Memory loss inside the brain

TCD for Dementia and Alzheimer

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

References

Elevation in cerebral blood flow velocity with aerobic fitness throughout healthy human ageing – Philip N. Ainslie, James D. Cotter, Keith P. George, Sam Lucas, Carissa Murrell, Rob Shave, Kate N. Thomas, Michael J. A. Williams and Greg Atkinson; 2008

The Assessment of Cerebrovascular Response to a Language Task from the Addenbrooke’s Cognitive Examination in Cognitive Impairment: A Feasibility Functional Transcranial Doppler Ultrasonography Study – Lucy C Beishon, Ronney B Panerai, Thompson G Robinson, Hari Subramaniam, Victoria J Haunton;2018

Effects of brain training on brain blood flow (The Cognition and Flow Study-CogFlowS): protocol for a feasibility randomised controlled trial of cognitive training in dementia – Lucy C Beishon, Ronney B Panerai, Thompson G Robinson, Hari Subramaniam, Victoria J Haunton;2019

Blood flow velocity changes in anterior cerebral arteries during cognitive tasks performance – Boban M, Crnac P, Junakovic A, Garami Z, Malojcic B.; 2014

Transcranial Doppler to measure cerebral blood flow in delirium superimposed on dementia. A cohort study – Caplan GA, Lan Z, Newton L, Kvelde T, McVeigh C, Hill MA.;2014

Transcranial Doppler ultrasound blood flow velocity and pulsatility index as systemic indicators for Alzheimer’s disease – Roher AE, Garami Z, Tyas SL, Maarouf CL, Kokjohn TA, Belohlavek M, Vedders LJ, Connor D, et al.;2011

Altered cerebral hemodynamics in early Alzheimer disease: A pilot study using transcranial Doppler – Claassen JAHR, Diaz-Arrastia R, Martin-Cook K, Levine BD, Zhang R.;2009

Vasoreactivity induced by acetazolamide in patients with vascular dementia versus Alzheimer’s disease – Likitjaroen Y, Suwanwela NC, Phanthumchinda K.;2009

Cerebrovascular reactivity in degenerative and vascular dementia: A transcranial Doppler study – Asil T, Uzuner N.; 2005

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