Teaching Case

Occipital headaches (more at right side) for 5 months; stronger in the last weeks.

A previous healthy adult men presented with strong occipital headaches (more at right side) for 5 months which were getting worse in the last weeks. He did not have other symptoms like nausea, vomiting or vertigo. Neurological examination was normal. Haemogram revealed leucocitosis and normal red blood cell counts. CT scan showed an expansive right cerebellar mass, near the right petrous temporal bone (extending to the right cerebellopontine angle but not into the internal auditory canal), with associated marked oedema, causing a IV ventricle deformation and supratentorial ventricular dilatation. MR confirmed a right cerebellar hemisphere mass with isosignal on T1WI and high intensity signal on T2WI, with abnormal serpentine voids suggesting vessels and marked oedema causing a significative mass efect in adjacent brain structures.
After gadolinium administration there was an intense but not homogeneous enhancement. The angiography examination showed a prolonged homogeneous vascular blush, confirming a vascular mass.

In adults, infratentorial neoplasms occur less frequently than supratentorial. Extra-axial lesions are most common; intra-axial are rare. The most frequent infratentorial tumours inadults are: metastasis, hemangioblastoma, meduloblastoma, glioma and limphoma (intra-axial); schwanomma, meningioma, epidermoid and lymphoma (extra-axial).
The intra-axial infratentorial tumours primarily involve the cerebellar hemispheres, with the most common being metastasis and hemangioblastomas (8-12% of all posterior fossa lesions in adults, much more frequent than metastasis). Hemangioblastoma is an highly vascular benign neoplasm of uncertain origin (WHO grade I) : approximately 80% are located in the cerebellum, followed by the spinal cord (10%), medulla (5%) and cerebrum (2%). They are more common in young men, with a peak incidence in the thirties, often presenting with headache, ataxia, nausea/vomiting, vertigo, or policithemia (by increased erythropoietin production - 40%; more frequent with solid hemangioblastomas). Although most hemangioblastomas are sporadic, they are associated with autosomally dominant Von Hippel-Lindau (VHL) disease in approximately 25% of the cases (frequently multiple and are also found in the medulla, spine and retina); 45% of patients with VHL disease will develop hemangioblastoma. Most hemangioblastomas can be treated with complete excision, and long-term recurrence rates seem to depend of the presence of VHL disease and multicentric lesions. MR is the most accurate exam to diagnosis and predicting the number, extension and vascularity of hemangioblastomas. It also provides a basis for further diagnostic and therapeutic procedures. MR imaging demonstration of a posterior fossa mass with abnormal vessels should suggest the diagnosis of hemangioblastoma.
Angiography is still usually required for the diagnosis and preoperative assessment of this tumor. On angiography examination, absence of dural vascular supply strongly mitigates against the possible diagnosis of a tentorial meningioma. When multiple and small HBs are present in VHL syndrome, angiography allow the screening of these lesions.
In approximately 55-60% of cases, hemangioblastoma shows the classic appearance of a cystic mass (with low intensity on T1WI and high intensity on T2WI) with an avidly enhancing mural nodule that abuts pial surface and serpentine signal voids of feeding vessels. Patient age, pial attachment, tiny hypervascular nodule with a huge cyst and lack of enhancement of the cyst wall aids in the differentiation of these lesions, mainly from Juvenile Pylocitic Astrocytoma. Purely solid hemangioblastomas are less common but occur in 40-45% of cases, potentially leading to the misdiagnosis of cerebellar glioma (less likely in adult population), and less common purely cystic HBs. In the solid type, the tumor usually is isointense on T1WI, high intensity on T2WI, with marked and homogeneous enhancement after Gad. Multiple extremely low-intensity serpentine "flow void" signs, indicating afferent and efferent vessels, are observed within or around the tumor.
We present a male adult with an infratentorial tumour, seeming intra-axial, without polycythemia. Neuroimaging studies are suggestive of a solid hemangioblastoma, but without homogeneous enhancement - sporadic one. Histopathology confirmed the diagnosis. In differential diagnosis (MRI) it is important to consider solitary infratentorial metastasis, often solid and could being very vascular.