Dana – Seizures Due to Meningioma
Dana is a 7-year-old spayed female Labrador Retriever. She originally presented to an emergency clinic for evaluation of new onset seizures. She was managed overnight and transferred to the neurologist the following morning. On examination, Dana was bright and alert. Her cranial nerve examination was normal, as were her postural reactions and spinal reflexes. She did not seem painful and exhibited a normal gait.
Diagnosing the Cause
Seizures tell us there is a problem with the brain. They are a symptom of abnormal brain function, but do not tell us the cause. In general, there are three main causes of seizures. Extracranial causes such as low blood sugar and severe liver disease, intracranial causes such as brain tumors and strokes, and idiopathic epilepsy.
Dana’s CBC and chemistry panel did not show a cause for the seizures. Chest x-rays were normal. Idiopathic epilepsy typically has an onset between 1 and 5 years of age, making this less likely but still possible for Dana. Intracranial causes such as a tumor or stroke were possible, even though her neurological examination was normal.
An MRI was performed by the neurologist which is pictured below. Note the large, oval, well-demarcated mass that is on the surface of the brain, overlying the frontal lobes. The most common type of mass that has this appearance is a type of brain tumor called a meningioma. There are other types of tumors that can have a similar appearance.
Dana was discharged with prednisone and Keppra. Prednisone was prescribed at 0.5mg/kg orally twice daily on a tapering schedule. Keppra was prescribed at 30mg/kg orally three times daily. She was then referred to Southeast Veterinary Neurology for consultation to consider treatment options.
On initial examination at Southeast Veterinary Neurology, Dana was still neurologically normal. She had experienced 3 more seizures prior to referral. Based on the presence of a space occupying mass and our suspicion for it being a meningioma, several treatment options were discussed.
The first treatment option was surgery. Surgery would be indicated to remove as much of the tumor as possible, obtain a histologic diagnosis and confirm what type of tumor it was as well as whether is was benign or malignant. Since the mass is located within the brain, tumor margins are typically not possible, so we typically recommend follow up radiation therapy after surgery.
The second option was to consider radiation without surgery. The advantage of this was that it would be less expensive than surgery and radiation combined, but it would require multiple anesthetic periods and we would not know exactly what sort of mass we were treating.
The third option was to consider palliative medications of prednisone and Keppra. This is the least invasive and least expensive option but typically carries the worst prognosis. The owners elected surgery with the plan of follow-up radiation depending on the biopsy results.
A transfrontal craniectomy was performed. At surgery, a grayish, friable mass was encountered on the surface of the brain. The mass was removed with gentle dissection as well as ultrasonic aspiration. Surgery went well with all grossly visible tumor removed.
An MRI was performed immediately after surgery to assess for completeness of resection as well as any evidence of hemorrhage or swelling within the brain. This is Dana’s post-operative MRI. As you can see, there is total gross resection of the tumor.
Dana’s biopsy came back as a meningioma. Meningiomas tend to be slower growing tumors of the coverings of the brain. Follow-up radiation therapy was performed. Dana tolerated surgery and radiation well and has not had any further seizure activity.
A follow-up MRI was performed 3 months after finishing radiation (6 months after surgery). We are happy to say that there is no evidence of tumor regrowth on the follow-up MRI. Dana also has not had any further seizures since surgery.
Take Home Message
There are several important lessons that Dana teaches us:
- Seizures in dogs older than 6 are more likely to be caused by an extracranial or intracranial cause. Idiopathic epilepsy is unlikely in dogs older than 6 or 7.
- Dogs with completely normal examinations may still have an intracranial cause for seizures.
- While serious, there are treatment options for dogs with brain tumors. Many dogs can do quite well.
- Surgery followed by adjunctive therapy of radiation offers the best chances for a long-term positive outcome.