Seizures

Seizures

Definitions

Epidemiology:

Aetiology :

Seizure types

Specific Epilepsy Syndromes

Patient Evaluation

Differential diagnoses

Treatment:

Specific Anticonvulsants

Driving

Epilepsy and Suicide

Epilepsy and Sudden death

References

Definitions

• Seizure
• The clinical manifestations of an abnormal and excessive excitation of a population of neurons
• Epilepsy
• Recurrent seizures which are unprovoked by systemic or neurologic insults
• ILAE – “a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures”
1. Requires the “occurrence of at least one unprovoked seizure”

Epidemiology:

· 5-10% of the population will have a seizure in their lifetime

· 25-30% due to acute brain disturbance

· 30% of people who ever have a seizure will eventually be diagnosed with epilepsy

Recurrence rate in acute brain disturbance

• If no structural damage – less than 3%
• If structural damage 12.5% (1/8)

Recurrence rate if unprovoked:

• After one seizure 30-50%
• After 2 unprovoked seizures 70-80% -diagnosis of epilepsy

If a second seizure is to occur 60-70% occur within 6 months

Epilepsy

• Incidence 0.3-0.5%
• Prevalence 0.5-1%
• Lifetime risk 1.4%-3.3%

Seizure types and Classification

• Generalized seizures
• Begin in bilaterally distributed networks
• Can begin ‘focally’ within a network but do not recurrently originate in the same region.
• Partial
• Originate in networks limited to one hemisphere
• The seizure has a consistent focus of onset.
• Epilepsy syndromes will be grouped according to aetiology (see Epilepsy Syndromes)

Bold text = new ILAE terminology

Seizures	Description	EEG
Partial (focal)	Localized to discrete area’s of the cerebral cortex
Simple	Consciousness maintained “With observable motor or autonomic symptoms” Motor - Head and eyes turn away from side of focus - Jacksonian Autonomic “With subjective sensory or psychic symptoms only” = aura Sensory - Usually numbness or paraesthsia, visual relatively rare, auditory and vertiginous can also occur - Olfactory - Gustatory - Visceral Psychic
Complex “With impairment of consciousness or awareness”	Decreased awareness/ consciousness Frequent aura Automatisms Post-ictal confusion/amnesia Psychic symptoms can occur - Illusions, hallucinations, déjà vu, jamis vu, affective symptoms	Often normal Brief discharges – epileptiform spikes/sharp waves
Partial with secondary generalization “Evolving to bilateral convulsive seizure”	Usually frontal lobe focus Usually tonic-clonic seizure
Primarily generalized	Diffuse area’s of the brain simultaneously
Tonic-clonic	May be vague prodrome Most common seizure in metabolic disturbances Tonic phase 10-20sec - Pupils dilated and NR Clonic phase - 8Hz slowing to 4Hz - ~30s - Ends with deep inspiration Gradually increasing relaxation Usually no more than 1min Post-ictal – unresponsive, flaccid, salivation, bowel/bladder incontinence	Tonic phase – progressive increase in generalized low-voltage fast activity followed by generalized high amplitude, polyspike discharges. Clonic phase – spike and wave Post-ictal – generalized slowing.
Absence	Brief, sudden lapses of consciousness (2-10s) without lapses of postural control No post-ictal confusion Subtle movements may accompany Usually begin in childhood (4-8yrs) 15-20% of childhood seizures 60-70% resolve during adolescence 50% will also experience TC seizure 33% will have myoclonic jerks	Generalized, symmetric 3Hz spike and wave discharge that begins and ends suddenly Hyperventilation provokes seizures and EEG changes
Typical
Atypical
With special features
Myoclonic	Most common with metabolic syndromes, degenerative CNS disease, anoxic brain injury	Bilateral synchronus spike and wave pattern – at time of myclonus
Myoclonic atonic
Myoclonic tonic
Tonic
Clonic
Atonic	Brief loss of tone 1-2 sec with loss of consciousness No post-ictal confusion Associated with specific syndromes
Unknown
Epileptic spasms

Aetiology :

Causes in Adults

• Unknown 62%
• Stroke 9%
• Trauma 9%
• Alcohol 6%
• Neurodegenerative disease 4%
• Encephalopathy 3.5%
• Tumours 3%
• Infection 2%

Causes of seizure (by age)

Noenates (less than 1 month)	Hypoxia/ischaemia ICH Acute infection Metabolic Drug withdrawal Developmental disorders Genetic disorders
Infants and children (1month to 12 years)	Febrile seizures Genetic disorders CNS infection Developmental disorders Trauma Idiopathic
Adolescents (12-18yrs)	Trauma Genetic Infection Tumour Drug use Idiopathic
Young adults 18-35yrs	Trauma Alcohol withdrawal Drug use Tumour Idiopathic
Older adults Over 35yrs	Cerebrovascular disease Tumour Alcohol withdrawal Metabolic Alzheimer’s/degenerative disease Idiopathic

Aetiology and workup of “First Idiopathic seizures” – see

Specific Epilepsy Syndromes

Patient Evaluation

History

• Previous seizures including history of febrile seizures
• CNS lesions
• Trauma, CVA, tumour, vascular malformations
• Developmental milestones
• Family history
• Drug or alcohol abuse
• Precipitating factors:
• Sleep deprivation, systemic disease, electrolyte/metabolic disturbance, acute infection, drugs – legal/illegal, alcohol.
• Note: OSA can worsen seizure – think of this if well controlled epileptic worsens with age

