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Longitudinal relaxographic imaging of white matter hyperintensities in the elderly.

Anderson VC, Obayashi JT, Kaye JA, Quinn JF, Berryhill P, Riccelli LP, Peterson D, Rooney WD - Fluids Barriers CNS (2014)

Bottom Line: The vb of deep WMHs was 1.8 ± 0.6 mL/100 g and was significantly reduced compared to NAWM (2.4 ± 0.8 mL/100 g).In contrast, the vb of periventricular WMHs was unchanged compared to NAWM, decreased with ventricular volume and showed a positive association with ventricular permeability.Hyperintensities in the deep WM appear to be driven by vascular compromise, while those in the periventricular WM are most likely the result of a compromised ependyma in which the small vessels remain relatively intact.

View Article: PubMed Central - HTML - PubMed

Affiliation: Advanced Imaging Research Center, L452, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA.

ABSTRACT

Background: Incidental white matter hyperintensities (WMHs) are common findings on T2-weighted magnetic resonance images of the aged brain and have been associated with cognitive decline. While a variety of pathogenic mechanisms have been proposed, the origin of WMHs and the extent to which lesions in the deep and periventricular white matter reflect distinct etiologies remains unclear. Our aim was to quantify the fractional blood volume (vb) of small WMHs in vivo using a novel magnetic resonance imaging (MRI) approach and examine the contribution of blood-brain barrier disturbances to WMH formation in the deep and periventricular white matter.

Methods: Twenty-three elderly volunteers (aged 59-82 years) underwent 7 Tesla relaxographic imaging and fluid-attenuated inversion recovery (FLAIR) MRI. Maps of longitudinal relaxation rate constant (R1) were prepared before contrast reagent (CR) injection and throughout CR washout. Voxelwise estimates of vb were determined by fitting temporal changes in R1 values to a two-site model that incorporates the effects of transendothelial water exchange. Average vb values in deep and periventricular WMHs were determined after semi-automated segmentation of FLAIR images. Ventricular permeability was estimated from the change in CSF R1 values during CR washout.

Results: In the absence of CR, the total water fraction in both deep and periventricular WMHs was increased compared to normal appearing white matter (NAWM). The vb of deep WMHs was 1.8 ± 0.6 mL/100 g and was significantly reduced compared to NAWM (2.4 ± 0.8 mL/100 g). In contrast, the vb of periventricular WMHs was unchanged compared to NAWM, decreased with ventricular volume and showed a positive association with ventricular permeability.

Conclusions: Hyperintensities in the deep WM appear to be driven by vascular compromise, while those in the periventricular WM are most likely the result of a compromised ependyma in which the small vessels remain relatively intact. These findings support varying contributions of blood-brain barrier and brain-CSF interface disturbances in the pathophysiology of deep and periventricular WMHs in the aged human brain.

No MeSH data available.


Related in: MedlinePlus

Histograms of average CSF R1 values during CR washout. The mean (dashed line) and fitted Gaussian distribution (solid line) are also shown. Time, t, was calculated as the temporal midpoint of each variable-TI image set. Data from one subject who completed only two post-CR measurements were excluded.
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Figure 3: Histograms of average CSF R1 values during CR washout. The mean (dashed line) and fitted Gaussian distribution (solid line) are also shown. Time, t, was calculated as the temporal midpoint of each variable-TI image set. Data from one subject who completed only two post-CR measurements were excluded.

Mentions: In the absence of CR, CSF R1 values averaged 0.239 (±0.023) s−1, in good agreement with the 0.231- 0.237 s−1 reported previously [41,50]. These values increased to 0.244 (± 0.022) s−1 within 13 (±5) minutes after CR administration and continued to increase with time (F3,18 = 8.71, P < .0001). Figure 3 shows the R1 histograms of ventricular CSF during CR washout. The total change in R1 values over the 50–55 minute measurement period was 0.0091 (±0.01) s−1. Assuming a linear dependence of CSF R1 values on CR concentration, this corresponds to a ventricular permeability of approximately 3.4 μM hr−1. Although not statistically significant (P = 0.09), pWMH vb showed a moderate association (r2 = 0.22) with the R1 increase observed midway through the washout period (Figure 4a). An inverse association (r2 = 0.31; P = 0.04) of pWMH vb with ventricular volume was also observed (Figure 4b).


