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