title: Superior oblique muscle palsy after frontal sinus mini-trephine.
abstract: OBJECTIVE
  The aim of this study is to present a case of superior oblique muscle dysfunction after a frontal sinus mini-trephine.
  
  
  METHODS
  This is a case report of an 18-year-old woman where a mini-trephination approach and endoscope were used to open and marsupialize a symptomatic, opacified type IV cell within the left frontal sinus. After surgery, the patient developed a persisting diplopia; a left superior oblique muscle palsy was diagnosed. Nine cadaveric dissections of the trochlea were undertaken to clarify mechanisms for potential trochlear damage.
  
  
  RESULTS
  Cadaveric dissection reveals that the trochlea is more than a simple pulley; it is a complex structure in close proximity to the orbital rim. The superior oblique tendon telescopes and is surrounded by a vascular sheath that could be easily traumatized.
  
  
  CONCLUSIONS
  Damage to the trochlea could occur, as the periosteum is elevated from bone or during healing. Alternatively, prolonged traction on soft tissue near the trochlea could cause swelling of the vascular sheath, fibrosis, and hypomobility of the superior oblique tendon. Careful siting of the incision for external frontal sinus surgery as well as careful retraction of skin flaps and periosteal elevation are all techniques used, which should reduce the risk of damage to the trochlea.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Counties Manukau District Health Board, Auckland, New Zealand. jbartley@ihug.co.nz
authors.forename: Jim
authors.initials: J
authors.lastname: Bartley
authors.forename: Ngaire
authors.initials: N
authors.lastname: Eagleton
authors.forename: Paul
authors.initials: P
authors.lastname: Rosser
authors.forename: Saad
authors.initials: S
authors.lastname: Al-Ali
mesh_terms: D000293:Adolescent; D004724:Endoscopy / Q000009:adverse effects*; D005260:Female; D015522:Frontal Sinusitis / Q000601:surgery*; D006801:Humans; D015835:Ocular Motility Disorders / Q000209:etiology* / Q000601:surgery