Neurology Flashcards
Define epileptic seizure.
Excessive and/or hypersynchronous
neuronal electrical activity in the cerebral
cortex resulting in paroxysmal episodes of abnormal consciousness,
motor activity, sensory input and/or autonomic
function.
Define status epilepticus.
Continuous seizures, or two or more discrete seizures between which there is incomplete recovery of consciousness, lasting at least 5 minutes.
Define cluster seizures.
> 2 self-limiting seizures over a period of 24 hours. , The patients regain consciousness, or return to baseline central nervous system function, between seizures.
Define epilepsy.
Disease of the brain characterized by an enduring predisposition to generate epileptic seizures. This definition is usually practically applied as having at least two unprovoked epileptic seizures >24 h apart
How is epilepsy classified?
2 classifications:
Based on cause:
- Idiopathic
- Structural
Based on seizure type:
- Focal
- Generalized
What is the proposed mechanism behind the development of status epilepticus?
Excessive, sustained neuronal excitation and/or inadequate neuronal inhibition.
What happen when an action potential reaches an axon terminal?
Depolarization: voltage-gated Na channels open to allow influx of Na+.
The flow of Na into the cell leads to further depolarization of the memb, thus opening more Na channels in a positive-feedback loop.
Influx of Na into the cell results in opening of
calcium channels. Calcium enters the cell and causes release of the neurotransmitter.
Name some excitatory naurotransmitters.
Glutamate, aspartate, acetylcholine.
What is the major inhibitory neurotransmitter?
GABA
There are 4 recognizable stages of seizure activity, Name them.
- prodrome
- aura
- ictus
- post-ictal period
When a patient is presented for seizure, where is the anatomical localization?
Forebrain.
What role do NMDA receptors play in status epilepticus?
NMDA receptors become activated during continuous neuronal stimulation due to excessive concentration of glutamate - opening of Ca channels - large amounts of Ca2+ enter the neuron and induce a cascade of intracell neurochemical events that can kill the cells.
What are the areas of the brain that are more sensitive to the
detrimental effects of SE?
Pyramidal cells of the
hippocampus and the amygdala.
Describe the early (0-30min) and late (>30min) phases of status epilepticus.
Early:
- release of large amounts of catecholamines (=increased systemic,
pulmonary and LA BP, CVP and HR, increased susceptibility to cardiac arrhythmias)
- hyperthermia
- increased bronchial secretions and salivation
- decrease ventilation
- increase CBF
- lactic acidosis
Late:
- failure of body’s compensatory mechanisms
- hypoxia
- impaired cardiac ventricular function
- hypotension
- low CBF (due to hypotension)
- neuronal ischemia and cell death
- multiorgan failure (due to systemic hypoxia)
What are your differentials for status epilepticus?
Differentiate between reactive and intracranial/structural/idiopathic seizures:
- Reactive: toxic, metabolic
- Intracranial - can be divided into progressive and non-progressive:
Progressive: inflammation (e.g., granulomatous meningoencephalitis),
neoplasia, nutritional alterations (e.g., thiamine deficiency), infection,
anomalous entities (e.g., hydrocephalus), and trauma.
Non-progressive: idiopathic epilepsy, previously active
cerebral diseases such as infections and traumatic lesions that are no
longer active.
