PRENATAL DIAGNOSIS OF ARACHNOID CYSTS - … cysts are the surface of the brain at the level ......

Introduction

Arachnoid cysts are a rare central nervous system malfor-mation, representing only 1% of all intracranial masses innewborns [1]. Primary (congenital) arachnoid cysts arebenign accumulation of clear fluid between the dura andthe brain substance throughout the cerebrospinal axis inrelation to the arachnoid membrane and do not com-municate with the subarachnoid space [2]. Secondary(acquired) arachnoid cysts result from hemorrhage,trauma, and infection and usually communicate withthe subarachnoid space [1,3]. The common locations ofarachnoid cysts are the surface of the brain at the levelof main brain fissures, such as sylvian, rolandic and inter-hemispheric fissures, sella turcica, the anterior cranialfossa, and the middle cranial fossa [4]. Arachnoid cysts

may be associated with ventriculomegaly and dysgenesisof corpus callosum [5]. Prenatal ultrasound and mag-netic resonance imaging (MRI) have led to the increaseddiagnosis of central nervous system abnormalities ofthe fetuses (Figures 1–8: page 193–197, cases 1–3).

Prenatal Diagnosis

Fetal arachnoid cysts can be evaluated prenatally byultrasound and/or MRI [5–21]. To date, at least 27cases of fetal arachnoid cysts have been reported(Table). Among these, 9 cases had prenatal MRI evalu-ation in addition to ultrasound. The arachnoid cystcan appear as a hypoechoic lesion on prenatal ultra-sound. Most of fetal arachnoid cysts were first diag-nosed in the third trimester. In a few cases, the diagnosiswas made in the second trimester. Bretelle et al [18]reported the first-trimester diagnosis of a posterior fossaarachnoid cyst at 13 gestational weeks by transvaginalsonographic examination. The majority of arachnoidcysts are supratentorial with sylvian fissure cysts being

Taiwan J Obstet Gynecol • September 2007 • Vol 46 • No 3 187

PRENATAL DIAGNOSIS OF ARACHNOID CYSTS

Chih-Ping Chen*

Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, and Department of Biotechnology, Asia University, Taichung, Taiwan.

SUMMARY

Arachnoid cysts are a rare central nervous system malformation, representing only 1% of all intracranial massesin newborns. Primary (congenital) arachnoid cysts are benign accumulation of clear fluid between the dura andthe brain substance throughout the cerebrospinal axis in relation to the arachnoid membrane and do not com-municate with the subarachnoid space. Secondary (acquired) arachnoid cysts result from hemorrhage, trauma,and infection and usually communicate with the subarachnoid space. The common locations of arachnoidcysts are the surface of the brain at the level of main brain fissures, such as sylvian, rolandic and interhemi-spheric fissures, sella turcica, the anterior cranial fossa, and the middle cranial fossa. Arachnoid cysts may beassociated with ventriculomegaly and dysgenesis of corpus callosum. Prenatal ultrasound and magnetic resonanceimaging have led to the increased diagnosis of fetal arachnoid cysts. This article provides a thorough review of fetalarachnoid cysts, including prenatal diagnosis, differential diagnosis and associated chromosomal abnormalities,as well as comprehensive illustrations of perinatal imaging findings of fetal arachnoid cysts. Prenatal diagnosisof intracranial hypoechoic lesions should include a differential diagnosis of arachnoid cysts and prompt geneticinvestigations. [Taiwan J Obstet Gynecol 2007;46(3):187–198]

Key Words: arachnoid cysts, MRI, prenatal diagnosis, ultrasound

*Correspondence to: Dr Chih-Ping Chen, Department ofObstetrics and Gynecology, Mackay Memorial Hospital, 92,Section 2, Chung-Shan North Road, Taipei 104, Taiwan.E-mail: [email protected]: June 28, 2007

■ REVIEW ARTICLE ■

Taiwan J Obstet Gynecol • September 2007 • Vol 46 • No 3188

C.P. Chen

Tabl

e.R

epor

ted

case

s of

feta

l ara

chno

id c

ysts

dia

gnos

ed b

y ul

tras

ound

and

/or m

agne

tic r

eson

ance

imag

ing

(MR

I)

