Transcranial doppler ultrasound blood flow velocity and pulsatility index as systemic indicators for Alzheimer's disease

Abstract

Background: Multiple lines of evidence suggest that cardiovascular co-morbidities hasten the onset of Alzheimer's disease (AD) or accelerate its course.

Methods: To evaluate the utility of cerebral vascular physical function and/or condition parameters as potential systemic indicators of AD, transcranial Doppler (TCD) ultrasound was used to assess cerebral blood flow and vascular resistance of the 16 arterial segments comprising the circle of Willis and its major tributaries.

Results: Our study showed that decreased arterial mean flow velocity and increased pulsatility index are associated with a clinical diagnosis of presumptive AD. Cerebral blood flow impairment shown by these parameters reflects the global hemodynamic and structural consequences of a multifaceted disease process yielding diffuse congestive microvascular pathology, increased arterial rigidity, and decreased arterial compliance, combined with putative age-associated cardiovascular output declines.

Conclusions: TCD evaluation offers direct physical confirmation of brain perfusion impairment and might ultimately provide a convenient and a noninvasive means to assess the efficacy of medical interventions on cerebral blood flow or reveal incipient AD. In the near term, TCD-based direct assessments of brain perfusion might offer the prospect of preventing or mitigating AD simply by revealing patients who would benefit from interventions to improve circulatory system function.

Figure 1

ROC curves for Lsiph and RdMCA pulsatility indices in subjects with AD and NDC. Lsiph PI, left siphon pulsatility index; RdMCA PI, right distal middle cerebral artery pulsatility index.

Figure 2

ROC curves for LICA and RdMCA mean flow velocities in subjects with AD and NDC. LICA MFV, left internal carotid artery mean flow velocity; RdMCA, right distal middle cerebral artery mean flow velocity.

Figure 3

Distribution values for Lsiph and RdMCA pulsatility indices in AD and NDC subjects. The cutoff values are represented by the black horizontal lines. Notice that more of the AD values are above the cutoff line for the PI than below indicating that increasing PI is correlated with AD. NDC, non-demented control; AD, Alzheimer’s disease; PI, pulsatility index; Lsiph, left siphon; RdMCA, right distal middle cerebral artery.

Figure 4

Distribution values for LICA and RdMCA mean flow velocities in cm/sec in AD and NDC subjects. The cutoff values are represented by the black horizontal lines. The majority of RdMCA and LICA MVF measures fall below the cutoff line in the AD group. NDC, non-demented control; AD, Alzheimer’s disease; MFV, mean flow velocity; LICA, left internal carotid artery; RdMCA, right distal middle cerebral artery.

Figure 5

Scatter charts of Lsiph and RdMCA pulsatility indices (A) and LICA and RdMCA mean flow velocities (B) in subjects with MCI. The cutoff values are represented by the black horizontal lines. NDC, non-demented control; AD, Alzheimer’s disease; PI, pulsatility index; Lsiph, left siphon; RdMCA, right distal middle cerebral artery; MFV, mean flow velocity; LICA, left internal carotid.