One area of controversy in the field of epilepsy is how to describe the seizures experienced by patients with epilepsy and how to categorize them in order to sensibly discuss and treat epilepsy. Several congresses have been convened to work on this problem, and out of them have come the International Classification of Epilepsies and Epileptic Syndromes. This classification has broadly defined seizures as either generalized ("seizures in which the first clinical changes indicate initial involvement of both hemispheres" or sides of the brain) or partial (location related or focal/local/partial) seizures.
Generalized Epilepsy
Idiopathic Generalized Epilepsies
These are forms of generalized epilepsies that have a generalized onset involving both sides of the brain. EEG (electroencephalography) recordings of the seizures show bilateral abnormal seizure patterns that are synchronized and symmetrical. Recordings done when no seizures are occurring are normal.
Benign Neonatal Familial Convulsions
These are rare seizures that occur just after birth (typically on the third or fourth day of life) and manifest as rhythmic shaking of the body with or without breath holding. This condition is heritable, and 14 percent of these babies will go on to develop epilepsy.
Benign Neonatal Convulsions
These are rare seizures which occur just after birth (typically on the third or fourth day of life) and manifest as rhythmic shaking of the body with or without breath holding. This condition is heritable, and 14 percent of these babies will go on to develop epilepsy.
Benign Myoclonic Epilepsy in Infancy
These occur in otherwise normal children during their first or second year of life. The seizures consist of brief jerks of the body or part of it, similar to those experienced by most people as they are falling asleep. EEG recordings show brief burst of seizure activity, especially during the early stages of sleep. Later in life, a few children who experience this will develop generalized tonic (body stiffening)–clonic (body rhythmically shaking) seizures, and children with benign myoclonic epilepsy in infancy can have mild delay in development and minor personality disorders.
Childhood and Juvenile Absence Epilepsy
These seizures are associated with a momentary loss of consciousness (frequently not realized by others) with or without abnormal movements or loss of body tone and collapse. The childhood form occurs during early school years, may occur several times a day, and is associated with the child later (during teens) developing generalized tonic-clonic seizures (GTCS). The juvenile form usually has an onset around puberty, and the events are not uncommonly preceded by GTCS. The EEG shows bilateral, symmetrical spike-waves that are synchronized and occur at a frequency of three per second.
Juvenile Myoclonic Epilepsy
Also termed impulsive petit mal epilepsy, these seizures occur around puberty and consist of single or repetitive jerking that is irregular, arrhythmic and occurs bilaterally, predominately in the arms. GTCS and, infrequently, absences may also occur. The most common time to see the seizures is shortly after awakening or when a person is sleep deprived.
Epilepsy with GTCS on Awakening
These seizures occur during the teen years and may be associated with absence or myoclonic seizures. The most common time for the seizures to occur is shortly after awakening from sleep (>90 percent), but they can also occur in the evening during periods of relaxation. Juveniles with this type of epilepsy will demonstrate a susceptibility to light-induced seizures.
Generalized Cryptogenic or Symptomatic Epilepsies
West Syndrome
Also called infantile spasms, this syndrome is manifest by seizures which start in the first year of life and consist of spasms with the body flexing or extending, or the head may nod. There is arrest in the baby's development and the EEG has a characteristic pattern (hypsarrhythmia) that is diagnostic. The prognosis for the baby is a function of how well the baby responds to treatment with ACTH (adrenocorticotropic hormones) or steroids. There are two subgroups of this syndrome:
Symptomatic group: The infant has signs of an injured brain (delay in development, signs of abnormal function of parts of the nervous system or MRI/CT scans showing areas of injury in the brain) that pre-date the onset of the seizures.
Cryptogenic group: There is no known reason for the seizures and examination of the baby is normal.
Lennox-Gastaut Syndrome
Children with this syndrome have intractable seizures of multiple types (absence, tonic axial, atonic, myoclonic, GTCS or partial). The frequency of the seizures is high and episodes of status are not unusual. The children exhibit psychomotor retardation, and the EEG recordings are characteristic (generalized slow [less than 2 ½ per second] spike and wave pattern during clinical seizures). This condition can occur in children who had West syndrome during infancy.
Symptomatic group: The child has signs of an injured brain (delay in development, signs of abnormal function of parts of the nervous system or MRI/CT scans showing areas of injury in the brain) that predate the onset of the seizures.
Cryptogenic group: There is no known reason for the seizures, and examination of the child is normal.
