Decrease in parietal cerebral hemoglobin oxygenation during performance of a verbal fluency task in patients with Alzheimer's disease monitored by means of near-infrared spectroscopy (NIRS)--correlation with simultaneous rCBF-PET measurements.
We used near-infrared spectroscopy (NIRS) to study non-invasively changes in cerebral hemoglobin oxygenation in the frontal and parietal cortex during performance of a verbal fluency task in patients with Alzheimer's disease (AD). Whereas healthy elderly subjects (n = 19, age 67 +/- 10 years) showed increases in concentrations of oxygenated hemoglobin [HbO2] (mean (arbitrary units) +/- S.E.M., 1.44 +/- 0.59) and total hemoglobin [HbT] (0.92 +/- 0.81) over the left superior parietal cortex, patients with AD (n = 19, age 71 +/- 10 years) showed significant decreases in [HbO2] (-3.26 +/- 1.30, P < 0.01) as well as [HbT] (-4.45 +/- 1.57, P < 0.01). [HbR] decreased slightly in both groups (-0.62 +/- 0.29 and - 1.18 +/- 0.40, respectively). Using two pairs of NIRS optodes placed on the left superior partietal cortex and on the left prefrontal cortex simultaneous increases in [HbO2] as well as [HbT] in both cortical regions in the healthy elderly subjects (n = 8, age 60 +/- 15) were demonstrated during performance of the task. AD patients (n = 10, age 65 +/- 13 years) showed decreases in [HbO2] and [HbT] in the parietal cortex and, at the same time, increases in [HbO2] and [HbT] in the frontal cortex. Simultaneous NIRS-[HbT] and PET-rCBF measurements showed a significant correlation both when calculated in a 'banana' shaped volume approximated by using cortical thresholds as well as when calculated in a semisphere volume of brain tissue beneath the optodes placed on the head surface (patients with AD, n = 10). The correlation was dependent on the assumed penetration depth of the near-infrared light and was best for all three NIRS variables ([HbO2], [HbR] and [HbT]) when calculated using a semisphere radius of 0.45 cm to 1.35 cm. In conclusion, in Alzheimer's disease a marked reduction of regional cerebral blood flow and cerebral hemoglobin oxygenation may occur during activation of brain function, probably mainly in degenerating brain areas, such as the parietal cortex.
Hock
C
C
Psychiatrische Universitätsklinik (PUK), Basel, Switzerland. hock@ubaclu.unibas.ch
Villringer
K
K
Müller-Spahn
F
F
Wenzel
R
R
Heekeren
H
H
Schuh-Hofer
S
S
Hofmann
M
M
Minoshima
S
S
Schwaiger
M
M
Dirnagl
U
U
Villringer
A
A
D000368:Aged; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010296:Parietal Lobe / Q000378:metabolism*; D015203:Reproducibility of Results; D013055:Spectrophotometry, Infrared; D014055:Tomography, Emission-Computed; D014705:Verbal Behavior / Q000502:physiology*
D006454:Hemoglobins; D010100:Oxygen