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Chapter 10 Intrauterine Insults: Fetal Stroke and Destructive Processes
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71. Brouwer MJ, de Vries LS, Pistorius L, Rademaker KJ, Groenendaal
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72. Larroque B, Marret S, Ancel PY, et al. White matter damage and
intraventricular hemorrhage in very preterm infants: The EPIPAGE
study. J Pediatr. 2003;143:477–483.
73. Fanaroff AA, Wright LL, Stevenson DK, et al. Very-low-birth-weight
outcomes of the National Institute of Child Health and Human
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and intraventricular hemorrhage. Pediatr Neurosurg. 2006;42:
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75. Grant EG. Pathophysiology of germinal matrix-related hemorrhage
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76. Volpe JJ. Brain injury in the premature infant—from pathogenesis to
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77. Volpe JJ. Edward B. Neuhauser lecture: Current concepts of brain
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78. Burrows RF, Caco CC, Kelton JG. Neonatal alloimmune thrombocytopenia: Spontaneous in utero intracranial hemorrhage. Am J
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79. Fogarty K, Cohen HL, Haller JO. Sonography of fetal intracranial
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81. Knuppel RA, Salvatore DL, Agarwal R, Leiman S, Sikka A.
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82. Lustig-Gillman I, Young BK, Silverman F, et al. Fetal intraventricular
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86. Coulson CC, Kuller JA, Sweeney WJ. Nonimmune hydrops and
hydrocephalus secondary to fetal intracranial hemorrhage. Am J
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87. Serrarens-Janssen VM, Semmekrot BA, Novotny VM, et al. Fetal/
neonatal allo-immune thrombocytopenia (FNAIT): Past, present,
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88. Huang YF, Chen WC, Tseng JJ, Ho ES, Chou MM. Fetal intracranial hemorrhage (fetal stroke): Report of four antenatally diagnosed cases and review of the literature. Taiwan J Obstet Gynecol.
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89. Grant EG. Neurosonography: Germinal matrix-related hemorrhage. In: Grant EG, ed. Neurosonography of the Pre-term Neonate.
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90. Rutherford MA. Magnetic resonance imaging of the fetal brain. Curr
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91. Glenn OA. MR imaging of the fetal brain. Pediatr Radiol.
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92. Papile LA, Burstein J, Burstein R, Koffler H. Incidence and evolution
of subependymal and intraventricular hemorrhage: A study of infants
with birth weights less than 1,500 gm. J Pediatr. 1978;92:529–534.
93. Sarkar S, Bhagat I, Dechert R, Schumacher RE, Donn SM. Severe
intraventricular hemorrhage in preterm infants: Comparison of
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and grade 4 intraventricular hemorrhage. Am J Perinatol. 2009;26:
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94. Hadi HA, Finley J, Mallette JQ, Strickland D. Prenatal diagnosis
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95. Lerner A, Gilboa Y, Gerad L, Malinger G, Kidron D, Achiron R.
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96. Hiller LT, McGahan JP, Bijan B, Melendres G, Towner D.
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98. Martin R, Roessmann U, Fanaroff A. Massive intracerebellar hemorrhage in low-birth-weight infants. J Pediatr. 1976;89:290–293.
99. Ben-Chetrit A, Anteby E, Lavy Y, Zacut D, Yagel S. Increased middle
cerebral artery blood flow impedance in fetal subdural hematoma.
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100. Piastra M, Pietrini D, Massimi L, et al. Severe subdural hemorrhage due to minimal prenatal trauma. J Neurosurg Pediatr. 2009;4:
543–546.
101. Robinson MJ, Cameron MD, Smith MF, Ayers AB. Fetal subdural
haemorrhages presenting as hydrocephalus. Br Med J. 1980;281:35.
102. de Sousa C, Clark T, Bradshaw A. Antenatally diagnosed subdural
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104. Gunn TR, Mok PM, Becroft DM. Subdural hemorrhage in utero.
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105. Nogueira GJ. Chronic subdural hematoma in utero: Report of a case
with survival after treatment. Childs Nerv Syst. 1992;8:462–464.