Epilepsy with Myoclonic-Astatic Seizures
These seizures are mixed and include myoclonic, astatic and myoclonic-astatic seizures in association with absences, GTCS and tonic seizures as well as non-convulsive status. When the status occurs, it is usually on awakening and is characterized by apathy or stupor in association with infrequent myoclonus. The onset of this condition is during early childhood and is frequently preceded by a febrile seizure. The EEG has a characteristic evolution over time, and the outcome of children with this condition is variable.
Epilepsy with Myoclonic Absences
Children with this type of disorder experience absences usually accompanied by severe clonic jerking of both sides of the body. There can also be tonic stiffening of the body during these episodes. These can occur several times during the day. The age of onset is about 7 years, and the EEG shows characteristic changes during these episodes similar to that seen that seen with childhood absences.
Symptomatic Generalized Epilepsies and Syndromes
These occur most commonly in infancy and childhood, and the seizures are characterized by generalized seizures and EEG recordings that differ from those described in the idiopathic generalized epilepsies. Not uncommonly, the child will exhibit more than one type of seizure, and the EEG is characterized by bilateral asymmetrical activity that is less rhythmic than that seen with the idiopathic generalized epilepsies. The child has clinical signs of a diffuse encephalopathy.
Symptomatic Generalized Epilepsies of Specific Etiologies
These are seizures which are a prominent feature of a disease or disorder due to malformations of portions of the brain that cause such seizures as infantile spasms. Some malformations can cause characteristic seizures such as hypothalamic hamartomas causing gelastic seizures and tuberous sclerosis; infants with tuberous sclerosis commonly exhibit West syndrome, which evolves into generalized and partial seizures with aging.
Proven or Suspected Inborn Errors of Metabolism
These are seizures, generalized or partial, that result when breakdown products of chemical reactions in the body accumulate, triggering the seizure or prohibiting a particular substance important to the normal function of the nervous system from being made—the resultant deficit leads to seizures. The seizures may be stereotypic for the condition or may be mixed. The age for onset of the seizures varies with the condition, with some starting at birth, some in infancy, some in childhood and some in the teens. There are even a few that do not present until adulthood. A feature of these disorders is they are heritable.
Generalized Symptomatic Epilepsies of Nonspecific Etiology
Early Myoclonic Encephalopathy
The onset of this condition is usually by 3 months of age; it starts with myoclonic seizures and evolves to more severe seizures. EEG (electroencephalograph) recordings show bursts of abnormal activity interspersed with suppression of the brain's normal activity, and this pattern evolves into a hypsarrhythmia. Babies with this condition arrest in their development as the seizures worsen.
Early Infantile Epileptic Encephalopathy with Suppression Burst
This starts during the first few months of life and is characterized by frequent tonic spasms of the body and an EEG recording similar to that seen with early myoclonic encephalopathy. This is frequently associated with developmental arrest or delay and can evolve into West syndrome by 4 to 6 months of age.
Epilepsies and Syndromes Undetermined as to Whether They are Focal or Generalized
Neonatal seizures—These can be difficult to appreciate because of the immaturity of the nervous system. Manifestations of these types of seizures may include such subtle behavior as deviation of the eyes to one side with or without jerking, repetitive movements of the mouth mimicking lip smacking, swallowing, sucking, etc., pedaling or swimming movements in the arms/legs and apneic episodes. Premature infants may exhibit tonic extension in the arms or legs. Infrequently, there can be clonic or myoclonic seizures. These last types have greater significance with regards to the infant’s prognosis.
Severe Myoclonic Epilepsy in Infancy
This form of epilepsy evolves out of febrile convulsions, usually in infants with a family history of febrile seizures or epilepsy. The seizures evolve during the first year of life and consist of generalized or unilateral clonic febrile seizures and evolve into myoclonic seizures and partial seizures later. There can be associated psychomotor retardation that becomes more obvious during the second year.
Epilepsy with Continuous Spike-Wave During Slow-Wave Sleep
This is an EEG diagnosis, with the child exhibiting seizures of varying types during deep sleep (partial or generalized seizures) and also absences while awake. There can be associated neuropsychological disorders.
Special Syndromes
Febrile convulsions—This is a relatively benign condition seen during early childhood. The seizures are generalized and occur in association with fevers. Usually they are brief, but when prolonged there is a chance of injury to the central nervous system that then results in a permanent dysfunction. As only 4 percent of children having these type of seizures go on to develop epilepsy, routine use of medications to prevent these is unusual unless they become a repetitive problem.
