Seizure Disorders

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Definitions

Seizure – (Schomer) state of pathologic hypersynchronous behavior of large number of neurons associated with an altered neurologic function

  • text defines it as – an episode of abnormally synchronized and high-frequency firing of neurons that results in abnormal behavior or experience of the individual

Epilepsy – a condition in which there is a tendency to have recurrent unprovoked seizures (about a 1- 2% incidence)

  • Lifetime risk of having a single seizure is higher, estimates ranging from 10 – 15% of population
  • 4th most common neurological disorder; most common neurological condition in childhood (4.3-9.3/1000)
  • Onset most often during childhood and adolescence
  • High incidence in prisons (4x general population): impulse control + lower SES + criminal behavior

Kindling – may account for susceptibility to electrophysiologic dysfunction in area opposite hemisphere homologous to original site of discharge

Aura – brief, simple partial seizures of any type experienced by a patient with no outward behavioral manifestations. They may occur in isolation, or they may serve as a warning for a larger seizure, when patients have seizures that typically begin in one region of the brain before spreading.

  • Patients with seizures arising from medial temporal limbic structures often report a visceral sensation of rising in the epigastric area, a feeling of déjà vu, strange unpleasant odors, or feelings of extreme fear and panic (smell, emotion, memory)
  • Odors and panic are thought to arise from the amygdala and nearby cortex, rather than the hippocampus

EEG (Electroencephlogram)

Alpha

8-13 CPS/hertz; the normal dominant/background activity; occurs over occipital region

  • Reflects an anxiety free state; used as guideline in biofeedback
  • Lost with eye opening, falling asleep, medication that affects mental function
  • Slows in elderly and in nearly every brain-based neurological illness
  • Slows in early stage Alzheimer Disease, but remains in normal range

Beta

>13 hertz; read over frontal lobes

  • Prominent with concentration, anxiety, under effects of minor tranquilizers

Theta and Delta

4-7 hertz and 1-3 hertz

  • Detected in children and everyone entering deep sleep; generally absent in healthy, alert adults
  • Presence may indicate a degenerative illness or metabolic derangement
  • Focal presence may suggest a lesion in that region

EEG in other differential diagnoses

  • triphasic waves present in metabolic/toxic encephalopathy and hepatic/renal failure delirium;
  • periodic complexes present (seen as myoclonic jerks) in subacute sclerosing parencephalitis (SSPE) and Creutzfeld-Jakob disease;
  • can differentiate between locked-in syndrome and persistent vegetative state (slow and disorganized)
    • EEG is not useful to detect or exclude structural lesions
    • EEG after ECT looks post-ictal (similar to GTC sz), and slow wave activity may continue for 3 months

Seizure Activity

  • Ictally, EEG reveals paroxysmal activity consisting of bursts of spikes, slow waves, or complexes of spikes and waves or poly-spikes and waves.
  • Post ictally, EEG shows low voltage activity (“postictal depression”) followed by diffuse high voltage slowing
  • Interictally, EEG often contains specific abnormalities supporting a diagnosis in 80% of epilepsy patients (20% have normal interictal EEGs). To evoke abnormalities, may try hyperventilation, strobe, sleep deprivation
  • 15% of population has nonspecific EEG changes (e.g., background slowing) – 1-2% have slow wave or spikes but no ictal events
  • Up to 60% of individuals with known epileptic disorders will not show abnormalities on the typical in office brief EEG!

Taxonomy

Partial Seizures (a.k.a. “focal”)

Begin in focal region of brain and semiology reflects this focus; may or may not spread; aura may be present. Typically last 5-10 seconds, but longer periods not uncommon

Simple Partial

  • No post-ictal deficits unless seizures are prolonged or recurrent as in Todd’s hemiparesis (see below)
  • Consciousness not impaired; one mode of expression
  • Motor (Jacksonian march – spreads along motor cortex. Todd’s mono or hemiparesis – accompanying post-ictal muscle weakness)
  • Seizures in frontal motor association cortex can include “fencing posture”, bilateral leg cycling movements, turning of eyes, head or body
  • Sensory (unformed hallucinations in any sensory modality)
  • Can have positive symptoms (e.g., hand twitching), or negative symptoms (e.g., impaired language abilities)

