Cellular Basis of Epilepsy Flashcards
What defines epilepsy?
Having 2 or more seizures, with an ongoing predisposition to further seizures
What is a simple partial seizure?
Aura - confined to limbic structures in temporal lobe
What is the focal discognitive phase of a seizure?
As the seizure spreads to conscious areas, the patient becomes unaware of automatic behaviours they are producing
What is a secondary convulsive seizure?
Involvement of the bilateral motor areas; horrible crying/moaning is typical, characterized by generalized limb stiffness followed by generalized limb jerking
What is epilepsy?
neurological condition with enduring alterations in the brain, resulting in abnormally increased predisposition to seizures
What can cause an acute symptomatic seizure?
trauma/head injury, drug intoxication, severe metabolic illness, stroke
What are the 3 major causes of epilepsy?
Genetic (idiopathic/primary), structural/metabolic (symptomatic/secondary to tumour, scarring, etc.), and unknown
How are seizures characterized?
Based on clinical features (representing the parts of the brain affected) and EEG findings
What are epileptic syndromes?
epileptic disorders with similar signs, symptoms, prognosis, and response to treatment
What are partial (focal) seziures?
starts in a geographically limited part of one hemisphere and may or may not spread to involve other parts of the brain - mostly arises from structural or metabolic abnormalities
What are generalized seizures?
arise simultaneously in both hemispheres, rapidly engaged bilaterally with widely distributed networks - usually genetic
What are the types of seizure?
partial (focal), generalized, and unclassifiable
What are the types of epilepsy?
genetic (idiopathic), structural/metabolic (symptomatic), and unknown
What is genetic epilepsy?
most common in childhood & teenage years; usually respond well to tx or remit; underlying brain is structurally and functionally normal, genetic basis such as ion channels
What is structural/metabolic epilepsy?
identifiable underlying structural or functional brain abnormality; not easily tx or remitting; more common as you age
What is a Jacksonian seizure?
starts in the motor cortex causing focal jerking of one hand that gradually spreads up the arm to involve the face and leg as it moves up the cortex
Epilepsy is primarily a disease of
cortical grey matter
What generates a seizure?
disturbance of the balance between inhibition and excitation of cortical neurons and neural networks (circuits can be small and localized or widely distributed and generalized) resulting in uncontrolled, hypersynchronous, self-sustained firing
What type of alterations in neuronal network components contribute to the mechanism of seizure?
loss of inhibitory neurons (esp. hippocampus; lost first); gain of excitatory neurons forming aberrant circuits; aberrant sprouting of severed axons; alterations in intrinsic neuronal excitability (ion channels); alterations in synaptic transmission; alterations in extra-neuronal environment (glial function in NT uptake)
What is the most sensitive brain structure to developing an epileptic network?
the hippocampus in the mesial temporal region
What is the most common cause of drug-resistant temporal lobe epilepsy?
Hippocampal lobe sclerosis
Epileptic remodelling in hippocampal sclerosis can include
cell loss (CA1), abnormal (mossy) fibre sprouting, excess proliferation of glial cells
Onset of epilepsy in infancy/early childhood is most commonly
congenital/perinatal CNS insult
Onset of epilepsy in late childhood/early adulthood is most commonly
idiopathic/genetic
Onset of epilepsy in adult/elderly (60+) is most commonly
symptomatic/structural
What is the basis of genetic causes of epilepsy?
multiple or several different polymorphisms in ion channels that result in a tendency to epileptic firing - VG and ligand-gates but also non-ion channel gated genes like structural elements
