The normal range of posterior fossa volume varies depending on age, gender, and body size. In adults, the average posterior fossa volume ranges from approximately 150 to 200 cubic centimeters (cc). However, in children, the average volume is smaller, ranging from approximately 100 to 150 cc.
Abnormalities in the size or shape of the posterior fossa can be indicative of certain medical conditions. For example, an enlarged posterior fossa can be a sign of a Chiari malformation, which is a condition where the brain tissue extends into the spinal canal. On the other hand, a smaller-than-normal posterior fossa can be a sign of Dandy-Walker syndrome, which is a rare congenital brain malformation.
C1 Laminectomy was effective in increasing posterior fossa volume expansion, both with and without duraplasty. A more rapid decrease in syrinx volume occurred when C1 Laminectomy was combined with duraplasty 1).
A greater increase in the postoperative PCF volume, and specifically an increase in the cisterna magna volume, was associated with a greater likelihood of clinical improvements in headache and tonsillar descent in patients with CM-I. Larger increases in the caudal portion of the posterior fossa volume were also associated with a greater likelihood of improvement in syrinx and cervicomedullary kinking 2).