Esophoria or esotropia in adulthood: a sign of cerebellar dysfunction?

[What's behind cerebellar dizziness? - News on diagnosis and therapy]

Vertigo and dizziness comprise a multisensory and multidisciplinary syndrome of different etiologies. The term "cerebellar vertigo and dizziness" comprises a heterogenous group of disorders with clinical signs of cerebellar dysfunction and is caused by vestibulo-cerebellar, vestibulo-spinal or cerebellar systems. About 10 % of patients in an outpatient clinic for vertigo and balance disorders suffer from cerebellar vertigo and dizziness. According to the course of the symptoms, one can considers 3 types: permanent complaints, recurrent episodes of vertigo and balance disorders, or an acute onset of complaints. The most common diagnoses in patients with cerebellar vertigo and dizziness were as follows: degenerative disease, hereditary forms and acquired forms. In a subgroup of patients with cerebellar vertigo, central cerebellar oculomotor dysfunction is indeed the only clinical correlate of the described symptoms. 81 % of patients with cerebellar vertigo suffer from permanent, persistent vertigo and dizziness, 31 % from vertigo attacks, and 21 % from both. Typical clinical cerebellar signs, including gait and limb ataxia or dysarthria, were found less frequently. Key to diagnosis is a focused history as well as a thorough clinical examination with particular attention to oculomotor function. Regarding oculomotor examination, the most common findings were saccadic smooth pursuit, gaze-evoked nystagmus, provocation nystagmus, rebound nystagmus, central fixation nystagmus, most commonly downbeat nystagmus, and disturbances of saccades. Thus, oculomotor examination is very sensitive in diagnosing cerebellar vertigo and dizziness, but not specific in distinguishing different etiologies. Laboratory examinations using posturography and a standardized gait analysis can support the diagnosis, but also help to estimate the risk of falls and to quantify the course and possible symptomatic treatment effects. Patients with cerebellar vertigo and dizziness should receive multimodal treatment.

Voxel-based meta-analysis of gray matter and white matter changes in patients with spinocerebellar ataxia type 3

Purpose

Increasing neuroimaging studies have revealed gray matter (GM) and white matter (WM) anomalies of several brain regions by voxel-based morphometry (VBM) studies on patients with spinocerebellar ataxia type 3 (SCA3); however, the findings of previous studies on SCA3 patients by VBM studies remain inconsistent. The study aimed to identify consistent findings of gray matter (GM) and white matter (WM) changes in SCA3 patients by voxel-wise meta-analysis of whole-brain VBM studies.

Methods

VBM studies comparing GM or WM changes in SCA3 patients and healthy controls (HCs) were retrieved from PubMed, Embase, Web of Science, and Medline databases from January 1990 to February 2023. Manual searches were also conducted, and authors of studies were contacted for additional data. The coordinates with significant differences in GM and WM between SCA3 patients and HCs were extracted from each cluster. A meta-analysis was performed using anisotropic effect size-based signed differential mapping (AES-SDM) software.

Results

A total of seven studies comprising 160 SCA3 patients and 165 HCs were included in the GM volume meta-analysis. Three studies comprising 57 SCA3 patients and 63 HCs were included for WM volume meta-analysis. Compared with HC subjects, the reduced GM volume in SCA3 patients was found in the bilateral cerebellar hemispheres, cerebellar vermis, pons, right lingual gyrus, and right fusiform gyrus. The decreased WM volume was mainly concentrated in the bilateral cerebellar hemispheres, right corticospinal tract, middle cerebellar peduncles, cerebellar vermis, and left lingual gyrus. No increased density or volume of any brain structures was found. In the jackknife sensitivity analysis, the results remained largely robust.

Conclusion

Our meta-analysis clearly found the shrinkage of GM and WM volume in patients with SCA3. These lesions are involved in ataxia symptoms, abnormal eye movements, visual impairment, cognitive impairment, and affective disorders. The findings can explain the clinical manifestations and provide a morphological basis for SCA3.

Scale for Ocular motor Disorders in Ataxia (SODA)

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.

