Investigation of the sensitivity and specificity of radiological signs for diagnosis of periapical infection of equine cheek teeth.

REASONS FOR PERFORMING STUDY: Radiography is commonly used for the diagnosis of equine cheek teeth (CT) infection but, to our knowledge, no study to date has evaluated the relative values of individual specific radiographic signs when making a diagnosis. OBJECTIVES: To investigate the sensitivity and specificity of individual radiographic signs identified from the literature for the diagnosis of CT apical infection using a retrospective case-control study. METHODS: Cropped radiographs taken using computed radiography of 41 apically infected CT and 41 control CT were independently blindly evaluated by 3 clinicians for the presence of 12 predetermined radiographic signs associated with CT apical infection. A final diagnosis of either noninfected or infected was made. Sensitivity and specificity were calculated for the presence or absence of each radiographic sign for each clinician. Uni- and multivariable conditional logistic regression were used to determine strength of association of the 12 radiographic signs with apical infection. RESULTS: Median sensitivity and specificity for the diagnosis of CT apical infection were 76 and 90%, respectively. Periapical sclerosis, clubbing of one or 2 roots, degree of clubbing and periapical halo formation had the highest sensitivities (73-90%), with moderate specificity (61-63%). Multivariable conditional logistic regression revealed that severity of periapical sclerosis and extensive periapical halo were strongly associated with CT apical infection. CONCLUSIONS: The presence of periapical sclerosis and formation of a periapical halo were strongly associated with CT apical infection. Computed radiography appears to have a higher sensitivity but similar specificity to previously published results using film radiography to detect CT apical infection. POTENTIAL RELEVANCE: These findings may aid practitioners when interpreting radiographs of equine CT as to the relative significance of their findings.

Histological and histochemical characterisation of the equine soft palate muscles.

REASONS FOR PERFORMING STUDY: Dysfunction of the muscles is implicated in the pathogenesis of intermittent dorsal displacement of the soft palate (DDSP) in exercising horses. The histological features of normal equine soft palate muscles have not been previously described. OBJECTIVE: To describe the histological and morphometric features of normal equine soft palate muscles. METHODS: The palatinus, palatopharyngeus, levator veli palatini and tensor veli palatini muscles of 6 Thoroughbred type horses were examined histologically and histochemically to assess their general morphology, fibre-type distribution and mean fibre diameter. RESULTS: The muscles of all 6 specimens showed very similar characteristics, including a low proportion of type 1 muscle fibres in the 4 different muscles examined, with the 3 muscles innervated by the pharyngeal branch of the vagus (i.e. palatopharyngeus, palatinus and levator veli palatini) having significantly fewer (P<0.005) type 1 muscle fibres compared to the tensor veli palatini. The mean fibre diameters were significantly (P<0.05) smaller in type 1 than type 2 fibres in all muscles except the palatinus. Considerable variability in mean fibre size diameter was evident in all muscles examined, with type 1 fibres in the levator veli palatini and rostral fasciculus of the palatopharyngeus and both fibre types in the caudal fasciculus of the palatopharyngeus having the most marked variation, with coefficients of variation >250 and the latter also having high levels of endomysial connective tissue. The palatinus had least variation in fibre size. CONCLUSION AND CLINICAL RELEVANCE: Morphological characterisation of the normal soft palate muscles may provide reference values for future comparative studies with samples obtained from horses with palatal dysfunction. The palatinus appears to be the best muscle to histologically examine for evidence of muscle abnormality.

Treatment of oromaxillary fistulae in nine standing horses (2002-2006).

REASONS FOR PERFORMING STUDY: There is minimal published information on equine oromaxillary fistulae that are unrelated to cheek teeth (CT) repulsion or on the conservative treatment of these atypical fistulae. OBJECTIVES: To report equine oromaxillary fistulae unrelated to CT extraction and describe their management in standing horses. METHODS: Case details of oromaxillary fistulae of atypical aetiology occurring at 2 referral centres between 2002-2006, including their treatment and response to treatment were examined. RESULTS: Nine cases of oromaxillary fistula were recorded, mainly in aged horses (median 22 years). Fistulae were associated with CT diastemata in 7 cases, fractured CT in one and a central defect in a worn CT in another. After removing food and exudate from the sinuses, 6 cases were treated successfully by filling the diastema or dental defect with polymethylmethacrylate (PMMA). Following dental extraction, the other 3 cases were treated successfully by use of PMMA alveolar packing. CONCLUSION: Older horses can spontaneously develop oromaxillary fistulae, usually secondary to CT diastemata. In the absence of apical infection, this disorder can usually be treated successfully in standing horses by treating the sinusitis and sealing the oral aspect of the diastema with PMMA. POTENTIAL RELEVANCE: Older horses with sinusitis should be assessed for the presence of CT diastemata and oromaxillary fistulae. If detected, these disorders can be treated successfully in the standing horse.