Science 13Mar2020

was the primary source of edema fluid, we
performed CSF cisternography using three-
dimensional (3D) fast imaging employing
steady-state acquisition (3D-FIESTA) mag-
netic resonance imaging (MRI). The CSF
compartment—including the lateral, third, and
fourth ventricles and the cisterna magna—
accounted for a total of 13 ± 1 mm^3 (Fig. 2A).
Smaller collections of fluid (7.6 ± 1.3 mm^3 )

were observed along the PVS of the large

arteries of the circle of Willis, and the rest of

the intracranial volume was occupied by the

brain tissue, including the intravascular com-

partment (509 ± 11 mm^3 ). After MCAO, CSF

in the lateral ventricle (Fig. 2B and Movie 1)

of the ischemic hemisphere and in the cis-

terna magna (Fig. 2C) slowly disappeared.

Total CSF volume in the ventricular system

and cisterna decreased by 9.0 ± 2.5% at 15 min

and 17 ± 3% at 29 min poststroke (Fig. 2, D

and E). PVS fluid volume began decreasing

at around 15 min (Fig. 2F), several minutes

after the CSF compartment started shrink-

ing (~5 min). Combined, these results add

additional support to the notion that CSF is

the primary source of early edema fluid after

ischemic stroke.

Mestreet al.,Science 367 , eaax7171 (2020) 13 March 2020 2of15

Contra Ipsi

MCAO

CSF 1 min 3 min 6 min 9 min 12 min 15 min

255

0

Pixel Intensity (AU)

MCA

CCA

Macrosphere

AB

E

F

D

-100

-95

-90

-85

rCBF (%)

CSF tracer infusion

MCAO

15 min15 min

G

-15 -10 -5 051015

0

5

10

0

50

100 MCAO

rCBF (%)

F/F

0

)

Time after MCAO (min)

Contralateral

Ipsilateral

P < 0.0001

0

2

4

6

8

Time to peak (min)

1 st 2 nd

MCA

CSF)

0.1

C

Sphere

H

Contralateral Ipsilateral

0 15304560

3.5

3.6

3.7

3.8

3.9

4.0

Time after MCAO (min)

Cortical water content(ml g dry weight

-1

)

P=0.001

Contralateral Ipsilateral Contralateral Ipsilateral

I

CSF tracer

i.v. bolus MCAO infusion MCAO

i.v. infusion

5 min 15 min

Blood CSF

(^22) Na+
(^3) H-mannitol 322 Na+
H-mannitol
J
0.00
0.05
0.10
0.15
0.20
0.25
Hemispheric uptake (%)
ns
ns
(^22) Na^3 H-mannitol
0
5
10
15
P = 0.013 P = 0.014
15 min15 min
Blood
CSF
Brain
(^3) H-mannitol
(^3) H-mannitol
(^22) Na+
(^22) Na+
H 2 O
H 2 O
Cl-
Cl-
KLM
(^22) Na + (^3) H-mannitol +
Contra Ipsi
F/F 0
min
Blood CSF
Hemispheric uptake (%)
Fig. 1. CSF rapidly enters the brain after stroke, resulting in edema.
(A) Macrospheres (arrow) were infused into the common carotid artery (CCA),
occluding the MCA. (B) Triphenyltetrazolium chloride staining after MCAO.
Contra, contralateral; Ipsi, ipsilateral. (C) Ipsilateral rCBF after MCAO.
(D) Intracisternal Alexa Fluor647–conjugated bovine serum albumin (BSA-647)
was infused 15 min before MCAO. (E) Ipsilateral and contralateral tracer
influx was imaged while measuring rCBF. (The white line indicates the sagittal
suture and fiber optic probe.) AU, arbitrary units. (F) Time series of rCBF
and fluorescence intensity (DF/F 0 ) in each hemisphere. Gray peaks are the
temporal derivative of fluorescence intensity. Repeated measures two-way analysis
of variance (ANOVA) was performed; interactionPvalue < 0.0001;n=5mice.
(G) Timing of the first and second peaks. (H) Water content of the cortex.
Mixed-effects repeated measures two-way ANOVA with Sidak’smultiple
comparisons test was performed;n= 4 to 7 mice per time point. The
shaded regions above and below the plot lines indicate SEM. (I)Thesource
of the edema fluid was identified by labeling either the blood or CSF
compartment. (J)^22 Na+and^3 H-mannitol were delivered intravenously
(i.v.). (K) Percentage of the total injected radiation found in each hemisphere
after intravenous delivery. Student’sttests with Holm-Sidak correction were
performed;n= 7 mice. ns, not significant. (L) Isotopes were delivered into
CSF. (M) Percentage of the total injected radiation in each hemisphere after
intracisternal delivery. Student’sttests with Holm-Sidak correction were
performed;n= 6 mice. In (B) and (E), scale bars are 2 mm. In (C), (G), (K),
and (M), error bars represent SEM.
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