Epilepsy Flashcards
Epilepsy Epidemiology:
oIn the United States, about 6.5 persons per 1,000 population are affected with
recurrent unprovoked seizures, or epilepsy
o About 40 million people are affected worldwide
o 2% of the general population will suffer a seizure at some point in their life
Epilepsy Epidemiology: Risk Factors
o Family History (genetic component)
o History of CNS infection (meningitis or encephalitis)
o Head trauma, particularly penetrating head trauma.
o Prior cranial surgery
o History of stroke, tumor, AVM or other mass lesion
o Electrolyte derangement
o Drugs/Toxin.
•There are countless (>200 (click link) drugs which lower the
seizure threshold. We often see provoked seizures from
inappropriate rapid cessation of benzodiazepines, baclofen and
barbiturates.
• Use of Bupropion is particularly common cause of seizure as study
demonstrated that bupropion-induced seizures were the third most
common cause of drug-induced seizures after cocaine ingestion
and benzodiazepine withdrawal
Pathophysiology:
• An epileptic seizure is the result of a temporary physiologic dysfunction of the
brain caused by a self-limited, abnormal synchronous electrical discharge of
cortical neurons.
• A seizure is a transient epileptic event, a symptom of disturbed brain function.
Although seizures are the cardinal manifestation of epilepsy, not all seizures
imply epilepsy.
•Epilepsy is a chronic disorder, or group of chronic disorders, in which the
indispensable feature is recurrence of seizures that are typically unprovoked and
usually unpredictable.
•There are many different kinds of seizures, each with characteristic behavioral
changes and electrophysiological disturbances that usually can be detected on
scalp EEG recordings.
• The particular manifestations of any single seizure depend on several factors:
o whether most or only part of the cerebral cortex is involved at the
beginning
o functions of the cortical areas where the seizure originates
o subsequent pattern of spread of the electrical ictal discharge within the
brain
o extent to which subcortical and brain stem structures are engaged
CLASSIFICATION OF SEIZURES AND EPILEPSY:
• Accurate classification of seizures and epilepsy is essential for understanding
epileptic phenomena, developing a rational plan of investigation, making
decisions about when and for how long to treat, choosing the appropriate
anticonvulsant drug, and conducting scientific investigations that require
delineation of clinical and EEG phenotype
• The classification used today is the 1981 Classification of Epileptic Seizures
developed by the International League Against Epilepsy (ILAE). This system
classifies seizures by clinical symptoms supplemented by EEG data.
•Inherent in the classification are two important physiologic principles:
o First, seizures are fundamentally of two types: those with onset limited to
a part of the cerebral hemisphere (partial or focal seizures) and those that
seem to involve the brain diffusely from the beginning (generalized
seizures).
o Second, seizures are dynamic and evolving; clinical expression is
determined as much by the sequence of spread of electrical discharge
within the brain as by the area where the ictal discharge originates.
o Both the generalized and partial seizures are further divided into subtypes.
• For partial seizures, the most important subdivision is based on
consciousness, which is preserved in simple partial seizures or lost
in complex partial seizures.
• Simple partial seizures may evolve into complex partial
seizures, and either may evolve into secondarily
generalized seizures. In adults, most generalized seizures
have a focal onset whether or not this is apparent clinically.
• For generalized seizures, subdivisions are based mainly on the
presence or absence and character of ictal motor manifestations.
Partial seizures: Simple
• Simple partial seizures result when the ictal discharge occurs in a limited and
often circumscribed area of cortex, the epileptogenic focus.
• Almost any symptom or phenomenon can be the subjective (aura) or observable
manifestation of a simple partial seizure.
o Especially common auras include an epigastric rising sensation, fear, a
feeling of unreality or detachment, deja vu and jamais vu experiences, and
olfactory hallucinations.
o Patients are aware of their surroundings and may interact with others
during these episodes.
Partial seizures: Complex
• Complex partial seizures, on the other hand, are defined by impaired
consciousness and imply bilateral spread of the seizure discharge, at least to basal
forebrain and limbic areas.
o In addition to loss of consciousness, patients with complex partial seizures
usually exhibit automatisms such as lip smacking, repeated swallowing,
clumsy perseveration of an ongoing motor task, or some other complex
motor activity that is undirected and inappropriate.
o Postictally, patients are confused and disoriented for several minutes, and
determining the transition from ictal to postictal state may be difficult
without simultaneous EEG monitoring.
o Of complex partial seizures, 70-80% arise from the temporal lobe; foci in
the frontal and occipital lobes account for most of the remainder.
