Case Study: Cluster Seizures in a 4-Year-Old Dachshund with a Normal Brain MRI

By Mark Soderstrom, DVM, Medical Director, Veterinary Outpatient MRI 

Signalment & Presentation

Rolo, a 4-year-old male Dachshund, presented with cluster seizure activity despite ongoing anticonvulsant therapy (levetiracetam), with phenobarbital recently initiated.

Clinical history and referring records indicated:

• Recurrent seizure activity with increasing frequency and clustering
• Post-ictal neurologic abnormalities, including disorientation and ataxia
• Requirement for emergency stabilization and hospitalization due to severity
• Baseline laboratory evaluation without a clear metabolic etiology

At presentation for imaging, neurologic examination was reported as within normal limits .

Clinical Problem

This case represents a common but critical neurologic decision point:

Is this seizure disorder structural or functional?

Differential diagnoses at this stage include:

• Intracranial neoplasia
• Inflammatory or infectious encephalitis
• Vascular insult
• Idiopathic epilepsy

Given the patient’s age, progression, and cluster pattern, advanced neuroimaging was indicated to rule out structural disease.

MRI Protocol

A complete brain MRI was performed, including:

• T2-weighted sequences
• T2 FLAIR
• T1 pre- and post-contrast
• T2* (gradient echo)
• Diffusion-weighted imaging (DWI) with ADC mapping

This protocol is designed to evaluate for:

• Mass lesions
• Inflammatory changes
• Hemorrhage
• Ischemic injury
• Subtle parenchymal abnormalities

MRI Findings

The study demonstrated:

• Normal brain parenchyma
• Normal pituitary morphology and signal intensity
• No meningeal enhancement
• No evidence of mass effect, edema, or structural abnormality

Conclusion:

Normal brain MRI

Interpretation

A normal MRI in this clinical context carries significant diagnostic weight.

In a young dog with:

• Cluster seizures
• Normal neurologic exam between episodes
• Unremarkable laboratory work
• No imaging abnormalities

…the leading diagnosis becomes:

Idiopathic epilepsy

Clinical Implications

1. Structural disease effectively ruled out

The absence of:

• Mass lesions
• Inflammatory changes
• Contrast enhancement

makes neoplasia and active encephalitis highly unlikely.

2. Prognosis shifts favorably

While cluster seizures are serious, the absence of structural pathology:

• Improves overall prognosis
• Supports long-term medical management
• Reduces the likelihood of progressive intracranial disease

3. Treatment strategy becomes targeted

Management should now focus on:

• Optimization of anticonvulsant therapy
• Combination therapy when indicated (e.g., levetiracetam + phenobarbital)
• Monitoring for breakthrough seizure activity

Further diagnostics (e.g., CSF analysis) may be considered selectively but are not mandatory in the setting of a normal MRI and stable neurologic exam.

Key Takeaway for Referring Veterinarians

This case underscores a critical point:

MRI is not only diagnostic—it is decisional.

A normal brain MRI:

• Eliminates the most serious differentials
• Allows confident classification as idiopathic epilepsy
• Prevents unnecessary escalation toward invasive or empirical treatments

Summary

Rolo’s case illustrates the value of MRI in seizure workups:

• Cluster seizures prompted appropriate escalation to advanced imaging
• MRI ruled out structural intracranial disease
• Diagnosis narrowed to idiopathic epilepsy
• Treatment pathway clarified and prognosis improved