106. Kiryabwire J, Chaseling R, Lang EW. Extensive in utero traumatic
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107. Bonnefoy O, Maugey-Laulom B, Diris B, Dallay D, Diard F. Fetal
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108. Demir RH, Gleicher N, Myers SA. Atraumatic antepartum subdural
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109. Hanigan WC, Ali MB, Cusack TJ, Miller TC, Shah JJ. Diagnosis of
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110. Kawabata I, Imai A, Tamaya T. Antenatal subdural hemorrhage
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Chapter 11
INTRACRANIAL CYSTS
Eran Bornstein ● Ana Monteagudo ● Ilan E. Timor-Tritsch
KEY POINTS
1. One of the most common and usually benign fetal
brain tetralogy pathology.
2. Easily detected due to its obvious anechoic appearance
at places that should not be located present.
3. Larger cysts may exert pressure on adjacent organs
causing displacement of structures or obstruct the
flow of cerebrospinal fluid.
4. Although mostly isolated, they can be associated
with other pathologies, therefore targeted neuroscan
and anatomy scan is warranted.
Intracranial cysts are relatively common findings
encountered in the prenatal sonographic assessment
of the fetal brain. The vast majority of these fluid collections (arachnoid and choroid plexus cysts) are of a
benign nature, remain clinically silent, do not evolve,
and regress spontaneously. When these lesions are not
associated with other fetal anomalies, they are compatible with normal life regardless of whether they require
postnatal treatment or not.
numerous differential diagnostic entities, as well as the
associated parental anxiety, clinically, these findings
present a dilemma in need of appropriate diagnosis and
counseling.
The differential diagnoses of intracranial cysts
encompass multiple etiologic and pathologic processes.
Advancements in imaging techniques, especially in fetal
sonography, have facilitated the workup of such cysts by
depicting their exact location, size, relationship to the
ventricular system, and midline structures. Additionally,
fetal sonography allows for evaluation of the presence of
solid components seen in cases of brain tumors or blood
clots and for performance of Doppler studies of blood
flow patterns in cases of vascular malformations, such as
an aneurysm of the vein of Galen. Nevertheless, imaging
studies may come short of distinguishing between some
of these lesions, which require histologic examination of
the cyst wall to establish the correct diagnosis.
chapter, we classify intracranial cysts based on the location of their origin into one of three groups: extra-axial,
intraventricular, and intraparenchymal ( Table 11–1 ).
1 , 2
Nevertheless, due to the
3
In this
CLASSIFICATION OF
INTRACRANIAL CYSTS
CYSTS OF EXTRA-AXIAL ORIGIN
This group of lesions consists of arachnoid cysts,
glioependymal cysts, endodermal cysts, cystic teratomas,
and dural separation due to dural sinus thrombosis.
Arachnoid Cysts
Arachnoid cysts are by far the most common lesion in this
group, and our review will focus on them.
Synonyms
None
Definition
3
Arachnoid cysts were first described by Bright in 1831
“serous cysts forming in connection with the arachnoid and
apparently lying between its layers.” Like other intracranial
cysts, arachnoid cysts are collections of cerebrospinal fluid
(CSF) on the brain surface bordered by a cyst wall.
Incidence
Arachnoid cysts account for 1% of all intracranial masses
in children.
an isolated single lesion. Multiple and bilateral arachnoid
cysts are unusual; familial occurrence has been reported in
only a few cases. The left side of the brain is affected more
commonly, and a male predominance with a 2:1 male-tofemale ratio has been shown.
2 – 4
They usually occur in a sporadic fashion as
5 – 8
P athogenesis
The exact pathogenesis is not clear, but it is thought to
develop mostly in the second and third trimesters. Arachnoid
cysts are usually benign, congenital, space-occupying
lesions with a cavity that is entirely surrounded by a transparent arachnoid membrane. These collections of CSF are
located within the layers of the arachnoid membranes and
as
352
Chapter 11 Intracranial Cysts
Table 11–1. CLASSIFICATION OF INTRACRANIAL CYSTS
Extra-axial Cyst Intraventricular Cyst Intraparenchymal Cyst
Arachnoid cyst Choroid plexus cyst Periventricular pseudocyst
Glioependymal cyst Choroid plexus hemorrhage Cystic periventricular leukomalacia
Endodermal cyst Porencephalic cyst
Dural separation Cystic brain tumor
Cystic tumors (teratoma) Holoprosencephaly
Vascular malformations Schizencephaly
may or may not communicate with the subarachnoid space.
