Reversible Dementias

Dementia is generally caused by damage to or disruptions of brain cells, particularly in the cerebral cortex (the part of the brain which controls memory, perception, consciousness, and language). In some cases, this damage or disruption isn't permanent, causing reversible dementia conditions that can be slowed or cured with proper treatment.


Especially in the older population, infections and fevers can cause delirium, a state of extreme disorientation that is often confused with dementia because it shows many of the same symptoms. Delirium is noticeably more abrupt and sudden than dementia and can worsen or improve drastically in a matter of days or hours. Delirium is not caused by gradual damage to the brain but rather by external factors like infections (UTIs or influenza), withdrawal, strokes, or adverse reactions to medications.

Normal Pressure Hydrocephalus

Normal Pressure Hydrocephalus is a form of dementia caused by a build-up of excess cerebrospinal fluid in the ventricles of the brain. This fluid buildup causes ventricles to expand, damaging surrounding brain tissue and leading to difficulty walking, disrupted gait, and loss of bladder control, along with symptoms common to dementia like memory loss and cognitive impairment. Hydrocephalus can be reversed and treated by draining the excess fluid from the brain through the surgical implantation of a shunt.

Cerebrovascular Disease, Alzheimer's Disease, hypertension, and vascular disorders can increase the risk of developing normal pressure hydrocephalus, though the concrete cause of cerebrospinal fluid buildup hasn't yet been identified.

Wernicke-Korsakoff Syndrome

Wernicke-Korsakoff Syndrome is a type of dementia caused by chronic, long-term alcoholism which leads to thiamine (vitamin B1) deficiencies. Thiamine works to help brain cells convert sugar to energy, so as thiamine levels decrease the brain becomes unable to generate energy for proper functioning. It's unclear why alcoholism leads to thiamine deficiency only in some alcoholics, though research suggests that poor nutrition could contribute to risk.

Wernicke-Korsakoff syndrome is only partially reversible - though abstinence can restore memory and cognitive functioning to some extent, the condition causes permanent damage to the brain that cannot be reversed even upon discontinuing alcohol use.

Vitamin B12 Deficiency

Vitamin B12 assists in the production of red blood cells which transport oxygen to the brain, so impaired absorption of vitamin B12 or a vitamin B12 deficiency can lead to dementia caused by pernicious anemia. Symptoms of pernicious anemia include fatigue, yellowed skin, pica, and shortness of breath along with dementia symptoms like confusion and difficulty concentrating. Usually, pernicious anemia isn't caused by dietary issues or a lack of vitamin B in the diet but rather by an inability to properly absorb and retain the vitamin.

Pernicious anemia is sometimes passed down genetically, through it more frequently results from atrophic gastritis (weakened stomach lining) or autoimmune conditions. Vitamin B12 supplements or injections can reverse pernicious anemia, eliminating the dementia symptoms that accompany it. However, pernicious anemia is not completely curable, so medications must be taken consistently to prevent the onset of dementia symptoms.

Subdural Hematomas

Subdural hematomas, or blood clots in the brain, are caused by bruising from severe head trauma, most commonly from trauma received in vehicle accidents. In the older population, blood clots can occur even as a result of very minor head injuries which may be unnoticed or forgotten. Hematomas can cause dementia and mimic symptoms of Alzheimer's disease, though quickly treating and removing the blood clot can eliminate symptoms and restore brain function.

Thyroid Disease

When the thyroid gland doesn't produce enough thyroid hormones (or overproduces thyroid hormones) overall body functioning decreases, possibly leading to dementia. Thyroid-related dementia affects females up to five times as often as it affects males. Thyroid supplements can fully restore functioning and eliminate dementia symptoms, but life-long treatment and consistent medication is needed to manage thyroid disease.


Though it's uncommon, tumors and cancers in certain parts of the brain can damage surrounding tissues and cause dementia. Tumor-related dementia will usually be accompanied by symptoms like headaches, vomiting, intracranial pressure, or rapid personality changes. Treating or removing these tumors will cause dementia symptoms to significantly reduce or disappear.

Toxic Reactions to Drugs or Chemicals

Certain medications or interactions between medications, along with types of poisoning like carbon monoxide, mercury, lead, or other heavy metal poisoning can lead to dementia symptoms which will diminish once exposure to the chemicals or medications ceases.

Heavy drug use and alcoholism (especially alcohol poisoning) can also lead to dementia symptoms that may decrease after the substance abuse is stopped. However, with serious or long-term substance abuse permanent damage may occur, resulting in a condition known as substance-induced persisting dementia.

Irreversible Dementias

Alzheimer's Disease

Alzheimer's Disease is the leading cause of dementia and results from the death of cells in the cerebral cortex, the area of the brain responsible for memory and cognition. Abnormal proteins, hypothesized to be beta amyloids, form lesions that build up in the cerebral cortex until they disrupt and destroy surrounding cells.

