Search

Differentiation of spinocerebellar ataxia type 17 (SCA17) from Huntington's disease (HD) is often challenging since they share the clinical features of chorea, parkinsonism, and dystonia. The ocular motor findings remain to be elucidated in SCA17, and may help differentiating SCA17 from HD. We retrospectively compared the ocular motor findings of 11 patients with SCA17 with those of 10 patients with HD. In SCA17, abnormal ocular motor findings included impaired smooth pursuit (9/11, 82%), dysmetric saccades (9/11, 82%), central positional nystagmus (CPN, 7/11, 64%), abnormal head-impulse tests (4/11, 36%), and horizontal gaze-evoked nystagmus (GEN, 3/11, 27%). Among these, CPN was more frequently observed in SCA17 than in HD (7/11 (64%) vs. 0/10 (0%), p = 0.004) while saccadic slowing was more frequently observed in HD than in SCA17 (8/10 (80%) vs. 2/11 (18%), p = 0.009). Of six patients with follow-up evaluation, five later developed bilateral saccadic hypermetria (n = 4), GEN (n = 1), CPN (n = 1), bilaterally abnormal smooth pursuit (n = 1), and hyperactive head-impulse responses (n = 1) along with a clinical decline. Ocular motor abnormalities can be utilized as a diagnostic marker for differentiation of SCA17 from HD as well as a surrogate marker for clinical decline in SCA17. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aimed to define the clinical features and involved structures that aid in differentiation of neuromyelitis optica spectrum disorder (NMOSD) from multiple sclerosis (MS) involving the brainstem and cerebellum. We analyzed the clinical and ocular motor findings, and lesion distribution on brain MRIs in 42 patients with MS (17 men, mean age ± SD = 37 ± 12) and 26 with NMOSD (3 men, mean age ± SD = 43 ± 15) that were recruited from two university hospitals in South Korea (whole study population). An additional subgroup analysis was also conducted in 41 patients presenting acute brainstem or vestibular syndrome (brainstem syndrome population). Logistic regression analysis showed that bilaterality of the lesions (p = 0.012) and presence of horizontal gaze-evoked nystagmus (hGEN, p = 0.041) were more frequently associated with NMOSD than with MS in the whole study population. In the brainstem syndrome population, only hGEN (p = 0.017) was more frequent in NMOSD than in MS. The lesions specific for NMOSD were overlapped in the medial vestibular nucleus (MVN) and nucleus prepositus hypoglossi (NPH) at the pontomedullary junction. In conclusion, presence of hGEN and bilateral lesions involving the MVN and NPH favor the diagnosis of NMOSD rather than MS. [ABSTRACT FROM AUTHOR]

We sought to determine the cerebellar structures responsible for tilt suppression of post-rotatory nystagmus. We investigated ocular motor findings and MRI lesions in 73 patients with isolated cerebellar lesions who underwent recording of the vestibulo-ocular reflex (VOR) using rotatory chair tests. Tilt suppression of post-rotatory nystagmus was diminished in 27 patients (27/73, 37.0 %). The gains of the VOR and the TCs of per- and post-rotatory nystagmus did not differ between the patients with diminished and with normal tilt suppression. The patients with impaired tilt suppression showed perverted ('cross-coupled') head-shaking nystagmus (pHSN) and central positional nystagmus (CPN) more frequently than those with normal responses. Tilt suppression was impaired in five (71.4 %) of the seven patients with isolated nodulus and uvular infarction. Probabilistic lesion-mapping analysis showed that the nodulus and uvula are responsible for tilt suppression. Impaired tilt suppression may be ascribed to disruption of cerebellar contribution to the vestibular velocity-storage mechanism, which integrates information from the semicircular canals and otolith organs to help derive the brain's estimate of the head orientation relative to the pull of gravity. [ABSTRACT FROM AUTHOR]

Rebound nystagmus is a transient nystagmus that occurs on resuming the straight-ahead position after prolonged eccentric gaze. Even though rebound nystagmus is commonly associated with gaze-evoked nystagmus (GEN), development of rebound nystagmus in a different plane of gaze has not been described. We report a patient with episodic ataxia type 2 who showed transient upbeat nystagmus on resuming the straight-ahead position after sustained lateral gaze that had induced GEN and downbeat nystagmus. The rebound upbeat nystagmus may be ascribed to a shifting null in the vertical plane as a result of an adaptation to the downbeat nystagmus that developed during lateral gaze. [ABSTRACT FROM AUTHOR]