Optic Chiasm and Bilateral Optic Nerve Oligodendroglioma in A 29-Month-Old German Shepherd.

First documented canine optic chiasm/nerve oligodendroglioma emphasizes rarity and diagnostic significance.

This case report documents the first documented high-grade oligodendroglioma affecting the optic chiasm and bilateral optic nerves in a 29-month-old male German Shepherd dog. Over a two-month period, the patient underwent comprehensive diagnostic evaluation including physical and ophthalmic examinations, laboratory testing, MRI imaging, ultrasound-guided biopsy, and necropsy. MRI revealed a large, lobulated, asymmetric retrobulbar mass causing compression of the optic chiasm and nerves, with imaging characteristics suggesting an aggressive neoplasm including hyperintensity on T2-weighted sequences and heterogeneous contrast enhancement with necrotic areas. Histopathologic examination confirmed high-grade oligodendroglioma with marked nuclear atypia, elevated mitotic activity, and positive OLIG2 nuclear immunoreactivity. The tumor's location within the optic pathway differs from typical canine oligodendrogliomas. This rare presentation highlights the importance of including neoplasia in differential diagnoses for optic pathway disease and demonstrates the potential value of dogs as comparative models for studying human gliomas.

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