoms onset) on the time course of the SN reduction.

Results

Study 1 showed shorter median time of SN normalization in patients with VR compared to patients without VR (14 days and 90 days, respectively). Study 2 showed that AUVP patients with early and late VR had a similar median time of SN normalization. The SN slow phase eye velocity was significantly decreased as early as the end of the first VR session in both groups, and kept decreasing at each subsequent VR session. In the early VR group, 38% of the patients had slow phase eye velocity below 2°/s after the first VR session, 100% after the fifth session. Similar findings were observed in the late VR group.

Discussion

Taken together, these results indicate that VR with a unidirectional rotation paradigm speeds up the normalization of SN. This effect seems independent of the time between symptoms onset and commencement of VR, but early intervention is recommended to speed up the SN reduction.

Spontaneous Nystagmus in Patients With Posterior Semicircular Canal Benign Paroxysmal Positional Vertigo

OBJECTIVE

This study aimed to investigate the incidence of spontaneous nystagmus (SN) in posterior semicircular canal (PSCC) benign paroxysmal positional vertigo (BPPV) and its effect on treatment outcomes.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

METHODS

This study included 50 patients with idiopathic unilateral PSCC BPPV between July 2021 and May 2022. The presence of SN was investigated, and the results of the bithermal caloric test and video head impulse test (vHIT) were compared.

RESULTS

SN was observed in 13 (26%) of the 50 patients presenting PSCC BPPV. The direction of SN was mainly unidirectional and horizontal in 12 of the 13 patients with a slow-phase velocity ranging from 2 to 4°/s. One patient presented an upbeating torsional SN at the initial evaluation. The mean vHIT gain of the PSCC on the affected side was significantly lower in patients with SN than those without SN (p = .004, Mann-Whitney U test). The proportion of patients who recovered within 2 sessions of the repositioning maneuver was significantly higher in those without SN than that in those with SN (p < .001, Fisher's exact test).

CONCLUSION

This study demonstrated that the treatment outcomes of PSCC BPPV were significantly worse in patients with SN than those without SN. Examining the presence of SN in patients with PSCC BPPV may be helpful in counseling the patients on prognosis, and it is expected that more sessions of canalith repositioning maneuver may be required to treat PSCC BPPV in patients with SN than those without SN.

The role of vestibular cold caloric tests in the presence of spontaneous nystagmus

Objective

The bithermal caloric test is commonly used to detect a canal paresis. However, in case of spontaneous nystagmus, this procedure can provide results of non-univocal interpretation. On the other hand, confirming the presence of a unilateral vestibular deficit can help to differentiate between central and a peripheral vestibular involvement.

Methods

We studied 78 patients suffering from acute vertigo and showing spontaneous horizontal unidirectional nystagmus. All patients were submitted to bithermal caloric tests, and the results were compared with those obtained using a monothermal (cold) caloric test.

Results

We demonstrate the congruence between the bithermal and monothermal (cold) caloric test through mathematical analysis of the results of both tests in patients with acute vertigo and spontaneous nystagmus.

Conclusions

We propose to perform the caloric test in the presence of a spontaneous nystagmus using a monothermal cold assuming that the prevalence of the response to the cold irrigation on the side towards which the nystagmus beats is a sign of the presence of pathological unilateral weakness and therefore more likely peripheral in its origin.

Vestibular assessment in sudden sensorineural hearing loss: Role in the prediction of hearing outcome and in the early detection of vascular and hydropic pathomechanisms

Introduction

Predicting hearing outcome in sudden sensorineural hearing loss (SSNHL) is challenging, as well as detecting the underlying pathomechanisms. SSNHL could be associated with vestibular damage since cochleo-vestibular structures share the same vascularization, along with being in close anatomical proximity. Whereas viral inflammations and autoimmune/vascular disorders most likely represent the involved aetiologies, early-stage Menière's disease (MD) can also present with SSNHL. Since an early treatment could beneficially influence hearing outcome, understanding the possible etiology plays a pivotal role in orienting the most appropriate treatment. We aimed to evaluate the extent of vestibular damage in patients presenting with SSNHL with or without vertigo, investigate the prognostic role of vestibular dysfunctions on hearing recovery and detect specific lesion patterns related to the underlying pathomechanisms.

Methods

We prospectively evaluated 86 patients with SSNHL. Audio-vestibular investigation included pure-tone/speech/impedance audiometry, cervical/ocular-VEMPs, vHIT and video-Frenzel examination. White matter lesions (WML) were evaluated on brain-MRI. Patients were followed-up and divided into "SSNHL-no-vertigo," "SSNHL+vertigo" and "MD" subgroups.

