Table: Causes of Seizures - Merck Manuals Consumer Version

Causes of Seizures

Cause	Examples
High fever Fever in Adults Fever is an elevated body temperature that occurs when the body's thermostat (located in the hypothalamus in the brain) resets at a higher temperature, primarily in response to an infection... read more	Heatstroke Heatstroke Heatstroke is a life-threatening condition that results in very high body temperature and malfunction of many organ systems, which may be fatal. (See also Overview of Heat Disorders.) Heatstroke... read more Infections
Brain infections Overview of Brain Infections Infections of the brain can be caused by viruses, bacteria, fungi, or, occasionally, protozoa or parasites. Another group of brain disorders, called spongiform encephalopathies, are caused by... read more	Abscess Abscess of the Brain A brain abscess is a pocket of pus in the brain. An abscess may form in the brain when bacteria from an infection elsewhere in the head or in the bloodstream or from a wound enter the brain... read more AIDS Acquired immunodeficiency syndrome (AIDS) Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and is treated with antiretroviral medications. If untreated, it can cause... read more Malaria Malaria Malaria is infection of red blood cells with one of five species of the protozoa Plasmodium. Malaria causes fever, chills, sweating, a general feeling of illness (malaise), and sometimes... read more Meningitis Introduction to Meningitis Meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space). Meningitis can be... read more Rabies Rabies Rabies is a viral infection of the brain that is transmitted by animals and that causes inflammation of the brain and spinal cord. Once the virus reaches the spinal cord and brain, rabies is... read more Syphilis Syphilis Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum. It can occur in three stages of symptoms, separated by periods of apparent good health. Syphilis... read more Tetanus Tetanus Tetanus results from a toxin produced by the anaerobic bacteria Clostridium tetani. The toxin makes muscles contract involuntarily and become rigid. Tetanus usually develops after a wound... read more Toxoplasmosis Toxoplasmosis Toxoplasmosis is infection caused by the protozoan parasite Toxoplasma gondii. Infection occurs when people unknowingly ingest toxoplasma cysts from cat feces or eat contaminated meat... read more Viral encephalitis Encephalitis Encephalitis is inflammation of the brain that occurs when a virus directly infects the brain or when a virus, vaccine, or something else triggers inflammation. The spinal cord may also be involved... read more
Metabolic disorders	High blood levels of sugar ( hyperglycemia Hyperosmolar Hyperglycemic State (HHS) Hyperosmolar hyperglycemic state is a complication of diabetes mellitus that most often occurs in type 2 diabetes. Symptoms of hyperosmolar hyperglycemic state include extreme dehydration and... read more ) or sodium Hypernatremia (High Level of Sodium in the Blood) In hypernatremia, the level of sodium in blood is too high. Hypernatremia involves dehydration, which can have many causes, including not drinking enough fluids, diarrhea, kidney dysfunction... read more Low blood levels of sugar ( hypoglycemia Hypoglycemia Hypoglycemia is abnormally low levels of sugar (glucose) in the blood. Hypoglycemia is most often caused by medications taken to control diabetes. Much less common causes of hypoglycemia include... read more ), calcium Hypocalcemia (Low Level of Calcium in the Blood) In hypocalcemia, the calcium level in blood is too low. A low calcium level may result from a problem with the parathyroid glands, as well as from diet, kidney disorders, or certain drugs. As... read more , magnesium Hypomagnesemia (Low Level of Magnesium in the Blood) In hypomagnesemia, the level of magnesium in blood is too low. (See also Overview of Electrolytes and Overview of Magnesium's Role in the Body.) Magnesium is one of the body's electrolytes,... read more , or sodium Hyponatremia (Low Level of Sodium in the Blood) In hyponatremia, the level of sodium in blood is too low. A low sodium level has many causes, including consumption of too many fluids, kidney failure, heart failure, cirrhosis, and use of diuretics... read more
Other disorders	Kidney failure Overview of Kidney Failure Kidney failure is the inability of the kidneys to adequately filter metabolic waste products from the blood. Kidney failure has many possible causes. Some lead to a rapid decline in kidney function... read more or liver failure Liver Failure Liver failure is severe deterioration in liver function. Liver failure is caused by a disorder or substance that damages the liver. Most people have jaundice (yellow skin and eyes), feel tired... read more , which can lead to dysfunction of the brain (encephalopathy) Vitamin B6 deficiency Vitamin B6 Deficiency Vitamin B6 is in most foods, but people can have vitamin B6 deficiency if they do not absorb it properly. Many foods contain vitamin B6, but extensive processing can remove the vitamin. People... read more (in newborns)
