What Causes Amnesia?

Amnesia is not a disease. One person cannot pass it to another, and it is not hereditary, handed down through families from one generation to the next. It can be a symptom of an illness, as in the forgetfulness of Alzheimer’s disease. It can be the result of a bad accident in which the head gets injured, or it can be caused by drugs, alcohol, or even poor nutrition when a person’s diet is missing important nutrients. Amnesia can also be caused by traumatic emotional events, as in the case of psychogenic forgetting.

“Memory problems resulting from brain trauma can vary widely in nature and extent,” says author Lisa Schoenbrodt. “The processes involved in memory are very complex. Damage to any part of this intricate system can disrupt your ability to categorize, link, and recall past experiences.”²⁵

Because amnesia is not a disease, and because there are so many types of amnesia and so many possible causes, it is hard for scientists to find cures or treatments. The best way to deal with memory loss may be to prevent the things that cause it. Therefore, scientists actively study known causes of amnesia in the hope that they can stop brain damage from happening in the first place.

Traumatic Brain Injury

The brain has the best protection the body can provide. It is buried within the thick, bony shield of the skull, where it is surrounded by fluid so that when the head moves, the delicate brain does not constantly bump against the skull. It is a very effective safety system. Despite this, anything that hurts the head can hurt the brain, and the way people are shaped makes the human head more vulnerable to injury than the heads of most animals.

For one thing, humans stand upright. For the size of the feet on which they balance, humans are naturally rather top-heavy. If someone stumbles and falls, the head comes from the greatest height, so it is the body part that hits the ground the hardest.

Human heads also perch on longer, more wobbly necks than the heads of many animals. (Giraffes and storks are two good exceptions, but giraffes walk steadily on four legs, and a stork’s brain is not big, so its head simply is not that heavy.) The heavy human head can whip backward or forward on the end of the neck during a fall, causing injury to the spinal cord. Although other primates, such as gorillas and chimpanzees, also have quite large brains, their necks are shorter and thicker than a human’s, and they spend more time squatting than standing, so the risk of a head injury from a stumble is minimal. Humans are unique in the animal kingdom in that they have a very high risk of head injury.

“Although growing a big neocortex gave us ‘book smarts,’” say Temple Grandin and Catherine Johnson, authors of Animals in Translation: Using the Mysteries of Autism to Decode Animal Behavior, “we paid a price. For one thing, bigger frontal lobes probably made humans a lot more vulnerable to brain damage and dysfunction of just about any kind.”²⁶

Human beings also place themselves in far more dangerous situations than other animals do. A monkey travels only as fast as its body is designed to go. People, on the other hand, have invented machines to help them reach incredible speeds. Bicycles, motorcycles, cars, and planes, for example, allow humans to travel at speeds far greater than their bodies are designed to go. The impact of a crash at such speeds can be serious and sometimes fatal.

During such an accident, the head all too often gets the worst of the damage. The brain rattles around inside the skull, smashing against the bone. When the brain is injured this way, it is called a concussion, which means “violent shaking.” The result is traumatic brain injury, one of the most common and most serious causes of amnesia. The two main symptoms of traumatic brain injury are loss of consciousness and a period of memory loss after the injury, called posttraumatic amnesia (PTA).

“A patient with a concussion may display any combination of . . . signs and symptoms,” says author and doctor Robert C. Cantu, in an article in the Journal of Athletic Training. “Many consider the duration of PTA the best indicator of traumatic brain injury severity.”²⁷

PTA can be retrograde or anteretrograde, depending on whether there is a loss of memories from before the accident or a loss of the ability to remember new things afterward. According to Cantu, “we now know that structural damage with loss of brain cells does occur with some concussions.” Anteretrograde memory, he says, “is frequently the last function to return after the recovery from a loss of consciousness.”²⁸ In many patients whose head injury was very severe, memory may never be completely normal again.

