Epilepsy Flashcards
What causes a seizure?
Abnormal, synchronous activation of large numbers of hyperexcitable neurons which are connected in networks.
An imbalance between excitation and inhibition
They spread through synaptic and non-synaptic pathways.
How do you classify seizures?
Focal (part of the brain) or generalized (most of both hemispheres of the brain).
What are the manifestations of focal seizures?
Focal seizure manifestations: depends on where in the brain, can be focal motor, visual, somatosensory, auditory, psychic. Focal aware seizure (conscious and can notice seizure). Unconscious but on autopilot.
What are the manifestations of generalized seizures?
Generalized seizures manifestations: can be tonic (stiff), clonic (jerking), tonic/clonic (stiff then jerking), myoclonic (sudden jerk), atonic (lose all tone and fall), myoclonic-astatic (jerk and then fall), absence (loss of consciousness without fall), atypical absence seizures
What are the types and features of glutamate channels?
They are excitatory. There are NMDA receptors and non-NMDA receptors. The non-NMDA receptors (AMPA and kainate) allow most cations to pass through once activated once bound by glutamate. However, it is not very selective for Ca2+, mostly for Na and K. They are fast acting.
The NMDA receptors are slower and are voltage and ligand gated. They are more selective for Ca2+. Mg2+ sits in the channel and will only be removed when the neuron depolarized.
The non-NMDA receptors are activated first, allow Na and K to enter causing voltage change, this allows the NMDA receptors to open and Ca2+ to enter.
What channels are involved in epilepsy?
Can have voltage gated K+ channels involved, this is benign in infants because the channels change at 3 months of age and the seizures stop.
Voltage gated Na channel involvement is more severe (Dravet’s syndrome; sever monoclonic epilepsy of infancy). Other types too.
Mutations of voltage gated Ca2+ channels in the thalamus causes absence seizures. Hyperpolarisation of the thalamic relay neurons causes synchronous depolarization of the cortex via excitatory neurons.
Mutations of ligand gated ion channels, nicotinicacetylcholine receptors = frontal lobe epilepsy. GABA receptors
What are some drugs that can cause epilepsy?
Penicillin - blocks GABA channels
Glutamate receptors activation - dominic acid, unblocking Mg from NMDA receptors
What are some treatments for seizures?
Na channel blockers: they stabilize the Na channels reducing the number activated at a given voltage: Phenytoin, sodium valporate, carbamazepine
Enhancement of GABA transmission: diazepam, sodium valporate, barbituates,
Drugs that act on Ca channels: for absent seizures, sodium valporate, ethosuxamide.
Blocks glutamate transmission:
What is the impact of seizures on the brain?
Can cause some neurons to die and others to form inappropriate connections.
