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David G Hunter - One of the best experts on this subject based on the ideXlab platform.
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adjustable nasal transposition of split Lateral Rectus Muscle for third nerve palsy
JAMA Ophthalmology, 2014Co-Authors: Ankoor S Shah, Sanjay P Prabhu, Mohammad Ali A Sadiq, Iason S Mantagos, David G HunterAbstract:Importance Third nerve palsy causes disfiguring, incomitant strabismus with limited options for correction. Objective To evaluate the oculomotor outcomes, anatomical changes, and complications associated with adjustable nasal transposition of the split Lateral Rectus (LR) Muscle, a novel technique for managing strabismus associated with third nerve palsy. Design, Setting, and Participants Retrospective medical record review appraising outcomes of 6 consecutive patients with third nerve palsy who underwent adjustable nasal transposition of the split LR Muscle between 2010 and 2012 with follow-up of 5 to 25 months at a tertiary referral center. Intervention Adjustable nasal transposition of the split LR Muscle. Main Outcomes and Measures The primary outcome was postoperative horizontal and vertical alignment. Secondary outcomes were (1) appraising the utility of adjustable positioning, (2) demonstrating the resultant anatomical changes using magnetic resonance imaging, and (3) identifying associated complications. Results Four of 6 patients successfully underwent the procedure. Of these, 3 patients achieved orthotropia. Median preoperative horizontal deviation was 68 prism diopters of exotropia and median postoperative horizontal deviation was 0 prism diopters ( P = .04). Two patients had preoperative vertical misalignment that resolved with surgery. All 4 patients underwent intraoperative adjustment of LR positioning. Imaging demonstrated nasal redirection of each half of the LR Muscle around the posterior globe, avoiding contact with the optic nerve; the apex of the split sat posterior to the globe. One patient had transient choroidal effusion and undercorrection. Imaging revealed, in this case, the apex of the split in contact with the globe at an anteroLateral location, suggesting an inadequate posterior extent of the split. In 2 patients, the surgical procedure was not completed because of an inability to nasally transpose a previously operated-on LR Muscle. Conclusions and Relevance Adjustable nasal transposition of the split LR Muscle can achieve excellent oculomotor alignment in some cases of third nerve palsy. The adjustable modification allows optimization of horizontal and vertical alignment. Imaging confirms that the split LR Muscle tethers the globe, rotating it toward primary position. Case selection is critical because severe LR contracture, extensive scarring from prior strabismus surgery, or inadequate splitting of the LR Muscle may reduce the likelihood of success and increase the risk of sight-threatening complications. Considering this uncertainty, more experience is necessary before widespread adoption of this technique should be considered.
Stephen J Goldberg - One of the best experts on this subject based on the ideXlab platform.
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stimulation evoked eye movements with and without the Lateral Rectus Muscle pulley
Journal of Neurophysiology, 2003Co-Authors: Diana M Dimitrova, Mary S Shall, Stephen J GoldbergAbstract:Recent studies have suggested that extraocular Muscle (EOM) pulleys, composed of collagen, elastin, and smooth Muscle, are among the tissues surrounding the eye. High-resolution magnetic-resonance imaging appears to indicate that the pulleys serve to both constrain and alter the pulling paths of the EOMs. The active pulley hypothesis suggests that the orbital layer of the EOMs inserts on the pulley and serves to control it. Based on anatomical data, the active pulley hypothesis also suggests that the orbital layer does not rotate the eye within the orbit; this is done by the global layer of the Muscle. However, no physiological data exist to confirm this hypothesis. Here we used stimulation-evoked eye movements in anesthetized monkeys and cats before and after destruction of the Lateral Rectus Muscle pulley by removal of the Lateral bony orbit and adjacent orbital tissue. The absence of these structures resulted in increased Lateral, in the primate, and medial, in the cat, eye-movement amplitude and velocity. Vertical eye movements in the cat were not significantly affected. The results indicate that these increases, confined to horizontal eye-movement amplitude and velocity, may be attributed to passive properties within the orbit. In relation to the active pulley hypothesis, we could discern no clear impact (in terms of amplitude or velocity profile of the movements) of Lateral eye exposure that could be directly attributable to the active Lateral pulley system.
