IC6 Flashcards
what is the definition of epilepsy?
disease of the brain with any of the following
1) ≥2 unprovoked seizures >24h apart.
2) 1 unprovoked seizure with a probability of further seizures being similar to part 1).
3) diagnosis of an epileptic syndrome.
what is the difference between acute and remote seizure?
acute seizures occur immediately after a recognisable stimulus/cause
VS
remote seizures occur >1 week following a disorder known to increase risk
what is an unprovoked seizure
occuring in the absence of a potentially responsible clinical condition OR beyond the interval estimated for occurrence of acute symptomatic seizures.
etiology of acute symptomatic seizures
Metabolic
* Hyponatremia
* Hypocalcemia
* Hypomagnesemia
* Hypoglycaemia
Toxic subst/drugs
* Illicit drugs (e.g. cocaine, amphetamines)
* Drugs (e.g. Tricyclic antidepressants, carbapenems, baclofen)
* ETOH (withdrawal & intoxication)
* Benzodiazepine withdrawal
Structural
* Stroke
* Traumatic Brain Injury
Infection/Inflammation
* CNS Infection
* Febrile illness
wht is your understanding of drug induced seizures
drugs don’t really induce seizures. rather, they lower the seizure threshold.
risk depends on
- effects on neurotransmission
- time course (starting new drug, withdrawal)
- concentration reaching brain
- susceptibility risk factors (PMH seizure, structural or functional brain abnormalities, concurrent drug use).
what are common drugs that lower seizure thresholds?
antimicrobials (high dose beta lactams eg carbapanems)
analgesics (opiods eg pethidine/meperidine, tramadol..)
antipsychotics (clozapine)
antidepressants (bupropion, overdose situations)
immunosuppressants (cyclosporin)
stimulants (eg dextroamphetamine, methylphenidate)
what are non-epileptic events
not related to abnormal epileptiform discharges but manifests like epileptic seizures.
1) psychogenic non-epileptic seizures (PNES)
- caused by stressful psychological experiences/emotional trauma.
- involuntary.
- partial alteration of LOC with partial preservation of awareness.
2) physiological non-epileptic events (PNEE)
- symptoms of paroxysmal systemic disorder.
- convulsive syncope, hypoglycemia, migraine aura, non-ictal dysautonomia, intoxications, transient ischemic attacks, panic attacks
- movement disorders, balance disorder, sleep disorders,
pathophysiology of a seizure
1) short in circuit
- paroxysmal depolarisation shift, where instability = one cell or a group of cells become excited.
2) driving of normal neighbours
(synchronisation OR synchronised paroxysmal discharges)
- repeated paroxysmal depolarisation will increase extracellular K+
- less K+ able to diffuse out during the hyperpolarised state and the cell remains partially depolarised + depolarise other cells.
3) failure of inhibition
- loss of hyperpolarisation
- loss of surround inhibition (neurons that drive inhibitory tone are reduced)
- excess glutamate stimulation/excess excitatory neurotransmitters)
- increase intracellular Ca2+ (and other intracellular and extracellular substance abnormalities)
what part of the brain plays a large role in epilepsy?
hippocampus
plays a role in hyper-synchronisation
- hippocampal sclerosis
- intrinsic reorganisation of local circuits (hippocampus, neocortex, thalamus) = synchronisation and promotes generation of epileptiform activityt.
etiology of epilepsy
- Structural
– E.g. Hippocampal sclerosis, brain tumours, vascular malformations, glial scarring (including stroke and traumatic brain injury) - Genetic/presumed genetic
– E.g. Dravet syndrome with SCN1A mutations - Neurodegenerative
– E.g. Alzheimer’s disease - Metabolic
– E.g. inborn errors of metabolism, mitochondrial disorders - Infectious
– E.g. bacterial meningitis, encephalitis, neurocysticercosis
how does ILAE classify seizures
1) region where seizure begins in the brain
- focal onset (partial) - one hemisphere
- generalised onset - both hemisphere
- secondarily generalised - start from one, then spreads to another.
2) impairment of consciousness
or level of awareness
what are the phases of a seizure?
prodromal
early ictal (aura)
ictal
postictal
clinical presentation of focal onset/simple partial seizure (motor, sensory, autonomic, psychic)
motor:
- clonic movement (repeat jerking)
- speech arrest
sensory
- numbness, tingling
- visual disturbance = flashing lights
- rising epigastric sensation
autonomic
- sweating, saliva, pallor
- BP, HR
psychic
- flashbacks, dé j à vu (memory
- Visual, auditory, auditory, gustatory or olfactory hallucinations
- Affective symptoms include fear (most common), depression, anger and irritability
ILAE classification of partial/focal seizure
simple:
- retained consciousness
- retained msucle tone
- staring spells
complex
- initial aura
- LOC
- ictal automatisms (repeated movement)
- postictal confusion
secondary generalised
- initial aura
- convulsion W/W/O jacksonian march
- postictal confusion W/W/O todds paralysis
characteristics of tonic-clonic (grand mal) seizure
tonic phase (stiffening limbs) > clonic (jerking limbs/face)
tonic phase
- breathing decrease/cease
- cyanosis of nail beds, lips, face
clonic phase
- 1 min (appx)
- brain then becomes extremely hyperpolarised and insensitive to stimuli.
- incontinence
- biting tongue
post ictal
- headache, lethargy, confused, sleepy
- minutes to hours to recover
