Types of Seizures
An epileptic seizure is classified as a single event based on clinical and electroencephalographic (EEG) information. The classification of epileptic seizures used throughout this book is the 1981 revision of the Clinical and Electroencephalographic Classification of Epileptic Seizures of the International League Against Epilepsy (henceforth, International Classification of Epileptic Seizures). In 2001, the International League Against Epilepsy proposed a new classification of epileptic seizure types. This classification has not been accepted yet and is cumbersome in its present form for general use. We have elected to continue the use of the 1981 classification in this volume.
The International Classification of Epileptic Seizures is presented in Table 2-1. Seizures are first classified into two broad categories: (a) partial seizures (seizures beginning in a relatively small location in the brain), and (b) generalized seizures (seizures that are bilaterally symmetric and without local onset). Seizures are then further classified by the exact clinical and EEG manifestations of the seizure. The clinical and EEG manifestations of the principal types of epileptic seizures recognized by the International Classification of Epileptic Seizures are presented in this chapter.
I. PARTIAL (FOCAL, LOCAL) SEIZURES
A. Simple Partial (Focal) Seizures
1. Definitions
Simple partial seizures are caused by a focal cortical discharge that results in seizure symptoms appropriate to the function of the discharging area of brain, without impairment of consciousness. Simple partial seizures may consist of motor, sensory, autonomic, or psychic symptoms and signs. The same symptoms and signs may occur in both simple partial seizures and complex partial seizures (CPSs). The crucial distinction is that impairment of consciousness occurs in the latter but not in the former. Impaired consciousness is defined as the inability to respond normally to exogenous stimuli by virtue of altered awareness or responsiveness. Responsiveness refers to the ability of the patient to carry out simple commands or willed movements, and awareness refers to the patient’s contact with and recall of events during the period in question.
2. Seizure Phenomena
Seizure manifestations are dependent on the region of the cortex in which they originate and its functions. Following the International Classification of Epileptic Seizures, the manifestations of simple partial seizures can be divided into four groups: (a) with motor signs, (b) with somatosensory or special sensory symptoms, (c) with autonomic symptoms or signs, and (d) with psychic symptoms.
Table 2-1. International classification of epileptic seizures | ||
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A. SIMPLE PARTIAL SEIZURES WITH MOTOR SIGNS.
These are among the most frequently encountered varieties of simple partial seizure. The symptoms are, at least initially, always strictly contralateral to the hemispheric focus and may represent the expression of excitatory (positive-irritative) phenomena, inhibitory (negative-suppressive or paralytic) phenomena, or a combination of the two.
The simplest form of simple partial seizure with motor signs is clonus, which consists of rhythmic alternating contraction and relaxation of muscle groups controlled by the precentral gyrus. The episodes may be self-limited (clonic focal seizure), recurrent (focal motor status epilepticus), or continuous
(epilepsia partialis continua). Spread of the discharge along contiguous areas of the precentral gyrus gives rise to the characteristic march of spreading involvement of muscle groups in jacksonian seizures. Transient paralytic phenomena (Todd paralysis) are a common postictal manifestation of an excitatory clonic seizure, especially if it is severe or repeated. With somatic inhibitory seizures, sensory loss or dysesthesia and weakness occur.
(epilepsia partialis continua). Spread of the discharge along contiguous areas of the precentral gyrus gives rise to the characteristic march of spreading involvement of muscle groups in jacksonian seizures. Transient paralytic phenomena (Todd paralysis) are a common postictal manifestation of an excitatory clonic seizure, especially if it is severe or repeated. With somatic inhibitory seizures, sensory loss or dysesthesia and weakness occur.
Versive seizures consist of conjugate eye movements and turning of the head to the same side. Parietal and temporal lobe seizures may produce homolateral or contralateral versive movements, and occipital seizures usually produce contralateral versive movements.
Postural seizures consist of asymmetric dystonic posturing of the limbs, which may be associated with vocalization or speech arrest.
Aphasic seizures consist primarily of speech arrest or inability to verbalize while consciousness is fully retained, or both. Aphemia (speech arrest), as well as vocalization (phonatory seizures), also may occur.
B. SIMPLE PARTIAL SEIZURES WITH SOMATOSENSORY OR SPECIAL SENSORY SYMPTOMS.
Somatosensory seizures are usually described as “numbness,” “tingling,” “pins and needles,” or “like a weak electric shock” and may arise from the postcentral (most often) or precentral areas. Less frequently, a sense of movement, desire to move, or inability to move is present. The initial somatosensory sensation may be the only manifestation of a seizure. The focal discharge may spread to the adjacent sensory cortex, producing a jacksonian march of sensory phenomena. The focal discharge also may spread to the adjacent motor cortex, producing motor symptoms.
