Phakomatoses are a group of neurocutaneous disorders characterised by involvement of structures that arise from the embryonic ectoderm (thus central nervous system, skin and eyes). Other organs may also be involved

Neurofibromatosis type 2 (NF2) is a rare autosomal dominant neurocutaneous disorder (phakomatosis) manifesting as development of multiple CNS tumours ^1-2. Unlike neurofibromatosis type 1 (NF1), it is not associated with neurofibromas.  Instead, patients with this disease have:

• 
  intracranial schwannoma(s) - mostly vestibular schwannoma(s)
  
• 
  intracranial and spinal meningioma(s)
  
• 
  intraspinal-intramedullary ependymoma(s).
  

These features suggest the mnemonic MISME which describes Multiple Inherited Schwannomas Meningiomas and Ependymomas ⁴. In fact, labeling this disorder neurofibromatosis type 2 is a misnomer, because neurofibromas are not a part of its constellation of abnormalities.⁵

There can also be associated syringohydromyelia with lesions in the spine ¹ as well as cataracts ³.

Epidemiology

The disease is rare with an estimated prevalence of 1:50000.

The neoplasms usually develop in adult patients - but the predisposition is inherited via a mutational loss of a tumor supressor gene on the long arm of chromosome 22.  This gene codes for a protein pNF2 or "schwannomin" - also called "merlin".

Although meningiomas are often an isolated findings in adults, their presence in a child should raise suspicion regarding NF2. The presence of mulitple and diffrent types spinal tumours also raise high suspicion of NF2 ¹