A 2020 article published in Equine Veterinary Education discussed the "importance of muscle biopsy in horses with neuromuscular disease as concurrent diseases may be present that require specific treatment for a positive outcome."
"Sarcocystis myositis and vitamin E deficiency in a Gypsy Vanner stallion suspected of having equine motor neuron disease" was authored by A. C. Trimble, K. M. Delph and E. R. Perry of Kansas State University; and S. J. Valberg of Michigan State University.
A 3‐year‐old Gypsy Vanner stallion was presented for evaluation of intermittent recumbency, muscle fasciculations, weakness, low head carriage, shifting of weight between the hindlimbs and an elevated tail head. History, physical examination and serum alpha tocopherol concentrations were suggestive of vitamin E deficiency and equine motor neuron disease (EMND). Sacrocaudalis dorsalis medialis muscle biopsy identified myositis secondary to sarcocystosis. Treatment with alpha tocopherol, ponazuril and sulfadiazine/pyrimethamine resulted in significant improvement in muscle weakness and body condition with resolution of sarcocystosis and inflammation on repeat muscle biopsy. This case illustrates the importance of muscle biopsy in horses with neuromuscular disease as concurrent diseases may be present that require specific treatment for a positive outcome.