Results

Hearing was more impaired in "SSNHL+vertigo" patients who exhibited either down-sloping or flat-type audiograms, and was less impaired in "MD" where low frequencies were mostly impaired (p < 0.001). Otolith receptors were more frequently involved than semicircular canals (SCs). Although the "SSNHL-no-vertigo" subgroup exhibited the lowest vestibular impairment (p < 0.001), 52% of patients developed otolith dysfunctions and 72% developed nystagmus. Only "MD" subjects showed anterior SC impairment and upbeating spontaneous/positional nystagmus. They more frequently exhibited cervical-VEMPs frequency tuning (p = 0.036) and ipsilesional spontaneous nystagmus (p < 0.001). "SSNHL+vertigo" subjects presented with more frequently impaired cervical-VEMPs and posterior SC and with higher number of impaired receptors (p < 0.001). They mainly exhibited contralesional spontaneous and vibration-induced nystagmus (p < 0.05) and only they showed the highest WML score and "vascular" lesion patterns (p < 0.001). Concerning the outcomes, hearing was better in "MD" and worse in "SSNHL+vertigo" (p < 0.001). Hearing recovery was mostly affected by cervical-VEMPs impairment and the number of involved receptors (p < 0.05). Patients with "vascular" lesion patterns presented with the highest HL degree and WML score (p ≤ 0.001), while none of them exhibited a complete hearing recovery (p = 0.026).

Conclusions

Our data suggest that vestibular evaluation in SSNHL can provide useful information on hearing recovery and underlying aetiologies.

Subjective Evaluation of Balance by the Dizziness Handicap Inventory Does Not Predict Fall Risk in Older Adults Visiting Otolaryngology Clinics

OBJECTIVES

Subjective symptoms of dizziness in older adults are affected not only by objective data such as postural balance, but also by complex psychological factors. Published data analyzing how simultaneous evaluations of both objective and subjective assessments of balance can predict fall risk remain lacking. This study examined how fall risk can be predicted based on both objective data for balance and hearing and subjective symptoms of dizziness among older adults visiting otolaryngology clinics.

METHODS

Medical charts of 76 patients ≥65 years old with dizziness/vertigo who visited the otolaryngology clinic were reviewed. Objective data were evaluated by postural balance (posturographic data with eyes open and closed, and one-leg standing test), spontaneous nystagmus, and mean hearing levels. Subjective handicap associated with dizziness/vertigo was assessed using the Dizziness Handicap Inventory (DHI). Subjective mental status of anxiety and depression were assessed using the Hospital Anxiety and Depression Scale (HADS). Information on history (cardiovascular diseases) and fall accidents within the preceding year was collected using an in-house interview sheet.

RESULTS

Objective data on postural balance did not correlate with subjective symptoms on DHI or HADS (P > .05, Pearson's correlation coefficient). Adjusted logistic regression modeling with the outcome of incident falls revealed that poor postural balance significantly predicted fall risk (P < .05; 4.9 [1.4-16.8] per 10-cm² increment). Nystagmus tended to be associated with fall risk. In contrast, DHI score did not predict fall risk (P = .43; 1.0 [0.9-1.03]). Receiver operating characteristic analysis proposed a cut-off for postural sway with eyes closed >6.1 cm² as optimal to predict falls in patients with nystagmus (AUC, 0.74; 95% confidence interval, 0.48-0.997).

CONCLUSION

Poor postural balance is associated with increased fall risk after adjusting for subjective symptoms in older adults at otolaryngology clinics. Conversely, the self-perceived dizziness handicap of DHI score is an insufficient tool to evaluate their fall risk.

A new immunohistochemical method to evaluate the development of vestibular compensation after unilateral labyrinthectomy in rats

BACKGROUND

Unilateral labyrinthectomy (UL) causes the disappearance of ipsilateral medial vestibular nuclear (ipsi-MVe) activity and induces spontaneous nystagmus (SN), which disappears during the initial process of vestibular compensation (VC). Ipsi-MVe-activity restores in the late process of VC.

OBJECTIVE

We evaluated the late process of VC after UL in rats and examined the effects of thioperamide (H3 antagonist) on VC.

MATERIALS AND METHODS

MK801 (NMDA antagonist)-induced Fos-like immunoreactive (-LIR) neurons in contra-MVe, which had been suppressed by NMDA-mediated cerebellar inhibition in UL rats was used as an index.

RESULTS

The number of MK801-induced Fos-LIR neurons in contra-MVe gradually decreased to the same level as that of sham-operated rats 14 days after UL. Thioperamide moved the disappearance of the MK801-induced Fos-LIR neurons 2 days earlier. The number of MK801-induced Fos-LIR neurons in thioperamide-treated rats was significantly decreased, compared with that of vehicle rats on days 7 and 12 after UL. But, thioperamide did not influence the decline of SN frequency in UL rats.

