Central paroxysmal positional nystagmus: Characteristics and possible mechanisms

[Positional vertigo variant]

The article describes case history and multiphase treatment of the patient with attacks of vertigo, initially regarded as the onset of Meniere's disease, but later qualified as secondary positional attacks with combined musculoskeletal pathology of the craniovertebral region and temporomandibular joint. Medicinal, local and surgical treatment led to the perfect result. Thus, the team work of neurologist, otolaryngologist, maxillofacial surgeon and orthodontist led to the successful elimination of vertigo attacks.

Central positional nystagmus in inferior cerebellar peduncle lesions: a case series

We aimed to characterize the central positional nystagmus (CPN) observed in lesions involving the inferior cerebellar peduncle (ICP). We analyzed the clinical and neurotologic findings in six patients with an isolated unilateral ICP infarction that had been diagnosed at a university hospital in South Korea from 2003 to 2019. Patients usually presented with acute vestibular syndrome in isolation (4/6, 67%). Ipsilesional spontaneous nystagmus was observed in five while supine (5/6, 83%). Four (4/6, 67%) patients showed CPN which included apogeotropic (n = 3) or geotropic (n = 1) during head turning to either side while supine, and vertical nystagmus during straight-head hanging, Dix-Hallpike maneuvers, or up-righting (n = 3). Four patients showed contraversive ocular tilt reaction or tilt of the subjective visual vertical. Bedside and video head-impulse tests were normal in all patients. CPN is a usual finding in ICP lesions, and may be ascribed to damage of the fibers running from the nodulus/uvula onto the vestibular nucleus via the ICP.

Vertigo and dizziness in the emergency room

PURPOSE OF REVIEW

To provide an update on diagnostic algorithms for differential diagnosis of acute vertigo and dizziness and swift identification of potentially harmful causes.

RECENT FINDINGS

About 25% of patients with acute vertigo and dizziness have a potentially life-threatening diagnosis, including stroke in 4-15%. Diagnostic work-up relies on the combination of symptom features (triggers, duration, history of vertigo/dizziness, accompanying symptoms) and a comprehensive vestibular, ocular motor, and balance exam. The latter includes head impulse, head-shaking nystagmus, positional nystagmus, gaze-holding, smooth pursuit, skew deviation, and Romberg's test. Recent standardized diagnostic algorithms (e.g., HINTS, TriAGe+) suggest the combination of several elements to achieve a good diagnostic accuracy in differentiation of central and peripheral vestibular causes. Neuroimaging with MRI must be applied and interpreted with caution, as small strokes are frequently overlooked, especially in the acute setting (false-negative rate of up to 50%).

SUMMARY

Diagnostic differentiation of acute vertigo and dizziness remains a complex task, which can be tackled by a structured clinical assessment focusing on symptom characteristics and constellations of ocular motor and vestibular findings. Specific challenges arise in cases of transient or atypical vestibular syndromes.

Update on benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo worldwide. This review considers recent advances in the diagnosis and management of BPPV including the use of web-based technology and artificial intelligence as well as the evidence supporting the use of vitamin D supplements for patients with BPPV and subnormal serum vitamin D.

Positioning Velocity Matters in Central Paroxysmal Positional Vertigo: Implication for the Mechanism

Objectives: To elucidate the mechanism of paroxysmal central positional nystagmus (CPN) by determining the effects of head rotation velocity on the intensity of paroxysmal downbeat nystagmus induced during straight head hanging (SHH).

Methods: We recruited 21 patients with paroxysmal downbeat CPN induced during SHH at the Dizziness Center of Seoul National University Bundang Hospital from September 2018 to July 2019. Twenty-one patients had manual SHH at two different lying velocities, the fast (routine) and slow, and they also underwent SHH at different rotation velocities of 10, 20, 30, and 40 °/s using a motorized rotation chair. Induced nystagmus was recorded using video-oculography and the maximum slow phase velocity (SPV) and time constant (TC) of the induced paroxysmal nystagmus were analyzed.

