Causes of Reversible Dementia

When you think of dementia, you probably picture the vacant, blank face of an Alzheimer’s patient. Alzheimer’s disease is the most common form of dementia, but it’s certainly not the only one. There are other types of dementia, some of which are reversible with proper treatment. What are the most common causes of reversible dementia?

The Importance of Diagnosing Reversible Dementia

When an older patient is suspected of having Alzheimer’s disease, a doctor runs a battery of tests including blood tests, imaging studies of the head, and neuropsychological testing – not only to make the diagnosis, but to exclude reversible dementia causes that might respond to therapy. Only about ten percent of dementia cases are due to conditions that can be treated, but it’s important to rule them out. What could be sadder than not treating a person with reversible dementia before it’s too late?

Type of Dementia: Irreversible vs. Reversible Dementia

Alzheimer’s disease accounts for almost 60% of all dementia cases – and it’s a condition that’s progressive and irreversible, although the progression can be slowed somewhat with medications.

Another common cause of dementia is vascular disease, which comes from conditions that reduce blood flow to the brain such as small strokes or “hardening of the arteries”. Vascular dementia isn’t really reversible once the damage is done, but treating the underlying cause such as heart problems, diabetes, or high blood pressure can prevent further progression.

Certain neurological diseases can cause dementia too. These are usually progressive and not reversible. A good example is the later stages of Parkinson’s disease. Two others are Huntington’s disease, which is usually inherited, and Pick disease, a rare degenerative condition that affects the brain.

Causes of Reversible Dementia

An older person who experiences memory loss and cognitive function may do so after falling and hitting their head – causing bleeding to occur in the brain. This can lead to brain swelling that compresses brain tissue and leads to symptoms of dementia. In some cases, family members may not even be aware the person has fallen. This condition can usually be diagnosed using head imaging studies.

Another type of reversible dementia comes from a deficiency in B12, a vitamin which is critical for normal brain and nerve function. It’s not uncommon for older people to be deficient in vitamin B12 due to problems with B12 absorption. Blood testing is usually used to rule out this cause of dementia.

Certain infections that may have been present for many years can be causes of reversible dementia. These include fungal infections that affect the brain, HIV, and long-term syphilis. Encephalitis or meningitis can also cause a form of reversible dementia.

Other causes? Hypothyroidism, or an under-active thyroid, can cause symptoms that mimic dementia and are reversible once the person gets on thyroid hormone replacement. Chronic alcoholism and depression can cause reversible dementia symptoms in older people too. Some drugs and exposure to toxins cause a decrease in cognitive function and memory – and any type of long-term chronic illness can cause systemic changes that affect brain function.

Another, not uncommon, cause of reversible dementia is a condition called normal pressure hydrocephalus – where pressure rises inside the brain and compresses on brain structures that control memory and thinking. This happens when something blocks the free flow of cerebrospinal fluid through the brain and spinal cord. People with this condition usually improve when a shunt is placed to drain the excess cerebrospinal fluid that’s putting pressure on the brain.

Type of Dementia: The Bottom Line?

Alzheimer’s disease is the most common dementia, but not all dementias are irreversible. Every patient with memory or cognitive changes needs a thorough work-up – to look for reversible dementia causes.

References:

N Engl J Med 1996; 335:330-336
Merck Manual. Eighteen edition. 2006.
American Family Physician website. “Initial Evaluation of the Patient with Suspected Dementia”