“The most common cognitive impairment among severely head-injured patients is memory loss,”²⁹ says Sandra J. Judd in Brain Disorders Sourcebook. About 270,000 people in the United States each year have a traumatic brain injury, she says, and 80,000 of them “live with significant disability as a result of the injury.”³⁰

Because most traumatic brain injuries are caused by accidents, they are very random and difficult to prevent. Safety is the best way to avoid brain injuries that can cause lifelong amnesia. Simply wearing a seatbelt in the car and putting on a helmet when using bikes, skateboards, and other equipment would prevent thousands of serious brain injuries. Unfortunately, not all cases of amnesia are this preventable.

Head Injuries: The Statistics

Every year, three quarters of a million people in the United States spend time in a hospital because of a head injury. Seventy percent of them have posttraumatic amnesia, and 30 percent of these lose some or all of their memory for at least four weeks. The longer amnesia lasts after a head injury, the smaller the chances that the person will recover all of his or her memory.

Amnesia from Disease

Brain damage does not always come from reckless behavior or unfortunate accidents. Sometimes, illness is to blame. Perhaps the best-known and most wicked thief of memory is Alzheimer’s disease. More than 4 million Americans are losing their memories to this illness. Although there are a few cases of Alzheimer’s disease in people younger than sixty years of age, it usually strikes in one’s sixties, seventies, or eighties. It is a disease of the brain’s cells. Proteins begin to clump together in the neurons, and as a result, the cells die. Dead and dying brain cells stick together in clumps, called plaques, and these block important electrical messages from getting around the brain.

When the brain’s cells cannot communicate with each other, the brain loses the ability to do important jobs. Memory is one of the first things to go. People with Alzheimer’s often start to lose their memories even before they know they have the disease. When this memory loss begins to be a problem for daily living, it is called dementia.

“People with dementia may have difficulty learning new things or remembering the names of people they just met,” says Dr. Alberto Maud. “They may get lost in places that were previously very familiar or have trouble finding words.”³¹

The amnesia caused by Alzheimer’s is both retrograde and anteretrograde. Patients forget what they knew, and they also lose the ability to learn anything new. They start to ask the same questions over and over because they forget the answers as soon as they hear them. They slowly start to lose memories of their past, too. A person with Alzheimer’s disease may eventually forget her entire life since childhood, and may therefore begin to believe that she is still a child. Memory loss is such a major part of Alzheimer’s disease that some people think amnesia itself is the disease. It is not—it is only a symptom. But it is usually the first sign that a person has Alzheimer’s, and it certainly is the biggest problem of the disease.

“It is frightening to lose control of your body in any way,” says Alzheimer’s sufferer Thomas DeBaggio in his book, Losing My Mind: An Intimate Look at Life with Alzheimer’s. “It is especially tragic when the body’s central control system, the brain, is the target of an angry destructive process that science has been unable to tame or reclaim. Memories tell us who we are and where we have been. . . . My memories are slowly disappearing.”³²

Doctors have not found a cure for Alzheimer’s. They do not yet know how to prevent it. There are medications that can slow it down, but love and patience are still the best tools people have to help someone who suffers from this kind of progressive and merciless memory loss.

A Sudden Strike on Memory

Amnesia can come on slowly, as it does in Alzheimer’s disease and other illnesses like it. Accidents, on the other hand, happen suddenly, and so does the memory loss they can cause. Traumatic brain injuries and concussions are the result of accidents that happen outside the body, but other types of brain “accidents” happen within the brain itself. These are called cerebrovascular accidents, or CVAs—literally, accidents within the blood vessels of the brain. A simpler word for a CVA is a stroke.

Like every part of the body, the brain depends on blood for oxygen and nutrients. A stroke happens when the blood supply to part of the brain is cut off. A blood vessel might form a clog, called a clot. Blood cannot get past the clot, and when part of the brain goes without oxygen for a while, that part no longer works properly. Without blood and nutrients, cells of the brain die, and often, they take memory with them.

Strokes are a leading cause of brain damage. Many problems are created in the body if the brain cannot send messages to the right places. Some people who have had a major stroke cannot move one of their hands or cannot smile with one side of their mouth. Strokes can also cause loss of memory for past events, as well as the loss of implicit memory for how to do things. People who have had a stroke often struggle to remember the right words for everyday objects such as a pencil or a chair. They may forget how to read or write.

