MRI and CT Scans for Dogs with Epilepsy: When Are They Needed? 2025 Guide

When your dog experiences their first seizure, or when seizures become more frequent or severe, your veterinarian may recommend advanced brain imaging—specifically an MRI or CT scan. These sophisticated diagnostic tools have revolutionized how we diagnose and understand canine epilepsy, moving from educated guesses to precise diagnoses.

Understanding when imaging is necessary, what it reveals, and what to expect can help you make informed decisions about your dog's care. This comprehensive guide explains the role of MRI and CT scans in diagnosing canine epilepsy, based on the latest 2025 veterinary guidelines and evidence.

Why Advanced Imaging Matters: Moving Beyond Guesswork

For decades, canine epilepsy was often diagnosed based on clinical signs alone—a "diagnosis of exclusion" when no other cause could be found. Today, advanced neuroimaging has transformed epilepsy diagnosis from educated guesswork into precision medicine.

The International Veterinary Epilepsy Task Force (IVETF) classifies diagnostic confidence into three tiers:

• Tier I: Normal physical/neurological exam + routine blood/urine tests
• Tier II: Normal MRI + cerebrospinal fluid (CSF) analysis
• Tier III: EEG abnormalities confirming idiopathic epilepsy

Only dogs achieving Tier II or III confidence can be definitively labeled as having idiopathic epilepsy. This matters because 25-45% of dogs undergoing MRI for seizures have a clinically relevant abnormality that changes treatment and prognosis.

When Is Brain Imaging Indicated?

Current 2025 guidelines recommend brain imaging in specific situations. Understanding these indications helps you and your veterinarian make informed decisions.

Mandatory Imaging (MRI Preferred)

Brain imaging is considered essential in these situations:

Age-related concerns:

• Age at onset less than 6 months or greater than 6-7 years
• Any dog with first seizure after 5-6 years (risk of brain tumors rises exponentially with age)

Clinical red flags:

• Focal seizures (affecting one body part or region)
• Abnormal neurological examination between seizures
• Cluster seizures (multiple seizures in 24 hours) or status epilepticus at presentation
• Progressive seizure frequency or severity despite treatment
• Abnormal mentation or behavior between seizures
• Signs of increased intracranial pressure (papilledema, etc.)

Breed considerations:

• Breeds predisposed to intracranial disease (brachycephalic breeds, Boxers, Golden Retrievers)

Strongly Recommended

Imaging is strongly recommended when:

• Drug-resistant epilepsy (failure of two or more appropriate antiepileptic drugs)
• Systemic signs suggesting inflammatory or infectious disease
• Owner wants definitive diagnosis for peace of mind

Not Routinely Needed (But Often Performed)

Classic idiopathic epilepsy profile where imaging may be optional:

• Purebred dog, 1-5 years old
• Normal neurological examination
• Generalized tonic-clonic seizures
• Rapid post-seizure recovery
• Good response to first antiepileptic medication

Even in these cases, many owners choose imaging for certainty and to rule out structural causes. For a complete guide to understanding canine epilepsy, including diagnosis and types, see our comprehensive resource.

What Do Scans Actually Find? The Diagnostic Yield

Large-scale studies consistently show that 25-45% of dogs undergoing MRI for seizures have a clinically relevant abnormality. The likelihood increases dramatically with age:

Age-related findings:

• Under 1 year: 2-4% abnormal (congenital malformations, trauma, inflammation)
• 1-6 years: 6-10% abnormal (mostly inflammatory conditions)
• Over 6 years: 60-75% abnormal (brain tumors dominate)

Most Common Findings on MRI

Brain tumors (neoplasia): 12-38% of cases, depending on age

• Meningioma: Most common brain tumor in dogs
• Glioma (astrocytoma, oligodendroglioma): Second most common
• Pituitary macroadenoma: May cause seizures via mass effect

Inflammatory conditions: 8-11% of cases

• Meningoencephalitis of unknown origin (MUO)
• Granulomatous meningoencephalitis (GME)
• Necrotizing encephalitis (common in Yorkies and Pugs)

