SEIZURES AND EPILEPSY

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chapter 8

Seizures and Epilepsy

This chapter is a brief discussion of the clinical aspects of epilepsy. It does not discuss pathophysiology. The numerous classification schemes [1–4] also are not discussed as it is inevitable that with advancing knowledge these will continue to evolve.

In everyday clinical practice it is more practical to classify seizures on the basis of what happens to the patient and what can be witnessed.

The basic principles of clinical assessment and management of patients suffering from a suspected seizure or epilepsy (recurrent seizures) will be discussed. A comprehensive discussion of epilepsy can be found in numerous textbooks [5–7]. Treatment is documented in Appendix C but, as it will continue to evolve rapidly, any discussion in a textbook will quickly be out of date. Therefore, links to neurology- and epilepsy-related websites are included in Chapter 15, ‘Further reading, keeping up-to-date and retrieving information’. It is anticipated that these websites will provide the reader with the up-to-date information that a textbook cannot provide.

CLINICAL FEATURES CHARACTERISTIC OF EPILEPSY

The clinical manifestations of epilepsy are extremely variable and depend on the site of origin of the seizures within the central nervous system. There are, however, certain characteristics of all forms of epilepsy that are independent of any classification scheme.

Epilepsy (apart from the very rare reflex epilepsies discussed below) is:

• an episodic disturbance

• that may or may not be preceded by a warning (aura)

• brief in duration

• unpredictable, with

• stereotyped clinical manifestations

• positive phenomena

• impaired consciousness or awareness

• often followed by a period of post-ictal (after the event) confusion.

Epilepsy is an episodic disturbance of function that occurs with variable frequency from a single seizure in a lifetime to many seizures per day. Apart from reflex epilepsy (see ‘Reflex epilepsies’ below), when seizures will occur is unpredictable and can be any time of the day or night and under any circumstances. Some patients may experience a brief warning (aura), lasting seconds only, leading up to the ictus. Unless a patient has more than one type of seizure each episode is identical or almost identical (stereotyped), in terms of the clinical manifestations, to the previous one. If a patient suffers from multiple types of seizures each will be have their own stereotypical features. Seizures are brief, usually lasting less than 1–3 minutes (even tonic–clonic seizures) and rarely 5–10 minutes [8]. There are characteristic positive phenomena, i.e. abnormal movements or smell, taste, sensory, psychic or visual sensations. A loss of function, such as paralysis or sensory loss, is NOT a feature during a seizure but may follow a seizure; this is referred to as Todd’s palsy (see ‘Tonic–clonic seizures’ below).

If the period of ‘post-ictal’ confusion and drowsiness is prolonged, this may reflect hypoxia during the seizure, or the seizure may be part of a disease process that in itself would cause prolonged confusion such as hypoglycaemic coma or infections such as meningitis and encephalitis.

THE PRINCIPLES OF MANAGEMENT OF PATIENTS WITH A SUSPECTED SEIZURE OR EPILEPSY

1. Confirm that the patient has suffered a seizure.

2. Characterise the type(s) of seizure(s).

3. Assess the frequency of seizures.

4. Identify any precipitating causes.

5. Establish the aetiology.

6. Decide whether to treat or not.

7. Choose the appropriate drug and dose and monitor the response to therapy.

8. Advise regarding lifestyle.

9. Consider surgery in patients who fail to respond to drug therapy.

10. Decide whether and when to withdraw therapy in ‘seizure-free’ patients.

CONFIRMING THAT THE PATIENT HAS HAD A SEIZURE OR SUFFERS FROM EPILEPSY

Epilepsy is an intermittent disturbance of neurological function. Unless the seizures are frequent, it is unlikely that the clinician, routine electroencephalography or even video-electroencephalography (EEG) telemetry will witness or capture an actual event. The diagnosis, therefore, is almost entirely dependent on the neurological history. If there is an eyewitness to the episode(s) they can be questioned; otherwise the history consists of what the patient is able to recall and, since many seizures are associated with loss of consciousness, this will be limited to what happened before and what the patient can recall after the ictus.

In patients with suspected seizure(s) the best history-taking technique is to obtain a blow-by-blow description of the episode or several of the episodes. Concentrate on the periods immediately before, during and after the event or ictus. These are referred to as the pre-ictal, ictal and post-ictal periods. The correct diagnosis depends on establishing the exact duration and nature of the symptoms that occur during each of these three phases. The alternative diagnoses that may be confused with epilepsy have been discussed in Chapter 7, ‘Episodic disturbances of neurological function’.

There are several useful questions that can be asked of the patient and any eyewitnesses and these are discussed next.

In patients with suspected seizure(s) the best history-taking technique is to obtain a blow-by-blow description of the episode or several of the episodes.

