An epileptic seizure is a paroxysmal disorder characterized by an abnormal, excessive, hypersynchronous discharge of neurons which results in an alteration of function of the patient. This alteration of function can be quite dramatic such as during a generalized tonic–clonic (grand mal) seizure or much more subtle such as during an absence (petit mal) seizure. Epilepsy is a condition characterized by repeated, unprovoked seizures. If the seizures are consistently provoked, such as by fever or hypoglycemia, the term epilepsy should not be used. Epilepsy is not a single disorder, but rather a symptom of underlying brain dysfunction.

A classification of epileptic seizures and syndromes is an essential step in developing communication and provides a basis for an understanding of the underlying processes of epilepsy. A classification system provides guidance in determining the diagnostic evaluation, treatment, and prognosis (Table 1–1). However, no single classification code can cover the multiple aspects of epilepsy including behavioral and electroencephalographic (EEG) features, age of onset, and etiology (including genetic susceptibility and acquired insults). In addition, limited knowledge regarding the basic mechanism does not permit classification on the physiopathology of the disorder.

The first modern classification system of seizures was proposed in 1969 by an ad hoc committee of the International League Against Epilepsy.¹ In 1981, the classification was revised.² It is based on two criteria: the clinical features and the EEG features of the seizures. Seizures are classified into two broad categories: (a) partial seizures (seizures beginning in a limited location in the brain) and (b) generalized seizures (seizures that are bilaterally symmetrical and without focal onset). Seizures are then further classified, depending on the exact clinical and EEG manifestations of the seizure. In 2010 the International League Against Epilepsy (ILAE) proposed a revision of the terminology and concepts for organization of seizures and epilepsies.³ The ILAE felt they did not have enough data to support a new classification. Instead the ILAE provided new nomenclature for the seizures and epilepsies. In this chapter, the new terminology will be used with the older nomenclature in parentheses.

The various seizure types are described here and Fig. 1–1 provides a guide for correctly diagnosing seizure type.

FOCAL (PARTIAL) SEIZURES

Focal seizures are those that originate within networks limited to one hemisphere. Focal seizures may be classified further into those without impairment of consciousness or awareness (formerly termed simple partial seizures) and those with impairment of consciousness or awareness (formerly classified as complex partial seizures). Determining impaired consciousness may be quite difficult, particularly in patients in whom the seizures involve language cortex, patients with cognitive impairment, and in neonates or infants. In patients not demonstrating impairment of consciousness or awareness, further subdivision into seizures with: (i) observable motor or autonomic components and (ii) subjective sensory or psychic phenomenon. Focal seizures can evolve into a bilateral, convulsive seizure.

The signs or symptoms of focal seizures depend on the location of the focus. Seizures involving the motor cortex most commonly consist of rhythmic or semirhythmic clonic activity of the face, arm or leg. There is usually no difficulty in diagnosing this type of seizure. Seizures with somatosensory, autonomic, and psychic symptoms (hallucinations, illusions, déjà vu) may be more difficult to diagnose. Psychic symptoms usually occur as a component of a focal seizure with impaired consciousness or responsiveness. Focal seizures can occur at any age.

Focal seizures with impairment of consciousness or awareness (complex partial seizures), formerly termed temporal lobe or psychomotor seizures are one of the most common seizure types encountered in both children and adults. Focal seizures without impaired consciousness or awareness may evolve into seizures with impaired consciousness. The beginning of the focal seizure may serve as a warning to the patient (i.e., aura) that a more severe seizure is pending. It is important to recognize that the aura may enable the clinician to determine the cortical area from which the seizure is beginning.

The impairment of consciousness or awareness may be subtle. For example, the patient may either not respond to commands or respond in an abnormally slow manner. While focal seizures with altered consciousness or awareness may be characterized by simple staring and impaired responsiveness, behavior is usually more complex during the seizure. Automatisms, semipurposeful behaviors of which the patient is unaware and subsequently cannot recall, are common during the period of impaired consciousness. Types of automatism behaviors are quite variable and may consist of activities such as facial grimacing, gestures, chewing, lip smacking, snapping fingers and repeating phrases. The patient does not recall fully this activity following the seizure.