Nystagmus: Diagnosis, Topographic Anatomical Localization and Therapy

Nystagmus is defined as rhythmic, most often involuntary eye movements. It normally consists of a slow (pathological) drift of the eyes, followed by a fast central compensatory movement back to the primary position (refixation saccade). The direction, however, is reported according to the fast phase. The cardinal symptoms are, on the one hand, blurred vision, jumping images (oscillopsia), reduced visual acuity and, sometimes, double vision; many of these symptoms depend on the eye position. On the other hand, depending on the etiology, patients may suffer from the following symptoms: 1. permanent dizziness, postural imbalance, and gait disorder (typical of downbeat and upbeat nystagmus); 2. if the onset of symptoms is acute, the patient may experience spinning vertigo with a tendency to fall to one side (due to ischemia in the area of the brainstem or cerebellum with central fixation nystagmus or as acute unilateral vestibulopathy with spontaneous peripheral vestibular nystagmus); or 3. positional vertigo. There are two major categories: the first is spontaneous nystagmus, i.e., nystagmus which occurs in the primary position as upbeat or downbeat nystagmus; and the second includes various types of nystagmus which are induced or modified by certain factors. Examples are gaze-evoked nystagmus, head-shaking nystagmus, positional nystagmus, and hyperventilation-induced nystagmus. In addition, there are disorders similar to nystagmus, such as ocular flutter or opsoclonus. The most common central types of spontaneous nystagmus are downbeat and upbeat, infantile, pure torsional, pendular fixation, periodic alternating, and seesaw nystagmus. Many types of nystagmus allow a precise neuroanatomical localization: for instance, downbeat nystagmus, which is most often caused by a bilateral floccular lesion or dysfunction, or upbeat nystagmus, which is caused by a lesion in the midbrain or medulla. Examples of drug treatment are the use of 4-aminopyridine for downbeat and upbeat nystagmus, memantine or gabapentin for pendular fixation nystagmus, or baclofen for periodic alternating nystagmus. In this article we are focusing on nystagmus. In a second article we will focus on central ocular motor disorders, such as saccade or gaze palsy, internuclear ophthalmoplegia, and gaze-holding deficits. Therefore, these types of eye movements will not be described here in detail.

Clinical Classification of Acquired Concomitant Esotropia

BACKGROUND

Classification and management of acquired concomitant esotropia is controversial. We sought to establish a simple clinical classification in order to determine in which cases further investigations in search of underlying pathologies are necessary.

PATIENTS AND METHODS

Observational retrospective study of the files of 175 consecutive patients examined in our unit between 2009 and 2018 for acute convergent strabismus. One hundred and nine patients were selected, after exclusion of infantile, incomitant, or mechanical esotropias, residual esotropias, and patients examined on a single occasion. All patients received a complete orthoptic and ophthalmological examination. We grouped the patients according to their common characteristics.

RESULTS

We established the following categories: 1. Acute esotropia of large angle (20 to 45 prism diopters [PD]), accompanied by mild hyperopia (mean 1.2 D) in children (n = 16) and moderate myopia (mean 3.7 D) in adolescents and adults (n = 13). 2. Decompensated micro-esotropia, which is distinguished from the other categories by the presence of abnormal retinal correspondence (n = 33). 3. Decompensated esophoria, with intermittent deviations of 5 to 30 PD, esotropia being compensated part of the time (n = 25). 4. Esotropia present only at a distance in patients over 50 years of age (n = 20). 5. Small-angle esotropia (< 15 PD) greater at a distance, associated with oculomotor cerebellar syndrome (n = 2). Complementary examinations (MRI or CT scan) were performed on 21 patients, leading to the discovery of a posterior fossa astrocytoma in a 4-year-old boy.

CONCLUSIONS

The recognition of decompensated micro-esotropia and esophoria, as well as distance esotropia of the elderly, avoids unnecessary additional investigations, which are indicated in any type of acute comitant strabismus if associated with any neurological sign or symptom (e.g., headaches, nausea, vertigo, imbalance, poor coordination, nystagmus, or papilledema). In the absence of neurological findings, there is no consensus about the indication of neuroimaging in large-angle acquired concomitant esotropia, but long-term follow-up of patients that do not undergo neuroimaging is strongly recommended in order to identify later occurring intracranial diseases. This is of particular importance with children.

