Seizures and epilepsy Flashcards
Define seizures and epilepsy
- a seizure is a paroxysm of abnormal electrical discharges of the brain, often leading to overt neurological symptoms including involuntary movement, altered sensation and awareness
- epilepsy is a disorder predisposing to recurrent i.e. 2 or more unprovoked seizures
- seizures within a 24 hour period are regarded as a single cluster
- status epilepticus was once defined as continuous seizure activity >30min or a series of seizures within 30min without regaining function interictally
- now defined as min 5 minutes of continuous seizures OR min 2 discrete seizures between which there is incomplete recovery of consciousness
Breakdown the epidemiology of seizures and epilepsy
- lifetime prevalence of seizures is 8-10%
- lifetime prevalence of epilepsy is 1%
- there is a bimodal age distribution, but with a significant overlap
- childhood: genetic, or lesional from genetic causes
- older adult: lesional, from insults or neurodegenerative causes
List the differential diagnoses of epilepsy
- syncope
- TIA - mimicking Todd’s paresis
- migraine esp complex migraines
- psychogneic non-epileptic seizures (PNES)
- hyperkinetic movement disorder
Questionnaire and scoring system for symptoms relating to loss of consciousness is highly sensitive and specific to distinguish syncope from seizures.
Define positive and negative symptoms
- Positive symptoms – implies part of the nervous system is overactive: e.g. tingling, pins and needles, olfactory hallucinations, visual hallucinations (shimmering lights, fortifications)
- Negative symptoms – implies a part of the nervous system is underactive: e.g. weakness, numbness, blindness
- Transient positive focal brain symptoms strongly imply seizures (and sometimes migraine) ; transient focal negative symptoms usually imply ischaemia
Describe the features of focal epilepsy
- temporal lobe most common
- frontal, parietal and occipital less common
- aura: often as onset of seizure activity
- **asymmetry
- stereotypy**
- can spread to contralateral hemisphere and become bilateral – otherwise known as secondary generalisation
Focal epilepsies can be broken down into aware or simple partial, and impaired awareness or complex partial.
Aware focal onset can progress to bilateral/secondarily generalised tonic-clonic.
Describe generalised epilepsy
- generalised tonic-clonic epilepsy or grand mal, most common type
- symmetrical
- post-ictal confusion
- myoclonic or absence epilepsies often start in childhood or adolescence
- absence (petit mal) seizures often last less than 20-30 seconds, without change of muscle tone, or post-ictal confusion
Generalised onset can be motor (tonic, myoclonic, tonic-clonic) or non-motor (absence).
Briefly describe pathophysiology of epilepsy
is generally an imbalance between excitatory and inhibitory activity in a neural network.
Focal is mostly lesional, due to
- cortical dysplasia, perinatal injury, hippocampal sclerosis
- stroke, tumour, head trauma, vascular malformations, CNS infections
- neurodegenerative disease e.g. alz
General is predominantly genetic, due to:
- channelopathies, ion and non-ion
- most are still unknown and postulated to be polygenic
List some etiologies of seizures
- provoked seizures i.e. acute symptomatic seizures
- acute factors predominate, including
- direct CNS insult e.g. stroke, ICH, CNS infections
- metabolic derangement
- drug alcohol excess or withdrawal
- systemic infections
- sleep deprivation
- acute factors predominate, including
- unprovoked seizures
- intrinsic factor predominate, including
- genetic
- lesional
List relevant investigations
- EEG: routine or sleep-deprived, hyperventilation or photic stimulation, takes ~ 30 minutes, low sensitivity
- neuroimaging: non-contrast CT, low yield; MRI brain: modality of choice, epilepsy protocol requires 1mm slices in coronal view, MRI should appear normal for primary generalised epilepsy
List the aims of diagnosis and treatment
Diagnosis aims
- history: stereotypy, typical semiology
- some signs and investigation findings are very specific but not sensitive
- remains largely a clinical diagnosis as a result
Treatment
Treatment principles
- treat the underlying cause – in provoked seizures
- antiepileptic drugs: acute and long term treatment
- minimising provoking factors: sleep deprivation, alcohol excess, medications e.g. opioids and psychiatrics, antibiotics
- lifestyle mods: driving, heights/pools/baths
Describe treatment options
Acute treatment
STAT options
- Midazolam 2 – 5 mg (Onset of action: IV 5min, half-life: ~3 hours)
- Diazepam 5 – 10 mg (Onset of action: IV 3min, half-life: ~30 hours)
Administration route: IV, SC, IM, buccal, intranasal, PR
Long term
Broad spectrum:
- Sodium Valproate
- Lamotrigine
- Levetiracetam
- Phenytoin
Narrow spectrum:
- carbamazepine
- lacosamide
