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Congenital arachnoid cyst with unusual clinical radiological and pathological findings.

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Congenital Arachnoid Cyst
with Unusual Clinical, Radiological,
and Pathological Findings
Antonio Rosich-Pla, MD, Bernard H. Smith, MD, and Ranajit Sil, MD, PhD
Choroid plexus-like structures were found in the wall of a congenital frontotemporal arachnoid cyst in a 14-year-old
girl who presented with temporal lobe seizures since the age of 6. T h e temporal cortex beneath the cyst was
maldeveloped. The clinical, radiological, and pathological aspects of congenital arachnoid cysts are reviewed.
Rosich-Pla A, Smith BH, Sil R: Congenital arachnoid cyst with unusual clinical, radiological, and pathological
findings. Ann Neurol 2:443-446, 1977
Intracranial extracerebral fluid collections may be of
inflammatory, traumatic, or congenital origin. They
have variously been described as subdural hygromas
or hydromas, leptomeningeal cysts, arachnoid cysts,
and external hydrocephalus. Whether these cysts lie
between layers of the arachnoid (“intraarachnoid”),
between the arachnoid and pia (“subarachnoid”) o r
between the arachnoid and dura (“subdural hygroma”) is not always clear, even at operation [8, 91.
This communication reports an unusual case of congenital leptomeningeal cyst and reviews the pertinent
clinical, radiological, and pathological aspects.
A 14-year-old right-handed white girl was admitted to the
hospital in December, 1975, for investigation of uncontrolled temporal lobe seizures. The seizures had started at
the age of 6 years and were described as staring spells, each
lasting about one minute, during which the patient would
carry out automatic activities such as scratching and disrobing. The frequency had increased since puberty in spite of
treatment with primidone, 250 mg qid. Skull roentgenograms and brain scan were normal. The electroencephalogram showed recurrent sharp waves from the left anterior and
midtemporal areas with associated focal slowing in the
temporal area.
O n examination she had acnelike lesions on the face and
upper trunk. There was slight bulging of the left temporal
bone. Cranial nerve functions were intact except for congenital left ptosis and inconsrant npstagmus on extreme lateral
gaze to either side. Motor, sensory, and cerebellar functions
were normal. The deep reflexes were sluggish and the
plantar responses flexor.
Labomtory Tests
Pertinent laboratory results included unremarkable blood
and cerebrospinal fluid examinations. Pneumoencephalogtaphy showed shifting of midline structures to the right; the
From the Departments of Neurology and Pathology (Division of
Neuroparhology), State University of New York at Buffalo and
Edward J. Meyer Memorial Hospital, Buffalo, NY.
right lateral ventricle was slightly enlarged, and the left
temporal horn was elevated. There was some asymmetry of
the calvaria. CAT scan showed a large area of decreased
density deep in the left frontotemporal area. Bilateral
carotid angiography showed an avascular mass involving the
inferior left frontal lobe and extending into the medial and
inferior aspects of the temporal lobe (Fig 1).
Craniotomy in January, 1976, disclosed a left subfrontal
subdural cyst with extension toward the sylvian fissure.
Forty milliliters of fluid containing over 400 mg/dl of protein and 101 mgidl of glucose was removed. T h e temporal
cortex beneath the cyst was biopsied.
Pathology Report
The wall of the cyst consisted of a strip of poorly cellular
leptomeninges; in certain areas there was a papillary structure resembling choroid plexus (Fig 2). In adjacent brain the
cellular arrangement under low-power magnification resembled the granular layer of the cerebellum; at higher
magnification, swollen astrocytes and fully developed
neurons and round cells resembling neuroblasts were detected (Fig 3). N o hemorrhage or necrotic tissue was seen.
Follou ‘-up
The patient has been followed for one year since surgery.
During the first postoperative months she continued to have
frequent but more prolonged seizures.
A follow-up electroencephalogram in June, 1976, was
unchanged. CAT scan again showed a large radiolucent
lesion deep in the anterior and midtemporal areas on the left
side; i n the contrast-enhancement study the radiolucent area
appeared well defined, its margins delineated posteriorly by
the displaced left middle cerebral artery (Fig 4 ) . There was
very little change in appearance compared to the preoperative CAT study. An effort to add carbamazepine to her
primidone regimen to improve management of the seizures
failed because of severe allergic dermatitis. Since that atAccepted for publication May 16, 1977.
Address reprint requests to Dr Rosich-Pla, Edward J. Meyer
Memorial Hospital, Buffalo, N Y 14217.