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short term effects of botulinum toxin on the Lateral Rectus Muscle of the cat
Experimental Brain Research, 2002Co-Authors: Diana M Dimitrova, Mary S Shall, Stephen J GoldbergAbstract:Botulinum toxin type A (BTX) is often used as an alternative to surgery for the treatment of strabismus and many other motor or cosmetic problems. Although numerous studies established BTX as a powerful transmission-blocking agent at the neuromuscular junction, no evaluation of extraocular Muscle (EOM) contractile properties after administration of BTX exists. Some anatomical studies on EOM fiber types suggested a long-term preferential effect of BTX on orbital layer, singly innervated Muscle fibers. In this study, we examined the short-term effects of BTX on the contractile properties of normal Lateral Rectus Muscle to determine the functional effect of BTX on Muscle-force output over time. Measurements of Muscle tension and the corresponding EMG evoked by stimulation of nerve VI were made hourly for up to 18 h following BTX administration. An intramuscular BTX injection of 2 U caused a dramatic decrease in maximum twitch and tetanic tension of the Muscle in response to different frequencies of stimulation. This suppression developed gradually over time, with a concomitant reduction of EMG amplitude. No significant changes in Muscle-speed-related characteristics (e.g., twitch contraction time, fusion frequency) were found. The results suggest a functional effect of BTX on all Muscle fiber types, although, with the dose used, we did not observe complete Muscle paralysis within the time of recording. The time course of Muscle tension suppression by BTX also was frequency dependent, with the lower stimulation frequencies being more affected, suggesting that implementation of higher frequencies could still produce adequate eye movements.
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extraocular motor unit and whole Muscle responses in the Lateral Rectus Muscle of the squirrel monkey
The Journal of Neuroscience, 1998Co-Authors: Stephen J Goldberg, Alex M Meredith, Mary S ShallAbstract:Because primate studies provide data for the current experimental models of the human oculomotor system, we investigated the relationship of Lateral Rectus Muscle motoneuron firing to Muscle unit contractile characteristics in the squirrel monkey. Also examined was the correlation of whole-Muscle contractile force with the degree of evoked eye displacement. A force transducer was used to record Lateral Rectus whole-Muscle or Muscle unit contraction in response to abducens whole-nerve stimulation or stimulation of single abducens motoneurons or axons. Horizontal eye displacement was recorded using a magnetic search coil. (1) Motor units could be categorized based on contraction speed (fusion frequency) and fatigue. (2) The kt value (change in motoneuronal firing necessary to increase motor unit force by 1.0 mg) of the units correlated with maximum tetanic tension. (3) There was some tendency for maximum tetanic tension of this unit population to separate into three groups. (4) At a constant frequency of 100 Hz, 95% of the motor units demonstrated significantly different force levels dependent on immediately previous stimulation history (hysteresis). (5) A mean force change of 0.32 gm/° and a mean frequency change of 4.7 Hz/° of eye displacement were observed in response to whole-nerve stimulation. These quantitative data provide the first contractile measures of primate extraocular motor units. Models of eye movement dynamics may need to consider the nonlinear transformations observed between stimulation rate and Muscle tension as well as the probability that as few as two to three motor units can deviate the eye 1°.
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summation of extraocular motor unit tensions in the Lateral Rectus Muscle of the cat
Muscle & Nerve, 1997Co-Authors: Stephen J Goldberg, Kristi Wilson, P Mary T S ShallAbstract:Contractile measures on 67 single Muscle units in the cat Lateral Rectus Muscle were made in response to motoneuron stimulation. Simultaneous activation of four to five additional units, using Muscle nerve stimulation, allowed an examination of unit force summation. Linear force addition was found in 73% of the units, while 25% added only about half of their twitch force to the twitch force of the nerve-activated units. “Nonadditive” units had significantly weaker twitch tensions than the units which added linearly. Lengthening or shortening the whole Muscle, from maximal isometric settings, reduced whole Muscle twitch tension as well as Muscle unit tension. Injury to the Lateral Rectus Muscle did not significantly alter whole Muscle tension. These findings suggest that the known serial and branching arrangement of these Muscle fibers, as well as the complex interfiber matrix, may help explain the force reduction in some Muscle units and the whole Muscle's resistance to insult. © 1997 John Wiley & Sons, Inc. Muscle Nerve20: 1229–1235, 1997
Ankoor S Shah - One of the best experts on this subject based on the ideXlab platform.