Results: During manual SHH, paroxysmal downbeat nystagmus was invariably induced during routine SHH (fast lying down), but absent or minimal during slow positioning. During motorized SHH, the median of maximum intensity of downbeat nystagmus increased from 7.6 °/s (0–16.9) to 14.0 °/s (0–32.5), 16.5 °/s (0–44.6), and 19.1 °/s (0–55.2) as the rotation velocity increased from 10 to 20, 30, and 40°/s (P < 0.001, P < 0.001, P = 0.004; linear mixed models). In contrast, the TCs of paroxysmal downbeat CPN remained unchanged (P = 0.558, P = 0.881, P = 0.384, linear mixed models).

Conclusions: The dependence of nystagmus intensity on head rotation velocity supports a disinhibited and exaggerated inhibitory rebound of the canal signals as the mechanism of paroxysmal CPN.

Feasibility of Using the Video-Head Impulse Test to Detect the Involved Canal in Benign Paroxysmal Positional Vertigo Presenting With Positional Downbeat Nystagmus

Positional downbeat nystagmus (pDBN) represents a relatively frequent finding. Its possible peripheral origin has been widely ascertained. Nevertheless, distinguishing features of peripheral positional nystagmus, including latency, paroxysm and torsional components, may be missing, resulting in challenging differential diagnosis with central pDBN. Moreover, in case of benign paroxysmal positional vertigo (BPPV), detection of the affected canal may be challenging as involvement of the non-ampullary arm of posterior semicircular canal (PSC) results in the same oculomotor responses generated by contralateral anterior canal (ASC)-canalolithiasis. Recent acquisitions suggest that patients with persistent pDBN due to vertical canal-BPPV may exhibit impaired vestibulo-ocular reflex (VOR) for the involved canal on video-head impulse test (vHIT). Since canal hypofunction normalizes following proper canalith repositioning procedures (CRP), an incomplete canalith jam acting as a "low-pass filter" for the affected ampullary receptor has been hypothesized. This study aims to determine the sensitivity of vHIT in detecting canal involvement in patients presenting with pDBN due to vertical canal-BPPV. We retrospectively reviewed the clinical records of 59 consecutive subjects presenting with peripheral pDBN. All patients were tested with video-Frenzel examination and vHIT at presentation and after resolution of symptoms or transformation in typical BPPV-variant. BPPV involving non-ampullary tract of PSC was diagnosed in 78%, ASC-BPPV in 11.9% whereas in 6 cases the involved canal remained unidentified. Presenting VOR-gain values for the affected canal were greatly impaired in cases with persistent pDBN compared to subjects with paroxysmal/transitory nystagmus (p < 0.001). Each patient received CRP for BPPV involving the hypoactive canal or, in case of normal VOR-gain, the assumed affected canal. Each subject exhibiting VOR-gain reduction for the involved canal developed normalization of vHIT data after proper repositioning (p < 0.001), proving a close relationship with otoliths altering high-frequency cupular responses. According to our results, overall vHIT sensitivity in detecting the affected SC was 72.9%, increasing up to 88.6% when considering only cases with persistent pDBN where an incomplete canal plug is more likely to occur. vHIT should be routinely used in patients with pDBN as it may enable to localize otoconia within the labyrinth, providing further insights to the pathophysiology of peripheral pDBN.

Redox-Responsive Nanobiomaterials-Based Therapeutics for Neurodegenerative Diseases

Redox regulation has recently been proposed as a critical intracellular mechanism affecting cell survival, proliferation, and differentiation. Redox homeostasis has also been implicated in a variety of degenerative neurological disorders such as Parkinson's and Alzheimer's disease. In fact, it is hypothesized that markers of oxidative stress precede pathologic lesions in Alzheimer's disease and other neurodegenerative diseases. Several therapeutic approaches have been suggested so far to improve the endogenous defense against oxidative stress and its harmful effects. Among such approaches, the use of artificial antioxidant systems has gained increased popularity as an effective strategy. Nanoscale drug delivery systems loaded with enzymes, bioinspired catalytic nanoparticles and other nanomaterials have emerged as promising candidates. The development of degradable hydrogels scaffolds with antioxidant effects could also enable scientists to positively influence cell fate. This current review summarizes nanobiomaterial-based approaches for redox regulation and their potential applications as central nervous system neurodegenerative disease treatments.

Cerebellar infarction presenting with isolated positional vertigo: differentiating factors for benign paroxysmal positional vertigo

BACKGROUND

Isolated central positional vertigo (CPV) due to cerebellar infarction is often difficult to differentiate from benign paroxysmal positional vertigo (BPPV). Here, we aimed to evaluate whether vascular risk factors and serum vitamin D level can differentiate between positional vertigo types.

