Animal Behavior Case of the Month Statement of the Problem A dog was examined because it was frequently chasing lights and shadows and spinning in circles. Signalment The patient was a 2-year-old 17-kg (37.4-lb) spayed female Border Collie. History The dog lived with 2 other dogs in a single-family house with a large yard. The owners (2 adults) had ad- opted the dog from a shelter at 4 months of age; the history prior to that time was unknown. The owners indicated that the dog knew a variety of commands but did not respond to them well. Since adoption, the dog would spin in both direc- tions equally and appeared to chase light and shadows. The behavior was more pronounced when there were loud noises present, if there was a heightened amount of activity surrounding the dog, and when it was out- doors in bright sunlight or indoors when rooms were brightly lit. This behavior would last between 15 and 20 minutes, after which the dog appeared normal. The episodes occurred once or twice daily for a total of ap- proximately 15 to 40 min/d. During the episodes, the dog did not respond to commands or other interrup- tions from the owners. The behavior had not been ob- served on regular outdoor walks in the early morning hours before sunrise. Within 1 week after adoption, the dog was evaluated by the primary care veterinarian because of the described behaviors. At that time, the referring veterinarian suspected hyperactivity or obsessive-compulsive disorder, and ami- triptyline hydrochloride (1 mg/kg [0.45 mg/lb], PO, q 12 h) was prescribed. Treatment with the medication was con- tinued for approximately 3 months with no improvement in the behavioral signs. Shortly after this visit, the dog was anesthetized for a full dental examination. Numerous re- tained deciduous teeth (which appeared to be functional and firmly attached) were identified, and the right and left maxillary premolar teeth were noted as missing. Results of a CBC and serum biochemical analysis at that time were within the respective reference ranges. Eight months prior to evaluation by the authors, the primary care veterinarian referred the owners to a veterinary neurologist because the dog’s light- and This report was submitted by Melissa J. Bain, DVM, MS, and Kathryn L. Good, DVM; from the Departments of Veterinary Medicine and Epidemiology (Bain) and Veterinary Surgery and Radiology (Good), School of Veterinary Medicine, University of California- Davis, Davis, CA 95616. Address correspondence to Dr. Bain (mjbain@ucdavis.edu). Vet Med Today: Animal Behavior Case of the Month In cooperation with shadow-chasing and spinning behaviors had persisted. There were no clinically important findings on full physical and neurologic examination except for light chasing and spinning in both directions in the exami- nation room. The neurologist recommended further diagnostic evaluation by means of MRI, examination of a CSF sample, and EEG, all of which the owners de- clined. Differential diagnoses made by the neurologist at that time included partial complex seizures or ob- sessive-compulsive disorder. Amitriptyline hydrochlo- ride treatment was discontinued, and administration of phenobarbital (5 mg/kg [2.3 mg/lb], q 24 h) was started on a trial basis. One month later, after consultation with the pri- mary care veterinarian, the dose of phenobarbital was increased to 8.1 mg/kg (3.7 mg/lb) every 24 hours. Two weeks after this change in treatment, potassium bromide solution (2 mL [concentration not reported], q 24 h) was added to the regimen. During this period, the dog had also received zonisamide (information on dosage and duration of treatment was not available) with no noted improvement. At the time of evaluation at the University of California-Davis Veterinary Medi- cal Teaching Hospital, the patient was receiving phe- nobarbital (2.8 mg/kg [1.3 mg/lb], q 12 h) and 1 mL of the potassium bromide solution every 24 hours. Dur- ing this time, the owners had not attempted behavior modification, but would calmly hold the dog in place when episodes were observed. Physical Examination Findings and Laboratory Results During the consultation, the dog was observed to periodically spin equally in both directions in response to noises from outside the room or if the owners talked loudly. During these episodes, the patient bit at the air while continually appearing to scan the ceiling area. On physical examination, it was noted that all maxillary and mandibular premolar teeth were missing, and the teeth that were present were much smaller than expected. All other general physical and neurologic ex- amination findings were unremarkable. To assess the patient’s vision, consultation with a veterinary ophthalmologist was requested. On oph- thalmic examination, both eyes were open and ap- peared comfortable with no overt photophobia appre- ciated. Direct and consensual pupillary light reflexes were present and considered normal in both eyes. There was no anisocoria. The patient had an appropri- ate menace response, and dazzle and palpebral reflexes were present in both eyes. Globe position and move- ments of both eyes were normal, and no facial asym- metry was evident. Tropicamide solution was admin- istered topically to each eye for pupil dilation. There JAVMA, Vol 247, No. 4, August 15, 2015
