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Epilepsy:

  • It is a condition where there are paroxysmal, self-limited functional cerebral disturbances characterized by abnormal electrical activity of brain.
  • It leads to signs known as ‘seizure’, ‘fits’ or ‘convulsion’.
  • Each attack is characterized by sudden loss of consciousness.
  • It is most common chronic neurological disorder in veterinary medicine and affects upto 1% dogs and 2% cats in general population.
  • Seizures are clinical manifestations of excess and hypersynchronous electrical activity in the cerebral cortex.

 

Classification of Epilepsy:

  1. According to Etiology
  2. According to Nature of Fit (Clinical)

 

  1. According to Etiology:

Based on etiology, it is of two types:

  1. Idiopathic epilepsy:
  • In this type there is no definite causes.
  • In majority of cases, hereditary history is present.
  • There may be some kind of metabolic disturbances.
  • It is genetical and age dependent.
  • Certain breeds are predisposed to this type of epilepsy.

 

  1. Symptomatic epilepsy:
  • this type of epilepsy denotes physical, physiological and inflammatory derangements.
  • It is common in cats.
  • This type of epilepsy is result of one or more identifiable structural lesion of the brain.

 

  1. According to Nature of Fit (Clinical):

Based on nature of fit, it is of two types:

  1. Generalized epilepsy:
  • In this type of epilepsy, abnormal electrical discharges spread all over the brain.
  • It reflects involvement of both hemisphere of cerebral cortex.
  • It is of further 3 types:
    • Grand mal (Major epilepsy)
    • Petit-mal (Minor epilepsy)
    • Status epilepticus

 

  1. Focal epilepsy:
  • In this type, abnormal electrical discharge is localized to a particular part of brain (cerebral hemisphere).
  • It may be:
    • Temporal lobe epilepsy
    • Jacksonian epilepsy
    • Myoclonic epilepsy
    • Akinetic attack or focal fits

 

Etiology:

  • Traumatic injury of cranium
  • Degenerative changes in brain
  • Congenital malformation of brain
  • Space occupying lesion (cyst, tumor, abscess)
  • Meningitis, encephalitis
  • Otitis media
  • Metabolic disturbances: Diabetes mellitus, uremia, hepatic coma, alkalosis, hypocalcemia)
  • Fever- febrile convulsion, febrile fit
  • Cardiac disorder- aortic stenosis, pulmonary stenosis, myocardial infarction, etc
  • Canine distemper, Cryptococcosis
  • Round worm infestation, tapeworm infestation
  • Toxin- Bait, mycotoxin, spoiled feeds
  • Hypoglycaemia
  • Hydrocephalus

 

Stages of epilepsy:

  1. Stage of aura:
  • It is the first stage. It is warming signal indicating that the fit is coming.
  • The animal shows the expression that some danger is coming
  • It persists for few seconds.
  • Animal remains conscious but doesnot possess voluntary power.
  • Type of aura depends on site of abnormal electrical discharge. It may include:
    • Motor aura: twitching and convulsion of angle of mouth
    • Sensory aura: peculiar sensation on body
    • Visual aura: visual hallucination, vacant look

 

  1. Stage of prodromal (unconsciousness):
  • It follows the stage of aura
  • Animal becomes still and unconscious.

 

  • Stage of ictus (convulsion):
  • It has got two phases; tonic phase and clonic phase
  • In tonic phase, suddenly the muscles of whole body are thrown into tonic spasm and animal will fall on ground.
  • This phase may be characterized by deviation of eyes, epileptic cry, temporary stoppage of respiration, cyanotic condition, rapid pulse and abnormalities in limbs.
  • In clonic phase, there is convulsion of all muscle groups including limbs. This may be characterized by pedaling movements.
  • Initially clonic convulsion occurs at regular frequency but gradually becomes longer at intervals and ultimately ends with final jerk and passes into stage of flaccid coma.
  • Ictus phase is characterized by;
    • Tongue biting
    • Hypersalivation (blood stained froth from mouth and nostril)
    • Urination
    • Defecation
    • Pupillary dilatation
  • It may last from few seconds to a few minutes

 

  1. Stage of post-ictus (post-convulsive):
  • Following clonic phase, animal regains its consciousness but not the full functions of nervous control.
  • It may show flaccidity of muscles, depression, fatigueness, incoordination of gait and blindness.
  • It may remain from few seconds to few days.