METHODS

A total of 78 consecutive patients were consecutively enrolled from January 2017. All CPV patients had a National Institutes of Health Stroke Scale score of 0 and cerebellar infarctions confirmed by brain MR imaging. Vascular risk factors and serum 25-hydroxyvitamin D levels were compared between the two groups of patients.

RESULTS

The proportion of men was higher in the CPV than in the BPPV group (p = 0.004). Atrial fibrillation was common in the CPV group on univariate analysis (p = 0.046). However, there were no independent differentiating factors between the two groups. The proportion of patients according to the number of risk factors was significantly different between the two groups (linear by linear association test, p = 0.02). The mean serum 25-hydroxyvitamin D level did not differ. Also, the proportions of vitamin D insufficiency and deficiency did not differ significantly between the two groups.

CONCLUSIONS

Increased number of vascular risk factors including male sex suggested more CPV than BPPV. However, the serum vitamin D level was below the normal range in both groups. Our results demonstrate that serum vitamin D level has little value in the differential diagnosis of positional vertigo. Efforts to identify differentiating factors are warranted, and accumulating evidences including our research may lead to a diagnostic algorithm for isolated positional vertigo.

Peripheral Downbeat Positional Nystagmus: Apogeotropic Posterior Canal or Anterior Canal BPPV

BACKGROUND AND PURPOSE

Downbeat nystagmus (DBN) during the Dix-Hallpike test (DHT) suggests excitation of the anterior canal (AC) or inhibition of the posterior canal (PC) underlying benign paroxysmal positional vertigo (BPPV). This case series describes 2 individuals presenting with DBN in positional testing suggestive of a PC BPPV variant termed apogeotropic PC-BPPV and due to inhibition of the PC.

CASE DESCRIPTIONS

Case 1 illustrates a DBN during positional testing (PC inhibition) that changes to an upbeating nystagmus (PC excitation) representing the otoconial material changing location and direction of movement within the PC. Case 2 describes a canal jam in the nonampullary segment of the PC.

DIFFERENTIAL DIAGNOSIS

Apogeotropic PC-BPPV can cause DBN due to inhibition of the vestibular afferent. Apogeotropic PC-BPPV may be due to a canal jam of debris within the nonampullary segment or cupulolithiasis with debris attached to the inferior-most aspect of the cupula within the PC. It can be difficult to differentiate AC-BPPV from the apogeotropic PC-BPPV variant. In both forms, the affected canal may be provoked in 1 or both positions of the DHT and straight head hanging position. However, in AC-BPPV there may only be a slight or absent torsional component toward the involved ear. In apogeotropic PC-BPPV, a strong torsion away from the involved ear is typically observed. The straight head hanging position may resolve AC-BPPV or convert apogeotropic PC-BPPV to typical PC-BPPV.

SUMMARY

These 2 cases illustrate atypical variants of BPPV that clinicians must consider in their interpretation of DBN during positional testing, particularly in the absence of other neurological signs.

Bilateral posterior semicircular canal dysfunction: a new finding with video head impulse test

Development of the video head impulse test (vHIT) assessing all three semicircular canals in both labyrinths has uncovered the existence of new vestibular failure patterns and made bilateral posterior canal dysfunction detection possible. We conducted a retrospective analysis of 41 patients with bilateral posterior semicircular canal failure and compared results to 37 controls, with normal posterior semicircular canal function. Mean calculated gain showed significant difference between patients and controls in right [0.54 (SD 0.016)] and left [0.57 (SD 0.014)] posterior semicircular canals. There was a peak in prevalence between 71 and 80 years. Presentation was chronic in 78% of patients, and gait instability was the most common complaint. Sixty eight percent of cases were classified as idiopathic. Significant difference between groups was seen regarding the presence of Meniere's disease, presbycusis, and positional down-beat nystagmus (posDBN). This new vHIT pattern is most often seen in elderly patients, mainly of idiopathic etiology and presents together with sensorineural hearing loss and posDBN. Our findings suggest idiopathic cases may well contribute to the so-called "presbyastasis".