Static and Dynamic Ocular Motor Abnormalities as Potential Biomarkers in Spinocerebellar Ataxia Type 3

While dynamic ocular motor abnormalities (e.g., gaze-evoked nystagmus (GEN), low optokinetic nystagmus (OKN), pursuit and vestibulo-ocular reflex (VOR) gains, and dysmetric saccades) have been shown to be potential biomarkers in spinocerebellar ataxia type 3 (SCA3), the value of static abnormalities (e.g., convergent [esodeviation] and divergent strabismus [exodeviation]) is unknown. Moreover, studies on dynamic abnormalities in SCA3 usually do not take into account the existence of potential abduction-adduction asymmetries in patients with degenerative ataxia. Thirty-eight patients with genetically confirmed SCA3 (24 females; mean age ± SD, 49.8± 12.2 years) and 22 healthy controls (12 females, p = 0.589; mean age ± SD, 50.7± 12.5 years, p = 0.651) underwent clinical and video-oculographic assessment. A p value < 0.002 (between- and within-group analyses) and < 0.001 (correlation analysis) was considered significant. Patients showed larger esodeviation at distance (p < 0.001), became more esodeviated in lateral gaze (p < 0.001), and their near exodeviation correlated with scale for the assessment and rating of ataxia (SARA) score (p = 0.004). Pursuit, OKN, and VOR gains were lower in patients, both for their adducting and abducting components (p < 0.001). Saccades showed higher velocities (p < 0.001), abducting saccades showed lower amplitude (p < 0.001), and adducting saccades tended to show greater vertical bias (p = 0.018) in patients. Abducting saccades showed relatively lower velocity (p < 0.001) and lower amplitude (p = 0.015) than abducting saccades within patients. All dynamic ocular motor abnormalities except saccades correlated with SARA score, CAG repeat number, and/or disease duration (p < 0.001). Static and dynamic ocular motor abnormalities are potential biomarkers in SCA3. SCA3 studies using saccades should take into account the existence of potential abduction-adduction asymmetries.

Differential Diagnosis of Acquired Esotropia in the Elderly

AIM

To provide an overview of the differential diagnoses of acquired esotropia that occur in the elderly and to facilitate their differentiation in everyday clinical practice.

METHODS

The data of all patients who presented in our outpatient university department for strabology and neuroophthalmology from March 2014 to October 2015 due to esotropia with diplopia with onset after age 50 were evaluated retrospectively. Exclusion criteria were a known strabismus before the age of 50 and/or vertical deviations in the primary position. Anamnestic characteristics, accompanying findings and orthoptic parameters, were analysed.

RESULTS

85 patients were included in the study, 42 of them female and 43 male. The following diagnoses were made: abducens nerve palsy (n = 34, 3 of them both sides), esotropia due to myopia magna (n = 12), esotropia with accompanying neurological symptoms (n = 6) and other etiology (n = 5). In 4 cases, the diagnosis was still unclear at the end of the study. In 24 patients, none of the above diagnoses existed and the diagnosis of "sagging eye syndrome" (ETSAG) was made. The abducens nerve palsy typically showed a sudden onset of double vision, slowed abduction saccades and asymmetrical abduction ability. With unilateral abducens nerve palsy, the esotropia increased continuously from the view to the unaffected side through the primary position to the view to the affected side. Patients with ETSAG and myopia-associated esotropia, on the other hand, reported a gradual onset of double vision, showed normal abduction saccades and a slightly reduced abduction ability. The squint angle often increased slightly to both sides. Esotropia with accompanying neurological symptoms was rare and was seen in various underlying diseases.

CONCLUSIONS

The kind of onset of the double vision, the quality of the saccades, the incomitance pattern and the ability to abduct are important parameters for the etiological assignment of an esotropia in the elderly. The characteristics of the individual diagnoses are described and differential diagnostic aspects are discussed.

Surgical Responses and Outcomes of Bilateral Medial Rectus Recession in Esotropia With Spinocerebellar Ataxia

PURPOSE

To evaluate the surgical responses and outcomes of bilateral medial rectus (BMR) recession in esotropic patients with spinocerebellar ataxia (SCA) and to compare the results with normal controls.

