Angiomatous meningioma

Angiomatous meningiomas are a rare histological variant of WHO grade I meningiomas and account for only 2.1% of all meningiomas ^1,3. 

The epidemiology and clinical presentation of these tumours does not clearly deviate from that of more common histological variants of meningiomas and is thus not repeated here.

Terminology

Unfortunately the main differential for an angioblasticangiomatous meningioma is a haemangiopericytoma, which used to be considered a variant of meningioma and went by the annoyingly similar name of "angioblastic meningioma".

Pathology

Angiomatous meningiomas, as their name suggests, demonstrate abundant blood vessels (greater than 50% of the whole tumour) within a tumour with areas of classic meningothelial differentiation ¹. They are considered WHO grade I tumours and cellular atypia and anaplasia is not present ³.

Radiographic features

CT

Appearance of angiomatous meningiomas on CT is similar to that of more typical meningothelial and fibrous subtypes, appearing as slightly hyperdense to adjacent brain parenchyma and exhibiting vivid contrast enhancement ¹.

MRI

On MRI angiomatous meningiomas can be difficult to distinguish from microcystic meningiomas and chordoid meningiomas other than the presence of often prominent flow voids. They frequently have obvious dural tails and not infrequently demonstrate some cystic change ¹.

Signal characteristics 

Typically the exhibit the following signal characteristics ¹:

• T1: hypointense compared to grey matter
• T1 C+: vivid enhancement
• T2
  • ​hyperintense compared to grey matter
  • peritumoralperitumoural oedema very common (75-100%) ²
  • prominent flow voids
• DWI / ADC: facilitated diffusion
• MRA: in some cases feeding vessels may be visible ¹ 

Treatment and prognosis

Although surgery is the mainstay of treatment, as is the case for other variants, the presence of such abundant blood supply can make surgery more difficult. As such pre-operative embolisation may be of benefit. 

Differential diagnosis

Other entities to be considered predominantly are extra-axial masses with high T2 signal and masses with prominent blood supply. These include:

• haemangiopericytoma
  • can appear very similar
  • less likely to have a dural tail ⁴
  • more likely to enhance heterogeneously ⁴
  • more likely to have microlobulation / irregular contour ⁴
  • perhaps counterintuitively ADC values are higher than in angiomatous meningiomas ⁴
  • bone and brain invasion more common
  • somewhat more common in younger males (vs. older females)
• microcystic meningioma and chordoid meningioma: usually do not have prominent flow voids
• haemangioblastoma
  • intra-axial (albeit peripheral) usually in the posterior fossa
  • typically cyst with an enhancing mural nodule