Positional Testing in Acute Vestibular Syndrome: a Transversal and Longitudinal Study

OBJECTIVE

To evaluate the utility of positional testing in peripheral and central acute vestibular syndrome (pAVS, cAVS, respectively).

STUDY DESIGN

Prospective; observational.

SETTING

Tertiary referral center.

PATIENTS

Consecutive AVS patients.

INTERVENTIONS

Video-oculography in upright, supine and head hanging positions at presentation, 3-month and 1-year follow-up.

MAIN OUTCOME MEASURES

Positional modulation of spontaneous nystagmus; co-occurrence of central paroxysmal positional nystagmus (CPPN).

RESULTS

Fifteen pAVS [mean age (SD), 53.3 (16.6) (11 males)] and 15 cAVS [mean age (SD), 56.5 (17.8) (11 males)] patients were included (p=0.49). Acutely, in supine, in patients whose nystagmus was present in both head rotation sides, 12 of 13 (93%) pAVS and only 4 of 12 (33%) cAVS patients showed direction-fixed positional nystagmus which was stronger when turning the head to the slow phase side. The remaining cAVS patients showed either direction-fixed positional nystagmus which was stronger when turning the head to the fast phase side (5), or direction-changing positional geotropic nystagmus (2). One patient in each group showed direction-changing positional apogeotropic nystagmus. During follow-up, direction-changing positional apogeotropic and geotropic nystagmus became common in both groups. Acutely, in head hanging, 5 (33%) cAVS patients showed vertical CPPN and 2 showed positional saccadic intrusions. Positional downbeat nystagmus and saccadic intrusions became chronic.

CONCLUSIONS

The presence of acute direction-changing positional geotropic nystagmus, stronger direction-fixed positional nystagmus when turning the head to the fast phase side, and acute or chronic head hanging vertical CPPN should raise the suspicion for central AVS. Chronic geotropic and apogeotropic nystagmus following AVS constitute an underrecognized manifestation of vestibular compensation.

Perverted Downward Corrective Saccades During Horizontal Head Impulses in Chiari Malformation

The mechanism of perverted vertical responses during horizontal head impulse tests (HITs) requires further elucidation. A 47-year-old woman with a Chiari malformation showed alternating skew deviation, downbeat nystagmus with an increasing slow phase velocity, impaired smooth pursuit, and upward ocular deviation during horizontal HITs and corrective downward saccades in the presence of normal bithermal caloric tests and intact tilt suppressions of the post-rotatory nystagmus. These findings suggest dysfunction of the inferior cerebellum including the tonsil, nodulus, and uvula. We propose that disruption of signals from the medial part of the vestibulocerebellum, which normally inhibits the lateral and anterior canal pathways, may elicit an upward misdirection of the eye velocity during rapid horizontal head rotation. Otherwise, the Chiari malformation may have directly affected the brainstem structures involved in the direction matrix of the vestibulo-ocular reflex.

Central mimics of benign paroxysmal positional vertigo: an illustrative case series

Benign paroxysmal positional vertigo (BPPV) is the most common peripheral vestibular disorder that is diagnosed based solely on clinical findings. Rarely, central lesions can present with positional vertigo and nystagmus, mimicking BPPV. Recognised red flags that may help distinguish central mimics from BPPV include the presence of additional neurological symptoms and signs, atypical nystagmus patterns, and the absence of a sustained response to repositioning manoeuvres. We present seven cases that illustrate how heuristic bias may affect the detection of these features in practice. Furthermore, our cases suggest that isolated downbeat positional nystagmus (simulating anterior canal BPPV) and apogeotropic horizontal nystagmus on the supine roll test (simulating horizontal canal BPPV) should be considered additional red flags.

Horizontal Direction-Changing Positional Nystagmus and Vertigo: A Case of Vestibular Migraine Masquerading as Horizontal Canal BPPV

Episodic positional vertigo is typically due to benign paroxysmal positional vertigo (BPPV) but may also be a manifestation of vestibular migraine. Distinguishing vestibular migraine from BPPV is essential since the treatment of each disorder is markedly different. The 31-month clinical course of a 41-year-old woman with vestibular migraine causing recurrent positional vertigo is described. During vestibular migraine attacks, she developed left-beating nystagmus in the upright position with removal of fixation, and geotropic horizontal nystagmus during the supine roll test. Interictally, her exam demonstrated positional apogeotropic horizontal nystagmus with the supine roll test, more intense in the supine head left position. Her vestibular migraine was successfully controlled with topiramate and eletriptan.