Focal or Partial Epilepsy
These are localization-related epilepsies and syndromes that are referred to as partial, focal or local epilepsies and syndromes. Either the feature or pattern of the seizures or the clinical investigation demonstrate a focal involvement of the brain in these conditions. Patients with these conditions can have a focal area of brain that functions abnormally, has a lesion or tumor or has developed abnormally. The abnormal area is responsible for the abnormal electrical discharges that result in the seizure. Some may have several areas capable of generating abnormal seizures, and some may experience a secondary generalization of the seizure activity with the seizure coming to resemble a generalized seizure in very short (within seconds) order after onset of electrographic onset of the focal activity. Not uncommonly, the onset may resemble a generalized seizure to a casual observer. In certain types of focal epilepsies (idiopathic age-related focal epilepsies), mirror areas of the two halves of the brain may be capable of generating seizures.
Focal seizures are commonly described as a function of their point of onset in the brain. To do this, a careful history is obtained and extensive EEG recordings coupled with videotaping of the patient's behavior are done to better appreciate what the first signs and symptoms of the typical seizure are and how these symptoms and signs progress as the seizure progresses. As a result, descriptions of syndromes related to anatomic localization are becoming available.
Temporal Lobe Epilepsies
These include simple partial, complex partial and secondarily generalized seizures. The simple partial seizures typically have autonomic (pupillary dilation, flushing in the face, arrest of breathing) and/or psychic symptoms (fear, panic, rage) as well as auditory and olfactory sensations, including illusions. The complex partial seizures usually begin with an arrest in motor activity followed by oroalimentary automatisms such as belching, rumbling in the abdomen. Other automatisms then follow, which typically encompass repetitive, complex movement such as opening and closing a door. The actual seizure usually lasts less than a minute and is followed by confusion and amnesia for a variable period with recovery occurring gradually.
- Temporal lobe seizures can arise from the medial side of the lobe (mesial temporal lobe seizures, limbic seizures, rhinencephalic seizures) or the lateral side (lateral temporal lobe seizures).
- Mesial temporal lobe seizures start deep within the brain, so EEGs done between seizures are typically normal. The chances of recording abnormal activity is greatly enhanced by using sphenoidal electrodes (thin wire electrodes inserted to lay at the base of the skull below the central part of the brain using thin needles temporarily inserted through the cheek). These seizures usually start with a rising sensation in the abdomen, nausea with autonomic signs and psychic symptoms following.
- Lateral temporal lobe seizures are characterized by auditory hallucinations/illusions, dreamlike state, disorders in language reception and output, and visual symptoms. The seizure can then move to involve the medial temporal lobe, occipital lobe or parietal lobe with onset of corresponding symptoms referable to these areas of the brain.
Because the memory circuits originate in the temporal lobe, repeated seizure activity that involves these structures can cause difficulties with memory and intellectual function. These seizures typically start in childhood or young adulthood, tend to cluster and are frequently associated with a history of febrile convulsions and/or a family history of seizures.
Frontal Lobe Epilepsies
These are generally short, complex partial seizures with minimal or no post-ictal confusion. Secondary generalization is common and rapid. Simple partial seizures can also occur. The seizures contain a prominent motor component that is either postural or tonic. At the onset of these seizures, complex gestures are common, and if the activity spreads to the other half of the brain, falling is common. Given the complex nature of these seizures, they are not uncommonly mistaken for psychogenic seizures. The constellation of signs and symptoms that occur as the seizure starts and progresses offers clues to the site of origin of the seizure. The seizures take their name for the area of the frontal lobe from which they arise.
Seizures Types
Supplementary Motor Seizures
The patient assumes a fencing position with the arms or assumes another posture or exhibits focal, tonic activity. There is speech arrest or vocalizations.
Cingulate seizures: These are complex partial seizures with complex, automatismal gesturing occurring at the onset. Commonly, there are changes in mood and affect and autonomic signs.
Anterior frontopolar seizures: With these seizures, one sees forced thinking, loss of contact with the environment and aversive (movement toward the side of the body opposite the side of brain generating the seizure) head and eye movement. As these seizures evolve, the head and eyes may move back to the side of seizure onset and there may be jerking of the trunk as well as autonomic signs, and the patient may fall.
Dorsolateral Seizures
Dorso refers to the upper half of the frontal lobe. These seizures arise in the upper, lateral part of the lobe and typically cause tonic and, occasionally, clonic motor activity with associated versive head and eye movement and speech arrest.
Orbitofrontal Seizures
These are complex partial seizures where automatisms (motor and gestural) predominate with olfactory hallucinations/illusions and autonomic signs also occurring.
