2.0 Seizures and Epilepsy

Question 1

What is epilepsy?

Answer 1

seizures are symptoms not a diagnosis; epilepsy is simply the predisposition of an animal to have seizures

seizures are clinical manifestation of excessive and hypersynchronous neuronal activity

• they are characterized by a neuronal imbalance (increased excitation and/or decreased inhibition)
• a paitent may be considered to have epilepsy if there are at least 2 unprovoked seizures >24 hours apart

Question 2

What are the phases of a seizure?

Answer 2

1. aura: often involves alterations in smell, taste, visual perception, hearing, and emotional state; not always recognized in our patients
2. ictal phase: the time from the first symptom to the end of the seizure activity; seizures are typically either focal or generalized
3. post-ictal phase: follows a seizure → drowsiness and confusion are commonly experienced during this phase

Question 3

How are seizures classified by semiology?

Answer 3

seizures may be

• generalized
• focal
• focal with secondary generalization

Question 4

Differentiate generalized from focal epileptic seizures.

Answer 4

generalized epileptic seizures:
bilateral involvement of cerebral hemispheres; as a rule the animal loses consciousness during convulsive epileptic seizures; often involves autonomic dysfunction (urination, defication)

may be:

• tonic: sustained increased muscle contraction
• myoclonic: sudden, brief, involuntary contractions of muscles or muscle groups
• clonic: prolonged, regular and repetitive myoclonic contractions
• atonic: sudden loss of muscle tone of few seconds duration

focal epileptic seizures are characterized by lateralized and/or regional signs

can present as:
1. focal motor: motor events or automatisms (movements that resemble voluntary motor activity such as chewing). The level of consciousness is usually unaffected
2. focal sensory: behavioral seizures often involving the limbic system (rage/aggression, vocalization, fly-catching, tail chasing)
3. focal autonomic: rare, may present with vomiting, diarrhoea, drooling

*differential diagnosis: OCD

Question 5

How are seizures classified by eitiology?

Answer 5

seizures may be

idiopathic (intracranial)

• overarching term (genetic, or of unknown cause)
• normal metabolic, physical, and neuro exam in interictal period
• generalized tonic clonic most common
• 3 teirs based on level of confidence (I is blood/urine only, II adds intracrainial. imaging, III adds EEG)

structural (intracranial)

• provoked by intracranial pathology (degenerative, neoplastic, inflammatory, etc)
• 87% have abnormal neuro exam durin interictal period
• metabllically normal
• may be focal or generalized

reactive (extracranial)

• seizure in response to transient disturbance
• NOT a form of epilepsy, as not predisposed
• metabolic or toxic
• abnormal neuro exam consistent with diffuse forebrain involvement (signs may wax and wane)
• systemic signs may accompany
• most common: intoxications (39%) and hypoglycemia (32%), followed by electrolyte disturbances (11%) and HE (9%)