Endodermal
Epithelial Extending
Cyst into
—
Osamu Departments
HIRAI,
the Fourth
Case
Akinori
of Neurosurgery
in the Prepontine
Cistern
Ventricle
Report—
KONDO
and
Hirofumi
KUSAKA*
and *Neurology, Kitano Medical Research and Hospital, Osaka
Institute
Abstract The authors report a case of epithelial cyst, which recurred 32 years after the initial surgical treatment. Computed tomography showed no abnormality, but magnetic resonance (MR) imaging clearly demonstrated a well-demarcated mass in the prepontine cistern, extending into the fourth ventricle. The lesion showed extreme hyperintensity compared with the surrounding brain on both the T1and T2-weighted images. The ultrastructural features of the cyst suggested an endodermal origin. MR im aging and electron microscopy are essential for correct diagnosis and exact pathogenetic identification of intracranial cystic lesions. Key words: electron
epithelial
cyst,
endodermal
origin,
recurrence,
Introduction
Case
was admitted cranial nerve
pareses and moderate motor weakness and hypes thesia of the left lower extremity. He had undergone surgical removal of a cystic mass located in the fourth ventricle at the age of 21, because of pro
Received
right abducens September present
imaging,
gressive motor weakness of the left lower extremity. Pre and postcontrast computed tomographic (CT) scans on admission revealed no abnormalities. Cerebral angiography and myelography were also normal. However, MR imaging disclosed a well demarcated irregular mass with marked hyperinten sity signals on both the T, and T2-weighted images. The mass was located on the left side of the prepon tine cistern and apparently extending dorsally through the pons into the fourth ventricle (Fig. 1). A left suboccipital craniectomy disclosed a cystic mass in the subarachnoid space between the fifth and tenth cranial nerves. The cyst surface was smooth, and a puncture yielded about 10 ml of creamy viscous fluid. The extremely thin membranous cyst wall was almost totally removed, but the part in the fourth ventricle was inaccessible. The cyst fluid con tained 81 mg/dl of cholesterol and 566 mg/dl of
Report
On June 21, 1989, a 53-year-old male with persistent right fifth to eighth
Author's
resonance
cyst wall burst perioperatively, and as the yellowish viscous content immediately entered the cerebrospi nal fluid, no specimen of the cyst wall was obtained. He remained well until 1987, when he noticed pro
Cysts lined by a single layer of epithelium may occur anywhere in the central nervous system (CNS).2,4'''''"' Since various pathological entities are included in this disease, electron microscopic examinations may often be required for precise diagnosis." Here, we describe a recurrent cyst of endodermal origin, located in the prepontine cistern and extending into the fourth ventricle. The characteristics and diag nostic value of magnetic resonance (MR) imaging for epithelial cyst are also discussed.
gressive
magnetic
microscopy
25,
address:
and facial 1990; O. Hirai, Japan.
nerve Accepted M.D.,
pareses. October Department
The 26,
1990
of Neurosurgery,
Faculty
of Medicine,
Kyoto
University,
Kyoto,
total protein. The albumin/globulin ratio was 0.08, lower than that in serum. Light microscopy showed that the cyst wall was lined by a single layer of cuboidal epithelium con taining numerous granules with positive periodic acid-Schiff (PAS) staining (Fig. 2). Ultrastructural ly, the epithelium contained ciliated and non-cili ated cells. The latter cells contained numerous free ribosomes and were slightly darker. Microvilli on the luminal surface of the non-ciliated cells were coated by electron-dense materials. Several func tional complexes and well-developed interdigitations were noted between adjoining cells. The underlying connective tissue was clearly separated from the epithelium by a distinct continuous basement mem brane (Fig. 3). The postoperative course was uneventful, except
Fig. 3
Electron micrograph, showing ciliated and non-ciliated cells, numerous free ribosomes, and electron-dense materials coating the lumi nal surface of the non-ciliated cells. There are also well-developed interdigitations between adjacent cells. Bar = 1 um.
for mild meningitis successfully treated by in trathecal antibiotics. He was discharged with no addi tional neurological deficit and improved motor weakness and hypesthesia of the left lower extremity. Postoperative MR images showed disappearance of the cyst in the prepontine cistern but a small remnant in the fourth ventricle. One year postoperatively, he was working normally.
Discussion Fig. 1
Fig. 2
T, (left) and T,-weighted (right) MR images, showing a well-demarcated high-intensity mass with an irregular shape in the left prepontine cistern, apparently extending into the fourth ventricle.
