Epilepsy and Seizures Clinical Presentation

Updated: Jul 12, 2016
  • Author: David Y Ko, MD; Chief Editor: Selim R Benbadis, MD  more...
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Presentation

History

The diagnosis of epileptic seizures is made by analyzing the patient's detailed clinical history and by performing ancillary tests for confirmation. Someone who has observed the patient's repeated events is usually the best person to provide an accurate history. However, the patient also provides invaluable details about auras, preservation of consciousness, and postictal states. A key feature of epileptic seizures is their stereotypic nature.

Questions that help to clarify the type of seizure include the following:

  • Was any warning noted before the seizure? If so, what kind of warning occurred?
  • What did the patient do during the seizure?
  • Was the patient able to relate to the environment during the seizure and/or does the patient have recollection of the seizure?
  • How did the patient feel after the seizure? How long did it take for the patient to get back to baseline condition?
  • How long did the seizure last?
  • How frequently do the seizures occur?
  • Is anything known to precipitate the seizures?
  • Has the patient shown any response to therapy for the seizures?
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Physical Examination

The clinical diagnosis of seizures is based on the history obtained from the patient and, most importantly, the observers. Physical examination helps in the diagnosis of specific epileptic syndromes that cause abnormal findings, such as dermatologic abnormalities (eg, neurocutaneous syndromes such as Sturge-Weber, tuberous sclerosis, and others). In addition, patients who for years have had intractable generalized tonic-clonic seizures are likely to have suffered injuries requiring stitches.

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Overview of Epileptic Seizures Classification

In 1981, the International League Against Epilepsy (ILAE) developed an international classification of epileptic seizures that divides seizures into 2 major classes: partial-onset seizures and generalized-onset seizures. Partial-onset seizures begin in a focal area of the cerebral cortex, whereas generalized-onset seizures have an onset recorded simultaneously in both cerebral hemispheres. Some seizures are difficult to fit into a single class, and they are considered unclassified seizures. This classification is still widely accepted.

Other classifications, such as a semiologic classification advanced by Luders and others, have been proposed. [24] A refinement of this semiologic classification led to a 5-dimensional (5-D), patient-oriented classification of epilepsy. [25]

The ILAE commission on classification developed additional reports. [26, 27] In 2006, a new proposed classification of seizures was published. [26, 27] The 2 main changes in this classification are (1) the use of focal rather than partial and (2) the proposal that a single seizure in the setting of a predisposition for further seizures be considered epilepsy. In 2010, the ILAE commission on classification explained in more detail the decision for using the changes in terminology in the revised proposed classification. [28] Nevertheless, there remains controversy over the classification of epileptic seizures among clinicians. A revised proposal is expected after the 2013 ILAE meeting.

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Focal-Onset Seizures

Focal-onset seizures are further classified as simple focal seizures, complex focal seizures, and secondary generalized tonic-clonic seizures.

Simple and complex focal seizures

The defining element of simple focal seizures is a seizure with preserved consciousness. A complex partial seizure is defined as one in which there is some alteration or impairment of consciousness. Many patients with complex focal seizures have an aura warning them of their seizure; the aura itself is a simple focal seizure. The many kinds of simple focal seizures include sensory, motor, autonomic, and psychic types. Any discrete experience that involves the cerebral cortex could be a simple focal-onset seizure.

The diagnosis of the seizure type is based on the repeated, stereotypic occurrence of the same experience in association with focal electroencephalographic (EEG) changes or on recurrent auras leading to a complex focal-onset seizure or a secondary generalized seizure. Resolution of the recurrent clinical phenomena with anticonvulsants is presumptive but not diagnostic evidence for epileptic seizures.

The clinical diagnosis is difficult, as many stereotypic auras may be induced in areas of the cerebral cortex that are not recorded well on a typical EEG. About 20-40% of auras have an ictal correlate on the scalp EEG. Simple focal seizures may last a few seconds to a few minutes. However, if the aura lasts longer than 30 minutes, it is considered simple focal status epilepticus by definition.

As noted above, consciousness is impaired during a complex focal seizure. In practice, assessing the patient's history to determine whether consciousness was impaired is difficult. The most common way to assess preserved consciousness is asking patients if they remembered the event. Patients may be able to remember their aura but are unaware that they were briefly unable to respond to the environment.

A complex focal seizure typically begins with behavioral arrest and is followed by staring, automatisms, and postictal confusion. Typical automatisms are chewing, lip smacking, mumbling, and fumbling with the hands. Dystonic posturing of the contralateral upper extremity is often seen when a complex partial seizure originates from the mesial temporal lobe. A typical complex focal seizure lasts about 60-90 seconds and is followed by brief postictal confusion. However, generalized weakness, asthenia, and fatigue may last for a few days.

