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Eye movements are fundamental diagnostic and progression markers of various neurological diseases, including those affecting the cerebellum. Despite the high prevalence of abnormal eye movements in patients with cerebellar disorders, the traditional rating scales do not focus on abnormal eye movements. We formed a consortium of neurologists focusing on cerebellar disorders. The consortium aimed to design and validate a novel Scale for Ocular motor Disorders in Ataxia (SODA). The primary purpose of the scale is to determine the extent of ocular motor deficits due to various phenomenologies. A higher score on the scale would suggest a broader range of eye movement deficits. The scale was designed such that it is easy to implement by non-specialized neurological care providers. The scale was not designed to measure each ocular motor dysfunction's severity objectively. Our validation studies revealed that the scale reliably measured the extent of saccade abnormalities and nystagmus. We found a lack of correlation between the total SODA score and the total International Cooperative Ataxia Rating Scale (ICARS), Scale for Assessment and Rating of Ataxia (SARA), or Brief Ataxia Rating Scale (BARS). One explanation is that conventionally reported scales are not dedicated to eye movement disorders; and when present, the measure of ocular motor function is only one subsection of the ataxia rating scales. It is also possible that the severity of ataxias does not correlate with eye movement abnormalities. Nevertheless, the SODA met the consortium's primary goal: to prepare a simple outcome measure that can identify ocular motor dysfunction in patients with cerebellar ataxia. • Scale for Ocular Motor Disorders in Ataxia is presented. • The scale is an objective measure of eye movement burden in ataxia. • It is operator friendly and is validated with video oculography. [ABSTRACT FROM AUTHOR]

The brainstem contains numerous structures and their afferent and efferent fibers that are involved in generation and control of eye movements. These structures give rise to distinct patterns of abnormal eye movements when damaged. Thus, defining these ocular motor abnormalities allows a topographic diagnosis of a lesion in various disorders involving the brainstem. Even though diverse patterns of impaired eye movements may be observed in lesions affecting anywhere along the brainstem, medullary lesions mostly present various patterns of nystagmus and impaired vestibular eye movements without obvious ophthalmoplegia. In contrast, pontine ophthalmoplegia is characterized by abnormal eye movements in the horizontal plane while midbrain lesions typically show vertical ophthalmoplegia in addition to pupillary and eyelid abnormalities. Recognition of the patterns and characteristics of abnormal eye movements observed in brainstem lesions is important in understanding the roles of each neural structure and circuit in ocular motor control as well as in localizing the lesions by determining the involved structures. [ABSTRACT FROM AUTHOR]

Abstract: Ocular neuromyotonia refers to paroxysmal involuntary contraction of one or more ocular muscles resulting in paroxysmal diplopia and strabismus. A 73-year-old woman reported spells of horizontal diplopia that usually developed after leftward gaze and mostly lasted less than one minute. Between the episodes, the extraocular movements were normal without aberrant regeneration. The diplopic paroxysms could be triggered by leftward gaze for several seconds. During the episode, the left eye was exotropic with mild adduction limitation. Brain imaging revealed an aneurysm in the left internal carotid artery. The episodes resolved with carbamazepine. Aneurysm of the internal carotid artery is a rare cause of abducens neuromyotonia. A compressive lesion may give rise to ocular neuromyotonia even in the absence of prior irradiation. [Copyright &y& Elsevier]

Abstract: Even though pendular seesaw nystagmus (PSN) or periodic alternating nystagmus (PAN) has been reported in blind persons, the co-occurrence of PSN and PAN has not been described. A 69-year-old woman with progressive visual loss to only light perception in both eyes showed PSN with a conjugate torsional component and the vertical components in the opposite directions in both eyes. In complete darkness, she also exhibited PAN in addition to PSN. PSN remained unchanged in darkness. The rest of the neurological examination, testing for mitochondrial mutations of Leber''s hereditary optic neuropathy, fluorescent angiography, electroretinogram, and brain MRI were normal except for bilateral optic atrophy. Deprivation of the visual inputs, which are required to calibrate normal eye motion, may produce various ocular motor abnormalities in blindness. Although the co-occurrence of PSN and PAN in our patient with visual loss indicates a common etiology, the different effects of darkness on nystagmus intensity suggest a distinct pathomechanism. [Copyright &y& Elsevier]