Vascular issues: 4% of cases

• Ischemic or hemorrhagic strokes
• Intracranial hemorrhage

Other findings:

• Hippocampal sclerosis/necrosis (associated with chronic epilepsy)
• Congenital malformations (hydrocephalus, Chiari-like malformation)
• Metabolic or toxic changes (less common, usually subtle)

Track seizure patterns with PupPal – Our comprehensive system helps you log seizures, note any focal signs, track frequency changes, and share detailed reports with your veterinarian. When you can provide clear data about seizure characteristics and progression, you help your veterinarian determine if imaging is necessary. Start tracking today.

MRI: The Gold Standard for Epilepsy Diagnosis

Magnetic resonance imaging (MRI) is considered the gold standard for diagnosing structural causes of seizures in dogs. It provides superior soft tissue detail compared to CT scans, making it ideal for identifying brain tumors, inflammation, and other abnormalities.

What to Expect During an MRI

Procedure:

• Your dog will be under general anesthesia for 30-50 minutes
• The scan itself is painless and non-invasive
• Modern anesthesia protocols have mortality rates less than 0.1% in healthy dogs
• Pre-anesthetic bloodwork and IV fluids are mandatory for safety

Standard epilepsy protocol includes:

• T2-weighted images (multiple planes)
• T2-FLAIR (best for detecting inflammatory lesions)
• T1-weighted images before and after contrast
• T2* or SWI (for detecting microhemorrhages)
• 3D volumetric imaging (for detailed hippocampal evaluation)

Contrast injection: Gadolinium contrast is almost always used, as non-contrast MRI misses 20-30% of meningiomas and most inflammatory lesions.

What MRI Reveals

Brain tumors:

• Meningioma: Extra-axial mass with broad-based dural attachment, intense contrast enhancement
• Glioma: Intra-axial mass with ring or heterogeneous enhancement, often with surrounding edema
• Pituitary tumors: May require dedicated imaging protocol for detection

Inflammatory conditions:

• Multifocal areas of increased signal on T2-FLAIR
• Strong meningeal and/or brain tissue enhancement with contrast
• Pattern helps distinguish between different types of inflammation

Other findings:

• Hippocampal sclerosis: Shrinking and signal changes in the hippocampus
• Vascular lesions: Areas of restricted blood flow or hemorrhage
• Congenital malformations: Structural brain abnormalities present from birth

CT Scans: When Are They Still Useful?

Computed tomography (CT) scans are faster (5-10 minutes vs. 45 minutes for MRI), more widely available, and less expensive. While MRI is preferred for epilepsy diagnosis, CT still has important roles:

When CT Is Appropriate

Emergency situations:

• Acute status epilepticus when anesthesia time must be minimized
• Unstable patients who need rapid assessment
• Suspected skull trauma or acute hemorrhage (CT shows bone detail excellently)

Specific scenarios:

• Brachycephalic dogs with suspected syringomyelia (if MRI unavailable)
• Screening for large masses or hydrocephalus in unstable patients
• When MRI is unavailable or cost-prohibitive

CT vs. MRI: Diagnostic Comparison

A 2023 head-to-head study found:

• CT detected 71% of lesions seen on MRI
• Missed 85% of inflammatory lesions (CT is poor for detecting inflammation)
• Missed 40% of low-grade gliomas (subtle tumors)
• Excellent for meningiomas (>95% detection rate)

Bottom line: CT is a reasonable emergency triage tool, but should never replace MRI when a definitive diagnosis is needed and the patient is stable.

Practical Considerations: Cost, Safety, and Logistics

Cost (2025 USA Averages)

CT brain (with contrast): $800-$1,800 MRI brain epilepsy protocol (1.5 Tesla): $1,800-$3,200 3 Tesla MRI: $2,500-$4,500 CSF tap + analysis (usually done under same anesthesia): +$400-$800

Pet insurance: Typically covers 70-90% after deductible if medically justified. Check your policy for imaging coverage.

