Spontaneous development of a de novo suprasellar arachnoid cyst - Case report
Arachnoid cysts are commonly thought to arise from either congenital defects or trauma. In this article the authors report the spontaneous development of a suprasellar third ventricular arachnoid cyst whose origin was not clearly congenital or traumatic. At the age of 4 months, the patient presented with hypertonia, and a magnetic resonance (MR) imaging study showed no abnormalities. At the age of 2 years, the boy presented with headaches and projectile emesis, symptoms that prompted further imaging studies. An MR image of the brain revealed a suprasellar cyst and obstructive hydrocephalus. The cyst was endoscopically fenestrated, which led to long-term symptom resolution.
J Neurosurg (6 Suppl Pediatrics) 104:426–428, 2006
J. Neurosurg: Pediatrics / Volume 104 / June, 2006
NTRACRANIAL arachnoid cysts are fluid-filled cavities
that arise within the arachnoid layer. They occur fairly
frequently, but are rarely found in the ventricles. The
cysts are often asymptomatic, and can remain undetected
for years. Thus, most opportunities to study the growth of
arachnoid cysts occur when a patient undergoes an imaging
procedure for an unrelated issue. The advent of more ad-
vanced imaging techniques has increased the frequency of
these findings, but they still remain rare. Furthermore, the
causes and dynamics of these cysts are not wholly under-
stood. The majority of arachnoid cysts are thought to be
congenital and to result from developmental abnormalities;
however, various physical insults have also been proposed
as possible instigators of their appearance and growth.
Other reports have indicated that arachnoid cysts can
spontaneously grow or resolve with no readily apparent
In this article we describe the spontaneous
de novo development of a suprasellar third ventricular
arachnoid cyst in a 2-year-old child. This is only the second
documented case of an arachnoid cyst whose origin was
not clearly congenital or traumatic, and it is the first such
case in which the lesion was located in the third ventricle.
The cyst caused obstructive hydrocephalus and was fenes-
trated endoscopically. The child has undergone follow-up
serial MR imaging for 4 years, and thus far has had no re
currence of hydrocephalus.
History. The child was examined in 1998, when he was 4
months of age, for an exaggerated startle reflex and hy-
pertonia. An MR imaging study performed at that time re-
vealed generous convexity of the cerebrospinal fluid spac
es, which was consistent with benign convexity fluid of
infancy (Fig. 1). No other abnormality was detected. The
lateral, third, and fourth ventricles were normal in size. The
infant was started on physical and occupational therapy
Presentation and Examination. During the 2nd year of
life, the boy began to experience frontal headaches and in-
termittent episodes of projectile emesis. He was examined
and the diagnosis was ventriculomegaly caused by an ob-
structive suprasellar arachnoid cyst that completely effaced
the third ventricle.
First Operation and Postoperative Course. At the time, a
ventriculoperitoneal shunt was inserted to treat the hydro
cephalus. After surgery, the patient reported a large reduc-
tion in headaches. There was improvement in his appetite
and gait, although his gait remained unsteady. Within a
month after sur
, the patient became irritable and com
bative, and suffered from low appetite and insomnia. An
MR image revealed a slightly smaller lateral ventricle ipsi
lateral to the shunt and a large third ventricular arachnoid
cyst (Fig. 2). The diagnosis of obstructive hydrocephalus
was made, and the patient was referred to our institution for
Spontaneous development of a de novo suprasellar
AARON F. STRUCK, B.S., MICHAEL J. MURPHY, B.S., AND BERMANS J. ISKANDAR, M.D.
Department of Neurological Surgery, University of Wisconsin, Madison, Wisconsin
Arachnoid cysts are commonly thought to arise from either congenital defects or trauma. In this article the authors
report the spontaneous development of a suprasellar third ventricular arachnoid cyst whose origin was not clearly con-
genital or traumatic. At the age of 4 months, the patient presented with hypertonia, and a magnetic resonance (MR)
imaging study showed no abnormalities. At the age of 2 years, the boy presented with headaches and projectile eme-
sis, symptoms that prompted further imaging studies. An MR image of the brain revealed a suprasellar cyst and ob-
structive hydrocephalus. The cyst was endoscopically fenestrated, which led to long-term symptom resolution.
