title: Splitting of the extraocular horizontal rectus muscle in congenital cranial dysinnervation disorders.
abstract: OBJECTIVE
  To analyze the horizontal rectus extraocular muscles (EOMs) by orbital magnetic resonance imaging (MRI) in patients with congenital cranial dysinnervation disorders that arises from abnormal development of cranial nerve nuclei or their axonal connections.
  
  
  METHODS
  Case series, retrospective analysis.
  
  
  METHODS
  The morphology of the horizontal rectus EOMs was analyzed in orbital MRI on 4 patients with congenital oculomotor palsy, 26 with congenital superior oblique palsy, and five with Duane syndrome. Orbital imaging was performed by 1.5 tesla (T) and 3T MRI, and quasi-coronal and sagittal images perpendicular and parallel to the long axis of the orbit were obtained at slice thicknesses of 3 and 2 mm.
  
  
  RESULTS
  The horizontal rectus EOMs were split in 4 of the 35 patients (11%). Splitting was observed in 2 of the five patients (40%) with Duane syndrome, one of the 26 patients (4%) with congenital superior oblique palsy, and 1 of the 4 patients (25%) with oculomotor palsy, but in none of the 6 normal subjects and 12 patients with acquired cranial nerve palsy.
  
  
  CONCLUSIONS
  Since splitting of the horizontal rectus EOMs was noted in patients with congenital dysinnervation disorders, including Duane syndrome, Sevel's theory that the horizontal rectus EOMs develop from the superior and inferior mesodermal complexes is considered to be reasonable.
authors.affiliation: Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan. tankun@bj9.so-net.ne.jp
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Okanobu
authors.forename: Reika
authors.initials: R
authors.lastname: Kono
authors.forename: Koji
authors.initials: K
authors.lastname: Miyake
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohtsuki
mesh_terms: D000010:Abducens Nerve / Q000473:pathology*; D000328:Adult; D000368:Aged; D003389:Cranial Nerve Diseases / Q000151:congenital / Q000175:diagnosis*; D004370:Duane Retraction Syndrome / Q000175:diagnosis; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000294:innervation* / Q000473:pathology; D009802:Oculomotor Nerve / Q000473:pathology*; D015840:Oculomotor Nerve Diseases / Q000151:congenital / Q000175:diagnosis; D009915:Orbit; D012189:Retrospective Studies; D013285:Strabismus / Q000175:diagnosis; D014321:Trochlear Nerve / Q000473:pathology*; D020432:Trochlear Nerve Diseases / Q000175:diagnosis