Postnatally, they usually are the result of head trauma,
which provokes a proliferation of fibroblasts that form a
loculated cyst within the leptomeninges. These can enlarge
because the fluid within (CSF) is trapped and can only
increase. As a congenital lesion, the cause is less certain, but
the prevailing theory is that an arachnoid cyst is a disturbance of the mesencephalic neural crest, the origin of the
meninges, which forms a splitting of the primordial membrane into which fluid accumulates and becomes loculated,
analogous to a dissecting aneurysm. Whereas a cleft may
form during this period, it does not necessarily fill with fluid
to separate the two leaves until later in gestation or even
postnatally; hence, it is plausible that it would not be identified in the second trimester by neuroimaging, because it
may be detectable only microscopically at that time.
Etiology
An arachnoid cyst may present as a primary or an acquired
lesion. Primary cysts commonly arise from an abnormal
developmental process of the leptomeningeal formation,
whereas acquired arachnoid cysts (secondary cysts) generally result from entrapment of CSF within arachnoid
adhesions following in utero hemorrhage, infection, or
9 – 13
trauma.
Pathology
On histologic examination, the cyst wall is lined with collagen and cells of the arachnoid matter (meningothelial
cells). Electron microscopic findings confirm that the
origin of these cysts is arachnoid cells and not epithelial
14
Immunohistochemical markers have also been used
cells.
to differentiate arachnoid cysts from epithelial cysts. The
cells lining the arachnoid cyst are not ciliated and do not
stain with antibodies against glial fibrillary acidic protein
(GFAP), S-100, transthyretin, and carcinoembryonic antigen (CEA).
15
Associated Anomalies
Arachnoid cysts usually present as isolated lesions.
Several central nervous system (CNS) anomalies have
been described in association with them. These include
agenesis of the corpus callosum, absent septum pellucidum, deficient cerebellar lobulation, Arnold-Chiari type
I malformation, malformations of cortical development,
and arteriovenous malformation.
16
We believe interhemispheric cysts that present in fetuses with commissural
anomalies are probably not true arachnoid cysts but rather
cystic processes that develop from an abnormal meninx
that cause by themselves the defect, as they block the pathway of the axonal fibers through the midline. Non-CNS
malformations associated with arachnoid cysts are tetralogy of Fallot, sacrococcygeal tumor, and neurofibromatosis type I.
11 , 12 , 17 – 19
In addition, a few case reports point to
the possible association of arachnoid cysts with nonchromosomal syndromes, such as distichiasis-lymphedema and
Mohr syndrome, as well as trisomy 12q24.31.
20 – 22
However,
the strength of this association is questionable and may
suffer from publication bias due to the limited number of
case reports.
Risk of Recurrence
Generally, the finding of an arachnoid cyst is not thought
to represent an increased risk for future pregnancies.
However, arachnoid cyst is associated with a few hereditary conditions that confer increased risk of recurrence
mostly in an autosomal recessive or an X-linked pattern.
Aicardi syndrome, for example, is a rare X-linked dominant syndrome that includes agenesis of the corpus callosum, interhemispheric cyst, choroidal anomalies, and
infantile seizures ( Figure 11–1A ).
Sonographic Diagnosis
Most of the arachnoid cysts are sonographically detectable in the second or third trimester, which is consistent
with the belief that these lesions only develop around
this time. Prenatal diagnosis before 20 weeks’ gestation
is uncommon. In one of the largest series evaluating
fetuses with arachnoid cysts, there were no cases diagnosed prior to 20 postmenstrual weeks. Moreover, in this
series 55% of the arachnoid cysts were diagnosed between
20 and 30 postmenstrual weeks and 45% only after the
30th week despite an earlier scan.
trimester sonographic diagnosis coupled with histologic
2
Nevertheless, first
Chapter 11 Intracranial Cysts
BA
353
Figure 11–1.
hemispheres. (B) A midcoronal section localizes the cyst between the hemispheres in the longitudinal sulcus. The exact localization of this arachnoid
cyst was in the suprachiasmatic area. In spite of the favorable counseling, the patient elected for termination of the pregnancy. (Courtesy of Leibovitz
Zvi Haifa, Israel.)
confirmation of an arachnoid cyst has been described
( Figure 11–1 ).
Arachnoid cyst at 16 postmenstrual weeks. (A) Axial plane showing the 0.7 × 0.54 cm cystic structure between the frontal lobes of the
1 , 23
interventricular area. They found 22.2% of the cysts to be
located at the infratentorial area.