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complication and management of optic nerve edema resulting from nasal transposition of the split Lateral Rectus Muscle
Journal of Pediatric Ophthalmology & Strabismus, 2021Co-Authors: Sabine S Khan, Ankoor S Shah, Linda R Dagi, Norman B Medow, Ilana B Friedman, Jamie B RosenbergAbstract:A 9-year-old boy with partial third nerve palsy underwent medial transposition of the left Lateral Rectus Muscle and left inferior oblique myectomy. He developed optic nerve compression, which improved after a superior oblique tenotomy. A primary superior oblique tenotomy or a maximum Lateral Rectus Muscle split may help avoid this complication. [J Pediatr Ophthalmol Strabismus. 2021;58(3):e12-e15.].
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adjustable nasal transposition of split Lateral Rectus Muscle for third nerve palsy
JAMA Ophthalmology, 2014Co-Authors: Ankoor S Shah, Sanjay P Prabhu, Mohammad Ali A Sadiq, Iason S Mantagos, David G HunterAbstract:Importance Third nerve palsy causes disfiguring, incomitant strabismus with limited options for correction. Objective To evaluate the oculomotor outcomes, anatomical changes, and complications associated with adjustable nasal transposition of the split Lateral Rectus (LR) Muscle, a novel technique for managing strabismus associated with third nerve palsy. Design, Setting, and Participants Retrospective medical record review appraising outcomes of 6 consecutive patients with third nerve palsy who underwent adjustable nasal transposition of the split LR Muscle between 2010 and 2012 with follow-up of 5 to 25 months at a tertiary referral center. Intervention Adjustable nasal transposition of the split LR Muscle. Main Outcomes and Measures The primary outcome was postoperative horizontal and vertical alignment. Secondary outcomes were (1) appraising the utility of adjustable positioning, (2) demonstrating the resultant anatomical changes using magnetic resonance imaging, and (3) identifying associated complications. Results Four of 6 patients successfully underwent the procedure. Of these, 3 patients achieved orthotropia. Median preoperative horizontal deviation was 68 prism diopters of exotropia and median postoperative horizontal deviation was 0 prism diopters ( P = .04). Two patients had preoperative vertical misalignment that resolved with surgery. All 4 patients underwent intraoperative adjustment of LR positioning. Imaging demonstrated nasal redirection of each half of the LR Muscle around the posterior globe, avoiding contact with the optic nerve; the apex of the split sat posterior to the globe. One patient had transient choroidal effusion and undercorrection. Imaging revealed, in this case, the apex of the split in contact with the globe at an anteroLateral location, suggesting an inadequate posterior extent of the split. In 2 patients, the surgical procedure was not completed because of an inability to nasally transpose a previously operated-on LR Muscle. Conclusions and Relevance Adjustable nasal transposition of the split LR Muscle can achieve excellent oculomotor alignment in some cases of third nerve palsy. The adjustable modification allows optimization of horizontal and vertical alignment. Imaging confirms that the split LR Muscle tethers the globe, rotating it toward primary position. Case selection is critical because severe LR contracture, extensive scarring from prior strabismus surgery, or inadequate splitting of the LR Muscle may reduce the likelihood of success and increase the risk of sight-threatening complications. Considering this uncertainty, more experience is necessary before widespread adoption of this technique should be considered.
Joseph L Demer - One of the best experts on this subject based on the ideXlab platform.
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functional anatomy of human extraocular Muscles during fusional divergence
Journal of Neurophysiology, 2018Co-Authors: Joseph L Demer, Robert A ClarkAbstract:Magnetic resonance imaging shows that the Lateral Rectus Muscle must overcome continued contraction by its opponent the medial Rectus when humans diverge their visual axes to achieve single, binocu...