Light
micrograph,
lined
by
numerous x 200.
demonstrating
columnar PAS-positive
epithelial
the cyst wall cells
granules.
containing PAS
stain,
Epithelial cysts occur anywhere in the CNS, and are described by various terms including colloid cyst, neuroepithelial cyst, paraphyseal cyst, ependymal cyst, choroidal epithelial cyst, and enterogenous cyst. 1,1,1,131Previously, a single etiology for these cysts was considered, but now several causes are recognized depending on the site and ultrastructural features.','," The epithelial cysts may become symptomatic at any age, but most are considered to form in the fetus. In this case, simple evagination of a fourth ven tricular cyst derived from epithelial lining of the epen dyma or choroid plexus might also have caused the prepontine lesion. However, MR images showed that the intraventricular and extraventricular parts were not connected by the foramen of Luschka, but rather through the pontine parenchyma. lihara et al." recently reported an epidermoid cyst traversing the pons into the fourth ventricle through In this case, no such defect was found suboccipital craniectomy.
a small defect. by a unilateral
The initial neurological symptoms of right ab ducens and facial nerve pareses strongly suggested the primary focus in the prepontine cistern. The first operation, 32 years previously, only detected the in traventricular part of the cyst. However, this does not exclude a prepontine lesion since the approach was a midline suboccipital craniectomy. Therefore, it is unlikely that the extraventricular part of the cyst developed from the fourth ventricular cyst. Another possibility is that the extraventricular part is derived from heterotopic neuroglial nests.") Electron microscopic study of the cyst showed the epithelium containing both ciliated and non-ciliated cells, electron-dense materials coating the microvilli on the luminal surfaces of the non-ciliated cells, and a distinct continuous basement membrane and promi nent interdigitations along the lateral cell borders. These features suggest an endodermal origin, especially the respiratory epithelium, rather than a neuroepithelial origin, because a basement mem brane is not common in the ependyma, cilia and in terdigitations at the lateral borders of adjacent cells are not constant features of the choroid plexus, and electron-dense materials have never been seen in the normal CNS.2,5> The neural tube closes cranially at Carnegie stage 11 (about 24 days) and caudally at stage 12 (about 26 days), followed by thickening of the wall to form the brain and spinal cord. Therefore, any migration of endodermal tissue into the CNS should have oc curred by then. The introduction of CT has made the diagnosis of intracranial cystic lesions much easier. Most epithe lial cysts appear isodense or slightly hyperdense compared with surrounding brain parenchyma, because the cyst fluid contains protein, ionic cal cium, iron, and other metals. 1,121However, CT pro vided no information in this case as the cyst was perfectly isodense and unenhanced by the contrast injection. MR imaging now provides much useful informa tion about intracranial cystic lesions.') Coronal and sagittal images allow better visualization of the anatomical relationship with the surrounding neural structures. Cysts containing fluid almost identical with cerebrospinal fluid appear as low-intensity signals on T1-weighted images and high-intensity signals on T2-weighted images, using routine pulse se quences.' Recently, Maeder et al.") demonstrated the heterogeneous MR appearance of colloid cysts of the third ventricle, despite the homogeneous his tology. They suggested that high-signal intensities on T1-weighted images correlated with high choles terol content, but metals did not affect signal inten
sities. Cyst fluid analysis in this case also could not explain the extremely high-signal intensities on both the T1 and T2-weighted images. Such variation in MR features is compatible with heterogeneous histo pathogenesis. Craniotomy is the best surgical treatment for di rectly accessible benign epithelial cysts. Recent developments in stereotactic procedures allow safer and less traumatic cyst evacuation. However, a number of patients have required subsequent craniotomy to remove residual or recurrent cysts,3) because of the mucous secretions of such lesions. Therefore, epithelial cysts should be completely extir pated if possible histology identified studies.