Symptoms:

• Aura’s or other associated phenomena not previously diagnosed as seizure
• Behaviour
• Vocal
• Motor
• Eyes
• Motionless stare – MTLE
• Flickering – absence
• Deviated – focal
• Rolled back – syncope
• Closed – non-epileptic
• Respiration pattern
• Autonomic – drooling, pallor, N+V
• LOC

Post ictal

• Amnesia
• Lethargy
• Confusion
• Sleepiness
• Headache
• Muscle ache
• Tongue biting
• Incontinence
• Transient focal weakness
• N+V

Physical examination

• Neurological examination
• Signs of infection
• Cutaneous markers of CNS disease
• Signs of trauma
• Signs of metabolic disease
• CVS examination for risk of cerebrovascular disease

Investigations

• Bloods:
• Glucose, calcium, magnesium, U+E, LFT
• Toxin/drug screen
• Serum prolactin
• Lumbar puncture – if meningitis suspected or HIV pos

EEG

• Abnormal in 29% (range 8 to 50%) of adult patients presenting with first seizure
• Increased incidence of abnormalities in sleep deprivation
• During event
• Interictal
• 60% are normal in patients with known epilepsy

Imaging

• CT in emergency cases, otherwise MRI (although no good evidence)
• A significant abnormality is present in ~10% of adult patient with first seizure (CT or MRI)
• (Dr Archer) “80% of significant abnormalities will be detected on CT-B’

Differential diagnoses

• Migraines
• Psychotic disorders
• TIA/CVA
• Syncope
• Differentiating from syncope:

	Seizure	Syncope
Precipitating	Usu none	Stress, valsalva, cardiac event
Premonitory symptoms	None or aura	Tiredness, nausea, sweating, tunnelling of vision
Posture	Variable	Usually erect
Transition to unconciouness	Usu. Immediate	Gradual
Duration of unconsciousness	Minutes	Seconds
Duration of tonic or clonic movt.	30-60 seconds	Never more than 15sec
Facial appearance during event	Cyanosis, frothing at mouth	Pallor
Aching muscles after event	Often	Sometimes
Biting of tongue	Sometimes	Rarely
Incontinence	Sometimes	Sometimes
Headache	Sometimes	Rarely

Treatment:

• Treatment of underlying condition
• Avoidance of precipitating factors
• Anti-epileptic drug therapy
• Avoidance of dangerous activities
• Driving
• Operating machinery or at heights
• Swimming alone
• Treat/screen for concomitant problems
• Depression
• Overall effective in 60-70% of patients

Ketogenic Diet

• Effective, especially in paediatric populations

Surgery

• Temporal lobe resections
• 60-70% chance of being seizure free
• Vagal nerve stimulation
• 50% reduction in 30-40% of patients
• Deep brain stimulation
• Under investigation

First seizure treatment

Focal/Partial Seizures

• Monotherapy is primary aim
• Carbamazepine is first line
• Controls 70%

*

	Tonic-Clonic	Partial	Absence	Atypical*
First-line	Valproic acid Lamotrigine (child bearing women)	Carbamazepine Phenytoin Lamotrigine Valproic acid	Valproic acid Ethosuximide	Valproic acid
Alternatives	Phenytoin Carbamazepine Topiramate Zonisamide Felbamate Primidone Phenobarbital	Topiramate Levetriacetam Tiagabine Zonisamide Gabapentin Primidone Phenobarbital	Lamotrigine Clonazepam	Lamotrigine Topiramate Clonazepam Felbamate
Avoid	Ethosuximide Tigabine Vigabatrin		Phenytoin Carbamazepine Tigabine Vigabatrin

* Atypical absence, myoclonic, atonic

Specific Anticonvulsants

Driving

After isolated seizure	6 months
Epilepsy – From initial diagnosis	6 months
Epilepsy -Previously uncontrolled seizures	2 years
Sleep only seizures	12 months
Post surgery for epilepsy	12 months
Seizure due to identified stimulus in previously well controlled person	1 month
Stimulus not identified	3 months
If seizure causes MVA	1 year
Withdrawal of treatment	3 months
If seizure off treatment and treatment restarted	1month

Epilepsy and Suicide

• RR = 2 when all patients with psychiatric disease excluded
• Highest risk during first half year after diagnosis
• ? common pathogenic mechanism in terms of receptor abnormalities

SUDEP (Sudden unexpected death in epilepsy)

Epidemiology

• Australia ~280 deaths/year
• Mean age of death from epilepsy 52
• Rates

	Per 1000/year
New onset epilepsy	~ 0.35
General population of epilepsy	~ 0.5-2.0
Refractory seizures	~4.0
Associated mental retardation	~3.0

Pathogenesis

· Respiratory causes probably important

· ?Cerebral shutdown

· Small proportion cardiac cause (0.1-0.4% of seizures observed to cause asystole)

Risk factors

· Seizures:

o GTCS

o Recent or frequent seizures (>3 seizures in last year ~8x risk)

· Medications:

o Non-compliance

o Recent and frequent changes in medication

o Patients on polytherapy (polytherapy and >3seizures ~25x risk)

· Environment

o ?Lack of nocturnal supervision/sleeping alone

· ?Alcohol

· ?Depression

• SUDEP NEJM 2011, SUDEP Lancet 2011

References

“Evaluation of first seizure” Neurology 2007 69:pg1996-2007

“Initial Management of Epilepsy” NEJM 2008 359;2 pg166