Canine & Feline Epilepsy Flashcards
What is the main cause of seizures?
neuronal excitability
- inadequate inhibition - high GABA
- excessive excitation - high glutamate
- neuronal synchronization
- genetic factors influencing ionic gradients
What cells are responsible for maintaining the resting potential and ionic charges of neurons?
glial cells control action at Na/K ATPase and the effect of excessive discharge on other cells
What is resting membrane potential?
at equilibrium, electrical gradients counteract the concentration gradients for K+
What is the Nernst equation?
calculates the membrane potential at which specific ions will be at equilibrium on both sides of a membrane
- K+ = -80 mV
- Na+ = 62 mV
- resting potential = -70 to -90 mV = cell is a K+ battery
What causes local currents created by neurons?
ATPase is activated, causing 2 Na+ molecules to move into the cell (depolarizing it) and K+ moves out
What are EPSP and IPSP?
fluctuations in membrane potential around resting potential average
- EPSP = excitatory post-synaptic potential = depolarization
- IPSP = inhibitor post-synaptic potential = hyperpolarization
What makes up the BBB? What is its function?
capillary endothelial tight junctions and astrocytic perivascular end-feet on endothelium
limits the entry of large molecules into the brain, acting as a transcellular transport system using P-gp, coded by ABCB1 (MDR1) gene
What are 5 causes of increasing seizure activity over time?
- kindling and mirroring
- neuronal plasticity
- formation of recurrent circuits by axonal sprouting
- calcium currents
- gliosis in epileptic foci, causing the loss of K+ buffering capacity
What is the most common genetic cause of epilepsy?
polygenic mutations identified in dogs
- MDR1 gene mutation in Border Collies
What is the difference between focal and generalized seizures?
FOCAL = affect part of the brain, resulting in convulsions in one side of the body, difficult to control
GENERALIZED = affect the entire brain, resulting in entire body convulsions; typically have a focal component that is not observed
Is there a test for epilepsy?
NO
- r/o extracranial causes
- history and signalment are key
- neurologic examination
- imaging (not commonly done, $$$)
What age is most commonly affected by idiopathic epilepsy?
1-5 years old
- not absolute: juvenile and late-onset epilepsy exist
When do most dogs with idiopathic epilepsy seizure?
while at rest - morning and evenings most common
- typically are normal between episodes (may be anxious0
How do seizures change with no/inadequate therapy?
commonly increase in frequency and duration
What imaging modality is preferred for diagnosing epilepsy? Why?
MRI - provides superior soft tissue detail
- CT gives details on the bone. acute hemorrhage, and post-operative implant assessment
