Epilepsy and Seizures Clinical Presentation

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 clarify the type of seizure include the following:

• Was any warning noted before the spell? If so, what kind of warning occurred?
• What did the patient do during the spell?
• Was the patient able to relate to the environment during the spell and/or does the patient have recollection of the spell?
• How did the patient feel after the spell? How long did it take for the patient to get back to baseline condition?
• How long did the spell last?
• How frequent do the spells occur?
• Are any precipitants associated with the spells?
• Has the patient shown any response to therapy for the spells?

The clinical diagnosis of seizures is based on the history obtained from the patient and, most important, the observers. Physical examination helps in the diagnosis of specific epileptic syndromes that cause abnormal findings, such as dermatologic abnormalities. For example, patients with intractable generalized tonic-clonic seizures for years are likely to have injuries requiring stitches.

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 the semiologic classification advanced by Luders and others, have been proposed.^[11] A refinement of this semiologic classification led to a 5-dimensional (5-D) patient-oriented classification of epilepsy.^[12] The ILAE commission on classification has developed additional reports.^{[13, 14]} In 2006, a new proposed classification of seizures was published.^{[13, 14]} 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 of using the changes in terminology.^[15]

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

Simple and complex focal seizures

The defining element of simple focal seizures is a seizure with preserved consciousness. Many patients with complex focal seizures have an aura warning them of their seizure. An aura 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 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 secondarily 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.

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 might 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. Automatisms frequently consist of 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. They 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 of seizures. 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.

Secondarily generalized seizures

Secondarily 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, 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 secondarily generalized seizure.

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 EEG manifestations. On occasion, classifying seizures is difficult despite videotape review of the data.

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. Facial automatisms are most common, and repetitive blinking is the most common facial automatism. Hyperventilation or photic stimulation often precipitates these seizures which typically begin during childhood or adolescence, although they may persist into adulthood.

A diagnosis of new-onset absence seizures in adulthood is incorrect in the vast majority of cases. Adults often have complex focal seizures with relatively minor automatisms. In children, absence seizures are often unrecognized until a child develops a generalized tonic-clonic seizure, and then the child is brought to medical attention. Sudden decreased performance in school or overall attention might be a subtle manifestation of frequent absence seizures.

The classic ictal electroencephalogram (EEG) correlate of absence seizures consists of 3.5-Hz generalized spike-and–slow wave complexes. Twin studies have demonstrated a significant inherited predisposition for typical childhood absence seizures. 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, they are less well formed, and they are of lesser amplitude.

Myoclonic, clonic, and tonic seizures

Myoclonic seizures consist of brief, arrhythmic, jerking, motor movements that last less than 1 second. Myoclonic seizures often cluster within a few minutes. If they 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 in the EEG consists of fast polyspike-and–slow wave complexes.

Clonic seizures consist of rhythmic, motor, jerking movements with or without impairment of consciousness. Clonic seizures can have a focal origin with or without impaired consciousness. 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 the person falls asleep, or just after he or she awakens. They 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 secondarily generalized tonic-clonic seizures is that these seizures lack an aura. However, the aura preceding the secondarily generalized seizure is often forgotten because of postictal amnesia.

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 occur in people with clinically significant neurologic abnormalities. These seizures consist of brief loss of postural tone, often resulting in falls and injuries. The ictal EEG correlate is similar to abnormalities observed in tonic seizures.

Epileptic seizures are symptoms of neurologic dysfunction and are but one manifestation of many neurologic diseases. Like 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. A task force is revising this syndromic classification. 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 Task Force on Classification and Terminology of the International League Against Epilepsy (ILAE) 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^[16] :

• 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 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 or localization-related seizure or epilepsy for the term focal. The 2006 review of 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 of probably symptomatic. However, cryptogenic remains an accepted term.

Despite the fact that psychiatrists have successfully used for many years 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 [2003]^[17] and its discussion by Engel, Luders et al, Berg and Blackstone, and Avanzini. Similarly, see Fisher et al [2005]^[1] and its 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.^[18]