ScienceDaily (Apr. 17, 2007) — People who develop dementia or Alzheimer's disease experience brain structure changes years before any signs of memory loss begin, according to a study published in the April 17, 2007, issue of Neurology®, the scientific journal of the American Academy of Neurology. Researchers say these findings may help identify people at risk of developing mild cognitive impairment (MCI), which leads to Alzheimer's disease.
Researchers performed brain scans and cognitive tests on 136 people over the age of 65 who were considered cognitively normal at the beginning of the five-year study. Participants were then followed annually with neurologic examination and extensive mental status testing. By the end of the study, 23 people had developed MCI, and nine of the 23 went on to be diagnosed with Alzheimer's disease. The brain scans of the 23 people with memory loss were then compared to the 113 people who remained cognitively normal.
Alzheimer's Brain
There are three brain abnormalities that are the hallmarks of the Alzheimer's disease process:
- Plaques. A protein called beta-amyloid accumulates and forms sticky clumps of amyloid plaque between nerve cells (neurons). High levels of beta amyloid as associated with reduced levels of the neurotransmitter acetylcholine. (Neurotransmitters are chemical messengers in the brain.) Acetylcholine is part of the cholinergic system, which is essential for memory and learning and is progressively destroyed in Alzheimer?s disease.
- Tangles. Neurofibrillary tangles are the damaged remains of macrotubules, the support structure that allows the flow of nutrients through the neurons. A key feature of these tangled fibers is an abnormal form of the tau protein, which in its normal version helps maintain healthy neurons.
- Loss of nerve cell connections. The tangles and plaques cause neurons to lose their connection to one another and die off. As the neurons die, brain tissue shrinks (atrophies).
Compared to the group that didn't develop memory problems, the 23 people who developed MCI or Alzheimer's disease had less gray matter in key memory processing areas of their brains even at the beginning of the study when they were cognitively normal.
"We found that changes in brain structure are present in clinically normal people an average of four years before MCI diagnosis," said study author Charles D. Smith, MD, with the University of Kentucky Medical Center in Lexington and member of the American Academy of Neurology. "We knew that people with MCI or Alzheimer's disease had less brain volume, but before now we didn't know if these brain structure changes existed, and to what degree, before memory loss begins."
In addition, the study found those people destined to develop MCI had lower cognitive test scores at the beginning of the study compared to the group that didn't develop memory problems, even though these scores were still within normal range.
"These findings of structural changes in cognitively normal people before memory loss begins aren't surprising given Alzheimer's disease may be present for many years before symptoms of the disease begin to appear," said Smith.
The study was supported by grants from the National Institute of Neurological Disorders and Stroke and the National Institute on Aging Alzheimer's Disease Centers Program (ADCs).
Dementia Brain:
Initial Assessment of Memory and Function
A worrying tendency to forget recent events, appointments, bills and other things that need attention often motivates the patient or caring relation to seek for a medical opinion. Whether or not the patient’s or carer’s worries are justified can usually be assessed without recourse to formal testing procedures, especially if there is a reliable informant and/or the physician is familiar with the patient’s clinical history and general situation.
Assessment of the problem generally begins with a patient interview to establish the present level of cognitive functioning and the extent of change from prior functioning. The interview is preferably conducted in the presence of a partner, close relative or another reliable informant. This preliminary interview will generally assess the present levels of memory, language ability and executive function. Impaired memory may be evident in how the patient responds to quite simple questions, in searching for words to express him or herself, or in direct complaints. For example, individuals with impaired memory may not recall recent events, forget that food is cooking or misplace items such as keys, spectacles or money.
When the patient answers questions, it is important to note whether the ‘head turning sign’ is present. A person with cognitive impairment will often turn their head to their spouse/caregiver to have them provide answers. This person is often critical in the assessment, as patients may lack insight and their responses will often require verification. Perhaps more importantly, the observer may give a more reliable assessment of changes in functional abilities.
No comments:
Post a Comment