Complex focal seizures of frontal-lobe origin may feature bizarre motor behaviors such as bicycling or a fencing posture, and they may have more of a nocturnal occurrence. These seizures have more prominent motor features than those of complex focal seizures of temporal-lobe onset. Frontal lobe–onset complex focal seizures may have a fast postictal recovery to baseline, and they often appear in clusters.

The great majority of complex focal seizures have an ictal correlate on the EEG. A normal alpha rhythm during behavioral impairment of consciousness is highly suggestive of nonepileptic seizures, but this should be interpreted by an experienced epileptologist, as some true seizures may not have surface EEG changes, and some true seizures can have somewhat atypical features (eg, bilateral motor activity is present, but the patient may be conscious from supplementary motor seizures).

Secondary generalized seizures

Secondary generalized seizures often begin with an aura that evolves into a complex focal seizure and then into a generalized tonic-clonic seizure. However, a complex focal seizure may evolve into a generalized tonic-clonic seizure without a preceding aura, or an aura may evolve into a generalized tonic-clonic seizure without an obvious complex focal seizure.

Clinically classifying a generalized tonic-clonic seizure as being secondarily generalized (focal onset) or primarily generalized is difficult on the basis of the history alone. In most cases, the association with prominent amnesia for the aura increases with the severity of a secondary generalized seizure.

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Generalized-Onset Seizures

Generalized-onset seizures are classified into 6 major categories, as follows:

  • Absence seizures
  • Myoclonic seizures
  • Clonic seizures
  • Tonic seizures
  • Primary generalized tonic-clonic seizures
  • Atonic seizures

Each seizure type is classified by its clinical and electroencephalographic (EEG) manifestations. Definitive classification of seizures is best made by ictal recordings over a period of several days to capture seizures.

Absence seizures

Absence seizures are brief episodes of impaired consciousness with no aura or postictal confusion. They typically last less than 20 seconds and are accompanied by few or no automatisms. Of the automatisms that develop, the facial ones are most common, with repetitive blinking occurring most often. Hyperventilation or photic stimulation frequently precipitates these seizures, which typically begin during childhood or adolescence and may persist into adulthood.

A diagnosis of new-onset absence seizures in adulthood is not likely in the vast majority of cases. (Adults often have complex focal seizures with relatively minor automatisms.) Confusion arises when patients and some healthcare providers incorrectly use the term “absence seizure” (or “petit mal seizure”) and “petit mal/absence seizure” to describe a seizure that is not “grand mal.”

Twin studies have demonstrated a significant inherited predisposition for typical childhood absence seizures. In children, the seizures are subtle, manifesting as “staring episodes” and often going unrecognized until the child develops a generalized tonic-clonic (previously known as “grand mal”) seizure. Sudden decreased performance in school or overall attention may be a subtle manifestation of frequent absence seizures.

The classic ictal EEG correlate of absence seizures consists of 3-Hz generalized spike-and–slow wave complexes that may be induced by activation during EEG by hyperventilation and sometimes photic stimulation. EEG abnormalities may persist into adulthood despite the absence of clinical seizures. However, compared with the EEG discharges in children, those in adults occur less often, are less well formed, and are of lesser amplitude.

Myoclonic, clonic, and tonic seizures

Myoclonic seizures consist of brief arrhythmic jerking motor movements that last less than 1 second and often cluster within a few minutes. If the seizures evolve into rhythmic jerking movements, they are classified as evolving into a clonic seizure. Myoclonus is not always epileptic in origin. For example, the myoclonic jerks during phase I of sleep are normal release phenomena. The classic ictal correlate of myoclonic seizures on the EEG consists of fast polyspike-and–slow wave complexes.

Clonic seizures consist of rhythmic jerking motor movements with or without impairment of consciousness; they can have a focal origin. The focal seizures are classified as simple or complex partial seizures. The typical generalized clonic seizures simultaneously involve the upper and lower extremities. The ictal EEG correlate consists of bilateral, rhythmic, epileptiform discharges.

Tonic seizures consist of sudden-onset tonic extension or flexion of the head, trunk, and/or extremities for several seconds. These seizures typically occur in relation to drowsiness, shortly after patients fall asleep, or just after they awaken. Tonic seizures are often associated with other neurologic abnormalities.