Useful questions to ask the patient

• What were you doing just before the episode? The circumstances under which the episode occurred may provide a vital clue in terms of aetiology or precipitating factors: flashing lights in a discotheque with photosensitive epilepsy or a seizure during venesection suggesting a seizure probably secondary to syncope.

• Was there any warning? If so, what was the exact nature of this warning and how long did it last? A brief warning or aura lasting only seconds is very typical of epilepsy; a more prolonged warning would point to a possible alternative diagnosis.

• What was your next recollection? Can you establish how long this was after the episode commenced? A short period of lost time, 10 minutes or at most 20 minutes, is more in keeping with epilepsy.

• When you came to were you aware of anything the matter? A period of post-ictal drowsiness or confusion in the absence of a head injury strongly suggests epilepsy.

• Did you injure yourself? This is non-specific, but a dislocated shoulder occasionally occurs with tonic–clonic seizures and an injury indicates a fall, thus reducing the number of diagnostic possibilities.

• During the episode did you bite your tongue or cheek or lose control of your bladder or bowels? These occur with tonic–clonic seizures.

• Have you ever had any unexplained motor vehicle accidents? An explanation may be a seizure without warning.

• When you are watching a television program that you are interested in or having a conversation with a person, do you ever miss parts of the program or conversation? An affirmative answer to this suggests the possibility of minor absence or complex–partial seizures that the patient may not have noticed. However, when patients are just sitting in front of the television it would be not uncommon through lack of concentration to miss parts of the program. On the other hand, if it interrupts a program that the patient is particularly interested in, it is more likely to be a minor seizure.

• Do people accuse you of being a daydreamer? It is not uncommon for children and adolescents to be thought of as daydreamers when they have been having unrecognised minor seizures. It is also not uncommon for children and teenagers to actually daydream, so interpret the answer to this question with caution. If the patient has suffered from repeated episodes, establish if each and every episode was identical or whether there may have been different types of seizures so that detailed questioning of several different events is necessary.

• Have you ever been able to prevent one of these episodes and, if so, how? Seizures secondary to syncope or hypotension may be prevented if the patient assumes a recumbent posture immediately after they experience the first warning.

Useful questions to ask an eyewitness or relative

Some patients can suffer unrecognised seizures for many years [9], particularly children and teenagers who are often thought to be daydreaming. Relatives may have witnessed a number of episodes and not recognised them as seizures.A useful sequence of questions includes:

1. Have you ever seen the patient suddenly interrupt what they were doing and stare into space, where their eyes were open but they did not respond to you? If the answer is yes, this is in keeping with absence or complex–partial seizures.

2. What was the patient doing at the time the episode commenced?

3. What was the first thing that you noticed and how long did it last?

4. What was the next thing that you noticed and how long did it last?

5. What was the next thing that you noticed and how long did it last?

Keep asking this question until the whole episode has been described in detail. More specific questions include:

• During the episode was the patient able to hear what you were saying or were they out to it? If the answer is no, this indicates a loss of awareness suggesting a generalised seizure or complex–partial seizure.

• Did you see any excessive blinking or abnormal chewing movements of the mouth? These occur with absence and complex–partial seizures, respectively.

It is often useful to question more than one eyewitness or relative as one individual may not have observed all the details. When seeing a patient with suspected epilepsy or a seizure, more is to be gained by picking up the telephone and ringing a family member or an eyewitness than undertaking investigations.

As a general rule, the more complex and varied the behaviour during an episode and the longer the duration of the abnormal behaviour, the less likely one is dealing with a seizure disorder.

Epilepsy in the elderly

It is a common misconception that epilepsy is a disease of childhood. While this is largely true of absence (petit-mal) seizures, which are very rare in adults and often present when they do occur with absence status epilepsy, seizures do occur in the elderly and the incidence increases with increasing age, as shown in Figure 8.1. Elderly patients with epilepsy most often present with tonic–clonic or complex–partial seizures that have a higher recurrence rate than in the younger population. The complex–partial seizures are often difficult to diagnose since they present with atypical symptoms, particularly prolonged post-ictal symptoms including memory lapses, confusion, altered mental status and inattention [10].

FIGURE 8.1 Schematic diagram to show that both maturational factors in seizure susceptibility derived from onset of age-related epileptic disorders and febrile convulsions (a) and environmental factors derived from age-related risk of cerebral injury (b) combined to yield the incidence of epilepsy by age (c) Reproduced from ‘Seizures and Epilepsy’, by J Engel, Jr. In: Contemporary Neurology Series, edited by F Plum, Vol 31, 1989, FA Davis Company, Figure 5.3, p 115 [12]

Although there is a continuing incidence of seizures throughout life, they are more common in the first 5 years. There is also a higher incidence in the 70- to 80-year-old age group [11].