2
The characteristic sonographic appearance is that
of a sonolucent cystic mass with a thin, smooth wall
( Figures 11–2 to 11–9 ). Arachnoid cysts do not communicate with the lateral ventricles (unlike some of the
intraparenchymal cysts or lesions, such as porencephaly,
dorsal cysts of holoprosencephaly, and schizencephaly).
In severe cases, secondary hydrocephaly may be the
result of an obstruction in the flow of CSF due to the
mass effect. Most arachnoid cysts are supratentorial,
with ∼50% to 65% located in the middle cranial fossa, 5%
to 10% in the suprasellar cistern, 5% to 10% in the quadrigeminal cistern, 5% spread along the convexities, and
only 5% to 10% in the posterior fossa at the level of the
cerebellopontine angle and the cisterna magna. PierreKahn and Sonigo
2
published the largest series including
54 patients with arachnoid cysts. Based on their experience, 63% of the cysts were supratentorial, mostly intrahemispheric (25%), with few in the base, suprasellar, or
Differential Diagnosis
The differential diagnosis of an arachnoid cyst includes other
extra-axial lesions, as well as intraparenchymal or intraven-
9 , 10
tricular cystic lesions, as displayed in Table 11–1 . With the
exception of brain cystic tumors, which may be heterogeneous and contain solid components, all other lesions are
sonolucent fluid cystlike masses that can be associated with
secondary hydrocephaly due to a mass effect. In experienced
hands, ultrasound (US) can distinguish between the different groups of intracranial cysts. For example, porencephalic
cysts can be seen in the brain parenchyma and communicate with the ventricles and subarachnoid space.
Malformations of the vein of Galen have turbulent flow, which becomes evident using two- (2D) or
three-dimensional (3D) color or power angiography.
The sonolucent structure of the dilated vein of Galen does
24 – 27
*
*
A
Figure 11–2. Interhemispheric arachnoid cyst (*) associated with agenesis of the corpus callosum in a fetus at 22 weeks of gestation. (A) Axial view
showing typical ventricular colpocephaly with a sharp shape of the anterior horn ( arrow ) . (B) Coronal view. The interhemispheric fissure is continuous
with the arachnoid cyst due to agenesis of the corpus callosum. (C) Median plane fails to show the corpus callosum ( arrows ); note also the presence of
a severely dysgenetic vermis ( arrowhead ).
BC
*
354
Chapter 11 Intracranial Cysts
A
F-1
B
Rt Obl-2 Rt Obl-1 Med- Lt Obl-1
Figure 11–3. Transvaginal brain study of a fetus at 25 postmenstrual weeks showing a quadrigeminal cistern arachnoid cyst. (A) Serial coronal sections
from frontal–1 to occipital–2 (F-1 to O-2), with F-1 and frontal–2 (F-2) section showing the parenchyma of the frontal lobes. Midcoronal–1 (MC-1) to
midcoronal–3 (MC-3) shows the midline anechoic cyst. In occipital–1 (O-1), the cyst can be seen slightly impinging on the posterior lobe of the brain.
(B) Median (Med) and right and left oblique (Rt. and Lt. Obl) sections showing the extended and exact location of the cyst. Right oblique–1 and –2 (Rt.
Obl-1 and -2) show the normal right cerebral hemispheres. Note that there is no dilation of lateral ventricles. On the median section, the arachnoid cyst
is seen below the tail of the corpus callosum extending almost to the cranial bone. On left oblique–1 (Lt. Obl-1), more of the cyst is seen extending all
the way to the outer surface of the brain. This fetus has a normal corpus callosum; therefore, the prognosis is good.
F-2 MC-2 MC-3 O-1 O-2MC-1
not communicate with the ventricles or the subarachnoid
space and is located in the area of the quadrigeminal
plate cistern ( Figures 11–10 and 11–11 ). The aneurysm
probably represents a remnant of the embryonic median
prosencephalic vein. The diagnosis is generally made
postnatally, and the clinical signs include cyanosis, systolic murmur, cardiomegaly, and increased pressure with
hydrocephaly due to obstruction of the sylvian aqueduct
by the dilated aneurysm. In severe cases, nonimmune
hydrops fetalis may result from severe high-output congestive heart failure. Gerards and colleagues
28
described
their experience with two cases of aneurysm of the vein of
Galen. Their experience suggests that Doppler studies, 3D
sonography, and magnetic resonance imaging (MRI) may
be used to evaluate for prognostic factors, such as drainage
and secondary damage.