Beta amyloids and brain lesions are present without serious effects in most aging brains, but in those suffering from Alzheimer's lesions are significantly more populous and build up in regions that control cognition and memory. It can take 10 to 20 years of beta amyloid buildup to begin displaying symptoms of Alzheimer's, and the continual buildup of the proteins means that the disease progresses and worsens with age.

Age is the most influential risk factor for the development of Alzheimer's - 10% of Americans aged 65 and older have Alzheimer's disease, but this proportion rises to over 30% for Americans aged 85 or older. Genetic susceptibility is also a significant risk factor for developing Alzheimer's: those with a close family member suffering from Alzheimer's are up to three times more likely to develop the condition than the general population.

Vascular Dementia

Atherosclerosis, or the buildup of fatty deposits on the walls of brain arteries, can cause decreased blood flow to certain parts of the brain. If this restriction of blood flow is serious enough to deprive the brain of oxygen, areas of dead tissue form and eventually result in Vascular Dementia. Each individual incidence of blocked blood flow and atherosclerosis usually goes unnoticed, but a buildup of damage over time begins to cause slurred speech, decreased cognitive abilities, confusion, and other symptoms of dementia.

Vascular Dementia usually develops in those with a previous history of cardiovascular conditions, especially diabetes, heart disease, high blood pressure, and high cholesterol. Vascular Dementia accounts for over 20% of dementia cases, making it the second most common cause of dementia after Alzheimer's Disease.

Parkinson's Disease

The concrete cause of Parkinson's Disease has not yet been identified, though researchers attribute Parkinson's to the death of nerve cells in the substantia nigra region of the brain. The destroyed nerve cells usually produce dopamine that assists in sending messages to the region of the brain responsible for movement. Decreases in dopamine production inhibit the brain's ability to send these messages and lead to the stiffness, tremors, and impaired coordination found in those with Parkinson's Disease.

Those suffering from Parkinson's Disease have small deposits of alpha-synuclein proteins in the brain that build up to form lewy bodies. As Parkinson's Disease worsens and progresses, these lewy bodies spread from areas of the brain which affect movement to areas which play a role in memory and cognition, causing dementia.

Research estimates that 50-80% of Parkinson's sufferers will develop dementia. Some incidences of Parkinson's are inherited or linked to exposure to certain toxins (beta-HCH and MPTP), but the cause of the vast majority of cases is still unknown.

Lewy-Body Dementia

Lewy bodies are small, circular deposits of alpha-synuclein proteins that build up in brain cells and are frequently found in Parkinson's sufferers. It's unknown exactly how Lewy bodies affect brain functioning and cause dementia, but researchers hypothesize that the bodies interfere with the functioning of dopamine and acetylcholine, messenger chemicals responsible for regulating memory, mood, learning, and cognition. Lewy-Body Dementia is usually found in those with no family history of the condition, and the concrete causes of LBD are still unclear.

Huntington's Disease

The cause of Huntington's Disease is genetic - Huntington's is characterized by a mutation on the fourth chromosome that results in the death of nerve cells in the basal ganglia area of the brain. Children of parents with Huntington's Disease have a 50% chance of inheriting the mutated fourth chromosome, and those that inherit the gene have a 100% chance of developing Huntington's Disease.

Infectious Dementias

Creutzfeld-Jakobs Disease

Creutzfeldt-Jakob Disease is caused by the introduction of improperly folded proteins into the brain. These proteins trigger reactions in other proteins in the brain, causing them to misfold in a chain reaction. These misfolded proteins will then clump together, causing damage to surrounding cells.

The most well known type of CJD is variant CJD (vCDJ), also known as "mad cow disease", in which beef infected by bovine spongiform encephalopathy (misfolded proteins) is ingested and introduced into the system. Misfolded proteins can also be introduced through surgically implanted corneas, brain grafts, or improperly sterilized electrode implants. CJD is one of the only types of dementia that occurs in those with little or no known dementia risk factors, though about 10% of CJD cases are hereditary.

AIDS-induced Dementia

Dementia sometimes occurs in those suffering from AIDS, as the human immunodeficiency virus can damage parts of the brain responsible for memory, concentration, and communication. However, AIDS-induced Dementia is rare as modern medical practice has found ways to manage the human immunodeficiency virus in order to keep it from damaging body systems and leading to dementia.


Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum and spread through direct contact with syphilis sores. Neurosyphilis can develop if syphilis goes untreated long enough for the infection to reach the spinal cord and brain. Syphilis is easy to treat and prevent, and it can take 10-20 years for syphilis to progress into neurosyphilis. Only 25-40% of untreated syphilis cases develop into neurosyphilis, but if the Treponema pallidum bacteria infects the brain or spinal cord it can cause dementia symptoms which mimic Alzheimer's disease.