| Popis: |
A large group of clinical entities have been described whose common underlying cause has been premature fusion of the cranial sutures. Many have a common symp tomatology manifest by varying degrees of optic atrophy, convulsions, headaches, and mental deficiency secondary to increased intracranial pressure. Other cases have pre sented only the external cranial deformity without any symptoms of increased pressure at any time during their life, the only evi dence thereof being the convolutional mark ings of the skull seen roentgenographically. Briefly, it will be recalled that the defini tive skull is formed by the fusions and modi fications of skeletal elements enclosing the neural tube and supporting the visceral arches. The mesenchyme in the region of the future basis cranii and in the visceral arches undergoes chondrification before ossifying; whereas, most of the side walls and cranial vault ossify directly from fibrous connective tissue. Thus the bones of the cranium are either substitution bones, replacing cartilage, or they are bones of intramembranous ori gin. At the precartilage stage, the tip end of the notochord and the sensory capsules (nasal, optic, and otic) are enclosed in dense precartilaginous mesenchyme. At the carti lage state, there is a fusion of the cartilage of the basis cranii with the nasal and otic cartilaginous capsules. Later on anterior placement and fusion of the optic capsules occurs. JD F. J. PlNKERTON, M.D. Hawaii |
