Intramuscular Innervation of Primate Extraocular Muscles: Unique Compartmentalization in Horizontal Recti

Costa, Roberta; Kung, Jennifer; Poukens, Vadims; Yoo, Lawrence; Tychsen, Lawrence; Demer, Joseph L.

doi:10.1167/iovs.10-6651

Cited by 68 publications

(68 citation statements)

References 33 publications

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“…The inescapable conclusion that horizontal rectus EOMs must generate ocular torsion then motivated discovery of compartmentalization as a plausible mechanism expanding the diversity of EOM actions. 10,11 Compartmentalization has proven to be a general feature of ocular motility, and is not limited to the horizontal rectus EOMs.…”

Section: Mysteries Of Ocular Motor Effectorsmentioning

confidence: 99%

“…Motor nerves innervating horizontal rectus EOMs bifurcate into about equal regionally segregated intramuscular arborizations (Figure 1). 11 This was first suspected in LR because it has been thought to have a dual origin 13 arising from separate embryonic progenitors. 14 Longitudinal LR splitting can be observed by magnetic imaging resonance (MRI) in congenital cranial dysinnervation disorders, including congenital fibrosis, 15 Duane syndrome, 16 and congenital oculomotor palsy.…”

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

“…18 The medial rectus (MR) motor nerve also bifurcates and arborizes into nonoverlapping superior and inferior compartments of roughly equal size. 11 The feline inferior oblique is innervated by distinct medial and lateral branches that generate different contractile responses. 20 In human and monkey, the inferior oblique is also innervated in compartmental fashion by two separate motor nerve trunks.…”

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

“…21 Possible compartmentalization is less clear for the inferior rectus, which has a selective lateral trunk that overlaps diffuse arborization of another trunk throughout the entire EOM. 11 This implies that selective neural control of the lateral inferior rectus might be possible. However, current efforts at tracing have not identified selective intramuscular motor nerve arborization in superior rectus.…”

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

“…However, current efforts at tracing have not identified selective intramuscular motor nerve arborization in superior rectus. 11 The superior oblique (SO) of humans and monkeys is innervated in non-overlapping medial and lateral compartments by two divisions of the trochlear nerve 21,22 ( Figure 2). The border between compartments is slightly oblique to the major axis of the elliptical SO cross-section, and thus also oblique to the border found in horizontal rectus EOMs.…”

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

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Compartmentalization of extraocular muscle function

Demer

2014

Eye

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Ocular motor diversity exceeds capabilities of only six extraocular muscles (EOMs), but this deficiency is overcome by the plethora of fibers within individual EOMs surpassing requirements of homogeneous actuators. This paper reviews emerging evidence that regions of individual EOMs can be differentially innervated to exert independent oculorotary torques, broadening the oculomotor repertoire, and potentially explaining diverse strabismus pathophysiology. Parallel structure characterizes EOM and tendon fibers, with little transverse coupling of experimentally imposed or actively generated tension. This arrangement enables arbitrary groupings of tendon and muscle fibers to act relatively independently. Coordinated force generation among EOM fibers occurs only upon potentially mutable coordination of innervational commands, whose central basis is suggested by preliminary findings of apparent compartmental segregation of abducens motor neuron pools. Humans, monkeys, and other mammals demonstrate separate, nonoverlapping intramuscular nerve arborizations in the superior vs inferior compartments of the medial rectus (MR) and lateral rectus (LR) EOMs that could apply force at the superior vs inferior portions of scleral insertions, and in the medial vs lateral compartments of the superior oblique that act at the equatorial vs posterior scleral insertions that might preferentially implement incycloduction vs infraduction. Magnetic resonance imaging of the MR during several physiological ocular motor behaviors indicates differential compartmental function. Differential compartmental pathology can influence clinical strabismus. Partial abducens palsy commonly affects the superior LR compartment more than the inferior, inducing vertical strabismus that might erroneously be attributed to cyclovertical EOM pathology. Surgery may selectively manipulate EOM compartments.

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Section: Mysteries Of Ocular Motor Effectorsmentioning

confidence: 99%

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

Section: Anatomic Evidence For Eom Compartmentalizationmentioning

confidence: 99%

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Compartmentalization of extraocular muscle function

Demer

2014

Eye

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Insertion Slanting Strabismus Surgical Procedures

Kushner

2011

Arch Ophthalmol

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nsertion slanting recessions or biased resections have been reported to be useful for treating A-and V-pattern strabismus, convergence insufficiency, and convergence excess esotropia. Paradoxically, good results have been reported with methods that are opposite in nature. For example, some researchers would recess the medial rectus muscles and slant the superior pole of each muscle back farther than the inferior pole (Simonsz/von Graefe method) for a V-pattern esotropia, and others would slant the inferior poles back farther (Bietti method). The Simonsz/von Graefe method seems to be based on sound concepts of oculomotor mechanics. The Bietti method has been justified based on a misquoting and misinterpretation of previous work by Alan Scott, MD. Probably neither method contributes substantially to the outcome of strabismus surgery because sarcomere remodeling should rapidly negate the effect of the slanting. Most likely it is the recession or resection itself that affects the outcome.

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On Insertion Slanting Strabismus Surgery—Reply

Kushner¹

2012

Arch Ophthalmol

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Intramuscular Innervation of Primate Extraocular Muscles: Unique Compartmentalization in Horizontal Recti

Cited by 68 publications

References 33 publications

Compartmentalization of extraocular muscle function

Compartmentalization of extraocular muscle function

Insertion Slanting Strabismus Surgical Procedures

On Insertion Slanting Strabismus Surgery—Reply

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