Generalized seizures: Tonic Clonic seizures
• Generalized tonic-clonic seizures are characterized by abrupt loss of
consciousness with bilateral tonic extension of the trunk and limbs (tonic phase),
often accompanied by loud vocalization as air is forcedly expelled across
contracted vocal cords (epileptic cry), followed by synchronous muscle jerking
(clonic phase).
o In some patients, a few clonic jerks precede the tonic-clonic sequence; in
others, only a tonic or clonic phase is apparent.
o Postictally, patients are briefly unarousable, then lethargic and confused,
often preferring to sleep
Generalized seizures:
Absence (petit mal) seizures
momentary lapses in awareness that are
accompanied by motionless staring and arrest of ongoing activity.
o Absence seizures begin and end abruptly; they occur without warning or
postictal period.
o Longer attacks may be accompanied by myoclonic jerks of the eyelid or
facial muscles, variable loss of muscle tone and automatisms.
o When the beginning and the end of the seizure are less distinct, or if tonic
and autonomic components are included, the term atypical absence seizure
is used.
o Atypical absences are seen most often in retarded children with epilepsy
or in epileptic encephalopathies, such as Lennox-Gastaut syndrome (see
below).
Generalized seizures:
Myoclonic seizures
characterized by rapid, brief muscle jerks that can occur
bilaterally, synchronously or asynchronously, or unilaterally.
o These range from isolated small movements of the face, arm, or leg
muscles, to massive bilateral spasms simultaneously affecting the head,
limbs, and trunk.
Generalized seizures: Atonic (astatic) seizures
also called drop attacks.
o These are characterized by sudden loss of muscle tone, which may be
fragmentary (head drops) or generalized, resulting in a fall.
Neonatal seizures
• The most common sign of neurologic dysfunction in the newborn.
• They occur in 0.5% of all newborns, more often in preterm babies, and frequently
signify injury to the developing brain.
•The current classification recognizes four general patterns: subtle, clonic, tonic,
and myoclonic. The prognosis is directly related to the etiology of the seizures.
Infantile spasms
• This is an age specific form of epilepsy that may be idiopathic or symptomatic.
• When all clinical data are considered, including results of imaging studies, only
about 15% of the patients are now classified as idiopathic.
• Only 5-10% of children with infantile spasms have normal or near normal development, and more than 66% have severe disabilities.
• Symptomatic cases have various etiologies: cerebral dysgenesis, tuberous
sclerosis, phenylketonuria, intrauterine infections, or hypoxic-ischemic injury.
• Seizures are characterized by sudden flexor or extensor spasms that involve the
head, trunk, and limbs simultaneously. The attacks usually begin before 6 months
of age.
• The EEG is grossly abnormal, showing chaotic, high voltage slow activity with
multi focal spikes, a pattern termed hypsarrhythmia.
• The treatment of choice is adrenocorticotropic hormone (ACTH); spasms are
notoriously refractory to usual anticonvulsant medications, with the exception of
Vigabatrin (not available in the US).
o ACTH controls the spasms and normalizes the EEG.
Childhood Absence Epilepsy
• This disorder begins most often between the ages of 4 and 12 years of age and is
characterized predominantly by recurrent absence seizures, which, if untreated,
can occur literally hundreds of times per day.
• EEG activity during the absence attacks is characterized by stereotyped,
bilaterally synchronous 3Hz spike and wave discharges.
• Generalized tonic-clonic seizures also occur in 30 to 50% of cases. Most
children are intellectually and neurologically intact.
• Ethosuximide is a treatment option that is frequently tested but infrequently used
in clinical practice.
Lennox-Gastaut Syndrome.
• This term is applied to a heterogeneous group of childhood epileptic
encephalopathies that are characterized by mental retardation, uncontrolled
seizures, and a distinctive EEG pattern.
• The syndrome is not a pathologic entity, because clinical and EEG manifestations
result from brain malformations, perinatal asphyxia, severe head injury, CNS
infection, or, rarely, a progressive degenerative or metabolic syndrome. A cause can be identified in 50 to 60% of cases.
• Seizures usually begin before the age of 4 years, and about 25% of children have
a history of infantile spasms.
• No treatment is effective. Refractory cases may be considered for corpus
callosotomy
Febrile Seizures.
•These are generalized convulsions that occur during a febrile illness that does not
involve the brain.
• Most occur in children between the ages of 6 months and 4 years; they are
occasionally seen in children as old as 6 or 7 years.
•Typically the seizure occurs early in febrile illness, while the temperature is
rapidly rising.
• Although generalized convulsions are the rule, focal features or Todd paralysis
(transient weakness) are seen in about 10% of patients.
• About one third of children with febrile seizures have more than one. Recurrence
is highest in infants whose first febrile seizure occurred before the age of 1 year
and in children with a family history of febrile convulsions.
• The risk of developing epilepsy is increased in children with febrile seizures, but
the magnitude of the risk depends on several factors.
o In children with simple febrile seizures, the risk of later epilepsy is 2-3%.
o The incidence of epilepsy increases to 10-13% in children who have had a
complex febrile seizure, or who were neurologically abnormal before the
first seizure.
