Extracranial expansion of a feline meningioma.

Meningioma is the most frequently observed primary brain tumour in cats. Usually, it is associated with an intracranial expansion with consequent brain compression, oedema and brain herniation. Typical features of feline intracranial meningiomas are hyperostosis of the adjacent bone and intratumoral mineralisation. We describe a 13-year-old male neutered cat with a 1-year history of behavioural change. At clinical and neurological examination the cat showed signs consistent with right-sided forebrain lesion. Magnetic resonance images showed a right-sided extra-axial contrast enhancing mass in the region of the frontotemporal lobe. The overlying bone of the calvarium showed a marked defect with extracranial expansion of the tissue. Surgery was performed and the tumour could be exposed by a right-sided temporal approach. After extension of the bony defect the mass could be removed properly. The cat recovered well from surgery and a 12-month follow-up showed no persistent neurological deficits. Histopathological assessment of the tumour revealed a transitional grade 1 meningioma. Despite osteolysis and extracranial expansion of the tumour differentials should include menigioma in feline intracranial neoplasms.