KEY WORDS • obstructive hydrocephalus • suprasellar cyst • cyst formation •
Abbreviation used in this paper: MR = magnetic resonance.
Second Operation and Postoperative Course. The cyst was
treated using endoscopic fenestration and shunt removal.
The fenestration consisted of resecting the roof of the cyst
and opening its bottom into the suprasellar cistern—a pro-
cedure akin to a third ventriculostomy. The cerebral aque
duct was revealed when the cyst membrane covering it was
removed. An external ventricular drain was left in place for
a few days. Postoperatively, the patient suf
fered from tran-
sient episodes of photophobia, but his preoperative symp-
toms resolved. Computerized tomography and MR images
of the head showed that the cyst had resolved and that the
ventricles had significantly decreased in size (Fig. 3).
Intracranial arachnoid cysts have been implicated in a
variety of neurological problems. In particular, third ven-
tricular arachnoid cysts have been associated with hydro-
cephalus, seizures, developmental delays, and decreased
Yet often these cysts remain asymptomatic
and undetected. In fact, unless an imaging procedure is un-
dertaken for an unrelated issue, it is likely that an asympto-
matic arachnoid cyst will remain undiscovered for the en-
tire lifetime of the patient. As such, detailed studies of the
development of arachnoid cysts are rare. To date there are
only five cases of enlargement of arachnoid cysts that have
been documented using serial imaging techniques.
Arachnoid cysts are generally thought to be congenital or
caused by discrete events such as trauma or intracranial
In this patient, the cyst did not appear
to be congenital because an MR image obtained when he
was 4 months of age demonstrated normal ventricle size
and no obvious cyst. In addition, the patient’s parents de-
scribed no serious trauma or surgery during the child’s life.
The origin of this cyst thus remains obscure.
Several hypotheses have been proposed in an attempt to
explain the mechanism by which arachnoid cysts form, per-
sist, and enlarge. Starkmen, et al.,
proposed that congenital
arachnoid cysts originate from the splitting of the arachnoid
membrane. Recently, attempts have been made to support
Starkmen’s theory through experimental measures, includ-
ing an example of an arachnoid cyst in an intraarachnoid
Mechanisms proposed to explain the enlarge-
ment and persistence of cysts include secretion of fluid by
ependymal cells, fluid influx from an osmotic gradient, and
a one-way valve mechanism.
The valve mechanism has
been witnessed during endoscopic fenestration of arachnoid
cysts and has subsequently been gaining credence.
J. Neurosurg: Pediatrics / Volume 104 / June, 2006
. 1. Sagittal (left) and axial (center and right) MR images obtained when the patient was 4 months of age, dis-
playing no evidence of a cyst or of any enlargement of the third ventricle.
FIG. 2. Preoperative sagittal (left) and axial (right) MR images obtained when the patient was 2 years of age, reveal-
ing enlargement of the third ventricle due to a suprasellar arachnoid cyst. Note the indentation in the brainstem caused
by the cyst.
De novo arachnoid cyst
J. Neurosurg: Pediatrics / Volume 104 / June, 2006
The original insult leading to the formation of the cyst
might well be congenital yet imperceptible in the early im-
aging studies. However, the cause of the rapid enlargement
remains unknown. With the ubiquitous use of MR imaging,
more documented cases of symptomatic as well as asymp-
tomatic arachnoid cysts are surely forthcoming. Hopefully,
this body of data will elucidate these commonly idiopathic
and sometimes pathogenic cysts.
This is the first documented case of a suprasellar third
ventricular arachnoid cyst that formed spontaneously dur-
ing early childhood. The mechanism of cyst formation and
persistence is unclear. The lesion was successfully fenes-
trated endoscopically, resulting in a decrease in ventricle
size and resolution of the symptoms.
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Manuscript received June 1, 2005.
Accepted in final form March 1, 2006.
Address reprint requests to: Bermans J. Iskandar, M.D., Depart-
ment of Neurological Surgery, University of Wisconsin Hospital,
600 Highland Avenue, K4/832, Madison, Wisconsin 53792. email:
FIG. 3. Four-year postoperative sagittal (left) and axial (right) MR images demonstrating a significant decrease in the
sizes of the third ventricle and cyst.
A. F. Struck, M. J. Murphy, and B. J. Iskandar