achondroplasia treatmenthydrocephalus ventriculostomyachondroplasia characteristicscommunicating hydrocephalus treatmentcongenital hydrocephalus treatmentobstructive hydrocephalus treatmentheterozygous achondroplasiaachondroplasia descriptionachondroplasia complicationshomozygous achondroplasiaachondroplasia inheritanceachondroplasia mutation