CONCLUSION

These findings suggested that the number of MK801-induced Fos-LIR neurons in contra-MVe was decreased in concordance with the restoration of ipsi-MVe-activity during the late process of VC after UL and that thioperamide accelerated the late, but not the initial process of VC.

Peripheral Vestibulopathy Presenting as Acute Vertigo and Spontaneous Nystagmus with Negative Video Head Impulse Test

OBJECTIVE

To analyze acute vertigo showing spontaneous nystagmus with negative video head impulse test (vHIT).

STUDY DESIGN

Retrospective chart analysis.

SETTING

Tertiary referral hospital.

SUBJECTS AND METHODS

Over 16 months, 155 patients were identified with acute vertigo with spontaneous nystagmus. Of these 155, 30 (19.4%) were enrolled in this study because they did not show gain loss or catch-up saccades in both sides of the horizontal vHIT. Results of vestibular function tests (videonystagmography, horizontal vHIT, caloric test, and cervical vestibular-evoked myogenic potential [cVEMP]) and pure tone audiometry were analyzed. For all cases, magnetic resonance imaging with diffusion-weighted imaging was checked.

RESULTS

Patients consisted of 17 with Ménière's disease and 7 with sudden sensorineural hearing loss with vertigo (SSNHL_V), and only 3 patients were finally diagnosed as having acute vascular stroke. Except for the loss of hearing on the lesion side, the direction of nystagmus or cVEMP asymmetry showed very different results. All 7 patients with SSNHL_V did not have canal paresis in the caloric test, but cVEMP amplitude was smaller on the lesion side for 6 patients.

CONCLUSIONS

For patients with acute vertigo presenting spontaneous nystagmus with negative horizontal vHIT, it is important not only to focus on the diagnosis of acute vascular stroke but also to evaluate hearing because of the high possibility of Ménière's disease or SSNHL_V.

Clinical value of 4-hour delayed gadolinium-Enhanced 3D FLAIR MR Images in Acute Vestibular Neuritis

OBJECTIVE

To investigate the clinical significance of 4-hour delayed-enhanced 3.0 Tesla three-dimensional (3D) fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging in acute vestibular neuritis.

STUDY DESIGN

A prospective observational study.

METHODS

Twenty-nine vestibular neuritis patients were enrolled between January 2017 and June 2017. Vestibular function tests, comprising the caloric and video head impulse tests and vestibular-evoked myogenic potential measurements, were performed. Precontrast, 10-minute, and 4-hour delayed-enhanced 3D-FLAIR MR images using double-dose IV gadolinium were obtained. After laterality and extent of inner ear enhancement were defined, the patients were divided into groups based on the patterns of enhancement, and clinical parameters were analyzed according to the groups.

RESULTS

Twenty patients (20 of 29, 69.0%) had obviously asymmetric enhancement of the affected inner ear structures on 4-hour delayed images, whereas only three patients (10.3%) had marked enhancement on 10-minute delayed images. The duration of spontaneous nystagmus (DurSN) was significantly longer in the patients with enhancement, especially with enhancement of the whole inner ear, including the vestibule and semicircular canals (P < 0.033). Spontaneous nystagmus resolved within 12 days in patients without laterality of enhancement, and within 16 days in ipsilesional enhancement confined to the inner auditory canal and fundus. Other results of vestibular function tests did not reveal any significant associations with MR enhancement.

CONCLUSIONS

Contrast enhancement of the vestibular nerve and inner ear structures can be identified on 4-hour delayed-enhanced 3T 3D-FLAIR MR images in acute vestibular neuritis. The extent of inner ear enhancement may be associated with the DurSN.

LEVEL OF EVIDENCE

4. Laryngoscope, 1946-1951, 2018.

[The analysis of the value of spontaneous nystagmus in peripheral vestibular hypofunction]