The ictal correlate of tonic seizures in the EEG includes an electrodecremental response, which is a high-frequency electrographic discharge in the beta frequency (also known as "beta buzz"), with a relatively low amplitude compared with that of the background rhythm. This pattern may evolve into slow spike-and-wave complexes or diffuse polyspikes.

Primary generalized tonic-clonic seizures

Tonic-clonic seizures are commonly referred to as grand mal seizures. They consist of several motor behaviors, including generalized tonic extension of the extremities lasting for few seconds followed by clonic rhythmic movements and prolonged postictal confusion. On clinical evaluation, the only behavioral difference between these seizures and secondary generalized tonic-clonic seizures is that these seizures lack an aura, or there are partial seizure signs and symptoms. However, the aura preceding the partial seizure with secondary generalization is often forgotten because of postictal amnesia, and observers may not see partial seizure signs and come upon the patient in the grand mal phase.

The ictal correlate of generalized tonic-clonic seizures consists of generalized (bilateral) complexes of spikes or polyspike and slow waves. These epileptiform discharges often have increased amplitude in the frontal regions.

Atonic seizures

Atonic seizures are also called “drop attacks.” These seizures occur in people with clinically significant neurologic abnormalities and consist of brief loss of postural tone, often resulting in falls and injuries (hence, some patients need helmets). The ictal EEG correlate is similar to EEG abnormalities observed in tonic seizures.

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Classification of Epileptic Syndromes

Epileptic seizures are symptoms of neurologic dysfunction, and they are but 1 manifestation of many neurologic diseases. As with any other syndrome in medicine, an epileptic syndrome is a group of signs and symptoms that share a common pathogenesis, prognosis, and response to treatment.

In 1989, the International League Against Epilepsy (ILAE) developed a classification of epileptic syndromes, which is in the process of being revised. The current system comprises 2 major categories: localization-related syndromes and generalized-onset syndromes. Physicians would ideally classify their patients' seizures by using the classification for seizure types and make a syndromic diagnosis, if possible.

Localization-related epilepsies and syndromes include the following:

  • Idiopathic, with age-related onset
  • Benign childhood epilepsy with centrotemporal spikes
  • Childhood epilepsy with occipital paroxysms
  • Symptomatic
  • Mesial temporal lobe sclerosis

Generalized epilepsies and syndromes include the following:

  • Idiopathic, with age-related onset
  • Benign neonatal familial convulsions
  • Benign neonatal convulsions
  • Benign myoclonic epilepsy of infancy
  • Childhood absence epilepsy (pyknolepsy)
  • Juvenile absence epilepsy
  • Juvenile myoclonic epilepsy (JME)
  • Epilepsy with grand mal seizures on awakening
  • Idiopathic and/or symptomatic infantile spasms
  • Lennox-Gastaut syndrome
  • Epilepsy with myoclonic astatic seizures
  • Epilepsy with myoclonic absences
  • Symptomatic

In 2001, the ILAE Task Force on Classification and Terminology proposed that rather than revising the entire classifications of seizures (1981) or epilepsy syndromes (1989), a better strategy was to devise a 5-axis diagnostic scheme, as follows [29] :

  • Axis 1: Descriptive ictal terminology
  • Axis 2: Seizure type, from the “List of Epileptic Seizures,” with specific brain location (if known)
  • Axis 3: Syndrome, from the “List of Epilepsy Syndromes”; not always possible
  • Axis 4: Etiology, including specific genetic defects or pathologic substrates
  • Axis 5: Impairment; optional but useful parameter that can be derived from the World Health Organization (WHO) revised International Classification of Functioning, Disability and Health (ICIDH-2) impairment classification

The 2001 task force report also discussed the abandonment of the terms “partial-onset” and “localization-related” seizure and epilepsy for the term “focal.” The 2006 review of the terminology formalized the change from partial to focal, but localization-related epilepsy remains an accepted term. In addition, the task force recommended that the term “cryptogenic be replaced for the more precise wording “probably symptomatic.” However, cryptogenic remains an accepted term.

Despite the fact that for many years psychiatrists have successfully used a somewhat similar 5-axis diagnostic scheme, critics indicate that this system is unnecessarily complex and its reliability, accuracy, and clinical use are uncertain. (For a more complete description of these controversies see Wolf [30] and the resultant discussions by Engel, Luders et al, Berg and Blackstone, and Avanzini. Similarly, see Fisher et al [1] and its resultant discussion.)

To increase the controversy on this subject, there is evidence that epilepsy syndromes are not static diagnoses but ones that may evolve over time. They also have poor prognostic predictivity, and the interobserver reliability of classifying epileptic syndromes is poor. [31]

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