Frontal sinus depth at four landmarks in breeds of dog typically affected by sinonasal aspergillosis

The objective of this study was to assess whether the frontal sinuses in dogs with aspergillosis and of breeds typically affected by this condition were deeper at a more caudal location. CT scans of the head performed at the Small Animal Teaching Hospital, University of Liverpool, between April 2007 and March 2009 for dogs diagnosed with aspergillosis (group 1) and unaffected dogs of similar breeds (group 2) were selected for study. Sinus depth was measured at four standardised locations from reconstructed images of these CT scans. Data were compared for differences in sinus depth between groups and between landmarks. No significant difference was found between measurements within individual dogs or for each of the various landmarks between groups. Difference in depth of the sinuses between landmarks was significant (P<0.001). Sinus depth was significantly greater at the more caudal landmarks and was shallowest at the previously recommended landmark for sinus entry. In 54 per cent of dogs, the frontal sinus depth measured less than or equal to 2 cm at one or more of the landmarks. Sinus entry at the deepest point will reduce the risk of accidentally damaging underlying structures. This may be approximately 1 cm caudal, in breeds of dog that typically develop aspergillosis, to a previously suggested landmark.