Dementia versus Pseudodementia

Dementia Overview


Alzheimer’s Disease. Bilateral decreased parietal and temporal lobe activity. Top-down surface view
Alzheimer’s Disease. Bilateral decreased parietal and temporal lobe activity. underside surface view
 

As the population ages, the incidence of dementia in the U.S. will become an even more common problem and take up an even larger percentage of the health care budget. With the advent of new medications that slow the course of some dementing processes, diagnostic tools that help in the early differential diagnosis of dementia is essential. The SPECT pattern for Alzheimer’s Disease is typically bilateral hypoperfusion in the parietal and temporal regions of the brain with frontal lobe hypoperfusion occurring later in the illness. Multi-infarct dementia is characterized by multiple areas of decreased perfusion. HIV dementia is typically seen by decreased patchy uptake across the cortex. Frontal lobe dementias (as the name indicates) are often characterized by very poor frontal lobe perfusion. Psuedodementia (another condition, such as depression, that clinically appears like dementia) will not have a typical dementia pattern and may be more like a depression pattern.

Here are several examples of how SPECT can be useful in the evaluation and treatment of dementia-like presentations.

 
Frontal Temporal Lobe Dementia (Baseline Surface)
 

When Frank, a wealthy, well-educated man, entered his seventies, he began to grow forgetful. At first it was over small things, but as time went on the lapses of memory progressed to the point where he often forgot essential facts of his life: where he lived, his wife’s name and even his own name. His wife and children, not understanding the change in behavior, were aggravated with his absent-mindedness and often angry at him for it. Frank’s SPECT study showed a marked suppression across the entire brain, but especially in the frontal lobes, the parietal lobes and temporal lobes. This was a classic Alzheimer’s disease pattern. By showing the family these images and pointing out the physiological cause of Frank’s forgetfulness, in living images, I helped them understand that he was not trying to be annoying, but had a serious medical problem.

Consequently, instead of blaming him for his memory lapses, they began to show compassion towards him, and they developed strategies to deal more effectively with the problems of living with a person who has Alzheimer’s Disease. In addition, I placed Frank on new experimental treatments for Alzheimer’s Disease that seemed to slow the progression of the illness.

 

Alzheimer’s Disease


top-down surface view. Notice marked overall suppression, especially in the parietal lobes (arrows left images) and temporal lobes (arrows right image)
underside surface view.Notice marked overall suppression, especially in the parietal lobes (arrows left images) and temporal lobes (arrows right image)
 
Pseudodementia good temporal and parietal lobe perfusion, with increased limbic and/or decreased prefrontal cortex activity.underside active view before treatment
Pseudodementia good temporal and parietal lobe perfusion, with increased limbic and/or decreased prefrontal cortex activity. underside active view after treatment
 

Here is a scan of a 92 year old man with Alzheimer’s Disease who had become forgetful, frequently lost away from home, forgot how to do simple things such as dress himself and began getting aggressive with his wife. Notice the extensive frontal lobe involvement.

Before treatment notice good overall activity, with increased limbic system activity (center arrow), after treatment with Wellbutrin the limbic system normalizes.

I first met Margaret when she was 68 years old. Her appearance was ragged and unkempt. She lived alone and her family was worried because she appeared to have symptoms of serious dementia. They finally admitted her to the psychiatric hospital where I worked after she nearly burned the house down by leaving a stove burner on. When I consulted with the family I also found out that Margaret often forgot the names of her own children and frequently got lost when driving her car. Her driving habits deteriorated to the point where the Department of Motor Vehicles (DMV) had to take away her license after four minor accidents in a six month period. At the time when Margaret’s family saw me, some members had had enough and were ready to put her into a supervised living situation. Some family members, however, were against the idea and wanted her hospitalized for further evaluation.

While at first glance it may have appeared that Margaret was suffering from Alzheimer’s Disease, the results of her SPECT study showed full activity in her frontal, parietal and temporal lobes. If she had Alzheimer’s Disease, there should have been evidence of decreased blood flow in those areas. Instead, the only abnormal activity shown on Margaret’s SPECT was in the limbic system at the center of the brain where the activity was increased. Often, this is a finding in people suffering from depression. Sometimes in the elderly it can be difficult to distinguish between Alzheimer’s Disease and depression because the symptoms can be similar. Yet with pseudodementia (depression masquerading as dementia), a person may appear demented, yet not be at all. This is an important distinction to make because a diagnosis of Alzheimer’s Disease would lead to prescribing a set of coping strategies to the family and possibly new experimental medications, whereas a diagnosis of some form of depression would lead to prescribing an aggressive treatment of antidepressant medication for the patient along with psychother-apy.

Here is another example.

 
underside active view before treatment
underside active view after treatment
 

Before treatment notice poor prefrontal cortex activity and increased limbic system activity, after treatment with imipramine the limbic system normalizes and the prefrontal cortex improves significantly.