GW

at

GW

at

Pren

atal

MR

IA

utho

rspr

enat

alSo

nogr

aphi

c pr

enat

al M

RI

find

ings

inPe

rinat

al o

utco

me

[Ref

eren

ce]

Loca

tion

sono

grap

hic

find

ings

diag

nosi

sad

ditio

n to

cys

tdi

agno

sis

Dia

koum

akis

et a

l [6]

Supr

asel

lar

32

A 3

.5cm

sup

rase

llar c

ystic

–

–Va

gina

l del

iver

y at

37

wee

ks, 2

,654

g,

mas

sa

4.3

cm s

upra

sella

r ara

chno

id c

yst

35A

4cm

sup

rase

llar a

rach

noid

w

ith h

ydro

ceph

alus

, a s

olit

ary

seiz

ure

–cy

st w

ith h

ydro

ceph

alus

at a

ge 3

day

s, a

cys

tope

riton

eal s

hunt

at

age

19

days

Mei

zner

et a

l [7]

Parie

to-o

ccip

ital

22A

3.3

×3.

4cm

cys

tic m

ass

in

––

Vagi

nal d

eliv

ery

at 3

9 w

eeks

, 3,4

00g,

the

right

par

ieto

-occ

ipit

al lo

be

a 6

×7

cm a

rach

noid

cys

t, n

o of

the

brai

n, n

o hy

droc

epha

lus

hydr

ocep

halu

s, n

o de

fici

t or s

eizu

res,

38En

larg

emen

t of t

he c

yst u

p to

lo

st to

follo

w-u

p5

×4

cm

Ram

an e

t al [

8]Po

ster

ior f

ossa

24A

7.8

×9.

6cm

pos

terio

r cra

nial

–

–C

esar

ean

sect

ion

at 3

8 w

eeks

, 3,5

00g,

fo

ssa

cyst

, dila

tion

of th

e th

irda

post

erio

r fos

sa a

rach

noid

cys

t,

vent

ricle

vent

ricul

omeg

aly,

cys

tope

riton

eal a

ndve

ntric

ulop

erito

neal

shu

nts,

rec

urre

ntse

izur

es, d

eath

at a

ge 2

.5 m

onth

s

Lang

er e

t al [

9]C

ase

1Su

prat

ento

rial,

25A

3.0

×2.

2cm

ane

choi

c –

–Va

gina

l del

iver

y at

40

wee

ks, 3

,620

g,

mid

dle

cran

ial

supr

aten

toria

l mas

s w

ithin

the

an a

rach

noid

cys

t in

the

mid

dle

cran

ial

foss

arig

ht p

arie

to-o

ccip

ital

lobe

foss

a an

d rig

ht p

arie

to-o

ccip

ital

lobe

, 28

A s

light

incr

ease

in th

e di

amet

er

––

hydr

ocep

halu

s, a

cys

tope

riton

eal

of th

e cy

st (

4cm

),

shun

t at a

ge 2

mon

ths,

nor

mal

no

ven

tric

ulom

egal

yde

velo

pmen

t at a

ge 1

8 m

onth

sC

ase

2Su

prat

ento

rial,

32A

6cm

sup

rate

ntor

ial a

rach

noid

–

–C

esar

ean

sect

ion

at 4

0 w

eeks

, 3,0

80g,

m

idlin

ecy

st in

the

mid

line,

a

supr

asel

lar a

rach

noid

cys

t, m

ild

vent

ricul

ar d

ilatio

nve

ntric

ular

dila

tion,

cys

tope

riton

eal

and

vent

ricul

oper

itone

al s

hunt

s at

age

8 d

ays,

nor

mal

dev

elop

men

t at

age

20

days


Arachnoid Cysts

Hog

ge e

t al [

10]