Classification of vestibular signs and examination techniques: Nystagmus and nystagmus-like movements

This paper presents a classification and definitions for types of nystagmus and other oscillatory eye movements relevant to evaluation of patients with vestibular and neurological disorders, formulated by the Classification Committee of the Bárány Society, to facilitate identification and communication for research and clinical care. Terminology surrounding the numerous attributes and influencing factors necessary to characterize nystagmus are outlined and defined. The classification first organizes the complex nomenclature of nystagmus around phenomenology, while also considering knowledge of anatomy, pathophysiology, and etiology. Nystagmus is distinguished from various other nystagmus-like movements including saccadic intrusions and oscillations.

View accompanying videos at http://www.jvr-web.org/ICVD.html

Characteristics and mechanism of apogeotropic central positional nystagmus

Here we characterize persistent apogeotropic type of central positional nystagmus, and compare it with the apogeotropic nystagmus of benign paroxysmal positional vertigo involving the lateral canal. Nystagmus was recorded in 27 patients with apogeotropic type of central positional nystagmus (22 with unilateral and five with diffuse cerebellar lesions) and 20 patients with apogeotropic nystagmus of benign paroxysmal positional vertigo. They were tested while sitting, while supine with the head straight back, and in the right and left ear-down positions. The intensity of spontaneous nystagmus was similar while sitting and supine in apogeotropic type of central positional nystagmus, but greater when supine in apogeotropic nystagmus of benign paroxysmal positional vertigo. In central positional nystagmus, when due to a focal pathology, the lesions mostly overlapped in the vestibulocerebellum (nodulus, uvula, and tonsil). We suggest a mechanism for apogeotropic type of central positional nystagmus based on the location of lesions and a model that uses the velocity-storage mechanism. During both tilt and translation, the otolith organs can relay the same gravito-inertial acceleration signal. This inherent ambiguity can be resolved by a 'tilt-estimator circuit' in which information from the semicircular canals about head rotation is combined with otolith information about linear acceleration through the velocity-storage mechanism. An example of how this mechanism works in normal subjects is the sustained horizontal nystagmus that is produced when a normal subject is rotated at a constant speed around an axis that is tilted away from the true vertical (off-vertical axis rotation). We propose that when the tilt-estimator circuit malfunctions, for example, with lesions in the vestibulocerebellum, the estimate of the direction of gravity is erroneously biased away from true vertical. If the bias is toward the nose, when the head is turned to the side while supine, there will be sustained, unwanted, horizontal positional nystagmus (apogeotropic type of central positional nystagmus) because of an inappropriate feedback signal indicating that the head is rotating when it is not.

Central positional nystagmus: Characteristics and model-based explanations

The central vestibular system operates to precisely estimate the rotational velocity and gravity orientation using the inherently ambiguous information from peripheral vestibular system. Therefore, any lesions disrupting this function can generate positional nystagmus. Central positional nystagmus (CPN) can be classified into the paroxysmal (transient) and persistent forms. The paroxysmal CPN has the features suggesting a semicircular canal origin regarding the latency, duration, and direction of nystagmus. Patients with paroxysmal CPN commonly show several different types of nystagmus classified according to the provoking positioning. The persistent form of CPN mostly appears as downbeat nystagmus while prone or supine, or apogeotropic or geotropic horizontal nystagmus when the head is turned to either side while supine. CPN may be ascribed to erroneous neural processing within the velocity-storage circuit that functions in estimating angular head velocity, gravity direction, and inertia. Paroxysmal CPN appears to be post-rotatory rebound nystagmus due to lesions involving the cerebellar nodulus and uvula. In contrast, persistent CPN may arise from erroneous gravity estimation. The overlap of lesion location responsible for both paroxysmal and persistent CPN may account for the frequent coexistence of both forms of nystagmus in a single patient.