Complex Partial (i.e., “psychomotor seizures”)

  • Typical duration 30 seconds – 2 minutes
  • Consciousness is impaired
  • May have complete impairment or may only be “mild” – sometimes making the distinction between simple partial seizures difficult
  • Can have simple partial onset followed by impairment of consciousness – or consciousness can be affected at onset
  • complex symptoms including automatisms, subjective feelings, postural changes
  • postictal – confusion (including aphasia w/dominant hemisphere involvement), amnesia, fatigue, agitation, aggression, and headache
  • Most originate in temporal lobe
    • Medial temporal lobe-onset complex partial seizures often begin with an aura of unusual, indescribable sensation, or with epigastric, emotional, or olfactory phenomena.
  • Initial symptoms are followed by unresponsiveness and loss of awareness, during which patient may have automatisms (e.g., lip smacking, swallowing, or stereotyped hand or leg movements)
  • Often, basal ganglia are involved – leading to contralateral dystonia/immobility. Thus, automatisms occur in the ipsilateral extremity — can lead to inaccurate localizing to the “unpracticed eye”
  • Usually begin in late childhood and early thirties
  • Most common type of seizure (65% of all epilepsy pts)
  • Difficult to recognize and interpret due to almost limitless variety of clinical findings; often mimic other disorders, especially psychiatric ones
  • Intellectual symptomatology (aphasia, memory distortion – déjà vu [already seen], jamais vu [feeling of not having seen that which is familiar], deja entendu, jamais entendu, deja pensee, cognitive alterations – dreamy state, depersonalization, forced thinking, thought blocking)
  • Affective symptomatology (fear, depression, pleasant/unpleasant experience, anxiety, embarrassment, anger, compulsions)
  • Psychosensory symptomatology (illusions – metamorphosia [sudden distortion of a common object or person], micropsia [objects have become smaller, further away, or suddenly out of reach], macropsia [objects have become larger, closer to or “towering over” the patient], hallucinations – olfactory, gustatory, auditory)
  • Psychomotor symptomatology (automatisms – simple, speech, affective, complex; present in 80% of complex partial seizure pts)

Partial Seizures evolving to secondarily generalized seizures

  • From simple or complex; spreads across corpus callosum to entire cortex
  • Epilepsia partialis continua (a.k.a. focal status epilepticus) – partial seizures continue for hours/ days

Generalized Seizures

  • Synchronized bilateral electrical discharge involving whole cortex.
  • No aura, no focal semiology, no lateralized findings, no focal EEG abnormalities.
  • Immediate LOC.
  • May be nonconvulsive (e.g., absence) or convulsive (e.g., tonic-clonic).
  • Rarely result from tumors, infarctions, or structural lesions.
  • Postictal amnesia, confusion, fatigue, unresponsiveness

Absence (petit mal)

  • Onset usually 4-10 years of age, disappear in adulthood in about 40% of cases
  • 40% – absence replaced by GTC seizures
  • characteristics: 1-10 second lapse of attention (staring) with automatisms and subtle clonic limb movements; maintain tone and bladder control; no significant postictal symptoms
  • easily confused with inattention, dullness, or complex partial seizures (but differential diagnosis critical due to variable treatment)
  • inherited autosomal dominant pattern
  • 3/second spike and wave
  • often can be provoked by hyperventilation, strobe lights, or sleep deprivation

Atypical Absence

  • Usually begin in early childhood
  • Frequently accompanied by other generalized seizure
  • Difficult to control

Myoclonic

  • Brief, single symmetrical jerks of head and upper extremities; in series or clusters, common after waking
  • No LOC (duration of generalized polyspike-wave burst usually <1 second)

Clonic

Tonic

Tonic-clonic (grand mal)