Post

erio

r fos

sa–

A 1

×1

cm c

ystic

str

uctu

re in

–

–Te

rmin

atio

n of

pre

gnan

cy,

the

left

pos

terio

r fos

sa,

a pr

omin

ent n

ose,

mic

rogn

athi

a,

com

pres

sing

the

right

ov

erla

ppin

g of

the

fing

ers,

a th

in-

cere

bella

r hem

isph

ere

wal

led

cyst

com

pres

sing

the

right

ce

rebe

llar h

emis

pher

e, a

kar

yoty

pe

of 4

6,X,

der

(X)t

(X;9

)(q2

2;q2

2)m

atw

ith p

artia

l tris

omy

9q a

nd p

artia

lm

onos

omy

Xq a

t am

nioc

ente

sis

Has

san

et a

l [11

]C

ase

2M

idlin

e17

Bila

tera

l ven

tric

ulom

egal

y,

––

Term

inat

ion

of p

regn

ancy

at 2

4 w

eeks

, a

mid

line

cyst

ic s

truc

ture

in

886

g, a

mid

line

arac

hnoi

d cy

st,

the

ante

rior h

alf o

f the

bra

in

vent

ricul

omeg

aly,

no

asso

ciat

ed

mea

surin

g 0.

8×

0.8

cmm

alfo

rmat

ions

, a k

aryo

type

of

24Pr

ogre

ssiv

e in

crea

se o

f the

46

,XY

at a

mni

ocen

tesi

scy

stic

siz

e an

d w

orse

ning

ve

ntric

ulom

egal

y

Pilu

et a

l [12

]C

ase

1M

idlin

e an

d th

e 23

A la

rge

mid

line

cyst

in th

e C

ases

1–3

: One

ter

min

atio

n of

an

terio

r-m

iddl

e an

terio

r-m

iddl

e th

ird o

f bra

in,

preg

nanc

y, tw

o de

liver

ed a

t ter

m:

third

of b

rain

agen

esis

of c

orpu

s ca

llosu

ma

cyst

oper

itone

al s

hunt

in b

oth,

C

ase

2A

s in

Cas

e 1

32A

s in

Cas

e 1

––

norm

al d

evel

opm

ent a

t age

s 6

and

Cas

e 3

As

in C

ase

122

As

in C

ase

1–

–9

year

sC

ase

4M

idlin

e an

d th

e 28

A la

rge

mid

line

cyst

in p

oste

rior

––

Cas

es 4

–5: D

eliv

ery

at t

erm

, po

ster

ior t

hird

th

ird o

f bra

ina

cyst

oper

itone

al s

hunt

in o

ne c

ase,

of

bra

inno

rmal

dev

elop

men

t at a

ges

2 an

d C

ase

5A

s in

Cas

e 4

28A

s in

Cas

e 4

––

7 ye

ars

Cas

e 6

Am

bien

t cis

tern

22A

sm

all c

yst i

n am

bien

t cis

tern

, –

–Te

rmin

atio

n of

pre

gnan

cy, t

risom

y do

uble

-out

let r

ight

ven

tric

le,

18 a

t pre

nata

l dia

gnos

iscl

ench

ed h

ands

Cas

e 7

Am

bien

t cis

tern

34A

sm

all c

yst i

n am

bien

t cis

tern

, –

–D

eliv

ery

at te

rm, s

eizu

res,

dev

elop

men

tal

agen

esis

of c

orpu

s ca

llosu

mde

lay

at a

ge 4

yea

rs (con

tinue

d on

nex

t pag

e)


C.P. Chen

Tabl

e.(c

ontin

ued)

GW

at

GW

at

Pren

atal

MR

IA

utho

rspr

enat

alSo

nogr

aphi

c pr

enat

al M

RI

find

ings

inPe

rinat

al o

utco

me

[Ref

eren

ce]

Loca

tion

sono

grap

hic

find

ings

diag

nosi

sad

ditio

n to

cys

tdi

agno

sis

Raf

fert

y et

al [

13]

Mid

dle

cran

ial

33M

acro

ceph

aly,

righ

t–

–C

esar

ean

sect

ion

at 3

9 w

eeks

, fo

ssa

vent

ricul

omeg

aly,

a 5

cm

an e

ndos

copi

c fe

nest

ratio

n of

the

mid

dle

cran

ial f

ossa

cy

st o

n da

y 1,

nor

mal

dev

elop

men

t ar

achn

oid

cyst

at a

ge 6

mon

ths

Levi

ne e

t al [

14]

