Cancer Genetics and Epigenetics 2017, Vol.5, No.4, 17-24
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It is worth to note that Grade III ependymomas are characterised by hypercellularity, cellular and nuclear
pleomorphism, frequent mitosis, pseudopalisading necrosis and endothelial proliferation associated with higher
risk of recurrence, or drop metastasis through CSF and spine, which accounts for 8-33%, particularly detected in
infratentorial lesions. Therefore, imaging protocols including intracranial and spinal MR examination are essential
before operation.
Notably, MR-spectroscopy is noted for its priority in providing additional biochemical information in which
intense signals of myo-inositol are observed in ependymomas compared with conventional MRI sequences (T1-
and T2-weighted MRI, contrast T1-weighted MRI) (Yang, 2016). Moreover, MRS is considered of importance for
optimal treatment strategies. Radio surgical resection is recommended for ependymomas aiming for recurrences;
while radical resection is considered optimal treatment for other tumors such as meningiomas. It was unfortunate
that MR- spectroscopy was not performed in either of the cases reported here.
2.4 Differential diagnosis
Housing 6-10% of all intracranial tumors, CPA represents a space comprising neuroglia tissue, cranial nerve
sheaths, meninges and embryo reminant. A wide spectrum of lesions occurs in the space of the CPA. In adults,
benign tumors are more common including vestibular schwannomas (70-80%), meningiomas (10-15%) and
epidermoid cysts (3-7%) (Patel, 2012). Vestibular schwannomas are the most common lesion within the CPA
space, typically arising from the inferior vestibular portion of the VIII cranial nerve. Most of vestibular
schwannomas originate from the VIII cranial nerve in the lateral third of the internal auditory canal, where they
grow medially along the line of least resistance, remodeling and expanding the canal and extending into the CPA.
In 90% of patients, the initial presenting symptoms entail unilateral sensorineural hearing loss, tinnitus, and
imbalance. Radiologically, vestibular schwannomas are round or oval lesions that show isointensity on T1WI
compared with parenchyma, and variable signals intensities on T2WI owing to its components such as Antonio
A/B. After contrast administration, intense enhancement detected. Bony changes including widening of the canal
caused by the lesion are usually demonstrated on Computed tomography (CT). However, overall radiologic
findings are nonspecific for vestibular schwannomas.
Meningiomas that occupy the CPA are usually based at the posterior surface of the petrous bone or the
petrotentorial junction where the arachnoid villi are predominately found. Owing to the diverse anatomic location
from vestibular schwannomas, meningiomas are more likely to present with hearing loss later in the disease
process and involve other cranial nerves more frequently. Radiologically, CT scan may demonstrates
homogeneous masses showing its higher tendency for bony destruction or hyperostosis. The presence of
calcification and dural tails may be helpful in differential diagnosis. Meningiomas usually show isointensity on
both T1WI and T2WI, or variable signal intensity on T2WI, with bright enhancement. The similar MRI
manifestations make radiologic differentiation of the two lesions difficult at times. Most reported IEAEs and
present case were misdiagnosed as meningiomas. In a recent study, Yang Yang et al found it useful to apply MRS
in differential diagnosis between meningioma and ependymoma, and helpful for making treatment decisions.
intrascranial extral-axial ependymoma case showed choline and myo-inositol/glycine peaks, rather than alanine
glutamate/glutamine peaks commonly dected in meningioma; however, the conclusion is made based on very rare
data.
The remaining abnormalities found at CPA space account for less than 1% of all lesions in this region (Patel,
2012). Such as CPP, although exceedingly rare, needs to be taken into account. CPP shows iso to homogeneous
hyperintensity on T1WI and T2WI, with 20% showing calcifications; whereas, calcification is rare in ependymal
tumors.
However, these above neoplasms are rarely seen in children. For children, ependymal tumors usually arise from
the fourth ventricle (the roof, floor, lateral medullary velum) and its lateral recess and extend into the CPA or
subarachnoid space through the foramen of Luschka by means of exophytic growth. No case of CPA anaplastic
ependymoma in children has been reported yet.