  • Begin at any age after infancy and persist into adulthood
  • Massive motor activity (tonic stiffening of trunk followed by clonic rhythmic jerking of extremities) lasting less than 5 minutes, profound postictal residua
  • Inherited autosomal dominant trait
  • Incontinence or tongue biting is common
  • Immediately postictally, patients lie immobile, flaccid, and unresponsive, with eyes closed, breathing deeply to compensate for the mixed metabolic and respiratory acidosis produced by seizures
  • Post-ictal deficits last from minutes to hours and include profound tiredness, confusion, amnesia, headache, and other deficits related to location of seizure onset

Atonic (“drop seizures”)

Abrupt loss of muscle tone that produces a sudden fall

Generalized status epilepticus

May persist for many hours and become life threatening.

Reflex epilepsy

Seizures in response to specific stimulus (e.g., light, television, music)

Febrile seizures

Occur in 2-4% of all children; recur in 1/3 of them. Tx is fever prophylaxis or oral diazepam with fever onset

Staring Spells: Complex Partial Seizures vs. Absence Seizures

Features Typical absence Seizure Typical medial temporal complex seizure
Aura None May be present
Duration less than 10 sec. 30-120 secs
Automatisms None aside from minor mvmt of mouth / eyelids May be present
Post-ictal deficits None May be present
Frequency Multiple events daily 3-4 monthly
Ictal EEG Generalized 3-4 hz spike-wave Unilateral or assymetric 5-8 hx over temporal lobe

Epilepsy Syndromes

West Syndrome (infantile spasms)

  • Clusters of myoclonic seizures
  • Myoclonic seizures cease between 2-4 years old, but give rise to other seizure types in 25-60% of cases

Lennox-Gastaut

  • Mixed seizure disorder – includes atypical absence, atonic, myoclonic
  • Onset ages 2-8
  • EEG – background slowing and slow spike and wave
  • Seizures difficult to control and status is common

Benign Focal Epilepsy of Childhood

  • Most common type of partial seizure
  • centrotemporal spikes
  • Rolandic Epilepsy (nocturnal seizures)
    • believed to have autosomal dominance with incomplete penetrance
    • EEG has characteristic centrotemporal spikes
    • onset b/t 3 and 13; remission nearly always complete by age 15
    • Characteristics: unilateral parasthesias, speech arrest, T-C seizures occurring mostly at night
  • Benign Occipital Epilepsy (visual symptoms)
    • Onset between ages 3-10, more common in boys, often remits by puberty; inherited
    • Responsive to AEDs

Childhood Absence Epilepsy

  • Onset between 4 and 8 (second peak of onset at puberty known as juvenile absence epilepsy)
  • Easy to treat and spontaneous remission in 80%
  • Onset in adolescence more likely to experience generalized seizures and persist into adulthood

Juvenile Myoclonic Epilepsy

  • Onset late childhood, early adolescence
  • Involves myoclonic jerks of upper extremities generally associated with morning waking. No associated LOC, BUT 90-95% have generalized tonic-clonic seizures
  • Responds to AED’s but resolution is infrequent
  • Accounts for 10% of all epilepsies; genetically inherited (autosomal dominant)
  • IQ usually ok

Landau-Kleffner

  • “Acquired aphasia with convulsive disorder”
  • need abnormal EEG (usually over temporal areas) but no actual seizures are necessary for diagnosis
  • Age of onset b/t 2 and 11; follows a period of normal development
  • Characterized by sudden or gradual onset of auditory agnosia; may involve total unresponsiveness to language or progressive deterioration of expressive speech
  • Usually associated with behavioral difficulties as well
  • Seizure type varies, but most common is generalized motor seizures
  • Seizures and language deficits unresponsive to AED’s (current: steroid tx)
  • Earlier onset is related to poorer prognosis

Continuous spike-wave discharges during sleep (CSWS)

  • Continuous activity during >85% of non-REM sleep
  • Neuropsychological regression associated
  • Partial motor seizures, absence seizures

