(Image #1 and Image #2)
(Image #3 and Image #4)
(Image #1 and Image #2)
(Image #3 and Image #4)
Click on Images for Enlarged View
Findings: Image #1 is a contrast-enhanced axial CT of the head demonstrating an approximately 2 cm. ring enhancing lesion within the left cerebellum. There is significant associated edema with obliteration of the fourth ventricle.
Image #2 is a T2 weighted MR image of the head demonstrating an approximately 2 cm. region of increased signal within the left cerebellum with surrounding edematous changes.
Image #3 is a T1 weighted MR image in the same region demonstrating this lesion to be of low signal intensity on T1 weighted images.
Image #4 is a post Gadolinium enhanced T1 weighted sagittal image through the same region demonstrating this lesion to have a cystic center with irregular peripheral enhancement with more dense enhancement posteriorly near the pial surface.
Diagnosis: Hemangioblastoma.
Discussion: Hemangioblastomas are rare, benign, generally solitary tumors of the central nervous system most commonly identified within the posterior fossa. These lesions are most often found in the cerebellum, and although they may be solid, the majority are cystic. In addition, the majority of hemangioblastomas will demonstrate a densely enhancing peripheral nodule. In addition to the cerebellar hemispheres, the vermis and medulla are other potential sites of origin of hemangioblastomas. Between 4 and 20% of patients with hemangioblastomas of the cerebellum or spinal cord have von Hippel-Lindau disease. Histologically, these tumors are characterized by a fine hypervascularity mesh in a stroma of polygonal cells without evidence for mitotic activity. These lesions are always superficial in location most often located within the periphery of the cerebellar hemisphere. The nidus of the tumor always abuts the pial surface. The vascular supply to a hemangioma is derived from the pia. The characteristic radiologic findings of a hemangioblastoma on both CT and MR include a peripherally located cerebellar lesion with central cystic region with peripheral enhancing nodule. The signal intensity of the cystic portion of the hemangioma may be brighter than that of cerebral spinal fluid. In summary, the findings of a peripheral cystic structure with bright signal intensity on T2 weighted images located within the posterior fossa with an associated densely enhancing mural nodule is virtually pathognomonic for hemangioblastoma.
References:
Lee Seung. Posterior Fossa Hemangioblastomas: MR Imaging.
Radiology 1989;171:463-468.
Osborn Anne. Diagnostic Neuroradiology. Mosby, St. Louis. 1994.
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