Objective:To study the characteristics and clinical value of spontaneous nystagmus in patients with peripheral vestibular dysfunction.Method:Sixty cases with acute unilateral peripheral vestibular dysfunction were studied.All were diagnozed as vestibular neuritis(VN) . The relationship between SN and disease duration,DP and UW were analyzed.Result:SN was present in49 patients(81.7%)and absent in the remaining 11(18.3%).The intensity of SN ranged from 0.5°/s-20.4°/s and had negative correlation with the disease duration(r=-0.478，P<0.01). The patients were divided into 3 groups (mild,medium and severe) according to SN intensity,with median duration of disease being 6.5 d，5 d and 3 d respectively. The difference between groups was statistically significant(χ²=9.071，P<0.01).The result of the caloric test were as following：caloric test revealed DP in 44 cases（89.8%） of SN ;DP values were normal in 8 cases（10.2%）;SN intensity was positively correlated with DP value（r=0.513,P<0.01） ;unilateral weakness was found in 35 cases（71.4%）,with the direction of SN towards the weakness side in 4 cases and towards the opposite direction in the remaining 31 cases; 7 cases（14.3%）had bilateral weakness and 7 cases（14.3%）normal. There were no relationship between the intensity of SN and UW value（r=-0.321,P>0.05）.The UW value of patients with SN (40.9±26.3）% was compared to the group without SN（29.9±18.2）% . The difference was statistically significant (F=4.497,P<0.05).Conclusion:The intensity of SN in patients with acute unilateral peripheral vestibular dysfunction was often moderate and severe. The intensity of SN waned as the disease progressed or the direction reversed,The vestibular injury in patient with SN was more severe than those without. SN is useful in clinical assessment of vestibular injury and compensatory status.

Acute unilateral loss of vestibular function

Sudden unilateral loss of vestibular function is the most severe condition that can occur in the vestibular system. The clinical syndrome is caused by the physiologic properties of the vestibulo-ocular reflex (VOR) arc. In the normal situation, the two peripheral vestibular end organs are connected to a functional unit in coplanar pairs of semicircular canals working in a push-pull mode. "Push-pull" mode means that, when one side is excited, the other side is inhibited, and vice versa due to two mechanisms. First, first-order vestibular afferents are bipolar cells. They have a tonic firing rate that is modulated up or down depending on the direction of rotation. Second, via inhibitory neural connections of second-order vestibular neurons between the vestibular nuclei (vestibular commissural system), the excited side inhibits further the contralateral side. The neural signals are encoded as the difference of the change in firing rate of the vestibular neurons modulating the tonic firing rate on both sides in opposite directions (one side up, the contralateral side down). When the head is not moving, the two peripheral vestibular end organs generate a resting firing rate, which is exactly equal on both sides. When the head is rotated, for example, to the right, the right-sided first-order vestibular afferents increase their discharge rate and the left-sided ones decrease their firing rate. This leads to increase in firing rate of also the type I second-order vestibular neurons in the vestibular nuclei, which synapse with inhibitory type II neurons on the contralateral side, further decreasing the firing rate in the second-order vestibular neurons in the contralateral vestibular nucleus. When the direction of head rotation is reversed, the behavior of the type I neurons on the two sides of the head is reversed. The same relation exists between the coplanar vertical canal afferents on the two sides of the head. When there is unilateral damage to the end organ or the vestibular nerve, the resting firing frequency is drastically reduced or even silenced on the lesioned side, thereby creating a tonic imbalance between the normal resting firing on the healthy side and the lesioned side. This tonic imbalance mimics a permanent rotation toward the healthy side (the side with the higher firing rate), resulting, via the VOR, in a slow-phase drift of the eyes toward the side of the lesion, interrupted by rapid quick-phase resetting eye movements toward the healthy side. This leads to the typical vestibular spontaneous horizontal-torsional nystagmus together with rotational vertigo and postural imbalance, with the tendency to fall toward the lesioned side. The tonic imbalance with the hallmark of spontaneous nystagmus usually recovers within days to weeks after the lesion due to the central restoration of tonic activity on the lesioned side. The dynamic changes, however, might be long-lasting when the peripheral sensors do not recover their function. This causes asymmetric VOR responses, with weaker responses when the head is rotated rapidly toward the lesioned side, leading to transient oscillopsia.

Lateral canal BPPV with Pseudo-Spontaneous Nystagmus masquerading as vestibular neuritis in acute vertigo: a series of 273 cases

OBJECTIVE

To investigate the incidence of Lateral Semicircular Canal BPPV (LSC BPPV) with Pseudo-Spontaneous Nystagmus in patients preliminarily diagnosed for vestibular neuritis in the Emergency Department (ED).

METHODS

Retrospective study of 273 patients with acute vertigo and persistent horizontal nystagmus in upright position (male 110, female 163, 14-93 years old) observed over four years. All the patients were checked for any nystagmus modification by performing the Head Pitch Test (HPT) in the upright position.

RESULTS

The HPT modified the beating direction of the persistent horizontal nystagmus in 56 of the 273 examined patients. The positioning tests subsequently confirmed the diagnosis of LSC BPPV in all those 56 patients. There were 37 geotropic variants and 19 apogeotropic variants and all of them were successfully treated by performing liberatory manoeuvres in the course of the same session.

CONCLUSION

Performing the HPT in the upright position helps to differentiate a direction fixed nystagmus from a direction changing one, and in so doing, to make the differential diagnosis between vestibular neuritis and LSC BPPV, achieving the goal of successfully treating LSC BPPV in the first session.