Fast Facts: Epilepsy is a succinct and practical aid to the diagnosis and treatment of seizure disorders. Contents include: * The diagnostic essentials - classification of seizures, conditions that can mimic epileptic seizures, clinical evaluation of the patient and the latest brain-imaging techniques * The principles of drug selection and therapy withdrawal * An up-to-date overview of all 15 antiepileptic drugs on the market * The non-pharmacological options for patients with medically refractory epilepsy, including deep brain stimulation * Special considerations for women, elderly people, teenagers and people with learning disabilities * Psychiatric morbidities - depression, anxiety and psychosis * The effects of epilepsy on employment, driving, life insurance and lifestyle. The management of patients with epilepsy is a team effort involving medical and social service professionals and the patient's family, friends and co-workers. Primary care providers are at the forefront of care, usually performing the initial evaluation after the first seizure, making dose adjustments to the patient's drug treatment and providing ongoing support. Now in its fifth edition, this ever-popular handbook is a neatly packaged, up-to-date resource for the busy clinician and team, to help investigate, diagnose and successfully treat children and adults with a wide range of seizure disorders.
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Fast Facts: Epilepsy
By Martin J Brodie, Steven C Schachter, Patrick Kwan
Health Press LimitedCopyright © 2012 Martin J Brodie, Steven C Schachter, Patrick Kwan
All rights reserved.
Epidemiology and prognosis
Incidence and prevalence
Epilepsy is the most common serious neurological condition. It affects nearly 70 million people in the world. In high-income countries, approximately 6 per 1000 people will develop epilepsy during their lifetime, and 45 people per 100 000 will develop new-onset epilepsy each year. These figures are nearly twice as high in low- and middle-income countries, possibly as a consequence of more primitive obstetric services as well as the greater likelihood of cerebral infection and head trauma.
Incidence varies greatly with age, with high rates in early childhood, low levels in early adult life and a second peak in people aged over 65 years (Figure 1.1). In recent years, there has been a fall in the number of children affected as well as a sharp rise in epilepsy in the elderly. Indeed, old age has now become the most common time in life to develop the condition.
Most patients with epilepsy have a good prognosis. The prognosis is strongly influenced by the underlying cause. In many people – particularly children – the condition will remit, although a substantial proportion will have epilepsy all their lives. Overall, 60–70% of patients become seizure free after the start of treatment with antiepileptic drugs (AEDs). Some of these patients become and remain seizure free on the initiation of the first AED, while in others the disorder appears to follow a more fluctuating course. Some patients can remain in remission after subsequent drug withdrawal, implying that the epileptogenic causes have truly remitted. The other 30–40% of patients continue to have seizures with varying degrees of frequency and severity. It is also increasingly recognized that some patients can have a 'remitting–relapsing' course, fluctuating between periods of seizure freedom and recurrence. Factors that indicate a poor prognosis for seizure control include:
poor response to the initial AED treatment
high seizure frequency before AED treatment
generalized tonic–clonic seizures
generalized epileptiform activity on the electroencephalogram (EEG)
family history of epilepsy
comorbid psychiatric history.
The standardized mortality ratio (the ratio of observed deaths to expected deaths) for patients with epilepsy is two to three times above that of the general population. In many cases, the cause of death is related to the underlying etiology, but sudden unexpected death in epilepsy (SUDEP) is believed to account for up to 17% of all epilepsy-related deaths. SUDEP has been defined as 'sudden, unexpected, witnessed or unwitnessed, non-traumatic and non-drowning death in patients with epilepsy, with or without evidence of a seizure, and excluding documented status epilepticus, in which postmortem examination does not reveal toxicological or anatomic cause of death'. The reported incidence of SUDEP ranges from 0.35 to 10 per 1000 patients per year. It is higher if the seizure disorder remains uncontrolled, suggesting that the majority of SUDEP is related to seizure activity. Other associated causes of death include drowning, burns, aspiration, pneumonia, status epilepticus and suicide.CHAPTER 2
Classification of seizures and syndromes
A seizure is a symptom and represents the clinical manifestation of an abnormal and excessive synchronized discharge of a set of cortical neurons in the brain. Establishing the type(s) of seizure experienced by the patient has important implications for:
selection of antiepileptic drugs (AEDs)
likelihood of an underlying cerebral lesion
possible genetic transmission.
Depending on the pattern of neuronal involvement, the clinical features of a seizure consist of a wide range of sudden and transitory abnormal phenomena, which may include alterations of consciousness, or motor, sensory, autonomic or psychic events. The widely used electroclinical classification of seizures established nearly three decades ago by the International League Against Epilepsy (ILAE) is the most widely adopted scheme. This classification system, viewed by the ILAE as a work in progress, divides seizures into two major groups: partial and generalized (Table 2.1).
Partial (or focal) seizures originate in a focal region of the cortex (Figure 2.1). They can be subdivided into those that do not impair consciousness (simple partial) and those that do (complex partial), which is useful for identifying patients whose safety may be compromised by loss of consciousness from their seizures. Partial seizures can also be classified according to their clinical manifestations, such as focal motor, and can spread rapidly to other cortical areas through neuronal networks, resulting in secondary generalized tonic–clonic seizures (Figure 2.2).
