Schwannosis in Three Foals and a Calf.

This study explores the phenomenon of Schwannosis (proliferation of Schwann cells within the central nervous system) in three foals and a calf. This condition is most common in humans suffering from neurofibromatosis type-2. The affected animals, aged between 5 to 11 weeks, had shown progressive neurological signs from birth.

Key Objectives and Observations

• The primary aim of the study was to investigate the occurrence and impact of Schwannosis in foals and a calf, especially considering that this condition has been largely unrecognized in domestic animals.
• Upon analysis, it was identified that all animals had bilateral plaques of proliferative spindle cells, mainly affecting the white matter adjacent to dorsal and ventral nerve roots and variably extending into the gray matter throughout different levels of the spinal cord.

Methodology and Findings

• The proliferative cells showed strong intracytoplasmic immunoreactivity for the Schwann cell markers myelin protein zero and periaxin. This highlighted the formation of peripheral nervous system (PNS) myelin within the spinal cord.
• Glioneuronal hamartomas (foci of disorganized neural tissue) were present in all cases. In two cases, these hamartomas formed a mass effect that resulted in syringohydromyelia (a disorder in which a cyst or cavity forms within the spinal cord).

Interpretation and Conclusion

• The neonatal presentation of Schwannosis in these animals suggests that they might have been born with a developmental issue in the nervous system, with unexpected invasion of PNS-derived Schwann cells into the CNS. This case serves to further our understanding of the condition as it occurs in animals, a domain where it has typically been ignored.