Keywords
ventricles - brain - schwannoma - hydrocephalus
Case Presentation
A 20-year-old male patient without significant medical history presented to an urgent
care facility for the evaluation of intermittent blurry vision which had been present
for approximately 2 years. The patient additionally complained of dysesthesia: a burning
sensation, located at the upper neck and right occiput, intermittent in occurrence
and lasting only a few seconds, but increasing in intensity and severity over the
previous 2 months.
Physical examination found the patient to be awake, alert, and oriented. Pupils were
equal, round, and reactive to light and accommodation. A fundoscopic examination was
not performed. Cranial nerves II–XII were intact; specifically, extraocular motion
was intact. Reflexes and range of motion were normal, and the strength of the bilateral
upper and lower extremities was 5/5. Sensation, proprioception, muscle tone, and gait
were intact.
Initial radiologic evaluation included an unenhanced computed tomography (CT) scan
of the head which showed a right temporal horn intraventricular mass, with surrounding
white matter edema and dilation of the right lateral ventricle. Subsequent evaluation
with an enhanced magnetic resonance imaging (MRI) of the head included T2, T2*, fluid-attenuated
inversion recovery, diffusion-weighted, and T1-unenhanced images in the axial plane.
Unenhanced T1-weighted images were acquired in the sagittal plane, as well as enhanced
T1-weighted images in the axial, coronal, and sagittal planes. In aggregate, these
images showed a 2.1 × 1.9 × 2.6 cm (transverse × anterior-posterior × superior-inferior)
mass, located within the atrium of the right lateral ventricle. The mass demonstrated
mild T1 hypointensity ([Fig. 1A]) with areas of heterogeneous T2 hyperintensity ([Fig. 2A]).
Fig. 1. T1-weighted magnetic resonance imaging of the brain before (A) and after (B, C) the
administration of gadolinium-based contrast demonstrate a midly T1 hypointense, avidly
enhancing mass within the right lateral ventricle.
Fig. 2. T2-weighted magnetic resonance imaging of the brain demonstrate a heterogeneously
hyperintense mass within the right lateral ventricle. Enlargement of the posterior
horn of the right lateral ventricle with surrounding white matter edema is consistent
with ventricular entrapment.
Foci of susceptibility artifact within the mass ([Fig. 3]) were suggestive of calcification or hemosiderin deposition from previous hemorrhage.
Postcontrast images displayed homogeneous enhancement ([Fig. 1B, C]). Within the white matter of the surrounding right parietal and inferior right temporal
lobes, there was a large amount of edema ([Fig. 2A]). Asymmetric enlargement of the right lateral ventricle ([Fig. 2B]), particularly at the level of the right temporal horn, was suggestive of ventricular
entrapment. The third and fourth ventricles were normal in size. The primary radiographic
consideration was a meningioma, although ependymoma and choroid plexus papilloma were
in the differential.
Fig. 3 T2*-weighted magnetic resonance imaging of the brain demonstrates susceptibility
artifact within the mass, representing foci of calcification.
The patient underwent surgical resection of the tumor through a right parietal craniotomy,
with a transparietal approach, and intraventricular shunt placement for treatment
of associated ventricular entrapment. Gross examination demonstrated the tumor to
be well encapsulated and adherent to the medial aspect of the right lateral ventricle
wall. Areas of moderate calcification were noted.
Pathologic evaluation demonstrated densely packed fascicles of spindle cells with
elongated nuclei representing Antoni A tissue ([Fig. 4]). These were mixed with areas of loosely packed, hypocellular foci of spindle cells
with small, round nuclei within myxoid matrix. This was consistent with Antoni B tissue
([Fig. 5]).
Fig. 4 Hematoxylin-eosin staining viewed at ×200 magnification demonstrates densely packed
fascicles of spindle cells with elongated nuclei (Antoni A).
