**The Classification of Seizures and Epilepsy Syndromes**

Leslie A. Rudzinski1 and Jerry J. Shih2 *1Emory University School of Medicine, 2Mayo Clinic Florida U.S.A.* 

#### **1. Introduction**

68 Novel Aspects on Epilepsy

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Understanding the classification of epileptic seizures is the first step towards the correct diagnosis, treatment and prognostication of the condition. The initial management of a patient with seizures begins with an understanding of the patient's seizure type and, if pertinent, epilepsy syndrome. Specific seizure types or syndromes often respond better to specific medications or surgical approaches. Some seizure types or syndromes carry a benign prognosis or high likelihood of seizure remission by a certain age. Other seizure syndromes may carry a far poorer prognosis, and early knowledge of this allows focused treatment and lifestyle modifications for patients and families.

The classification of epileptic seizures is still largely based on clinical observation and expert opinions. The International League Against Epilepsy (ILAE) first published a classification system in 1960. The last official update for seizures was published in 1981, and the last official update for the epilepsies was in 1989. By definition, epilepsy is diagnosed after a patient has two or more unprovoked seizures. The 1981 and 1989 updates form the officially accepted classification system, although there continues to be efforts to develop a clinically meaningful revision to the current system. A report in 2010 by the ILAE Commission on Classification and Terminology recommended that changes be made in the current conceptualization, terminology, and definitions of seizures and epilepsy. This chapter will focus primarily on the currently accepted standard based on the 1981 and 1989 reports, and discuss the recommendations of the 2010 ILAE report.

#### **2. The classification of epileptic seizures**

#### **2.1 Partial seizures**

Partial or focal seizures comprise one of the two main classes of epileptic seizures, with generalized seizures being the other. Partial seizures are subdivided between simple and complex partial seizures, which are distinguished by the presence or absence of impairment of consciousness. Simple partial seizures are defined as seizures without impairment of consciousness while complex partial seizures are defined as seizures with impairment of consciousness. Consciousness is defined as the "degree of awareness and/or responsiveness of the patient to externally applied stimuli". Responsiveness refers to the ability of the patient to respond to external stimuli, and awareness refers to the recall of events occurring

The Classification of Seizures and Epilepsy Syndromes 71

1994). Finally, sensory seizures can also originate from the insular cortex. The symptoms often involve the naso-oropharyngeal-laryngeal regions and consist of throat paresthesias, warmth,

Simple partial seizures with special sensory symptoms include visual, auditory, gustatory, olfactory, and vertiginous symptoms. Visual seizures can originate from primary visual cortex and consist of primary visual hallucinations such as flashing lights, spots, stars, or circles of colored light which can appear in the contralateral visual field or directly ahead. More complex visual hallucinations originate from visual association cortex and can include seeing persons or scenes. One patient described seeing Fred Flintstone and The Gingerbread Man at the onset of seizures. Post-ictal darkness or blindness can follow simple visual seizures. Auditory seizures which arise from the lateral temporal region, specifically the superior temporal gyrus and Heschl's gyrus, can include the clinical symptoms of buzzing, ringing, hearing a rushing sound, hyper- or hypoacusis, sound distortion, or hearing words or music. Olfactory seizures originating from the uncinate gyrus or mesial temporal region typically involve smelling unpleasant odors such as burning rubber, smoke, or sulfur. Gustatory sensations originating from the temporal lobe, insula, or parietal operculum can be pleasant or unpleasant and usually are described as a metallic taste but can also be bitter or sweet. On rare occasions, vertiginous symptoms may also be a type of simple partial

Simple partial seizures with psychic symptoms indicate a disturbance of higher cortical function. For example, dysphasic symptoms include expressive or receptive language disturbances and may involve repetition of a word or phrase (epileptic palilalia). Dysmnesic symptoms involve a distortion of memory and include déjà vu, jamais-vu, déjà-entendu, jamais- entendu, autoscopy, or panoramic vision (see Table 1). Other cognitive disturbances such as dreamy states, distorted time sense, derealization, or a sense of unreality may be present. Emotional symptoms include pleasure, fear, or anger which occurs in paroxysms lasting seconds to minutes. Illusions may be present which result in distorted perceptions of the person him or herself or objects around him or her. Structured hallucinations can take the form of music or scenes and may affect multiple sensory modalities (somatosensory, visual, olfactory, or gustatory). Primitive hallucinations originate from the corresponding primary sensory area whereas more complex and elaborate hallucinations originate from the corresponding association cortices. Psychic auras often originate from the temporal lobe.

