Seizures and epilepsy

Question 1

Define seizure?

Answer 1

Transient occurence of SS due to abnormal excessive or synchronous neuronal activity in the brain (not necessary convulsions –> motor seizure)
* Provoked seizure: occuring at the time or in close temporal association with documented brain insult. Arise from pathological lowering of seizure threshold (if temporary does not rise to epilepsy) e.g. fever, neurological (stroke, TBI, encephalopathy, SDH) or metabolic (hypogly, hypoCa, hypoNa)
* Unprovoked seizures: absence of temporary/reversible factor causing decreased seizure threshold. Cryptogenic seizure: seizure with a presumed yet unidentified structural cause. Remote symptomatic seziures due to chronic irreversible conditions that increase risk of seizures e.g. tumors, post stroke states, autoimmune diseases
* Reflex seizure: triggered by exintrinsic cause (light, tactile, acoustic stimulus)

Question 2

Define epilepsy

Answer 2

An enduring tendency (>60% risk) to develop unprovoked seizures

Defined as
* >2 unprovoked/reflex seizures occuring >24h apart
* 1 unprovoked/reflex seizure with a >60% risk of seizure recurrence in next 10y
* Diagnosis of epilepsy syndrome

Question 3

Pathogenesis of seizures?
Conditions that change seizure threshold?

Answer 3

Oscillations by cortical neurons within each network depends on activity of inhibitory neurons (GABA neurons), communication between different neurons (synaptic transmission), intrinsic neuronal properties (ability to maintain burst firing)
Acute symptomatic seizure caused by any acute brain insult e.g. stroke (esp lobar hemorrhage), SAH, SDH, TBI, brain abscess
Epilepsy due to underlying genetic, structural, metabolic, immune, infectious, unknown

Change in seizure threshold
* Increased connectivitiy
* Increased excitatory transmission +failure of inhibitory mechanisms
* Changes in intrinsic neuronal properties

Question 4

Types of seizures

Answer 4

• Focal seizures: originate within networks within 1 hemisphere. Usually due to underlying focal CNS lesiosn
• Generalized seizures: originate and rapidly engaging bilateraly distributed networks. Usually with a strong genetic component. Discharges arise from subcortical location and spreads to bilateral cortex simultaneously

Question 5

How to categorize focal seizures?

Answer 5

• Focal aware seizure if no LOC
• Focal impaired awareness seizure (prev complex partial): aura (same as focal aware seizure, represents phase before progressin to LOC), LOC (may be a/w behavioural arrest/staring, automatisms)
• Focal to bilateral tonic clonic if focal progresses into a generalized seizure

Question 6

How to localize focal seizures?

Answer 6

Mesial temporal lobe (commonest): complex aura +/-progression into impairment in consiousness
* Aura: visceral disturbances (gustatory and olfactory hallucinations, epigastric rising sensation), psychiatric symptoms (deja vu, jamais vu, depersonalization), sensory symptoms: visual/auditory hallucinations
* After progression into LOC (complex partial seizure/focal impaired awareness seizure): automatisms –> orobuccal movements (chewing, swallowing, sucking), complex motor phenomena (bicycling, kicking)

Frontal lobe: focal clonic movements
Jacksonian march: marching clonic movement with gradual anatomical spread
Parietal lobe (uncommon): focal/spreading paresthesia or tingling sensation
Occipital lobe: visual phenomena varying from simple flashes to complex hallucination

Question 7

Types of generalized seizures?

Answer 7

Question 8

Presentation of post ictal period of seizure?

Answer 8

Question 9

ddx of epileptic seizures

Answer 9

Question 10

Causes of epilepsy according to age

Answer 10

Question 11

etiology of epilepsy
Structural
Genetic
Infectious
Other (metabolic, immune, unknown)

Answer 11

Question 12

Epilepsy syndromes

Answer 12

Question 13

Early infantile epileptic encephalopathy cause and features

Answer 13

Question 14

Dravet syndrome cause and features

Answer 14

Question 15

Infantile spasm cause and features

Answer 15

Question 16

Lennox Gastaut syndrome cause and features

Answer 16

Question 17

Generalized epilepsy with febrile seizure plus (GEFS) cause and features

Answer 17

Question 18

Approach to epilepsy?

Answer 18

Question 19

Non pharmacological mx of epilepsy

Answer 19

Question 20

Indications for starting AED and types of antiepileptics

Answer 20

Question 21

Use of AEDs in types of seizures

Answer 21

Question 22

What cautions of AEDs in women?
What drugs need to be changed?

Answer 22

Question 23

Preop evaluation for epilepsy surgery

Answer 23

□ Video EEG ± invasive intracranial EEG
□ Neuroimaging
□ WADA test: determine language lateralization and memory fx of each temporal lobe→ sedating agent injected into ICA → determine dominance to prepare for TLE surgery
□ Cortical mapping

Question 24

Temporal lobe epilepsy surgery and S/E

Answer 24

Question 25

Neurostimulation mx in epilepsy

Answer 25

 Vagus nerve stimulation (VNS): regular pulsed stimulation via vagus nerve → desynchronize cerebral activity + ↑synthesis of inhibitory neurotransmission
 Deep brain stimulation (DBS): usually at anterior thalamus to abort seizure spread

Question 26

Define status epilepticus

Answer 26

Question 27

Types of status epilepticus

Answer 27

Question 28

Causes of status epilepticus

Answer 28

□ Acute cerebral insult due to
→ CNS infections (classically encephalitis)
→ Neurotoxins incl. drugs, eg. lignocaine, amphetamine
□ Rapid withdrawal of AEDs

Question 29

General mx of status epilepticus

Answer 29

Question 30

Acute mx of status epilepticus

Answer 30