title: Lateral rectus superior compartment palsy.
abstract: OBJECTIVE
  To employ magnetic resonance imaging (MRI) to seek evidence of compartmental lateral rectus atrophy consistent with a lesion involving selective denervation of only 1 of the 2 neuromuscular compartments of the lateral rectus.
  
  
  METHODS
  Prospective observational case-control series.
  
  
  METHODS
  At a single institution, surface coil coronal MRI was obtained at 312 μm resolution in quasi-coronal planes 2 mm thick throughout the orbit in 20 normal volunteers and 18 patients with unilateral lateral rectus palsy fixated monocularly on a target placed in central gaze. Maximum cross sections and posterior volumes of the superior and inferior lateral rectus compartments were computed and correlated with clinical findings.
  
  
  RESULTS
  Twelve patients with lateral rectus palsy demonstrated symmetric, highly significant 40% reductions in maximum cross sections and 50% reductions in posterior volumes from normal for both compartments (P < 10(-6) for all comparisons). Six patients with lateral rectus palsy had similar significant but asymmetric reductions in those measures only for the superior compartment of the affected lateral rectus (P < 10(-4) for all comparisons), with insignificant 20%-30% reductions for the inferior compartment (P > 0.2 for all comparisons).
  
  
  CONCLUSIONS
  A subset of patients with clinical lateral rectus palsy may have palsy limited to the superior compartment. Paralytic esotropia may be caused by lateral rectus superior compartment palsy despite an intact lateral rectus inferior compartment. This finding is consistent with evidence supporting independent innervation of the 2 lateral rectus neuromuscular compartments.
authors: Department of Ophthalmology, University of California, Los Angeles, California; David Geffen Medical School, University of California, Los Angeles, California.
authors: Robert A
authors: RA
authors: Clark
authors: Department of Ophthalmology, University of California, Los Angeles, California; Department of Neurology, University of California, Los Angeles, California; Department of Neuroscience, University of California, Los Angeles, California; Biomedical Engineering Interdepartmental Programs, University of California, Los Angeles, California; David Geffen Medical School, University of California, Los Angeles, California. Electronic address: jld@ucla.edu.
authors: Joseph L
authors: JL
authors: Demer
mesh_terms: D000010:Abducens Nerve / Q000473:pathology*; D020434:Abducens Nerve Diseases / Q000175:diagnosis*; D000328:Adult; D000368:Aged; D001284:Atrophy; D016022:Case-Control Studies; D004948:Esotropia / Q000175:diagnosis; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009469:Neuromuscular Junction / Q000473:pathology; D009801:Oculomotor Muscles / Q000294:innervation*; D011446:Prospective Studies; D055815:Young Adult