Fig 2. C h o r d PlrXdls-Irke structuves i n the wall of the
cyst. ( H 6 E ; X 3 2 0 before -30% reduction.)
tempt [he patient has been relatively well controlled o n
primidone alone, 250 mg qid, with only one or two spells
occurring per month.
Fig 1 . Left carotid angiogram (antwoposterior and lateral
views) showing an auascular mass involoing the inferior
left f r o n d l o b e and extending into the medid and infrrior
aspects ofthe temporal lode.
Inflammatory and traumatic lep tomeningeal cysts
have been reported frequently, and their pathogenesis seems well understood. O n the other hand, congenital cysts have been the source of much confusion.
Cysts following inflammatory lesions of the leptomeninges result from adhesions trapping collections of cerebrospinal fluid. Traumatic leptomeningeal cysts in infancy and early childhood follow skull
fracture. The diagnosis can usually be made on the
basis of plain skull roentgenograms that show an irregular defect in the bone with scalloping of the margins and adjacent sclerosis. Taveras and Ransohoff
[13] postulated that such subjects have suffered an
initial (most commonly parietal) skull fracture with
associated dural tear; herniation of the underlying
arachnoid through this tear could permit the normal
intracranial pulse gradually to erode the bone edges.
Lende and Erickson [61 proposed the term growing
444 Annals of Neurology Vol 2 No 5 November 1977
Fig 3 . Round cells resembling neuroblasts and two matured neurons (center). ( H 6 E ; X320.1
skull fractures of childhood to stress the importance of a
F i g 4. Postoperutive CAT scan showing large area of
decreased density in the Left frontotemporal region.
skull fracture in the pathogenesis of the syndrome.
However, trauma is still a frequent antecedent in
other cases of leptomeningeal cyst in which skull fracture is not apparent radiologically. The role of trauma
in these patients is difficult to prove, and indeed the
cyst may have preceded the trauma.
Leptomeningeal cysts of developmental or congenital origin may occur in the supratentorial or infratentorial compartments. Below the tentorium, they may
occur anywhere in the posterior fossa but particularly
in the cerebellopontine angle and in the cisterna
magna. Supratentorially, the most common location is
in the middle fossa (sylvian area), but they may also
occur parasagittally or over the convexity. These congenital cysts have been considered intraarachnoid by
Starkman et a1 [12]: at autopsy in 3 of their cases,
congenital cysts in the sylvian area lay between two
membranes that were continuous at the margins of the
cyst with the arachnoid mater. Escourolle et a1 [3]
from a study of 6 cases arrived at the same conclusion.
Robinson [l11 presented evidence for a congenital
origin of leptomeningeal cysts in the temporal fossa.
He believed that the crucial pathogenic factor is
Case Report: Rosich-Pla, Smith, and Sil: Unusual Arachnoid Cyst
agenesis of the temporal lobe and that the fluid collection constitutes a secondary “external hydrocephalus”
and not a true cyst. H e proposed the termtemporullobe
ugenesis syndrome to include his own patients and many
cases previously described as chronic subdural hygromas or hydromas, arachnoid cysts, and other
Choroid plexus-like tissue (as was found in our
patient) has been reported [7, 81, though rarely, in the
walls of arachnoid cysts in the posterior fossa-further
evidence of their maldevelopmental origin. We have
been unable to find a previous report with such a finding in arachnoid cysts located above the tentorium.
The fluid in the cyst is clear o r slightly xanthochromic. Its chemical composition has been described
as that of normal cerebrospinal fluid [14J or, more
rarely, as being hyperproteinemic [2].
In infancy and early childhood the most common
clinical presentation of congenital cysts is enlargement of the head, often asymmetrical [ l , 2, 3, 141.
Transillumination is helpful in their detection. In
older children, adolescents, o r adults, supratentorial
cysts may present with the signs and symptoms of
increased intracranial pressure [ 1, 15 1. Such a pressure increase is particularly frequent in posterior fossa
cysts obstructing spinal fluid circulation with resulting
internal hydrocephalus.
Seizures are uncommon with congenital cysts [ 11I.
Two of Aicardi and Bauman’s [ 1] 12 patients and 3 of
the 10 reported by Vigoreaux et a1 [14] presented
with seizures, but in only 1 were these described as
of temporal lobe type. At times the cyst may be silent,
being discovered incidentally at autopsy [ 12 I. Case 2
of Starkman et a1 [ 121, like our patient, had left ptosis
that was thought to have been present since birth.
Their patient died at age 72 years of bladder carcinoma, and at autopsy an unsuspected leptomeningeal cyst compressing the third nerve was found.
