Atypically located arachnoid cyst in a five-year-old cat.

Area of Science:

• Veterinary Neurology
• Comparative Pathology

Background:

• Arachnoid cysts are leptomeningeal cysts found in spinal or intracranial locations.
• Intracranial arachnoid cysts are infrequently reported in felines, with limited prior case documentation.

Purpose of the Study:

• To report the clinical, gross, and histopathological findings of an intracranial arachnoid cyst in a cat.
• To emphasize the diagnostic utility of magnetic resonance imaging and histopathology in identifying feline intracranial arachnoid cysts.

Main Methods:

• Magnetic resonance imaging (MRI) was utilized to identify and characterize the intracranial lesion.
• Necropsy and histopathological examination, including immunohistochemistry, were performed for definitive diagnosis.

Main Results:

• A 5-year-old European Shorthair cat presented with chronic, asymmetrical encephalopathy.
• MRI revealed a focal, non-contrast-enhancing, fluid-filled cavity in the left temporal and piriform lobes.
• Histopathology confirmed an arachnoid cyst with characteristic features and adjacent neuroparenchymal changes.

Conclusions:

• Intracranial arachnoid cysts are a significant differential diagnosis for feline encephalopathy.
• Comprehensive diagnostic imaging and histopathological evaluation are crucial for accurate diagnosis of these rare feline intracranial lesions.