Vascular hamartoma in the central nervous system of a foal.

The study reports a case of a young horse (a Freiberger foal) with a rare vascular abnormality called a vascular hamartoma, found in the brain. This uncommon condition, previously reported in dogs and cats, caused the foal to have breathing and swallowing difficulty, facial paralysis on one side, and a corneal ulcer in one eye. The researchers conclude that the foal’s symptoms were a result of neural compression caused by the hamartoma.

Background on Vascular Hamartomas

• Vascular hamartomas are non-cancerous malformations of blood vessels.
• They are developmental anomalies, meaning they occur during a creature’s growth and development.
• While hamartomas in general are not particularly rare, vascular hamartomas in the central nervous system are, especially in horses. Prior reports mainly include cases in cats and dogs.

The Foal’s Symptoms and Diagnosis

• The Freiberger foal mentioned in the study was only four weeks old.
• It had shown consistent issues with breathing and swallowing since birth. Upon investigation, it was diagnosed with bilateral laryngeal paralysis.
• The foal later developed left-sided facial nerve paralysis and a secondary corneal ulcer in its left eye, prompting further examination.
• During an autopsy, investigators found a pinkish mass in the obex region of the brain, leading to histological and immunohistochemical analysis.

Investigation and Final Diagnosis

• Microscopic examination of the tissue showed the mass was made up of numerous thin-walled, blood-filled vascular structures of different sizes, spread throughout the white matter of the obex.
• Immunohistochemical tests, which involve the use of antibodies to detect specific antigens, was used to further identify the nature of the mass.
• The cells lining the mass were immunoreactive for Factor VIII (also known as von Willebrand factor), indicating they were endothelial cells, the type that line blood vessels.
• The vascular lining also showed variable immunoreactivity (responses to antigens) for smooth muscle actin and vimentin, proteins found in muscle and connective tissue cells respectively.
• Normal neural tissue, revealed by antibodies directed against glial fibrillary acidic protein and neuron-specific enolase, was found in between the vascular proliferations.
• Based on their findings, the researchers ultimately diagnosed the mass as a focal vascular hamartoma in the obex.
• The study suggests that the neurological symptoms experienced by the foal were due to the surrounding neural tissue being compressed by the hamartoma.