Epidural melanoma causing posterior paresis in a horse.

An elderly, gray stallion, which experienced severe posterior paralysis, bladder paralysis, and perineal anesthesia, is found to have epidural melanoma at autopsy after its death. The tumor had been present for a long time and was the primary cause of the neurological dysfunction.

Background

• This research article discusses a case study involving an aged, gray stallion horse that was brought for examination due to severe posterior paralysis (impairment of movements), bladder paralysis (loss of bladder control), and perineal anesthesia (numbness in the region around the anus).

Findings

• Upon preliminary examination, the horse’s condition was detected as lower motor neuron dysfunction at the lumbosacral level of the spinal cord, causing the hind paresis and bladder control loss.
• Necropsy observed a single epidural melanoma at vertebrae L5-6. This tumor is abnormal growth of pigmented cells (known as melanocytes) in the epidural space, the area outside the dura mater which is the outer layer of the meninges that surround the spinal cord.
• The horse’s cerebrospinal fluid was also noted to have turned yellow.

Conclusion

• The report concluded the melanoma as primary, meaning it originated where it was found. The evidence for this conclusion is due to the absence of cutaneous melanotic growth and non-involvement of other organs.
• The extensive vertebral remodeling indicates that the neoplasm had been present for an extended period before its discovery.
• The horse’s health condition deteriorated rapidly due to spinal cord compression caused by the growth of the neoplasm, leading to acute and progressive neurologic dysfunction.

Significance of the Research

• This case study brings attention to epidural melanoma as a potential cause for fullminating posterior paresis, bladder paralysis, and perineal anesthesia in horses, especially aged ones.
• The case encourages the veterinary medicine field to consider epidural melanoma in cases presenting similar symptoms, given the severity of the impact on the horse’s health and the apparent long-term presence of the tumor without detectable symptoms until the end stage.