Neurotransmitter: Squirrel

The Clinical Management of Status Epilepticus

Squirrel is a 10 year old, male, castrated cat that presented to BVNS for persistent, intermittent 15 second seizures (non-responsive, left side facial twitching progressing to generalized twitching, salivation) despite treatment with multiple doses of valium and 10 mg/kg of phenobarbital. Squirrel’s examination suggested multifocal brain disease because there was a tendency to turn his head to the right, poor postural ability on right side, circling left, and a poor menace and poor palpebral response on the left. Infection, inflammation, or a neoplastic process were considered most likely.

Chemistry, CBC, and later, MRI, spinal tap, and infectious disease titers were all negative and treatment was initiated for infection (likely viral) and seizure. Squirrel was treated with zonisamide, levetiracetam, and phenobarbital as well as low doses of prednisolone and clindamycin. Thirty hours later he had the following story.

Presenting Complaint:

Fever, confusion, dull, non-ambulatory, intermittent eyelid twitching, squinting, and right head turn.

Assessment (Neurolocalization):

Mutlifocal brain disease was noted. Brainstem disease was suggested by weakness, dullness and poor palpebral response; right forebrain disease was suggested based on confusion and head turn. The patient was thought to be having a constant seizure (Status Epilepticus or SE) based on eyelid twitching and fever, however, there are many other causes for fever and eyelid twitching.

Diagnostics:

Dr. Mark Stecker, who is a physician, neurologist and world expert on EEG that has been helping Dr. Bush perform EEG for over 10 years, was asked to assist with Squirrel’s care.

An electroencephalogram (EEG) was recorded in a double banana montage and read real time by Dr. Cuff, Dr. Bush and Dr. Stecker. Dr. Stecker remotely viewed the EEG in order to provide ongoing feedback and consultation. This allowed us to titrate treatment to the dissipation of epileptiform activity with 100 mg/kg of phenobarbital. Phenobarbital was selected because barbiturates are the most useful drugs in this situation in people as opposed to diazepam, propofol or levetiracetam. The patient was intensely monitored (end tidal CO2, blood gas, blood pressure, ECG) but did not require cardiorespiratory support during the 12 hour loading with phenobarbital.

Outcome:

Squirrel developed serious heart disease and azotemia while being treated for SE. A heart murmur had been noted two years ago and current thinking is that this disease may have become clinical due to administration of low doses of fluids and prednisone or possibly related to the cardiovascular effects of the diluent in phenobarbital (a phenomenon reported in the 1940’s in people). After two weeks of intensive care from the Critical Care Service at TLC, CVCA, and BVNS, Squirrel was healthy enough to go home. Above he is pictured with the owners and Dr. Cuff. Squirrel is about two months out from his presumed severe viral brain problem and doing very well.

Take Home Points:

1. Status Epilepticus leads to death of inhibitory neurons, release of excitatory neurotransmitters and generates other pockets of abnormal electrical activity (kindling) leading to more seizure and occasionally death.

2. Patients can have active severe EEG seizure without any autonomic signs (salivation, urination, defecation, pupil dilation or constriction) and without obvious muscle movement.

3. Treatment of SE, ideally guided by the EEG, can require very high doses of phenobarbital.

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