The diagnosis of arachnoid cyst located in the sylvian fissure is best accomplished radiographically.
Plain skull roentgenograms may reveal the cranial
vault to be enlarged, rounded, and thinned compared
with the opposite side [ 9 ] ,and the lesser wing of the
sphenoid may be elevated [ 111. These changes may
be subtle and go unnoticed, as in our patient, in whom
the skull series was initially read as normal and only
later, at the time of pneumoencephalographp, noted
to show “some asymmetry of the calvaria.” Angiography may demonstrate an avascular extracerebral
mass, and pneumoencephalography may show dilatation of the ventricular system, a lateral shift of midline
structures, or elevation of the ipsilateral temporal
horn. Air does not enter the cyst itself unless it is
tapped directly during ventriculography “9, 161.
Congenital arachnoid cysts appear on CAT scan as
sharply defined lucent lesions indenting the brain,
displacing middle structures, and causing bulging of
446 Annals of Neurology
Vol 2
No 5
the overlying calvaria [ 101. Subdural hygromas may
appear similar to a subdural hematonia except that,
because the fluid has absorption values in the range of
cerebrospinal fluid [ 5 ] , the abnormal area between
the normal gray matter and the bone is of decreased
rather than increased density.
In the present case, the appearance of the lesion on
CAT scan is not typical for a simple arachnoid cyst or a
subdural hygroma. tndeed, the first scan was interpreted as most consistent with astrocytoma. Part of
the radiolucent area seen in the CAT scan may represent an associated intraparenchymatous nonneoplastic cyst (“closed porencephaly” as described by Handa
and Bucy [4]),
separated from the arachnoid cyst by a
layer of hypoplastic cortex. Escourolle et a1 [ 3 ]have
emphasized that the frequency of congenital anomalies or cerebral malformations associated with
arachnoid cysts is low in cases studied surgically but
increases when autopsy verification is possible. In addition, the cyst may be multiloculated and only partially evacuated at the time of surgery. Both reasons
may account for the paucity of changes between the
preoperative and postoperative CAT scans.
1. Aicardi J , Bauman F: Supratentorial extracerebral cysts in
infants and children. J Neurol Neurosurg Psychiatry 3X:5768, 1975
2. Anderson FM, Landing B H : Cerebral arachnoid cysts in infants. J Pediarr 69:88-96, 1966
3. Escourolle R, Hauw JJ, Hcrvt d e Sigalony JP, e t al: Lcs kystes
arachnoldicns de I’adulte: Orude neuropathologiquc dc 6 observations. Ann Anat Pathol (Paris) 19257-274, 1974
4. Handa H, Bucy P: Benign cysts of the brain simulating brain
tumor. J Neurosurg 13:489-498, 1956
5 . Kistler JP, Hochberg FH, Brooks BR, ct al: Computerized
axial tomography: clinicopathologic correlation. Neurology
(Minneap) 25:201-209, 19?5
6. Lende RA, Erickson TC: Growing skull fractures of childhood.
J Neurosurg 18:479-489, 1961
7 . Lewis AJ: Infantile hydrocephalus caused by arachnoid cyst. J
Neurosurg 19431-434, 1962
8. Little JR, Gomez MR, MacCarty CS: Infratentorial arachnoid
cysts. J Neurosurg 39380-386, 1973
9. Matson DD: Benign intracranial cysts, in Neurosurgery of
Infancy and Early Childhood. Second edirion. Springfield, IL,
Charles C Thomas, 1969, chap 10
10. Peterson HO, Kieffer SA: Computed tomography of the head,
in Baker’s Clinical Neurology. New York, Harper & Row,
1976, vol 1, chap 2
11. Robinson RG: Temporal lobe agenesis syndrome. Brain
87:87-106, 1964
12. Srarkman SP, Brown TC, Livell EA: Cerebral arachnoid cysts. J
Neuroparhol Exp Neurol 17:484-500, 1958
13. Taveras JM, Ransohoff J: Leptomeningeal cysts of the brain
following trauma with erosion of the skull. J Neurosurg
10:233-242, 1953
14. Vigoreaux RP, Choux M, Baurand C: Les kystes arachndidiens
congbnitaux. Neurochirurgie 9:169-187, 1966
15. Weinman DF: Arachnoidal cysts insylvian fissure ofthe brain. J
Neurosurg 22:185-187, 1965
16. Wilson CB, Bertan V: Cerebral leptomcningeal cysts of developmental origin. Am J Roentgen01 98:570-574, 1966
November 1077
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radiological, pathologic, clinical, arachnoid, unusual, congenital, findings, cysts
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