Jamais vu When what should be a familiar visual experience becomes unfamiliar

Jamais entendu When what should be a familiar auditory experience becomes

Autoscopy Seeing oneself in external space, as if the mind has left the body

Derealization A feeling of unreality of the outside world; the world seems strange and

Depersonalization A feeling of unreality in one's sense of self; feeling as if in a dream or

tightening, or a sense of strangulation or suffocation (Nguyen et al., 2009).

seizure which originates from the lateral temporal region.

Déjà vu An illusion of a familiar memory

unfamiliar

unreal

Déjà entendu An auditory illusion of something familiar

watching oneself act Macro-/Micropsia Objects appear larger or smaller than usual Macr-/Micracusia Sounds are louder or softer than usual

**Psychic Aura Definition** 

Table 1. Psychic Auras

during the ictal period. These two features of consciousness are usually tested during and after a seizure in an epilepsy monitoring unit. A patient may be able to follow commands during a seizure, but may not be able to recall portions of the event afterwards, which indicates intact responsiveness but impaired awareness.

Partial seizures manifest themselves in many different forms, depending on which area of the cortex is involved in the onset and spread of the ictal discharge. Partial seizures originate from a focal area of cerebral cortex and may spread to other cortical regions either unilaterally or bilaterally. A partial seizure may manifest with motor signs, autonomic symptoms, somatosensory or special sensory symptoms, or psychic symptoms. The term aura comes from the Latin word "breeze" and is synonymous with a simple partial sensory or psychic seizure. An aura often reflects the location of the seizure onset zone, although there are exceptions.

## **2.1.1 Simple partial seizures**

Focal motor seizures can originate in the precentral gyrus or spread to the precentral gyrus from neighboring cortical regions. They can remain focal, causing right hand clonic activity for example, or can spread or "march" along the motor strip involving different areas of the motor homunculus. This type of seizure is known as a "Jacksonian seizure" and often clinically manifests as clonic activity originating in the hand and then marching up the ipsilateral arm, shoulder, face, and leg. After a focal motor seizure, post-ictal weakness (Todd's paralysis) can last for minutes to hours. The mechanism of Todd's paralysis is thought to be either from "neuronal exhaustion due to the increased metabolic activity of the discharging focus" or from "increased inhibition in the region of the focus." Epilepsia Partialis Continua (EPC) is defined as a continuous focal motor seizure which remains confined to a specific body part and usually consists of clonic movements which can persist for up to months with preserved consciousness (1981). EPC can be seen in Rasmussen Syndrome, focal lesions (cortical dysplasia, vascular lesions, or tumors), nonketotic hyperglycemia, and some inborn errors of metabolism (MERRF) (Engel, 2006).

In a series of 14 patients with focal motor seizures who underwent epilepsy surgery at Mayo Clinic, 11 patients were seizure-free post operatively (Sandok & Cascino, 1998). Other types of focal motor seizures originating from the language area include those with a motor speech arrest or vocalization. Versive seizures originating from the dorsolateral frontal cortex (frontal eye fields) involve contralateral head, eye, or trunk deviation. Tonic seizures originating from the SMA (supplementary motor area) involve abrupt bilateral or asymmetric posturing usually of the contralateral arm, where sometimes the contralateral arm is abducted, externally rotated, and elevated and the head is also deviated contralaterally. This has been termed the "fencing posture" or M2e sign. Consciousness is usually preserved.

Simple partial seizures can also have autonomic symptoms such as vomiting, sweating, piloerection, pupil dilation, pallor, flushing, borborygmi, and incontinence. Simple partial seizures with somatosensory symptoms originating from the post central gyrus may include feelings of focal paresthesias ("pins and needles"), numbness, warmth, or electrical shock-like sensations which can also spread like Jacksonian seizures (a sensory Jacksonian march). Simple partial seizures with somatosensory symptoms can also originate from the secondary sensory area which lies above the Sylvian fissure anterior to the precentral gyrus. Secondary sensory seizures are characterized by more widespread involvement of the sensation (contralateral, ipsilateral, and bilateral involvement) and may include symptoms of feeling cold, pain, or the desire to move (Penfield W et. al., 1950). Sensory seizures can also originate from the supplementary sensory area, which is just posterior to the supplementary motor area, and involve tingling, the desire for movement, feeling stiff, pulling, pulsing, and heaviness (Lim et al.,

during the ictal period. These two features of consciousness are usually tested during and after a seizure in an epilepsy monitoring unit. A patient may be able to follow commands during a seizure, but may not be able to recall portions of the event afterwards, which

Partial seizures manifest themselves in many different forms, depending on which area of the cortex is involved in the onset and spread of the ictal discharge. Partial seizures originate from a focal area of cerebral cortex and may spread to other cortical regions either unilaterally or bilaterally. A partial seizure may manifest with motor signs, autonomic symptoms, somatosensory or special sensory symptoms, or psychic symptoms. The term aura comes from the Latin word "breeze" and is synonymous with a simple partial sensory or psychic seizure. An

