Generalized Tonic-Clonic Seizures Clinical Presentation

  • Author: David Y Ko, MD; Chief Editor: Selim R Benbadis, MD  more...
Updated: Jun 30, 2015


Patients with generalized tonic-clonic seizures may report having a prodrome, which comprises premonitory symptoms occurring hours or days before a seizure. Common prodromes include mood changes, sleep disturbances, lightheadedness, anxiety, irritability, difficulty concentrating and, rarely, an ecstatic feeling.

Patients with generalized tonic-clonic seizures do not have auras. An aura represents a simple partial seizure, and a reliable history of aura identifies the seizure as partial and not generalized. For seizures that arise out of sleep (nocturnal seizures), it may be hard to distinguish a primary generalized seizure from a partial seizure with secondary generalization.

Other symptoms that have been described less consistently are abdominal pain, facial pallor, or headache. Witnesses of a patient's seizure should be asked about the stereotypical ictal cry, which is strongly associated with generalized tonic-clonic seizures.[2]


Physical Examination

The patient may have completely nonfocal findings on neurologic examination when not having seizures. Seizures typically are divided into tonic, clonic, and postictal phases, which are described in detail in this section.

Tonic phase

This stage lasts for 10-20 seconds. Generalized convulsive seizures may begin with myoclonic jerks or, rarely, with absences. The tonic phase begins with flexion of the trunk and elevation and abduction of the elbows. Subsequent extension of the back and neck is followed by extension of arms and legs. This can be accompanied by apnea, which is secondary to laryngeal spasm.

Autonomic signs are common during this phase and include increase in pulse rate and blood pressure, profuse sweating, and tracheobronchial hypersecretion. Although urinary bladder pressure rises, voiding does not occur because of sphincter muscle contraction.

Clonic phase

The tonic stage gives way to clonic convulsive movements, in which the tonic muscles relax intermittently for a variable period of time.

During the clonic stage, a generalized movement occurs at a rate of about 4-8 Hz. This is because phases of atonia alternate with repeated violent flexor spasms. Each spasm is accompanied by pupillary contraction and dilation. Some patients may bite their tongue or cheek.

The atonic periods gradually become longer until the last spasm. Voiding may occur at the end of the clonic phase as sphincter muscles relax. The atonic period lasts about 30 seconds. The patient continues to be apneic during this phase.

The convulsion, including tonic and clonic phases, lasts around 1-2 minutes.

Postictal state

The postictal state includes a variable period of unconsciousness during which the patient becomes quiet and breathing resumes. The patient gradually awakens, often after a period of stupor or sleep, and often is confused, with some automatic behavior. Headache and muscular pain are common. The patient does not recall the seizure itself.

Contributor Information and Disclosures

David Y Ko, MD Associate Professor of Clinical Neurology, Associate Director, USC Adult Epilepsy Program, Keck School of Medicine of the University of Southern California

David Y Ko, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, American Headache Society, American Clinical Neurophysiology Society

Disclosure: Received honoraria from UCB for speaking and teaching; Received consulting fee from Lundbeck for consulting; Received consulting fee from Westward for consulting; Received consulting fee from Esai for consulting; Received consulting fee from Supernus for consulting; Received consulting fee from Sunovion for speaking and teaching.


Soma Sahai-Srivastava, MD Director of Neurology Ambulatory Care Services, LAC and USC Medical Center; Assistant Professor, Department of Neurology, Keck School of Medicine of the University of Southern California

Soma Sahai-Srivastava, MD is a member of the following medical societies: American Academy of Neurology, American Medical Association, American Headache Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Jose E Cavazos, MD, PhD, FAAN, FANA, FACNS Professor with Tenure, Departments of Neurology, Pharmacology, and Physiology, Assistant Dean for the MD/PhD Program, Program Director of the Clinical Neurophysiology Fellowship, University of Texas School of Medicine at San Antonio; Co-Director, South Texas Comprehensive Epilepsy Center, University Hospital System; Director, San Antonio Veterans Affairs Epilepsy Center of Excellence and Neurodiagnostic Centers, Audie L Murphy Veterans Affairs Medical Center

Jose E Cavazos, MD, PhD, FAAN, FANA, FACNS is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Neurological Association, Society for Neuroscience, American Epilepsy Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Brain Sentinel, consultant.<br/>Stakeholder (<5%), Co-founder for: Brain Sentinel.

Chief Editor

Selim R Benbadis, MD Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, Tampa General Hospital, University of South Florida Morsani College of Medicine

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, American Medical Association

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cyberonics; Eisai; Lundbeck; Sunovion; UCB; Upsher-Smith<br/>Serve(d) as a speaker or a member of a speakers bureau for: Cyberonics (Livanova); Eisai; Lundbeck; Sunovion; UCB<br/>Received research grant from: Cyberonics (Livanova); GW, Lundbeck; Sunovion; UCB; Upsher-Smith.

Additional Contributors

Ramon Diaz-Arrastia, MD, PhD Professor, Department of Neurology, University of Texas Southwestern Medical Center at Dallas, Southwestern Medical School; Director, North Texas TBI Research Center, Comprehensive Epilepsy Center, Parkland Memorial Hospital

Ramon Diaz-Arrastia, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, New York Academy of Sciences, Phi Beta Kappa

Disclosure: Nothing to disclose.

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