Cas

e 1

–22

An

arac

hnoi

d cy

st–

Part

ial a

gene

sis

–31

of c

orpu

s ca

llosu

m w

ith

abse

nt b

ody

and

sple

nium

Cas

e 2

Mid

line

20A

mid

line

arac

hnoi

d cy

st–

Nor

mal

cor

pus

–ca

llosu

m th

at

was

not

vi

sual

ized

by

sono

grap

hyC

ase

3–

26A

larg

e ar

achn

oid

cyst

–Ex

tent

of m

ass

–27

effe

ct o

n 33

surr

ound

ing

36st

ruct

ures

Elbe

rs a

nd F

urne

ss [

15]

Supr

aten

toria

l18

.5A

larg

e m

idlin

e ar

achn

oid

cyst

––

Ces

area

n se

ctio

n at

38

wee

ks, n

orm

al

30D

ecre

ase

of th

e cy

st s

ize

deve

lopm

ent a

t age

2 y

ears

32C

ompl

ete

reso

lutio

n of

the

cyst

Bla

iche

r et a

l [5]

Cas

e 1

Left

-tem

pora

l, 39

A 6

×3.

8×

2.4

cm h

ypoe

choi

c 39

A p

eris

ylvi

an

Elec

tive

cesa

rean

sec

tion,

3,4

95g,

pe

risyl

vian

hom

ogen

eous

lesi

on in

the

arac

hnoi

d cy

st

no n

euro

logi

cal a

bnor

mal

ity, n

orm

al

left

par

ieta

l hem

isph

ere

with

no

deve

lopm

ent a

t age

6 m

onth

sco

mpr

essi

on

of s

urro

undi

ngst

ruct

ures

Cas

e 2

Third

ven

tric

le34

3×

5×

1.2

cm a

sym

met

ric

34C

allo

sal

Ces

area

n se

ctio

n at

39

wee

ks, 3

,300

g,


Arachnoid Cysts

hypo

echo

ic h

omog

eneo

us

dysg

enes

is,

repe

ated

apn

eas

and

gene

raliz

ed

lesi

on in

the

third

ven

tric

le

norm

al fa

lx

seiz

ures

, ant

icon

vuls

ive

ther

apy

with

se

para

ting

the

basa

l gan

glia

, ce

rebr

i, co

rtic

al

phen

ytoi

n, s

light

ly a

bnor

mal

m

ild b

ilate

ral d

ilatio

n of

pa

tter

n,

deve

lopm

ent a

t age

5 m

onth

s w

ith

the

post

erio

r hor

nsce

rebe

llum

, di

min

ishe

d he

ad c

ontr

ol a

nd r

educ

ed

basa

l gan

glia

vi

sual

fix

atio

nan

d br

ain

stem

Gol

ash

et a

l [16

]Su

pras

ella

r17

A 2

.5cm

mid

line

cyst

ic le

sion

28Sl

ight

dila

tion

Elec

tive

cesa

rean

sec

tion

at 3

8 w

eeks

, 24

Cys

t siz

e 3.

2cm

of th

e oc

cipi

tal

vent

ricul

omeg

aly

and

mac

roce

phal

y,

28C

yst s

ize

3.2

cmho

rns

of th

e en

dosc

opic

cys

tove

ntric

ulos

tom

y la

tera

l an

d cy

stoc

iste

rnos

tom

y, n

orm

al

vent

ricle

sde

velo

pmen

t at a

ge 2

yea

rs

Nak

amur

a et

al [

17]

Prep

ontin

e-28

Mac

roce

phal

y, e

nlar

ged

28A

sup

ra a

nd

Vagi

nal d

eliv

ery

at 3

5 w

eeks

, su

pras

ella

rve

ntric

les

and

a m

idlin

e in

frat

ento

rial

impl

emen

tatio

n of

a c

yst-

perit

onea

l cy

stic

lesi

onfo

ssae

cys

t sh

unt o

n da

y 18

, end

osco

pic

com

pres

sing

cy

stov

entr

icul

osto

my

at a

ge

the

brai

n st

em2

mon

ths,

a 1

-mon

th d

elay

of

deve

lopm

ent a

t age

4 m

onth

s

Bre

telle

et a

l [18

]Po

ster

ior f

ossa

13A

n an

echo

ic m

ass

abov

e th

e –

–Te

rmin

atio

n at

15

wee

ks, 1

03g,

po

ster

ior f

ossa

and

bet

wee

n ka

ryot

ype

46,X

Y, a

pos

terio

r med

ian

the

two

occi

pita

l lob

esar

achn

oid

cyst

, no

othe

r ano

mal

ies

Sout

er e

t al [

19]

