A novel encephalopathy in a thiamine-deficient dog resembling human Wernicke’s disease with atypical MRI pattern

Abstract

Thiamine is a water-soluble vitamin, which participates in several vital metabolic pathways involved in energy metabolism and neurotransmitter synthesis of mammals. In companion animals thiamine deficiency is classically associated with signs of diffuse encephalopathy and lesions on brainstem nuclei and mesencephalic colliculi evident on magnetic resonance imaging. This paper describes a novel clinical presentation in a thiamine-deficient dog showing multifocal, central and peripheral nervous and cardiovascular system alterations. Brain MRI showed bilateral caudate nuclei damage, with necrotic-malacic evolution, similar to the atypical MRI pattern found in Wernicke's encephalopathy in humans. Detection of bilateral symmetrical lesions of the caudate nuclei in dogs should prompt consideration of a thiamine deficiency among the differential diagnoses.

Evaluation of blood thiamine concentration in hospitalized dogs with and without critical illness

“…15,17,20,25,43 There are rare documented cases of clinical thiamine deficiency in which blood thiamine concentrations are measured at time of diagnosis in the veterinary literature. 7,38,44 Unfortunately, methods of thiamine analysis are inconsistent across veterinary case reports, and most reports of thiamine deficiency in dogs are based on response to treatment and resolution of clinical signs. 9,38,44,45 In a dog presenting for severe neurological dysfunction, thiamine deficiency was diagnosed based on tB1 concentration <7.5 ng/ml, measured by mass spectrometry; however, TDP was reportedly normal (15.3 ng/ml) in that dog based on the provided reference interval.…”

“…7,38,44 Unfortunately, methods of thiamine analysis are inconsistent across veterinary case reports, and most reports of thiamine deficiency in dogs are based on response to treatment and resolution of clinical signs. 9,38,44,45 In a dog presenting for severe neurological dysfunction, thiamine deficiency was diagnosed based on tB1 concentration <7.5 ng/ml, measured by mass spectrometry; however, TDP was reportedly normal (15.3 ng/ml) in that dog based on the provided reference interval. 38 A more recent case report of clinical thiamine deficiency in a dog fed a thiamine-deficient diet identified neurological dysfunction at TDP of 40.2 ng/ml (laboratory reference interval = 46-112 ng/ml), measured by HPLC on whole blood.…”

“…9,38,44,45 In a dog presenting for severe neurological dysfunction, thiamine deficiency was diagnosed based on tB1 concentration <7.5 ng/ml, measured by mass spectrometry; however, TDP was reportedly normal (15.3 ng/ml) in that dog based on the provided reference interval. 38 A more recent case report of clinical thiamine deficiency in a dog fed a thiamine-deficient diet identified neurological dysfunction at TDP of 40.2 ng/ml (laboratory reference interval = 46-112 ng/ml), measured by HPLC on whole blood. 44 In the current study, the lowest reported thiamine measurement was 74.6 ng/ml in healthy dogs and 44.3 ng/ml in dogs with critical illness, far higher than those consistent with thiamine deficiency in people, although the minimum TDP measured in critically ill dogs was not much higher than that reported in the aforementioned case report of a thiamine-deficient dog.…”

“…As such, criteria for the diagnosis of thiamine deficiency are also unknown. Previous reports in which thiamine (TDP or fB1) is measured in healthy dogs use variable methodologies, including microbial methods, mass spectrometry, or HPLC on washed RBCs or whole blood samples, a, 7,35–38 making it difficult to directly compare thiamine status in healthy dogs between studies and establish a true reference interval. The current study focused on evaluation of TDP concentrations measured by HPLC, as it more accurately reflects true thiamine status of the patient; however, tB1 and fB1 were also measured to provide complete thiamine evaluation of hospitalized dogs.…”

“…Thiamine deficiency in people has been defined most commonly as whole blood thiamine concentration <3.22–4.14 ng/ml (7–9 mmol/L), although 1 study evaluating thiamine in people with septic shock had a cutoff of <16 ng/ml 15,17,20,25,43 . There are rare documented cases of clinical thiamine deficiency in which blood thiamine concentrations are measured at time of diagnosis in the veterinary literature 7,38,44 . Unfortunately, methods of thiamine analysis are inconsistent across veterinary case reports, and most reports of thiamine deficiency in dogs are based on response to treatment and resolution of clinical signs 9,38,44,45 …”