Grade 2###Clear separation of the synchondrosis is seen along most sections, except for some areas that are indistinct or suspicious
Grade 3###There is an area of fusion or bridging across a portion of the synchondrosis
Grade 4###Complete fusion of the synchondrosis with remnant sclerotic margin
The posterior intraoccipital synchondrosis showed initial evidence of closure (grade 2) in 78% of the cases from age of 18 months with a mean age of 23 months.
The anterior intraoccipital synchondrosis showed signs of early fusion (grade 2) starting from the age of 3 years and 6 months with a mean age of four years.
[6], found that fusion of anterior intraoccipital synchondrosis began during the second year and displayed grade 4 level of fusion between the ages of 7 and 10 years.
The sphenooccipital synchondrosis showed wide variation in the age demonstrating initial CT evidence of fusion (grade 2), ranging from 4-10 years with the mean age of 7.5 years in 68% of cases, and reached grade 4 at a mean age of 15 years.
Madeline, [4] who found that the sphenooccipital synchondrosis showed signs of early fusion by the age of 8 years and reached grade 4 of closure at 16 years.