Spinal ataxia in a horse caused by a synovial cyst.

This research discusses a case of spinal ataxia in a horse caused by a synovial cyst, examining the symptoms, the diagnosis process, and the anatomical impact of the cyst on the spinal cord.

Introduction

• The paper initially speaks about the frequent occurrence of ataxia, or incoordination, in horses due to spinal cord diseases.
• It lists out several disorders that could be related to such a condition, including the cervical vertebral stenotic myelopathy, equine degenerative myeloencephalopathy, equine proto-zoal myeloencephalitis and others.

Case Presentation

• The horse in this case study is a 19-month-old Quarterhorse stallion that had developed ambulatory difficulties over six months.
• The symptoms included walking difficulties with hypermetria and stumbling, dragging of front feet while backing up, and reluctance to either flex or extend the neck.
• These symptoms became more pronounced whenever the neck was extended.

Diagnosis and Necropsy Findings

• Radiographic examination of the cervical spine had shown no abnormalities.
• However, the horse unfortunately died while being prepared for myelography, an imaging procedure used to examine the spinal cord.
• Upon necropsy, the researchers found a protruding synovial cyst in the vertebral canal of the fifth and sixth cervical vertebrae.
• The cyst, filled with a clear yellow fluid, showed no direct connection with surrounding meninges or vertebral joints.
• Microscopically, the cyst wall was composed of fibrocytes and demonstrated minor foci of hemorrhage.

Investigation and Analysis

• The scientists further observed a mild to moderate spongy appearance of dorsal and ventral funiculi in the cervical vertebrae, indicating significant changes in the pathology of the area.
• Degenerated axons and debris-laden phagocytes were present in spaces usually occupied by healthy axons suggesting that the cyst had slowly triggered a degradation of the nerve fibers.
• The team concluded that the cyst might have caused compression on the spinal cord, particularly when the neck was extended.
• Despite certain differences in the bony structure and absence of a visible connection to the surrounding tissues, the properties of the cyst pointed towards it being a synovial structure.
• Many similar cysts have been found to affect the Cs-C7 region in horses, often resulting in significant changes in the bones of the synovial joints around the cyst.

Conclusion

• The compression caused by the cyst on the spinal cord seems to have led to the displayed ataxia symptoms in the horse.
• The researchers highlight that while such synovial cysts are common in horses, no literature was found indicating their occurrence in other species.