Neuro - Epilepsy

Question 1

Epileptic Seizures

Definitions
Aetiology
Pathophysiology
Provoked Seizures
Effect on Driving

Answer 1

1.) Definitions
- seizure: episodes of abnormal electrical activity
- epilepsy: >2 unprovoked seizures >24hrs apart
- status epilepticus: seizure lasting > 5mins or > 3 seizures in one hour (w/o complete recovery)

2.) Aetiology
- genetic: differences in brain chemistry
- drugs: exogenous activation of receptors
- metabolic: acquired changes in brain chemistry
- neuronal damage: e.g. from strokes or tumours

3.) Pathophysiology - ↑↑excitation and synchronisation of a group of neurones within the brain due to:
- ↑excitatory (glutamate) or ↓inhibitory (GABA) signals
- generalised seizures originate in both hemispheres
- focal seizures often originate from one hemisphere
- can be brought on by a particular stimulus e.g. light, music, eating, movement, reading, shower/bath

4.) Provoked Seizures - due to other medical conditions, often the cause in elderly
- drug/alcohol use or withdrawal
- head trauma/intracranial bleeding, CNS infections,
- post-surgical complications
- metabolic e.g. hyponatraemia, hypoglycaemia
- febrile seizures in infants, uncontrolled hypertension
- cerebrovascular disease

5.) Antiepileptic Drugs
- can be stopped if seizure free for >2 years and stopped over 2-3 months

5.) Effect on Driving - must surrender the licence to DVLA
- one-off seizure: reapply in 6mths, (5yrs if bus/lorry)
- >1 seizure/epilepsy: reapply in 1yrs, (10yrs if bus/lorry)

Question 2

Generalised Seizures

Tonic-Clonic (Grand Mal)
Absence (Petit Mal)
Myoclonic
Atonic

Answer 2

1.) Tonic-Clonic - most typical seizures
- LOC w/ episodes of muscle tensing (tonic) followed by muscle jerking (clonic), often associated with:
- involuntary movements: tongue biting, incontinence, groaning and irregular breathing
- prolonged post-ictal period: where the person is confused, drowsy, and feels irritable or depressed
- Mx: 1°sodium valproate, 2°lamotrigine or carbamazepine

2.) Absence - typically happens in children
- lose awareness of surroundings, stares into space, is non-responsive, but then abruptly returns to normal
- often flutter their eyelids or slightly jerk their body/limbs
- can be provoked by hyperventilation or stress
- lasts 10-20s and can happen several times a day
- seizures often stop as patients get older
- Mx: 1°sodium valproate OR ethosuximide
- avoid carbamazepine as can worsen

3.) Myoclonic - muscle jerking
- sudden brief muscle contractions w/o LOC
- often in children (teenage girls) as juvenile myoclonic epilepsy: combo of absence, tonic-clonic, and myoclonic seizures classically associated with seizures in the morning/following sleep deprivation
- Mx: 1°sodium valproate, 2°lamotrigine/levetiracetam/topiramate
- avoid carbamazepine as it can worsen

4.) Atonic - known as “drop attacks”, no LOC
- brief lapses in muscle tone, usually lasting < 3 mins
- often begin in childhood, may indicate Lennox-Gastaut syndrome
- Mx: 1°sodium valproate, 2° lamotrigine

Question 3

Focal/Partial Seizures

Pathophysiology
Presentations
Management

Answer 3

1.) Pathophysiology - often begins from the temporal lobe
- slightly later onset at 40-50s
- simple (most common): w/o LOC, no post-ictal sx
- complex: LOC after an aura or seizure onset, post-ictal sx are common e.g. confusion

2.) Presentations - lobe dependent:
- temporal: hallucinations (olfactory/auditory), déjà vu,
automatisms (eg. lip-smacking, plucking of clothes), post-ictal dysphasia, emotional disturbance
- frontal: motor sx e.g. dysphasia, Todd’s paralysis (weakness in a limb), Jacksonian march
- parietal: motor and sensory sx e.g. tingling/numbness
- occipital: visual sx e.g. spots and lines in visual field

3.) Management
- 1°+2°levetiracetam or lamotrigine vice versa
- 3° carbamazepine
- 4° sodium valproate

Question 4

Management of a Status Epilepticus

Initial Management
Pharmacological Treatment
Investigations
Differential Diagnoses

Answer 4

1.) Initial Management - full A-E assessment
- start a timer, no drugs for the first 5 minutes
- positioning of the patient to avoid injury (recovery position if possible)
- support respirations with oxygen, maintaining blood pressure
- correction of any hypoglycaemia (most common cause)
- consider IV Pabrinex if suspecting alcohol abuse
- get them into the recovery position if possible

2.) Pharmacological Treatment - benzodiazepines
- 1°IV lorazepam 4mg bolus (can repeat once after 10 minutes if needed)
- IM/BUC midazolam 10mg OR PR diazepam 10mg if in the community or there is any delay in IV access
- seek senior help if the patient doesn’t respond to the first dose of benzo
- 2° IV phenytoin by slow infusion (max rate of 50mg/min)
- 3° IV phenobarbital or general anaesthesia - contact ITU often over 30 mins after initiation of treatment with no improvement

3.) Investigations
- ABG: O2 and BM (most common reversible cause)
- bloods: FBC, U+E, LFT, CRP, clotting, Ca, Mg
- serum and urine save for toxicology, and pretreatment antiepileptic drug levels should be sent as appropriate.
- electroencephalogram (EEG): not definitive, more for classification, relies on capturing an episode
- MRI: to detect vascular or structural causes, often used in drug-resistant epilepsy

4.) Differential Diagnoses - from epilepsy
- syncopal episodes, TIAs, migraines
- movement disorders e.g. Parkinsons, Huntingtons
- cardiac e.g. arrhythmia, reflex anoxic seizures
- non-epileptic attack disorders

Question 5

Anti-Epileptic Drugs (AEDs)

Sodium Valporate
Carbamazepine
Lamotrigine
Levetiracetam
Phenytoin

Answer 5

1.) Sodium Valproate - GABAa agonist/NaC blocker
- first-line for most forms apart from focal seizures
- teratogenic: need pregnancy prevention programme, avoided in women of child bearing age
- side effects: tremor, ataxia, weight gain, alopecia
- hepatitis, pancreatitis, thrombocytopenia, PCOS, hyponatraemia, CYP450 inhibitor

2.) Carbamazepine - blocks NaC when inactivated
- first-line for focal seizures
- avoid in absence and myoclonic seizures as it can worsen
- CYP450 inducer: ↓efficacy of COCP and some Abx
- other side effects: agranulocytosis, aplastic anaemia, ataxia, diplopia, SIADH, SJS,

3.) Lamotrigine - NaC blocker, also affects Ca channels
- effective in focal epilepsy or when sodium valproate is contraindicated
- side effects: SJS, tremor, diplopia, leukopenia

4.) Levetiracetam - synaptic vesicle glycoprotein binder which ↓neurotransmitters release into the synapse
- can be used for focal and generalised seizures
- has fewer side effects and is safe in pregnancy

5.) Phenytoin - NaC blocker, exhibits zero-order kinetics
- CYP450 inducer: ↓efficacy of COCP and some Abx
- other side effects: aplastic anaemia, vitD deficiency, peripheral neuropathy –> osteomalacia, folate deficiency –> megaloblastic (macrocytic) anaemia