What is arachnoidal hyperplasia in the context of optic nerve gliomas, and how is it identified radiologically?

Arachnoidal hyperplasia refers to the thickening of the perioptic meninges often seen in association with optic nerve gliomas. It represents a peritumoral reactive meningeal change. Key diagnostic features include enhancement of the optic nerve sheath on MRI, which may mimic optic nerve sheath meningioma. Clinically, it is important to differentiate from true tumor invasion, as treatment approaches differ significantly. Common pitfalls include misinterpreting the enhancement as tumor extension rather than reactive change.