Is hypovitaminosis D one of the environmental risk factors for multiple sclerosis?

The role of hypovitaminosis D as a possible risk factor for multiple sclerosis is reviewed. First, it is emphasized that hypovitaminosis D could be only one of the risk factors for multiple sclerosis and that numerous other environmental and genetic risk factors appear to interact and combine to trigger the disease. Secondly, the classical physiological notions about vitamin D have recently been challenged and the main new findings are summarized. This vitamin could have an important immunological role involving a number of organs and pathologies, including autoimmune diseases and multiple sclerosis. Furthermore, human requirements for this vitamin are much higher than previously thought, and in medium- or high-latitude countries, they might not be met in the majority of the general population due to a lack of sunshine and an increasingly urbanized lifestyle. Thereafter, the different types of studies that have helped to implicate hypovitaminosis D as a risk factor for multiple sclerosis are reviewed. In experimental autoimmune encephalomyelitis, vitamin D has been shown to play a significant immunological role. Diverse epidemiological studies suggest that a direct chain of causality exists in the general population between latitude, exposure to the sun, vitamin D status and the risk of multiple sclerosis. New epidemiological analyses from France support the existence of this chain of links. Recently reported immunological findings in patients with multiple sclerosis have consistently shown that vitamin D significantly influences regulatory T lymphocyte cells, whose role is well known in the pathogenesis of the disease. Lastly, in a number of studies on serum levels of vitamin D in multiple sclerosis, an insufficiency was observed in the great majority of patients, including at the earliest stages of the disease. The questionable specificity and significance of such results is detailed here. Based on a final global analysis of the cumulative significance of these different types of findings, it would appear likely that hypovitaminosis D is one of the risk factors for multiple sclerosis.

Five-year outcome in the copaxone observatory: a nationwide cohort of patients with multiple sclerosis starting treatment with glatiramer acetate in France.

The benefits provided by disease-modifying treatments in multiple sclerosis have been demonstrated in clinical trials, but the extent to which they can be extrapolated to everyday care is less clear, as are the long-term benefits of treatment. The objective of this prospective observational cohort study performed in France was to evaluate the effectiveness and safety of glatiramer acetate in patients with relapsing-remitting multiple sclerosis over a 5-year period. All neurologists in France were invited to participate and enroll adult patients starting a first treatment with brand glatiramer acetate 20 mg. Given the observational nature of the study, no fixed study visits were imposed; consultations took place according to the investigator's normal practice. Occurrence of disease exacerbations and adverse events was documented and neurological disability evaluated with the EDSS at each consultation. Overall, 852 patients were analysable and 269 took glatiramer acetate continuously for 5 years. Median treatment duration was 3.4 years. Principal reasons for discontinuation were inadequate efficacy (38.9%), local tolerability (22.6%) and personal convenience (21.3%). Age, employment status, baseline EDSS score and number of previous exacerbations were variables associated with treatment persistence. The annualised exacerbation rate (5 years) was 0.41 [95% CI 0.39-0.44]; 316 patients (37.2%) remained exacerbation-free throughout. The risk of confirmed disability worsening (5 years) was 43.8% [95% CI 39.9-47.9%]. The most frequent adverse drug reactions were local injection site reactions (584 patients; 68.5%) and systemic immediate post-injection reactions (168 patients; 19.7%). Overall, these findings are consistent with those of previous clinical trials.

Cholecalciferol in relapsing-remitting MS: A randomized clinical trial (CHOLINE).

OBJECTIVE: To evaluate the safety and efficacy of cholecalciferol in patients with relapsing-remitting MS (RRMS). METHODS: In this double-blind, placebo-controlled parallel-group, 2-year study, 181 patients with RRMS were randomized 1:1. Key inclusion criteria were a low serum 25-hydroxy vitamin D (25OHD) concentration (<75 nmol/L), a treatment with interferon beta-1a 44 µg (SC 3 times per week) 4 months ± 2 months before randomization, and at least one documented relapse during the previous 2 years. Patients received high-dose oral cholecalciferol 100,000 IU or placebo every other week for 96 weeks. Primary outcome measure was the change in the annualized relapse rate (ARR) at 96 weeks. Secondary objectives included safety and tolerability of cholecalciferol and efficacy assessments (ARR, MRI parameters, and Expanded Disability Status Scale [EDSS]). RESULTS: The primary end point was not met. In patients who completed the 2-year follow-up (45 with cholecalciferol and 45 with placebo), all efficacy parameters favored cholecalciferol with an ARR reduction (p = 0.012), less new hypointense T1-weighted lesions (p = 0.025), a lower volume of hypointense T1-weighted lesions (p = 0.031), and a lower progression of EDSS (p = 0.026). The overall rate of adverse events was well balanced between groups. CONCLUSIONS: Although the primary end point was not met, these data suggest a potential treatment effect of cholecalciferol in patients with RRMS already treated with interferon beta-1a and low serum 25OHD concentration. Together with the good safety profile, these data support the exploration of cholecalciferol treatment in such patients with RRMS. CLINICALTRIALSGOV IDENTIFIER: NCT01198132. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that for patients with RRMS and low serum 25OHD, cholecalciferol did not significantly affect ARRs.