Benign positional vertigo, its diagnosis, treatment and mimics

The diagnosis of benign positional vertigo (BPV) relies on a history of episodic positional vertigo and a distinctive pattern of nystagmus during provocative positional testing. The direction of the induced nystagmus is specific to the affected canal and the velocity profile reflects the underlying mechanism of canalithiasis (free-floating otoconia within the canal duct) or cupulolithiasis (otoconia adherent to the cupula). We review current theories on the pathophysiology of BPV, the clinical history and examination underlying its diagnosis, and recommended repositioning manoeuvres for each of the BPV subtypes. Disorders other than BPV which may present with a similar history and/or positional nystagmus are discussed.

Vascular vertigo: updates

Discriminating strokes in patients with acute dizziness/vertigo is challenging especially when other symptoms and signs of central nervous involvements are not evident. Despite the developments in imaging technology over the decades, a significant proportion of acute strokes may escape detection on imaging especially during the acute phase or when the lesions are small. Thus, small strokes causing isolated dizziness/vertigo would have a higher chance of misdiagnosis in the emergency department. Even though several diagnostic algorithms have been advanced for acute vascular vertigo, we still await more comprehensive and sophisticated ones that can also be applied to transient vestibular symptoms due to vascular compromise. In this respect, vascular and perfusion imaging would be informative. Application of artificial intelligence and tele-consultation may be future perspectives for real-time decision in acute dizziness and vertigo. Several new constellations of ocular motor and vestibular findings have been added to the strokes involving the brainstem and cerebellum. Defining these characteristics would help understanding the function of central vestibular structures and allow more accurate localization of the strokes involving these structures.

Persistent geotropic positional nystagmus in unilateral cerebellar lesions

Objective

To determine the prevalence of central lesions in persistent geotropic positional nystagmus, and characteristics and anatomical substrates of the nystagmus in cerebellar lesions.

Methods

We prospectively recruited 58 patients with persistent geotropic positional nystagmus at the Dizziness Clinic of Pusan National University Hospital. Seven patients with unilateral cerebellar lesions were subjected to analysis of clinical characteristics, oculographic data, and MRI lesions. For comparison, we studied 37 cases of peripheral persistent geotropic positional nystagmus.

Results

The prevalence of central lesions in persistent geotropic positional nystagmus was 12% (7/58). Persistent geotropic positional nystagmus in cerebellar lesions was mostly asymmetrical. Horizontal nystagmus changed in direction during the bow-and-lean test with null positions. All patients showed impaired horizontal smooth pursuit bilaterally, and 3 of them also had positional downbeat nystagmus. The peak intensity and asymmetry of persistent geotropic positional nystagmus did not differ between central and peripheral groups (p > 0.05), while there was a difference in the maxima. Lesion overlays revealed that damage to the cerebellar tonsil was responsible for the generation of persistent geotropic positional nystagmus.

Conclusion

Although persistent geotropic positional nystagmus in cerebellar lesions shares the characteristics of nystagmus measures with peripheral cases, accompanying central oculomotor signs can aid in differentiation. In tonsillar lesions, compensatory rotational feedback due to erroneous estimation of the direction of gravity may generate constant horizontal geotropic positional nystagmus.

Abnormal Oculomotor Functions in Amyotrophic Lateral Sclerosis

BACKGROUND AND PURPOSE

Although traditionally regarded as spared, a range of oculomotor dysfunction has been recognized in amyotrophic lateral sclerosis (ALS) patients. ALS is nowadays considered as a neurodegenerative disorder of a third compartment comprising widespread areas of extra-motor brain including cerebellum. Our objective was to perform an observational study to examine for ocular motor dysfunction in patients with ALS and for any differences between bulbar-onset and spinal-onset patients.

METHODS

Thirty two ALS patients (bulbar onset: 10, spinal onset: 22) underwent the standardized systemic evaluations using video-oculography.

RESULTS

Oculomotor dysfunctions such as square wave jerks, saccadic dysmetria, abnormal cogwheeling smooth pursuits and head shaking and positional nystagmus of central origin have been observed in the ALS patients at a relatively early stage. Abnormal smooth pursuits and saccadic dysmetria were increased in the bulbar-onset compared to the spinal-onset (p<0.05).

CONCLUSIONS

These oculomotor abnormalities may be a marker of neuro-degeneration beyond motor neurons in ALS, especially in bulbar-onset disease. Future longitudinal studies of eye movement abnormalities have provided insights into the distribution and nature of the disease process.

