Evaluating Dementia: Assessment for Treatable Causes

"Dementia" means an acquired, persisting decrease in mental functioning. Dementia is not a disease or a final diagnosis; instead, it refers to a category of symptoms that can be the result of a diverse group of conditions and diseases.

Everyone with eyes and a brain of their own knows that dementia is a very common and serious problem, robbing some people of their memories, ability to function independently and even their personalities. As a community-based neurologist, I see all too many cases of dementia, but the part that worries me the most is when patients, family members and even medical personnel assume that nothing can be done and don't even bother to evaluate for underlying causes.

Although it is certainly true that modern medicine lacks effective treatments for many causes of dementia, it's also true that still others can be cured or favorably modified. It would be a shame to assume that a case was untreatable and thereby miss something that could have been cured or better managed.

So how do dementia specialists or other doctors investigate cases of dementia? The medical detective-work begins with a thorough history and physical examination.

Clues might come from the history of the patient's other medical problems, the medication list, use of alcohol or other drugs, or from other physical problems that developed concurrently with the dementia. Apart from the general physical exam, the doctor also explores the patient's ability to pay attention, remember, calculate, draw pictures, reason, comprehend words and express himself or herself. Further neurological examination assesses other aspects of brain function like vision, hearing, strength, coordination, sensation, walking and reflexes.

After compiling the results of the history and examination, the physician can usually judge the relative likelihoods of different underlying causes for the dementia, but follows up these clinical judgments with additional medical tests to nail down the most likely cause. The irreducible minimum of additional testing includes a brain scan--either a CT or an MRI--plus a panel of blood tests.

The brain scan might detect a brain tumor, previously unsuspected strokes, clotted blood compressing the brain or hydrocephalus (water on the brain) all of which can cause dementia and which can also be treated. The blood tests look for salt-and-water imbalances, abnormal blood-sugar levels, kidney impairment, liver impairment, excessive calcium levels, thyroid disease, and deficiencies of vitamin B12 and folic acid. Each of these problems, if found, would warrant specific treatments.

Other tests can be applied depending on the physician's judgment of their usefulness in individual cases. These might include an electroencephalogram (brain-wave test), lumbar puncture (spinal tap) or a PET (positron emission tomographic) scan, which is a newer technique that shows the relative activity of brain cells in different parts of the brain. Additional blood-tests can screen for infections with human immunodeficiency virus (HIV) or the bacteria associated with Lyme disease or syphilis.

After all is said and done, what turns up? Unfortunately, about half the dementia cases evaluated in this way lead to a diagnosis of Alzheimer's disease or similar degenerative brain disease for which there is no cure. Although treatments exist for these degenerative dementias, their benefits are modest.

It's the other half of the cases which reveal an interesting grab-bag of different underlying causes and, for that matter, treatments.

Neurosurgery can be indicated for dementias caused by brain tumors, especially meningiomas which are slow-growing tumors that respond poorly to chemotherapy or radiation therapy, but can be totally removed in surgical operations. Meningiomas are not cancerous, but because space inside the skull is limited, they cause trouble by crowding the brain. Subdural hematomas and epidural hematomas are two other space-occupying abnormalities that crowd the brain. These are masses of clotted blood usually caused by traumatic blows to the head. The injuries producing the bleeding are not always remembered or, if remembered, might have been dismissed as trivial at the time they occurred. These, too, can be totally removed by a neurosurgeon.

Normal pressure hydrocephalus is another cause of dementia responding to neurosurgery, but in this condition the surgeon doesn't remove a mass-lesion. Instead, the surgeon places a tube inside one of the brain's swollen fluid-chambers known as ventricles, allowing the excessive fluid-accumulation to drain away through the tube and into another body-space where it causes no harm. Normal pressure hydrocephalus can be identified not only by its dementia and enlarged ventricles, but by the concurrent presence of a prominent walking impairment as well as urinary incontinence.

Non-surgical treatments can be helpful for other causes of dementia. Two conditions involving a deficiency or shortage of a biochemical are hypothyroidism and vitamin B12 deficiency. Finding one of these is a blessing in disguise because they are easily fixed. In hypothyroidism, the thyroid gland in the neck secretes too little thyroid hormone. This is managed by making up for the shortfall in pill form. In vitamin B12 deficiency, the problem is that this essential vitamin is not properly absorbed into the bloodstream via the gastrointestinal tract, so the deficiency is treated by periodic injections of vitamin B12.

As people get older and acquire more medical problems, their list of medications often grows longer. One or more of the medications they take might interfere with mental functioning. Common offenders are medications for urinary incontinence, anxiety or insomnia. If a problem-medication is eliminated, or replaced with another drug, the patient's mental prowess can improve.

Depression is a common cause of dementia in which the mood disorder itself interferes with concentration, memory and other mental performance. In many cases the mental impairments are more prominent than the mood disturbance, causing it to be overlooked. Depression is treated with medication, psychotherapy, or both.

Chronic infections with the Lyme and syphilis bacteria can be resolved with appropriate antibiotics. Occasionally a fungal infection is to blame, and can also be treated with specific medication. Treatments for HIV are less good, but this disease still needs to be identified in order to obtain the best possible outcome.

Chronic alcohol abuse can damage the brain and cause dementia. In most cases the previously caused damage cannot be undone, but further damage can be prevented through treatment of the alcoholism. Wernicke's encephalopathy is an alcohol-associated cause of confusion for which injections of thiamine (vitamin B1) are urgently needed.

Strokes can also produce dementia. Strokes are caused by disrupted circulation which damages parts of the brain. In most cases, the patient and family were aware of strokes when they occurred, but in other cases one or more strokes might have gone undetected at the time they occurred. Prior strokes cannot be undone, but recognition of the presence of strokes can lead to preventive measures to decrease the likelihood of future strokes.

Apart from the conditions and diseases already mentioned, the list of potential causes of dementia is longer still. In brief, not every cause of dementia can be cured or significantly improved, but without a thoughtful, thorough, medical evaluation the ones that can be treated could easily go undetected.

(C) 2005 by Gary Cordingley