W19 Epilepsy Flashcards
(46 cards)
What is epilepsy?
- Anyone can have an isolated seizure – this is NOT the same as having epilepsy
- Epileptic seizures occur when ordinary brain activity is disrupted spontaneously and recurrently
What is the definition of a seizure?
“A transient paroxysm of uncontrolled discharges, beginning at the epileptic focus, causing an event which is discernible* by the person experiencing the seizure and/or an observer”
*able to be seen or understood
Prognosis of Epilepsy:
(chance of treatment success)
- Good
- 70-80% of patients become seizure-free
- About 50% successfully withdraw their medication
- 20-30% have chronic epilepsy
- Usually normal function between seizures
- 5% will not be able to live alone
Mortality in Epilepsy:
Increased by?
- Increased by 2-3 times due to:
- Accidents
- Status epilepticus
- Tumours
- Cerebrovascular disease
- Pneumonia
- Suicide
(SUDEP – sudden unexpected death in epilepsy)
Causes of Epilepsy? (7)
*Cause now identified in ~50% of people globally
*Most common defined causes:
–cerebrovascular disease
–cerebrovascular tumours
–genetic, congenital, or hereditary conditions
–alcohol
–drugs and toxic causes
–head trauma (including neurosurgery)
–post-infective causes (encephalitis/meningitis)
What are the risk factors for Seizures? (9)
*Disturbed levels of water/electrolytes
*Disturbed levels of blood glucose
*Altered blood gases
*Raised body temperature
*Altered sleep patterns
*Hormonal disturbance
*Toxicity
*Heredity
*Tumours
How is epilepsy diagnosed?
- Difficult
- Unpredictable and transient
- Need a reliable account
- Use of EEG, MRI and/or CT
– not conclusive alone - Seizures MUST be recurrent and spontaneous
- EEG records abnormal electrical discharges
- Has limitations
– 5% of people without epilepsy have abnormal EEG
– 40% of people with epilepsy have normal EEG between attacks
Features of Epilepsy:
- Sudden, excessive high frequency neuronal discharge
- Highly synchronous discharges- Not random
- A disorder of the cerebral cortex
- May be loss of consciousness
- Behavioural changes related to site of discharge (focus)
What is an EEG?
What are some other imaging techniques?
Electro-EncephaloGraphy (EEG)
Electroencephalogram - EEG
* Records the activity of populations
(many thousands) of neurones
* reveals synchrony of neuronal activity
- MEG (Magnetoencephalography)
- PET (Positron emission tomography)
- MRI / fMR
Seizure Types
what is it based on?
2 main groups:
- Based on the description of events and EEG
- Classified according to the international scheme:
1. Generalised- whole brain
2. Focal (previously referred to as “partial”)
-involves small part of brain
What are the different types of generalised seizures? (6)
Absence
Tonic-Clonic
Myoclonic
Clonic
Tonic
Atonic
Generalised Seizures
1. Tonic-clonic Convulsions (Grand Mal)
What are the features?
*Most common form
*Patient stiffens, falls and convulses
*Laboured breathing, hyper-salivation
*Cyanosis, tongue biting and incontinence
*Lasts a few minutes
*Followed by headache and drowsiness
Generalised Seizures
Tonic and Clonic seizures:
What are the features of tonic?
What are the features of clonic?
Tonic seizures
* stiffening of body – head, trunk +/- limbs
Clonic seizures
* rhythmic, motor, jerking movements
* +/- impairment of consciousness
* simultaneous involvement of arms and legs
Generalised Seizures
4. Absence Attacks (Petit Mal)
What are the features?
- Rarer; almost exclusively in childhood and early adolescence
- Goes blank, stares, eyelids flutter, head flops
- Last a few seconds
- Child may not be aware of it
Generalised Seizures (5)
Describe a Myoclonic Seizure? (Abrupt)
- Abrupt, brief, involuntary, shock-like jerks
- Involve head, limbs or whole body
- Recovery immediate
- Not always epilepsy
Generalised Seizures
6. Atonic Seizures
- Sudden loss of muscle tone
- Quick recovery
- Very rare
Focal Seizures (also sometimes called Partial Seizures)
1. Simple Focal/Focal Aware Seizures (retains awareness)
What are the Features? (5)
abnormal discharge?
- Abnormal discharge remains localised
- Consciousness not impaired
- What happens depends on area of the brain
- Will vary from person to person
- Will be the same each time in each person
Focal Seizures
Complex Focal/Focal Altered-awareness Seizures (altered awareness)
Features?
- ‘automatic’ behaviours
- confusion
- apparent drunkeness
Focal Seizures:
Secondarily Generalised Seizures
- Simple or complex focal seizures
– then spread to the whole brain
– leads to tonic-clonic attack - May be a warning ‘aura’
– symptoms of the partial seizure
What is Status epilepticus?
- Serious uncontrolled seizure
- Convulsive (tonic-clonic) status epilepticus
- A tonic-clonic seizure lasts for 5 minutes or more, or
- One tonic-clonic seizure follows another without the person regaining consciousness in between
Which areas do seizures arise in the brain?
- Anywhere
- subcortical rare (thalamus: absence)
- mostly cortical
– frontal, parietal, occipital, temporal -
Temporal most prevalent - 30-40%
– Hippocampus, entorhinal cortex,
amygdala
– Most common seizures that are drug refractory
– Surgical resection
Imaging in epilepsy: Susceptible regions and levels of activity
what do PET,MRI and fMRI scans monitor?
MRI- Hippocampus is larger on LHS and smaller on RHS
* PET – monitors local metabolism
* MRI – structure and volume
* fMRI – relates activity to structure
How do seizures arise?
*Cortical activity - dynamic balance between inhibition and excitation
Two levels of control
*Intrinsic or level of individual cell: determined by ion channels (in neurons)
* At a Network level- controlled by synaptic
transmission
Disturbed balance - excessive synchrony and epilepsy
* INC excitation, normal inhibition
* DEC inhibition, normal excitation
* DEC inhibition, INC excitation
WHAT IS THE MAIN CNS…
EXCITATORY NEUROTRANSMITTER?
INHIBITORY NEUROTRANSMITTER?
Glutamate
GABA
