Epilepsy

Introduction

Epileptic seizures are typically short lived and transitory but nonetheless have the potential for considerable disability because of the unpredictable nature of attacks, the risk of injury they bring, and neurologic impairment from repeated seizures and adverse effects of treatment. Driving is restricted, and there is social embarrassment, stigma, and impact on employment. Fundamental questions regarding the neurobiology of epilepsy, reasons for its development, factors that make seizures start and stop, and the variable response to treatments remain unanswered.

Epilepsy in older adults needs special consideration. An older adult with presenting symptoms that suggest a diagnosis of epilepsy can be a considerable clinical challenge. Diagnosis rests on the history of events obtained from the patient and a reliable witness. There are no clinical signs that can be elicited in a clinic, beyond directly observing a seizure, to support the diagnosis, and tests can have normal results or show nonspecific abnormalities that catch the unwary. The differential diagnosis of collapse or altered consciousness in older adults is wide. A previous diagnosis of epilepsy made earlier in life might not explain new or ongoing attacks and the term known epileptic (seen in some medical records) should be avoided.

Older people with a diagnosis of epilepsy can be considered as falling into four groups:

• 1.

  Those with new-onset seizures in late life

• 2.

  Those with an established diagnosis of epilepsy with seizures persisting or recurring in late life

• 3.

  Those with new-onset attacks in late life that have been misdiagnosed as epilepsy

• 4.

  Those with an established diagnosis of epilepsy with new or ongoing attacks that are not caused by epilepsy

Definition

An epileptic seizure is the clinical manifestation of an abnormal synchronous neuronal discharge. Epilepsy is defined as a tendency toward recurrent epileptic seizures. A diagnosis of epilepsy is not appropriate after a single event. In older adults the likelihood of further seizures can be more likely when the seizure has occurred as a result of a structural brain lesion. Traditionally the ability to predict who will develop epilepsy after a first seizure was deemed insufficient to warrant the label or treatment. In 2014 the International League Against Epilepsy (ILAE) published new proposals for the operational definition of epilepsy, which included “one unprovoked (or reflex) seizure and a probability of further seizures (at least 60%), occurring over the next 10 years.” A seizure occurring at least 1 month after a stroke was provided as an example in this new operational definition. The proposals have undergone much discussion and scrutiny within the epilepsy community. For example, what is the evidence base, and how does one calculate recurrence risk after one seizure even in the presence of intracranial pathology? The level of adoption of these new proposals remains to be seen.

Epidemiology

Epilepsy is the third most common neurologic condition in old age after dementia and stroke. The incidence is two to three times higher than that seen in childhood. A community study, the United Kingdom General Practice Survey of Epilepsy and Epileptic Seizures, found that 24% of newly diagnosed cases of definite epilepsy occurred in people aged older than 60 years. A significant rise in incidence with increasing age has been confirmed in several studies, from an overall incidence of 50 per 100,000, to 70 to 80 per 100,000 in adults older than 60 years and 160 per 100,000 in adults older than 80 years ( Figure 58-1 ). The prevalence of epilepsy is generally taken as between 5 and 10 cases per 1000 persons, with a lifetime prevalence of 2% to 5%. Rates are dependent on case ascertainment and agreement on definitions used, for example, active epilepsy (ongoing seizures) versus controlled epilepsy.

In light of these data, there would appear to be relative underprovision in specialist care for older people with epilepsy. The reasons for this are unclear, but possible explanations include a lesser perceived impact on lifestyle in older people with epilepsy compared to their younger counterparts, or less focus on the condition in older patients in light of more pressing clinical issues such as associated or unrelated comorbidities.

Classification

Epilepsy classification might be considered by generalists as overly complex. This need not be the case if the principles behind the classification schemes are better understood. The current classification of epilepsy was developed by the ILAE Commission on Classification and Terminology.

There are two parallel schemes: one for epileptic seizures and another for epilepsy syndromes. In 2010 the ILAE proposed a further revision, mostly around terminology to reflect new concepts (discussed in detail in the following sections).

Accurate syndromic classification helps direct treatment decisions and provide information on prognosis. Classification is also important for epidemiologic studies and service needs assessments. Furthermore, rigorous attempts at classification benefit the whole diagnostic process and reduce, or identify, previous epilepsy misdiagnoses. A good understanding of epilepsy syndromes that occur in childhood or early adult life remain useful when dealing with older patients because seizure risk can persist throughout life, patients may carry a diagnostic label that may not be correct, and questions regarding the continuation of long-standing medication may be raised. Several areas of confusion seem to arise in epilepsy classification in the nonspecialist setting. Typically confusion arises from the use of outdated terminology or from the failure to distinguish between terms intended to describe seizure types and those intended to designate epilepsy syndromes or some causal substrate.

