Type 1 (5% of posterior fossa HBs) is a simple cyst without a macroscopic nodule.
Type 2 is a cyst with a mural nodule (60%).
Type 3, or solid tumors (26%).
Type 4, or solid tumors with small internal cysts (9%), are also seen in the cerebellum and predominate in the spinal cord.
Some authors have stated that type 1 is actually rare.
Symptoms correlate with regional compression of cerebrospinal fluid (CSF) flow or eloquent tissue and can include cerebellar signs and symptoms, cranial nerve deficits and weakness and spasticity, among other findings.
Despite extensive literature describing the diagnosis, treatment, and prognosis of these lesions, 3) individual cases still present a surgical quandary given their frequently eloquent location and high degree of vascularity.
Typically haemangioblastomas (60% of cases) are sharply demarcated homogeneous masses composed of cyst with non-enhancing walls, except for a mural nodule which vividly enhances and often has prominent serpentine flow voids 4).
Not infrequently the mural nodule itself has cystic spaces within it. The solid nodules are commonly seen abutting the pia mater.
In the remaining 40%, the tumour is solid with no cystic cavity 5).
The mural nodule is isodense to brain on non-contrast scans with fluid density surrounding cyst bright enhancement of the nodule is demonstrated with contrast the cyst walls do not usually enhance calcification is not a feature.
The combination of a peripheral posterior fossa cyst with a mural nodule supplied by enlarged vessels may be pathognomonic 6).
Based on MRI findings, there are several known types of this tumor. The most common type consists of small nodular tumors on the side of a large cyst and the two rarer types comprise a solid mass, or a lesion with an enhanced cyst wall due to cystic nodules, which exhibits enhanced uneven walls on imaging 7).
Postcontrast MR of the head and spine is the best currently available means of detecting hemangioblastomas associated with VHL 8).
At present, no unified radiological classification system based on magnetic resonance imaging (MRI) findings exists for cerebellar hemangioblastoma, and this tumor type can be solid or cystic mass, according to the MRI findings. The most common presentation of cerebellar hemangioblastoma observed radiologically is a large sac with small nodules, where the wall of the large cyst is not enhanced. A tumor with enhanced large cysts and tumor nodules is extremely rare 9).
hypointense to isointense mural nodule
CSF signal cyst content
T1 C+ (Gd)
hyperintense mural nodule flow voids due to enlarged vessels may be evident especially at the periphery of the cyst, seen in 60-70% of cases 12) fluid filled cyst, similar to CSF
MR perfusion imaging:
high rCBV ratios
Enlarged feeding arteries and often dilated draining veins are demonstrated, with a dense tumour blush centrally 13)
Cerebral angiography should be performed to rule out vascular abnormalities such as cerebral aneurysms adjacent to the tumor in patients with hemangioblastoma who present with intracranial hemorrhage.
Simultaneous 3D visualization of feeding arteries, draining veins, and surrounding structures is needed. A study evaluated the usefulness of high-resolution 3D multifusion medical imaging (hr-3DMMI) for preoperative planning of hemangioblastoma. The hr-3DMMI combined MRI, MR angiography, thin-slice CT, and 3D rotated angiography. Surface rendering was mainly used for the creation of hr-3DMMI using multiple thresholds to create 3D models, and processing took approximately 3-5 hours. This hr-3DMMI technique was used in 5 patients for preoperative planning and the imaging findings were compared with the operative findings. Hr-3DMMI could simulate the whole 3D tumor as a unique sphere and show the precise penetration points of both feeding arteries and draining veins with the same spatial relationships as the original tumor. All feeding arteries and draining veins were found intraoperatively at the same position as estimated preoperatively, and were occluded as planned preoperatively. This hr-3DMMI technique could demonstrate the precise locations of feeding arteries and draining veins preoperatively and estimate the appropriate route for resection of the tumor. Hr-3DMMI is expected to be a very useful support tool for surgery of hemangioblastoma 14).