“It is estimated that approximately one third of stroke victims will develop memory problems,” says Maud. “The memory problems can be so severe that they interfere with normal functioning and are then called dementia.”³³

Most strokes are caused by blocked blood vessels. A healthy heart and a healthy cardiovascular system, therefore, are important for prevention throughout life. Lawrence H. Wyatt, writing in the Journal of the American Chiropractic Association, says strokes can happen at any age. “In the United States, strokes are the most common cause of disability and the third most common cause of death in adults,” he says. “Especially prone to stroke are people with unhealthy lifestyles—those who smoke, stick to poor diets, and don’t exercise.”³⁴

The causes of strokes are known, and there are things people can do to prevent them. Education, therefore, might help prevent many cases of stroke-related amnesia. The same is true for another cause of major memory loss: alcoholism.

Memories Lost to Alcohol Abuse

Drinking alcohol affects the brain and the nervous system. A person who has had too much to drink will start to show it. Slurred speech, stumbling, slow reflexes, and poor reasoning skills are signs that alcohol has had some bad effects on the brain. Alcoholic beverages can also cause amnesia. People who have had way too much to drink might even black out, waking up the next day with no idea where they are or how they got there. Such a situation may be scary at the time. With any luck, it will convince the person not to drink so much in the future. Although the memories of that particular night are probably lost forever, the person will move on with no lasting effects on future memory.

Alcohol’s effects on the brain are not always temporary. Alcoholics, people who are addicted to alcohol, can sometimes get permanent amnesia—not just for the events of one evening but for life. The condition is called Wernicke-Korsakoff syndrome or Korsakoff’s psychosis. Over time, heavy use of alcohol can

Where Am I?

In September 2006 Jeff Ingram left his home in Olympia, Washington, to visit family and friends in Canada. He never arrived. Instead, he wound up on the streets of Denver, Colorado, with no idea where he was—or who he was. When he finally found a hospital, he had trouble getting admitted because he could not give them his name.

Ingram was suffering a type of amnesia called dissociative fugue, a total memory blank that usually goes along with wandering far from home. More than a month went by before Ingram finally made his way to a Denver TV station and appeared on the network news to plead for someone to recognize him. Halfway across the country, his fiancée was watching. Ingram went home, but he had no memories of the place. He and his fiancée married, but he had no memories of the years they dated. The cause of his fugue was not known.

The car Ingram was driving when he left Olympia was never found.

affect the body’s ability to use thiamine, also known as vitamin B1. When the brain does not have enough of this important vitamin, the memory process is damaged. Patients who have a long-term history of alcohol abuse, Harvard University psychology professor Daniel L. Schacter says, “show a profound loss of memory for recent experiences.” He adds that “in addition to memory loss, most patients with Korsakoff’s syndrome have cognitive and emotional problems.”³⁵

Korsakoff’s psychosis is a permanent form of amnesia. A person who has this condition often tries to hide memory loss by making up stories for experiences or situations he or she cannot remember. But even for the best storytellers, the damage to the brain has been done, and the memories are lost forever.

Korsakoff’s psychosis gets worse over time, even if the person completely stops drinking. When the body’s ability to use thiamine is lost because of alcohol abuse, this ability cannot be recovered. A memory-erasing chain of events has been set in motion, and there is no way to stop it. Even taking vitamin supplements will not help. Wernicke-Korsakoff syndrome continues to get worse and memories continue to fade until eventually, the syndrome causes death. As with so many other causes of amnesia, there is no cure.

Contagious Culprits

Amnesia is usually brought on by diseases, injuries, or conditions that are not contagious. Alzheimer’s disease does not pass from one person to the next through a cough or a sneeze, and a person will not have a stroke from sharing a straw with a stroke patient. Far more frightening to most people are the causes of amnesia that are contagious. Certain viruses or bacteria can infect the brain and cause brain damage so severe that memories are lost.