to prevent recurrence and the precisely by electron microscopic
References 1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
Ganti SR, Antunes JL, Louis KM, Hilal SK: Com puted tomography in the diagnosis of colloid cyst of the third ventricle. Radiology 138: 385-391, 1981 Ghatak NR, Kasoff I, Alexander E: Further observa tion on the fine structure of a colloid cyst of the third ventricle. Acta Neuropathol (Berl) 39: 101-107, 1977 Hall WA, Lunsford LD: Changing concepts in the treatment of colloid cysts. An 11-year experience in the CT era. J Neurosurg 66: 186-191, 1987 Hirai O, Kawamura J, Fukumitsu T: Prepontine epithelium-lined cyst. Case report. J Neurosurg 55: 312-317, 1981 Hirano A, Ghatak NR: The fine structure of colloid cyst of the third ventricle. J Neuropathol Exp Neurol 33: 333-341, 1974 Iihara K, Kikuchi H, Ishikawa M, Nagasawa S: Epidermoid cyst traversing the pons into the fourth ventricle. Case report. Surg Neurol 32: 377-381, 1989 Keyaki A, Hirano A, Llena JF: Differential diagnosis and origin of epithelial cysts in the central nervous system. Report of seven cases and review of articles. No To Shinkei 41: 411-418, 1989 (in Japanese) Kjos BO, Brant-Zawadzki M, Kucharczyk W, Kelly WM, Norman D, Newton TH: Cystic intracranial le sions: Magnetic resonance imaging. Radiology 155: 363-369, 1985 Koto A, Horoupain DS, Shulman K: Choroidal epithelial cyst. Case report. J Neurosurg 47: 955-960, 1977 Maeder PP, Holtas SL, Basibuyuk LN, Salford LG, Tapper UAS, Brun A: Colloid cyst of the third ventri cle: Correlation of MRI and CT findings with histology and chemical analysis. AJNR 11: 575-581, 1990 Nishioka T, Kondo A, Kusaka H, Imai T: Epithelium-lined cyst of the pretectal region: Case report and electron microscope study. Surg Neurol 31: 448-453, 1989
12)
13)
14)
Sackett JF, Messina AV, Petito CK: Computed tomography and magnification vertebral angio tomography in the diagnosis of colloid cyst of the third ventricle. Radiology 116: 95-100, 1975 Shuangshoti S, Netsky MG: Neuroepithelial (colloid) cyst of the nervous system. Further observation on pathogenesis, location, incidence, and histochemis try. Neurology (Minneap) 16: 887-903, 1966 Tandon PN, Roy S, Elvidge A: Subarachnoid epen
dymal
cyst.
741-745,
Address
reprint
Report
requests
of Neurosurgery, sity, 54 Shogoin 606,
Japan.
of
two
cases.
J Neurosurg
37:
1972
to: 0.
Hirai,
M.D.,
Department
Faculty of Medicine, Kyoto Kawahara-cho, Sakyo-ku,
Univer Kyoto
Epithelial Extending
Cyst into
—
Osamu Departments
HIRAI,
the Fourth
Case
Akinori
of Neurosurgery
in the Prepontine
Cistern
Ventricle
Report—
KONDO
and
Hirofumi
KUSAKA*
and *Neurology, Kitano Medical Research and Hospital, Osaka
Institute
Abstract The authors report a case of epithelial cyst, which recurred 32 years after the initial surgical treatment. Computed tomography showed no abnormality, but magnetic resonance (MR) imaging clearly demonstrated a well-demarcated mass in the prepontine cistern, extending into the fourth ventricle. The lesion showed extreme hyperintensity compared with the surrounding brain on both the T1and T2-weighted images. The ultrastructural features of the cyst suggested an endodermal origin. MR im aging and electron microscopy are essential for correct diagnosis and exact pathogenetic identification of intracranial cystic lesions. Key words: electron
epithelial
cyst,
endodermal
origin,
recurrence,
Introduction
Case
was admitted cranial nerve
pareses and moderate motor weakness and hypes thesia of the left lower extremity. He had undergone surgical removal of a cystic mass located in the fourth ventricle at the age of 21, because of pro
Received
right abducens September present
imaging,
gressive motor weakness of the left lower extremity. Pre and postcontrast computed tomographic (CT) scans on admission revealed no abnormalities. Cerebral angiography and myelography were also normal. However, MR imaging disclosed a well demarcated irregular mass with marked hyperinten sity signals on both the T, and T2-weighted images. The mass was located on the left side of the prepon tine cistern and apparently extending dorsally through the pons into the fourth ventricle (Fig. 1). A left suboccipital craniectomy disclosed a cystic mass in the subarachnoid space between the fifth and tenth cranial nerves. The cyst surface was smooth, and a puncture yielded about 10 ml of creamy viscous fluid. The extremely thin membranous cyst wall was almost totally removed, but the part in the fourth ventricle was inaccessible. The cyst fluid con tained 81 mg/dl of cholesterol and 566 mg/dl of
Report
On June 21, 1989, a 53-year-old male with persistent right fifth to eighth
Author's
resonance
cyst wall burst perioperatively, and as the yellowish viscous content immediately entered the cerebrospi nal fluid, no specimen of the cyst wall was obtained. He remained well until 1987, when he noticed pro
Cysts lined by a single layer of epithelium may occur anywhere in the central nervous system (CNS).2,4'''''"' Since various pathological entities are included in this disease, electron microscopic examinations may often be required for precise diagnosis." Here, we describe a recurrent cyst of endodermal origin, located in the prepontine cistern and extending into the fourth ventricle. The characteristics and diag nostic value of magnetic resonance (MR) imaging for epithelial cyst are also discussed.
