Transcranial doppler padaDementia

Dr.Fred Septo SpSRS Stroke Nasional Bukittinggi

• Aging and dementia are associated with changes in cerebrovascular structure and functioncognitive and functional declines

• Recent autopsy studies have stressed the important role of vascular pathologies in the manifestation of late onset dementia

• Alzheimer’s disease (AD) and vascular dementia (VaD) have generally reported reduced cerebral perfusion

• Chronic cerebral hypoperfusion could affect cellular health within the brain and the development of neurodegenerative pathologies

• Cerebral amyloid angiopathy refers to the deposition of β-amyloid in the media and adventitia of small and mid-sized arteries.

• Cerebral amyloid angiopathy has been recognized as one of the morphologic hallmarks of Alzheimer disease 

• The 3 most common mechanisms of vascular dementia are multiple cortical infarcts, a strategic single infarct, and small vessel disease.

• Arterial stiffness, which reflects an alteration in arterial mechanics, can be a risk factor for vascular dementia

• Transcranial Doppler (TCD) ultrasonography is a non-invasive, inexpensive and portable technique allowing continuous and bilateral recording of cerebral blood flow velocity through the major arteries

INSONATION

Syphon (ICA).Opthalmic artery

Midle cerebral artery (MCA), Anterior cerebral artery (ACA) Posterior cerebral artery (PCA)Bifurcatio ICA-MCA

Vertebral arteryBasilar artery

Distal ICA

• TCD methods have much to provide the assessment of functional cerebrovascular contributions to cognitive impairment and may help in the differentiation of dementia from normal aging and between the subtypes such as AD and VaD.

• Measurements – rest – cerebral vasomotor reactivity

•Breath holding index•Azetazolamide administration•CO2 inhalation

REST

• TCD metrics were employed to assess cerebral blood flow at rest including – mean flow velocity– systolic velocity– diastolic velocity– pulsatility index– emboli

Systolic upstroke or acceleration is defined as the initial slope of the peak velocity envelope during systole; corresponds to maximal contraction of left ventricle

(PSV-EDV)+EDV 3

MEAN FLOW VELOCITY

PULSATILITY INDEX

Pulsatility describes the degree of variability in the maximal flow velocities during the different phases of the cardiac cycle

PI: PV-EDVMFV

PULSATILITY INDEX

downstream vascular resistance

• Low MFV/high PI (2 or more artery) were documented in multiple vessels byTCD in patients with diffuse intracranial disease on contrast angiography (Sharma et al 2007)

• Dementia patients also demonstrated correlation between low velocity/high resistance flow pattern with degree of cumulative intracranial stenosis due to atheromatous disease (autopsy-based reports) (Roher AE et al 2004)

Cerebrovascular hemodynamics in Alzheimer's disease and vascular dementia: A meta-analysis of TCD

Alzheimer's disease (ES = −1.09, 95% CI −1.77 to −0.44, p = 0.004) vascular dementia (ES = −1.62, 95% CI −2.26 to −0.98, p < 0.001) significantly lower MFV compared with healthy controls.Pulsatility index was significantly higher in Alzheimer's disease (ES = 0.5, 95% CI 0.28–0.72, p < 0.001) -vascular dementia patients (ES = 2.34, 95% CI 1.39–3.29, p < 0.001). Patients with Alzheimer's disease had lower pulsatility index (ES = −1.22, 95% CI −1.98 to −0.46, p = 0.002) compared to subjects with vascular type of dementia.

Behnam et al 2011

Transcranial Doppler ultrasound blood flow velocity and pulsatility index as systemic indicators for Alzheimer’s disease

Alex E et al 2011

Micro embolic signal

• MES can be identified as – short lasting (<0.01–0.03 s),– unidirectional intensity increase, and intensity

increase (>3 dB) within the Doppler frequency spectrum.

– MESs appear randomly within the cardiac cycle and produce a “whistle,” “chirping,” or “clicking” sound when passing through the sample 

Association of Cerebral Emboli With Accelerated Cognitive Deterioration in Alzheimer’s Disease and Vascular Dementia

15,4 (95% CI=10.5–20.2) p=0.009

6,0 (95% CI=4.7–8.9) p=0.01

Nitin P et al 2012

59.0 (95% CI=40.1–78.0) (p=0.008)

12.0 (95% CI=5.7–18.4) (p<0.001

Conclusions : Spontaneous cerebral emboli predict more rapid progression of dementia over 2 years in both Alzheimer’s disease and vascular dementia

• TCD is an ideal functional test for detecting rapid changes in cerebral perfusion.

• Functional tests are evaluating the reserve mechanism of the cerbral vasculature using various stimuli such as hypocapnia or hypercapnia, increased or reduced systemic arterial pressure, and hypoxia

VASOMOTOR REACTIVITY

The assessment of cerebral vasoreactivity can provide information about vessels to adapt in response to systemic modification or brain metabolic activity requiring an increase or decrease in cerebral blood flow

Dahal A et al 2002

Reduction of this property has been found in association with situations predisposing one toward cerebrovascular disease

Chimowitz A et al 1992

Vasomotor Reactivity

Normal vasomotorLow resistance (arteriole)Increased velocity Resistance goes up

Velocity decreased

Breath holding Hyperventilation

VASOMOTOR REACTIVITYbreath holding index

TCD before breath holding (MFVbaseline) and at the end of 4 sec ( MFV end) of breathing after 30 sec of breath holding test

Cerebrovascular Reactivity in Degenerative and Vascular Dementia: A Transcranial Doppler Study

– 60 AD,58 VaD, 62 NDC.AD-VaD subjects  CO2 mixture inhalation followed by hyperventilation

– Lower FV and higher (PI) as compared with controls.

– Lower total VMR AD VaD groups as compared with controls. AD and VaD patients did not show significant differences (FV, PI values,cerebral vasoreactivity)

Vicenzini E et al,2007

Decreased Vasomotor Reactivity in Alzheimer’s DiseaseSoon-Tae Lee et al 2004

VMR was significantly reduced in AD group both in the rightside(24.5% vs. 36.6%, p<0.05) and left-side (20.7% vs. 34.1%, p<0.05) MCAs

Limitation TCD exam

• Operator experience• Poor transtemporal windows• Patient movement• Anatomi variation• Unknown tranducer to artery doppler angle• Improper instrument control setting• Displacement of arteries by an intracranial mass• Misinterpretation of collateral channels or

vasospasm as a stenosis• Distal branch disease