Longitudinal relaxographic imaging of white matter hyperintensities in the elderly.

Anderson VC, Obayashi JT, Kaye JA, Quinn JF, Berryhill P, Riccelli LP, Peterson D, Rooney WD - Fluids Barriers CNS (2014)

Histograms of average CSF R1 values during CR washout. The mean (dashed line) and fitted Gaussian distribution (solid line) are also shown. Time, t, was calculated as the temporal midpoint of each variable-TI image set. Data from one subject who completed only two post-CR measurements were excluded.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4209516&req=5

Figure 3: Histograms of average CSF R1 values during CR washout. The mean (dashed line) and fitted Gaussian distribution (solid line) are also shown. Time, t, was calculated as the temporal midpoint of each variable-TI image set. Data from one subject who completed only two post-CR measurements were excluded.
Mentions: In the absence of CR, CSF R1 values averaged 0.239 (±0.023) s−1, in good agreement with the 0.231- 0.237 s−1 reported previously [41,50]. These values increased to 0.244 (± 0.022) s−1 within 13 (±5) minutes after CR administration and continued to increase with time (F3,18 = 8.71, P < .0001). Figure 3 shows the R1 histograms of ventricular CSF during CR washout. The total change in R1 values over the 50–55 minute measurement period was 0.0091 (±0.01) s−1. Assuming a linear dependence of CSF R1 values on CR concentration, this corresponds to a ventricular permeability of approximately 3.4 μM hr−1. Although not statistically significant (P = 0.09), pWMH vb showed a moderate association (r2 = 0.22) with the R1 increase observed midway through the washout period (Figure 4a). An inverse association (r2 = 0.31; P = 0.04) of pWMH vb with ventricular volume was also observed (Figure 4b).

Bottom Line: The vb of deep WMHs was 1.8 ± 0.6 mL/100 g and was significantly reduced compared to NAWM (2.4 ± 0.8 mL/100 g).In contrast, the vb of periventricular WMHs was unchanged compared to NAWM, decreased with ventricular volume and showed a positive association with ventricular permeability.Hyperintensities in the deep WM appear to be driven by vascular compromise, while those in the periventricular WM are most likely the result of a compromised ependyma in which the small vessels remain relatively intact.

View Article: PubMed Central - HTML - PubMed

Affiliation: Advanced Imaging Research Center, L452, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA.

ABSTRACT

Background: Incidental white matter hyperintensities (WMHs) are common findings on T2-weighted magnetic resonance images of the aged brain and have been associated with cognitive decline. While a variety of pathogenic mechanisms have been proposed, the origin of WMHs and the extent to which lesions in the deep and periventricular white matter reflect distinct etiologies remains unclear. Our aim was to quantify the fractional blood volume (vb) of small WMHs in vivo using a novel magnetic resonance imaging (MRI) approach and examine the contribution of blood-brain barrier disturbances to WMH formation in the deep and periventricular white matter.

Methods: Twenty-three elderly volunteers (aged 59-82 years) underwent 7 Tesla relaxographic imaging and fluid-attenuated inversion recovery (FLAIR) MRI. Maps of longitudinal relaxation rate constant (R1) were prepared before contrast reagent (CR) injection and throughout CR washout. Voxelwise estimates of vb were determined by fitting temporal changes in R1 values to a two-site model that incorporates the effects of transendothelial water exchange. Average vb values in deep and periventricular WMHs were determined after semi-automated segmentation of FLAIR images. Ventricular permeability was estimated from the change in CSF R1 values during CR washout.

Results: In the absence of CR, the total water fraction in both deep and periventricular WMHs was increased compared to normal appearing white matter (NAWM). The vb of deep WMHs was 1.8 ± 0.6 mL/100 g and was significantly reduced compared to NAWM (2.4 ± 0.8 mL/100 g). In contrast, the vb of periventricular WMHs was unchanged compared to NAWM, decreased with ventricular volume and showed a positive association with ventricular permeability.

Conclusions: Hyperintensities in the deep WM appear to be driven by vascular compromise, while those in the periventricular WM are most likely the result of a compromised ependyma in which the small vessels remain relatively intact. These findings support varying contributions of blood-brain barrier and brain-CSF interface disturbances in the pathophysiology of deep and periventricular WMHs in the aged human brain.

No MeSH data available.


Related in: MedlinePlus