Visual seizures beginning with simple visual symptoms are indicative of a focus in the occipital lobe. Visual simple partial seizures consisting of crude positive symptoms, such as flashes of lights or colors in the contralateral hemifield, are more frequently described than are negative symptoms, such as scotomas or hemianopia. Visual illusions (distortions of visual input) and hallucinations (perception of a stimulus not actually present) usually represent seizure phenomena arising from the posterior temporal area.
Auditory seizures arising near the cortex of Heschl region of the first temporal gyrus may produce simple auditory phenomena usually described as a “humming,” “buzzing,” or “hissing.” More complex auditory illusions or hallucinations result from discharges arising in the auditory association areas of the temporal lobe.
Olfactory and gustatory seizures consist of olfactory and gustatory illusions or hallucinations, usually in the form of unpleasant odors and tastes.
Vertiginous seizures may consist only of a vague feeling of dizziness or light-headedness. Vertiginous sensations without alteration of consciousness are extremely frequent expressions of vestibular irritative phenomena (peripheral or central), although they have been described also as true epileptic manifestations of
seizure foci in the middle or posterior portion of the first temporal gyrus (tornado epilepsy).
seizure foci in the middle or posterior portion of the first temporal gyrus (tornado epilepsy).
C. SIMPLE PARTIAL SEIZURES WITH AUTONOMIC SYMPTOMS OR SIGNS.
Autonomic symptoms accompanying simple partial seizures may consist of epigastric sensations, flushing or pallor, sweating, pupil dilation, diaphoresis, piloerection, nausea, vomiting, borborygmi, or incontinence.
D. SIMPLE PARTIAL SEIZURES WITH PSYCHIC SYMPTOMS.
Psychic symptoms of simple partial seizures may include dysphasia, dysmnesia, cognitive symptoms, affective symptoms, illusions, or structured hallucinations.
Dysphasic symptoms may take the form of speech arrest, vocalization, or palilalia (involuntary repetition of a syllable or phrase).
Dysmnesic symptoms, distortions of memory, may take the form of a temporal disorientation, a dreamy state, a flashback, the sensation that an experience has occurred before (déja vu, if visual; déja entendu, if auditory), or the sensation that a familiar sensation is new (jamais vu, if visual; jamais entendu, if auditory). Occasionally, a patient may experience a rapid recollection of episodes from the past (panoramic vision).
Cognitive symptoms may include dreamy states, distortions of time sense, and sensations of unreality, detachment, or depersonalization.
Affective symptoms may include fear, pleasure, displeasure, depression, rage, anger, irritability, elation, and eroticism. Some individuals may have inappropriate affective reactions to environmental stimuli, possibly because of misinterpretation of cues during the clouded consciousness of a seizure. Fear is the most frequent affective symptom and may be accompanied by objective signs of autonomic activity such as pupil dilation, pallor, flushing, piloerection, palpitation, and hypertension.
Unlike the affective symptoms of psychiatric disease, the symptoms of partial seizures occur in attacks lasting a few minutes, tend to be unprovoked by environmental stimuli, and usually abate rapidly. Less commonly, patients describe exhilaration, elation, serenity, satisfaction, and pleasure (ecstatic seizures, Dostoyevsky epilepsy). The enjoyable sensations may be similar to or different from sexual pleasure. Sexual pleasure during an aura may consist of either sexual arousal or orgasm. Violent affect and behavior during partial seizures are discussed later, in section I.B.4.c. Illusions are distorted perceptions in which objects are perceived as deformed. Polyopic illusions, such as monocular diplopia, macropsia, micropsia, and distortions of distance, may occur. Distortions of sound, including microacusia and macroacusia, may be experienced. Depersonalization, a feeling that the person is outside the body, may occur. The patient may experience altered perception of the size or weight of a limb.
Structural hallucinations are perceptions without corresponding external stimuli and may affect somatosensory, visual, auditory, olfactory, or gustatory senses. Seizures arising from primary receptive areas tend to give rather primitive hallucinations, whereas seizures arising from association areas tend to give more elaborate symptoms.
E. COMPLEX PARTIAL SEIZURES WITH SIMPLE PARTIAL ONSET.
If a simple partial seizure arising in a circumscribed portion of one lobe spreads to involve larger portions of the brain, and if consciousness becomes impaired, the seizure is classified as a CPS with simple partial onset.
F. SIMPLE PARTIAL SEIZURES EVOLVING TO SECONDARILY GENERALIZED SEIZURES.
Simple partial onset seizures may spread further and become secondarily generalized (tonic-clonic, tonic, or clonic).
