Case of the Month #1
Case of the Monthby Laura Gillihan MD, Jose Gavito MD and Luis Ramos MD
Look carefully at the following images , What are the differential diagnosis?
Fig 1. Axial CT with contrast Fig 2. Reformated CT Fig 3. Axial T1WI
Fig 4. Axial T1 with contrast Fig 5. Coronal T2WI Fig 6. Sag T1 with contrast.
Findings :
CT scan:
Presence of a 40.6 x 35.0 mm homogeneous, well defined, extra-axial tumor in the pineal region, presenting 45 Hounsfield units, with mass-effect of the adjacent structures, intensive and homogeneous enhancement after contrast media administration.
MRI:
Extra-axial lesion with isointense signal to the gray matter in the T1 and T2-WI and with intense homogeneous enhancement after gadolinium administration, measuring 40.6 x 35.6 m (Fig 7 & 8); localized in the pineal region above the supracerebellar cistern, producing marked mass-effect, compressing the quadrigeminal plate (Fig 9), with right lateral displacement of the internal cerebral veins (Fig 7) and rostral (anterior) displacement of the thalamus, splenium of the corpus callosum and posterior wall of the third ventricle.(Fig 8)
Fig 7. T1WI Fig 8. T1 with contrast Fig 9. Cleft sign
Fig 10. Dural tail sign
Differential diagnosis according to suspected mass origin :
1. Splenium: Exophoytic GBM
Primary CNS Lymphoma
2. Pineal tumor:
Pinealoma
Pinealoblastoma
Meningioma
3. Cuadrigeminal plate:
Exophitic Astrocytoma of the Cuadrigeminal plate
4. Cisternal Structures:
Cisternal Abducens nerve schwanoma
Thrombosed Anomaly of the Galen Vein
Diagnosis: Pineal meningioma
Key facts:
• Meningioma is the most common extraaxial tumor among adults, and constitutes 15% of all intracranial tumors among adults
• Meningioma occurs mainly among middle aged women (sex hormones may be responsible) and patients with neurofibromatosis type II (especially multiple meningioma)
• Common sites include parasagittal-falcine (50%), sphenoid wing (20%), floor of the anterior cranial fossa (10%), parasellar region (10%), tentorium, and cerebellopontine angle.
• Histologic types are typical (90-95%), atypical (3-5%) and frankly malignant (1%)
• Classic “hyperostosis” of the underlying bone is present in only 5% of cases, typical meningioma may erode bone.
• At MRI, a “dural tail” suggests the diagnosis but is not pathognomonic.(Fig 10)
• Histologic features cannot be predicted, but bright meningiomas on T2- weighted magnetic resonance images tend to have more atypical microscopic features.
• Brain edema is present in 60% of cases.
• You may see calcifications within the meningiomas in 20%
Typical findings:
MR signal intensity characteristics: Isointensity to slight hypointensity relative to gray matter on T1-weighted image (T1WI) and isointense to hyperintense relative to gray matter on the T2WI.
The “cleft sign” (Fig 9) has been described in MR to identify extraxial intradural lesions such as meningiomas. The cleft usually contains one or more of the following :
1. Cerebrospinal fluid between the lesion and the underlying brain parenchyma.
2. Hypointense dura (made of fibrous tissue)
3. Marginal blood vessels trapped between the lesion and the brain.
You may be able to identify the “dural tail”; enhancement of the dura trailing off away from the lesion in crescentic fashion, which is typical of meningioma and has been exhibited in up to 72% of cases.
CT: 60% of meningiomas are slightly hyperdense compared with normal brain tissue. You may see calcifications within meningiomas in about 20% of the cases.
Suggested readings :
Typical, atypical, and misleading features in meningioma. [1]
The requisites [2]
Pineal meningioma article click here
Reference List
1. M.P.Buetow, P.C.Buetow, and J.G.Smirniotopoulos, Typical, atypical, and misleading features in meningioma. In: 1991, pp. 1087-1106.
2. R.I. Grossman, The requisites: Neuroradiology, Elsevier Inc, Philadelphia, PA, 2003.