TCD for Dementia and Alzheimer

Dementia is a progressive condition characterized by a gradual loss of cognitive and/or non-cognitive higher functions (e.g., language, visuospatial skills, attention). Mild cognitive impairment is characterized by a subjective and objective decline in cognitive function, although functional independence in daily living is maintained. It is increasingly recognized that impaired vascular function contributes early to the deposition of amyloid plaques and tau tangles in Alzheimer’s disease.

Several clinical studies have shown that decreased mean arterial flow velocity and increased Pulsatility Index are associated with clinical diagnosis of suspected Alzheimer disease. Cerebral circulatory disturbances revealed by these parameters thus reflect the global hemodynamic and structural consequences of a multifaceted disease process involving diffuse congestive microvascular pathologies, increased arterial stiffness, and decreased arterial compliance in conjunction with presumably age-related decline in cardiovascular performance.

Measurements with transcranial Doppler ultrasound in the area of cognitive and functional brain performance may provide early detection of such changes in cerebral blood flow.

Also, the use of Doppler sonography could be a reliable method not only to detect the onset of dementia or even Alzheimer’s disease, but it would also be suitable to visualize neurovascular training effects. These could, for example, serve as markers to predict which patients might benefit from specific cognitive training programs. Clinical studies suggest that regular endurance training can increase blood flow. Therefore, TCD could be used to test the effects of exercise on changes in cerebral blood flow velocity, e.g., in the MCA in healthy male subjects.

In the near future, TCD-based direct assessments of brain perfusion may offer the prospect of preventing or attenuating AD by identifying patients who would benefit from interventions to improve circulatory function.

Clinical indication:

• Evaluate restricted mean flow velocity and increased cerebral vascular resistance.in the basic cerebral arteries
• TCD-based cognitive tests with high activation potential could be used to discriminate between healthy individuals and patients with neurovascular or neurodegenerative diseases
• As differential diagnostics of various cognitive impairments and to distinguish between Vascular Dementia (VD) and Alzheimer disease (AD)
• Used as screening method to evaluate the progress of therapeutic interventions such as e.g. medication, physical and/or cognitive training

Application for TCD:

• Cognitive brain function tests such as language task, visual stimulation (e.g. Evoke flow), physical exercise
• Vasomotor reactivity testing e.g., BHI, Diamox test
• Autoregulation testing
• Routine scanning of the circle of Willis to evaluate mean velocity and PI