Chapter 11 Intracranial Cysts
355
QP
AB
Figure 11–4. Images of a large quadrigeminal plate arachnoid cyst at 26 postmenstrual weeks. (A) Median section showing the displacement of a
quadrigeminal plate (QP) and the vermis of the cerebellum (V). (B) Midcoronal section showing the symmetrical position of the cyst displacing the
hemispheres.
Fetal brain tumors are extremely rare, have a heterogeneous pattern, are usually within the brain parenchyma, and may communicate with the ventricles.
Teratomas are probably the only tumor that may appear
as a completely cystic intracranial extra-axial neoplasm.
Cassart et al
29
published their experience with US and
MRI of fetal intracranial tumors. Of 13 teratomas in their
series, 12 had a significant cystic component, and few
were completely cystic. These cystic components correspond to necrotic lesions and were extremely uncommon in other types of tumors. In a different series of
fetal brain tumors, the authors diagnosed seven cases of
brain tumors, of which six were confirmed postnatally.
One case of a supratentorial arachnoid cyst was mistaken
for a teratoma with cystic components. Out of the six
cases of suspected teratomas, one was revealed to be a
glioblastoma, one an arachnoid cyst, and one a primitive neuroectodermal tumor. The authors concluded that
prenatal ultrasonography is a useful tool to identify any
intracranial space-occupying lesion >10 mm, with 86%
specificity. As expected, the accuracy of US in diagnosing the tumor’s histologic type was limited (57%).
a more detailed discussion and images of fetal CNS
tumors, see Chapter 13 .
Other extra-axial cysts, such as glioependymal and
endodermal cysts, are extremely rare and cannot be
distinguished sonographically from arachnoid cysts.
Glioependymal cysts, also called ependymal cysts, choroidal epithelial cysts, neuroepithelial cysts, and epithelial
cysts, have a glioependymal lining that distinguishes them
from arachnoid cysts histologically. They may be located
both extra-axially and intraparenchymally and have been
reported to be detected in association with agenesis of the
corpus callosum.
31
This lesion is thought to arise from displaced neuroectodermal tissue most closely resembling the
area forming the tela choroidea and may also have a heterogeneous sonographic appearance. Like arachnoid cysts,
V
these lesions can grow and reach significant proportions.
Several reports describe the detection of glioependymal
11
cysts in fetuses undergoing neurosonographic evaluation
or brain MRI for the evaluation of ventriculomegaly.
31
32 , 33
The authors stressed the importance of considering this
entity in the differential diagnosis of fetal cystic brain
lesions, especially when callosal abnormalities coexist.
Endodermal cysts are extremely uncommon congenital
lesions that are rarely diagnosed prenatally. Most cases are
located in the spinal canal, and of the intracranial ones,
most are located in the posterior fossa.
34
Dural separation is a benign, mostly isolated finding
that may appear as a “cystlike” structure in the extra-axial
space of the brain.
Thrombosis of the dural sinus and thrombosis of
the torcular herophili following a thrombotic event are
rare events that are thought to result from trauma, dural
sinus malformation, or a genetic thrombophilia. The
diagnosis and management may be difficult, as this lesion
may mimic an intracranial tumor and display both solid
30
For
and cystic components. In utero resolution of the lesion
was reported in a few cases that had favorable outcome
(after an 18-month follow-up).
colleagues
37
reported their experience based on six cases
35 , 36
Laurichesse Delmas and
of dural sinus thrombosis. They found that sonographic
evidence of brain damage, cardiac failure, increased size
of the thrombus, and secondary brain ischemic damage
were associated with a poor outcome, whereas findings
of either partial or total regression, as well as the absence
of fetal decompensation, are considered good prognostic
factors associated with a favorable outcome. They further
concluded that based on the limited data available, the
outcome in cases in which the thrombus did not decrease
in size and there was no fetal decompensation or brain
anomaly could not be predicted. Our group had evaluated
three cases in which thrombus of the torcular herophili
was diagnosed on prenatal US. Separation of the dura with
356
Chapter 11 Intracranial Cysts
Rt
ABC
Rt
DEF
Figure 11–5. Bilateral cysts at 32 postmenstrual weeks. The working diagnosis based on the sonographic evaluation was bilateral choroid plexus cysts.
(A) “Horizontal”” section. The cysts are marked by arrows; the right is larger than the left. (B) Posterior angled “horizontal” section. The arrow points
to the larger right–sided cyst. (C) Left oblique–1 section. Note the slightly dilated posterior horn and the smaller cyst ( arrow ) below the choroid plexus.