Upbeat nystagmus from a demyelinating lesion in the caudal pons.

A 51-year-old man developed positional vertigo, ataxia, dysgeusia, diplopia, and oscillopsia. Eye movement examination and video-oculographic recording disclosed primary position upbeat nystagmus (PPUN) and a right internuclear ophthalmoplegia. Brain MRI showed a small focal lesion in the right dorsal tegmentum of the caudal pons with signal characteristics consistent with a primary demyelinating central nervous system disease. PPUN has not been described previously with a lesion in such a location. Clinicoanatomic correlation in this patient suggests that a lesion of the superior vestibular nucleus and its efferent crossing ventral tegmental tract could be responsible for the PPUN. This case report contributes to a better understanding of the role of this pathway in humans.

Visual vector inversion in the posterior parietal cortex.

In the antisaccade task, a saccade must be triggered towards the mirror location of a visual target. The neural basis required for this visual vector inversion remains unclear, although neuronal activities reflecting this process have been recorded in the monkey lateral intraparietal area. We examined a patient with a small, right-sided, posterior parietal stroke who complained of difficulty in manipulating visual information. Antisaccades were markedly hypometric rightwards but normal leftwards. Largely unaffected performances in other saccade tasks revealed that visual and motor processing were not significantly affected. Antisaccade inaccuracy could therefore be ascribed to the impairment of visual vector inversion, a processing specifically required in this task. These findings provide the first evidence in humans that visual vector inversion could be an intrinsic property of the posterior parietal cortex.

Prefrontal cortex is involved in internal decision of forthcoming saccades.

Deciding where to look is mandatory to explore the visual world. To study the neural correlates subserving the cognitive phase of self-initiated eye movements in humans, we tested 12 healthy participants, using event-related functional MRI. Changes in the frontal-cortical activity preceding voluntary saccades were studied when the participants freely decided the direction of a forthcoming saccade, compared with a condition in which they had only to prepare an externally cued saccade. Self-initiation of saccades, before their execution, was specifically associated with frontal-lobe activation in the dorsolateral prefrontal cortex, and in the right presupplementary eye field and frontal eye fields, suggesting the roles of these areas in the decision process of where to look when facing two possible visual targets.

Lateralized parietal activity during decision and preparation of saccades.

The posterior parietal cortex is involved in numerous visuospatial tasks, but little is known about the lateralization of these functions. We used functional magnetic resonance imaging to map the posterior parietal areas involved in saccades. Cerebral activation was studied during three different steps of saccadic elaboration: internal Decision of where to direct a horizontal saccade, motor Preparation and saccade Execution. These steps activated distinct areas: Decision and Preparation selectively activated the left posterior parietal cortex (left deep posterior intraparietal sulcus and left medial posterior intraparietal sulcus), whereas Execution activated only the right posterior parietal cortex (right medial posterior intraparietal sulcus). In humans, left but not right posterior parietal cortex might be specifically related to decision making and preparation of forthcoming ocular saccades.

Vitamin D and multiple sclerosis: An update.

