Non-Cognitive Behavioral Symptoms in Vascular Cognitive Impairment
Kenneth Rockwood, MD
Dalhousie University
Halifax, Nova Scotia, Canada

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.

 

Reporter: Elizabeth Coolidge-Stolz