Inadequate oxygen supply to the brain	Abnormal heart rhythms Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more Cardiac arrest Cardiac Arrest and CPR Cardiac arrest is when the heart stops pumping blood and oxygen to the brain and other organs and tissues. Sometimes a person can be revived after cardiac arrest, particularly if treatment is... read more Carbon monoxide poisoning Carbon Monoxide Poisoning Carbon monoxide is a colorless, odorless gas that is produced when many materials are burned and can be toxic when breathed in large amounts Carbon monoxide poisoning is common. Symptoms may... read more Near drowning Drowning Drowning occurs when submersion in liquid causes suffocation or interferes with breathing. During drowning, the body is deprived of oxygen, which can damage organs, particularly the brain. Doctors... read more Near suffocation Stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction) and symptoms that... read more Vasculitis Overview of Vasculitis Vasculitic disorders are caused by inflammation of the blood vessels (vasculitis). Vasculitis can be triggered by certain infections or drugs or can occur for unknown reasons. People may have... read more
Structural damage to the brain	Brain tumor Overview of Brain Tumors A brain tumor can be a noncancerous (benign) or cancerous (malignant) growth in the brain. It may originate in the brain or have spread (metastasized) to the brain from another part of the body... read more (noncancerous or cancerous) Head injury Overview of Head Injuries Head injuries that involve the brain are particularly concerning. Common causes of head injuries include falls, motor vehicle crashes, assaults, and mishaps during sports and recreational activities... read more Hydrocephalus Hydrocephalus Hydrocephalus is an accumulation of extra fluid in the normal spaces within the brain (ventricles) and/or between the inner and middle layers of tissues that cover the brain (the subarachnoid... read more Intracranial hemorrhage Intracranial Hematomas Intracranial hematomas are accumulations of blood inside the skull, either within the brain or between the brain and the skull. Intracranial hematomas form when a head injury causes blood to... read more (bleeding within the skull) Stroke
Abnormalities present or occurring at birth, including genetic disorders	Birth defect Overview of Brain and Spinal Cord Birth Defects Birth defects of the brain and spinal cord can occur in early or late fetal development. Typical symptoms include intellectual disability, paralysis, incontinence, or loss of sensation in some... read more Hereditary metabolic disorders, such as Tay-Sachs disease Tay-Sachs Disease and Sandhoff Disease Tay-Sachs disease and Sandhoff disease are types of lysosomal storage disorder called sphingolipidoses and are caused by a buildup of gangliosides in the tissues in the brain. These diseases... read more or phenylketonuria Phenylketonuria (PKU) Phenylketonuria is a disorder of amino acid metabolism that occurs in infants born without the ability to normally break down an amino acid called phenylalanine. Phenylalanine, which is toxic... read more Injury during birth Birth Injuries in Newborns Birth injury is damage that occurs as a result of physical pressure during the birthing process, usually during transit through the birth canal. Many newborns have minor injuries during birth... read more
Fluid accumulation in the brain (cerebral edema)	Eclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more Hypertensive encephalopathy Symptoms
Prescription drugs*	Buspirone (used to treat anxiety disorders) Camphor Chlorpromazine (used to treat schizophrenia) Ciprofloxacin (an antibiotic) Chloroquine (used to treat malaria) Clozapine (usually used to treat schizophrenia) Cyclosporine (used to prevent and treat rejection of organ transplants) Imipenem (an antibiotic) Indomethacin (used to relieve pain and reduce inflammation) Meperidine (used to relieve pain) Phenytoin† Theophylline (used to treat asthma and other airway disorders) Tricyclic antidepressants
Recreational drugs	Amphetamines Amphetamines Amphetamines are stimulant drugs that are used to treat certain medical conditions but are also subject to abuse. Amphetamines increase alertness, enhance physical performance, and produce euphoria... read more Cocaine Cocaine Cocaine is an addictive stimulant drug made from leaves of the coca plant. Cocaine is a strong stimulant that increases alertness, causes euphoria, and makes people feel powerful. High doses... read more (overdose)
Withdrawal of a drug after heavy use	Alcohol Alcohol Use Alcohol (ethanol) is a depressant (it slows down brain and nervous system functioning). Consuming large amounts rapidly or regularly can cause health problems, including organ damage, coma,... read more General anesthetics (used during surgery) Sedatives Misuse of Antianxiety Medications and Sedatives Antianxiety and sedative medications are prescription drugs used to relieve anxiety and/or help with sleep, but their use can result in dependency and a substance use disorder. Using prescription... read more , including sleep aids
Exposure to toxins	Lead Lead Poisoning Lead poisoning affects many parts of the body, including the brain, nerves, kidneys, liver, and blood. Children are particularly susceptible because their nervous system is still developing... read more Strychnine
* Various drugs can cause seizures if too much is taken. In some people, certain drugs can make seizures more likely to occur by making nerve cells in the brain easier to stimulate. These drugs are said to lower the seizure threshold.
† Phenytoin, used to treat seizure disorders, can cause seizures if too much is taken.