Seizures can occur in any age group and either sex.

CHARACTERISATION OF THE TYPE OF SEIZURE

The clinical manifestations of the more common types of seizures is discussed here; more detail can be found in textbooks [12–14]. The commonest seizures in clinical practice are:

• tonic–clonic

• complex–partial.

Less common are:

• simple–partial

• benign rolandic seizures.

Although the traditional approach is to classify seizures as focal versus generalised or primary (no obvious cause) versus secondary, an alternate way to characterise the various types of seizures is based on what can be witnessed:

1. seizures that cause the patient to fall with or without loss of consciousness (see Figure 8.2)

FIGURE 8.2 Seizures that cause a fall with or without loss of consciousness (LOC) ^∗A fall will result if the patient is standing and the myoclonus affects the legs. Patients with brief focal myoclonic seizures may not fall if they are seated.

2. seizures that are not associated with a fall with or without loss of consciousness (awareness; see Figure 8.3).

FIGURE 8.3 Seizures that do not cause a fall with or without loss of consciousness (LOC) ^∗Patients with myoclonic or focal–motor seizures may fall if they are standing but there is no LOC.

Tonic–clonic seizures

• Immediately before ictus: The aura or warning if it occurs may indicate a focal onset such as déjà vu, jamais vu or unpleasant olfactory (smell) or gustatory (taste) phenomena that are suggestive of a temporal lobe origin. The aura may consist of a non-specific epigastric rising sensation, where an unpleasant feeling commences in the epigastrium and rises up towards the head very quickly over a few seconds, a non-specific light-headedness or an odd feeling in the head. Tonic–clonic seizures preceded by an aura are often referred to as focal seizures with secondary generalisation, as opposed to primary generalised epilepsy where the tonic–clonic seizure is not of focal origin. The essential feature is that the aura is identical each time and more importantly is very brief, usually lasting seconds only.

• During ictus: With or without warning (an aura) the patient will fall to the ground, rigid, with the teeth clenched, arms and legs extended and eyes open. At times the arms may be flexed instead of extended. Many eyewitnesses describe the eyes as rolling up into the top of the head, which means that the eyes are open. This tonic phase is brief, usually less than 30 seconds, and it is followed by repetitive jerking (clonic phase) of the arms and legs, which is also brief, usually less than 1 or 2 minutes, although it may be prolonged up to 10 minutes. Seizures may last longer if the patient develops status recurrent seizures without recovery of consciousness between seizures, referred to as status epilepsy. During a tonic–clonic seizure the patient may bite the tongue or cheek, froth at the mouth or be incontinent of urine and/or faeces. If urinary or faecal incontinence occurs, it is during the tonic phase.

• After ictus: Immediately following the seizure the patient is limp, drowsy and confused. This period of post-ictal confusion and drowsiness varies depending upon the duration of the seizure and the age of the patient. If seizures are brief the duration may be less than a few minutes; with more prolonged seizures, the period of confusion can last much longer, usually less than half an hour. In the elderly it may last for several days in the absence of any obvious metabolic or infective process to account for such confusion. Very rarely, paralysis of a limb(s) follows a seizure, an entity called Todd’s palsy. Again, this tends to be more prolonged in the elderly.

Tonic seizures

Although these can occur at any age they are most commonly seen in childhood. When an adult has what seems like a tonic seizure it is often secondary to a hypotensive episode, e.g. vasovagal or neurocardiogenic syncope. Tonic contractions affect the face and limbs, resulting in flexion of the upper limbs and trunk and either flexion or extension of the lower limbs. Although consciousness is impaired, these seizures are very brief often lasting only seconds. It is rare for these to occur in isolation and usually patients have other types of seizures.

Atonic seizures

Atonic seizures, also referred to as drop attacks, are rare and consist of a sudden loss of postural tone: if brief only the head may drop, but if more severe the person will fall to the floor, often sustaining injury. There may be a brief period (seconds) of impaired consciousness but no post-ictal confusion. Patients usually have other seizure types, including a few brief myoclonic jerks, prior to the atonic seizure but most often tonic–clonic epilepsy.

Drop attacks due to epilepsy mainly occur in childhood; drop attacks that occur in elderly adults are thought not to be epileptic in origin and are discussed in Chapter 7, ‘Episodic disturbances of function’. The Lennox–Gastaut syndrome is seen in childhood and consists of multiple seizure types including atypical absence seizures, myoclonic, tonic–clonic and atonic seizures with often a degree of intellectual disability [5].

