Sinonasal Aspergillosis in the dog causes a painful, destructive rhinitis. The most successful treatments are achieved using topical liquid antifungal medications delivered through catheters placed into the nares, or via trephination of the frontal sinuses. Recently the administration of clotrimazole cream following sinus trephination was reported with success rates similar to those reported for other topical treatments with suggested advantages of a shorter anaesthetic time, improved drug distribution within the sinuses, and increased drug contact time due to the "depot" effect of cream compared to solutions.

Various anatomical landmarks are suggested for trephination of the sinuses, most are along a horizontal line joining the supraorbital processes.

This study aimed to investigate any damage to local structures and the distribution of clotrimazole cream using two different trephination sites.

Twelve medium canine cadavers underwent an initial computerised tomography (CT) study of the head. The cadavers were randomly divided into two groups and the sinuses were trephined using a Steinman pin at a location along a line joining the supraorbital processes, midway from the midline of the skull to between the supraorbital process (group 1) or at a location along the same sagittal plane as in group 1 but positioned 1cm caudally (group 2). Approximately 25g of clotrimazole cream was instilled via the trephination hole into each frontal sinus and each cadaver head underwent a second CT scan.

The images were analysed for:

1.  Damage to local structures associated with trephination.

2.  Completeness of frontal sinus filling with clotrimazole cream.

Penetration of the supraorbital tissues (1 cadaver) and incomplete distribution of cream into the smaller rostral and medial sinuses (1 cadaver) occurred in group 1 cadavers, all group 2 cadavers had accurate sinus trephination and complete sinus filling.

Our results suggest there is better filling of the sinuses using the more caudal landmark, with less risk of damaging local structures during trephination.

There are several limitations to this study:

1.  A majority of cadavers used were Staffordshire bull terriers/cross breeds which may not reflect the breeds that typically develop sinonasal Aspergillosis.

2.  The cream may have different "liquid" properties at body temperature and thus distribute differently in live patients.

3.  The distribution of cream may be different in patients with sinonasal Aspergillosis where the resulting destructive rhinitis may aid distribution of the drug.