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compartmentalized innervation of primate Lateral Rectus Muscle
Investigative Ophthalmology & Visual Science, 2010Co-Authors: Michelle Y Peng, Vadims Poukens, Roberta Costa, Lawrence Yoo, Lawrence Tychsen, Joseph L DemerAbstract:Muscles need not be controlled as if they were monolithic structures. Many human skeletal Muscles consist of multiple neuromuscular compartments in which different muscular regions are controlled by different populations of motor neurons.1–3 For example, the human cricothyroid Muscle has three distinct bellies controlled by separate motor nerve branches apparently serving different motor tasks.4 Numerous skeletal Muscles are compartmentally organized and controlled by somatotopically organized motor neuron pools.5 Compartmentalization adds diversity to the functional repertoire of a Muscle. Extraocular Muscle (EOM) fibers and motor neurons are known to exist in superabundance relative to the requirements of the conventionally recognized mechanisms of eye movements.6,7 It is theoretically plausible that individual EOMs would have more than one function. The active pulley hypothesis (APH) proposes that the orbital layers (OLs) of the EOMs shift connective tissue structures to influence EOM pulling directions, whereas the global layers (GLs) directly exert oculorotary torque. Aside from the APH, there is little knowledge or speculation about possible compartmentalization in EOMs. The Lateral Rectus (LR) is the most obvious candidate Rectus EOM for compartmentalization. Clues are already available that the LR may be a compartmentalized EOM. The LR has traditionally been recognized to have a dual-headed origin described as either dividing the superior orbital fissure into inferior and superior compartments8 or arising as two distinct slips at the common tendinous ring.9 Classic embryology maintained that the LR arises from what were originally considered two different myotomes.10,11 Modern embryology recognizes that the avian LR Muscle arises from somitomeres 4 and 512,13 and that the abducens nerve (CN6) arises from both rhombomeres 5 and 6.12 More recently, longitudinal splitting of the human LR has been observed by magnetic resonance imaging (MRI) in congenital cranial dysinnervation disorders, including congenital fibrosis of the extraocular Muscles type 1 (CFEOM1),14 Duane syndrome,15–17 congenital trochlear palsy,18 and congenital oculomotor palsy.18 In domestic mammals, CN6 innervates the LR after giving off branches to the retractor bulbi (RB) Muscle.19 The accessory Lateral Rectus Muscle (ALR), an EOM seen consistently in monkeys but normally absent in humans,20 is believed to be the vestigial homologue of the RB21 and has been reported once in a human with congenital third nerve palsy.22 The ALR shares an origin with the LR.23 In the cat, 18% of abducens nucleus neurons innervating the ALR also innervate the LR.19 These observations suggest that the ontogenic role of CN6 is to innervate multiple functional EOM units. Innervation of the LR may often be grossly bifid in humans. Autopsy evidence indicates an 8% to 15% rate of uniLateral or biLateral duplication of CN6 in humans,24–27 with splitting sometimes as proximal as the pons itself.27 Split innervation from CN6 to the RB and LR in nonhuman mammals, combined with the dual origin of the LR and frequent duplication of CN6 in humans, supports the idea that CN6 may contain topographically distinct branches that may innervate separate LR functional compartments. We therefore hypothesized that that the primate LR may contain two functional zones, controllable by topographically segregated innervation that may confer some degree of independence. We sought evidence to support this proposition by re-examining peripheral and intramuscular LR innervation in human and nonhuman primates.
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heavy eye syndrome in the absence of high myopia a connective tissue degeneration in elderly strabismic patients
Journal of Aapos, 2009Co-Authors: Tina Rutar, Joseph L DemerAbstract:Purpose In axial high myopes with “heavy eye” syndrome, orbital MRI can be use to demonstrate degeneration of the Lateral Rectus–superior Rectus (LR-SR) band, with the result that the Lateral Rectus Muscle slips inferiorly and causes esotropia and hypotropia. We investigated whether this degeneration might also cause strabismus in nonmyopic elderly patients. Methods Three elderly patients with strabismus, 3 strabismic high myopes, and 12 orthotropic elderly subjects underwent ophthalmic examinations and orbital MRI. The Lateral Rectus Muscle position was determined relative to globe center from quasicoronal images and correlated with LR-SR band structure. MRI scans were compared with histology of 4 cadaveric orbits ranging in age from 17 months to 93 years. Results Two strabismic patients exhibited hypotropia; one exhibited esotropia. Mean axial length was 24.1 ± 0.8 mm (mean ± SD), compared with 31.6 ± 1.4 mm for myopes. The Lateral Rectus Muscle position of elderly strabismic subjects averaged 4.6 ± 1.7 mm inferior to globe center, which was significantly lower than that of orthotropic elderly subjects (2.1 ± 1.9 mm; p = 0.01) and similar to that of high myopes (5.1 ± 3.2 mm). On MRI scanning, 100% of strabismic elderly orbits, 67% of strabismic myopic orbits, and 12.5% of control elderly orbits showed LR-SR band thinning, discontinuity, or displacement. LR-SR band degeneration was present histologically only in older cadavers. Conclusions Age-related LR-SR band degeneration permits the Lateral Rectus Muscle to slip inferiorly in elderly nonmyopes, a mechanism of strabismus similar to myopic “heavy eye” syndrome. Imaging may assist in diagnosing this mechanical cause of age-related strabismus.