Fig. 5 Hematoxylin-eosin staining viewed at ×200 magnification demonstrates a loosely packed,
hypocellular focus of spindle cells with small, round nuclei in a myxoid matrix (Antoni
B).
Positive S-100 staining confirmed the Schwann cell origin of the tumor while the negative
epithelial membrane antigen confirmed that the tumor was not meningeal in origin.
Glial fibrillary acidic protein was also positive, a marker which may be variably
positive in schwannomas, but which is often positive in intracranial schwannomas.
MIB-1 stain demonstrated low nuclear positivity, consistent with a benign process.
The patient is currently 9 months out from surgical resection of the tumor without
radiographic evidence of residual or recurrent tumor.
Discussion
Schwannomas account for 8% of all primary brain tumors.[1] Most schwannomas are associated with cranial nerves, most commonly cranial nerves
VIII, V, and VII, and 80 to 90% are located in the region of the cerebellopontine
angle.[2] They have also been associated with spinal nerve roots and have been found in the
retroperitoneum and mediastinum. Rarely, schwannomas have been noted to arise from
intracranial locations, a subset of which have been described as intraventricular
in location.
The earliest reported case of an intraventricular schwannoma was described by Marchand
et al in 1957.[3] Since then 23 cases have been reported in the literature ([Table 1]).
Table 1
Reported cases of intraventricular schwannoma
|
Age (y)
|
Gender
|
Location
|
Benign/malignant
|
Year
|
Citation
|
|
44
|
Male
|
Lateral (occipital)
|
Benign
|
1990
|
Ost et al[5]
|
|
21
|
Male
|
Lateral (temporal)
|
Benign
|
1975
|
Van Rensburg[12]
|
|
63
|
Female
|
Lateral
|
Benign
|
1975
|
Ghatak[13]
|
|
8
|
Male
|
Lateral
|
Benign
|
1988
|
Pimentel et al[14]
|
|
40
|
Male
|
Lateral (temporal)
|
Malignant
|
1995
|
Jung et al[4]
|
|
15
|
Male
|
Lateral
|
Benign
|
1965
|
David et al[15]
|
|
7
|
Male
|
Fourth
|
Benign
|
1990
|
Redekop et al[16]
|
|
16
|
Male
|
Lateral (trigone)
|
Benign
|
2004
|
Dow et al[7]
|
|
15
|
Male
|
Lateral (occipital)
|
Benign
|
2008
|
Benedict et al[11]
|
|
21
|
Male
|
Lateral
|
Benign
|
2003
|
Erdogan et al[17]
|
|
21
|
Female
|
Third
|
Benign
|
2006
|
Messing-Jünger et al[18]
|
|
71
|
Female
|
Fourth
|
Benign
|
2009
|
Oertel et al[10]
|
|
36
|
Female
|
Fourth
|
Benign
|
2002
|
Estrada[19]
|
|
16
|
Male
|
Lateral
|
Benign
|
2007
|
Lévêque et al[20]
|
|
13
|
Female
|
Lateral
|
Benign
|
2001
|
Barbosa et al[21]
|
|
43
|
Male
|
Fourth
|
Malignant
|
1957
|
Marchand et al[3]
|
|
21
|
Male
|
Lateral
|
Benign
|
2013
|
Luo et al[2]
|
|
61
|
Male
|
Fourth
|
Benign
|
1993
|
Weiner et al[22]
|
|
78
|
Female
|
Fourth
|
Benign
|
1993
|
Weiner et al[22]
|
|
16
|
Male
|
Lateral (occipital)
|
Benign
|
2013
|
Jaimovich et al[9]
|
|
16
|
Male
|
Lateral
|
Benign
|
1993
|
Casadei[23]
|
|
49
|
Female
|
Lateral
|
Benign
|
1993
|
Casadei[23]
|
|
21
|
Female
|
Lateral (occipital)
|
Benign
|
2009
|
Vasconcellos et al[24]
|
Among these cases there is almost a 2:1 male-to-female predominance. The median age
of presentation is 31 years, with a reported age range of 7 to 78 years. Overall,
21 of the reported cases were benign in etiology with only 2 reported cases demonstrating
malignant features.[3]
[4] These lesions are most often located within the lateral ventricles (70%) but have
also been found in the fourth (26%) and third (4%) ventricles. The most common complication
associated with intraventricular schwannoma is the presence of hydrocephalus.