Etiology

  • Diagnosis = more than 1 unprovoked seizure
  • Symptomatic epilepsy – origin of seizure is identified (only 30% of cases; harder to control with AEDs)
  • Idiopathic – unknown seizure origin
  • Risk of new onset seizures is high in infancy and childhood, declines in adulthood, and then rises again in elderly
    • Most common cause in infancy and childhood are febrile seizures, congenital disorders, and perinatal injury
    • Most common cause in patients > 60 – cerebrovascular disease, brain tumors and neurodegenerative conditions
  • Febrile seizures – occur in 3-4% of all children, usually between ages of 6 months and 5 years; usually are brief, generalized tonic-clonic seizures (called simple febrile seizures).
    • Increased risk of subsequent epilepsy in children with complex febrile seizures – seizures lasting more than 15 minutes, or occurring more than once in 24 hours – some of these kids may have an underlying cause for epilepsy which is triggered by the fever
  • Metabolic factors – hypoglycemia, hypocalcemia, electrolyte imbalance, uremia, hepatic failure, hypoxia
  • Drug withdrawal – EtOH, barbiturates
  • Post-traumatic – CHI, SDH, EtOH w/ multiple falls. 50% of people who develop seizure disorders will do so in first year post-injury; 80% within four years
  • Birth injury – congenital malformations, infection, trauma, idiopathic
  • Relative to age of onset:
    • Perinatal – toxemia, infection, congenital defects, difficult birth
    • Young children – congenital abnormality, neonatal meningitis, neurocutaneous disorders
    • Adolescent – idiopathic, trauma, drug-related
    • Young adult – trauma, EtOH, neoplasm, drug-related, AVM, AIDS (cerebral toxoplasmosis)
    • Middle age – neoplasm, EtOH, vascular disorder, trauma
    • Late life – vascular disorder, neoplasm, degenerative, cysticercosis; CVA most common after age 65
  • Risk Factors:
    • Genetic predisposition
    • Cerebral insult
    • Precipitating conditions (e.g., EtOH, physical debilitation, emotional stress, video games/TV)

Differential Diagnosis

  • CT usually normal
  • Normal EEG does not rule out seizure disorder; sleep EEG more sensitive than waking
  • PET/SPECT: hyperperfused ictal foci; hypoperfused post-ictally; better at detecting foci than MRI/ CT

Pseudoseizures

Non-epileptogenic events, psychogenic seizures

  • Resembles an epileptic seizure but is not caused by neuronal discharge
  • Is not “voluntary”; etiology is emotional or psychological

•Possible distinguishing semiology: acute emotional disturbance may initiate, rare when sleeping or alone, gradual onset, crying during ictus, occasional talking, movements may be asynchronous, thrashing and may include side-to-side movements and pelvic thrusting, personal injury fairly rare, directed violence not unusual, react to avoidance testing, infrequent micturition and defecation, may be quite long, NO ictal epileptiform EEG abnormality

  • More prevalent in women, children, and adolescents
  • Risk Factors:
    • h/o sexual abuse,
    • epilepsy,
    • psychiatric disorder (esp. depression/anxiety),
    • or head injury/ PCS;
    • model for seizure disorder (family/friend),
    • traumatic life course, family discord/academic stress
  • Important: 50% also have “real” (i.e., electrical) seizures

Other conditions that mimic seizures

  • Episodic dyscontrol syndrome (i.e., recurrent rage attacks)
  • Cerebrovascular disturbance (e.g., syncope, cardiac arrhythmias, TIA, transient global amnesia)
  • Panic disorder
  • Breath holding spells in infants
  • Sleep disorders (e.g., narcolepsy, cataplexy)
  • Migraine
  • Metabolic disturbances (e.g., med reactions, hyperventilation, hypoglycemia)

