Seizure Disorders/Epilepsy

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Seizure Disorders/Epilepsy

Group of disorders due to excessive depolarisation/excitability of groups of cerebral neurons that remain localised or spread to cause a general seizure. Affects about 1% of population (up to 5-10% of the population will have at least one seizure during their lifetime). Almost any condition that affects the grey matter of the brain can cause epilepsy. From the Greek word epilepsia (taking hold or seizing).

Seizures are produced by abnormal synchronisation of cortical neurons that result in a change in behaviours or perceptions. Epilepsy is the state of recurrent seizures caused by a brain abnormality.

Primary epilepsy – no identifiable cause (up to 10%; onset in childhood or adolescence)
Secondary epilepsy – seizure is due to identifiable cause (almost any disorder that affects the grey matter can cause a seizure): eg genetic (storage diseases, inborn errors of metabolism); drugs (eg penicillin, antimalarials, cyclosporin, lignocaine psychotropic agents); alcohol; cerebral birth injury; infection (eg meningitis); metabolic diseases (eg hypocalcaemia, hyponatraemia, hyperglycaemia, renal failure) inflammatory disease (eg SLE); space occupying lesion (eg tumour)

Aura – a sensory or psychic manifestation that precedes a seizure.

Two main groups of seizure:
1) Partial
clinical features are due to a small local/discrete part of brain affected and how much it spreads
simple partial seizures are confined to one part of brain; do not spread; usually short; usually abrupt onset and offset; remain conscious; tingling and numbness sensations; seizure is seen in a specific limb or muscle group (myoclonus) – Jacksonian seizure (frontal lobe), sensory (parietal lobe) or psychic (temporal lobe); no amnesia; most due to a structural lesion (eg tumour, vascular, infection)
complex partial seizures are more common; 50% arise in temporal lobe (temporal lobe seizure); 3 components – aura, loss/impairment of consciousness, confusion; initially may stare, then do purposeless movements, utter sounds; lasts for 30 secs to several minutes; autonomic features (pupillary dilation, salivation); amnesia of seizure

2) General:
start in local area, but spread to involve wide areas of both cerebral hemispheres
can be convulsive or non-convulsive; consciousness is almost always impaired
types of generalised seizures:
1) Tonic-clonic (grand mal) – the neuronal discharge spreads throughout entire cerebral cortex; the classical ‘epileptic fit’ with major convulsions with period of muscle rigidity (tonic phase) followed by period of synchronous muscle jerks (clonic phase); fall to ground; loss of consciousness; severe jerking movements of all skeletal muscles; excessive salivation; tongue biting; incontinence; vocalisations. After seizure  patient is disorientated, confused and exhausted (postictal state).
2) Absence (petit mal) – brief sudden self limiting loss of consciousness (5-30 seconds); stop what doing and stare blankly; may have rapid eye movements; no other motor activity; may not aware that are having an attack; can have as many as 100 attacks a day; usually begin in childhood (may be initially dismissed as ‘day dreaming’)
3) Myoclonic – sudden onset of short period of muscle twitching and jerking lasting for several minutes; limited to one limb/muscle (focal myoclonus) or whole body (massive myoclonus); consciousness not usually lost; rapid recovery without confusion; several types (Infantile spasms, Lennox-Gastaut syndrome, Juvenile myoclonic epilepsy)
4) Febrile – usually in young children with fever and no evidence of intracranial infection; typically a generalised tonic-clonic seizure; usually short duration; only small increased risk of developing other forms of epilepsy later in life
5) Status epilepticus (SE) – generalised repeated continuous tonic-clonic seizures without regaining consciousness or neurological function between attacks; defined as lasting > 30 minutes; life threatening medical emergency; can occur on withdrawal of antiepileptic drugs; considered a failure of seizure terminating mechanisms
6) Atonic – brief sudden loss of muscle tone; may be limited to neck muscles  head drop or if in muscles of trunk and limbs  suddenly collapse (“drop attack”); risk of injury from fall

Management:
Patient education (encourage normal life; exercise/activities encouraged; minimise alcohol consumption)
Education of family and co-workers (commonsense approach; avoid over protection; how to protect during seizure)
Restrictions (eg driving, dangerous machinery, working near open fires etc) until good control of seizures. Regulations may restrict driving and other activities.
Treat any conditions associated with seizures (eg hypertension)
Avoid precipitating factors

Pharmacological:
Tonic-clonic seizures  phenytoin, carbamazepine, sodium valporate, phenobarbitone, vigabatrin, gabapentin
Absence seizures  ethusuximide, sodium valproate, clonazepam
Myoclonic  sodium valproate, lamotrigine (for Lennox-Gastaut syndrome; ACTH, vigabatrin (for Infantile spasms); sodium valproate, phenobarbitone, clonazepam (for Juvenile myoclonic)
Status epilepticus  IV clonazepam, diazepam, phenytoin to terminate status

Surgical:
indicated for severe generalised seizures that produce falls and is intractable to pharmacological therapy
Resection of area of genesis of seizure.
Disconnecting procedures (usually corpus callosotomy).

Plasma levels of drugs need to be monitored and doses adjusted.

Outcome – after 5 years, 50% are seizure free without medication; 50% still continue with medication – of these 30% still have seizures.

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