Extraocular Muscles in Patients With Infantile Nystagmus

Berg, Katherine; Hunter, David G.; Bothun, Erick D.; Antunes-Foschini, Rosália; McLoon, Linda K.

doi:10.1001/archophthalmol.2011.381

Cited by 16 publications

(12 citation statements)

References 21 publications

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“…3 C). As shown previously for specimens from subjects with idiopathic INS, 22 the EOM from subjects with INS associated with albinism also had significantly reduced nerve fiber density compared to control values, at 0.39 ± 0.1% compared to control values of 6.09 ± 1.06% ( Fig. 3 C).…”

Section: Resultssupporting

confidence: 84%

“…In a previous study, we demonstrated that the extraocular muscles (EOMs) from idiopathic INS patients contained centrally nucleated myofibers, a sign of denervation/reinnervation, as well as decreased density of innervating nerve fibers and neuromuscular junctions (NMJ). 22 Our goal in the present study was to determine if similar findings would be seen in the EOMs from patients with albinism and INS. Our original study of EOM surgical waste specimens obtained from subjects with idiopathic INS at the time of surgery suggested changes that could reflect either retention of immature NMJ properties or a process of escalated remodeling of the NMJ.…”

mentioning

confidence: 76%

“…33 In our earlier study we showed that in the EOM from subjects with idiopathic INS there was a significant reduction in the density of NMJs that correlated with decreased density of innervating nerve fibers. 22 These studies suggest that there may be a common mechanism in these patient populations that affects the normal patterning of innervation.…”

Section: Discussionmentioning

confidence: 97%

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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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Section: Resultssupporting

confidence: 84%

mentioning

confidence: 76%

Section: Discussionmentioning

confidence: 97%

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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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“…When the monkeys were examined a few weeks later, it was found that the muscle that had been surgically repositioned had added sarcomeres, implying that the resting length of the muscle had changed to account for the muscle stretch and restricted motility imposed upon it by surgery (Scott 1994). Other studies have documented ( a ) hypertrophic or hypotrophic muscles and mislocalization of muscle pulleys in some forms of human strabismus, ( b ) increases in satellite cell activity in rabbit EOM following resection, ( c ) alterations in neuromuscular junction density following treatment of EOM with botulinum toxin, and ( d ) changes in muscle fiber characteristics and neuromuscular junction density in patients with nystagmus, all of which suggest that muscle remodeling can influence the final state of strabismus and eye movement disruption (Berg et al 2012, Christiansen & McLoon 2006, Harrison et al 2007, Oh et al 2002, Schoeff et al 2013). However, an examination of the EOM in monkeys with prism-reared strabismus and no prior surgical treatment found no gross changes in muscle or muscle pulleys (Narasimhan et al 2007), although cellular characteristics of the muscle and contractility were not measured.…”

Section: What Factors Govern Eye Misalignment and Disruption Of Eymentioning

confidence: 99%

Strabismus and the Oculomotor System: Insights from Macaque Models

Das

2016

Annu. Rev. Vis. Sci.

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Disrupting binocular vision in infancy leads to strabismus and oftentimes to a variety of associated visual sensory deficits and oculomotor abnormalities. Investigation of this disorder has been aided by the development of various animal models, each of which has advantages and disadvantages. In comparison to studies of binocular visual responses in cortical structures, investigations of neural oculomotor structures that mediate the misalignment and abnormalities of eye movements have been more recent, and these studies have shown that different brain areas are intimately involved in driving several aspects of the strabismic condition, including horizontal misalignment, dissociated deviations, A and V patterns of strabismus, disconjugate eye movements, nystagmus, and fixation switch. The responses of cells in visual and oculomotor areas that potentially drive the sensory deficits and also eye alignment and eye movement abnormalities follow a general theme of disrupted calibration, lower sensitivity, and poorer specificity compared with the normally developed visual oculomotor system.

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“…Biopsy of ocular muscle from nystagmus surgery patients has shown that there are more centrally nucleated muscle fibers with greater variation between them than is seen in normal extraocular muscle tissue. 28 Unique proprioceptors are found within the extraocular muscles and appear to be altered in INS compared to normal. It is possible that proprioceptor function changes after muscle surgery for nystagmus.…”

Section: Mechanisms For Development Of Nystagmusmentioning

confidence: 99%

Nystagmus in pediatric patients: interventions and patient-focused perspectives

Penix¹,

Swanson²,

DeCarlo³

2015

OPTH

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Nystagmus refers to involuntary, typically conjugate, often rhythmic oscillations of the eyes. The most common cause of nystagmus in children is infantile nystagmus syndrome (INS). INS presents within the first few months of life and is sometimes accompanied by an ocular condition associated with sensory impairment. Because this condition affects a person throughout life, it is important to understand the options available to manage it. This review focuses on the underlying nystagmus etiology, psychosocial and functional effects of nystagmus, as well as current principles of management, including optical, pharmacological, surgical, and rehabilitative options. Currently, the neural mechanisms underlying INS are not fully understood. Treatment options are designed to increase foveation duration or correct anomalous head postures; however, evidence is limited to mainly pre- and post-study designs with few objective comparisons of treatment strategies. Management of INS should be individualized. The decision on which treatment is best suited for a particular patient lies with the patient and his/her physician.

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Extraocular Muscles in Patients With Infantile Nystagmus

Cited by 16 publications

References 21 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

Strabismus and the Oculomotor System: Insights from Macaque Models

Nystagmus in pediatric patients: interventions and patient-focused perspectives

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Extraocular Muscles in Patients With Infantile Nystagmus

Cited by 16 publications

References 21 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

Strabismus and the Oculomotor System: Insights from Macaque Models

Nystagmus in pediatric patients: interventions and&nbsp;patient-focused perspectives

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Nystagmus in pediatric patients: interventions and patient-focused perspectives