Abstract

In November 2009, a bulging was identified on the left side of the neck in a fifteen-year-old male California sea lion (Zalophus californianus) by the training staff at Nausicaa. Though originally a reaction to a bite wound (even with no skin lesion apparent) was considered, the animal seemed to show no discomfort and the swelling showed no reduction by the use of anti-inflammatory drug (Carprofen 4 mg/BID – 5days). The swelling actually grew (or became more visible) to a 20 cm size mass that then stabilized. Other differential diagnoses were then advanced, among others the development of a cold abscess, an enlarged lymph node (infectious, tuberculosis) or the presence of a tumoral mass. Blood results, X-Rays and ultrasound of the mass were unremarkable. Because of the high prevalence of tuberculosis in Europe, though not really in California sea lions, enlargement of a lymph node was high on the list. However, the Nausicaa population, based on RT tests, seemed to be a sane population and had even been chosen to test the efficiency of skin test in pinnipeds in Europe. Eventually it was decided to perform a CT scan and a biopsy at the same time, which would necessitate only one anesthesia in the animal. The procedure occurred at Oncovet, a small animal diagnostic imaging reference clinic. Medetomidine (20 microgr/kg) and Zoletil (7 mg/kg) were used as premedication and isoflurane 0.8% as maintenance in the anesthesia protocol. Telebrix 35 (300 ml) was injected in the jugular on the R side with a 14G x 100 mm IV catheter as a contrast product. Neck and thoracic scannings were performed in dorsal decubitus. No mass was visible in the cervical region. A deformation of the second cervical vertebra, with embedment in C1, due to an ancient fracture by compression, was identified, with development of a bony cal. This deformation provokes a lateral deviation of the rachis at the level of C1–C2. Consequent to this result, no biopsy was done. The animal recovered from the procedure and still shows no symptoms or reduction of the mass. Comparable fractures are described in dogs as a consequence to a heavy shock (fight – car hit). The hypothesis is that the animal either fell hard on some rock or possibly had a heavy fight with some other animals in the group, being the lowest in the social ranking of this all castrated male colony. Ideally another CT scan should be performed to control the evolution of the fracture.