9.1   Fundamentals

9.2   Generalized Seizures

9.3   Focal (Partial) Seizures

9.4   Status Epilepticus

9.5   Episodic Neurologic Disturbances of Nonepileptic Origin

9.1 Fundamentals

In their differential diagnosis, epileptic seizures must be carefully distinguished from other episodic events involving neurologic deficits and disturbances of consciousness.

Epidemiology One percent of all persons have epileptic seizures. The child of a parent with genetic epilepsy has a 4% likelihood of suffering from it.

Pathophysiology Epileptic seizures are due to the uncoordinated activity of neurons in the brain, which expresses itself electrophysiologically as an abnormality of the fluctuations of electrical potential that are seen in an EEG (see section ▶ 4.3.2). (If the surface EEG is normal, such abnormalities can be revealed by recording with depth electrodes.) The underlying cause is an imbalance of excitatory and inhibitory currents, with predominance of excitatory neurotransmitters such as glutamate and aspartate, or diminished activity of inhibitory neurotransmitters such as gamma-aminobutyric acid. Altered network structures are responsible: these promote the generation and intermittent spread of uncoordinated neural activity. The uncoordinated discharge of neurons in a particular area of the brain is accompanied by a local increase in blood flow.

Etiology In structural epilepsy, epileptic seizures are produced by structural lesions in the brain (so-called epileptogenic structural changes: scar, tumor, congenital malformation). Metabolic epilepsy is due to metabolic disturbances (e.g., hypoglycemia) or toxic influences (e.g., alcohol). These are both types of symptomatic epilepsy. In contrast, the genetic epilepsies involve a genetic predisposition to epileptic seizures, in the absence of a structural lesion. The epilepsies of unknown cause are presumed to be of symptomatic origin, although their cause cannot (yet) be demonstrated. Molecular genetic techniques have made it possible to trace certain forms of focal epilepsy back to specific mutations in the genome.

This threefold classification, like all classifications, has its limits. There will always be cases whose classification is ambiguous or uncertain; for example, there are some genetically based structural changes of the brain that are epileptogenic. Moreover, there is often more than one etiologic factor at work. Thus, diseases of the brain are more likely to produce epileptic seizures in persons with an inherited predisposition to seizures than in other, normal individuals.

Clinical features General characteristics of epileptic seizures are as follows:

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  Epileptic seizures are events of sudden onset.

  
  
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  They occur with variable frequency (generally in the range of a few seizures per year to several per day).

  
  
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  Stereotypy: epileptic seizures generally take a similar course each time they occur, with an identical, “predetermined” sequence of manifestations, and are of similar duration each time as well.

  
  
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  They often present with motor phenomena (in particular, repetitive, clonic twitching or changes of muscle tone) and sometimes with somatosensory, special sensory, and/or autonomic manifestations.

  
  
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  Depending on their type, they may involve an impairment or loss of consciousness, or consciousness may be preserved during the seizure.

  
  
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  The seizure may be preceded by premonitory symptoms of various kinds (auras, e.g., nausea, a rising sensation of warmth, or a feeling of unreality).

  
  
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  In some patients, seizures occur in response to specific provocative and precipitating factors (sleep deprivation, alcohol withdrawal, medications, strobe lighting, hyperventilation, fever).

9.1.1 Classification of the Epilepsies

Epilepsy can be classified according to several criteria ( ▶ Table 9.1 and ▶ Table 9.2), including:

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  Etiology, for example:

  
  
  
  
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    “Genuine/idiopathic” = genetic.

    
    
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    Symptomatic = structural or metabolic.

    
    
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    Cryptogenic = of unknown cause.

  
  
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  Age of onset, for example:

  
  
  
  
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    Epilepsy of childhood or adolescence.

    
    
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    Epilepsy of adulthood.

    
    
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    Late epilepsy (age 30 and up; always consider a primary organic disease as the cause).

  
  
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  Setting in which seizures are most frequent, for example:

  
  
  
  
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    Sleep epilepsy.