Cas

e 2

Mid

line

25Te

tral

ogy

of F

allo

t–

–C

esar

ean

sect

ion

at 3

7 w

eeks

, 1,9

61g,

34IU

GR

, a 1

.8×

2.0

cm m

idlin

e fa

cial

dys

mor

phis

m, i

ngui

nal h

erni

as,

intr

acra

nial

ara

chno

id c

yst,

te

tral

ogy

of F

allo

t with

a la

rge

post

erio

r and

sup

erio

r to

over

ridin

g ao

rta,

MR

I con

firm

ed

the

thal

ami

a 2

×1.

1×

1.2

cm m

idlin

e ar

achn

oid

cyst

, mar

ked

glob

al d

evel

opm

enta

l de

lay

at a

ge 1

3 m

onth

s, a

pos

tnat

al

kary

otyp

e of

46,

XY,d

er(1

4)t(

14;2

0)

(q32

.2;p

13)

with

a s

ubte

lom

eric

de

letio

n of

the

dist

al lo

ng a

rm o

f ch

rom

osom

e 14

. (con

tinue

d on

nex

t pag

e)


C.P. Chen

Tabl

e.(c

ontin

ued)

GW

at

GW

at

Pren

atal

MR

IA

utho

rspr

enat

alSo

nogr

aphi

c pr

enat

al M

RI

find

ings

inPe

rinat

al o

utco

me

[Ref

eren

ce]

Loca

tion

sono

grap

hic

find

ings

diag

nosi

sad

ditio

n to

cys

tdi

agno

sis

Kus

aka

et a

l [20

]Q

uadr

igem

inal

30

An

anec

hoic

mas

s in

the

31N

o ob

liter

atio

n N

orm

al v

agin

al d

eliv

ery,

no

cist

ern

quad

rigem

inal

cis

tern

of

the

cere

bral

hy

droc

epha

lus

at a

ge 1

yea

rw

ithou

t hyd

roce

phal

usaq

uedu

ct, n

o co

mm

unic

atio

nbe

twee

n th

e ve

ntric

ular

syst

em a

ndth

e cy

st

Fujim

ura

et a

l [21

]Su

pras

ella

r25

A 3

-cm

mid

line

cyst

ic le

sion

, 28

Con

firm

atio

n of

Va

gina

l del

iver

y at

37

wee

ks, 2

,844

g,

no v

entr

icul

omeg

aly

a su

pras

ella

r en

dosc

opic

cys

tove

ntric

ulos

tom

y at

ar

achn

oid

cyst

age

5 m

onth

s, n

orm

al d

evel

opm

ent

at a

ge 3

yea

rs

GW

=ge

stat

iona

l wee

ks; –

= no

info

rmat

ion;

IUG

R =

intr

aute

rine

grow

th re

stric

tion.

the most common. Arachnoid cysts may progressivelyenlarge in utero, causing ventriculomegaly. Elbers andFurness [15] reported an unusual case of presumedarachnoid cyst diagnosed at 18.5 weeks’ gestation.The cyst resolved at 32 weeks’ gestation. Serial prena-tal sonographic examinations are able to assess thesize of the cyst and the ventricles. Prenatal MRI helpsto demonstrate the anatomic details of other centralnervous system abnormalities, such as compression ofthe aqueduct, communication between the cyst andthe ventricles, and corpus callosum dysgenesis.

Differential Diagnosis

Prenatal diagnosis of intracranial hypoechoic cysticlesions should include a differential diagnosis of arach-noid cysts, porencephalic cysts, glioependymal cysts,choroid plexus cysts, aneurysms of the vein of Galen,schizencephaly, cystic neoplasms, and intracranialhemorrhage [12].


