Generalized Tonic-Clonic Seizures Clinical Presentation

Updated: Dec 31, 2022
  • Author: David Y Ko, MD; Chief Editor: Selim R Benbadis, MD  more...
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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/focal aware 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 decreased consciousness 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.



Seizures may lead to injuries, including falls, shoulder dislocation, burns, fractures, oral/tongue trauma, and urinary or bowel incontinence. Loss of memory and postictal state and even brain injury may result, as well as aspiration pneumonia, and if prolonged, rhabdomyolysis. If a seizure does not stop, it can lead to status epilepticus. There may be an increased risk of Sudden Unexplained Death in Epilepsy (SUDEP).