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2) as part of the hereditary syndrome neurofibromatosis type 2 (NF2);
3) multiple or familial aggregation of meningiomas.
The first group involves the majority of the cases and consists of tumors occurring randomly
(not associated with a hereditary syndrome) in the general population. The second one
involves meningiomas found in individuals with NF2. The diagnostic criteria for NF2 are
depicted in table 2 (Evans et aI., 1992b).
Table 2,
Diagnostic cl'itel'ia ror Nfl
Bilateral vestibular schwannomas 01' family history of NF2 plus
1) unilateral vestibular schwannoma 01'
2) any two of: meningioma, glioma, neurofibroma, schwannoma, posterior
subcapsular lenticular opacities.
This disorder may be divided in at least two distinct forms. One is called Wishart type and
has an early onset, rapid course and multiple tumors in addition to bilateral vestibular
schwannomas. The other, Gardner type, is characterized by a later age of onset, a more
benign course and is usually limited to bilateral vestibular schwannomas (Evans et aI.,
1992b). In both categories meningiomas can occur. The third group consists of patients with
multiple or familial aggregation of meningiomas without evidence of NF2. In this group, at
least in some of the cases, a predisposing mutation is probably involved (Chapter VII). It
remains to be established whether these different groups arise as a result of different
mutations in one gene or that different genes or combination of genes are involved.
4.3 Anatomic localization
According to Russell and Rubinstein (1989) meningiomas can be found at seven different
sites in the body: I) intracranial; 2) spinal; 3) intraventricular; 4) orbital; 5) intrapetrous; 6)
(extra-) calvarial and 7) ectopic. The intracranial and spinal meningiomas are the most
common ones. These tumors are often further subdivided in base (sphenoid ridge, tuberculum
sellae, olfactory grooves, pontocerebellar angle, petrous ridge of the temporal bone, posterior
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