Arachnoid Cysts

Figure 1. Prenatal ultrasound of an arachnoid cyst of case 1.Prenatal ultrasound at 32 weeks’ gestation revealed a 5.39 ×3.94 cm midline interhemispheric hypoechoic homogeneouslesion. Magnetic resonance imaging (MRI) at 33 gestationalweeks showed a left interhemispheric arachnoid cyst, markeddysgenesis of the corpus callosum, and colpocephaly. The kary-otype was 46,XY. A 2,788-g male baby was delivered at 37weeks’ gestation. Postnatal MRI confirmed the prenatal diag-nosis. A cystoperitoneal shunt was performed at age 7 months.The infant was doing well at age 1 year and 2 months.

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Figure 2. (A) Sagittal, (B) axial and (C) coronalviews of magnetic resonance imaging of case 1 at33 weeks’ gestation.

Porencephalic cystsPorencephalic cysts are usually unilateral and communi-cate with the ventricular system with a cavity lined withwhite matter. Porencephalic cysts result from infarc-tion of the brain secondary to vascular insults, trauma,infection, hemorrhage, or monochorionic monozygotictwin–twin transfusion. In contrast, arachnoid cysts areusually asymmetric and smooth-walled; they do notcommunicate with the ventricular system and have amass effect.

Glioependymal cystsGlioependymal cysts are usually multilocular and locatedwithin the brain parenchyma. Glioependymal cysts havean ependymal lining, whereas, arachnoid cysts have

fibrous walls. Glioependymal cysts may have a masseffect and are often associated with agenesis of thecorpus callosum.

Choroid plexus cystsChoroid plexus cysts, unilateral or bilateral, are fre-quently detected in the second trimester. Choroid plexuscysts are sonolucent cysts within the choroids plexusof the lateral ventricle. Large choroid plexus cysts maybe associated with trisomy 18.

Aneurysms of the vein of GalenAneurysms of the vein of Galen are vascular anomaliesof the vein of Galen located in the brain deeply andposteriorly to the thalami and in the subarachnoidspace. Color Doppler is helpful for the diagnosis ofaneurysms of the vein of Galen. Prenatal sonographicdetection of fluid-filled lesions in the posterior third of the brain, which are found in association withhydrops fetalis, ventriculomegaly, porencephaly, singleumbilical artery, chorioangioma or limb reductiondefects, should raise the suspicion of aneurysms of thevein of Galen.

SchizencephalySchizencephaly or true porencephaly is characterizedby unilateral, asymmetric or bilateral congenital full-thickness clefts of the cerebral mantle. Schizencephalymay or may not communicate with the ventricular sys-tem and are lined by gray matter. Schizencephaly canbe associated with ventriculomegaly, polymicrogyria,heterotopias, agenesis of the corpus callosum, absentseptum pellucidum, and optic nerve hypoplasia.

Cystic neoplasmsCystic neoplasms, such as cystic teratoma and cysticastrocytoma, consist of solid and irregular cystic com-ponents and have a mass effect.


C.P. Chen

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Figure 3. (A) Sagittal and (B) axial views of postnatal magnetic resonance imaging of case 1 at age 3 days.

Figure 4. Prenatal ultrasound of an arachnoid cyst of case 2.Prenatal ultrasound of case 2 at 31 weeks’ gestation revealeda 1.97 × 2.87 cm left interhemispheric hypoechoic homoge-neous lesion. Magnetic resonance imaging (MRI) at 32 weeks’gestation showed a left interhemispheric arachnoid cyst andcolpocephaly. A 2,620-g male baby was delivered at term.Postnatal MRI confirmed the prenatal diagnosis. The size ofthe arachnoid cyst was measured about 6.81 × 3.71 cm.There was a left-to-right midline shift. A cystoperitonealshunt was performed at age 8 months. The child was doingwell at age of 3 years and 4 months.

Intracranial hemorrhageIntracranial hemorrhage usually occurs in the subependy-mal germinal matrix region and is associated withhypoxia, platelet disorders, coagulopathy, alterationsin cerebral blood pressure in the case of twin–twintransfusion or demise of a monozygotic co-twin, feto-maternal hemorrhage, and maternal medications. Intra-cranial hemorrhage may initially present echogenicblood clots in the ventricles and subsequently lead toventricular dilation.