The most recent findings linking exposure to sun and vitamin D insufficiency to multiple sclerosis (MS) are reviewed. Due to insufficient sunshine and changing lifestyles, hypovitaminosis D is widespread in temperate countries. Numerous epidemiological studies have strongly suggested that sunshine and vitamin D insufficiency contributes to MS risk in these countries. Moreover, several large genetic studies in MS patients have recently stated unequivocally that diverse abnormalities involving vitamin D metabolism are related to the risk of the disease. The important implications of such results are discussed here. Then, the interactions of hypovitaminosis D with the other genetic and environmental protective and risk factors, such as the allele HLA DRB1*1501, Epstein-Barr virus infection, obesity, smoking and sexual hormones, are summarized. Vitamin D insufficiency and sufficiency could be a risk and a protective factor, respectively, among many other factors possibly continuously modulating the global MS risk from the mother's pregnancy to the triggering of MS in adulthood. However, many interactions between these different factors occur more particularly between conception and the end of adolescence, which corresponds to the period of maturation of the immune system and thymus and may be related to the dysimmune nature of the disease. The main mechanisms of action of vitamin D in MS appear to be immunomodulatory, involving the various categories of T and B lymphocytes in the general immune system, but neuroprotector and neurotrophic mechanisms could also be exerted at the central nervous system level. Furthermore, several controlled immunological studies performed in MS patients have recently confirmed that vitamin D supplementation has multiple beneficial immunomodulatory effects. However, there is still an enduring absence of major conclusive randomized clinical trials testing vitamin D supplementation in MS patients because of the quasi-insurmountable practical difficulties that exist nowadays in conducting and completing over several years such studies involving the use of a vitamin. Nevertheless, it should be noted that similar robust statistical models used in five different association studies have already predicted a favorable vitamin D effect reducing relapses by 50-70%. If there is now little doubt that vitamin D exerts a beneficial action on the inflammatory component of MS, the results are as yet much less clear for the progressive degenerative component. Lastly, until more information becomes available, vitamin D supplementation of MS patients, using a moderate physiological dose essentially correcting their vitamin insufficiency, is recommended.

The prefrontal substrate of reflexive saccade inhibition in humans.

BACKGROUND: Prefrontal dysfunction in neuropsychiatric disorders such as schizophrenia has been shown to impair inhibition of reflexive saccadic eye movements; however, it is unclear whether reflexive saccade inhibition can be attributed to a distinct subregion of the human prefrontal cortex. METHODS: We tested 15 patients with acute unilateral ischemic lesions of the prefrontal cortex and 20 control subjects with an antisaccade task. Lesions were reconstructed using Talairach coordinates, and possible candidate regions for reflexive saccade inhibition were identified. RESULTS: Significantly increased antisaccade error rates were observed in patients with lesions affecting a region in mid-dorsolateral prefrontal cortex or the white matter between this region and the anterior portions of the internal capsule. Antisaccade error rates of patients with lesions outside this region were normal. These findings were largely independent of lesion volume, postlesion delay, and subject age. CONCLUSIONS: Our findings suggest that inhibition of reflexive saccades depends on a circumscribed subregion of the human dorsolateral prefrontal cortex. This region closely corresponds to Brodmann area 46 as defined by recent cytoarchitectonic studies. Increased antisaccade error rates in patients with prefrontal pathology may be explained by dysfunction of this region.

Cortical mechanisms of saccade generation from execution to decision.

Several cortical areas are involved in the control of ocular motor behavior, but little is known about the cognitive processes occurring prior to saccade triggering. The use of functional brain imaging allows a better understanding of the networks involved specifically in distinct processes of saccade generation. The use of sophisticated visual stimulation paradigms in functional imaging studies suggests that the decision process of where to look when faced with visual alternatives is subserved by a prefrontoparietal network, including the dorsolateral prefrontal cortex.

[Eye movement: from basic semiology to cognitive neuroscience]. / Mouvements oculaires: de la sémiologie elémentaire aux neurosciences cognitives.

Eye movements are an integral part of visual function. They are particularly well developed in frontal-eyed predator species. The abducens nuclei ensure lateral ocular motor synergy, while the oculomotor nuclei control vertical eye movements and convergence. The two main types of conjugate eye movement--saccades (image switching) and slow movements (image stabilization)--are controlled by specific brainstem premotor structures (respectively reticular and vestibular). Upstream of the brainstem, the cortical and subcortical pathways involved in eye movements are gradually being elucidated. Saccades are being used as a motor model to study the different cognitive processes, such as spatial memory, prediction and decision, involved in general movement preparation. The classical approaches based on lesion analysis, combined with transcranial magnetic stimulation and functional cerebral imaging, are contributing to our understanding of how the brain functions. Eye movements can be used for bedside diagnostic purposes, but also for sophisticated laboratory studies designed to explore the universe of cognition.

Neuropsychiatric disturbances in presumed late-onset cobalamin C disease.

