The authors report 14 cases of multiple intracranial meningiomas representing 1.1% of all meningiomas operated on at their hospital in the past 35 years. Differentiation of multiple meningiomas, especially from meningiomatosis, must be strict. Since the introduction of computerized tomography scanning, the frequency of these cases has risen from 0.58% to 4.5% in the authors' meningioma series. Despite the multiplicity of sites, multiple meningiomas do not differ in prognosis from benign solitary meningiomas.

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Syringomyelia associated with posterior fossa tumours is a very infrequent combination of pathological entities. The few cases which have been reported generally were asymptomatic in respect of the spinal cavitations. The authors report on a 36-year-old woman with a large extradural posterior fossa epidermoid tumour with a concomitant holocord symptomatic syringomyelia. Some of her symptoms were clearly attributed to the intraspinal cavitation. The lesions were both diagnosed by magnetic resonance imaging (MR). The patient did well after surgery of the brain lesion, with an objective improvement in her neurological status and a complete resolution of the syrinx documented by the MR 7 months after tumour removal. Syringomyelia in this case could be explained by blockage of the cerebrospinal fluid (CSF) circulation at the foramen magnum which in turn resulted in cranio-spinal pressure dissociation. This led to an accumulation of extracellular fluid (ECF) in the central canal, starting cavitation. Consequently, the syrinx was slowly expanded by the long-standing "slosh" effect of the systolic pressure waves. However, also via a distortion mechanism within the posterior fossa a pathologically plugged obex could have contributed to syrinx formation by means of preventing drainage of fluid from the ventricular CSF system.

The en-bloc cranioplastic approach with preservation of the mastoid process is a new, interesting variant of a classical technique that is easy to perform and has the intention of achieving the best possible cosmetic result.

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