<s>
A	O
hyperintensity	B-Algorithm
or	O
T2	B-Algorithm
hyperintensity	I-Algorithm
is	O
an	O
area	O
of	O
high	O
intensity	O
on	O
types	O
of	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	B-Algorithm
)	O
scans	O
of	O
the	O
brain	O
of	O
a	O
human	O
or	O
of	O
another	O
mammal	O
that	O
reflect	O
lesions	O
produced	O
largely	O
by	O
demyelination	O
and	O
axonal	B-Algorithm
loss	O
.	O
</s>
<s>
These	O
small	O
regions	O
of	O
high	O
intensity	O
are	O
observed	O
on	O
T2	B-Algorithm
weighted	O
MRI	B-Algorithm
images	O
(	O
typically	O
created	O
using	O
3D	B-Algorithm
FLAIR	I-Algorithm
)	O
within	O
cerebral	O
white	O
matter	O
(	O
white	B-Algorithm
matter	I-Algorithm
lesions	I-Algorithm
,	O
white	O
matter	O
hyperintensities	B-Algorithm
or	O
WMH	O
)	O
or	O
subcortical	O
gray	O
matter	O
(	O
gray	B-Algorithm
matter	I-Algorithm
hyperintensities	I-Algorithm
or	O
GMH	O
)	O
.	O
</s>
<s>
Hyperintensities	B-Algorithm
appear	O
as	O
"	O
bright	O
signals	O
"	O
(	O
bright	O
areas	O
)	O
on	O
an	O
MRI	B-Algorithm
image	O
and	O
the	O
term	O
"	O
bright	O
signal	O
"	O
is	O
occasionally	O
used	O
as	O
a	O
synonym	O
for	O
a	O
hyperintensity	B-Algorithm
.	O
</s>
<s>
Hyperintensities	B-Algorithm
are	O
commonly	O
divided	O
into	O
3	O
types	O
depending	O
on	O
the	O
region	O
of	O
the	O
brain	O
where	O
they	O
are	O
found	O
.	O
</s>
<s>
Deep	O
white	O
matter	O
hyperintensites	O
occur	O
deep	O
within	O
white	O
matter	O
,	O
periventricular	O
white	O
matter	O
hyperintensities	B-Algorithm
occur	O
adjacent	O
to	O
the	O
lateral	O
ventricles	O
and	O
subcortical	O
hyperintensities	B-Algorithm
occur	O
in	O
the	O
basal	O
ganglia	O
.	O
</s>
<s>
Hyperintensities	B-Algorithm
are	O
often	O
seen	O
in	O
auto	O
immune	O
diseases	O
that	O
have	O
effects	O
on	O
the	O
brain	O
.	O
</s>
<s>
Postmortem	O
studies	O
combined	O
with	O
MRI	B-Algorithm
suggest	O
that	O
hyperintensities	B-Algorithm
are	O
dilated	O
perivascular	O
spaces	O
,	O
or	O
demyelination	O
caused	O
by	O
reduced	O
local	O
blood	O
flow	O
.	O
</s>
<s>
White	O
matter	O
hyperintensities	B-Algorithm
can	O
be	O
caused	O
by	O
a	O
variety	O
of	O
factors	O
including	O
ischemia	O
,	O
micro-hemorrhages	O
,	O
gliosis	O
,	O
damage	O
to	O
small	O
blood	O
vessel	O
walls	O
,	O
breaches	O
of	O
the	O
barrier	O
between	O
the	O
cerebrospinal	O
fluid	O
and	O
the	O
brain	O
,	O
or	O
loss	O
and	O
deformation	O
of	O
the	O
myelin	O
sheath	O
.	O
</s>
<s>
Pathological	O
signs	O
of	O
oligodendritic	O
apoptosis	O
and	O
damage	O
to	O
axonal	B-Algorithm
projections	O
have	O
been	O
evident	O
.	O
</s>
<s>
Sufficient	O
damage	O
to	O
the	O
axons	B-Algorithm
that	O
course	O
through	O
WMH	O
can	O
cause	O
adequate	O
interference	O
with	O
normal	O
neuronal	O
functions	O
.	O
</s>