Several primary pathologic entities in diverse anatomic locations have the potential to simulate metastatic neoplasms histologically. Their misinterpretation as such may result in needless and extensive clinical evaluations that are intended to detect a presumed malignancy at another site. More importantly, mistakes of this type can deprive patients of surgical excisions that could be curative 15).
High b value DWI reflects diffusion more accurately than does regular b value. Results showed that ADC calculation by high b value (b = 4000) DWI at 3-T magnetic resonance imaging is clinically useful for differentiating hemangioblastomas from brain metastases 16).
Gamma Knife Radiosurgery as well as LINAC have also been employed to successfully treat recurrence and control tumor growth of cerebellar hemangioblastomas.
A retrospective chart review revealed 12 patients with a total of 20 intracranial hemangioblastomas treated with GKRS from May 1998 until December 2014. Kaplan-Meier plots were used to calculate the actuarial local tumor control rates and rate of recurrence following GKRS. Univariate analysis, including log rank test and Wilcoxon test were used on the Kaplan-Meier plots to evaluate the predictors of tumor progression. Two-tailed p value of <0.05 was considered as significant. Median follow-up was 64months (2-184). Median tumor volume pre-GKRS was 946mm3 (79-15970), while median tumor volume post-GKRS was 356mm3 (30-5404). Complications were seen in two patients. Tumor control rates were 100% at 1year, 90% at 3years, and 85% at 5years, using the Kaplan-Meier method. There were no statistically significant univariate predictors of progression identified, although there was a trend towards successful tumor control in solid tumors (p=0.07). GKRS is an effective and safe option for treating intracranial hemangioblastoma with favorable tumor control rates 18).
Suzuki et al. emphasize the usefulness of embolization with N-butyl cyanoacrylate for hemangioblastoma with ruptured feeder aneurysm, by which the aneurysm and the feeder could be simultaneously embolized 19).
Solitary hemangioblastomas are for the most part considered benign, curable by total resection, except in those cases associated with von Hippel Lindau disease.
Bründl et al. retrospectively analyzed the clinical, radiological, surgical, and histopathologic records of 24 consecutive patients (11 men, 13 women; mean age 51.3 years) with HBL of the posterior cranial fossa, who had been treated between 2001 and 2012.
Mean time to diagnosis was 14 weeks. The extent of resection (EOR) was total in 20 and near total in 4 patients. Four patients required revision within 24 h because of relevant postoperative bleeding. One patient died within 14 days. One patient required permanent shunting. At discharge, 75% of patients [n = 18, modified Rankin scale (mRS) 0-1] showed no or at least resolved symptoms. Mean follow-up was 21 months. Two recurrences were detected during follow-up.
In comparison to other benign entities of the posterior fossa, time to diagnosis was significantly shorter for HBL. This finding indicates the rather aggressive biological behavior of these excessively vascularized tumors. In this series, however, the rate of complete resection was high, and morbidity and mortality rates were within the reported range 20).
Cerebrospinal fluid dissemination of cerebellar hemangioblastoma was found dominantly in non-Von Hippel Lindau disease patients. The diagnosis was made 10 years after the initial surgery. Irradiation therapy was performed, but the patients died about 2 years after the diagnosis was given. Molecular targeted therapies including vascular proliferation suppression have been attempted lately, but no effective therapy has been established. Early diagnosis of dissemination as well as combination of aggressive excision and stereotactic radiosurgery are considered to be appropriate for current interventions 21).
Symptoms and signs caused by cerebellar hemangioblastomas in VHL disease are associated with edema and peritumoral cyst formation/propagation and are treated safely and effectively with resection. Cerebrospinal fluid diversion is rarely necessary after complete tumor removal in patients with preoperative hydrocephalus. Cerebellar hemangioblastomas are preferentially distributed in the posterior half of the cerebellum, as they are in the brainstem and spinal cord. Tumor recurrence is avoided by meticulous extracapsular resection 22).