Epilepsy is not a specific disease but a heterogeneous group of disorders manifesting the neuroanatomic and pathophysiologic substrate causing the seizures. A useful schema from the ILAE considers five parts, or axes, organized in a hierarchic fashion allowing the integration of available and new information. The five axes are as follows:

• Axis 1: Ictal phenomenology—describing in detail the seizure event

• Axis 2: Seizure type—localization within the brain and precipitating stimuli for reflex seizures should be specified when appropriate

• Axis 3: Syndrome—with the understanding that a syndromic diagnosis may not always be possible

• Axis 4: Cause—includes a specific disease, genetic defects or pathologic substrates causing seizures

• Axis 5: Impairment—optional but often useful additional diagnostic parameter that can be derived from an impairment classification adapted from the World Health Organization's International Classification of Impairment, Disability and Handicap (ICIDH-2)

This five-axis scheme has not been adopted widely in a formal sense. However, it remains a useful framework for clinicians who have patients with epilepsy, and it is used in some form by most epileptologists and epilepsy clinics. It can be applied in any setting, essentially considering in each case (1) the seizure type, (2) brain area or areas involved, and (3) the cause or syndrome. The precise terminology, and how it is applied, remains under debate and is likely to continue until the precise mechanisms and causes of epileptic seizures are defined to replace what are, in many cases, concepts and descriptions. The long-running debate of how best to classify epilepsy continues.

Epileptic Seizures

The International Classification of Epileptic Seizures (ICES) was developed by a panel of international experts examining video recordings of clinical and electroencephalographic seizures and linked to Axis 2 of the ILAE publication described earlier. It is based on a consensus of opinions. Box 58-1 shows the current recommended classification of epileptic seizures. By design the categories are descriptive. The first level of this system distinguishes between generalized seizures, a seizure whose initial semiology indicates, or is consistent with, “originating at some point within, and rapidly engaging, bilaterally distributed networks. Such bilateral networks can include cortical and subcortical structures, but do not necessarily include the entire cortex” ; and focal seizures, a seizure whose initial semiology indicates, or is consistent with, involvement of more localized or lateralized brain area.

Epilepsy Syndromes

The International Classification of Epilepsies and Epilepsy Syndromes (ICEES) supplements the ICES. Some epilepsy categories represent pure disease entities, whereas others represent a spectrum of clinical forms (e.g., idiopathic generalized epilepsy).

The concepts of generalized and focal are no longer recommended in the classification of syndromes. Classification is based on causative concepts: idiopathic, epilepsy occurring alone (Greek idios ) without apparent underlying pathology; symptomatic, with a known underlying cause; and cryptogenic, with an unknown but suspected underlying cause. The most recent ILAE revision proposes the following change in terminology: idiopathic is to be referred to as genetic, symptomatic as structural/metabolic, and cryptogenic as unknown. Again, the extent of adoption of all aspects of this new terminology remains to be seen.

Making the Diagnosis

Epilepsy can present with disparate symptoms. Similarly, several other conditions can present with features that may be mistaken for epileptic seizures. The key feature in epilepsy is that episodes are typically stereotyped, unchanged over a long period of time, and usually short lived. The following episodic manifestations occurring in isolation, or in combination, can be caused by epilepsy:

• Loss of awareness or consciousness

• Generalized convulsive movements

• Drop attacks

• Focal movements—jerks, posturing, semipurposeful movements, rarely thrashing, bicycling or motor agitation

• Sensory episodes—tingling, pain, burning

• Vocalization—formed speech, incomprehensible words, screams, or laughter

• Psychic experiences

• Episodic phenomena from sleep

• Prolonged confusion or fugue state

The importance of gathering a careful history before making a diagnosis of epilepsy cannot be overstated. The history should include a description of events from the patient and, crucially, a firsthand description from a witness. Overreliance on a secondhand statement such as “It looked like a fit” is likely to lead to a misdiagnosis. There is no single test to make a diagnosis of epilepsy, and time taken by an experienced clinician in taking a careful history cannot be circumvented. In each case, an account of the circumstances, time of day, situation, prodrome or warning, detailed account of the attack, the semiology and duration of the attack, rate and nature of recovery, and associated symptoms or signs (e.g., headache or confusion) are needed.

Direct questions about the attack itself and other previous attacks are helpful, but care should be taken not to lead the history; these questions are best left until the patient and witness have given a free account of the event or events in question. Useful features that are worth inquiring about directly, if not first offered, include head or eye deviation, the nature of limb movements, posturing, jerks or automatisms, and whether movements are rhythmic or synchronous and how they evolved over time. Asking a witness about repeated swallowing or lip smacking can be revealing. Any change of color, breathing pattern, and sweating need to be ascertained along with an account of the recovery period, its duration, and any subsequent symptoms such as headache, confusion, or altered behavior. It is always useful to ask about possible prior attacks that the patient may not associate with their current event; for example, a patient presenting after his or her first generalized tonic-clonic seizure may not make the link between previous experiences of focal seizures, common examples being epigastric sensations, déjà vu, or abnormal tastes or smells. Classically tongue biting and incontinence were thought to strongly indicate an epileptic seizure. This is not always the case. Urinary incontinence can occur during syncope, and injury to the tip of the tongue can occur in syncope although if the sides of the tongue or inner cheek are severely bitten, this usually indicates that a generalized tonic-clonic seizure has taken place.

The past medical history should include inquiries about previous history of head injury, intracranial infection, stroke, dementia, and cardiac history. Family history, medication history, and social history are important as in any other presentation. Specific inquiry should go into living arrangements, driving, occupation, and hobbies or pastimes.