    
    
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    Epilepsy on awakening.

  
  
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  EEG correlate and corresponding topographic localization, for example:

  
  
  
  
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    Generalized epilepsy.

    
    
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    Focal (= partial) epilepsy.

  
  
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  Finally, the clinical features of each seizure. The International League against Epilepsy has developed, and recently revised, a nomenclature for the different clinical types of epileptic seizure, which is reproduced in ▶ Table 9.2. For completeness, the table includes both the older and the newer nomenclature, because the older system is still in widespread use. ▶ Table 9.1 (classification of the epilepsies) also includes the terminology of both systems of classification.

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Table 9.1 Classification of the epilepsies

  Previous terminology	New terminology
  Idiopathic	Genetic According to current knowledge, the seizures are the direct result of one or more known or presumed genetic changes. The epileptic seizures are the main manifestation of the genetic disease
  Symptomatic	Structural or metabolic The patient is suffering from an entirely different condition or disease that has been shown in conclusive scientific studies to be associated with a markedly elevated risk of developing epilepsy, or there are clearly recognizable structural changes in the brain of a type known to be epileptogenic
  Cryptogenic	Of unknown cause “Of unknown cause” is a neutral designation of the fact that the nature of the underlying cause of the patient’s epilepsy could not be determined up to the present time
  Source: Adapted from Diener HC, Weimar C, Berlit P, et al. Leitlinien für Diagnostik und Therapie in der Neurologie. Stuttgart: Thieme; 2012.

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Table 9.2 Classification of epileptic seizure types as proposed by the International League against Epilepsy

  Previous terminology	New terminology
  Localization-related (focal, partial) seizures	Focal seizures
  Simple focal (simple partial) Focal motor Aura Automatisms Complex focal (complex partial), psychomotor Secondary generalized	Characteristics of focal seizures relating to impairment during the seizure: Without impairment of consciousness or attention: With observable motor or autonomic components (cf. section ▶ 9.3.1 and ▶ Table 9.9) With only subjective somatosensory, special sensory, or mental phenomena (cf. ▶ Table 9.9) With impairment of consciousness or attention: dyscognitive type With progression to a bilateral convulsive seizure (with tonic, clonic, or tonic–clonic elements)
  Generalized seizures	Generalized seizures
  Tonic–clonic (grand mal) Absences Myoclonic Clonic Tonic Atonic (astatic)	Tonic–clonic (in any combination) Absences Eyelid myoclonus with absence Typical Atypical With special features Myoclonic absence Myoclonic Myoclonic Myoclonic–atonic Myoclonic–tonic Clonic Tonic Atonic
  Unclassifiable seizures	Unknown
  –	Epileptic spasms
  Source: Adapted from Diener HC, Weimar C, Berlit P, et al. Leitlinien für Diagnostik und Therapie in der Neurologie. Stuttgart: Thieme; 2012.

9.1.2 Practical Clinical Management of a Suspected Epileptic Seizure

History and physical examination A thorough history is of the essence for the diagnosis of epilepsy and its differentiation from other, nonepileptic disorders (see later). A description of the seizures should also be obtained from someone who saw the patient having a seizure, if possible, because patients usually suffer amnesia for the seizures. The questions to be asked are summarized in ▶ Table 9.3. A video clip of a seizure is also a helpful part of the history that can be very useful in differential diagnosis: nowadays, the patient’s family can generally make one of these easily with a smartphone. The position of the eyes during the seizure is particularly significant ( ▶ Fig. 9.1).

When performing the physical examination, the examiner should pay special attention to the following:

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  Any physical evidence that a seizure has occurred.

  
  
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  Any signs of a neurologic or general medical disease that may have caused the seizure ( ▶ Table 9.4).