(D) Midcoronal–1 section. Note that the anterior horns are slightly dilated. (E) Midcoronal–2 section. The cyst on the right side is shown. T, thalamus.
(F) Occipital–1 section. The larger right-sided cyst is seen extending posteriorly even on this section. C, cerebellum. The neonate was born at term. The
MRI images suggested the diagnosis of arachnoid cyst rather than cyst arising from the choroid plexus.
Lt
TT
Lt
CP
T
C
C
a cystlike area at the level of the torcular herophili containing a focus of clotted blood could be detected on a detailed
sonographic evaluation. These findings were supported
by a fetal MRI and further confirmed on the post mortem
examination.
38
For an illustrative case of thrombosis of the
torcular herophili, see Chapter 10 , Figures 10–12 , 10–13 ,
10–14 , 10–16 , and 10–18 .
It is extremely hard to differentiate arachnoid cysts
that are located in the posterior fossa from megacisterna magna (MCM) or Dandy-Walker malformation.
Nevertheless, an attempt to distinguish between them is
important because of the significant difference in the outcomes of these conditions. The hallmark of this lesion is
a cyst compressing the cerebellum against the brainstem
( Figure 11–12 ), with the vermis remaining intact, whereas
in MCM, there are no signs of compression, and in
Dandy-Walker malformation, the vermis is either absent
or hypoplastic. The distinction between these conditions
can be established by identifying the normally formed
fourth ventricle and the presence of the complete cerebellar vermis. In these cases, we recommend visualizing the
median plane (either by transvaginal US or by 3D reconstruction) in order to evaluate the size of the cerebellar
vermis, which may be displaced by the cyst resembling
a Dandy-Walker malformation. Hogge and colleagues
22
reported a case of an infratentorial posterior fossa arachnoid cyst that was associated with an unbalanced X;9
translocation. In one of our cases ( Figure 11–13 ), the first
US at 15½ postmenstrual weeks was completely normal;
however, at 28 postmenstrual weeks, a cyst of the posterior fossa was imaged, and at 31 postmenstrual weeks, it
appeared like a Dandy-Walker malformation. Postnatal
MRI and computed tomography (CT) scan confirmed the
diagnosis of a posterior fossa arachnoid cyst.
Chapter 11 Intracranial Cysts
T
T
C
G
I
H
Figure 11–5. (continued) (G) Slightly right paramedian section notes the thin wall of the cysts in the right lateral ventricle. This plane was obtained
along the white line transecting the brain in Figure 11–5H . (H) “Horizontal” section. Note that the anterior horns (AH) are not dilated and that the right
thalamus (T) is pushed slightly forward. (I) Coronal section through the two cystic structures and the cerebellum (C).
C
357
Implications for Targeted Examination
When managing a fetus with an arachnoid cyst, the exact
location and the effect on the brain structures in its
immediate vicinity should be determined. Our practice
is to perform a targeted detailed neurosonographic
examination, preferably using a high-frequency transvaginal probe to scrutinize the brain. The focus is on the
exact location and size, the relationship to the ventricles,
and the presence of any associated intracranial malformations or secondary anomalies. We also follow up these
cases longitudinally with US and consider a brain MRI,
L
L
A
Figure 11–6. Interhemispheric arachnoid cyst at 21 postmenstrual weeks affecting the corpus callosum. (A) Three-dimensional (3D) orthogonal
planes: coronal (box A), sagittal (box B), axial (box C). Box D displays inversion rendering of the lateral ventricles (L) and the arachnoid cyst ( arrow ) . (B)
3D power Doppler study. The planes are the same as in Figure 11–6A . Box D displays the short pericallosal artery ( arrow ).
which may be valuable in detecting additional anomalies (specifically, migrational disorders in places distant
to the cyst),
16
as well as providing further reassurance.
We obtain a detailed fetal scan looking for extracranial
anomalies, a fetal echocardiogram, genetic counseling,
and possibly genetic testing for women who are diagnosed with fetal extra-axial cyst.
Prognosis
The clinical manifestations are directly related to the size
of the cyst and its location within the brain. Small cysts
B
358
Chapter 11 Intracranial Cysts
A
Figure 11–7. 3D tomographic representation of the interhemi-
spheric arachnoid cyst. Same case as in Figure 11–6 . (A) Sagittal
planes along the lines seen in the first box. (B) Coronal planes
along the lines seen in the first box. (C) Axial planes along the lines
seen in the first box.
generally present as incidental findings, whereas larger
cysts may come to attention during a workup of seizures,
headache, hydrocephaly, or focal neurologic signs, which
are caused by the mass effect.