Opercular Seizures
A primary feature of these seizures are signs and symptoms of alimentary tract involvement, including chewing, swallowing, salivation, epigastric sensation, speech arrest and sound generation. There can be speech arrest, fear and autonomic signs. If the activity spreads, secondary sensory changes may occur, such as numbness.
Motor Seizures
These are usually simple partial seizures and are localized based on what part of the body has movement at the onset of the seizure. If the face's motor region is involved, there will commonly be speech arrest, difficulty in swallowing or vocalizations of sounds in association with the tonic or clonic movements of the face's muscles on the side opposite to the area of the brain generating the seizure. These seizures frequently spread (referred to as "marching"—that is, seizure activity spreads up an arm or leg, marching to involve more and more adjacent muscles). After the seizure, there is frequently a weakness for a variable length of time of muscles that were active in the seizure.
Other Epilepsies
Parietal Lobe Epilepsies
These are typically simple partial seizures that can secondarily generalize. Rarely, they can evolve into complex partial seizures. Seizures from this area of the brain typically manifest sensations such as tingling, numbness, loss of the extremity, crawling, coldness or electric sensations in regions of the body but more complex sensations such as feeling that an extremity is moving, or complex alimentary sensations may occur. Rarely, there may be a painful sensation. The involvement may march, as with motor seizures of the frontal lobe. There can be complex visual symptoms, such as metamorphosis with distortions, foreshortening and elongation. Severe vertigo or disorientation is a sign of involvement of the lower part of the lobe. If the dominant (usually the left) lobe is involved, there can be dysfunction in processing language input and output. These seizures commonly generalize secondarily.
Occipital Lobe Epilepsies
There are two categories of localization-related epilepsies or syndromes with regards to their etiology. Each has several subtypes of seizures.
These are simple partial seizures that commonly undergo secondary generalization. With spread, the seizure can evolve into a complex partial seizure. The initial visual symptoms are usually sparks, flashes or phosphenes but may be scotoma, hemianopsia or amaurosis with the symptoms occurring toward the side opposite the involved part of the brain. There can also be distortion of vision with objects appearing altered in size (too large or small), shape or tilted. Distances may also appear altered.
Idiopathic Localization-Related Epilepsies
These are age-related epilepsies in children whose clinical examinations and testing fail to demonstrate anything other than a focal area of abnormal electrical discharge as recorded by EEG. There is no known causative factor for these children's epilepsies except for a number being hereditarily acquired. These seizures are brief, not associated with neurologic or intellectual abnormalities. The pattern of seizure is generally constant for any given child.
Benign Childhood Epilepsy with Centrotemporal Spikes
These are focal seizures commonly occurring around sleep that involve the face, can have a sensory component and can generalize into a GTCS. They are most common in males and can start as early as age 3 and typically burn out between ages 15 and 16.
Landau-Kleffner syndrome is an atypical form of benign partial epilepsy occurring in the speech region of the left frontal lobe.
Childhood Epilepsy with Occipital Paroxysms
These seizures start with visual symptoms such as amaurosis, phosphenes, illusions or hallucinations; 25 percent of patients with this condition will have migraine headache prior to onset of their seizures. The seizure can then spread to involve the posterior temporal lobe and central areas of the brain with onset of behavior that can include clonic activity in one side of the body or complex patterns of body movement. Otherwise, these seizures are very similar to benign childhood epilepsy with centrotemporal spikes.
Symptomatic Focal Epilepsies
These are epilepsies that are focal in origin and are due to known or suspected disorders of the brain as demonstrated by clinical investigations such as CT or MRI scans, laboratory testing, etc.
Chronic Progressive Epilepsia Partialis Continua of Childhood (Kojewnikow Syndrome)
This is one of the two forms of Kojewnikow syndrome (the other being Rasmussen's syndrome) which is a partial motor seizure that can progress to a myoclonic seizure involving the same muscle groups as are involved by the motor seizure. These type of seizures can begin at any age and are usually associated with a demonstrable lesion such as a tumor or vascular abnormality. The seizure disorder will not progress unless the causal lesion does.
Syndromes Characterized by Seizures with Specific Modes of Precipitation
These are seizures that reliably result from an environmental or internal factor. A memory or recognition of a specific pattern triggering a complex partial seizure would be an example. Less common would be partial seizures triggered by a simple sensation (e.g., a smell); as such stimulus-specific induced seizures are usually generalized. Partial seizures can also be caused by sudden, unexpected arousal, but, again, generalized seizures are more common in this setting.