Central vertigo

PURPOSE OF REVIEW

This review considers recent advances in central vertigo in terms of clinical and laboratory features and pathophysiology.

RECENT FINDINGS

Strokes presenting dizziness-vertigo are more likely to be associated with a misdiagnosis in the emergency setting. The risk of future strokes after discharge is higher in patients diagnosed with peripheral vertigo than in control patients. Strokes and transient ischemic attacks account for one-quarter of acute transient vestibular syndrome. Diagnosis of acute combined central and peripheral vestibulopathy such as anterior inferior cerebellar artery infarction requires additional consideration whenever applying the HINTS (head impulse test, direction-changing gaze-evoked nystagmus, and test of skew). Heat illness and metronidazole have been recognized as new causes of central vestibulopathy. Some new findings have also been added to the clinical and laboratory features of central vertigo.

SUMMARY

Central vertigo is a heterogeneous group of disorders with diverse clinical spectrums. An integrated approach based on understanding of clinical features, laboratory findings, speculated mechanisms, and limitations of current diagnostic tests will lead to better clinical practice.

Incidence and Clinical Significance of Positional Downbeat Nystagmus in Posterior Canal Benign Paroxysmal Positional Vertigo

Background and Purpose

The aim of this study was to determine the incidence and clinical significance of positional downbeat nystagmus (pDBN) after treatment of posterior canal (PC) benign paroxysmal positional vertigo (BPPV).

Methods

We recruited 77 patients with a diagnosis of PC BPPV, and assessed the presence of pDBN during follow-up positional tests after performing the Epley maneuver.

Results

An immediate response to the Epley maneuver was exhibited by 57 of the 77 patients, with resolution of their positional torsional upbeat nystagmus (pT-UBN). Twenty-two (39%) of them exhibited pDBN during follow-up tests performed 1 hour later. The latency and duration of pDBN were 3.2±2.0 and 12.0±10.0 s (mean±SD), respectively. The maximum slowphase velocity of pDBN was 5.1±2.5 degrees, and ranged from 2.0 to 12.2 degrees. A torsional component was also observed in six patients. The patients with pDBN were much more likely to develop a typical form of PC BPPV again at a 1-week follow-up (5/22, 23%) compared to those without pDBN (1/31, 3%; p=0.036). pDBN disappeared in all patients within 6 months.

Conclusions

Our study found transient pDBN in 40% of patients with PC BPPV after the immediate resolution of positional vertigo and pT-UBN. pDBN may be attributed to residual debris in the distal portion of the PC, which can move toward the ampulla producing an ampullopetal flow of endolymph during positioning.

Recurrent spontaneous vertigo with interictal headshaking nystagmus

Objective

To define a disorder characterized by recurrent spontaneous vertigo (RSV) of unknown etiology and interictal headshaking nystagmus (HSN).

Methods

We characterized HSN in 35 patients with RSV-HSN compared to that recorded in randomly selected patients with compensated vestibular neuritis (VN), vestibular migraine (VM), and Ménière disease (MD).

Results

The estimated time constant (TC) of the primary phase of HSN was 12 seconds (95% confidence interval [CI] 12–13) in patients with RSV-HSN, which was larger than those in patients with VN (5 seconds, 95% CI 4–5), VM (5 seconds, 95% CI 5–6), or MD (6 seconds, 95% CI 5–6). TCs of the horizontal vestibulo-ocular reflex were also larger during the rotatory chair test in patients with RSV-HSN. Among the 35 patients with RSV-HSN, 7 showed vigorous long-lasting HSN with a peak slow-phase velocity >50.0°/s. In 5 patients (5 of 7, 71%) with vigorous HSN, HSN could have been induced even with headshaking for only 2 to 5 seconds. Long-term prognosis was favorable, with a resolution or improvement of the symptoms in more than half of the patients during the median follow-up of 12 (range 2–58) years from symptom onset. None developed VM, MD, or cerebellar dysfunction during the follow-up.

Conclusion

The clinical features and characteristics of HSN in our patients indicate a hyperactive and asymmetric velocity-storage mechanism that gives rise to intermittent attacks of spontaneous vertigo probably when marginal compensation of underlying pathology is disrupted by endogenous or exogenous factors.