Focal motor seizures can originate in the precentral gyrus or spread to the precentral gyrus from neighboring cortical regions. They can remain focal, causing right hand clonic activity for example, or can spread or "march" along the motor strip involving different areas of the motor homunculus. This type of seizure is known as a "Jacksonian seizure" and often clinically manifests as clonic activity originating in the hand and then marching up the ipsilateral arm, shoulder, face, and leg. After a focal motor seizure, post-ictal weakness (Todd's paralysis) can last for minutes to hours. The mechanism of Todd's paralysis is thought to be either from "neuronal exhaustion due to the increased metabolic activity of the discharging focus" or from "increased inhibition in the region of the focus." Epilepsia Partialis Continua (EPC) is defined as a continuous focal motor seizure which remains confined to a specific body part and usually consists of clonic movements which can persist for up to months with preserved consciousness (1981). EPC can be seen in Rasmussen Syndrome, focal lesions (cortical dysplasia, vascular lesions, or tumors), nonketotic

aura often reflects the location of the seizure onset zone, although there are exceptions.

hyperglycemia, and some inborn errors of metabolism (MERRF) (Engel, 2006).

"fencing posture" or M2e sign. Consciousness is usually preserved.

In a series of 14 patients with focal motor seizures who underwent epilepsy surgery at Mayo Clinic, 11 patients were seizure-free post operatively (Sandok & Cascino, 1998). Other types of focal motor seizures originating from the language area include those with a motor speech arrest or vocalization. Versive seizures originating from the dorsolateral frontal cortex (frontal eye fields) involve contralateral head, eye, or trunk deviation. Tonic seizures originating from the SMA (supplementary motor area) involve abrupt bilateral or asymmetric posturing usually of the contralateral arm, where sometimes the contralateral arm is abducted, externally rotated, and elevated and the head is also deviated contralaterally. This has been termed the

Simple partial seizures can also have autonomic symptoms such as vomiting, sweating, piloerection, pupil dilation, pallor, flushing, borborygmi, and incontinence. Simple partial seizures with somatosensory symptoms originating from the post central gyrus may include feelings of focal paresthesias ("pins and needles"), numbness, warmth, or electrical shock-like sensations which can also spread like Jacksonian seizures (a sensory Jacksonian march). Simple partial seizures with somatosensory symptoms can also originate from the secondary sensory area which lies above the Sylvian fissure anterior to the precentral gyrus. Secondary sensory seizures are characterized by more widespread involvement of the sensation (contralateral, ipsilateral, and bilateral involvement) and may include symptoms of feeling cold, pain, or the desire to move (Penfield W et. al., 1950). Sensory seizures can also originate from the supplementary sensory area, which is just posterior to the supplementary motor area, and involve tingling, the desire for movement, feeling stiff, pulling, pulsing, and heaviness (Lim et al.,

indicates intact responsiveness but impaired awareness.

**2.1.1 Simple partial seizures** 

1994). Finally, sensory seizures can also originate from the insular cortex. The symptoms often involve the naso-oropharyngeal-laryngeal regions and consist of throat paresthesias, warmth, tightening, or a sense of strangulation or suffocation (Nguyen et al., 2009).

Simple partial seizures with special sensory symptoms include visual, auditory, gustatory, olfactory, and vertiginous symptoms. Visual seizures can originate from primary visual cortex and consist of primary visual hallucinations such as flashing lights, spots, stars, or circles of colored light which can appear in the contralateral visual field or directly ahead. More complex visual hallucinations originate from visual association cortex and can include seeing persons or scenes. One patient described seeing Fred Flintstone and The Gingerbread Man at the onset of seizures. Post-ictal darkness or blindness can follow simple visual seizures. Auditory seizures which arise from the lateral temporal region, specifically the superior temporal gyrus and Heschl's gyrus, can include the clinical symptoms of buzzing, ringing, hearing a rushing sound, hyper- or hypoacusis, sound distortion, or hearing words or music. Olfactory seizures originating from the uncinate gyrus or mesial temporal region typically involve smelling unpleasant odors such as burning rubber, smoke, or sulfur. Gustatory sensations originating from the temporal lobe, insula, or parietal operculum can be pleasant or unpleasant and usually are described as a metallic taste but can also be bitter or sweet. On rare occasions, vertiginous symptoms may also be a type of simple partial seizure which originates from the lateral temporal region.