 

Clinical Signs:

  • Stiffening of neck and legs
  • Stumbling and falling over
  • Uncontrollable chewing, drooling
  • Paddling of limbs
  • Loss of bladder control, defecation
  • Vocalizing
  • Violent shaking and trembling
  • It lasts for about 30-90 seconds and animal is typically unaware of its surroundings

 

Diagnosis:

  • Based on history of traumatic injury or other metabolic disturbances
  • Based on clinical signs
  • Based on normal neurologic examination
  • Brain MRI and EEG
  • Spinal fluid analysis

 

Differential Diagnosis:

Causes within 6 months of age:

  • Juvenile epilepsy: Unknown etiology. Young dogs used to suffer. Cocker spaniel suffers the most. Phenobarbital therapy may give satisfactory result.
  • Inflammation induced epilepsy: Canine distemper, Neospora caninum, fungus, bacteria and coli may cause epileptic seizure.
  • Toxin induced epilepsy: Bait, mycotoxin, spoiled feeds may cause epilepsy. Diazepam @0.5-1 mg/kg, IV may be of help
  • Traumatic epilepsy: Brain trauma causes epileptic seizure.
  • Hypoglycaemic epilepsy: Abrupt fall in blood glucose level may produce epilepsy in toy breeds of dog.
  • Hydrocephalus predisposed epilepsy
  • Hepatic encephalopathy induced epilepsy: Generalized tonoclonic seizure may be the feature

 

Causes within 6 months- 5 years of age:

  • Idiopathic- Genetic epilepsy
  • Infectious: Viral, Rickettsial, Parasitic, Bacterial, Protozoal, Fungal
  • Non-infectious: Granulomatosis, Immune-mediated, Breed specific
  • Tumors

 

Causes in more than 5 years of age:

  • Symptomatic causes: Metabolic disturbances, degenerative changes in brain, congenital malformation of brain
  • Inflammatory disease
  • Thalamocortical tumour
  • Encephalopathy
  • Beta cell tumour

 

Treatment:

  • Except with head trauma, starting of antiepileptic drugs (AED) is not recommended.
  • Patients should be started with AEDs in case of status epilepticus or cluster seizures (>1 seizure, q24h) or if long-term control is necessary (i.e. 1 seizure q4-6 weeks)
  • As in any emergency, airway, breathing and circulatory disturbances should be corrected first.
  • First line of drug for seizure is typically benzodiazepines; diazepam or midazolam administered IV or double dose. Diazepam @ 0.5-1 mg/kg/IV
  • If seizure persists, phenobarbital is administered @2-5 mg/kg, BID. PB is added to DZ @2-10 mg/hour
  • Status epilepticus requires rapidly increasing blood levels or loading the patient with a long-term AED by injection to rapidly reach therapeutic blood levels; phenobarbital is often the first choice
  • Propofol is given to patients that fails to respond to benzodiazepines or as first line agent to arrest status epilepticus in patients with post-stroke seizure (PSS).
  • Levetiracetam is immediately effective with few adverse effects and has become widely used in veterinary medicine.
  • Bromides (potassium bromide, injectable sodium bromide) may also be administered as long-term AEDs in dogs only.

 

Common Medications for Treatment of Epilepsy:

No description available.

 

Some Guidelines for Therapy:

  • Maximum dose should be given initially
  • No drugs should be withdrawn suddenly.
  • Replacing of one drug by other should not be done overnight but be done gradually.
  • Drug should be continued for few days after the last attack.
  • More dose may be given in the evening rather than morning.

 

Drugs contraindicated in epilepsy: Phenothiazine derivative tranquilizer e.g., Chlorpromazine (Largactil), Trifluopromazine (Siquil), etc. are not to be used against epilepsy as they activate the epileptic brain.

 

Dog Breeds Predisposed to Epilepsy:

No description available.

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