39
Approximately 60% to
80% of arachnoid cysts are a symptomatic. Even a large
cyst producing pressure on brain structures may remain
asympomatic.
circumference and calvarial asymmetry in severe cases of
hydrocephaly.
1
In infants there may be increased head
7
The prognosis of fetuses with arachnoid cysts is
mostly dependent on the presence of associated congenital or chromosomal anomalies. As mentioned before, the
prognosis is generally good even in those cases requiring
drainage of a hydrocephaly in the neonatal or infancy
period.
40 – 43
3
rience distinguishing between interhemispheric cystic
lesions that are related to physiologic median brain structures and cysts from pathologic fluid collections. In their
sonographic evaluation, they used an evaluation of the
cyst’s location, size, and change in size over time, as well
as associated anomalies. They detected 12 fetuses with
interhemispheric cysts that were related to median structures (enlargement of the cavum septi pellucidi [3 fetuses]
or of the cavum Vergae [2 fetuses] and cysts of the velum
interpositum [7 fetuses]). These cysts were unilocular,
ranging from 10 to 30 mm, and were not associated with
overt fetal anomalies. Moreover, the cysts resolved in
five cases, remained stable in the rest, and all had normal
pediatric follow-up. In contrast, seven cases that were
diagnosed as “pathologic lesions” were significantly larger,
ranging from 10 to 80 mm, and grew over time. In five
B
C
of these cases, associated intracranial anomalies, such
as partial or total agenesis of the corpus callosum and
overt hydrocephaly, were present. The neonatal outcome
in these cases was also significantly worse and included
one elective termination of pregnancy, one infant death
at 4 months of age, two neonates with neurodevelopmental delay, and three that appeared to be neurologically
intact at a mean follow-up of 43 months. Cyst shunting
was necessary in five of six cases.
3
In a different report,
five fetuses who were diagnosed with isolated cyst of the
cavum veli interpositi had a normal neurologic and neurosonographic follow-up.
44
Other investigators reached
similar findings, supporting the conclusion that isolated,
“benign-appearing” cysts of the median structures carry a
favorable neonatal outcome.
Obstetric Management and Prognosis
Management includes the workup that we previously
described. The mode of delivery should not be affected
by the presence of an arachnoid cyst unless hydrocephaly
does not permit vaginal delivery. Management of neonates
with arachnoid cysts varies based on their symptoms and
the degree of hydrocephaly. Most arachnoid cysts that are
found incidentally can be managed expectantly and have
favorable outcome. However, patients who are symptomatic should be regarded as surgical candidates. The surgical options for treatment include ventriculoperitoneal and
cystoperitoneal shunting, open or endoscopic fenestration, and stereotactic aspiration.
neurosurgical techniques and neuroendoscopy continue
41 – 45
Recent advances in
Chapter 11 Intracranial Cysts
359
Median plane
Rt
Ant
Ant
Rt
Ant
A
Rt
Ant
C
Ant
Anterior cerebral a.
Median plane
Rt. Parasagittal plane
Ant
Rt
Ant
Ant
Pericallosal a.
Median plane
B
Pericallosal A.
Ant.
Anteior
cerebral A.
Internal carotid A.
D
Cyst
E
Figure 11–8. An arachnoid cyst originating from the quadrigeminal plate at 23 postmenstrual weeks. (A) The septated cyst displacing the falx to the
right is shown by the coronal (box A), sagittal (box B), and axial (box C) planes. (B) Another set of orthogonal planes were selected to study the extent
of the lesion. (C) Color Doppler study. The picture in the active box (box B) highlighted by the frame is generated in the median plane ( dotted vertical
white line through boxes A and C). Only the anterior cerebral artery, but not the pericallosal artery, is seen (the latter should be evident in this plane).
(D) The plane is moved to the right. Now the active box (box B) is generated in the right parasagittal plane. In this plane, the pericallosal artery is clearly
detected. This proves that the corpus callosum is not destroyed by the cyst. The dotted vertical white line was kept to mark the median plane. (E) A 3D
color flow rendering of the anterior cerebral and pericallosal arteries. The approximate place of the arachnoid cyst is marked.