BACKGROUND: Combined methylmalonic aciduria and homocystinuria cobalamin C type (cobalamin C disease) is an inborn metabolic disorder consisting of an impaired intracellular synthesis of the 2 active forms of vitamin B12 (cobalamin), namely, adenosylcobalamin and methylcobalamin, that results in increased levels of methylmalonic acid and homocysteine in the blood and urine. Most patients present in the first year of life with systemic, hematological, and neurological abnormalities. Late-onset forms are rare and had not been comprehensively characterized. They could be easily misdiagnosed. OBJECTIVE: To describe clinical and biochemical features of the disease in 2 siblings affected with presumed late-onset cobalamin C disease. DESIGN: Case report and review of the literature. SETTING: Neurological intensive care unit of a university hospital. OBSERVATION: We describe 2 patients with neurological deterioration due to presumed cobalamin C disease. A 16-year-old girl was initially seen with psychosis and severe progressive neuropathy requiring mechanical ventilatory support and her 24-year-old sister had a 2-year disease course of subacute combined degeneration of the spinal cord. A metabolic workup displayed increased methylmalonic acid levels, severe hyperhomocysteinemia, and low plasma methionine levels. The diagnosis was then confirmed by demonstration of impaired synthesis of adenosylcobalamin and methylcobalamin in cultured skin fibroblasts and Epstein-Barr virus-infected lymphocytes. Under specific treatment the younger sister's condition dramatically improved. CONCLUSIONS: Although complementation studies have not been conducted, it is most likely these patients had cobalamin C disease. This study emphasizes the possibility of late-onset disease with purely neurological manifestations. Left untreated, this treatable condition can lead to death or irreversible damage to the nervous system. Screening for intracellular vitamin B12 dysmetabolism should, therefore, be considered in the investigation of adults with unexplained neurological disease, particularly when they are initially seen with a clinical picture suggestive of vitamin B12 deficiency.

Intraoperative frontal eye field stimulation elicits ocular deviation and saccade suppression.

Cortical stimulation is a useful way of elucidating the cortical control of eye movements. The aim of this study was to determine the type of eye movements evoked in response to intraoperative electrical stimulation of the frontal eye field (FEF) region in a fully awake patient during surgery for a frontal lobe glioma. A train of low-intensity electrical pulses within an area in the precentral gyrus evoked contraversive smooth eye movements (SEM) recorded electro-oculographically. Stimulation of an anterior sub-region of this electrically determined FEF disclosed both SEM and suppression of self-paced saccades. However, electrical stimulation of this region evoked no saccades in agreement with pre-operative fMRI using a self-paced saccade paradigm, which did not show activation within the ipsilateral FEF. In humans, intraoperative FEF stimulation may elicit recordable contraversive SEM, and interfere with oculomotor behaviour, suppressing self-paced saccades.

[The control of gaze (3). Neurological defects]. / Déficits neurologiques.

Eye movements serve vision, which has two different aims: changing images using saccades, i.e. rapid eye movements, and stabilizing new images on the retina using slow eye movements. Eye movements are performed by ocular motor nuclei in the brainstem, on which supranuclear pathways--originating in the cerebral cortex, cerebellum and vestibular structures--converge. It is useful for the neurologist to know the clinical abnormalities of eye movements visible at the bedside since such signs are helpful for localization. Eye movement paralysis may be nuclear or infranuclear (nerves), involving all types of eye movements, i.e. saccades as well as the vestibulo-ocular reflex (VOR), or supranuclear, in which case the VOR is usually preserved. Lateral eye movements are organized in the pons, with paralysis of adduction (and preservation of convergence) when the lesion affects the medial longitudinal fasciculus (internuclear ophthalmoplegia), paralysis of conjugate lateral eye movements when the lesion affects the abducens nucleus (VI) and the "one-and-a-half" syndrome when both these structures are involved. Vertical eye movements are organized in the midbrain, with ipsilateral oculomotor (III) paralysis and contralateral paralysis of the superior rectus muscle when the third nerve nucleus is unilaterally damaged, supranuclear upward gaze paralysis when the posterior commissure is unilaterally damaged and supranuclear downward gaze paralysis (often coupled with upward gaze paralysis) when the mesencephalic reticular formations are bilaterally damaged. Numerous types of abnormal eye movements exist, of which nystagmus is the most frequent and usually due to damage to peripheral or central vestibular pathways. Cerebral hemispheric or cerebellar damage results in subtle eye movement abnormalities at the bedside, in general only detected using eye movement recordings, because of the multiplicity of eye movement pathways at these levels and their reciprocal compensation in the case of a lesion. Lastly, eye movements can also help the neuroscientist to understand the organization of the brain. They are a good model of motricity allowing us, using eye movement recordings, to study the afferent pathways of the cortical areas that trigger them, and thus to analyze relatively complex neuropsychological processes such as visuo-spatial integration, spatial memory, motivation and the preparation of motor programs.