gressive
magnetic
microscopy
25,
address:
and facial 1990; O. Hirai, Japan.
nerve Accepted M.D.,
pareses. October Department
The 26,
1990
of Neurosurgery,
Faculty
of Medicine,
Kyoto
University,
Kyoto,
total protein. The albumin/globulin ratio was 0.08, lower than that in serum. Light microscopy showed that the cyst wall was lined by a single layer of cuboidal epithelium con taining numerous granules with positive periodic acid-Schiff (PAS) staining (Fig. 2). Ultrastructural ly, the epithelium contained ciliated and non-cili ated cells. The latter cells contained numerous free ribosomes and were slightly darker. Microvilli on the luminal surface of the non-ciliated cells were coated by electron-dense materials. Several func tional complexes and well-developed interdigitations were noted between adjoining cells. The underlying connective tissue was clearly separated from the epithelium by a distinct continuous basement mem brane (Fig. 3). The postoperative course was uneventful, except
Fig. 3
Electron micrograph, showing ciliated and non-ciliated cells, numerous free ribosomes, and electron-dense materials coating the lumi nal surface of the non-ciliated cells. There are also well-developed interdigitations between adjacent cells. Bar = 1 um.
for mild meningitis successfully treated by in trathecal antibiotics. He was discharged with no addi tional neurological deficit and improved motor weakness and hypesthesia of the left lower extremity. Postoperative MR images showed disappearance of the cyst in the prepontine cistern but a small remnant in the fourth ventricle. One year postoperatively, he was working normally.
Discussion Fig. 1
Fig. 2
T, (left) and T,-weighted (right) MR images, showing a well-demarcated high-intensity mass with an irregular shape in the left prepontine cistern, apparently extending into the fourth ventricle.
Light
micrograph,
lined
by
numerous x 200.
demonstrating
columnar PAS-positive
epithelial
the cyst wall cells
granules.
containing PAS
stain,
Epithelial cysts occur anywhere in the CNS, and are described by various terms including colloid cyst, neuroepithelial cyst, paraphyseal cyst, ependymal cyst, choroidal epithelial cyst, and enterogenous cyst. 1,1,1,131Previously, a single etiology for these cysts was considered, but now several causes are recognized depending on the site and ultrastructural features.','," The epithelial cysts may become symptomatic at any age, but most are considered to form in the fetus. In this case, simple evagination of a fourth ven tricular cyst derived from epithelial lining of the epen dyma or choroid plexus might also have caused the prepontine lesion. However, MR images showed that the intraventricular and extraventricular parts were not connected by the foramen of Luschka, but rather through the pontine parenchyma. lihara et al." recently reported an epidermoid cyst traversing the pons into the fourth ventricle through In this case, no such defect was found suboccipital craniectomy.
