Dr.
Rockwood's research involves non-cognitive behavioral and psychological
symptoms in patients with vascular cognitive impairment. Of
the three subtypes of this condition-- vascular dementia, vascular
dementia mixed with Alzheimer's disease, and vascular cognitive
impairment no dementia (often abbreviated as vascular CIND)
-- the most recently defined vascular CIND state is well characterized
clinically by such a profile of symptoms. His group hopes that
continuing analysis of their data will enable physicians to
improve diagnostic and prognostic skills in caring for patients
with the general condition of vascular cognitive impairment,
the subtype of vascular cognitive impairment no dementia, and
the specific state of subcortical ischemia, which has been least
well defined to date.
Dr. Rockwood opened with an introduction
of vascular cognitive impairment, explaining that its subtypes
include the previously defined conditions of vascular dementia
and vascular dementia mixed with Alzheimer's disease, as well
as a newly defined condition termed vascular cognitive impairment
no dementia, often abbreviated as vascular CIND.
Previous studies of patients with post-stroke dementia or
multi-infarct dementia have established that non-cognitive
behavioral problems can be significant in these populations.
In addition, more recent work has shown that subcortical ischemia
can cause clinically significant behavioral problems; proposed
diagnostic criteria rely heavily on behavioral and psychological
symptoms rather than language, memory, or other higher-level
functions. The typical clinical presentation is a disexecutive
syndrome.
When the current work began, a group of Canadian memory centers
enrolled 1,347 patients, all of whom had been diagnosed with
vascular cognitive impairment. Of the total, 324 patients
were diagnosed with the relatively newly defined disorder
vascular cognitive impairment no dementia. The investigators
accumulated as much observational data as possible on these
patients with use of all proposed criteria and of commonly
used scales such as the Mini Mental State Examination and
the Disability Assessment for Dementia.
Two groups of patients were used for comparison: people who
had been evaluated at the same clinics and were found not
to have cognitive impairment and patients diagnosed with Alzheimer's
disease.
When data for the three patient groups were analyzed individually
and then compared, the researchers found that vascular cognitive
impairment was indeed characterized by a prominent disexecutive
syndrome that was present to some degree in all patients and
was most prominent in patients with severe dementia. Clinically,
this disexecutive profile was markedly different from that
seen in patients with Alzheimer's disease. However, it was
difficult to distinguish the two profiles based on current
analytical tools.
Next, they began a search for a macroscopic state variable
for the disexecutive syndrome characteristic of vascular cognitive
impairment and subcortical ischemia: a useful clinical index
of signs or symptoms that represents the overall state of
cognitive brain function. Rockwood used the example of temperature
as a macroscopic state variable to describe the kinetic energy
in a glass of water. The overall (macroscopic) variable validly
describes the system as a whole (all of the water in the glass)
but is not derived from evaluation of individual contributions
(the energy in each molecule of water at any given moment
of time).
In clinical practice, this approach meant the researchers
looked at the behavioral variables assessed in the three patient
groups and selected 50 that might be appropriate. An index
of roughly 20 variables was developed and it was found to
be valid as a predictor of such important outcomes as need
for institutionalization and elevated risk for death.
The most common behavioral symptom reported was decreased
initiative (61%), followed by decreased mood (33%). Using
the index of 20 symptoms, the mean index value for VCI was
4.3±2.5, compared with 3.5±2.2 in patients diagnosed with
probable Alzheimer's disease. The highest value was in patients
with vascular dementia mixed with Alzheimer's disease. The
lowest was found in patients with vascular CIND.
Current work involves formal qualitative evaluation of patients
with vascular cognitive impairment no dementia (vascular CIND)
to see which variables are most capable of being captured
in a standard psychometric test.
Rockwood concluded that identification of a disexecutive
syndrome among patients with vascular cognitive impairment
has proven to be accurate based on the data from the Canadian
study. In particular, such a syndrome is the dominant clinical
presentation in patients with impairment from subcortical
ischemia. Even though psychometric tools are in development,
the diagnosis remains one of clinical judgment, meaning that
a careful history and physical examination remain the physician's
most important tools.
|