Generalized Seizure | What Happens When the Entire Brain Misfires at Once?

A tonic-clonic seizure is a type of generalized seizure that affects the entire brain from the onset. It is characterized by a sudden, abnormal burst of synchronized electrical activity throughout both hemispheres of the brain. This event consists of two distinct phases. The first is the "tonic" phase, where the individual loses consciousness and their muscles become rigid and stiff. This can cause them to fall, often leading to injury. Following this, the "clonic" phase begins, marked by rhythmic, convulsive jerking of the limbs. During the seizure, breathing may become irregular or stop temporarily, and the person’s skin may take on a bluish tint due to a lack of oxygen. The entire event typically lasts for one to three minutes. After the convulsions cease, the individual enters a "postictal" state. This recovery period is characterized by deep confusion, drowsiness, headache, and muscle soreness. The person will have no memory of the seizure itself. Tonic-clonic seizures are a serious medical event resulting from a widespread electrical storm in the brain, disrupting normal function entirely.

Absence seizures are another form of generalized seizure, but they present very differently from tonic-clonic seizures. Instead of convulsions, they involve a brief, sudden lapse of consciousness that lasts only a few seconds. An individual having an absence seizure will abruptly stop all activity and appear to be staring blankly into space. They may exhibit subtle motor signs, such as eye blinking or slight mouth movements. To an observer, it can look like simple daydreaming. However, unlike daydreaming, the person cannot be snapped out of it. After the seizure, which typically lasts less than 20 seconds, the person returns to full awareness immediately, with no memory of the pause. These seizures are also caused by abnormal electrical signals that disrupt the entire brain, but in a less violent manner than convulsive seizures. They are most common in children and can occur hundreds of times a day, potentially interfering with learning and daily functioning if not properly diagnosed and treated.

Generalized seizures arise from a variety of factors that affect the brain's electrical stability. A significant number of cases have a genetic basis, meaning a predisposition to seizures is inherited. Other common causes include structural abnormalities or damage to the brain, which can result from a head injury, a stroke (which deprives brain cells of oxygen), or a brain tumor. Infections that cause inflammation of the brain, such as meningitis or encephalitis, are also known triggers. In some individuals, metabolic imbalances, like very low blood sugar or sodium levels, can provoke a seizure. Despite these known causes, a large percentage of individuals with a seizure disorder have what is termed "idiopathic" epilepsy, where no specific cause can be identified.

Diagnosing generalized seizures requires a comprehensive medical evaluation. The cornerstone of this process is the electroencephalogram (EEG). This test records the brain's electrical activity through electrodes placed on the scalp. During a seizure, an EEG can capture the characteristic patterns of abnormal, synchronized brainwaves that confirm the diagnosis. To identify any underlying structural issues, physicians use neuroimaging techniques. A Magnetic Resonance Imaging (MRI) scan provides detailed images of the brain's structure, while a Computed Tomography (CT) scan is often used in emergency situations to quickly check for issues like bleeding or tumors. A detailed account of the seizure events from an eyewitness is also critically important, as it helps the doctor classify the seizure type accurately.

If you see someone having a tonic-clonic seizure, the primary goal is to ensure their safety. It is crucial to stay calm. Gently guide the person to the floor and clear the surrounding area of any hard or sharp objects to prevent injury from the convulsions. Place something soft and flat, like a folded jacket, under their head. Turn the person onto their side. This is a critical step, as it helps keep their airway clear and prevents them from choking on saliva or vomit. It is a dangerous myth that you should put something in their mouth; never do this, as it can cause injury to their teeth, jaw, or your fingers. Time the seizure from start to finish. Call for emergency medical assistance if the seizure lasts for more than five minutes, if the person has difficulty breathing afterward, if another seizure begins immediately, or if the person is injured.