Saccadic instabilities in albinism without nystagmus

Timms, Chris; Thompson, Dorothy; Russell‐Eggitt, Isabelle; Clement, Richard A.

doi:10.1007/s00221-006-0522-7

Cited by 5 publications

(3 citation statements)

References 23 publications

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“… 5 – 7 Even patients with albinism and no clinically detectable nystagmus were shown to have significant saccadic instabilities. 8 While there are a number of genes associated with different forms of albinism, the lack of pigmentation in these individuals leads to foveal hypoplasia and abnormal routing of the optic nerves. 9 , 10 In addition, it has been shown in animal models of albinism that the optic nerves contain a population of abnormal axons.…”

mentioning

confidence: 99%

Abnormally Small Neuromuscular Junctions in the Extraocular Muscles From Subjects With Idiopathic Nystagmus and Nystagmus Associated With Albinism

McLoon

Willoughby

Anderson

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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PurposeInfantile nystagmus syndrome (INS) is often associated with abnormalities of axonal outgrowth and connectivity. To determine if this manifests in extraocular muscle innervation, specimens from children with idiopathic INS or INS and albinism were examined and compared to normal age-matched control extraocular muscles.MethodsExtraocular muscles removed during normal surgery on children with idiopathic INS or INS and albinism were immunostained for neuromuscular junctions, myofiber type, the immature form of the acetylcholine receptor, and brain-derived neurotrophic factor (BDNF) and compared to age-matched controls.ResultsMuscles from both the idiopathic INS and INS and albinism groups had neuromuscular junctions that were 35% to 71% smaller based on myofiber area and myofiber perimeter than found in age-matched controls, and this was seen on both fast and slow myosin heavy chain isoform–expressing myofibers (all P < 0.015). Muscles from subjects with INS and albinism showed a 7-fold increase in neuromuscular junction numbers on fast myofibers expressing the immature gamma subunit of the acetylcholine receptor. The extraocular muscles from both INS subgroups showed a significant increase in the number and size of slow myofibers compared to age-matched controls. Brain-derived neurotrophic factor was expressed in control muscle but was virtually absent in the INS muscles.ConclusionsThese studies suggest that, relative to the final common pathway, INS is not the same between different patient etiologies. It should be possible to modulate these final common pathway abnormalities, via exogenous application of appropriate drugs, with the hope that this type of treatment may reduce the involuntary oscillatory movements in these children.

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confidence: 99%

Abnormally Small Neuromuscular Junctions in the Extraocular Muscles From Subjects With Idiopathic Nystagmus and Nystagmus Associated With Albinism

McLoon

Willoughby

Anderson

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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“…They are usually seen in association with cerebellar diseases that involve the fastigial nucleus or its outputs. They may be seen in patients with albinism [50] and, rarely, in patients with lesions in the pons in the vicinity of the omnipause neurons [51]. Based on the findings of recent modeling studies, it has been suggested that macrosaccadic oscillations arise due to a delay in the choking of saccadic drive signals by the fastigial nuclei of the cerebellum [9••].…”

Section: Macrosaccadic Oscillationsmentioning

confidence: 99%

Disorders of saccades

Thurtell¹,

Tomsak

Leigh³

2007

Curr Neurol Neurosci Rep

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Saccades are rapid eye movements that assist vision by pointing the fovea of the retina, which contains the highest density of photoreceptors, at features of interest in the visual environment. A great deal is now known about the properties and neurobiology of saccades in both health and disease states. They have consequently become a valuable diagnostic and research tool. In this review, we describe the common saccadic disorders and their causes. We also highlight recent insights into the pathophysiologic mechanisms underlying these disorders and discuss how these insights have helped increase our understanding of the saccadic system as a whole.

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“…Pattern appearance and flash stimuli have been typically used in most electrophysiological studies of chiasmal misrouting in albinism as prVEP responses can be confounded by nystagmus, which is present in the majority of people with albinism [16,21]. Although potentially under diagnosed, albinism without nystagmus is relatively rare, occurring in 6% to 11% of people with albinism [22,23]. Monocular hemifield (HF) prVEP stimulation is a sensitive way to identify hemisphere and chiasmal dysfunction in patients with steady central fixation [24,25].…”

Section: Introductionmentioning

confidence: 99%

Occipital Petalia and Albinism: A Study of Interhemispheric VEP Asymmetries in Albinism with No Nystagmus

Liasis

Handley

Nischal

2019

JCM

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The purpose of this study was to assess chiasmal misrouting in a cohort of children with albinism with no nystagmus using hemifield visual evoked potentials (VEP) measures. Methods: Monocular VEPs were recorded and analyzed from three electrodes (O1, Oz, and O2 referred to Fz) from 16 children with albinism without nystagmus. Pattern reversal (full field and hemifield stimulation), full field pattern appearance and flash stimuli were used to evoke VEPs for each eye. Results: The amplitude of the pattern reversal VEPs to stimulation of the hemifield corresponding to the crossing pathways were as expected significantly larger than those to the non-crossing in each eye ((right eye p = 0.000004), (left eye p = 0.001)). Pattern reversal VEPs recorded from the left hemisphere were also larger than those from the right and most evident when comparing the crossing pathways of each eye (p = 0.004). Conclusions: This study has demonstrated electrophysiological differences in visual pathway function of the left and right hemisphere in subjects with albinism like that previously described in controls. Nasal field stimulation activated crossing and non-crossing pathways in patients with albinism and as a result, nasal hemifield VEPs in albinism are less lateralized compared to what is found in normal subjects.

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Saccadic instabilities in albinism without nystagmus

Cited by 5 publications

References 23 publications

Abnormally Small Neuromuscular Junctions in the Extraocular Muscles From Subjects With Idiopathic Nystagmus and Nystagmus Associated With Albinism

Abnormally Small Neuromuscular Junctions in the Extraocular Muscles From Subjects With Idiopathic Nystagmus and Nystagmus Associated With Albinism

Disorders of saccades

Occipital Petalia and Albinism: A Study of Interhemispheric VEP Asymmetries in Albinism with No Nystagmus

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