Epilepsy Syndromes

Epilepsy syndromes

Epilepsy syndromes are disorders in which epilepsy is a predominant feature, and there is sufficient evidence (e.g. through clinical, EEG, radiologic, or genetic observations) to suggest a common underlying mechanism. Three important epilepsy syndromes are listed below:

Juvenile Myoclonic epilepsy

Juvenile Myoclonic epilepsy (JME) is a generalized seizure disorder of unknown cause that appears in early adolescence and is usually characterized by bilateral Myoclonic jerks that may be single or repetitive.

The Myoclonic seizures are most frequent in the morning after awakening and can be provoked by sleep deprivation. Consciousness is preserved unless the myoclonus is a especially severe.

Many patients also experience generalized tonic-clonic seizures, and up to one-third have absence seizures. The condition is otherwise benign, and although complete remission is uncommon.

The seizures respond well to appropriate anticonvulsant medication. There is often a family history of epilepsy, and genetic linkage studies suggest a polygenic cause.

Lennox-gastaut syndrome

Lennox-gastaut syndrome occurs in children and is defined by the following triad:

(1) multiple seizure types (usually including generalized tonic-clonic, atonic, and atypical absence seizures);

(2) an EEG showing slow (<3 Hz) spike-and-wave discharges and variety of other abnormalities; and

(3) impaired cognitive function in most but not al cases. Lennox-gastaut syndrome is associated with CNS disease or dysfunction from a variety of causes.

Including developmental abnormalities, perinatal hypoxia/ischemia, trauma, infection, and other acquired lesions. The multifactorial nature of this syndrome suggest that it is a nonspecific response of the brain to diffuse neural injury.

Unfortunately, many patients have a poor prognosis due to the underling CNS disease and the physical and psychosocial consequences of severe, poorly controlled epilepsy.

Mesial temporal lobe epilepsy syndrome

Mesial temporal lobe epilepsy (MTLE) is the most common syndrome associated with complex partial seizures and is an example of a symptomatic, partial epilepsy with distinctive clinical, electroencephalographic, and pathologic features.

High-resolution magnetic resonance imaging(MRI) can detect the characteristic hippocampal sclerosis that appears to be essential in the Pathophysiology of MTLE for many patients.

Recognition of this syndrome is especially important because it tends to be refractory to treatment with anticonvulsants but responds extremely well to surgical intervention.Advances in the understanding of basic mechanisms of epilepsy have come through studies of experimental models of MTLE.

Three additional features of partial motor seizures are worth nothing. First, in some patients the abnormal motor movements may begin in a very restricted region such as the fingers and gradually progress (Over seconds to minutes) to include a larger portion of the extremity.

This phenomenon, described by Hughlings Jackson and known as a “Jacksonian march” represents the spread of seizure activity over a progressively larger region of motor cortex. Seconds.

Patients may experience a localized paresis (Todd’s paralysis) for minutes to many hours in the involved region following the seizure. Third, in rare instances the seizure may continue for hours or days. This condition, termed epilesia partialis continua, is often refractory to medical therapy.

Complex partial seizure

Complex partial seizures are characterized by focal seizure activity accompanied by a transient impairment of the patient’s ability to maintain normal contact with the environment. The patient is unable to respond appropriately to verbal commands during the seizure and has impaired recollection or awareness of the ictal phase.

The seizures frequently begin with an aura (i.e. a simple partial seizure) that is stereotypic for the patient. The start of the ictal phase is often a sudden behavioral arrest or motionless stare, which marks the onset of the period of amnesia.

The behavioral arrest is usually accompanied y automatisms, which are involuntary, automatic behaviors that have a wide range of manifestations.

Automatisms may consist of very basic behaviors such as chewing, lip smacking swallowing, or “picking” movements of the hands, or more elaborate behaviors such as a display of emotion or running.

The patient is typically confused following the seizures, and the transition to full recovery of consciousness may range from seconds up to an hour.

Examination immediately following the seizure may show an anterograde amnesia or, in cases involving the dominant hemisphere, a postictal aphasia.

Partial seizures with secondary generalization

Partial seizure can spread to involve both cerebral hemispheres and produce a generalized seizure, usually of the tonic-clonic variety. Secondary generalization is observed frequently following simple partial seizures, especially those with a focus in the frontal lobe, but may also be associated with partial seizures occurring elsewhere in the brain.

A partial seizure with secondary generalization is often difficult to distinguish from a primarily generalized tonic-clonic seizure, since bystanders tends to emphasize the more dramatic, generalized convulsive phase of the seizure and overlook the more subtle, focal symptoms present at onset.

In some cases, the focal onset of the seizure becomes apparent only when a careful history identifies a preceding aura (i.e. simple partial seizure). often, however, the focal onset is not clinically evident and may be established only through careful EEG analysis.

Nonetheless, distinguishing between these two entitles is extremely important, as there may be substantial differences in the evaluation and treatment of partial versus generalized seizure disorders.

Understanding Epilepsy Syndromes