Contribution of vitamin D insufficiency to the pathogenesis of multiple sclerosis.

The contribution of vitamin D insufficiency to the pathogenesis of multiple sclerosis (MS) is reviewed. Among the multiple recently discovered actions of vitamin D, an immunomodulatory role has been documented in experimental autoimmune encephalomyelitis and in humans. This action in the peripheral immune system is currently the main known mechanism through which vitamin D might influence MS, but other types of actions could be involved within the central nervous system. Furthermore, vitamin D insufficiency is widespread in temperate countries and in patients with MS at the earliest stages of the disease, suggesting that the deleterious effects related to vitamin D insufficiency may be exerted in these patients. In fact, many genetic and environmental risk factors appear to interact and contribute to MS. In genetics, several human leukocyte antigen (HLA) alleles (more particularly HLA-DRB1*1501) could favour the disease whereas some others could be protective. Some of the genes involved in vitamin D metabolism (e.g. CYP27B1) also play a significant role. Furthermore, three environmental risk factors have been identified: past Epstein-Barr virus infection, vitamin D insufficiency and cigarette smoking. Interactions between genetic and environmental risk or protective factors may occur during the mother's pregnancy and could continue during childhood and adolescence and until the disease is triggered in adulthood, therefore possibly modulating the MS risk throughout the first decades of life. Furthermore, some clinical findings already strongly suggest that vitamin D status influences the relapse rate and radiological lesions in patients with MS, although the results of adequately powered randomized clinical trials using vitamin D supplementation have not yet been reported. While awaiting these incontrovertible results, which might be long in coming, patients with MS who are currently in vitamin D insufficiency should be supplemented, at least for their general health status, using moderate doses of the vitamin.

Relationship between 25-OH-D serum level and relapse rate in multiple sclerosis patients before and after vitamin D supplementation.

BACKGROUND: Vitamin D could play a protective role in multiple sclerosis. METHODS: In an observational, uncontrolled study, vitamin D3 supplementation (3010 IU/day on average) was given to 156 consecutive patients with relapsing-remitting multiple sclerosis, under first-line immunomodulatory therapy and with initial 25-OH-D serum level lower than 100 nmol/l (40 ng/ml). Relapses were determined for 29.1 ± 8.4 months during vitamin D and 29.8 ± 10.1 months before supplementation. The 25-OH-D level was measured before supplementation and several times during supplementation. The incidence rate of relapses before and during supplementation was estimated using negative binomial regression models with follow-up durations as offset terms. The incidence rate and incidence rate ratio of relapses at various 25-OH-D levels were also calculated using negative binomial regression models. RESULTS: In 76 patients, immunomodulatory therapy preceded vitamin D supplementation (by 4.2 ± 2.7 years) and in 80 patients both treatments were started simultaneously. Under supplementation, the 25-OH-D level increased from 49 ± 22 nmol/l to 110 ± 26 nmol/l on average. Pooling data collected before and during supplementation, we found a significant strong inverse relationship between the relapse incidence rate and the 25-OH-D level (p < 0.0001), suggesting that vitamin D did indeed influence the relapse rate. Results of univariate, bivariate and multivariate analyses were analogous: in the multivariate model adjusted for age, disease duration and previous use of immunomodulatory therapy, every 10 nmol increase in 25-OH-D level was associated with a reduction in the relapse incidence rate of 13.7%. Dividing iteratively the population made up of pooled periods into two subgroups according to the 25-OH-D levels, the relapse incidence rate ratio decreased as the 25-OH-D level increased up to 110 nmol/l, but a plateau effect was observed beyond this limit. CONCLUSION: Further studies are warranted for accurate quantification of the vitamin D effect.

When should we measure vitamin D concentration in clinical practice?

