Classification and Clustering Applications - An Invariant Approach to Statistical Analysis of Shapes - page 250

the calvarium of children diagnosed with premature closure of the
sagittal suture is long and narrow relative to a normal skull ( Figure
1.4b ). Additional sutures are present on the calvarium ( Figure 1.4a )
and premature closure of any of the other sutures results in abnor-
mally shaped skulls. When the metopic suture is closed prematurely,
the frontal bone (forehead) becomes pointed and the skull appears tri-
angular in shape when viewed from above. When either the right or
left coronal suture is closed prematurely, the skull takes on an asym-
metric shape when viewed from the top with the forehead and orbit
compressed on the synostosed side. There can also be flattening of the
posterior aspect of the same side and bulging of the neurocranium on
the posterior aspect of the unaffected side (see Figure 7.2 ).
Asymmetric deformation of the developing skull can occur even when
all sutures remain open. Typically, these skull deformations mimic the
appearance of either premature closure of one coronal suture or one
lambdoid suture. Crowding in the womb or repeated placement of the
infant in a particular sleeping position can result in flattening of one
side of the back of the skull. This deformity is referred to as plagio-
cephaly (literally, twisted skull) and does not involve craniosynostosis
(i.e., all sutures remain open). Data sets for this example include land-
mark coordinate data collected from samples of individuals diagnosed
with posterior plagiocephaly, meaning that the flattened part of their
skull was evident on the more posterior aspect, unicoronal synostosis
(where the coronal suture closes prematurely), metopic synostosis
(where the metopic suture closes prematurely), and sagittal synostosis
(premature closure of the sagittal suture) (see Chapter 1 ). Both uni-
coronal synostosis and posterior plagiocephaly can occur on either the
right or left side of the skull, and our sample contains children with
both right and left unicoronal synostosis and right and left posterior
plagiocephaly. For the cross validation study presented below, we
reflected all right-sided unicoronal and posterior plagiocephaly cases
such that all cases were left-sided for analysis.
Most children that present with obviously misshapen skulls are
referred to a specialist for consultation. Often a computed tomography
scan is necessary to determine whether or not a suture is truly closed
and to provide information for clinical correction of the deformity
(either by surgery or by a device). Landmark data were collected from
computed tomography images of children diagnosed with sagittal syn-
ostosis ( N =25), metopic synostosis ( N =11), unicoronal synostosis ( N =4),
and posterior plagiocephaly ( N =9). The landmarks were identified on
the cranial base (that part of the skull underlying and surrounding the