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Summary epilepsy notes
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notes on epilepsy (diagnosis, symptoms, management)
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Epilepsy Common neurological disorder where there is a tendency to have seizures
that start within the brain.
In the case of epilepsy, regular low-frequency discharges are replaced by
bursts of high-frequency discharges usually followed by periods of inactivity.
This abnormal discharge may remain localised or it may spread to adjacent
areas, recruiting more neurones as it expands.
It may also generalise throughout the brain via cortical and subcortical routes,
including collosal and thalamocortical pathways.
The area from which the abnormal discharge originates is known as the
epileptic focus.
Official definition
1) At least 2 unprovoked (or reflex) seizures occurring more than 24 hr apart
2) One unprovoked seizure and a probability of further seizures similar to the general
risk of recurrence (at least 60%) of two unprovoked seizures, occurring over the next
10 years
3) Diagnosis of an epilepsy syndrome
Epilepsy is not a diagnosis in itself but is a consequence of a wide variety of
cerebral diseases.
What is a seizure
Uncontrolled and excessive synchronized (more than one neuron firing AP’s
simultaneously) electrical activity of central neurons
Recurrent, rhythmic and repetitive disorderly discharge of nerve tissue that
may be caused by any pathological process which affects the cortical layer of
the brain.
Seizures can occur in response to practically any generalised metabolic
disturbance or cerebral pathology.
Causes
Enhanced excitatory neurotransmitter release – glutamate, particularly
Reduced inhibitory neurotransmitter release – GABA
Altered ion channel function in neurons leading to modified action potential
firing
Changes in balance between excitation and inhibition (favours
excitation)/EPSP’s neurons more likely to trigger AP synchronised activity
In an epileptic patient
- different amounts of VG channels e.g. excessive VG-Na+ channels AP’s
triggered more easily more susceptible to seizures
- or e.g. reduction in VG-K+ channels (same effect as above)
CNS diseases causing epilepsy and seizures
, Congenital – present from birth (e.g. brain damage)
Degenerative e.g. Alzheimer’s
Infective e.g. cerebral TB, HIV, cerebral malaria, viral encephalitis, meningitis,
cerebral toxoplasmosis, neurocysticercosis
Trauma
Tumour (brain) – (Intracranial mass lesions)
Cerebrovascular disease e.g. stroke
Systemic disturbances causing epilepsy and seizures
Fever
Hypoxia – low oxygen levels
Glucose disturbances
Electrolyte imbalance
Organ failure
Toxins
Drugs and drug withdrawal e.g. ciclosporin, lidocaine, quinolones, tricyclic
antidepressants, antipsychotics, lithium, stimulant drugs such as cocaine
Withdrawal of antiepileptic drugs (especially barbiturates) and
benzodiazepines
Vitamin deficiency
Metabolic abnormalities e.g. hyponatraemia, hypocalcaemia, hepatic
encephalopathy, porphyria
Alcohol withdrawal
Alcohol induced hypoglycaemia and head injury
Epilepsies can be defined as:
1) Genetic (previously known as ‘idiopathic’).
- Seizures are caused by a known or ‘presumed’ genetic defect that is
diagnosed. NB Even if there is a genetic cause, environmental factors may
still contribute to the expression of the disease
2) Structural/metabolic (previously known as ‘symptomatic’ or ‘acquired’).
- Causes are factors such as high temperature (fever), stroke, tumour,
infections, trauma; i.e. non-genetic. Again, genetic factors may also contribute
to this form but are not the primary cause of the disease
3) Unknown
- The underlying cause is not identified. It may be genetic or secondary to other
disorders.
Diagnosis of epilepsy
Witness accounts – what happened before, during and after attack
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