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year-old man with mild memory loss who shows the typical MRI and SPECT/PET abnormalities is
likely to be developing Alzheimer's disease.

Lumbar Puncture

A lumbar puncture is needed to examine the cerebrospinal fluid that bathes the brain and spinal cord.
Studies conducted mainly in Sweden, plus smaller American studies, show high levels of
cerebrospinal fluid tau protein (forms part of the neurofibrillary tangles) and low levels of A-Beta
amyloid protein (forms part of the amyloid plaque) in Alzheimer's patients compared to normal
elderly control subjects. However, high levels of tau are also found in other neurologic conditions, so
its diagnostic utility for Alzheimer's remains uncertain.

A few other diagnostic tests— a simple eye test, Alz-50 protein, and the AD7Nc protein— were
hyped up initially but fell by the wayside after subsequent research failed to replicate the original
results.

Genetic Markers

Nearly half the patients with Alzheimer's disease have a family history of dementia. Allen Roses,
formerly the head of the Alzheimer's Center at Duke University and currently a division chief at the
drug company Glaxo-Wellcome, is the main proponent of using the apolipoprotein E e4 genotype on
chromosome 19 as an early diagnostic marker of Alzheimer's disease. However, not everyone with
this type of gene gets Alzheimer's disease, and some people who do not have this gene can still get
the disease. Also, there are big differences among whites, African-Americans, and Hispanics in the
risks associated with this gene. Expert consensus panels have concluded that apolipoprotein E
genotyping should not be used for clinical diagnosis.

Scientists have identified abnormal genes for a few rare forms of Alzheimer's disease. Patients
with abnormal presenilin 1 and presenilin 2 genes tend to develop Alzheimer's disease at a relatively
young age: forty to sixty years. There is one large family pedigree of Volga Germans, now spread
across the world, who provided the genetic material that helped identify one of these genetic
mutations. But even in patients with early-onset disease, it is difficult to identify the presenilin 1 and
2 mutations because several dozen variations of each of these two main mutations have been
identified, and there probably are many more waiting to be discovered. Therefore, complex
laboratory techniques in specialized centers are necessary, and many