Acute Unilateral Audiovestibulopathy due to Embolic Labyrinthine Infarction

Introduction

Labyrinthine infarction is a cause of acute audiovestibulopathy, but can be diagnosed only in association with other infarctions involving the brainstem or cerebellar areas supplied by the anterior inferior cerebellar artery (AICA) since current imaging techniques cannot visualize an infarction confined to the labyrinth. This case series aimed to establish embolic labyrinthine infarction as a mechanism of isolated acute audiovestibulopathy.

Methods

We analyzed clinical features, imaging findings, and mechanisms of embolism in 10 patients (8 men, age range: 38–76) who had developed acute audiovestibulopathy in association with an obvious source of embolism and concurrent acute embolic infarctions in the non-anterior inferior cerebellar artery territories. The presence of audiovestibulopathy was defined when bedside or laboratory evaluation documented unilateral vestibular (head-impulse tests or caloric tests) or auditory loss (audiometry).

Results

Six patients showed combined audiovestibulopathy while three had isolated vestibulopathy. One patient presented isolated hearing loss. Audiovestibular findings were the only abnormalities observed in nine patients. In all patients, MRIs documented single or multiple infarctions in the cerebellum (n = 5) or cerebral hemispheres (n = 5). Especially three patients showed single or scattered foci of tiny acute infarctions only in the cerebral hemispheres. Cardiac sources of embolism were found in eight, and artery-to-artery embolism was presumed in two patients.

Conclusion

Selective embolism to the labyrinth may be considered in patients with acute unilateral audiovestibulopathy and concurrent acute infarctions in the non-AICA territories.

Finger extension weakness and downbeat nystagmus motor neuron disease syndrome: A novel motor neuron disorder?

Introduction: Disturbances of eye movements are infrequently encountered in motor neuron diseases (MNDs) or motor neuropathies, and there is no known syndrome that combines progressive muscle weakness with downbeat nystagmus. Methods: To describe the core clinical features of a syndrome of MND associated with downbeat nystagmus, clinical features were collected from 6 patients. Results: All patients had slowly progressive muscle weakness and wasting in combination with downbeat nystagmus, which was clinically most obvious in downward and lateral gaze. Onset was in the second to fourth decade with finger extension weakness, progressing to other distal and sometimes more proximal muscles. Visual complaints were not always present. Electrodiagnostic testing showed signs of regional motor axonal loss in all patients. Discussion: The etiology of this syndrome remains elusive. Because finger extension weakness and downbeat nystagmus are the discriminating clinical features of this MND, we propose the name FEWDON‐MND syndrome. Muscle Nerve56: 1164–1168, 2017

Central Positional Nystagmus: A Systematic Literature Review

Objective

To provide a systematic review of the clinical and radiological features of lesion-induced central positional nystagmus (CPN) and identify salient characteristics that differentiate central from peripheral positional nystagmus (PN).

Methods

Systematic literature search according to the preferred reporting items for systematic reviews and meta-analysis.

Results

A total of 82 patients from 28 studies met the participants intervention, comparison, outcomes, and study designs criteria for inclusion. An atypical direction of nystagmus for the stimulated canal was reported in 97.5% patients during Dix–Hallpike (D–H) and 54.5% upon supine roll testing. Five types of CPNs were identified during positional testing: positional horizontal nystagmus (pHN) (36.8%), positional downbeating nystagmus (pDBN) (29.2%), positional torsional nystagmus (pTN) (2.1%), positional upbeating nystagmus (pUBN) (2.1%), and a combination of the four profiles (29.9%). CPN was paroxysmal (<60 s) in 85% patients on straight head hanging (SHH), 63.9% on D–H, and 37.5% on supine roll, and had a latency <3 s upon positioning in 94.7% patients in which it was reported. Concurrent vertigo was reportedly present in 63.4% patients and 48.8% demonstrated other neurological signs. Radiologically, in 74.4%, there was mention of cerebellar involvement, isolated brainstem involvement in 8.5%, and 14.6% involved the fourth ventricle.

Conclusion

Currently, there is a lack of robust data on the clinical and radiological characteristics of CPN highlighting the need for better phenotyping of CPN to help differentiate this entity from peripheral causes of PN. With increased awareness of CPN, particularly in the acute setting, we may see a change in the estimated prevalence of CPN and improved clinical markers to promptly identify the frequently sinister underlying causes.