Opsoclonus Following Downbeat Nystagmus in Absence of Visual Fixation in Multiple System Atrophy: Modulation and Mechanisms.

We report atypical opsoclonus in a patient with multiple system atrophy and propose a mechanism based on the patterns of modulation by visual, vestibular, and saccadic and vergence stimulation. Firstly, the 6-Hz opsoclonus mostly in the vertical plane occurred only after the development of downbeat nystagmus in darkness without visual fixation. Even after a substantial build-up, visual suppression of the opsoclonus was immediate and complete. Furthermore, the latency for re-emergence of opsoclonus in darkness was greater when the duration of preceding visual fixation was longer. Secondly, the effect of preceding downbeat nystagmus on the development of opsoclonus was evaluated by changing the head position. The opsoclonus did not occur in the supine position when the downbeat nystagmus was absent. After horizontal head shaking, the opsoclonus in the vertical plane gradually evolved into horizontal plane and resumed its vertical direction again after vertical head shaking. Thirdly, any opsoclonus was not triggered by imaginary saccades in the supine position. Lastly, combined vergence and saccadic eye movements during the Müller paradigm did not induce opsoclonus. From these findings of modulation, we suggest that the opsoclonus observed in our patient was invoked by vestibular signals. When the function of the omnipause neurons and saccadic system was impaired, the centrally mediated vestibular eye velocity signals may activate the saccadic system to generate opsoclonus. These atypical patterns of opsoclonus, distinct from the classic opsoclonus frequently observed in para-neoplastic or para-infectious disorders, may be an unrevealing sign of degenerative brainstem or cerebellar disorders.

Linear Vertigo in Benign Paroxysmal Positional Vertigo: Prevalence and Mechanism.

This study aimed to determine the prevalence and mechanism of linear vertigo reported by the patients during the attacks of benign paroxysmal positional vertigo (BPPV). We prospectively evaluated the characteristics (rotational vs. linear) of positional vertigo in 70 patients with posterior and horizontal canal BPPV using a questionnaire allowing multiple choices. In patients with linear vertigo, we further assessed the directionality of linear vertigo. We adopted the velocity-storage model to explain the occurrence and direction of linear vertigo in these patients with BPPV. Patients reported only rotational vertigo in 46 (46/70, 65.7%), only linear vertigo in 10 (14.3%), and both rotational and linear vertigo in 14 (20%). The patients experienced fear from rotational vertigo in 54 (54/70, 77.1%) and from linear vertigo in 20 (20/70, 28.6%). The direction of linear vertigo was concordant with the direction of inertial acceleration predicted by the velocity-storage model. Patients with BPPV may experience linear as well as rotational vertigo during the attacks. This linear vertigo may be ascribed to centrally estimated inertial acceleration.

Rotational vertebral artery occlusion: mechanisms and long-term outcome.

BACKGROUND AND PURPOSE: To elucidate the mechanisms and prognosis of rotational vertebral artery occlusion (RVAO). METHODS: We analyzed clinical and radiological characteristics, patterns of induced nystagmus, and outcome in 21 patients (13 men, aged 29-77 years) with RVAO documented by dynamic cerebral angiography during an 8-year period at 3 University Hospitals in Korea. The follow-up periods ranged from 5 to 91 months (median, 37.5 months). Most patients (n=19; 90.5%) received conservative treatments. RESULTS: All the patients developed vertigo accompanied by tinnitus (38%), fainting (24%), or blurred vision (19%). Only 12 (57.1%) patients showed the typical pattern of RVAO during dynamic cerebral angiography, a compression of the dominant vertebral artery at the C1-2 level during contralateral head rotation. The induced nystagmus was mostly downbeat with horizontal and torsional components beating toward the compressed vertebral artery side. None of the patients with conservative treatments developed posterior circulation stroke, and 4 of them (21.1%) showed resolution of symptoms during the follow-ups. CONCLUSIONS: RVAO has various patterns of vertebral artery compression, and favorable long-term outcome with conservative treatments. In most patients with RVAO, the symptoms may be ascribed to asymmetrical excitation of the bilateral labyrinth induced by transient ischemia or by disinhibition from inferior cerebellar hypoperfusion. Conservative management might be considered as the first-line treatment of RVAO.

Dissociated Results between Caloric and Video Head Impulse Tests in Dizziness: Prevalence, Pattern, Lesion Location, and Etiology.

BACKGROUND AND PURPOSE: This study was designed to determine the prevalence, pattern, lesion location, and etiology of dissociation in the results of the bithermal caloric test and the horizontal video head impulse test (vHIT) in dizzy patients with various etiologies and disease durations. METHODS: We analyzed the results of bithermal caloric tests and vHITs performed over 26 months in 893 consecutive patients who underwent both tests within a 10-day period. RESULTS: Dissociation in the results of the two tests was found in 162 (18.1%) patients. Among them, 123 (75.9%) had abnormal caloric tests (unilateral paresis in 118 and bilateral paresis in 5) but normal vHITs. Peripheral lesions were identified in 105 (85.4%) of these patients, with the main underlying diseases being Meniere's disease (62/105, 59%) and vestibular neuritis/labyrinthitis (29/105, 27.6%). In contrast, central pathologies of diverse etiologies were found only in 18 (14.6%) patients. Abnormal vHIT (bilaterally positive in 18, unilaterally positive in 19, and hyperactive in 2) and normal caloric responses were found in 39 patients, with an equal prevalence of central (n=19) and peripheral (n=20) lesions. The peripheral lesions included vestibular neuritis/labyrinthitis in seven patients and Meniere's disease in another seven. The central lesions had diverse etiologies. CONCLUSIONS: Dissociation in the results between caloric tests and horizontal vHITs is not uncommon. The present patients with abnormal caloric tests and normal vHITs mostly had peripheral lesions, while central lesions were likely to underlie those with abnormal vHITs and normal caloric tests.

