Importance of the ophthalmological examination in case of suspicion of equine motor neuron disease. Description of 2 cases.

Introduction: Equine motor neuron disease (EMND) is a degenerative neurological condition caused by an imbalance between oxidative stress and antioxidant agents, associated with a vitamin E deficiency. To describe the importance of the ophthalmological examination in case of suspicion of EMND.

Clinical history: Two patients with recurrent esophageal obstruction who also presented generalized muscular atrophy and progressive weight loss were evaluated, being EMND considered as the presumptive diagnosis. For this reason, a fundus examination was performed.

Relevant clinical findings: No alterations in visual function were observed, but brownish-black deposits with a mosaic distribution pattern deposited in the tapetal and peripapillary area were observed in the fundus, compatible with lipofuscin deposits.

Evidence- Based diagnosis: To confirm the definitive diagnosis, clinical history and ophthalmological findings were complemented with histopathology of the coccygeal muscles. In both patients, angular atrophic muscle fibers were evident, consistent with EMND.

Discussion: Most authors agree that the presence of lipofuscin deposits in the retina is a pathognomonic sign of the disease. This is due to the fact that the appearance of these accumulations is the result of increased phagocytosis of the photoreceptors’ outer segments by the retinal pigment epithelium and a failure in lysosomal degradation associated with damage due to oxidative stress.

It is worth emphasizing the importance of ophthalmoscopy as a diagnostic method in cases of suspected EMND since it is a fast and non-invasive study and, even though lipofuscin deposits are not constant findings (30-50% of cases), it becomes an accurate diagnostic method if lipofuscin deposits are evident.

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