epilepsy Flashcards
definition
recurrent tendency to spontaneous, intermittent, abnormal electrical activity in part of brain, manifests as seizures
prodrome define
- Not part of seizure
- change in mood or behaviour - may precede the attack by some hrs - days.
aura- define
- Part of seizure- patient aware
- Partial (focal) seizure
- Experienced as “Strange feelings”:
- epigastric rising - strange feeling in the gut
- déjà/jamais vu
- strange smells or flashing lights
post ictal period define
headache, confusion, myalgia, sore tongue
todds paralysis -define
- temporary weakness if focal seizure is in the motor cortex
dysphasia
focal seizure in temporal lobe
epidemiology
- Common presentation: childhood/adolescence
- Prevalence:
- active epilepsy in ~1%
- one or two seizures: 3-5% population
conditions associated with epilepsy
Epilepsy most commonly occurs in isolation although certain conditions have an association with epilepsy:
- cerebral palsy: around 30% have epilepsy
- tuberous sclerosis
- mitochondrial diseases
other causes of seizures
Febrile convulsions
- typically occur in children between the ages of 6 months and 5 years
- around 3% of children will have at least one febrile convulsion
- usually occur early in a viral infection as the temperature rises rapidly
- seizures are typically brief and generalised tonic/tonic-clonic in nature
Alcohol withdrawal seizures
- occur in patients with a history of alcohol excess who suddenly stop drinking, for example following admission to hospital
- chronic alcohol consumption enhances GABA mediated inhibition in the CNS (similar to benzodiazepines) and inhibits NMDA-type glutamate receptors.Alcohol withdrawal is thought to be lead to the opposite (decreased inhibitory GABA and increased NMDA glutamate transmission)
- the peak incidence of seizures is at around 36 hours following cessation of drinking
- patients are often given benzodiazepines following cessation of drinking to reduce the risk
Psychogenic non-epileptic seizures
- previously termed pseudoseizures, this term describes patients who present with epileptic-like seizures but do not have characteristic electrical discharges
- patients may have a history of mental health problems or a personality disorder
classification of seizures
- Where seizures begin in the brain
- Level of awareness during a seizure (important as can affect safety during seizure)
- Other features of seizures
define ‘focal’ seizure
Focal seizures
- previously termed partial seizures
- these start in a specific area, on one side of the brain
- the level of awareness can vary in focal seizures. The terms focal aware (previously termed ‘simple partial’), focal impaired awareness (previously termed ‘complex partial’) and awareness unknown are used to further describe focal seizures
- further to this, focal seizures can be classified as being motor (e.g. Jacksonian march), non-motor (e.g. déjà vu, jamais vu; ) or having other features such as aura
define generalised seizures
Generalised
- these engage or involve networks on both sides of the brain at the onset
- consciousness lost immediately. The level of awareness in the above classification is therefore not needed, as all patients lose consciousness
- generalised seizures can be further subdivided into motor (e.g. tonic-clonic) and non-motor (e.g. absence)
specific types include:
→ tonic-clonic (grand mal)
→ tonic
→ clonic
→ typical absence (petit mal)
→ myoclonic: brief, rapid muscle jerks
→ atonic
what does ‘unknown onset’ mean
this termed is reserved for when the origin of the seizure is unknown
define term ‘focal to bilateral seizures’
- starts on one side of the brain in a specific area before spreading to both lobes
- previously termed secondary generalized seizures
special forms of epilepsy recognized in children
Syndrome
Notes
Infantile spasms (West’s syndrome)
Brief spasms beginning in first few months of life
- Flexion of head, trunk, limbs → extension of arms (Salaam attack); last 1-2 secs, repeat up to 50 times
- Progressive mental handicap
- EEG: hypsarrhythmia
- usually 2nd to serious neurological abnormality (e.g. TS, encephalitis, birth asphyxia) or may be cryptogenic
- poor prognosis
Lennox-Gastaut syndrome
May be extension of infantile spasms (50% have hx)
- onset 1-5 yrs
- atypical absences, falls, jerks
- 90% moderate-severe mental handicap
- EEG: slow spike
- ketogenic diet may help
Benign rolandic epilepsy
- paraesthesia (e.g. unilateral face), usually on waking up
Juvenile myoclonic epilepsy (Janz syndrome)
Typical onset in the teens, more common in girls
- Infrequent generalized seizures, often in morning
- Daytime absences
- Sudden, shock like myoclonic seizure
- usually good response to sodium valproate
aetiology of seizures
- 2/3 are idiopathic (often familial)
- Structural:
- Head injury = cortical scarring – yrs post-head injury
-
Developmental – antenatal and prenatal factors
- Intrauterine infections such as rubella and toxoplasmosis
- Maternal drug abuse
- perinatal trauma and anoxia = brain injury
- Space-occupying lesion - intracranial tumours = sudden onset seizures
- Stroke
- Hippocampal sclerosis: post febrile convulsion
- Vascular malformations
- Non-epileptic cause of seizures:
- Withdrawal: EtOH, opiates, benzodiazepine
-
Metabolic:
- Acute hypoxia:respiratory or cardiac arrest 2O to anoxic encephalopathy
- Glucose: ↑↓
- Electrolyte disturbance: ↑↓ Na, ↓Ca, ↓Mg
- Failure: uraemia, hepatic failure, porphyria
- Chronic encephalopathy: grey matter damage
- Trauma: head trauma, haemorrhage, ↑ICP
-
Infection:
- meningitis, encephalitis, cycticerosis (parasitic tissue infection – tapeworm),HIV
- Febrile convulsions: high fever secondary to non-cerebral infections (> six months and < six years)
- Systemic disease: polyarteritisnordosa, SLE, sarcoidosis, tuberous sclerosis
- Drugs: tricyclics, cocaine, tramadol, theophylline
- Pregnancy: Eclampsia
Pseudoseizure: psychogenic seizures
pathophysiology
- Genetics: autosomal dominant inheritance –channelopathiesin voltage-gated or ligand gated ion channels
- Neurotransmitters: abnormalities in excitatory neurotransmitter glutamate and the inhibitory neurotransmitter GABA
s/s
As well as the seizure activity described above patients who have had generalised seizures may
- bite their tongue
- experience incontinence of urine
Asking about such features can be useful way of detecting epileptic seizures when taking a history from a patient who presents with a ‘blackout’ or ‘collapse’.