Management

  1. Anti-epileptic drugs
    1. Use AED’s when seizures are prolonged or recurrent
    2. Seizure control can be established in up to 80% of pediatric population
  2. Surgery
    1. Focal resection – usually for partial complex
      1. In temporal lobectomies — 80% are seizure free or have significantly reduced seizures
      2. improvements in behavior and psychosocial functioning have been suggested
    2. Corpus callosotomy
      1. Used to control generalized seizures by preventing their spread across the hemispheres
      2. Tends to decrease frequency — but does not resolve disorder
    3. Functional hemispherectomy
  3. Vagus Nerve Stimulator
    1. VNS generator is implanted in left side of chest – stimulating lead is attached to left vagus nerve in carotid sheath
    2. Stimulus given off in cycles of 3 seconds on and 5 minutes off
  4. Ketogenic Diet
    1. 1/3 experience complete control of seizures
    2. adherence issues
  5. Multiple subpial transection – used when seizure site is inoperable (e.g., if in motor or language cortex). Involves inserting a sharpened probe under the pia to sever the cortical-cortical connections…essentially disconnecting the epileptogenic cortex) Can cause aphasia if dominant temporal lobe is transected

NP Effects of Anticonvulsants

  • May cause problems with attention, motor speed, memory, and processing speed – even when AED’s are within therapeutic range; *they may compound the cognitive difficulties and behavioral problems seen in people with epilepsy

Carbamazepine (Tegretol)

  • Few cognitive side effects
  • May improve speed of information processing, psychomotor speed and problem solving; may also decrease aggression and emotional lability
  • Interferes with BCPs

Valproic Acid (Depakote)

  • Minimal cognitive effects
  • May improve alertness
  • Few behavioral effects

Phenytoin (Dilantin)

  • Highest rate of side effects
  • Adverse effects on psychomotor speed, memory, and problem-solving
  • May result in progressive encephalopathy w/deterioration of intellection functioning, especially in children with MR or neuro problems
  • Dilantin (phenytoin) intoxication: nystagmus, ataxia, dysarthria
  • Due for frequent overgrowth of gum tissue (which can result in dental disease and heart issues), patients should have teeth cleaned 2X/year minimum

Phenobarbital

  • Inconsistent cognitive findings
  • Consistently related to hyperactivity, irritability and sleep disruption; may exacerbate premorbid problems

Polytherapy treatment

  • More negative impact on cognition and mood than monotherapy

Neuropsychological Findings in Epilepsy

  • IQ
    • In general, not associated with intellectual decline (except in syndromes such as tuberous sclerosis, Rett syndrome, chromosomal disorders, etc.) – when decline is noted, often associated with AED toxicity or status epilepticus
    • Co-occurs with MR (9-31%), autism (11-35%), and CP (18-35%)
  • Language
    • Expressive language more impaired than receptive
    • Dysnomia is common – may contribute to verbosity and circumstantial speech
    • Hypergraphia – excessive and compulsive writing
    • Reported memory problems may actually reflect subtle language difficulties
  • Perceptual-motor skills
    • TPT has been sensitive – total time, memory, and localization scores
    • Bender-gestalt – patients perform more poorly than controls
  • Memory
    • May reflect effects of continued abnormal activity or damage to CNS
    • Memory disturbance may be related to nature, extent, and location of pathology in temporal lobes
    • Long-term memory more affected than short-term memory
    • Localization of onset may affect memory impairments (i.e., verbal vs visual)
  • Attention
    • Deficits in attention tend to be present regardless of IQ
      • Generalized seizures – tend to show deficits on measures of sustained attention
      • Focal seizures – greater deficits on measures of selective attention
  • Executive functions
    • Trail making test, WCST, Category test
    • Frontal lobes affected by temporal/hippocampal discharges through temporal-frontal pathways
  • Motor skills
    • Decreased reaction time and psychomotor speed; overall slowing
  • Learning disabilities/Achievement
    • Higher risk for learning disorders
    • Etiology unclear
    • Seizure type, duration of disorder, severity of seizures and AED’s have NOT been found to be related to academic underachievement
    • May be related to impairments in language, memory, and attention

