Syndromes Associated with Intracranial Tumours: A Paediatric Neurosurgeon’s Perspective

rare and may be the result of chance rather than some increased risk for both conditions.In terms of the current chapter, these three disorders, as well as more-recently described phakomatoses, share the property of being associated with an increased risk of malignancies involving the central and, sometimes, peripheral nervous system. NeurofibromatosisNeurofibromatosis (NF) is the most common of all the phakomatosis syndromes, having been initially described by Frederick von Recklinghausen in the year 1882 (Crump, 1981).Also initially called von Recklinghausen's disease, the disorder received public attention in the highly-acclaimed 1981 movie, The Elephant Man, which portrayed the life of Joseph Merrick (who was erroneously called John in the film); though some controversy exists as to whether Merrick truly suffered from neurofibromatosis, another condition called Proteus syndrome, or some combination of the two (Legendre et al., 2011).For the purposes of this chapter, what is most significant is that, whereas CNS tumours are the rule in both types of neurofibromatosis, Proteus Syndrome generally is not associated with CNS tumours (Satter, 2007).Proteus syndrome is also much less common than neurofibromatosis, with a prevalence of less than one in one million (Legendre et al., 2011).In fact, neurofibromatosis is now recognized not to be one, but at least two distinct disorders: neurofibromatosis type 1 (NF-1) and neurofibromatosis type 2 (NF-2) (Ferner, 2007).Each of these two syndromes has its own diagnostic criteria that are very different; and whereas the characteristic lesion in NF-1 is the neurofibroma, the characteristic lesion in NF-2 is a peripheral nerve Schwannoma or neurolemoma (Pearce, 2003;Ferner, 2007;Lu-Emerson and Plotkin, 2009a;Lu-Emerson and Plotkin, 2009b).Neurofibromatosis has been further subcategorized beyond just neurofibromatosis types 1 and 2, into milder and more severe forms of NF-2 (Gardner syndrome and Wishart or Lee-Abbott Syndrome, respectively); segmental NF-1 and NF-2; and other variants of NF, including mixed NF.All forms of the disease appear to be autosomal dominant, though they are phenotypically highly variable, in terms of the presenting features and syndrome severity, even within a given family and when comparing monozygotic twins, suggesting the involvement of other disease-modifying genes and/or additional non-hereditary influences like second hit somatic events, environmental agents, epigenetic modification, and post-zygotic mutations (Rieley et al., 2011).This makes it difficult to advise parents regarding the risk to their future offspring, because a parent with very mild disease may have a child with severe involvement, or vice versa. Neurofibromatosis type 1Neurofibromatosis type 1 (NF-1) is the most common form of disease, affecting one in roughly 2500 to 5000 live births (Evans et al., 2010;Ferner et al., 2007;Legendre et al., 2011).This renders it more than ten times more common than NF-2(Evans et al., 2010;Ferner et al., 2007).Though autosomal dominant, up to 50% of cases arise spontaneously from a gene mutation that occurs on chromosome 17q11.2,which encodes for a large protein called neurofibromin (Evans et al., 2010;Legendre et al., 2011).This NF-1 gene is a classical tumour suppressor gene, with tumour growth requiring the loss of BOTH alleles.Neurofibromatosis type 1 has a classical combination of clinical signs (Ferner, 2010), for which the mnemonic CHANSOR has been used.These signs include Café au lait macules; Hamartomas of the iris (called Lisch nodules); Axillary and Inguinal Freckling; www.intechopen.com

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