Persistent marked cerebrospinal fluid eosinophilia in a dog with primary central nervous system histiocytic sarcoma.

A 6-year-old female spayed Jack Russell Terrier was evaluated for episodic seizure-like activity and intermittent obtundation over the previous 3 weeks. Magnetic resonance imaging (MRI) of the brain revealed mild generalized dilation of the ventricular system with periventricular edema. A focal area of mildly increased lepto- and pachymeningeal contrast uptake in the region of the right parietal and occipital lobes was observed. Analysis of cerebrospinal fluid (CSF) revealed marked mixed pleocytosis with 20% eosinophils and no atypical cells or microorganisms. The dog transiently improved with prednisolone for suspected eosinophilic meningoencephalitis/meningoencephalomyelitis of unknown origin (MUO) but worsened over the following 5 months. Brain MRI and CSF sampling were repeated. Additional multifocal lesions were evident in the brainstem and cerebellum. On CSF analysis, the eosinophilic pleocytosis and increased total protein persisted. The clinical signs progressed despite treatment, and the patient was euthanized 6 weeks later. A post-mortem examination was performed. Histopathology and immunohistochemistry revealed a multifocal neoplastic proliferation of cells in the brain, diffusely and strongly positive for ionized calcium-binding adapter molecule (Iba-1) and negative for AE1/AE3 pan-cytokeratin and glial-fibrillar-acid-protein (GFAP) immunostaining, consistent with a diagnosis of histiocytic sarcoma (HS). No other organic lesions were found; therefore, the neoplasm was considered a primary HS of the central nervous system (CNS). This case report stresses the importance of considering primary CNS HS in the differential diagnosis of dogs with marked CSF eosinophilia, even in the absence of atypical cells on cytologic examination.

Prevalence and clinical characteristics of phenobarbitone-associated adverse effects in epileptic cats.

OBJECTIVES: The study objective was to investigate the prevalence and clinical characteristics of phenobarbitone-associated adverse effects in epileptic cats. METHODS: The medical records of two veterinary referral clinics from 2007 to 2017 were searched for cats fulfilling the inclusion criteria of a diagnosis of epilepsy, treatment with phenobarbitone and available follow-up information on the occurrence of adverse effects. Follow-up information was obtained from the medical records of the primary veterinarian and referral institutions and a questionnaire completed by the cats' owners. RESULTS: Seventy-seven cats met the inclusion criteria. Fifty-eight were affected by idiopathic epilepsy and 19 by structural epilepsy. One or more of the following adverse effects were reported in 47% of the cats: sedation (89%); ataxia (53%); polyphagia (22%); polydipsia (6%); polyuria (6%); and anorexia (6%). Logistic regression analyses revealed significant associations between adverse effect occurrence and both phenobarbitone starting dosage and administration of a second antiepileptic drug (AED). For each 1 mg/kg q12h increment of phenobarbitone, the likelihood of adverse effects increased 3.1 times. When a second AED was used, the likelihood of adverse effects increased 3.2 times. No association was identified between epilepsy aetiology and adverse effect occurrence. An idiosyncratic adverse effect, characterised by severe neutropenia and granulocytic hypoplasia, was diagnosed in one cat. This resolved following phenobarbitone discontinuation. CONCLUSIONS AND RELEVANCE: The prevalence of phenobarbitone-associated adverse effects was 47%. Sedation and ataxia were most common. These are type A adverse effects and are predictable from phenobarbitone's known pharmacological properties. In the majority of cases, adverse effects occurred within the first month of treatment and were transient. Idiosyncratic (type B) adverse effects, which were not anticipated given the known properties of the drug, occurred in one cat. Increased phenobarbitone starting dosage and the addition of a second AED were significantly associated with the occurrence of adverse effects.