wiki:neurology:epilepsy

Epilepsy

It is important to establish the cause of transient loss of consciousness for which epileptic seizures are of the most common causes.
distinguishing functional, non-epileptic seizures from syncope or true epilepsy is a challenge in the ED

Classification of Epilepsy generally defined by the International League against Epilepsy 2010 (ILAE):

1. focal seizures (no LOC)
2. focal dyscognitive seizures

3. partial seizures evolving to generalised tonic-clonic (GTC) convulsions

convulsive or non-convulsive with bilateral discharges involving subcortical structures

NICE guidance - 1st seizures should be referred and seen within 2/52
anti-epileptic medication is not required for 1st seizure unless investigations suggest high risk of recurrence
history, exam and investigations
- determine whether the seizure is epileptic vs non-epileptic
- aimed at excluding infective and metabolic causes, alcohol and recreational drug use as well as potential for trauma
- include ECG for cardiac causes
- MRI is preferred scan but CT scan if intracranial event is suspected - eg trauma, anti-coag Rx, immunodeficency, Hx of malignancy, focal seizure, new CNS signs, fever
attention to stabilising patient - secure airway, IV access,etc

failing to recognise seizure activity - non-convulsive seizure is rare presentation of altered mental state
failing to treat early enough and aggressively enough, with neurological dysfunction thought to result after 20mins of continuous seizures
failing to consider underlying aetiology - looking for sepsis, metabolic derangement etc

Seizure which fails to self-terminate - can be either convulsive or non-convulsive
Convulsive Status - tonic clonic seizures persisting or recurring for >5mins

Management priorities
- stabilise airway
- IV access
- aggressive pharmaceutical approach to halting seizure

Consensus is that benzodiazepines are drug of 1st choice with Lorazepam the most effective and has longer seizure t_1/2 than diazepam. 2nd drug choice is phenytoin but there is no data or consensus on which drug is 3rd in line:
- 2 doses of IV Benzodiazepines are the drug of 1st choice. Buccal Midazolam in children or rectal diazepam if not available or difficult
- Lorazepam 4mg or
- Midazolam 10mg

Other anti-epileptic agents following benzodiazepines:

Phenytoin 20mg/kg @50mg/min = 1st choice
phenobarbital 10-15mg/kg
propofol 1-2mg/kg bolus the 2-10mg/kg/hr
Na+ valproate 30-40mg/kg (<3g) @10mg/kg/min
levetiracetam 40-60mg/kg (<4.5g) @6mg/kg/min
Although no recognised agreement on priority of drugs to use after benzodiazepines, any of the 3 drugs (levetiracetam, phenytoin, valproate) can be considered as potential first-choice, second-line drugs for benzodiazepine-refractory status epilepticus

First-line treatment is 2 doses of a benzodiazepine given 10 min apart
continued fitting 10 min after the second dose of benzodiazepine, administer second-line anticonvulsant. APLS recommends phenytoin as the first-choice second-line anticonvulsant; if the child is allergic to phenytoin, has previously not responded to it, or has experienced a serious adverse event (SAE), phenobarbital is recommended.
Failure to stop CSE necessitates rapid sequence induction (RSI), intubation, and admission to the PICU, with consequent potential for iatrogenic consequences including pneumonia, hospital-acquired infections, and prolonged admission.

Pharmacological agents
	Benzopdiazepines (BZD's)
	• GABA-A rec modulators • so-called “BZ1” rec responsible for sedative, amnesic and some anti-convulsive effects • BZ2 recs mediate anxiolytic and muscle relaxant effects • hepatic metabolism with renal excretion • peripheral vasodilator action
Lorazepam	• high potency, short acting • anticonvulsant and useful adjunct in psychosis • unique degradation pathway allowing use in renal dysfunction
Midazolam	• high potency, short acting
Diazepam	• medium potency, long acting • active metabolites which prolong clinical effect
Clonazepam	• high potency, long acting • additional serotonin agonist property
	Other Anti-Epileptic drugs
Phenytoin	• 'membrane stabiliser' via Na+ blockade • contraindicated with heart blocks • t_1/2 = 22/24
Phenobarbital	• binds to GABA_A but with lower specificity than benzo's • t_1/2 = 50-140/24
Propofol	• binds to GABA_A causing global CNS depression • t_1/2 = 40mins the 24+/24 after infusion