Meningocerebral hemangiomatosis resembling Sturge-Weber disease in a horse.

The research discusses a unique case of a 3-year-old horse suffering from recurrent seizures, which on investigation revealed abnormal vascular development covering a significant portion of the brain, likened to Sturge-Weber disease seen in humans. Despite these seizures, the horse appeared normal when not experiencing a seizure episode.

Case Presentation and Findings

• The horse had been presenting with generalized seizures intermittently over a course of two months. These seizures could not be attributed to any apparent cause.
• Upon performing a necropsy, opacity was observed in the leptomeninges (the two innermost layers of tissue that cover the brain and spinal cord), which covered majorly one cerebral hemisphere. There was also thinning and collapse of cortex in the pyriform lobe on the same side.
• Under histopathology, excessive growth of blood vessels in the leptomeninges and excessive growth of the cells lining the meninges (meningothelial hyperplasia) were noted.
• Noticeable twisted blood vessels protruding deep into some areas of the underlying cortex were revealed. In these areas, there was a loss, ectopia (misplacement), and disorganization of nerve cells.
• Clusters of prominent arterioles were identified in the hardened choroid plexus of the lateral and fourth ventricles.

Additional Observations

• Apart from the major findings, the researchers also noted less severe vascular anomalies in the leptomeninges of the brain stem, right cerebrum, spinal cord, and the eye.
• Swelling of identified collections of nerve fibers (fasicles) in the left trigeminal nerve distorted its structure with onion bulb-like formations.
• Upon examination with electron microscopy, cells arranged in concentric layers with continuous basal membranes and rare presence of pinocytotic vesicles (small vesicles containing fluids) were observed.
• Strong positive staining with S-100 (a protein used in pathology to identify certain types of cells) immunohistochemistry indicated these cells were indeed nerve cells.

Anomaly and comparison

• This unusual combination of lesions exhibited by the horse was compared to human neuroectodermal dysplasias, especially Sturge-Weber disease.
• The correlation between the neuropathy (nerve disease) and the leptomeningeal hemangiomatosis (vascular malformation in the leptomeninges) is yet unclear.
• The researchers suggest that these abnormalities might result from a compound anomaly occurring during the embryological development of the horse, which could lead to dysplasia (abnormal cell growth) and possibly neoplasia (tumor formation).