Chromosomal Abnormalities Associatedwith Congenital Arachnoid Cysts

Fetal arachnoid cysts can be associated with chromo-somal abnormalities. Therefore, prenatal diagnosis of anarachnoid cyst, especially in association with structuralabnormalities, should prompt a cytogenetic investiga-tion. Various associated chromosomal abnormalitieshave been reported. For instance, Hogge et al [10]reported partial trisomy 9q (9q22 � qter) and partialmonosomy Xq (Xq22�qter) in a fetus with an infraten-torial arachnoid cyst. The fetus postnatally manifested

a prominent nose, micrognathia, overlapping of thefingers, and a thin-walled cyst compressing the rightcerebellar hemisphere. Souter et al [19] reported asubtelomeric deletion of the distal long arm of chro-mosome 14, i.e. monosomy 14q (14q32.3 � qter), in a fetus with tetralogy of Fallot, intrauterine growthrestriction, and a midline intracranial arachnoid cyst.The infant postnatally manifested facial dysmorphism,inguinal hernias, tetralogy of Fallot, a midline arach-noid cyst, and marked global developmental delay. Piluet al [12] reported trisomy 18 in a fetus with a smallarachnoid cyst in the ambient cistern, a double-outletright ventricle, and clenched hands. Elbers and Furness[15] additionally reported their experience of the asso-ciation of triploidy with a fetus with an arachnoid cyst.

Fetal Outcome

The prognosis of fetal arachnoid cysts is dependent onthe presence or absence of the corpus callosum, thepresence or absence of other congenital malformations,parenchymal hemorrhages, the rate of the growth ofthe cyst, and progression of ventriculomegaly. Fetal


Arachnoid Cysts

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Figure 5. (A) Sagittal, (B) axial and (C) coronalviews of magnetic resonance imaging of case 2at 32 weeks’ gestation.

arachnoid cysts without associated structural anomaliesor chromosomal abnormalities can have a favorableoutcome. In some cases with rapid progression of thelesion and ventriculomegaly, appropriate pediatric sur-gical therapy may be required in early infancy. Currently,postnatal endoscopic cystoventriculostomy and cysto-cisternostomy have become less invasive surgical alter-natives [16,17,21]. The prognosis of fetal intracranialcysts has been shown to rely on the brain integrityrather than the cyst volume or location [22]. Therefore,in order to establish the correct prognosis and intellec-tual outcome of fetuses with arachnoid cysts, MRI is animportant adjunct to ultrasound and helps to optimizeneonatal management by accurate determination ofthe fetal anatomy and objective perinatal counseling.

Conclusion

This article provides a thorough review of fetal arachnoidcysts, including prenatal diagnosis, differential diagnosisand associated chromosomal abnormalities, as well as


C.P. Chen

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Figure 6. (A) Sagittal, (B) axial and (C) coronalviews of postnatal magnetic resonance imaging ofcase 2.

Figure 7. Prenatal ultrasound of an arachnoid cyst of case 3.Prenatal ultrasound of case 3 at 23 weeks’ gestation revealeda 1.45 × 3.03 cm midline interhemispheric hypoechoic homo-geneous lesion. The karyotype was 46,XY. Magnetic resonanceimaging (MRI) at 24 weeks’ gestation showed an interhemi-spheric arachnoid cyst and dysgenesis of the corpus callosum.Progression of the cyst was noted in late gestation. A 2,350-gmale baby was delivered prematurely at 28 weeks’ gestation.Postnatal MRI confirmed the prenatal diagnosis. A cysto-peritoneal shunt was performed at age of 1 week. The childwas doing well at age 4 years.


Arachnoid Cysts

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Figure 8. (A) Sagittal, (B) axial, and (C) coronalviews of magnetic resonance imaging of case 3at 24 weeks’ gestation.

comprehensive illustrations of perinatal imaging find-ings of fetal arachnoid cysts. Prenatal diagnosis ofintracranial hypoechoic lesions should include a differ-ential diagnosis of arachnoid cysts and prompt geneticinvestigations.

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with subtle subtelomeric chromosomal rearrangements.Ultrasound Obstet Gynecol 2003;21:609–15.

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