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Table 9.4 Physical examination

  The physical examination of a patient after a suspected seizure
  Evidence that an epileptic seizure has occurred	Tongue bite Incontinence of urine or stool Conjunctival hemorrhage External injury Fractures Shoulder dislocation
  Evidence implicating an underlying illness as the cause of the seizure	Neurologic deficits on physical examination, signs of intracranial hypertension (especially papilledema); these indicate an underlying organic disease of the brain Abnormal mental status (indicating intoxication or the effect of licit or illicit drugs) Evidence of general medical illness as the underlying condition (e.g., metabolic or endocrine disease, cardiovascular disease as a cause of a possible prior stroke)

General diagnostic aspects If the clinical findings suggest that an epileptic seizure has occurred, a series of laboratory studies and ancillary tests should be performed. These are indicated as part of the initial evaluation of every case of suspected epilepsy and mainly serve to detect, or rule out, any possible symptomatic cause of the seizure ( ▶ Table 9.5).

General therapeutic aspects If the diagnosis of epilepsy can be made securely on the basis of the clinical findings and further testing, an appropriate course of therapy must be decided upon. Any underlying cause of symptomatic epilepsy should be treated (causally directed treatment); moreover, the predisposition to seizures can be treated symptomatically with one or a combination of drugs (antiepileptic drugs, AEDs). Not every epileptic seizure implies a need for treatment. In many patients with a first seizure, it may be best to wait and see whether the event will repeat itself, as long as this presents no special danger and the patient agrees. The decision whether to treat with drugs must always be taken on an individual basis, with due consideration of the patient’s personality, life situation, occupation, need to drive a car, and so forth.

The general principles of the treatment of epilepsy are as follows:

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  Thorough patient education.

  
  
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  Avoidance of precipitating factors (regular sleep habits, no excessive alcohol consumption, no illicit drugs, caution with prescription drugs, avoidance of strobe lights).

  
  
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  Treatment of the underlying disease, if any (e.g., resection of a meningioma).

  
  
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  If pharmacotherapy is indicated: choice of a suitable drug for the particular seizure type ( ▶ Table 9.6).

  
  
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  Gradual increase of the dose till seizure control is achieved or intolerable side effects arise. Beware of treatment failure through underdosing: the side effect threshold varies greatly from patient to patient and must be crossed, or nearly so, before a drug can be declared ineffective.

  
  
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  Meticulous follow-up for possible side effects, with especially close observation in the initial phase of treatment.

  
  
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  Checking for compliance, for example, with serum levels, if the drug seems to be ineffective.

  
  
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  If treatment with the first drug tried is truly ineffective despite maximal dosing and adequate compliance, switch to another drug of first choice, in gradual and overlapping fashion.

  
  
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  Combination therapy only if monotherapy fails.

  
  
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  Determination of serum levels when:

  
  
  
  
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    Poor compliance is suspected.

    
    
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    Toxic drug effects are suspected.

    
    
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    Drug interactions are suspected, particularly those involving enzyme induction.

    
    
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    An already high dose is to be raised even further.

    
    
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    Medicolegal questions arise, particularly with respect to permission to drive.

  
  
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  Rules of thumb for the discontinuation of AEDs: the patient should be free of seizures for at least 2 years; the EEG should be free of potentials that are typical for epilepsy; traditionally, the drug is slowly tapered to off over several months (although the need for this has not been demonstrated); the patient and family must be explicitly told that seizures may recur during or after the tapering phase.

  
  
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  If a patient with focal seizures has not become seizure-free with two AEDs, the possibility of epilepsy surgery should be considered early.

  
  
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  In patients with treatment-resistant focal or generalized seizures, the seizure frequency can be reduced with vagus nerve stimulation.

▶ Table 9.6 contains an overview of the major AEDs that are currently available and the indications for each. A practical algorithm for the treatment of epilepsy is shown in ▶ Fig. 9.2.

Related posts:

Metabolic Disorders and Systemic Diseases Affecting the Nervous System Cerebellar Diseases and Other Conditions Causing Ataxia Brain Tumors Nontraumatic Intracranial Hemorrhage Cerebral Ischemia and Ischemic Stroke Diseases of the Spinal Cord

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