Diagnosis

History

Meningioma has a variable presentation depending on its site of origin.

  • Symptoms of mass effect are uncommon (as opposed to high grade glial tumours)
  • Visual field changes occur with central base of skull lesions adjacent to the sellar region
  • Motor or sensory changes can occur with meningiomas adjacent to the central sulcus, or when lesions arise adjacent to the brainstem
  • Seizures occur in about 1/3rd of patients as an initial presentation
  • Meningioma is found in about 1% of the asymptomatic population that undergo MRI

Examination

Full neurological examination should be performed. This can identify the site of a meningioma; for example, visual field defects suggest a lesion near the cavernous sinus or optic chiasm.

Imaging

Meningiomas are highly vascular and therefore intensely bright on contrast studies. MRI provides improved resolution and distinction from normal brain than CT and is the 'gold standard' test. The characteristic finding is the 'tail sign', where the dura is thickened adjacent to the mass and thins more distantly.

Histological Diagnosis

The imaging findings are highly suggestive of meningioma, but formal diagnosis should be done; this may simply be at the time of surgery. Some deep seated meningiomas may be highly morbid to biopsy and in these cases treatment may be undertaken on the presumption of meningioma (if the imaging findings are characteristic).

Staging

Meningiomas are not staged through TNM. There are three grades of meningioma:

  • WHO Grade 1 (meningioma) are thoroughly benign. The recur in < 10% of cases following complete surgical resection.
  • WHO Grade 2 (atypical meningioma) are characterised by a higher mitotic count (4-20 per 10 HPF) and other adverse histological features (necrosis, sheet-like growth, small cells, increased cellularity, or prominent nucleoli). About 1/4th of meningiomas are Grade 2
  • WHO Grade 3 (malignant meningioma) are rare (2%). They have a high mitotic count (> 20 per 10 HPF), carcinoma/sarcoma/melanoma features, or rhabdoid/anaplastic/papillary patterns.

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