Crouzon syndrome: posterior fossa volume studies in vestibular orientation

With the increasing possibilities of surgical treatment addressing the complex spectrum of defects in Crouzon syndrome (CS), it is of utmost importance to obtain accurate assessment of the malformation. Evaluating the volume of the posterior fossa is of great importance since many authors, considering that its volume is always decreased, favor posterior fossa enlargement as a first step in the treatment of CS.

We studied CT scans of children with CS, which were vestibular-oriented (VO) in order to conform with physiological landmarks, and we measured intracranial volume by manual segmentation; these abnormal CT scans were superposed with VO 3D-CT scanners of age-matched controls. We studied the volume index of the posterior fossa for each CS patient defined as the ratio of its volume in CS patients with the normal for age calculated from normal controls.

We studied the imaging of 41 children with CS and 70 control. Among CS patients, the volume of the posterior fossa was increased in 10, compared with control. We found closure of the sphenoidal synchondrosis was correlated with age and with the width of the posterior fossa, but not with its length nor with the posterior fossa volume index.

Segmentation on VO-CT scanner and superposition with CT scanners of normal controls is a powerful tool for the study of the impact of CS or other synostoses on volume and shape. We found that CS is more heterogeneous than previously thought, and surgical strategies should be adapted accordingly.