Grand mal seizures have two stages:

• Tonic phase. Loss of consciousness occurs, and the muscles suddenly contract and cause the person to fall down. This phase tends to last about 10 to 20 seconds.
• Clonic phase. The muscles go into rhythmic contractions, alternately flexing and relaxing. Convulsions usually last one to two minutes or less.

The following signs and symptoms occur in some but not all people with grand mal seizures:

• A scream. Some people may cry out at the beginning of a seizure.
• Loss of bowel and bladder control. This may happen during or following a seizure.
• Unresponsiveness after convulsions. Unconsciousness may persist for several minutes after the convulsion has ended.
• Confusion. A period of disorientation often follows a grand mal seizure. This is referred to as postictal confusion.
• Fatigue. Sleepiness is common after a grand mal seizure.
• Severe headache. Headaches may occur after a grand mal seizure.

Grand mal seizures occur when the electrical activity over the whole surface of the brain becomes abnormally synchronized. The brain's nerve cells normally communicate with each other by sending electrical and chemical signals across the synapses that connect the cells.

In people who have seizures, the brain's usual electrical activity is altered and many nerve cells fire at the same time. Exactly what causes the changes to occur often remains unknown.

However, grand mal seizures are sometimes caused by underlying health problems, such as:

Injury or infection

• Traumatic head injuries
• Infections, such as encephalitis or meningitis, or a history of such infections
• Injury due to a previous lack of oxygen
• Stroke

Congenital or developmental abnormalities

• Blood vessel malformations in the brain
• Genetic syndromes
• Brain tumors

Metabolic disturbances

• Very low blood levels of glucose, sodium, calcium or magnesium

Withdrawal syndromes

• Using or withdrawing from drugs, including alcohol

Risk factors for grand mal seizures include:

• A family history of seizure disorders
• Any injury to the brain from trauma, a stroke, previous infection and other causes
• Sleep deprivation
• Medical problems that affect electrolyte balance
• Illicit drug use
• Heavy alcohol use

Having a seizure at certain times can lead to circumstances that are dangerous for you or others. You might be at risk of:

• Falling. If you fall during a seizure, you can injure your head or break a bone.
• Drowning. If you have a seizure while swimming or bathing, you're at risk of accidental drowning.
• Car accidents. A seizure that causes either loss of awareness or control can be dangerous if you're driving a car or operating other equipment.
• Pregnancy complications. Seizures during pregnancy pose dangers to both mother and baby, and certain anti-epileptic medications increase the risk of birth defects. If you have epilepsy and plan to become pregnant, work with your doctor so that he or she can adjust your medications and monitor your pregnancy, as needed.
• Emotional health issues. People with seizures are more likely to have psychological problems, such as depression and anxiety. Problems may be a result of difficulties dealing with the condition itself as well as medication side effects.