3. Electroencephalographic Phenomena
A. INTERICTAL ELECTROENCEPHALOGRAM.
Abnormal interictal EEGs are found in as many as 80% to 90% of patients with simple partial seizures when multiple EEGs (including long-term monitoring) are performed and all types of abnormalities are considered. Only 50% or fewer of individual routine interictal EEGs show an abnormality. Focal spike or sharp discharges, slowing, or suppression of normal background are the usual abnormalities. Focal EEG findings are absent in many patients for several reasons: (a) spikes are an intermittent phenomenon, (b) spikes or slow waves originating from small areas of cortex may be markedly attenuated at the scalp, and (c) spikes or slow waves may originate from cortical areas distant from the convexity and be unrecorded at the scalp. Additional routine recordings, sleep deprivation, and long-term EEG recording increase the yield of abnormal EEG findings in a patient with a normal initial EEG.
B. ICTAL ELECTROENCEPHALOGRAM.
At the time of onset of clinical seizures, a majority of patients with focal seizures show a transformation in the scalp EEG from an interictal pattern to a sustained rhythmic pattern. The initial frequency of rhythmic ictal transformation (RIT) is most often in the range of 13 to 30 Hz but may be slower. The RIT shows a progressive increase in amplitude and a decrease in frequency as clinical seizures develop. Spread to adjacent areas of the brain is indicated by the development of RIT in those areas. Termination of rhythmic ictal activity may be associated with the gradual development of slow-wave and spike-slow-wave activity that gradually decreases in frequency and then gives way to postictal slowing, depression of voltage, or both. Rhythmic ictal activity can also subside abruptly. In the minority of cases that show no RIT, the interictal pattern of mixed sharp and slow activity (or normal background) persists without observable change during the clinical seizure.
5. Differential Diagnosis
Simple partial seizures in adults must be differentiated from migraine, syncope, transient ischemic attacks, Ménière disease, and psychogenic seizures. In children, tics, chorea, and tremor sometimes cause diagnostic confusion. The differential diagnosis for epileptic seizures is discussed in Chapter 9.
6. Epilepsy Syndromes
The epilepsy syndromes are listed in Chapter 1, Table 1-2. Partial seizures usually occur as part of the following groups of syndromes: symptomatic and probably symptomatic focal epilepsies (see Chapter 3), idiopathic focal epilepsies of infancy and childhood (see Chapters 4, 5, and 6), familial (autosomal dominant) focal epilepsies (see Chapters 3, 4, and 5).
7. Etiology, Management, and Prognosis
Etiology, management, and prognosis are reviewed in Chapter 3.
B. Complex Partial Seizures (Psychomotor or Temporal Lobe Seizures)
1. Definitions
The central feature of CPSs is impairment of consciousness, which is defined as the inability to respond normally to exogenous stimuli by virtue of altered awareness or responsiveness. Responsiveness refers to the ability of the patient to carry out simple commands or willed movement, and awareness refers to the patient’s contact with events during the period in question and its recall.
The period of impairment of consciousness may or may not be preceded by symptoms or signs of a simple partial seizure. No other manifestations may appear during the period of impaired consciousness, or automatisms (i.e., nonreflex actions performed “automatically,” without conscious volition, and for which the patient has no recollection) may be present.
2. Seizure Phenomena
A. CLASSIFICATION.
The International Classification of Epileptic Seizures divides CPSs into four groups (Table 2-1): (a) CPSs with simple partial onset followed by impairment of consciousness only, (b) CPSs with simple partial onset followed by impaired consciousness and automatisms, (c) CPSs with impairment of consciousness at onset with impairment of consciousness only, and (d) CPSs with impairment of consciousness at onset with automatisms. Three major areas describe seizure phenomena during CPSs: (a) impairment of consciousness, (b) types of simple partial onset, and (c) automatisms.
B. IMPAIRMENT OF CONSCIOUSNESS.
During the period of impaired consciousness, a patient may look vacant or frightened. Although sometimes able to recount vague sensations, these patients do not realize that anything more has occurred.
C. TYPES OF SIMPLE PARTIAL ONSET.
Simple partial onset with motor signs, with somatosensory or special sensory symptoms, with autonomic symptoms or signs, and with psychic symptoms are discussed earlier, in sections I.A.2.a-d. Psychic symptoms can occur without impairment of consciousness as part of a simple partial seizure. More commonly, psychic symptoms occur in association with impaired consciousness as part of a CPS. The frequent association of psychic symptoms and motor automatisms with CPSs is responsible for the formerly used term psychomotor seizure.
D. AUTOMATISMS.
An automatism is a more- or less-coordinated, involuntary motor activity occurring during the state of clouding of consciousness, either in the course of or after an epileptic seizure, usually followed by amnesia of the event. The automatism may be simply a continuation of an activity that was going on when the seizure occurred, or it may be a new activity developed in association with the ictal impairment of consciousness. Usually, the activity is commonplace, often provoked by the subject’s environment or by sensations during the seizure; fragmentary, primitive, infantile, or antisocial behavior is occasionally seen. Automatisms can be detected in more than 90% of CPSs recorded on videotape.
