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Seizure Management in Dogs 

The North Western Clin Path Club was treated to an excellent, practical and lively evening of CPD on Thursday 10th May. The principal speaker was Pip Boydell from the AMC, Manchester, whose talk was entitled ‘Philosophy of seizure management’.

Pip defined seizures as an increase in the electrical activity of the fore brain. Clinically there are four phases; prodrome, aura, ictus (the fit), and the postictus.  A number of owners are able to predict when a seizure is imminent.  This is extremely useful when it comes to preventing or mitigating the effects of an impending fit.

Pip listed the various causes of seizures in dogs viz.; metabolic, poisoning, CNS disturbances e.g.; trauma, tumours, rabies, toxoplasmosis, distemper.

Pip suggested that the vocalisation associated with seizures was more likely to be attributed to neurological disturbances rather than to pain.

History is vitally important viz:- age of the animal, frequency, duration and severity, any predisposing factors, the breed, and other clinical conditions eg; food allergy, video footage available, family lifestyle.

Investigations of all seizures require a full clinical examination, including a detailed neurological examination.  Base line data of haematology and serum biochemistry is preferable.  There was some debate as to include serology e.g. toxoplasmasis. CSF analysis is usually unremarkable and of little value. MRI scan (usually cost prohibitive) is the definitive procedure to eliminate or confirm cerebral lesions as a cause of seizures.  Pip commentated that often our medical colleagues do not perform such a detailed neurological examination sending patients directly for MRI investigation.  Confirmed cerebral lesions can be further investigated through biopsy, fine needle aspirate.  EEG is not normally helpful due to the problem of artefacts.

Pip defined epilepsy as ‘Seizures of undetermined origin’.  The primary origin may be inherited or secondary to CNS changes e.g. scaring, microscopic alterations, biochemical imbalances. 

Treatment fell into three categories a) As per the diagnosis eg Lyme’s Disease, Toxaplasmosis. b) Symptomatic. c) Client education.
The aim was to control seizures to a level the owners find acceptable.  This could be achieved by aiming to; reduce the frequency of attacks, reduce the duration of post ictal signs (very often owners do not like long lasting after effects), which suggests delaying treatment may exacerbate the problem later.

Pip posed the question ‘what was the worst case scenario?’  This prompted various suggestions including that of an on duty VS being contacted by a distraught owner with a vicious GSD having a status epilepticus!  However, there was general agreement that the worst case scenario was an ill prepared  owner having to witness a dog in status and then subsequently dying, and that it was the VS job to prepare owners for such an event.  Pip believed that seizures were not a welfare issue, neither was sedation of such clinical cases.  The philosophy was that the carer/owner receives the counselling and the dog receives the medication.

Drugs employed were –Diazepam- can be used to prevent a seizure (particular when diligent owners can predict the onset of a seizure) and to treat a seizure.  The preparation can be given orally as well as a rectal suppository.  Pip suggested that owners could use the latter route in those dogs under going a fit. 
Phenobarbitone- orally at 2mg/Kg bid. Aim for a serum level of 15-40?g/ml.
Potassium Bromide- per os 40-80mg/Kg.  (Reduce to 30-40 mg/Kg if used in conjunction with Phenobarbitone).  This is Pip’s first choice drug for seizures in young dogs.  Use in the cocker spaniel is not advised due to the possible induction of pancreatitis.  This drug takes longer to stabilise (> 2 weeks).  Serum levels of 1-3mg/ml should be aimed for.

Drug Monitoring - Efficacy is a very good measure.  Adjust the dose also according to any clinical side effects noted.  Serum levels allow the veterinary surgeon to monitor drug dosage, and help explain to owners drug dosage. However the important message was not to be too concerned about serum levels provided there is good clinical control with few side effects.

Side effects of the drugs were discussed.  These can include polyphagia, polyuria/polydypsia, aggression, neuropathy, GI upsets, toxicity (especially liver- which is usually irreversible).

Status Epilepticus. Treatment is often difficult especially when attempting to administer drugs i/v.  Rectal diazepam suppositories of 0.5mg/Kg are very useful.  If no response after 10 minutes repeat the medication.  If there is no further response then hospitalise.  Drugs employed are i/v phenobarbitone or pentobarbitone. Continuous use of propofol via a syringe driver may also be used.  Ventilation of these dogs with oxygen is very important.  Intracranial pressure doubles with hypoxia! Therefore intensive care needs to be very aggressive, requires a dedicated team and is very expensive.  Maintaining i) control of the airway (with muscle relaxation and mechanical ventilation), ii) control of haemodynamic function, iii) good venous drainage, are all essential.  Monitoring blood gases, blood pressure, blood oxygen, EEG? and the pupil all are vitally important.

Conclusion – Owners need to be ‘non stressed’ and be aware of the pathogenesis and prognosis of their individual pet’s condition.  They must become fatalistic and decide to what lengths their veterinary surgeon is to go to. BE PHILOSOPHICAL!

Geoff  Skerritt , in the audience, highlighted his experience with Epitard (a human drug used in Holland), which is a sustained release Phenytoin preparation.  This drug was acquired under a VMD special licence.  However its use to control epilepsy was disappointing, although useful for myoclonic epilepsy.

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