Case 13- Epilepsy Flashcards
Epileptic seizures
They tend to be transient in nature and present with a variety of signs and symptoms. The symptoms depend on what part of the brain is being affected. The type of epilepsy is based on the age of onset, type of seizure, specific EEG characteristics. This has implications for treatment, management and prognosis
Categories of epileptic seizures
1) 3 main types: focal onset, generalised onset and unknown onset.
2) Generalised onset seizures are classified into 2 major categories: motor and non-motor. Generalised seizures affect both hemispheres of the brain.
Non-motor generalised seizures
Main type is Absence seizures. Brief episodes of impaired consciousness with no aura or postictal confusion. They last up to 20 seconds and are accompanied by few or no automatisms. Of the automatisms that develop, the facial ones are common, with repetitive blinking. Hyperventilation or photic stimulation frequently precipitates these seizures, which typically begin during childhood or adolescence and may persist into adulthood. Absences seizures can be typical, atypical, myoclonic or with eyelid myoclonia. No physical convulsions.
Main types of generalised motor seizures
1) Tonic-clonic seizures
2) Myoclonic tonic-clonic seizures
3) Myoclonic-atonic seizures
4) Clonic seizures
5) Tonic seizures
6) Atonic seizures
Generalised motor seizures= Tonic-clonic seizures
Known as grand mal seizures. They consist of several motor behaviours - generalized tonic extension of the extremities lasting for few seconds, followed by clonic rhythmic movements and prolonged postictal confusion. Most common motor form of seizure, whole body stiffness followed by rhythmic movement. Loss of consciousness.
Generalised motor seizures= Myoclonic tonic clonic seizures
Begins with a few myoclonic jerks followed by tonic–clonic activity. The initial jerks can be considered to be either a brief period of clonus or myoclonus. These seizures are commonly seen in patients with juvenile myoclonic epilepsy and occasionally with other generalized epilepsies.
Myoclonus
Spasmodic jerky contractions of a group of muscles
Clonus
A rhythmic, oscillating, stretch reflex,
Generalised motor seizures= Myoclonic atonic seizures
Involves brief jerking of limbs or trunk (myoclonic jerk) due to muscle contractions, followed by a limp drop (atonic component). These seizures, previously called myoclonic-astatic seizures, are most commonly seen in Doose syndrome but can also be encountered in Lennox-Gastaut and other syndromes.
Clonic seizures
Consists of rhythmic jerking motor movements with or without impairment of consciousness. They can have a focal origin too.
Tonic seizures
Sudden-onset tonic extension or flexion of the head, trunk and/or extremities for several seconds. These seizures typically occur in relation to drowsiness, shortly after patients fall asleep, or just after they awaken. Tonic seizures are often associated with other neurologic abnormalities. Brief loss of consciousness, body stiffens
Atonic seizures
Also called “drop attacks.” These seizures occur in people with clinically significant neurologic abnormalities and consist of brief loss of postural tone, often resulting in falls and injuries. Brief loss of consciousness, become limp.
Focal seizures
Where a burst of activity is limited to one part of the brain
Classification of focal seizures
Can be classified into with preserved or impaired awareness. These can further be spilt into motor and non-motor. Motor includes automatisms, atonic, clonic, myoclonic, tonic and hyper kinetic and epileptic spasms. Non-motor examples are autonomic, behavioural, cognitive, emotional and sensory.
Simple focal seizure
Muscular jerks or altered sensation in one arm/leg. Odd taste, do not lose consciousness or awareness.
Complex focal seizures
Often starts in the temporal lobe. May behave oddly- mumble, wander, handle objects. May have odd emotions, fear, visions or sensations.
Link between focal seizures and generalised seizures
Focal seizures may develop into generalised seizures
Categorisation of unknown onset seizures
Can be classified into motor, non-motor and unclassified
Causes of epilepsy
Tend to be unknown, may have a genetic component, there doesn’t tend to be any other neurological conditions associated with it. Unknown/idiopathic epilepsy tends to respond well with treatment.
Symptomatic epilepsy
Tends to present from birth or develop later. Can be caused by scar tissue, neoplasia, infarction or heat in the brain. Causes abnormal depolarisation in the brain
Epileptic triggers
Dont cause epilepsy but make seizures more likely. Triggers- stress, drugs, tiredness, low blood glucose, alcohol and flickering lights.
Pathology of epilepsy
Na+ channel inactivated state helps prevent repetitive firing during a seizure. Depolarisation and Na+ entry causes a seizure. Abnormalities in Na+ channels (excessively stimulated or open for a long time) can cause seizures.
Epilepsy- Neuronal signalling
Balance between excitatory (glutamate) and inhibitory (GABA) control.
Surround inhibition
Prevents spread of activity (GABA) but also amplifies local signal. Abnormal activation will not spread to further sites. The surround inhibition is made of GABA neurons, when activated they release chlorine into the cell stopping the depolarisation by increasing the negative charge. The activated circuit in the centre will amplify signals but it is surrounded by an inhibitory surrounding which decreases signals.
Cause of all seizures
Caused by abnormal synchronous discharge due to a failure of protective mechanisms
Causes of focal seizures
Due to a sudden depolarisation ‘Paroxysmal Depolarising shift’ in a group of neurons. Depolarised for a long period of time (200ms). Causes a sustained level of abnormal depolarisation. Surround inhibition may limit spread, you will still be able to see it on an EEG. If the surround inhibition is not effective the depolarisation will travel to different parts of the brain causing a seizure.