Factors Affecting Cognitive Deficits

  1. AED toxicity
  2. Etiology
    1. People with idiopathic seizures score higher on IQ tests
    2. Symptomatic epilepsy
  3. Seizure type and frequency – greater deficits seen with:
    1. Tonic-clonic, atypical absence, mixed seizures
    2. History of status epilepticus
    3. More frequent seizures
    4. Longer duration of disorder
  4. Early seizure onset
  5. Poor seizure control
  6. TLE surgery: Non-dominant temporal lobectomy – no consistent changes in cognition; Dominant temporal lobectomy – depressed verbal memory fairly common. Risk factors for post-op decline in verbal memory: dominant resection, intact pre-op neuropsych memory testing, intact pre-op Wada memory testing, absence of mesial temporal sclerosis (MTS) on imaging

Psychological findings:

  • Higher prevalence of depression (especially males with complex partial)
    • Higher suicide rates
  • Children with epilepsy have higher rates of psychiatric disturbance than general population
  • Neurological and psychosocial factors contribute to increased risk for psychological maladjustment
  • Neuro variables: underlying brain damage, localized epileptogenic activity in areas regulating emotion, etc
  • Family variables: significant predictors of behavior problems

Epilepsy Syndromes Based on Location

Temporal Lobe Epilepsy (TLE)

  • Group of conditions resulting in paroxysmal discharge within the temporal lobe; multiple etiologies
  • Unifying feature: vulnerability of temporolimbic structures (amygdala, hippocampus) to epileptogenesis – vascular anatomy; convergent inputs from multiple sensory areas; special excitability as reflected in bursting and kindling; NMDA receptors and pathological plasticity
  • Common denominator of TLE: temporal lobe spike focus
  • Common ictal manifestations (in sum: varied, complex, and difficult to differentiate from spontaneously occurring behavior; complex partial seizures):
  • Sensory alterations – subjective, but not necessarily any objective findings
  • Motor symptoms – automatisms, twitching, eye movements, speech problems, transient weakness, etc.
  • Autonomic manifestations – flushing, shortness of breath, apnea, cardiac symptoms, nausea/epigastric rising, etc.
  • Hallucinations/illusions – in any sensory modality; includes metamorphosia, micropsia, and macropsia
  • Experiential manifestations – memory flashbacks, déjà vu, jamais vu, feeling of a presence, depersonalization, derealization, etc.
  • Emotional manifestations – often negative, sudden, unpredictable, inappropriate (fear – most common)
  • “Typical” interictal behaviors** (i.e., “TLE personality”): preoccupation with religion/morality/ philosophical issues, hypergraphia, hyper/hypo sexuality, viscosity, increased irritability/temper outbursts, schizophrenia-like psychosis, fearfulness, humorlessness
    • Left sided focus: intellectualized affect, thought disorder, reflective style
    • Right sided focus: overemotionality, affective disorder, impulsive style; artistic creativity
  • Behaviors are “opposite” that seen in Kluver-Bucy syndrome (damage to temporolimbic structures resulting in placidity, hypersexuality, hyperphagia, hypermetamorphosis, loss of social bonds):
  • CAVEAT: I believe that current thinking and research questions the validity of a so-called “TLE personality”. In general, it is not supported by recent evidence.

Complex Partial Seizures of Extratemporal Origin

  • Relatively few cases documented in the literature

Clinical Characteristics of Complex Partial Seizure (CPS) of Frontal Lobe Origin:

  • Frequent seizures, often in clusters with many per day
  • Brief seizures lasting less than one minute
  • Sudden onset and offset with little or no postictal confusion
  • Prominent motor automatisms, usually complex
  • Aggressive sexual automatisms as part of motor automatisms
  • Vocalizations of variable complexity
  • Frequent warnings, usually nonspecific
  • Complex partial status epilepticus possible
  • Bizarre attacks that appear hysterical
  • Stereotyped pattern

In Sum: similar to Temporal Lobe Epilepsy (TLE); bizarre movements and vocalizations, behavioral automatisms

Clinical Characteristics of CPS of Occipital Lobe Origin:

  • Elemental visual hallucinations
  • Contralateral eye deviation
  • Pulling or movement sensation in eyes in the absence of detectable motion
  • Rapid forced blinking or eyelid flutter
  • Ictal blindness – blackout or whiteout secondary to rapid spread via the splenium (infrequent)
  • Static visual field defects