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Neuroradiology
Case of the Week
Case
66
Karin
Westesson, Sudhir Kathuria, MD, George Mangalasseril,
Kha Nguyen, and PL Westesson, MD, PhD, DDS
Clinical
Presentation: A
13-year-old male presented with headache and a head CT showed
a right thalamic mass. Head MRI was requested for evaluation.
Radiological
Findings:
Diagnosis:
Ependymona
Discussion: Ependymonas
are moderately cellular malignant tumors which account for 10%
of pediatric brain tumors with a major peak occurrence between
the ages of 1 and 5 and another minor peak in the 3rd decade of
life [1-4]. They are formed from differentiated ependymal cells,
which line the floor and the roof of the 4th ventricle and expand
into both lateral recesses and into the foramina of the Luschka
[1].
The lesions are described as a well-demarcated, soft, lobulated grayish-red mass.
It may be cystic, necrotic or hemorrhagic [2]. Since they are soft and deformable,
they will insinuate through the subarachnoid spaces and around blood vessels,
nerves, surrounding and engulfing structures. Because of their malignant nature,
ependymonas will grow through the 4th ventricle wall, where they originate and
adhere to the adjacent brain tissue [1]. Tumors in the infrantentorial region
are more common in children under the age of 3 [2]. They arise from the ependymal
lining of the floor of the 4th ventricle and grow into the cerebellopontine angle
and extend posteroinferior through the foramen of Magendie into the cisterna
magna [3]. Children over the age of 3 and young adults generally have supratentorial
ependymonas [2], which originate from ependymal cell rests and grow into the
body of the lateral ventricles and expanding into the adjacent white matter of
the front parietal lobes [4]. Calcification is common in both types [2].
Symptoms of an ependymona are clinical manifestations
of the increase intracranial pressure, hydrocephalus, and involvement of the
cerebellum [4]. Most patients
present with headache, nausea, vomiting. Depending on the location and growth
pattern, some patients may also exhibit torticollis, ataxia (if it is near obex),
or lower cranial neuropathies (if in the foramen of Luschka and cerebellopontine
angle) [1]. Infants will be irritable, lethargic, developmentally delayed and
may show macrocephaly [2].
Ependymonas can be difficult to diagnose based on imaging.
On CT scans, the ependymonas appear as an iso or hyperdense 4th ventricular mass
with small, multifocal calcification
and moderate enhancement with contrast [4]. On MRI, it appears as heterogeneous
hypointense on T1-weighted and iso to hypointense on T2-weighted [2]. Foci that
are of high-intensity represent necrotic or cystic tissue and those with low
intensity are areas of calcification and hemorrhaging [4]. With contrast, it
will moderately and heterogeneously enhance [2]. The most important feature
of
ependymonas is the extension through the foramen of magendie and foramen magnum
into the dorsal cervical subarachnoid space behind the cervical spinal cord [4].
Because they tend to engulf surrounding structures, ependymonas
are difficult to cure. Entire removal of the affected region is uncommon and
recurrence is
common. Treatment usually consists of surgical resection, followed by chemotherapy
and radiation therapy. The prognosis is poor - only 50-60% survival
rate after 5 years [2].
References:
- Barkovich AJ. Intracranial orbital and neck tumors of childhood. IN: Pediatric
Neuroimaging. Philadelphia: Lippincott, Williams &
Wilkins, 2000.
- Osborn AG, Blaser SI, Salzman KL. Pocket
Radiologist: Brain. Philadelphia: W. B. Saunders, 2002.
- Osborn AG, Rauschning
W. Brain tumors and tumor-like masses - classifications and differential
diagnosis. IN: Diagnostic
Neuroradiology. Ed. Anne G. Osborn. St. Louis: Mosby, 1994.
- Tamaraz JC, Outin C, Forjaz-Secca M, Soussi B. MRI
Principles of Head, Skull Base and Spine. New York: Springer-Verlag, 2002.
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