Diagnostic option for suspected equine motor neuron disease

Introduction: Equine motor neuron disease (EMND) is a neurodegenerative disorder caused by increased oxidative damage in the nervous system, associated with a vitamin E deficiency. Describe the alternative diagnostic methodology for suspected EMND.

Clinical history and relevant clinical findigs: During the 2022-2023 period, three patients were examined that presented signs of weakness and muscle atrophy, proprioception alteration, chronic weight loss, dysphagia, and one of them also had the “circus elephant” stance (‘elephant on a ball’), which suggested EMND as the presumptive diagnosis.

The suggested diagnostic protocol is based on vitamin E measurements, electromyography, histopathology of the coccygeal and masseter muscles, eye fundus abnormalities, and enzyme measurements. Due to the lack of access to certain complementary diagnostic tests in these cases, histopathology of the coccygeus muscle, fundus examination and measurement of creatine kinase (CK) and aspartate aminotransferase (AST) enzymes was performed.

Evidence- based diagnosis: In none of the cases was there evidence of lipofuscin deposits in the fundus. In all three cases, CK was slightly increased and AST was normal whilst histopathology identified angulated atrophic muscle fibers compatible with EMND.

Discussion: Although vitamin E deficiency is suggested as the cause of this disease, its blood levels are often not representative, in addition to the fact that its measurement is not accessible. On the other hand, the equipment required for electromyography is usually very expensive and difficult to access, therefore, it is necessary to rely on other diagnostic techniques. Based on our results, which agree with other authors, it is extremely important to perform histopathology of the coccygeus muscle and eye fundus examination, since alterations detected in these ancillary tests, added to the history and clinical signs, allow us to reach a diagnosis of EMND.

References

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