a small defect. by a unilateral
The initial neurological symptoms of right ab ducens and facial nerve pareses strongly suggested the primary focus in the prepontine cistern. The first operation, 32 years previously, only detected the in traventricular part of the cyst. However, this does not exclude a prepontine lesion since the approach was a midline suboccipital craniectomy. Therefore, it is unlikely that the extraventricular part of the cyst developed from the fourth ventricular cyst. Another possibility is that the extraventricular part is derived from heterotopic neuroglial nests.") Electron microscopic study of the cyst showed the epithelium containing both ciliated and non-ciliated cells, electron-dense materials coating the microvilli on the luminal surfaces of the non-ciliated cells, and a distinct continuous basement membrane and promi nent interdigitations along the lateral cell borders. These features suggest an endodermal origin, especially the respiratory epithelium, rather than a neuroepithelial origin, because a basement mem brane is not common in the ependyma, cilia and in terdigitations at the lateral borders of adjacent cells are not constant features of the choroid plexus, and electron-dense materials have never been seen in the normal CNS.2,5> The neural tube closes cranially at Carnegie stage 11 (about 24 days) and caudally at stage 12 (about 26 days), followed by thickening of the wall to form the brain and spinal cord. Therefore, any migration of endodermal tissue into the CNS should have oc curred by then. The introduction of CT has made the diagnosis of intracranial cystic lesions much easier. Most epithe lial cysts appear isodense or slightly hyperdense compared with surrounding brain parenchyma, because the cyst fluid contains protein, ionic cal cium, iron, and other metals. 1,121However, CT pro vided no information in this case as the cyst was perfectly isodense and unenhanced by the contrast injection. MR imaging now provides much useful informa tion about intracranial cystic lesions.') Coronal and sagittal images allow better visualization of the anatomical relationship with the surrounding neural structures. Cysts containing fluid almost identical with cerebrospinal fluid appear as low-intensity signals on T1-weighted images and high-intensity signals on T2-weighted images, using routine pulse se quences.' Recently, Maeder et al.") demonstrated the heterogeneous MR appearance of colloid cysts of the third ventricle, despite the homogeneous his tology. They suggested that high-signal intensities on T1-weighted images correlated with high choles terol content, but metals did not affect signal inten
sities. Cyst fluid analysis in this case also could not explain the extremely high-signal intensities on both the T1 and T2-weighted images. Such variation in MR features is compatible with heterogeneous histo pathogenesis. Craniotomy is the best surgical treatment for di rectly accessible benign epithelial cysts. Recent developments in stereotactic procedures allow safer and less traumatic cyst evacuation. However, a number of patients have required subsequent craniotomy to remove residual or recurrent cysts,3) because of the mucous secretions of such lesions. Therefore, epithelial cysts should be completely extir pated if possible histology identified studies.
to prevent recurrence and the precisely by electron microscopic
References 1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
Ganti SR, Antunes JL, Louis KM, Hilal SK: Com puted tomography in the diagnosis of colloid cyst of the third ventricle. Radiology 138: 385-391, 1981 Ghatak NR, Kasoff I, Alexander E: Further observa tion on the fine structure of a colloid cyst of the third ventricle. Acta Neuropathol (Berl) 39: 101-107, 1977 Hall WA, Lunsford LD: Changing concepts in the treatment of colloid cysts. An 11-year experience in the CT era. J Neurosurg 66: 186-191, 1987 Hirai O, Kawamura J, Fukumitsu T: Prepontine epithelium-lined cyst. Case report. J Neurosurg 55: 312-317, 1981 Hirano A, Ghatak NR: The fine structure of colloid cyst of the third ventricle. J Neuropathol Exp Neurol 33: 333-341, 1974 Iihara K, Kikuchi H, Ishikawa M, Nagasawa S: Epidermoid cyst traversing the pons into the fourth ventricle. Case report. Surg Neurol 32: 377-381, 1989 Keyaki A, Hirano A, Llena JF: Differential diagnosis and origin of epithelial cysts in the central nervous system. Report of seven cases and review of articles. No To Shinkei 41: 411-418, 1989 (in Japanese) Kjos BO, Brant-Zawadzki M, Kucharczyk W, Kelly WM, Norman D, Newton TH: Cystic intracranial le sions: Magnetic resonance imaging. Radiology 155: 363-369, 1985 Koto A, Horoupain DS, Shulman K: Choroidal epithelial cyst. Case report. J Neurosurg 47: 955-960, 1977 Maeder PP, Holtas SL, Basibuyuk LN, Salford LG, Tapper UAS, Brun A: Colloid cyst of the third ventri cle: Correlation of MRI and CT findings with histology and chemical analysis. AJNR 11: 575-581, 1990 Nishioka T, Kondo A, Kusaka H, Imai T: Epithelium-lined cyst of the pretectal region: Case report and electron microscope study. Surg Neurol 31: 448-453, 1989
12)
13)
14)
Sackett JF, Messina AV, Petito CK: Computed tomography and magnification vertebral angio tomography in the diagnosis of colloid cyst of the third ventricle. Radiology 116: 95-100, 1975 Shuangshoti S, Netsky MG: Neuroepithelial (colloid) cyst of the nervous system. Further observation on pathogenesis, location, incidence, and histochemis try. Neurology (Minneap) 16: 887-903, 1966 Tandon PN, Roy S, Elvidge A: Subarachnoid epen
dymal
cyst.
741-745,
Address
reprint
Report
requests
of Neurosurgery, sity, 54 Shogoin 606,
Japan.
of
two
cases.
J Neurosurg
37:
1972
to: 0.
Hirai,
M.D.,
Department
Faculty of Medicine, Kyoto Kawahara-cho, Sakyo-ku,
Univer Kyoto