Such a brain infection is called encephalitis, meaning “swelling of the brain.” It can happen when bacteria or viruses enter the brain or the spinal cord. Encephalitis can cause a coma, and it is often deadly. A person who recovers from such an infection may have lasting brain damage, including widespread amnesia.

“Permanent amnesia results from destruction of brain tissue,” say Floyd E. Bloom, M. Flint Beal, and David J. Kupfer, authors of The Dana Guide to Brain Health. “Such damage can be caused by a variety of mechanisms, including infection.”³⁶

Quite a few illnesses can lead to encephalitis, and some of the most notorious are carried by insects such as mosquitoes and ticks. Lyme disease and West Nile virus are two examples. Lyme disease is caused by tiny organisms called spirochetes, which are carried by ticks. West Nile virus is carried by mosquitoes. Both insects are parasites that live by sucking the blood of other creatures, including humans. When these pests bite an infected creature, they pick up the virus or bacteria. When next they bite something else, they leave the harmful germs behind. Illnesses such as Lyme disease and West Nile virus can cause serious damage in people, including brain swelling that can destroy memory.

Insects, however, are not the only ones spreading dangerous diseases around. People themselves can pass disease to each other. Common illnesses such as herpes, measles, mumps, and chicken pox can end up in the brain, causing swelling and dangerous damage. Scientists have developed vaccines to prevent many of the illnesses that can be a threat to memory, and fortunately, encephalitis that is serious enough to cause brain damage and amnesia is very rare. When it happens, though, it is life changing.

John E. Douglas, a former agent with the Federal Bureau of Investigation, was helping with a tough case when he came down with viral encephalitis and a fever so high, he says, doctors told his family that “his brain has been fried to a crisp.”³⁷ Douglas was taken to a hospital in the throes of a violent seizure. He spent a week in a coma and had amnesia when he came out of it.

“The recovery was painful and discouraging,” he says. “I had to learn to walk again. I was having memory problems.” When he went home, he explains, “I’d notice a particular building and not know if it was new. I felt like a stroke victim and wondered if I’d ever be able to work again.”³⁸

A Shocking Condition

Douglas’s infection was in his brain, but an infection anywhere in the body that causes a high fever can also cause a seizure, a rise in the electrical activity in the brain. Seizures, in turn, can damage brain cells necessary for memory.

“Things that irritate the brain, particularly those that irritate a particular part of the brain, can cause neurons to fire erratically,”³⁹ says Dr. Carl W. Bazil, author of Living Well with Epilepsy and Other Seizure Disorders. The result is a seizure.

Seizures can be so mild that they are hardly noticeable. The person just seems to be staring into space for a moment. But seizures can also be severe, causing convulsions, or tensing of muscles in the body. Someone who is having a seizure may begin to jerk uncontrollably and clench his jaw. A major seizure can also cause damage to the brain, and as happened for Douglas, memory loss is one of the possible results.

Few illnesses cause a fever high enough to bring on a seizure and brain damage, but some people have a condition called epilepsy and frequently suffer from minor or major seizures at random. Seizures and epilepsy can be triggered by some of the same things that can cause amnesia.

“Epilepsy most often starts at the extremes of life—in the very young or the very old—although it can begin at any age,” says Bazil. “Many things in our lives that affect the brain also have the potential to cause seizures to begin.”⁴⁰

A stroke can cause a seizure, for example, and sometimes, a head injury can bring on epilepsy. The famous amnesia patient known as HM, in fact, had surgery on his brain for exactly this reason. When he was nine years old, he suffered a head injury that caused epilepsy. His brain surgery, at age twenty-seven, was supposed to help with the seizures. Unfortunately, it also wiped out his memory, something the seizures themselves had never done.

Solving the Brain’s Mysteries

Many of the things that go wrong in the brain that result in brain damage and amnesia are still widely considered to be medical puzzles. However, scientists have been busy developing new technology to study living brains, technology that can create detailed pictures of exactly what is happening in the brain and when. This technology may be the key to preventing some of the causes of amnesia. It may even help doctors to repair brain damage, restore some patients’ ability to learn new things again, and perhaps even find the memories that some amnesia patients think are gone forever.