Biomedical Engineering Reference
In-Depth Information
Recently, a two-dimensional voxel-based morphometric study, accounting for an
age effect, has reported significant white matter deficiency in the splenium of the
CC, but showed no significant difference in the middle body [27]. Sixteen autistic
and 12 control subjects, all right-handed males with one ambidextrous subject,
participated in this study. The average age for autistic boys is 16
.
1
±
4
.
5 and for
controls 17
.
1
±
2
.
8. A later study by Waiter et al. [28] reported reductions in the
isthmus and the splenium of the CC in autistic patients. In addition, abnormalities
of fractional anisotropy, “
a measure derived from diffusion tensor data that is
sensitive to developmental changes and pathological differences in axonal density,
size, myelination, and the coherence of organization of fibers within a voxel,
”in
the anterior CC were noted in a study using diffusion tensor imaging (DTI) by
Barnea-Goraly et al. [29]. Most recently, computational mapping methods were
used in an MRI study by Vidal et al. [30] to investigate CC abnormalities in male
patients with autism. Twenty-four boys with autism (age 10
±
3
.
3 years; range 6-
16 years) and 26 healthy boys (age 11
.
0
±
2
.
5 years; range 6-16 years) participated
in that study. Contrary to the traditional volumetric studies that have reported a
significant reduction in the total callosal area and the anterior subregion of the
CC in patients with autism, this study revealed significant reductions in both the
splenium and genu of the CC in autistic sufferers relative to controls. Similarly,
MRI studies of the hippocampus and the amygdale have reported inconsistent
findings. The volume of these structures was found to be increased, decreased, or
similar in autistic patients relative to control cases [31].
Cerebellum
The cerebellum is a part of the human brain located in the lower back of the
brain. This structure plays a major role in the integration of sensory perceptions
and motor output through neural connections with the motor cortex. Most neu-
ropathological studies of autistic individuals agree on the decreased number of
Perkinje cells in cerebellar hemispheres, vermis, and cerebellum. Williams et al.
[32] were the first to examine cortical and subcortical structures and the cerebellum
in four autistic individuals (three males, 12, 27, and 33 years old, and a 3-year-old
female, all mentally retarded and two with seizures). They reported a reduction of
the Perkinje cell density in one case. Lately, Ritvo et al. [33] reported a decreased
number of Perkinje cells in the cerebellar hemisphere and the vermis, in a study
involving three mentally retarded autistic males and none with seizures, and three
male controls. Other studies have followed and showed the same results [34, 35].
However, few studies reported no abnormalities in the cerebellum of some autistic
patients [20].
The first MRI study to examine the cerebellum was conducted by Courchesne
et al. [36]. This study showed a reduction in the area of the neocerebellar ver-
mis, which is consistent with the pathological studies noting reduced Perkinje cell
density in autism. Other MRI studies have reported an increased volume in cere-