Age-related deterioration of saccule-related neural function is associated with decreased estimated glomerular filtration rate and increased free thyroxine.

OBJECTIVE: This study attempted to identify systemic factors for age-related decline in neural function originating from the saccule using cervical vestibular-evoked myogenic potentials (cVEMP) parameters. METHODS: We recruited 129 symptomatic vertiginous patients who did not have known disorder affecting the cVEMP pathway (mean age = 52.4 ±â€¯13.9). The indicators of saccule-related neural function were the sum of normalized cVEMP amplitude (SNA) and the average of p13 latency on both sides (average latency, AL). Any associations between cVEMP and systemic factors were evaluated using a linear regression. RESULT: SNA decreased with ageing (p < 0.001) in univariable regression. The estimated glomerular filtration rate (eGFR) was positively associated with SNA (p = 0.002). Hematocrit, C-reactive protein, vitamin D, and free thyroxine (T4) showed a trend of association with SNA (p < 0.2). SNA was associated with ageing, increased free T4, and decreased eGFR in multivariable analysis. In the subgroup analysis, SNA was significantly associated with free T4 in younger patients (mean age = 41.5 ±â€¯9.91) but not in the older ones (mean age = 63.5 ±â€¯6.54). AL did not show any significant associations with systemic factors. CONCLUSION: Decreased eGFR and increased free T4 as well as aging may be risk factors for decline of saccule-related neural function. SIGNIFICANCE: Neural function originating from the saccule may be affected by systemic factors.

Predicting a successful treatment in posterior canal benign paroxysmal positional vertigo.

OBJECTIVE: To elucidate the characteristics and prognostic value of positioning nystagmus during the second position of the Epley maneuver (90 degrees contralateral head turn from the initial Hallpike maneuver). METHOD: The Epley maneuver was performed in 126 patients with confirmed posterior canal benign paroxysmal positional vertigo (PC-BPPV). The characteristics of positioning nystagmus were investigated using video Frenzel goggles. RESULTS: During the second position, 99 patients developed torsional upbeating nystagmus, which was in the same direction (orthotropic nystagmus) as during the first position (Hallpike maneuver), whereas 15 patients showed a reversed pattern. In 12 patents, nystagmus was not induced during the second position. All 99 patients with orthotropic nystagmus had resolution of BPPV after the first or second trial of the Epley maneuver. In contrast, 12 of the 15 patients with reversed nystagmus and 8 of the 12 patients without nystagmus failed to resolve. CONCLUSION: During the second position of the Epley maneuver, an orthotropic pattern of nystagmus predicts a successful repositioning, whereas reversed nystagmus or no nystagmus is suggestive of poor response to repositioning.

Nystagmus while recumbent in horizontal canal benign paroxysmal positional vertigo.

BACKGROUND: The identification of the affected ear is crucial for the successful treatment of benign paroxysmal positional vertigo involving the horizontal canal (HC-BPPV) by using particle-repositioning maneuvers. OBJECTIVE: To determine the lateralizing value of lying-down nystagmus in HC-BPPV. METHODS: The authors prospectively investigated lying-down nystagmus in 152 consecutive patients with confirmed HC-BPPV (99 geotropic and 53 apogeotropic types). Lying-down nystagmus was induced by placing patients in a supine position. For the geotropic type of HC-BPPV, the affected ear was identified by assuming that nystagmus is more intense when the head is rotated to the affected side while supine. The reverse assumption was adopted for the apogeotropic type. RESULTS: Lying-down nystagmus was observed in 58 patients (38.2%), 36 (36.4%) of the geotropic and 22 (41.5%) of the apogeotropic type. The direction of lying-down nystagmus was mostly away from the affected ear in the geotropic type, but toward the affected ear in the apogeotropic type. Of the 16 geotropic patients in whom the affected ear was not identified initially, 7 with lying-down nystagmus showed resolution of vertigo after particle-repositioning maneuvers when the involved ear was identified by observing lying-down nystagmus. CONCLUSION: Lying-down nystagmus is a valuable sign for determining which ear is affected in benign paroxysmal positional vertigo involving the horizontal canal, especially when patients show symmetric nystagmus on turning the head to either side.

Successful treatment of vasovagal syncope due to blood-injury phobia by physical maneuvering.

Blood-injury phobia may present as a vasovagal syncope in response to the sight of blood or after receiving venipuncture. A 26-year-old man presented with a history of syncope induced by venipuncture. A transcranial Doppler (TCD) scan with monitoring of both heart rate and blood pressure reproduced the syncope and showed it to be vasovagal in nature. Treatment by practicing physical maneuvers, such as leg crossing and muscle tensing, improved the condition of the patient. This case suggests that physical maneuvering is effective in the treatment of blood-injury phobia.