METHODS

The medical records of patients with SCA who underwent strabismus surgery for esotropia between 2006 and 2015 were reviewed retrospectively. Five esotropic patients with SCA (SCA group) and 10 esotropic patients without neurologic disorders (control group) who underwent BMR recession were included. Success rates, surgical responses, and the amount of preoperative and postoperative distance-near disparity were evaluated and compared between the groups.

RESULTS

The mean preoperative esodeviation was not different between the SCA and control groups (20 vs 17.3 prism diopters [PD], P = .214). However, patients with SCA showed significant undercorrection compared with controls 1 week postoperatively (4.8 vs 1.0 PD, P = .048) and at the final follow-up (6.8 vs 1.8 PD, P = .032). The surgical success rates for the SCA and control groups were 40% and 80%, respectively (P = .095). Patients with SCA demonstrated a significantly reduced surgical response compared with controls (3.15 vs 3.87 PD/mm, P = .004), and a greater amount of postoperative distance-near disparity than controls (8.0 vs 1.1 PD, P = .001).

CONCLUSIONS

A significant undercorrection was observed following BMR recession in esotropic patients with SCA. Accordingly, the authors recommend a slight overcorrection of 5 to 10 PD or adding a slanting procedure when planning strabismus surgery for this distinct group of patients. [J Pediatr Ophthalmol Strabismus. 2019;56(4):266-270.].

Curation and bioinformatic analysis of strabismus genes supports functional heterogeneity and proposes candidate genes with connections to RASopathies

Strabismus refers to the misalignment of the eyes and occurs in 2-4% of individuals. The low-resolution label "strabismus" covers a range of heterogeneous defects, which makes it challenging to unravel this condition. Consequently a coherent understanding of the causes is lacking. Here, we attempt to gain a better understanding of the underlying genetics by combining gene curation, diverse bioinformatic analyses (including gene ontology, pathway mapping, expression and network-based methods) and literature review. Through a phenotype-based curation process, we identify high-confidence and permissive sets of 54 and 233 genes potentially involved in strabismus. These genes can be grouped into 10 modules that together span a heterogeneous set of biological and molecular functions, and can be linked to clinical sub-phenotypes. Multiple lines of evidence associate retina and cerebellum biology with the strabismus genes. We further highlight a potential role of the Ras-MAPK pathway. Independently, sets of 11 genes and 15 loci tied to strabismus with definitive genetic basis have been compiled from the literature. We identify strabismus candidate genes for 5 of the 15 reported loci (CHD7; SLC9A6; COL18A1, COL6A2; FRY, BRCA2, SPG20; PARK2). Finally, we synthesize a Strabismus Candidate Gene Collection, which together with our curated gene sets will serve as a resource for future research. The results of this informatics study support the heterogeneity and complexity of strabismus and point to specific biological pathways and brain regions for future focus.

Oculomotor and Vestibular Findings in Gaucher Disease Type 3 and Their Correlation with Neurological Findings

Objectives

To evaluate the function of the oculomotor and vestibular systems and to correlate these findings with the clinical status of patients with Gaucher disease type 3 (GD3). The goal of this cross-sectional and longitudinal study was to find oculomotor biomarkers for future clinical trials.

Methods

Twenty-six patients with GD3 were assessed for eligibility and 21 were able to perform at least one task. Horizontal and vertical reflexive saccades, smooth pursuit, gaze-holding, optokinetic nystagmus, and horizontal vestibulo-ocular reflex (VOR) were examined by video-oculography/video-head impulse test and compared concurrently with 33 healthy controls. The Scale for the Assessment and Rating of Ataxia (SARA), the modified Severity Scoring Tool (mSST), and Grooved Pegboard Test (GPT) were administered to assess overall neurological function. Eleven patients were also re-assessed after 1 year.