Simple partial seizures. The symptoms and signs of simple partial seizures depend on the site of origin of the abnormal electrical discharge. For example, those arising from the motor cortex cause rhythmic movements of the contralateral face, arm or leg (formerly called Jacksonian seizures). Seizures arising from sensory regions or areas responsible for emotions and memory may produce olfactory, visual or auditory hallucinations, feelings of déjà vu or jamais vu, or fear, panic or euphoria.
Complex partial seizures, previously called temporal lobe or psychomotor seizures, are the most common seizure type in adults with epilepsy. There may be a warning, called an aura (simple partial seizure), immediately preceding loss or reduction of awareness. Complex partial seizures typically last less than several minutes. During that time, patients may appear awake, but lose contact with their environment; they do not respond normally to instructions or questions during this time. Patients usually stare and either remain motionless or engage in repetitive semi-purposeful behavior called automatisms, including facial grimacing, gesturing, chewing, lip smacking, snapping fingers, repeating words or phrases, walking, running or even undressing. Patients cannot remember behaving in this manner. If restrained, they may become hostile or aggressive. After the seizure, patients are often sleepy and confused, and complain of a headache. This postictal state can last from minutes to hours.
Generalized seizures are characterized by widespread involvement of bilateral cortical regions at the outset and are usually accompanied by impairment of consciousness. The familiar tonic–clonic seizure (previously called 'grand mal') often starts with a cry. The patient suddenly falls to the ground and exhibits typical convulsive movements, sometimes with tongue or mouth biting and urinary incontinence.
Other subtypes of generalized seizures include absence, myoclonic, clonic, tonic and atonic seizures (see Table 2.1).
Absence seizures (previously called 'petit mal') mainly affect children.
Typical absence seizures usually last 5–10 seconds, commonly in clusters. They manifest as sudden onset of staring and impaired consciousness, with or without eye blinking and lip smacking. The electroencephalogram (EEG) typically shows a 3-Hz spike-and-wave pattern (Figure 2.3). There is a strong genetic component for the seizures as well as for the EEG abnormality. While absences will remit during adolescence in around 40% of patients, related tonic–clonic seizures may continue into adulthood.
Atypical absence seizures usually begin before 5 years of age in conjunction with other generalized seizure types and learning disability. They last longer than typical absence seizures and are often associated with changes in muscle tone.
Myoclonic seizures consist of sudden brief muscle contractions, either singly or in clusters, that can affect any muscle group.
Clonic seizures are characterized by rhythmic or semi-rhythmic muscle contractions, typically involving the upper extremities, neck and face.
Tonic seizures cause sudden stiffening of the extensor muscles, often associated with impaired consciousness and falling to the ground.
Atonic seizures (also called drop attacks) produce sudden loss of muscle tone with instantaneous collapse, often resulting in facial or other injuries.
In addition to the classification of seizures, there is a separate system for epilepsies and epileptic syndromes (Table 2.2) that has been in place for many years. These are defined by groups of characteristic clinical features related to age at onset of seizures, family history of epilepsy, seizure type(s) and associated neurological symptoms and signs, aided by appropriate investigations, including EEG and brain imaging with, for example, CT and MRI (see Chapter 3, Diagnosis).
Diagnosing an epileptic syndrome helps the clinician define the likely prognosis, provide reasonable genetic counseling and choose the most appropriate AEDs.
Epileptic syndromes may be divided into:
localization-related or focal epilepsies (those with partial-onset seizures)
generalized epilepsies (those with generalized seizures).
Based on the knowledge of etiology, the syndromes are then further subdivided into:
idiopathic – presumed to be genetic in origin
symptomatic (secondary) – of known cause
cryptogenic – presumed to be symptomatic but with an unidentified underlying abnormality.
The accuracy of classification depends on the extent of investigation. With advances in technology, particularly in brain imaging, many subtle lesions can now be identified, making it possible to classify more of the epilepsies as symptomatic rather than cryptogenic. As with the classification of seizures, fueled by developments in diagnostic imaging and molecular genetics, the classification of epilepsy syndromes is also under revision by the ILAE.
Some of the epilepsy syndromes that may be encountered by the primary care provider are described below.
Benign rolandic epilepsy, also called benign childhood epilepsy with centrotemporal spikes, is an idiopathic focal epilepsy syndrome, with onset at 3–13 years of age. Nocturnal seizures predominate, and patients display a characteristic EEG pattern. Affected patients usually have normal cognitive function and normal findings on neurological examination. Seizures have a simple partial onset with occasional secondary generalization. Nocturnal seizures involve excessive salivation, gurgling or choking sounds, and clonic contractions of the mouth. Daytime seizures usually consist of tonic and/or clonic movements of one side of the body (particularly the face) and speech arrest, but the child remains conscious.
The EEG shows high-amplitude central and mid-temporal spikes and sharp waves, particularly during light sleep (Figure 2.4). The prognosis for children with benign rolandic epilepsy is excellent. The seizures are generally very easy to control with AEDs. The most commonly employed AEDs tend to be carbamazepine (CBZ), sodium valproate (VPA) and benzodiazepines given at bedtime. Other useful agents include oxcarbazepine (OXC) and levetiracetam (LEV). However, many children with mild or infrequent seizures do not require prophylactic AED treatment. Nearly all patients outgrow the disorder by their teenage years.
