Clinical History:
14-year-old male with history of headaches for several months.
Figure 1
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Radiographic Findings:
Large mass extending from the right suprasella region cephalad into the
right basal ganglia region. A portion of the mass is cystic appearing and
a portion uniformly enhances. There is mass effect and enlargement of the
lateral ventricle secondary to compression of the foramen of Monroe.
Discussion:
Some of the principles learned from the December Radiology web article
entitled "Couplet
Approach to Posterior Fossa Tumors" by Dr. J. Abrahams can be
used to help figure out this case. First, anytime there is a cystic lesion,
one needs to take the time to determine whether the cyst wall is enhancing
or not. In this case, there is no contrast enhancement of the cyst wall
which suggests a more benign, rather than aggressive, type lesion. The
lack of cyst wall enhancement should lead one to consider such lesions
as cystic meningioma, cystic astrocytoma, hemangioblastoma. If the cyst
wall did enhance, then more aggressive lesions such as glioblastoma, higher
grade astrocytoma, metastases, abscess, etc. should be considered.
Cystic meningioma, arising from the dorsum sella, seems like a reasonable
possibility. Since hyperostosis is not present, we must rely on other
information to determine if this is a meningioma or not. On the T2-weighted
MR scan the solid portion of the lesion is quite bright and almost of
the same signal as the cyst. Meningiomas (and lymphomas) are lesions which
tend not to be as bright as most lesions on the T2-weighted sequence.
The fact that the lesion is so bright on T2 makes meningioma very unlikely.
In differentiating between cystic astrocytoma and hemangioblastoma, age
is most important, with the former being seen in the pediatric age group
and the latter being seen in adults. Since this patient is 14 years old,
the more likely diagnosis is cystic astrocytoma. Other lesions which should
always be considered in the suprasella region are aneurysms, however,
this does not have the radiographic appearance of a giant aneurysm.
Cystic astrocytomas (pilocystic astrocytomas) are the most common posterior
fossa tumors in children, but are also frequently seen in the supratentorial
region. They have a peak incidence at around age 10, with the supratentorial
lesions being seen in slightly older children. These lesions are relatively
benign and resection of the enhancing nodule is usually curative. Occasionally,
there may be some enhancement noted in the cyst wall, and this frequently
implies a more aggressive lesion. If the cyst wall is involved, then the
enhancing nodule, as well as the cyst wall, needs to be resected.
Diagnosis:
Cystic astrocytoma
References:
- Osborne ENG. Astrocytomas and other glialneal
plasms. In: Osborne A ed. Diagnostic Radiology. St. Louis: CV Mosby,
1994: 529-578.
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