Following a seizure patients typically have a postictal phase where they feel drowsy and tired for around 15 minutes.
Investigations
Following their first seizure patients generally have both an electroencephalogram (EEG) and neuroimaging (usually a MRI).
Management
Most neurologists now start antiepileptics following a second epileptic seizure.
As a general rule:
- sodium valproate is used first-line for patients with generalised seizures
- carbamazepine is used first-line for patients with partial seizures
Antiepileptics are one of the few drugs where it is recommended that we prescribe by brand, rather than generically, due to the risk of slightly different bioavailability resulting in a lowered seizure threshold.
drug mx of epilepsy
Epilepsy: treatment
Most neurologists now start antiepileptics following a second epileptic seizure. NICE guidelines suggest starting antiepileptics after the first seizure if any of the following are present:
- the patient has a neurological deficit
- brain imaging shows a structural abnormality
- the EEG shows unequivocal epileptic activity
- the patient or their family or carers consider the risk of having a further seizure unacceptable
Sodium valproate is considered the first line treatment for patients with generalised seizures with carbamazepine used for partial seizures
Generalised tonic-clonic seizures
sodium valproate
second line: lamotrigine, carbamazepine
Absence seizures* (Petit mal)
sodium valproate or ethosuximide
sodium valproate particularly effective if co-existent tonic-clonic seizures in primary generalised epilepsy
Myoclonic seizures
sodium valproate
second line: clonazepam, lamotrigine
Focal** seizures
carbamazepine or lamotrigine
second line: levetiracetam, oxcarbazepine or sodium valproate
*carbamazepine may actually exacerbate absence seizure
** the preferred term for partial seizures
which group of people must you be careful of when
It is useful when thinking about the management of epilepsy to consider certain groups of patients:
patients who drive: generally patients cannot drive for 6 months following a seizure. For patients with established epilepsy they must be fit free for 12 months before being able to drive
patients taking other medications: antiepileptics can induce/inhibit the P450 system resulting in varied metabolism of other medications, for example warfarin
women wishing to get pregnant: antiepileptics are generally teratogenic, particularly sodium valproate. It is important that women take advice from a neurologist prior to becoming pregnant, to ensure they are on the most suitable antiepileptic medication. Breast feeding is generally considered safe for mothers taking antiepileptics with the possible exception of the barbiturates
women taking contraception: both the effect of the contraceptive on the effectiveness of the anti-epileptic medication and the effect of the anti-epileptic on the effectiveness of the contraceptive need to be considered
common medications used in epilepsy
Sodium valproate:
MOA: Increases GABA activityFirst-line for generalised seizures
- increased appetite and weight gain
- alopecia: regrowth may be curly
- P450 enzyme inhibitor
- ataxia
- tremor
- hepatitis
- pancreatitis
- thrombocytopaenia
- teratogenic (neural tube defects)
Carbamazepine
MOA: Binds to sodium channels increasing their refractory periodFirst-line for partial seizures
- P450 enzyme inducer
- dizziness and ataxia
- drowsiness
- leucopenia and agranulocytosis
- syndrome of inappropriate ADH secretion
- visual disturbances (especially diplopia)
Lamotrigine
MOA:Sodium channel blockerUsed second-line for a variety of generalised and partial seizures
- Stevens-Johnson syndrome
Phenytoin
MOA: Binds to sodium channels increasing their refractory periodNo longer used first-line due to side-effect profile
- P450 enzyme inducer
- dizziness and ataxia
- drowsiness
- gingival hyperplasia, hirsutism, coarsening of facial features
- megaloblastic anaemia
- peripheral neuropathy
- enhanced vitamin D metabolism causing osteomalacia
- lymphadenopathy
acute mx of seizures
Acute management of seizures
Most seizures terminate spontaneously.
When seizures don’t terminate after 5-10 minutes then it is often appropriate to administer medication to terminate the seizure.
Patients are often prescribed these so family members may administer them in this eventuality, often termed ‘rescue medication’.
Benzodiazepines such as diazepam are typically used are may be administered rectally or intranasally/under the tongue.
If a patient continues to fit despite such measures then they are termed to have status epilepticus.
This is a medical emergency requiring hospital treatment.
Management options include further benzodiazepine medication, infusions of antiepileptics or even the use of general anaesthetic agents.