Five types of phenomena may occur during an automatism: alimentary, mimetic, gestural, ambulatory, and verbal. Alimentary phenomena include automatic chewing movements, increased salivation, and borborygmus. Mimetic phenomena include movements of the face resulting in expressions of fear, bewilderment, discomfort, or vacant tranquility; laughing (gelastic seizures); and crying (lacrimonic seizures). Gestural phenomena include repetitive movements of the hands and fingers and sexual gestures. Ambulatory phenomena include wandering or running (cursive seizures), and the patient may unknowingly run out into traffic or into obstacles. Verbal phenomena include short phrases, expletives, or swearing, commonly repeated in an automatic fashion. The spontaneously vocalized words may reflect a previous experience.
E. DROP ATTACKS.
Sudden loss of consciousness, accompanied by loss of postural tone and falls, may occur during a CPS. Such patients usually have had seizures for several years before the falls begin, suggesting an increasing rate of spread over time.
F. COMPOUND FORMS OF COMPLEX PARTIAL SEIZURES.
Most CPSs exhibit a combination of the symptoms listed earlier. Delgado-Escueta et al. (2) found that most CPSs were compound forms of two types.
During the early phase of a type I attack, the patient was essentially motionless and initially unresponsive to superficial and deep pain. After approximately 10 seconds, a second phase of 10- to 60-second duration was observed. During this time, the patient remained unresponsive and showed automatisms such as repeated chewing, blinking, and swallowing. During the third and longest phase of a type I seizure (0.5 to 12.0 minutes), impairment of consciousness of a less profound nature was observed. Automatisms could be interrupted, and the patient sometimes reacted to environmental cues. This phase is best described as a cloudy state.
Type II attacks consisted of reactive automatisms during impaired consciousness. A motionless, staring state was not observed, although stereotyped movements occurred. Automatisms occurring during the cloudy states of type II attacks and during the third phase of type I attacks were considered reactive, because the behavior appeared purposeful. Amnesia for the entire attack ensued. Motor responses were coordinated and were sufficient to carry out the patient’s intended actions; appropriate and inappropriate responses were both seen.
G. COMPLEX PARTIAL SEIZURES EVOLVING TO GENERALIZED SEIZURES.
The seizure discharges of a CPS may become secondarily generalized, producing a generalized seizure (tonic-clonic, tonic, or clonic; see section I.C, later).
3. Electroencephalographic Phenomena
A. INTERICTAL.
Interictal manifestations of CPSs include focal spikes, sharp waves, and slowing. These abnormalities most often are found in the anterior temporal region, but many occur in other areas. Abnormalities may be localized or bilateral (synchronous or asynchronous). Discharges arising from the mesial surface of the frontal lobe may appear as generalized discharges on surface EEG.
B. ICTAL ELECTROENCEPHALOGRAM.
During a clinical CPS, any of the following can be recorded from scalp EEG electrodes: (a) sustained rhythm of spikes or sharp waves and rhythmic slowing, (b) attenuation of amplitude (suppression), (c) rhythmic slow waves; (d) 10- to 30-Hz fast activity, (e) spike-wave complexes, (f) other changes or variants of these five, or (g) no change (10% to 30% of patients). These patterns may be focal, lateralized, bilateral, or diffuse.
C. POSTICTAL ELECTROENCEPHALOGRAM.
The postictal EEG usually consists of generalized or localized slow activity. Localized postictal slowing provides information about lateralization or localization of the site of origin of the CPS in approximately 40% of recordings.
D. SPECIAL ELECTROENCEPHALOGRAPHIC TECHNIQUES.
Approximately 50% of routine EEGs performed on patients with CPSs are abnormal. This yield can be increased to 90% by using repeated studies, sleep deprivation (allowing 4 hours or less sleep the night before study), additional temporal electrodes (usually T1 and T2; alternatively, sphenoidal electrodes), and long-term EEG monitoring. When CPSs are suspected clinically and a routine EEG is normal, a sleep-deprived EEG with temporal leads should be ordered. If this is normal, long-term EEG monitoring should be considered.
4. Neurobehavioral Aspects of Complex Partial Seizures
Patients with CPSs often have (a) damage to limbic structures (with resulting cognitive and behavioral problems), (b) seizures involving limbic structures, and (c) psychosocial difficulties caused by (a) and (b). Thus, a number of complex neurobehavioral issues are associated with CPSs.
A. EMOTIONAL ACTIVATION OF COMPLEX PARTIAL SEIZURES.
Patients with CPSs are vulnerable to emotional activation of seizure activity because the anatomic structures involved during CPSs are those that subserve normal emotional responses. Conversely, reducing emotional stress (which may happen during hospitalization) may decrease the occurrence of CPSs.
B. INTERICTAL PERSONALITY.
Several authors have described “an interictal personality” of patients with CPSs, characterized by such features as “stickiness,” humorlessness, dependence,
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