Clinical and imaging findings after antiviral treatment in cats with presumptive neurologic feline infectious peritonitis: 9 cases (2020-2024).

BACKGROUND

Limited information is available regarding comparison between clinical outcomes and post-treatment imaging findings in cats with the neurologic form of feline infectious peritonitis (FIP).

HYPOTHESIS/

OBJECTIVE

Describe post-treatment imaging findings and clinical outcomes in cats with neurologic FIP treated with antiviral drugs.

ANIMALS: Nine cats with a presumptive diagnosis of neurologic FIP undergoing advanced imaging before and after antiviral treatment (GS-441524, remdesivir, or both).

METHODS

Medical records from 8 institutions were reviewed retrospectively (January 1, 2020 to December 31, 2024). Included cats had pre- and post-treatment magnetic resonance imaging (MRI) or computed tomography (CT) studies. Treatments consisted of GS-441524 (6/9), remdesivir (2/9), or both (1/9). All cats received corticosteroids. Follow-up imaging was performed at variable time points after completion of antiviral treatment.

RESULTS

Central vestibular disease was the most common neuroanatomical localization (6/9). Obstructive hydrocephalus was present in all cases on initial and follow-up imaging. Cerebrospinal fluid analysis, available in 4 cats, included pleocytosis (neutrophilic in 3/4; lymphocytic in 1/4). Complete clinical recovery occurred in 5/9 cats. Four of 9 had residual neurologic deficits and 2/9 experienced recurrence of neurologic signs. None showed complete resolution of imaging abnormalities. Imaging changes did not consistently reflect clinical outcomes. In 4/9 cats, progression of obstructive hydrocephalus was observed, including cases with clinical improvement.

CONCLUSIONS AND CLINICAL

IMPORTANCE

Clinical improvement is not always consistent with radiologic resolution in cats with neurologic FIP treated with antivirals. Post-treatment MRI findings, particularly persistent or worsening obstructive hydrocephalus, should be interpreted alongside clinical status rather than as a sole indicator of therapeutic response.