Computed tomographic features of the osseous structures of the external acoustic meatus, tympanic cavity, and tympanic bulla of llamas (Lama glama).
OBJECTIVE
To evaluate the osseous structures of the external acoustic meatus, tympanic cavity, and tympanic bulla of llamas (Lama glama) by use of computed tomography (CT) and establish measurement values for use in detection of abnormalities associated with the external or middle ear in llamas.


METHODS
10 adult llama heads without any evidence of ear disease.


METHODS
Heads of 10 healthy llamas euthanized by use of a captive bolt striking the dorsal aspect of the skull were collected. Transverse images of the heads were acquired with 1-mm slice thickness, and images were reconstructed in sagittal and dorsal planes. Measurements of the bony structures of the external and middle ear of each head were obtained.


RESULTS
The osseous external acoustic meatus curved ventrally as it tracked medially. Its narrowest portion was located at the level of the tympanic annulus. The tympanic bulla conformation differed widely from the bubble-shaped tympanic bulla in dogs and cats. The bulla was divided by the stylohyoid fossa into a larger caudolateral and a smaller caudomedial process; its interior had a honeycombed structure with pneumatized cells similar to the honeycombed appearance of the human mastoid process.


CONCLUSIONS
Results provided new information regarding the shape and dimensions of the osseous external and middle ear structures in adult llamas without ear disease. Specific landmarks for location of the external acoustic meatus, tympanic cavity, and tympanic bulla in relation to each other were identified. Knowledge of the CT appearance of normal structures will help clinicians to identify changes attributable to middle ear otitis, external ear canal stenosis, or congenital malformations of the ear in this species.
Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, USA.
Ismael
I
Concha-Albornoz
Susanne M
SM
Stieger-Vanegas
Christopher K
CK
Cebra
D019412:Anatomy, Cross-Sectional; D000818:Animals; D002161:Camelids, New World / Q000033:anatomy & histology*; D004424:Ear Canal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D004432:Ear, Middle / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005260:Female; D007091:Image Processing, Computer-Assisted; D008297:Male; D012016:Reference Values; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000662:veterinary