Micah’s Mystery: A Case of Seizures in a Golden Retriever

Ashley D. Justice

Meet Micah

• 11 year old intact male Golden Retriever• Agility Champion• Presented to Auburn’s neurology service on

8/18/09 due to recent onset of seizure activity.

History

• No previous history of seizures• No other medical conditions other than

hypothyroidism.• First seizure activity on 6/13/09 • Transported to emergency clinic• Micah was placed on phenobarbital (63.8 mg

tablet BID)

History cont.

• Micah was weaned off of the medication, then suffered another seizure a week later (8/9/09).

• Controlled with rectal diazepam• Micah was placed back on the phenobarb• rDVM tested for E.canis, Lyme disease, RMSF

Physical Examination

• Bright, Alert, Responsive• Temperature, pulse, and respirations were all

within normal limits.• No significant abnormalities found

Neurologic Examination

• Mental status: normal• Gait and Posture: normal with the exception

of a slightly abnormal rear limb gait• Slight, intermittent right head tilt was present,

otherwise, all cranial nerves WNL• Spinal reflexes: WNL• Postural reactions: WNL

Seizures

• Definition: the clinical manifestation of an excessive discharge of hyperexcitable cerebrocortical neurons.

• Generalized, simple partial, or complex partial• Brief/isolated vs. Cluster• Micah: generalized

Pathophysiology

• Imbalance between normal excitability and inhibitory mechanisms due to an intra or extra cranial disease process.

Seizure Classification

• Primary epileptic seizures– 44%- no identifiable cause of seizure activity– Large breed dogs– 1-5 yrs. (most initial episodes are from 6 mo.-3 yrs)– Longer inter-ictal period (>4 wks)– Generalized motor seizures– Considered familial or inherited

Seizure Classification

• Secondary epileptic seizures – 46% - animal has an identifiable intracranial

abnormality – Bimodal onset- <1 yr. or >7yr.– Partial seizures included– First seizure is usually between midnight and 8

am.– Many etiologies

Seizure Classification

• Reactive epileptic seizures– 10%– Metabolic, toxic, or other noxious insult capable of

inducing seizures.– Most likely when inter-ictal period is <4 wks.– Most involve organ or endocrine disease.– All ages– Many etiologies

Initial Treatment

• When to treat– >1 seizure in a 24 hour period– >1 seizure every 6 weeks– History of status or clusters– Judgement call

• Goal: to reduce the seizure frequency to less than one single seizure every 6-8 weeks ASAP.

• Potassium Bromide and Phenobarbital are the most common treatment options.

KBr vs. Phenobarb• KBr --• Dosage: 40-50 mg/kg q24 (lower dose when used as an adjunct)• Contraindication: renal insufficiency• Ensure stable dietary chloride intake • Side effects: ataxia, lethargy, PU/PD• Phenobarb --• Dosage: 2.5-4 mg/kg q12

– If seizures are occurring at intervals of less than 7 days, initiate PB therapy with an IV loading dose of 15-25 mg/kg.

– Measure levels in 2 wks. (target level is 20-45 mcg/ml)• Contraindication: liver disease

Other considerations

• Only if no seizures have occurred in 6-12 months, consider slowly weaning over a period of a few months.

• Do not administer drugs that interfere with the metabolism of PB:– Chloramphenicol, cimetidine, ranitidine, and tetracyclines.

• Do not administer drugs which may lower the seizure threshold: – Ace, xylazine, ketamine, estrogens, tricyclic

antidepressants, bronchodilators.

Initial Diagnostics

• CBC, Serum chemistries, Urinalysis- no significant abnormalities.

• 3 view thoracic radiographs- WNL• Titers for RMSF, E.canis, Neospora, Distemper,

Toxoplasma- RMSF again mildly elevated, but likely represents previous exposure or exposure to a non-pathogenic strain. Distemper borderline increased, but probably not clinically significant.

• Brain MRI

MRI results

27/14

12

4

Intracranial Tumors

• Seizures could be the result of expansile growth or peri-tumoral effects (edema, compromised blood flow)

• Rarely disseminate throughout the CNS by hematogenous or CSF routes.

• Incidence: 14.5 in 100,000

Types of Intracranial Tumors

• Astrocytic tumors• Oligodendroglial tumors• Ependymal cell tumors• Mixed gliomas• Tumors of the Meninges

Treatment Plan

• Continue with the current drug regimen (phenobarb, saloxine)

• Discharge (8/19/09) to return on 8/25/09 for brain surgery.

8/25/09

• Micah returns to Auburn for brain surgery• Bright, alert, and responsive with no seizure

activity noted by owner.

Surgical Considerations

• Intracranial pressure dynamics is the most important consideration for the patient prior to performing a craniotomy.

• Monroe-Kellie Doctrine: the contents of the cranial vault are blood, CSF, and parenchyma- an increase in any of these 3 results in a net decrease in the other 2 components.

Surgical Considerations (cont.)

• Pre-operative steroid administration– Dexamethasone: to reduce edema and CSF production– Sodium prednisolone succinate or methyl prednisolone

succinate- antiinflammatory and tissue protective as oxygen free radical scavengers and stabilizers of the lysosomal membranes.

– Micah: solu-delta cortef• Prophylactic antibiotic usage– To decrease CNS bacterial contamination– Micah: cefazolin

Craniectomy

• Sternal recumbency • Transfrontal approach

Post-operative • Critical care• Monitoring:

– Check heart rate, respirations, and blood pressure every two hours.– Flip sides every four hours, as well as ice pack incision every 4 hours.– NPO– LRS- 70 ml/hr

• Medications: – Cefazolin– Lasix– Buprenorphine– Phenobarb– Levothyroxine– Midazolam– Domitor– Famotidine

Post-operative

• Walked outside with assistance day 1• NPO• Began offering food on day 2 and switched to

oral antibiotic and pain control • Spiked a fever on day 3 but was controlled

easily, received surgical histopathology results• Gradually increased food intake and walking

distance

Meningioma

• Most frequent CNS tumor seen in vet med• MST

– Surgical excision followed by radiation therapy- 16 mo.– Surgical excision alone- 11 mo. – No treatment- variable – could be weeks to months.

• Breed predilection: dolicocephalic • Age predilection: mature adults• Behavior- generally benign• Location: usually solitary

– Cerebrum> cerebellum> spinal cord>ventricles

August 30, 2009- Micah goes home!

Recheck-9/14/09

• BAR, incision healing nicely• Neurologic examination- inconsistent right eye

menace response and droopy right eyelid• Owner reported Micah to be weak in his rear

limbs• Pretreatment CT for radiation therapy

10/2/09

• Micah is receiving his 13th of 16 fractions of radiation today.

• He is doing great with no abnormalities thus far!

Thank You…..

Phil. 4:13- “I can do all things through Christ who gives me strength.”

•God•Family•Micah•Dr. Ortinau and Dr.Shores•Class of 2010•Gran 1932-2009