Ependymoma of the neurohypophysis and hypernatremia in a horse.

This research paper explores the case where a 2-year-old horse displayed unusual physical symptoms, ultimately resulting in its death due to a brain tumor compressing its neurohypophysis. This condition led to persistent high plasma sodium levels, despite efforts to correct it, presumably disrupting the horse’s thirst mechanism.

Case Presentation and Clinical Findings

• The study focuses on a 2-year-old Standardbred gelding that displayed notable symptoms, such as third eyelid prolapse, myoclonus (sudden, involuntary twitching) of the muscles in the head, neck, and forelimbs, and constant tail swishing.
• Notably, the horse also had elevated plasma sodium concentration (hypernatremia). Despite the high sodium levels, the horse wasn’t consuming water.

Efforts in Medical Intervention and Results

• Medical practitioners attempted to rectify the horse’s hypernatremia via intravenous (IV) fluid administration. However, the condition couldn’t be corrected, and the horse’s overall condition progressively worsened.
• Six days post-initial examination, the horse died.

Necropsy Findings of the Horse

• A post-mortem examination (necropsy) was conducted to determine the cause of death. They found that a tumor had been compressing a part of the horse’s brain called the neurohypophysis.
• The neurohypophysis, a region of the brain involved in water and electrolyte balance, was being influenced by the tumor, which could explain the consistently high sodium levels and the horse’s lack of drive to drink water. Furthermore, the examination revealed that the tumor was also compressing the supposed location of the thirst centers in the horse’s brain, providing further rationale for its altered thirst.

Conclusion of the Research

• The research concludes that the hypernatremia in the horse was a likely result of its altered perception of thirst. The pressing of the brain tumor on the neurohypophysis and the potential thirst centers impaired the horse’s normal physiological functions, leading to such symptoms.
• The study illuminates the need for further research into the neurological influences on thirst mechanisms in horses and potentially other animals, particularly in relation to brain tumors such as the ependymoma found in this case.