The many recently published data on vitamin D have raised much interest in the medical community. One of the consequences has been a great increase in the prescription of vitamin D concentration measurements in clinical practice. It must be reminded that only the measurement of 25-hydroxyvitamin D (25(OH)D) concentration is indicated to evaluate vitamin D status. Furthermore, since vitamin D insufficiency is so common, since treatment is inexpensive and has a large safety margin, and since we already have much data suggesting that besides its classic effects on bone and mineral metabolism, vitamin D may potentially be helpful for the prevention/management of several diseases, perhaps should it be prescribed to everyone without prior testing? In our opinion, there are however groups of patients in whom estimation of vitamin D status is legitimate and may be recommended. This includes patients in whom a "reasonably" evidence-based target concentration (i.e., based on randomized clinical trials when possible) should be achieved and/or maintained such as patients with rickets/osteomalacia, osteoporosis, chronic kidney disease and kidney transplant recipients, malabsorption, primary hyperparathyroidism, granulomatous disease, and those receiving treatments potentially inducing bone loss. Other patients in whom vitamin D concentration may be measured are those with symptoms compatible with a severe vitamin D deficiency or excess persisting without explanation such as those with diffuse pain, or elderly individuals who fall, or those receiving treatments which modify vitamin D metabolism such as some anti-convulsants. Measurement of Vitamin D concentrations should also be part of any exploration of calcium/phosphorus metabolism which includes measurement of serum calcium, phosphate and PTH.

Real time identification of drug-induced liver injury (DILI) through daily screening of ALT results: a prospective pilot cohort study.

OBJECTIVE: Identification of drug-induced liver disease (DILI) is difficult, even among hospitalized patients. The aim of this pilot study was to assess the impact of a specific strategy for DILI screening. DESIGN: We prospectively compared the number of acute DILI cases identified in one week of a proactive strategy based on centralized elevated ALT values to those identified with a standard of care strategy for 24-week period based on referral cases to the hepatology unit. In the centralized strategy, a designated study biochemist identified patients with ALT greater than 3 times the upper limit of normal values (ULN) and notified the designated hepatologists, who then went to the patients' wards, analyzed the charts, and if necessary, interviewed the identified patients. During these two periods, patients with possible DILI were included after signing an informed consent in an ongoing European diagnostic study (SAFE-T consortium). RESULTS: During the 24-week period of the standard strategy, 12 (0.04%) patients out of a total of 28,145 were identified as having possible DILI, and 11 of these accepted to be included in the protocol. During the one-week proactive period, 7 patients out of a total of 1407 inpatients (0.498%) [odds ratio vs. standard = 12.1 (95% CI, 3.9-32.3); P<0.0001] were identified with possible DILI, and 5 were included in the protocol. CONCLUSION: A simple strategy based on the daily analysis of cases with ALT >3 ULN by designated biochemists and hepatologists identified 12 times more acute cases of drug-induced liver disease than the standard strategy. This pilot cohort is registered on the number AP-HP P110201/1/08-03-2011 and AFSSAPS B110346-70.

Nuclear, internuclear, and supranuclear ocular motor disorders.

In the brainstem, lateral and vertical eye movements are controlled by separate structures, the former mainly in the pons and the latter in the midbrain. The abducens nucleus (VI) in the pons controls all ipsilateral eye movements, i.e., ipsilateral saccades as well as the horizontal vestibulo-ocular reflex (VOR). This nucleus contains the abduction motoneurons, but also the internuclear neurons involved in adduction, passing through the contralateral medial longitudinal fasciculus (MLF) before relaying in the third-nerve nucleus in the midbrain. Lesions affecting the abducens nucleus result in complete ipsilateral eye movement paralysis, and lesions damaging the MLF result in internuclear ophthalmoplegia, whereas an association of these two lesions leads to the "one-and-a-half" syndrome. Ipsilateral saccades are controlled by the ipsilateral paramedian pontine reticular formation located close to the sixth nucleus, whereas the ipsilateral VOR is controlled by the contralateral medial vestibular nucleus. Vertical eye movements are controlled by the third- and fourth-nerve nuclei in the midbrain. A lesion unilaterally affecting the third-nerve nucleus results in an ipsilateral third-nerve paralysis and a contralateral upgaze paralysis because of the decussation of the superior rectus motoneurons, at the level of the third-nerve nuclei. Vertical saccades are controlled by the rostral interstitial nucleus of the MLF (riMLF) located close to the third-nerve nucleus. Downward and upward saccade paralysis results from bilateral riMLF damage whereas upgaze paralysis usually results from a unilateral lesion affecting the region of the posterior commissure, suggesting that the suprareticular control of these two types of vertical saccade is distinct.