Juvenile myoclonic epilepsy (JME) is an under-recognized syndrome characterized by myoclonic jerks, tonic–clonic seizures or clonic– tonic–clonic seizures and, occasionally, absence seizures. Myoclonic seizures occur within the first few hours after arising from sleep (as do the generalized seizures), are mild and bilaterally symmetrical, and usually involve the upper extremities without impairing consciousness. The patient may spill or drop things during a myoclonic jerk. Less commonly, myoclonic seizures affecting the legs can cause falls.
JME is an inherited condition in otherwise neurologically normal children. It usually begins during the teenage years. The EEG shows a characteristic spike-and-wave pattern of 3.5–6 Hz, and multiple spike-and-wave complexes that may be precipitated by photic stimulation and sleep deprivation (Figure 2.5).
The AED of choice is VPA. Other useful drugs include lamotrigine (LTG), topiramate (TPM), zonisamide (ZNS) and LEV. Phenytoin (PHT), CBZ, OXC and gabapentin (GBP) may exacerbate the myoclonic seizures. The seizures respond well to treatment but usually recur when medication is withdrawn. Therefore, lifelong therapy is generally recommended.
Febrile convulsions develop in association with fever (usually during the rapidly rising phase) with no evidence of another defined cause. They typically present between 6 months and 5 years old. There may be a family history of epilepsy. The incidence is approximately 4%. Up to 1 in 3 affected children will have recurrent febrile seizures. Although febrile seizures are generally benign, around 5% of children with febrile convulsions later develop epilepsy, typically in adolescence or later.
Factors associated with poor prognosis include seizures that have focal features or that last longer than 15 minutes, focal neurological abnormalities and a family history of afebrile seizures. Some children will go on to develop mesial temporal sclerosis and partial seizures that are often refractory to AED therapy.
Treatment of febrile convulsions is usually symptomatic, with sponge bathing and prompt administration of an antipyretic. Some physicians advocate prophylactic rectal diazepam when fever is present in children with a history of febrile convulsions. Most pediatric neurologists would not recommend long-term AED treatment for children with simple febrile seizures (i.e. generalized seizures lasting less than 15 minutes).
Infantile spasms are sudden brief seizures that are typically tonic flexor spasms of the waist, extremities and neck. They are usually seen as part of West syndrome, which is defined as infantile spasms, hypsarrhythmic patterns on the EEG and severe encephalopathy with psychomotor retardation. Infantile spasms are associated with 20% mortality; death usually results from the underlying pathology. Of the infants who survive, more than 75% have learning disabilities and more than 50% continue to have seizures throughout life.
Etiology may be known, for example cerebral malformations (half of all patients with tuberous sclerosis develop infantile spasms), perinatal brain damage and postnatal cerebral insults, or it may be idiopathic. Spasms typically begin before 12 months of age, with peak onset at 4–6 months. Seizures may occur dozens, if not hundreds, of times daily. In addition to massive flexor spasms, abduction or adduction of the arms, self-hugging movements and extensor contractions of the neck and trunk may be seen.
The EEG is markedly abnormal in most cases and consists of diffuse high-voltage spikes and slow waves superimposed on a disorganized slow background (hypsarrhythmia).
Infantile spasms are often difficult to control. Traditionally, adrenocorticotropic hormone (ACTH), corticosteroids, VPA and nitrazepam (NTZ) have been used. More recently, vigabatrin (VGB) has demonstrated superior efficacy to steroids and is now regarded as the treatment of choice by many pediatric neurologists for infantile spasms associated with tuberous sclerosis (see Chapter 5, Antiepileptic drugs).
Lennox–Gastaut syndrome is a devastating disorder beginning in childhood, which consists of mixed types of seizures and learning disability. The EEG is characterized by slow (< 2.5 Hz) spike-and-wave patterns superimposed on an abnormal slow background.
Seizures typically occur daily, often in the tens or hundreds, and consist of axial tonic, tonic–clonic, atypical absence, myoclonic and atonic seizures, which often cause injuries. Brief tonic seizures usually occur during the night, sometimes in clusters. Atonic seizures may vary from head drops to catastrophic falls.
Cognitive deficit is usually present before the seizures develop and may be associated with behavioral problems. Most patients demonstrate abnormalities on neurological examination.
Excerpted from Fast Facts: Epilepsy by Martin J Brodie, Steven C Schachter, Patrick Kwan. Copyright © 2012 Martin J Brodie, Steven C Schachter, Patrick Kwan. Excerpted by permission of Health Press Limited.
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Table of Contents
Epidemiology and prognosis, 9,
Classification of seizures and syndromes, 12,
Pharmacological management, 38,
Antiepileptic drugs, 62,
Non-pharmacological management, 100,
Status epilepticus and seizure clusters, 112,
Specific populations, 119,
Quality of life, 130,
Future trends, 137,
Useful resources, 140,