NF2 and schwannoma: In schwannomas, the loss of inhibitory effects of merlin can activate the mitogen-activated protein/ERK kinase (MEK)/extracellular signal-regulated kinase (ERK) cascade and the phosphatidylinostitol-3 kinase (PI3K)/serine-threonine protein kinase/Akt cascade, which can cause cellular growth and proliferation in schwannomas (Figure 2) [26,28].