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Generalized Tonic-Clonic Seizures

Background

A seizure is an abnormal paroxysmal discharge of cerebral neurons due to cortical hyperexcitability. The new International Classification of Seizures divides seizures into 3 categories: generalized onset, focal onset (formerly partial seizures) and unknown onset.
This article uses the term “partial seizures” throughout although the term focal is now the official term. However, many patients and practitioners are using old terminology.

Partial seizures result from a seizure discharge within a particular brain region or focus, and they manifest focal symptoms and may progress to secondarily generalized seizure (now called bilateral tonic clonic, with the term generalization reserved for primary generalized seizure only).
Primary generalized seizures probably begin in the thalamus and other subcortical structures, but on scalp electroencephalographic (EEG) recordings, they may appear to start simultaneously in both cerebral hemispheres; therefore, they manifest symptoms bilaterally in the body and are always associated with loss of consciousness.

Partial seizures can generalize secondarily and result in tonic-clonic activity. Some partial seizures have very rapid generalization, and the partial phase of the seizure may not be readily apparent clinically or even on scalp EEG recordings. Some partial seizures may have an aura (the new classification discourages the use of aura and suggests the term simple focal seizure aware instead), but primary generalized seizures usually do not. However, secondarily generalized partial seizures (now called focal with bilateral tonic clonic in the new classification) are not included in the category of generalized seizures, which includes only primary generalized seizures.

Generalized seizures can be classified as atonic, tonic, clonic, tonic-clonic, myoclonic, or absence on the basis of clinical symptoms and EEG abnormalities. Tonic seizure is the rigid contracture of muscles, including respiratory muscles, which is usually brief. The clonic component is the rhythmic shaking that occurs and is longer. Together, a generalized tonic-clonic seizure (GTCS) is also called a grand mal seizure and is one of the most dramatic of all medical conditions.

The following epilepsy syndromes may have generalized seizures:

Benign neonatal convulsions

Benign myoclonic epilepsy of infancy

Childhood absence epilepsy

Juvenile absence epilepsy

Juvenile myoclonic epilepsy

Generalized tonic-clonic seizures upon awakening

Patients with generalized tonic-clonic seizures and idiopathic generalized epilepsy typically have no evidence of any localized, regional, or diffuse brain abnormality on history, physical, or neurologic examination; clinical laboratory testing; or imaging studies. The awake EEG of patients with generalized tonic-clonic seizure may be normal; however, certain specific interictal EEG patterns can be distinctive of generalized epilepsy syndromes (see Workup). In generalized seizure patients, the activation of photic stimulation and/or hyperventilation during an EEG may produce spikes or even seizures.

A number of medications are used for the treatment of generalized tonic-clonic seizures. The choice of drug should be tailored to the individual patient and to the epilepsy syndrome, not only to the seizure type (see Treatment and Management, as well as Medication).

Go to Epilepsy and Seizures, First Adult Seizure, and First Pediatric Seizure for an overview of these topics.

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