Abstract: Background: To elucidate the mechanisms of paroxysmal ocular tilt reaction (OTR) from mesodiencephalic lesions by analyzing the associated ocular motor findings. Methods: Two patients with paroxysmal ipsiversive OTR due to mesodiencephalic lesions underwent evaluation of associated ocular motor abnormalities and one of them had three-dimensional recording of eye motion. We also reviewed previously reported six patients with paroxysmal OTR. Results: One patient showed contraversive torsional nystagmus during the paroxysms in association with vertical gaze limitation and vertical gaze-evoked nystagmus, which are consistent with baseline dysfunction and paroxysmal irritation of the interstitial nucleus of Cajal (INC) during the attacks. The other patient exhibited ipsiversive torsional nystagmus during the attacks, along with slowed vertical saccades and decreased amplitude of ipsitorsional nystagmus during the torsional vestibulo-ocular reflex between the attacks. These findings are best explained by underlying dysfunction and paroxysmal irritation of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). Conclusions: The associated ocular motor findings in our patients indicate that paroxysmal ipsiversive OTR in mesodiencephalic lesions is caused by intermittent hyperactivity of partially damaged ipsilesional riMLF or INC. [Copyright &y& Elsevier]

Abstract: Background: In benign paroxysmal positional vertigo involving the horizontal canal (HC-BPPV), nystagmus may be induced by neck flexion in the pitch plane while sitting (head-bending nystagmus). Objective: To determine the characteristics and lateralizing value of head-bending nystagmus in HC-BPPV. Methods: Using video-oculography, head-bending nystagmus was recorded in 54 patients with HC-BPPV (32 canalolithiasis and 22 cupulolithiasis). Lesion side was determined by comparing intensity of the nystagmus induced by lateral head turning (head-turning nystagmus) in supine. Results: Head-bending nystagmus was observed in 39 patients (72.2%) and lying-down nystagmus in 41 (75.9%). Thirty three patients (61.1%) showed both types of nystagmus while six (11.1%) had only head-bending and another eight (14.8%) showed only lying-down nystagmus. In 45 patients with asymmetrical head-turning nystagmus, the direction of head-bending nystagmus was mostly toward the affected ear in canalolithasis (88.9%) and toward the intact ear in cupulolithasis (80.0%). In 9 (16.7%) patients whose affected ear could not be determined due to symmetrical head-turning nystagmus, the particle repositioning maneuver based on the direction of head-bending or lying-down nystagmus resulted in the resolution of symptom. Two patients showed a transition from canalo- to cupulolithiasis during head-bending posture. Conclusion: In HC-BPPV, neck flexion in the pitch plane while sitting may generate nystagmus by inducing ampullopetal migration of the otolithic debris in the horizontal canal or by ampullofugal deflection of the cupula by the attached otolithic debris. Head-bending nystagmus may be a valuable sign for lateralizing the involved canal in HC-BPPV, especially when patients show symmetrical head-turning nystagmus. Conversion of canalo- into cupulolithiasis by the neck flexion supports the current explanation of the mechanisms of HC-BPPV. [Copyright &y& Elsevier]

Abstract: A 33-year-old woman with Wernicke''s encephalopathy (WE) due to poor oral intake after allogeneic stem cell transplantation for acute myeloid leukemia showed a sequential development of bilateral gaze-evoked nystagmus (GEN), rightward gaze palsy, and upbeat nystagmus. Initial MRIs obtained when she had GEN only showed a lesion involving the medullary tegmentum, and follow-up MRIs revealed additional lesions in the pontine and midbrain tegmentum along with development of rightward gaze palsy, and finally bilateral medial thalamus lesions in association with upbeat nystagmus. The evolution of abnormal ocular motor findings and serial MRI changes in our patient with WE provide imaging evidence on relative vulnerability of the neural structures, and on the progression of lesions and ocular motor findings in thiamine deficiency. [Copyright &y& Elsevier]

Abstract: A 66-year-old man developed primary position upbeat nystagmus and bilateral internuclear ophthalmoplegia (INO). Video-oculography showed primary position upbeat nystagmus with exponentially decreasing slow phases, which disappeared in darkness. Brain MRI disclosed enhancing lesions involving bilateral dorsomedial pons extending from the middle to upper portion. Upbeat nystagmus in association with bilateral INO may be attributed by the damage of the cell groups of the paramedian tracts (PMT), the projections from the interstitial nucleus of Cajal (INC) to PMT, or the connections between INC and the nucleus of Roller. [Copyright &y& Elsevier]