Atrophy of brain tissue is defined as progressive loss of
neurons and their connections
Atrophy occurs naturally in an aging brain, with the total
brain volume diminishing at a rate of 0.2-0.4% per year, but in Alzheimer’s
disease the rate of atrophy can surpass a reduction in mass of 10% each year
The medial temporal lobe is one of the first places with
amyloid and tangle deposits. The rate of atrophy of the entorhinal cortex and
hippocampus of the medial temporal lobe is particularly fast during early
Alzheimer’s disease, with these structures often degrading before symptoms are
fully noticed and identified.
As the disease progresses to become more severe, atrophy is
mainly noticed in the inferolateral temporal lobe. The parietal and frontal
lobes become myelinated last during brain development and remain slightly under
myelinated compared to the other brain structures. It is suggested that the
weakening of this protective layer leaves the lobes sensitive to degeneration by Alzheimer’s disease.
Degradation of the frontal lobe comes as the disease enters moderately severe
and at this stage the hippocampus and entorhinal cortex is likely to have
reduced in volume by 20-25%.
Parts of the lateral ventricles lie in close proximity to
these medial temporal lobe structures and the ventricles undergo
ventriculomegaly, due to the atrophy of their surroundings. The enlargement of
the third and lateral ventricles can be seen by brain magnetic resonance
imaging. The rate of enlargement of the ventricles occurs parallel with the
worsening of results from cognitive tests cognitive (as assessed by Mini-Mental
State Examination MMSE)carried out on the patient. Remarkably degradation of
the medial temporal lobe does not correlate as strongly with the decrease in
cognitive function. of the Alzheimer’s disease patient.
Another gross anatomy change that occurs in Alzheimer’s
disease is the shrinking and narrowing of the gyri of the brain, and a widening
of the sulci.
The size of gyri are found to decrease as Alzheimer’s
disease worsens and MMSE results in relation to cognitive functioning decreased
as the gyri narrow further.
The width of most cerebral sulci (other than the
intra-parietal sulci) are found to widen with the onset of Alzheimer’s disease
and there is a noted pattern of an increase in non- intra parietal sulci as the
MMSE score for cognitive functioning decreases as the disease becomes more
It is suggested that magnetic resonance imaging could be
used to identify narrowing gyri and widening sulci in an effort to recognise
Alzheimer’s disease earlier in the future.
In the case study provided the patient received a clinical
diagnosis of CBD- Corticobasal Degeneration. CBD is known as a Parkinson’s Plus
Syndrome, in which movement, speech, memory and swallowing abilities gradually
CBD is distinctively different to Parkinson’s disease as the
substantia nigra pigmentation of the brainstem degrades in Parkinson’s disease,
whereas in this case study the pigmentation is preserved and the patient goes
on to develop classical symptoms of Alzheimer’s disease alongside these