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duane s syndrome with compressive denervation of the Lateral Rectus Muscle
American Journal of Ophthalmology, 2001Co-Authors: Mark Silverberg, Joseph L DemerAbstract:Abstract PURPOSE: To describe an unusual case of Duane’s syndrome. METHODS: Individual case report. RESULTS: A skull base meningioma was discovered in a woman with Duane’s syndrome who presented with recurrent, large-angle esotropia and uncharacteristic atrophy of the Lateral Rectus Muscle on magnetic resonance image (MRI) scan. CONCLUSION: Neuroimaging may be useful in unusual cases of Duane’s syndrome.
Birsen Gokyigit - One of the best experts on this subject based on the ideXlab platform.
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effect of Lateral Rectus Muscle resection on abduction in duane retraction syndrome type 1
International Ophthalmology, 2021Co-Authors: Selcen Celik, Asli Inal, Ebru Demet Aygit, Osman Bulut Ocak, Birsen GokyigitAbstract:To assess the effect of Lateral Rectus Muscle resection on abduction in Duane retraction syndrome (DRS) type 1. The medical records of patients with DRS type 1 were reviewed retrospectively. Fifteen patients who underwent Lateral Rectus resection were included. Prism and cover test and the Krimsky test were used to detect deviations. Ocular ductions, abnormal head position (AHP), and globe retraction were recorded. Nine (60.0%) patients were female. The mean age was 13.1 ± 2.3 (range, 2–34) years. Left eyes were included in ten (66.7%) patients. Mean follow-up time was 37.6 ± 16.6 (range, 6–70) months. All patients had AHP, 13 patients had mild globe retraction, and 2 patients had no globe retraction preoperatively. Mean Lateral Rectus resection was 3.1 ± 0.7 (range, 2.0–4.5) mm, and the mean medial Rectus recession was 4.4 ± 0.6 (range, 3.0–5.0) mm. The mean preoperative deviation decreased from 23.3 ± 6.9 (range, 14–35) prism diopters (pd) to 2.2 ± 4.1 (range, 0–10) pd at near, and from 23.6 ± 7.1 (range, 14–35) pd to 1.8 ± 3.5 (range, 0–10) pd at distance, at 6 months postoperatively (p = 0.01). The mean limitation in abduction decreased from − 3.2 ± 0.9 to − 1.3 ± 1.1 postoperatively (p < 0.001). AHP resolved in all patients. There was not a limitation in adduction or a worsening of globe retraction in any patient. Lateral Rectus resection can be used to improve abduction in patients with DRS type 1 who have mild globe retraction. We assume that this procedure has no worsening effect on globe retraction in appropriate cases.
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medial transposition of a split Lateral Rectus Muscle for complete oculomotor nerve palsy
Journal of Aapos, 2013Co-Authors: Birsen Gokyigit, Serpil Akar, Banu Satana, Ahmet Demirok, Omer YilmazAbstract:Purpose To evaluate the effect on ocular alignment of Y splitting the Lateral Rectus Muscle and then reattaching the 2 ends near the medial Rectus Muscle insertion in patients with complete oculomotor nerve palsy. Methods All eyes with oculomotor nerve palsy treated between May 2008 and February 2010 with Y splitting and transposition of the Lateral Rectus Muscle to the medial Rectus Muscle were prospectively studied. In this procedure, the Lateral Rectus Muscle was split: the upper half was transposed to the superior border and the lower half to the inferior border of the medial Rectus insertion. For the Muscles that had lost the ability to stretch and strain due to fibrosis, a hang-back technique was used. In some patients, the medial Rectus Muscle of the same eye was subsequently strengthened or the Lateral Rectus Muscle of the fellow eye was recessed. Final deviation from 0 Δ to 10 Δ was considered a successful result. Results A total of 10 patients were included. Patients had a preoperative horizontal deviation >45 Δ (range, 45 Δ -90 Δ ). Of the 10 patients, 5 attained stable results following surgery, and 5 with postoperative undercorrection between 20 Δ and 30 Δ required further surgeries. Postoperatively, 2 patients improved their sensorial status in a very limited range of gaze and 2 patients had symptomatic diplopia. Conclusions Acceptable aesthetic results can be achieved in the treatment of complete oculomotor nerve palsy with the transposition of the split Lateral Rectus Muscle to the medial Rectus Muscle area.
