Brain MRI in cats

What brain MRI answers in a cat

Brain MRI in cats is mostly asked one question: is there a structural cause for the signs? The answer sorts cats into two groups:

• cats with a lesion that needs its own work-up
• cats whose scan is normal and whose seizures are likely idiopathic or of unknown cause

Seizures: how often the scan is normal

• Large imaging series. In 432 MRI studies of cats with suspected epileptic seizures (Knebel et al., Veterinary Record, 2026), 39% showed a structural lesion and 61% did not. Among cats with a lesion, the presumptive imaging diagnoses were inflammatory disease (25%), extra-axial neoplasia (19%), metabolic or toxic causes (12%), congenital disorders (10%), lesions of unknown relevance (9%), intra-axial neoplasia (7%), trauma (5%), suspected hippocampal necrosis (5%) and vascular events (4%). These diagnoses were imaging-based, without histopathology.
• Age. In 143 epileptic cats (Riegler et al., Tierärztliche Praxis Ausgabe K: Kleintiere/Heimtiere, 2022), MRI was normal in 49%, showed extrahippocampal changes in 18% and hippocampal signal changes in 33%. Extrahippocampal changes were found mostly in cats older than 6 years.
• The hippocampus is hard to interpret. In the same study, hippocampal sclerosis was found on histopathology in every MRI category, including cats with a normal MRI. Whether hippocampal signal change is the cause or the consequence of seizures is unclear in most cases.
• Orofacial seizures. In 35 cats with complex partial seizures with orofacial involvement (Flegel et al., Journal of Feline Medicine and Surgery, 2025), T2-weighted or FLAIR hippocampal hyperintensity was seen in 57.1% and contrast enhancement in 27.1%. Antibodies against voltage-gated potassium channels were found in 31.4%, with only a weak correlation to the MRI changes. No MRI finding was consistent across all cats.

Tumours: meningioma and lymphoma

In 46 cats with histologically confirmed brain tumours (Troxel et al., Journal of Veterinary Internal Medicine, 2004), MRI detected the tumour in 45 (98%). Two blinded reviewers identified the correct tumour type in 82% of cases from MRI appearance alone.

Tumour	MRI pattern reported
Meningioma	Always extra-axial, most often ovoid, marked contrast enhancement, mild peritumoral oedema (Troxel et al.)
Glioma	Always intra-axial, ring enhancement, usually more peritumoral oedema than other tumours (Troxel et al.)
Lymphoma	Intracranial lesions extra-axial (7 of 22), intra-axial (2) or mixed (13); all lesions enhanced, and meningeal enhancement was present in all but 2 of 31 cats. No feature was pathognomonic (Durand et al., Journal of Veterinary Internal Medicine, 2022)

Two meningioma findings matter for the report:

• Herniation is common. On MRI of 24 cats with intracranial meningioma (Minato et al., Journal of Veterinary Medical Science, 2021), all 24 had brain herniation: through the foramen magnum in 23, caudotentorial in 21 and subfalcine in 18. Relative to cranial cavity volume, meningiomas were larger in cats than in dogs. Altered behaviour, not seizures, was the most common sign in cats (43%).
• Imaging guides treatment and follow-up. In 61 cats treated for intracranial meningioma (Tichenor et al., Journal of the American Veterinary Medical Association, 2024), median survival was 1,345 days after surgery and 339 days after stereotactic radiotherapy. Regrowth or new tumour growth was confirmed on MRI or CT in 30% of the surgery group and in 4 radiotherapy cats (28%).

Inflammatory disease: feline infectious peritonitis

In 24 cats with histopathologically confirmed neurologic feline infectious peritonitis (FIP) (Crawford et al., Journal of Veterinary Internal Medicine, 2017), MRI was abnormal in every cat. Findings were:

• meningeal contrast enhancement (22)
• ependymal enhancement (20)
• ventriculomegaly (20)
• syringomyelia (17)
• foramen magnum herniation (14)

All 11 cats that had CSF analysis showed a marked increase in protein and nucleated cell count. Ependymal enhancement with ventriculomegaly is therefore a pattern worth looking for in a cat with multifocal or central vestibular signs.

Feline brain MRI protocol at a glance

Many of the patterns above are patterns of contrast enhancement: the tumour patterns, the meningeal enhancement of lymphoma and the ependymal enhancement of FIP. A feline brain study therefore pairs T2-weighted and FLAIR images, which show signal change such as hippocampal hyperintensity, with post-contrast images.

What the radiologist looks at

• Where a mass sits. Extra-axial or intra-axial, with its shape, enhancement and oedema, which together pointed to the right tumour type in 82% of cases.
• Herniation and its type. Because it was so frequent with meningioma, its presence and type are worth stating explicitly, as they bear on anaesthesia and CSF sampling decisions.
• Meninges and ependyma. Meningeal enhancement in lymphoma, and ependymal enhancement with ventriculomegaly in FIP.
• The hippocampus. Signal change is reported, but whether it is cause or consequence of seizures is usually unclear.

What your report will include

Every Veheri case is read by a radiologist or neurologist, and when you order you can choose Diplomate-only reporting or the full specialist panel. Neurology reporting covers CT and MRI. You can chat directly with the specialist assigned to your case, and a simplified pet owner report helps you explain the findings to the owner.

When you take the report forward:

• Imaging diagnoses are presumptive. The largest series had no histopathological confirmation, and lymphoma has no pathognomonic MRI feature. MRI is interpreted together with the signalment, clinical presentation and CSF analysis.
• A normal MRI does not exclude hippocampal pathology, as hippocampal sclerosis was found even in cats with a normal scan.
• CSF after a normal or hippocampal-only scan. In 87 epileptic cats with an unremarkable MRI or hippocampal signal change only (Majercikova et al., Journal of Feline Medicine and Surgery, 2023), CSF analysis was abnormal in 4 cats (4.6%). All four had a mildly increased nucleated cell count and none had increased protein (one cat had no protein measurement). The authors suggest weighing this before a CSF tap.
• Follow-up imaging after meningioma treatment. Regrowth or new growth was confirmed on MRI or CT in 30% of the surgery group and in 4 radiotherapy cats (28%).
• Talking to the owner: in cats with meningioma, altered behaviour, not seizures, was the most common sign. This helps explain why a change in behaviour can be a reason for brain MRI.

What to include when you request a feline brain MRI report

• signalment: age, breed and sex
• signs and their onset: seizures (type, frequency, clusters, orofacial involvement), behaviour change, circling, vestibular signs
• time since the last seizure
• neurological examination and suspected localisation
• systemic signs and blood results, which matter when FIP or lymphoma are possible
• CSF or antibody results, and any previous treatment, especially corticosteroids

How Veheri can help

Veheri works with veterinary radiologists and neurologists, reports brain MRI studies remotely for clinics, and can support your team with MRI scanning protocols for cats with seizures or forebrain signs. For related reading, see brain MRI for seizures in dogs and how Veheri neuroimaging reports are structured.