The clinical presentation of an intraventricular schwannoma often varies but most
commonly involves headache, nausea, and vomiting. Brachial-crural hemiparesis, seizures,
vertigo, and visual symptoms such as homonymous hemanopsia and transient scintillating
scotomas have also been reported. These lesions may also be asymptomatic and only
detected incidentally, through papilledema or retinal hemorrhage seen on an ophthalmic
screening examination.
Currently, the etiology of intraventricular schwannomas is unknown, although three
theories are often mentioned in the literature. The most popular theory postulates
that intraventricular schwannomas are the result of hyperplastic transformation of
Schwann cells associated with peripheral or autonomic nerve fibers located within
the choroid plexus.[5] This theory is supported by the identification of peripheral nerve fibers within
the choroid plexus of the fourth ventricle.[6] Another theory is neoplastic transformation of ectopic neural crest cells located
within the ventricles due to disorganized embryogenesis,[7]
[8] a theory that is supported by reported instances of schwannoma attachment to the
choroid plexus. The final theory involves neoplastic transformation of pluripotent
mesenchymal cells into Schwann cells after tissue injury.[9] No association between intraventricular schwannomas and genetic syndromes has been
identified.
The ubiquitous availability of CT means it is often the modality used for the initial
evaluation of intraventricular schwannoma. Intraventricular schwannomas have been
described as both hypodense and hyperdense, with possible cystic components. Calcifications
are often present. On MRI, intracranial schwannomas are predominantly solid with cystic
components. Solid components are most often homogeneously T1 hypointense with heterogeneous
T2 hyperintensity. The cystic components mostly follow simple fluid characteristics
(T1 hypointensity, T2 hyperintensity). The enhancement pattern has been described
as heterogeneous both on CT and MR studies, and attachment to the choroid plexus and
ventricle wall may be visualized. Associated periventricular edema may be visualized
on both CT and MRI. Due to the rarity of these lesions, the differential diagnosis
is mostly based on imaging findings and lesion location. The imaging differential
diagnosis includes cystic astrocytomas, cystic meningiomas, ependymoma, choroid plexus
papilloma, choroid plexus carcinoma, hemangioblastoma, and metastatic lesions.
Primary treatment is complete surgical resection. For tumors located within the lateral
ventricles, a transcortical approach with osteoplastic craniotomy is favored.[10] When the tumor is located in the third or fourth ventricles, a midline suboccipital
approach is generally performed.[10] Although complete surgical resection is always the preferred treatment, occasionally
tumors may involve intracranial vessels or invade cerebral parenchyma, and complete
resection may not be possible. In the single reported case where complete resection
was not possible and pathology demonstrated malignancy, subsequent treatment with
whole brain radiation was also performed (Jung et al). In cases of benign intraventricular
schwannomas where complete resection is not possible, close radiologic follow-up is
often pursued.[11]
Only two cases of malignant intraventricular schwannomas have been reported (Jung
et al and Marchand et al). In the case of Jung et al, the schwannoma was incompletely
resected due to tumor invasion and treated with subsequent whole brain radiation.
Tumor recurrence with metastatic disease to the left cerebellopontine angle and cerebellar
surface was diagnosed 4 months after the initial surgery.
Conclusions
Here, we present a case of right atrial intraventricular schwannoma causing right
lateral ventricle entrapment. Although a rare cause of primary central nervous system
neoplasm, with fewer than 25 cases reported in the literature, clinicians should keep
intraventricular schwannoma in mind when evaluating enhancing intraventricular masses.
These lesions are most often benign and may be fully cured with surgical resection.