Simple partial seizures with psychic symptoms indicate a disturbance of higher cortical function. For example, dysphasic symptoms include expressive or receptive language disturbances and may involve repetition of a word or phrase (epileptic palilalia). Dysmnesic symptoms involve a distortion of memory and include déjà vu, jamais-vu, déjà-entendu, jamais- entendu, autoscopy, or panoramic vision (see Table 1). Other cognitive disturbances such as dreamy states, distorted time sense, derealization, or a sense of unreality may be present. Emotional symptoms include pleasure, fear, or anger which occurs in paroxysms lasting seconds to minutes. Illusions may be present which result in distorted perceptions of the person him or herself or objects around him or her. Structured hallucinations can take the form of music or scenes and may affect multiple sensory modalities (somatosensory, visual, olfactory, or gustatory). Primitive hallucinations originate from the corresponding primary sensory area whereas more complex and elaborate hallucinations originate from the corresponding association cortices. Psychic auras often originate from the temporal lobe.


Table 1. Psychic Auras

The Classification of Seizures and Epilepsy Syndromes 73

may briefly flex and then extend and adduct with the toes pointed. Clonic activity then ensues which is initially rapid and then slows. Gasping respirations occur as the respiratory muscles are involved in the clonic activity. The patient may become cyanotic. Urinary incontinence may occur. At the end of the seizure, the patient is unconscious for a brief period of time and then gradually recovers. Patients typically report generalized muscle

Tonic-clonic seizures may occur independently, may arise from other generalized seizures, or may occur during secondary generalization of a partial onset seizure. The semiologic features of tonic-clonic seizures in primary generalized epilepsy may be bilaterally symmetric or may involve a forced head deviation to either side (Ochs et al., 1984). During secondarily generalized partial onset seizures, patients often assume a figure-4 posture where the contralateral arm extends, and the ipsilateral arm flexes at the elbow. This posture can occur with the legs as well. Tonic-clonic seizures may lead to injuries such as burns, head injuries, vertebral compression fractures, shoulder dislocations, and tongue and

*Myoclonic seizures* are generalized seizures characterized by brief, irregular, shock-like jerks of the head, trunk, or limbs. They can be symmetric or asymmetric and involve the whole body, regions of the body, or focal areas. They tend to occur close to sleep onset and upon awakening from sleep. Myoclonic seizures can be a feature of some idiopathic generalized epilepsies (Juvenile Myoclonic Epilepsy), symptomatic generalized epilepsies (Myoclonic-Astatic Epilepsy), the progressive myoclonic epilepsies (Lafora Disease), and infantile spasms. Myoclonus can be positive or negative. Negative myoclonus refers to the brief loss of postural tone when the body part is held against gravity. Consciousness is not impaired and there is no post-ictal confusion with single myoclonic jerks. Myoclonic seizures can occur in clusters and evolve into clonic-tonic-clonic seizures, with resultant loss of consciousness and postictal confusion. The ictal EEG pattern is characterized by brief generalized polyspike or polyspike and wave discharges which corresponds to the

*Tonic seizures* are seizures which involve tonic contraction of the face, neck, axial, or appendicular musculature lasting from 10 seconds to one minute. They can involve extension or flexion of the muscles and often lead to falls and head injuries. They may be more subtle and involve only upward eye deviation. They often occur out of NREM sleep. They are usually seen in patients with symptomatic generalized epilepsy and are one of the common seizure types in patients with Lennox-Gastaut syndrome. They can also occur in epilepsy with myoclonic-astatic seizures. The ictal EEG usually shows a brief generalized attenuation of cerebral activity followed by generalized paroxysmal fast activity in the beta

*Clonic seizures* are generalized seizures that are characterized by repetitive rhythmic clonic jerks (1-2 Hz) with impairment of consciousness and a short post-ictal phase. They can lead into a clonic-tonic-clonic seizure. It is thought that the repetitive discharges are due to rhythmic excitatory discharges from the cortex (1981; Engel, 2006). The ictal EEG demonstrates generalized polyspike and wave discharges or generalized fast activity. *Atonic seizures* are characterized by a sudden loss of muscle tone which can lead to a head drop, a limb drop, or a drop of the whole body (a.k.a. – a drop attack). There is a brief loss of consciousness and injuries, particularly to the face, may occur (1981). Atonic seizures last less than 5 seconds, and there is minimal post-ictal confusion. Atonic seizures may be preceded by

soreness and sometimes a headache post-ictally.

cheek lacerations.

myoclonic jerk.

frequency range.

#### **2.1.2 Complex partial seizures**

Complex partial seizures are partial seizures with impairment of consciousness. They may start as simple partial seizures (auras) and progress to complex partial seizures or may begin as complex partial seizures with impairment of consciousness at the onset of the seizure. They may or may not involve automatisms. The clinical features of the complex partial seizure depend on the region affected by abnormal electrical activity. Complex partial seizures usually originate in the frontal or temporal lobes but can occur in the parietal or occipital lobes.
