Possible Screening Tests for Alzheimer’s Disease- Part XIII
As the incidence of Alzheimer’s disease creeps past 4 million the search continues, not only for drug interventions, but also for early indicators of the disease. The general theory being, the earlier the disease can be identified, the greater the chance for modifying progress of the disease. Technological advances (PET, SPECT, fMRI etc.) in screening for possible brain changes associated with Alzheimer’s disease seem to be within our grasp. (Changes in entorhinal area of brain may foretell the start of cognitive loss).
The screenings are very costly, and may not pick up the disease until it is at a level that would make it unlikely for treatment success. What is needed is an easy to use and inexpensive way of screening people at risk for, developing Alzheimer’s disease, the same way Pap smears are used for cervical cancer.
Stephen Curran and John Wattis have proposed using a psychomotor test, Critical Flicker Fusion Threshold Test, as a potential marker for developing Alzheimer’s disease. This "test" meets many needs including the fact that it is not age related, does not require reading, is portable, inexpensive to administer and it does not require a high level of training to administer. Curran and Wattis feel it measure cognitive changes over time.
Relative data exists on a population that has not experienced cognitive loss. Using normal controls, they had 26 individuals with Alzheimer’s disease, from eight Residential Homes, undergo the Critical Flicker Fusion Threshold Test, both in ascending and descending order.
A flickering light has a direct influence on cortical activity as measured by EEG. Recording of EEG indicates that changes have occurred in the occipital area of the brain. They are synchronous with the frequency of retinal stimulation. Asking individuals to press a button when they notice a change in a flickering light (descending) and when they notice the light starting to flicker (ascending) was used as a basis of trying to distinguish normal from Alzheimer’s diseased individuals. They found:
Critical Flicker Fusion Threshold and descending thresholds were significantly lower in patients with Alzheimer’s disease compared with normal controls, but ascending thresholds were not significantly different in the two groups. In addition, in the patient group, ascending thresholds were also significantly higher than descending thresholds and this latter finding is a reversal of the situation seen in normal elderly subjects; thus might be a characteristic feature of Alzheimer’s disease. (Curran and Wattis, 2000)
If this experiment can be duplicated in a controlled, double-blinded prospective study, this may become a way of enabling the treating physician to institute pharmacotherapies early in the course of the illness before damage to neurons are too advanced to reverse the process of cognitive decline. The search continues.
Reference: Curran S. & Wattis J. Critical Flicker Fusion Threshold: A Potential Useful Measure for the early Detection of AD. Human Psychopharmacology Clinical And Experimental 2000; 15:103-112.
A new compund that sets the brain aglow for Alzheimer's disease is being tested at the University of Pittsburgh where researchers have spent more than 12-years concocting the substance. Doctors administer the compound to patients intravenously and then place them under a PET scanner to record detailed brain images.The compound acts as a dye but passes safely from the bloodstream into the brain. Once in the brain, it attaches onto tiny fibrils of plaque, while at the same time avoiding attaching to normal tissues.
In the test that was done under the leadership of William E. Klunk, associate professor of psychiatry at the University of Pittsburgh, the front and temporal lobes of 9 patients glowed with neon-red mounds of plaque. The 5 healthy people who were used in the study showed no such glow. Further testing is needed for the compound with a time frame of 5-years being thought of as the earliest time frame for which the compound and procedure could be approved.
See: Alzheimer's Disease Part I-Medications
for Alzheimer's.
See: Alzheimer’s Disease
Part II- Selegiline and AD.
See: Alzheimer's Disease Part III- Use of Gingko Biloba in memory problems of
Alzheimer patients.
See: Alzheimer's Disease PartIV-Alternative
Treatment.
See: Alzheimer's Disease Part V-Possible
New Drugs for Alzheimer's Disease Treatment.
See: Alzheimer's Part VI -Early
Diagnosis.
See: Alzheimer's Part VII -New
Medication-Metrifonate
See: Alzheimer's Part VIII-Implications
of Longer Life Expectancies
See: Alzheimer's Part IX-Ethical Care
Principles
See: Alzheimer's Disease Part X-Estrogen
and Alzheimer's Disease
See: Alzheimer's Disease Part XI-Pocket
Smell Test
See: Alzheimer's Disease Part XII-MAO-B
See: Alzheimer's Disease Part XIV-Donepezil
See: Alzheimer's Disease Part XV-Cerebrolysin
See: Alzheimer's Disease Part XVI-MCI
See: Alzheimer's Disease Part XVII-Summary
See: Alzheimer's Disease Part XVIII-NO
Releasing NSAIDs
See: Alzheimer's Disease Part XIX-Vitamin
E
See: Alzheimer's Disease-Part XX-Clinical
Trials
See: Alzheimer's Disease Part XXI-The
Brain
See Dementia with Lewy Bodies- Part
XXII-by Gourete Broderick
See: Alzheimer's Disease-Part XXIII-HMG
See: Alzheimer's Disease-Part XXIV-A
Prequel
See: Alzheimer's Disease-Part XXV-Psychosis
See: Alzheimer's Disease-Part XXVI-Amyloid-beta
Hypothesis Controversy
See: Alzheimer's Disease-Part XXVII-
AD and Diabetes
See: Alzhemeir's Disease-Part XXVIII
- Insulin and AD
FOR AN INFORMATIVE AND PERSONAL ARTICLE ON PRACTICAL SUGGESTIONS WHEN SELECTING A NURSING HOME SEE OUR ARTICLE "HOW TO SELECT A NURSING HOME"
Harold Rubin, MS, ABD, CRC, Guest Lecturer
updated July 23, 2002
http://www.therubins.com
email: hrubin12@nyc.rr.com or rubin@brainlink.com