Cranial Arterial Perfusion of the Tympanic Bullae Region in Llamas ( Lama glama ): Anatomic Features and Anomalies

The tympanic bulla of South American camelids is a unique multi-compartmental structure with an internal architecture resembling that of honeycomb. This unique configuration creates surgical challenges for the treatment of refractory otitis media cases in llamas (Lama glama). Surgical interventions for otitis media in the llama can result in life-threatening arterial haemorrhage. Surgery in lesser described species, such as camelids, can result in unanticipated complications when surgeons rely solely on anatomic extrapolation of similar species. Descriptive anatomy of llama vascular structures surrounding the tympanic bulla is lacking in the published record. To elucidate the arterial pattern of the tympanic bulla region of the llama with the intent of identifying unexpected arterial structures, 10 llama heads were dissected and all major arterial structures were identified, described and compared to computed tomography scans of contrast-enhanced arterial latex. Bilateral variations of the caudal auricular, superficial temporal and transverse facial arteries were found to result in an arterial trunk lying immediately adjacent to the lateral margin of the tympanic bulla in the llama. The arterial structure situated at the lateral margin of the tympanic bulla interferes with direct surgical access to the tympanic bulla by standard surgical techniques. These unique anatomic variations in the llama may be responsible for the risk of life-threatening haemorrhage during surgery that results in abandonment or failure of the procedure.