Middle cerebral artery pressure laterality in patients with symptomatic ICA stenosis

Figures

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  Fig 1. Illustration of the ΔPMCA between the contra- and ipsilateral MCA. The curve corresponds to Lassen’s autoregulation curve and is a schematic relationship between the QMCA and the cerebral perfusion pressure (CPPMCA) in MCA. The CPPMCA is here defined as the mean arterial pressure in MCA minus the intracranial pressure. This means that MCA should have a maintained flow within a range of perfusion pressures at the MCAs. The separation between the contra- and ipsilateral CPPMCA was defined as ΔPMCA. The geometry is an example of the anterior part of CW. Left and right ICA branches into the left and right MCA and ACA1. The two ACA1s is connected by the ACoA before they branch into the left and right ACA2. The posterior circulation is not displayed in the figure, but the anterior and the posterior part is connected via the posterior communicating arteries.

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  Fig 2. Circuit analogy of the circle of Willis. The figure illustrates a schematic of the CW, denoting the ipsi (I)- and contralateral (C) side of the ICA stenosis (St). It is modelled as an electrical circuit, where the change in pressure across each artery is related to the flow (Q) and the vascular resistance (R) of the artery. The arrows indicate the normal flow direction in each artery, and the circles indicate the two pressure sites for the ipsi- and contralateral MCA pressure (PMCA). The two equations for PMCA,I describe how the pressure changes, starting at PMCA,C, across the anterior collateral pathway versus the posterior collateral pathway. They show that the pressure laterality between the ipsi- and contralateral MCA must be the same for both pathways. Note that the MCA resistance only refers to the arterial segment from the bifurcation to the location of the pressure measurement.

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  Fig 3. A computational geometry and mesh from a representative patient. From the posterior view, with left and right denoted in the figure. Note how only the anterior part of the CW was included in the model, according to our model assumption. The black square shows the mesh refinement region of our simulations. Longer segments of the arteries were included as flow extensions.

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  Fig 4. MCA pressure laterality. (a) Histogram of ΔPMCA for the patient group. (b) The CFD pressure of a stationary simulation for the case in Fig 3. A zero-reference pressure was set at the contralateral ICA, which was the right ICA inlet in this case. The ΔPMCA was 3.0 mmHg in this example.

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  Fig 5. MCA flow relationship to pressure. The ΔQMCA versus the ΔPMCA. The linear correlation was r = 0.47 (p = 0.011).

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  Fig 6. ICA and ACA flow relationship to pressure. (a) The ΔPMCA versus ΔQICA. The linear correlation was r = 0.85 (p<0.001). (b) The ΔPMCA versus ΔQACA. The linear correlation was r = 0.71 (p<0.001).