Presumed Neuroglycopenia Caused by Severe Hypoglycemia in Horses

Abstract

BackgroundNeuroglycopenia refers to a shortage of glucose in the brain resulting in neuronal dysfunction and death if left untreated. Presumed neuroglycopenia has not been described in horses.ObjectiveTo report neurological signs in horses with presumed neuroglycopenia as the result of severe hypoglycemia.AnimalsNinety horses (hours to 28 years of age) diagnosed with hypoglycemia (blood glucose concentration < 75 mg/dL [< 4.2 mmol/L]).MethodsRetrospective study. Electronic medical records were searched. Signalment, history, complaint, clinical signs, laboratory findings including CSF analysis, electroencephalogram, clinical or definitive diagnosis, and outcome were recorded. Kruskal‐Wallis analysis of variance and logistic regression were used to investigate association between blood glucose concentration and data extracted. Statistical significance was set at P < 0.05.ResultsThirty‐eight and 52 horses had mild (50‐74 mg/dL [2.8‐4.1 mmol/L]), and severe hypoglycemia (< 50 mg/dL [< 2.8 mmol/L]), respectively. Most common causes of hypoglycemia included liver and gastrointestinal (40%) disease, sepsis (33%), neoplasia (7%), and insulin‐induced (4%). Most common neurologic deficits included obtundation (100%), seizures (42%), and disorientation (22%). CSF‐glucose was severely low (mean 2.5 mg/dL [0.1 mmol/L], median 0 mg/dL). Paroxysmal discharges in support of seizures were identified in the occipital (visual) and parietal (closest to temporal‐auditory) cortical regions upon EEG examination (8/8 horses).Conclusions and clinical importanceNeuroglycopenia is presumed to occur in horses as the result of severe hypoglycemia. Subclinical seizures, and intermittent blindness and deafness of cortical origin can occur. Severe altered state of consciousness and seizures can be observed at a blood glucose cut‐off value of < 42 mg/dL (< 2.3 mmol/L).

Hypoglycaemia, hypoglycorrhachia, neuroglycopenia and glycaemic thresholds

“…Clinical signs that result from hypoglycaemia in adult horses have not been reported extensively but have included signs resulting from cerebral dysfunction such as severe alterations in the state of consciousness, collapse and generalised seizures. Similar to the case reported here, other clinical signs associated with severe hypoglycaemia in adult horses may include disorientation, unawareness of surroundings, sweating, ear twitching, chewing, staggering and clonic muscle contractions (Aleman et al 2018). Various and diverse clinical signs in the reported case likely resulted from the combined effects of both extensive abdominal neoplasia and paraneoplastic hypoglycaemia.…”

“…Although CSF was not collected in order to ascertain the extent of hypoglycorrhachia in this case, a correlative relationship between severity of hypoglycaemia and the CSF glucose concentration was recently reported in a small number of horses (Aleman et al . ). In that study, CSF glucose was unmeasurable (glucose concentration was zero) in five of twenty neuroglycopenic hypoglycaemic horses and foals.…”

“…Similar to the case reported here, other clinical signs associated with severe hypoglycaemia in adult horses may include disorientation, unawareness of surroundings, sweating, ear twitching, chewing, staggering and clonic muscle contractions (Aleman et al . ). Various and diverse clinical signs in the reported case likely resulted from the combined effects of both extensive abdominal neoplasia and paraneoplastic hypoglycaemia.…”

“…Neurogenic signs, such as tremors, palpitations, anxiety and sweating were not reported, similar to observations in studies of other hypoglycaemic equids (Aleman et al . ).…”

Clinical Pathology in the Adult Sick Horse

“…Glucose concentrations often are surprisingly normal in most adult horses with hepatic failure but, in some cases, glucose may be very low. 52,53 Hematocrit, iron concentrations, and percentage iron saturation occasionally are high in horses with severe liver disease, in particular those with acute necrosis. The erythrocytosis can persist despite adequate rehydration.…”