Two and a half years old fontanel is still not closed may be the emergence of rickets, hydrocephalus and other diseases. 1. rickets, generally this case, one and a half to two years old fontanel has closed, if two and a half years old fontanel is not closed may be related to rickets, if the body lacks calcium, vitamin D, may lead to growth and development is affected, so this symptom will appear. 2. Hydrocephalus, if the baby hydrocephalus may lead to the skull development is affected, can not be normal development, so there will be two and a half years old fontanel is not closed symptoms. Usually need to observe the baby’s development, if found to have obvious discomfort, need to timely medical examination and treatment.