Canine tooth syndrome after frontoethmoidal osteoma surgery: a case report

Introduction: Canine tooth syndrome is a rare condition defined by the simultaneous presence of superior oblique palsy and Brown syndrome, resulting from pathological changes in the trochlear region. This syndrome can develop through various mechanisms, including dog bites, head trauma, infections, inflammation, and scarring. This report highlights its occurrence following sinus surgery for the first time. Methods: Medical and surgical records of an 18-year-old girl who presented with reading position diplopia after sinus surgery for right-side frontoethmoidal osteoma were retrospectively reviewed. Results: Strabismus examination revealed 8 Prism Diopter (PD) primary position hypertropia in the right eye that increased to 20 PD in downgaze. In the upward gaze to the left, the right eye showed 12 PD hypotropia with a positive forced duction test. The patient exhibited simultaneous signs of paresis and restriction of the right superior oblique muscle, consistent with type 7 of the Knapp classification. The patient declined strabismus surgery, and vertical diplopia was managed with prism spectacles. Long-term follow-up showed spontaneous resolution of superior oblique paresis leaving the patient with isolated Brown syndrome in the right eye. Discussion: Canine tooth syndrome can arise as a complication of frontoethmoidal sinus surgery due to excessive intraoperative manipulation of the superior and medial orbital wall, particularly in the trochlear region.