Results

Nine out of 17 patients exhibited gaze-holding deficits. One patient had upbeat nystagmus. Three patients presented with bilateral abducens palsy in combination with central oculomotor disorders, suggesting a bilateral involvement of the abducens nucleus. Horizontal angular VOR gain was reduced in all patients (0.66 ± 0.37) compared with controls (1.1 ± 0.11, p < 0.001). Most strongly correlated with clinical rating scales were peak velocity of downward saccades (SARA: ρ = −0.752, p < 0.0005; mSST: ρ = −0.611, p = 0.003; GPT: ρ = −0.649, p = 0.005) and duration of vertical saccades (SARA: ρ = 0.806, p < 0.001; mSST: ρ = 0.700, p < 0.0005; GPT: ρ = 0.558, p = 0.02) together with the VOR gain (SARA: ρ = −0.63, p = 0.016; mSST: ρ = −0.725, p = 0.003; GPT: ρ = −0.666, p = 0.004). Vertical smooth pursuit gain decreased significantly at follow-up.

Interpretation

This study shows neuronal degeneration of the brainstem and cerebellum with combined involvement of both supranuclear and nuclear oculomotor structures and the vestibular system in GD3. We also identified oculomotor parameters that correlate with the neurological status and can be used as biomarkers in future clinical trials.

Consensus Paper: Revisiting the Symptoms and Signs of Cerebellar Syndrome

The cerebellum is involved in sensorimotor operations, cognitive tasks and affective processes. Here, we revisit the concept of the cerebellar syndrome in the light of recent advances in our understanding of cerebellar operations. The key symptoms and signs of cerebellar dysfunction, often grouped under the generic term of ataxia, are discussed. Vertigo, dizziness, and imbalance are associated with lesions of the vestibulo-cerebellar, vestibulo-spinal, or cerebellar ocular motor systems. The cerebellum plays a major role in the online to long-term control of eye movements (control of calibration, reduction of eye instability, maintenance of ocular alignment). Ocular instability, nystagmus, saccadic intrusions, impaired smooth pursuit, impaired vestibulo-ocular reflex (VOR), and ocular misalignment are at the core of oculomotor cerebellar deficits. As a motor speech disorder, ataxic dysarthria is highly suggestive of cerebellar pathology. Regarding motor control of limbs, hypotonia, a- or dysdiadochokinesia, dysmetria, grasping deficits and various tremor phenomenologies are observed in cerebellar disorders to varying degrees. There is clear evidence that the cerebellum participates in force perception and proprioceptive sense during active movements. Gait is staggering with a wide base, and tandem gait is very often impaired in cerebellar disorders. In terms of cognitive and affective operations, impairments are found in executive functions, visual-spatial processing, linguistic function, and affective regulation (Schmahmann's syndrome). Nonmotor linguistic deficits including disruption of articulatory and graphomotor planning, language dynamics, verbal fluency, phonological, and semantic word retrieval, expressive and receptive syntax, and various aspects of reading and writing may be impaired after cerebellar damage. The cerebellum is organized into (a) a primary sensorimotor region in the anterior lobe and adjacent part of lobule VI, (b) a second sensorimotor region in lobule VIII, and (c) cognitive and limbic regions located in the posterior lobe (lobule VI, lobule VIIA which includes crus I and crus II, and lobule VIIB). The limbic cerebellum is mainly represented in the posterior vermis. The cortico-ponto-cerebellar and cerebello-thalamo-cortical loops establish close functional connections between the cerebellum and the supratentorial motor, paralimbic and association cortices, and cerebellar symptoms are associated with a disruption of these loops.

Eye movements in vestibular disorders

The differential diagnosis of patients with vestibular symptoms usually begins with the question: is the lesion central or is it peripheral? The answer commonly emerges from a careful examination of eye movements, especially when the lesion is located in otherwise clinically silent areas of the brain such as the vestibular portions of the cerebellum (flocculus, paraflocculus which is called the tonsils in humans, nodulus, and uvula) and the vestibular nuclei as well as immediately adjacent areas (the perihypoglossal nuclei and the paramedian nuclei and tracts). The neural circuitry that controls vestibular eye movements is intertwined with a larger network within the brainstem and cerebellum that also controls other types of conjugate eye movements. These include saccades and pursuit as well as the mechanisms that enable steady fixation, both straight ahead and in eccentric gaze positions. Navigating through this complex network requires a thorough knowledge about all classes of eye movements to help localize lesions causing a vestibular disorder. Here we review the different classes of eye movements and how to examine them, and then describe common ocular motor findings associated with central vestibular lesions from both a topographic and functional perspective.