Corticosteroid Responsive Tremor Syndrome Associated with Estrus in a Female Dog

Abstract

Background: Corticosteroid responsive tremor syndrome is an immune-mediated disorder that primarily affects small dogs aged 1 to 5 years. It is manifested by generalized tremors of high frequency and low amplitude, with involvement of head, trunk and limbs. The diagnosis is based on history, clinical signs and laboratory tests to rule out other conditions, as well as on the response to corticosteroid treatment. The aim of the present study was to report a case of a female dog with corticosteroid responsive tremor syndrome that began after estrus.Case: A 1-year-old, undetermined dog, weighing 4.9 kg, was attended at the Veterinary Hospital of Uberaba, with generalized tremors that impaired her walking and feeding. The picture had an acute onset, there was no history of intoxication, trauma, but the animal had an organophosphate-based collar. The bitch was not castrated and had been in heat for a month. In the clinical evaluation, it was observed that besides the tremors, the dog had hypermetria and hyperthermia. Suspected adverse reaction to organophosphorus or encephalitis. The collar was removed from the animal. Hemogram, serum biochemistry, analysis and culture of cerebrospinal fluid and test for distemper were performed. The hemogram was leukopenia due to lymphopenia. No alterations were observed in serum biochemistry CSF culture and the distemper test were negative. The CSF analyte revealed pleocytosis with predominantly lymphocytes, density and glucose increased slightly. The diagnosis of encephalitis of inflammatory etiology was established. Treatment with prednisone and diazepam was performed. Clinical signs improved after seven days of therapy. Approximately one and a half years after the initial clinical picture, the animal presented recurrence of the tremors associated with estrus again. The same treatment was instituted and the dog underwent ovariohysterectomy. There was no relapse of the clinical picture.Discussion: Syndromes characterized by generalized tremors were initially described in white-coated dogs. Later, they were observed in dogs of other pelts and in cats. It currently receives different nomenclatures such as idiopathic tremor syndrome or corticosteroid responsive tremor syndrome. The animal history of the present case allowed to exclude the main differential diagnoses of tremors caused by medication, intoxication and hypomyelination. The clinical manifestations of hyperthermia, hypermetry and generalized tremors of high frequency and low amplitude were also described by other authors in cases of corticosteroid responsive tremor syndrome. The age and size of the animal is consistent with previous reports that observed a higher frequency in animals from 1 to 5 years of age of small breed. The absence of alterations in the tests that indicated an infectious process allowed the diagnosis of inflammatory disease and the rapid improvement of the clinical signs after treatment with prednisone allowed to establish the diagnosis of the syndrome of the responsive corticosteroid tremor. Recurrence of the clinical picture again after estrus suggests that the variation of the hormones estrogen and progesterone during this phase may influence neuronal excitability as well as stimulate an inflammatory reaction. Further studies are needed to clarify the pathophysiology of corticosteroid responsive tremor syndrome and to investigate this hypothesis of sex hormone involvement in inflammation.