Safety Considerations

Anesthesia risks:

• Modern protocols are very safe, with mortality rates <0.1% in healthy dogs
• Pre-anesthetic bloodwork helps identify any concerns
• Full monitoring during anesthesia ensures safety
• IV fluids help maintain blood pressure and organ function

Radiation exposure (CT only):

• Effective dose approximately 5-15 mSv (equivalent to 2-6 years of background radiation)
• Negligible long-term risk in dogs
• MRI uses no radiation—it uses magnetic fields

What to Expect

Before the scan:

• Your veterinarian will perform a thorough neurological examination
• Pre-anesthetic bloodwork will check organ function
• You'll need to fast your dog (usually 12 hours before anesthesia)

During the scan:

• Your dog will be under general anesthesia
• The procedure takes 30-50 minutes for MRI, 5-10 minutes for CT
• Your dog will be monitored throughout

After the scan:

• Recovery from anesthesia usually takes 1-2 hours
• Your dog may be groggy for several hours
• Most dogs go home the same day
• Results are typically available within 24-48 hours

Special Populations: Age, Breed, and Refractory Cases

Young Dogs (Under 12 Months)

In puppies, imaging often reveals:

• Congenital malformations (hydrocephalus, lissencephaly)
• Inflammatory diseases
• Trauma-related changes

3 Tesla MRI with thin slices improves detection of subtle abnormalities in young dogs.

Older Dogs (Over 7 Years)

Brain tumor risk skyrockets with age:

• 60-75% of dogs over 6 years with seizures have abnormal MRIs
• Neoplasia (tumors) dominates in this age group
• Contrast is essential—many tumors only show with contrast
• Pituitary tumors may require dedicated imaging protocol

Refractory Epilepsy (Drug-Resistant)

A 2024 Cornell study found that 41% of "idiopathic" refractory cases had subtle MRI lesions visible only on 3 Tesla MRI or retrospective review. These included:

• Hippocampal necrosis
• Focal cortical dysplasia
• Small tumors

If your dog's seizures aren't responding to medication, re-imaging with higher-resolution MRI (3 Tesla) may reveal previously missed causes. Learn more about managing drug-resistant epilepsy and when to consider additional diagnostics.

Breed-Specific Considerations

Cavalier King Charles Spaniel:

• 40-50% have Chiari-like malformation ± syringomyelia
• May require specialized imaging protocols

Pug/Yorkshire Terrier:

• High risk of necrotizing meningoencephalitis
• MRI essential for diagnosis

Golden Retriever:

• High glioma (brain tumor) risk
• Early imaging recommended

Brachycephalic breeds:

• Higher incidence of intracranial neoplasia
• May have syringomyelia-related seizures

Emerging Techniques: The Future of Neuroimaging

7 Tesla research scanners:

• Sub-millimeter resolution of hippocampal structures
• Detects subtle abnormalities missed on standard MRI

Functional MRI (fMRI):

• Maps seizure onset zones in drug-resistant patients
• Helps guide surgical treatment when appropriate

PET-MRI hybrid imaging:

• Shows metabolic activity in brain regions
• Identifies epileptogenic foci (areas where seizures start)
• Useful for complex cases

AI-assisted detection:

• Algorithms now achieve 94% sensitivity for detecting meningiomas
• 88% sensitivity for meningoencephalitis
• Helps radiologists identify subtle abnormalities

Making the Decision: A Practical Guide

Decision Algorithm for Pet Owners

First seizure, 1-5 years old, classic history, normal exam:

• Your veterinarian may recommend treating empirically first
• Consider MRI if you want certainty or if insurance requires it
• Monitor closely—if seizures worsen or change, re-evaluate

Any red flag present:

• MRI + CSF analysis under same anesthesia is recommended
• Don't delay—early diagnosis improves outcomes

Emergency presentation, unstable patient:

• CT may be done first for rapid assessment
• MRI when patient is stable for definitive diagnosis

Drug-resistant after 2 medications:

• Re-image with 3 Tesla MRI if initial scan was 1.5 Tesla
• Subtle lesions may have been missed

Questions to Ask Your Veterinarian

1. Is imaging necessary in my dog's case? (Based on age, breed, seizure characteristics)
2. What are the risks vs. benefits? (Anesthesia risk, diagnostic value, cost)
3. Should we do MRI or CT? (Based on availability, urgency, cost)
4. What will imaging change? (Treatment plan, prognosis, peace of mind)
5. Is my dog a good anesthesia candidate? (Based on age, health, pre-anesthetic testing)

The Bottom Line: Why Imaging Matters

MRI has transformed canine epilepsy from a "guess and treat" condition into precision medicine. While idiopathic epilepsy remains common (approximately 65% of cases), we now know that 1 in 3 seizure patients has a visible brain lesion—and the older the dog, the more likely it is to be serious.

Key takeaways:

• Missing a treatable brain tumor or inflammatory condition is no longer acceptable
• Age is the strongest predictor of abnormal findings
• MRI is the gold standard; CT has limited but important roles
• Early diagnosis improves outcomes for treatable conditions
• The cost is significant, but the value in accurate diagnosis and targeted treatment is substantial

For your dog: If your veterinarian recommends imaging, it's because they believe it will provide valuable information for diagnosis and treatment. While the cost and anesthesia may feel daunting, modern protocols are very safe, and the diagnostic information can be life-changing.

Frequently Asked Questions

Is MRI or CT scan necessary for all dogs with epilepsy?

No. Imaging is mandatory for dogs with red flags (age >6-7 years, focal seizures, abnormal exam, etc.) but may be optional for classic idiopathic epilepsy in young dogs. However, many owners choose imaging for peace of mind and to rule out structural causes.

How much does a brain MRI cost for a dog?

In 2025, expect to pay $1,800-$3,200 for a standard 1.5 Tesla MRI brain scan with contrast. 3 Tesla MRI costs $2,500-$4,500. CT scans are less expensive ($800-$1,800) but provide less diagnostic information.

Is anesthesia safe for MRI scans?

Yes. Modern anesthesia protocols have mortality rates less than 0.1% in healthy dogs. Pre-anesthetic bloodwork, IV fluids, and full monitoring during anesthesia ensure safety. Your veterinarian will assess your dog's anesthesia risk before the procedure.

What's the difference between MRI and CT for seizures?

MRI provides superior soft tissue detail and is the gold standard for epilepsy diagnosis. CT is faster and cheaper but misses 85% of inflammatory lesions and 40% of low-grade tumors. CT is useful for emergencies, but MRI is preferred for definitive diagnosis.

Can imaging find the cause of my dog's seizures?

Yes—25-45% of dogs undergoing MRI for seizures have a clinically relevant abnormality. The likelihood increases with age: 60-75% of dogs over 6 years have abnormal findings. However, normal imaging doesn't rule out epilepsy—it helps rule out structural causes.

Should I get a second opinion on imaging results?

If your dog has refractory epilepsy or you have concerns about the diagnosis, consulting with a veterinary neurologist for image review can be valuable. They may identify subtle abnormalities or recommend additional imaging techniques.

Ready to help your veterinarian make informed decisions? Track your dog's seizures, note any focal signs or behavior changes, and monitor response to treatment with PupPal. When you bring detailed seizure logs and progression data to your veterinarian, you help them determine if imaging is necessary and what it might reveal. Start tracking seizures today and become an active partner in your dog's diagnostic journey.

Related Reading:

• Understanding Canine Epilepsy – Complete guide to causes, types, and diagnosis
• Medication Management for Dogs with Epilepsy – How to manage anti-seizure medications effectively
• What Triggers Seizures in Dogs – Complete guide to identifying and preventing triggers
• Misdiagnoses in Canine Epilepsy – Common diagnostic challenges and how to avoid them
• Does Epilepsy Shorten a Dog's Life? – Understanding life expectancy and prognosis