Myoclonic seizures

Myoclonus is a shock-like contraction of a muscle or a group of muscles. Myoclonus occurs in people without epilepsy, often when they are just falling asleep but also occasionally any time of the day. The frequency would usually be less than once a month. There is also an entity called segmental myoclonus that is not a seizure disorder, where a particular muscle or group of muscles supplied by a particular nerve or nerve root will have myoclonic jerks.

In patients with myoclonic epilepsy, these myoclonic jerks are more frequent, often occur during sleep but characteristically occur first thing in the morning on awakening. They affect the whole body or a single limb and may be single or repetitive jerks. In myoclonic seizures the patient is fully aware of what is happening. There is no aura, loss of awareness or post-ictal confusion, i.e. the patient is normal immediately before and after the event. Myoclonus induced by movement is a feature of post-hypoxic myoclonus [15].

JUVENILE MYOCLONIC EPILEPSY

Juvenile myoclonic epilepsy (JME) is myoclonus, absence seizures and occasional tonic–clonic seizures. This usually presents between ages 6 and 22, but there is a lifelong predisposition to recurrent seizures without treatment [16, 17].

Complex–partial seizures

Complex–partial seizures most commonly arise from the temporal lobe in association with mesial temporal sclerosis. Complex–partial epilepsy (CPE) was originally referred to as temporal lobe epilepsy. However, the recognition that minor seizures that impair consciousness without causing the patient to fall may arise from the occipital, frontal or parietal lobes has led to the use of the term CPE.

• Immediately before ictus: The duration of the aura is usually measured in seconds; the symptoms of aura have been described above.

• During ictus: The ictus usually lasts seconds to a few minutes. The patient is not aware of what is happening, nor are they able to respond to any verbal or painful stimuli. In the words of two relatives witnessing minor seizures: ‘the lights were on but no one was at home’ or ‘there were no sheep in the top paddock’. There may be involuntary movements of the mouth or limbs, depending on which area of the brain is the focus for the seizure.

• After ictus: There is a period of post-ictal confusion lasting several minutes during which the patient can usually respond to outside stimuli but is clearly disoriented and confused [18]. The patient is unable to relate what happened during the event.

Absence (petit-mal) seizures

Absence epilepsy generally occurs in childhood and is very rare as a primary presentation in adults. In retrospect, however, when one takes a careful history from a patient with their first tonic–clonic seizure, many patients have had unrecognised absence seizures [9] in childhood and have simply been regarded as either dull or a daydreamer.

• Immediately before ictus: The absence seizure is characterised by no warning unless it is an atypical absence.

• During ictus: The period of impaired consciousness is brief. In one study the average seizure duration was 9.4 seconds (range 1–44 seconds, SD 7 seconds), 26% of seizures were shorter than 4 seconds and 8% were longer than 20 seconds [19]. The patient simply stares into space and may blink, but they are clearly unresponsive to either verbal or painful stimuli. They have no recollection of what happened or was said to them during the episode.

• After ictus: Immediately following the ictus, the patient is able to resume a conversation and the activity that they were undertaking without any post-ictal confusion.

It is surprising how many absence seizures patients can experience without people actually noticing them because they are so brief. Absence seizures can readily be induced by hyperventilation (HV). In one study of 47 children with childhood absence seizures, HV induced seizures in 83% (39/47) of children. Of the eight children who did not have seizures induced by HV, four were too young to perform HV. In the other four children, HV was performed but may not have been performed well [19].

The important clue that helps differentiate absence seizures from daydreaming is that with absence seizures the patient will interrupt their behaviour. For example, they will momentarily pause unexpectedly during a conversation or a game they have been playing, and then appear to resume it as if nothing has happened. Many children daydream or are concentrating on television or some other activity and, although it can be difficult to attract their attention, they are not unresponsive. One common presentation of absence epilepsy is the child who has previously done well at school and who begins to fail. Unfortunately, many children in the past were assumed to be daydreamers who were not working hard enough when in fact they were missing large parts of the lesson because of minor absence seizures. In the author’s experience, many teachers fail to detect children with minor epilepsy. It is when these children who fail have further teaching that the seizures are actually discovered by the tutor who spends more time with them on a one-to-one basis.

The EEG in absence seizures shows a characteristic 3 per second spike and wave (see Figure 8.4).

FIGURE 8.4 EEG in absence epilepsy showing 3 per second spike and wave

Simple partial seizures

The essential characteristic of simple partial seizures is that they can occur at any age in either sex and consist of a brief stereotyped sensation without loss of awareness, i.e. the patient is fully conscious of what is happening and is able to describe the whole episode from start to finish. There is no warning or aura, nor is there any post-ictal drowsiness or confusion. Examples of this type of epilepsy are patients who experience a tingling sensation that may commence in their feet and rise up to the top of the head and sometimes go back down again to their feet, over a matter of seconds.

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