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Diffusion tensor imaging of frontal lobe in autism spectrum disorder.

Sundaram SK, Kumar A, Makki MI, Behen ME, Chugani HT, Chugani DC - Cereb. Cortex (2008)

Bottom Line: The fiber length distribution was significantly more positively skewed in the normal population than in the ASD group (P < 0.001).The long range association fibers of frontal lobe were significantly longer in ASD group (P = 0.026 for both left and right hemispheres).Lack of evidence for excessive short range connectivity in ASD in this study may need to be re-examined with future advances in DTI technology.

View Article: PubMed Central - PubMed

Affiliation: Carman and Ann Adams Department of Pediatrics, Children's Hospital of Michigan, 3901 Beaubien Blvd, Detroit, MI 48201, USA. ssundaram@pet.wayne.edu

ABSTRACT
To investigate frontal lobe white matter in children with autism spectrum disorder (ASD), we performed diffusion tensor imaging (DTI) in 50 ASD children (mean age: 57.5 +/- 29.2 months, 43 males) and 16 typically developing children (mean age: 82.1 +/- 41.4 months, 11 males). The apparent diffusion coefficient (ADC) was significantly higher for whole frontal lobe (P = 0.011), long (P < 0.001) and short range (P = 0.0126) association fibers in ASD group. There was a trend toward statistical significance in the fractional anisotropy (FA) of whole frontal lobe fibers (P = 0.11). FA was significantly lower in ASD group for short range fibers (P = 0.0031) but not for long range fibers (P = not significant [NS]). There was no between-group difference in the number of frontal lobe fibers (short and long) (P = NS). The fiber length distribution was significantly more positively skewed in the normal population than in the ASD group (P < 0.001). The long range association fibers of frontal lobe were significantly longer in ASD group (P = 0.026 for both left and right hemispheres). Abnormal frontal FA and ADC may be due to white matter organization abnormalities in ASD. Lack of evidence for excessive short range connectivity in ASD in this study may need to be re-examined with future advances in DTI technology.

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Histogram of fiber lengths in (A) the control group, (B) the ASD group, (C) a 38-month-old control child, and (D) a 34-month-old autistic child. The y axis represents the ratio of the number of fibers of given length to the total number of frontal lobe fibers (expressed as percentage). Note that the 2nd peak (located between the 2 vertical bars) is shifted to the right in the ASD group. The 2nd peak corresponds to the long range association fibers.
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fig2: Histogram of fiber lengths in (A) the control group, (B) the ASD group, (C) a 38-month-old control child, and (D) a 34-month-old autistic child. The y axis represents the ratio of the number of fibers of given length to the total number of frontal lobe fibers (expressed as percentage). Note that the 2nd peak (located between the 2 vertical bars) is shifted to the right in the ASD group. The 2nd peak corresponds to the long range association fibers.

Mentions: There was a highly significant positive correlation between average length of all frontal lobe fibers and the average length of fibers of whole brain (r = 0.75, P < 0.0001 for left frontal fibers and r = 0.74, P < 0.0001 for right frontal fibers). We found that there was no difference in the mean length of the fibers of whole brain (P = 0.26) or of the frontal lobes between the 2 groups (P = 0.88 for all frontal lobe fibers and P = 0.27 for short fibers). Even though the average length of the fibers was not different, the distribution of fiber length differed between the control and ASD groups. In particular, the fiber length distribution was significantly more positively skewed in the normal population than in the ASD group (P < 0.001). Upon visual examination, the histograms of fiber lengths showed a bi-modal distribution with a smaller peak corresponding to long range fibers (Fig. 2). When the fibers corresponding to this 2nd peak were isolated, the average length of these long fibers was significantly higher in ASD than in controls (P = 0.026 for both left and right hemispheres). In order to examine whether there is excessive short range connectivity, we also investigated the number of short and long association fibers in the frontal lobe. We did not find any differences between the 2 groups (P = 0.429 for left hemisphere and P = 0.217 for right hemisphere). The number and length of fibers is summarized in Table 3.


Diffusion tensor imaging of frontal lobe in autism spectrum disorder.

Sundaram SK, Kumar A, Makki MI, Behen ME, Chugani HT, Chugani DC - Cereb. Cortex (2008)

Histogram of fiber lengths in (A) the control group, (B) the ASD group, (C) a 38-month-old control child, and (D) a 34-month-old autistic child. The y axis represents the ratio of the number of fibers of given length to the total number of frontal lobe fibers (expressed as percentage). Note that the 2nd peak (located between the 2 vertical bars) is shifted to the right in the ASD group. The 2nd peak corresponds to the long range association fibers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2567426&req=5

fig2: Histogram of fiber lengths in (A) the control group, (B) the ASD group, (C) a 38-month-old control child, and (D) a 34-month-old autistic child. The y axis represents the ratio of the number of fibers of given length to the total number of frontal lobe fibers (expressed as percentage). Note that the 2nd peak (located between the 2 vertical bars) is shifted to the right in the ASD group. The 2nd peak corresponds to the long range association fibers.
Mentions: There was a highly significant positive correlation between average length of all frontal lobe fibers and the average length of fibers of whole brain (r = 0.75, P < 0.0001 for left frontal fibers and r = 0.74, P < 0.0001 for right frontal fibers). We found that there was no difference in the mean length of the fibers of whole brain (P = 0.26) or of the frontal lobes between the 2 groups (P = 0.88 for all frontal lobe fibers and P = 0.27 for short fibers). Even though the average length of the fibers was not different, the distribution of fiber length differed between the control and ASD groups. In particular, the fiber length distribution was significantly more positively skewed in the normal population than in the ASD group (P < 0.001). Upon visual examination, the histograms of fiber lengths showed a bi-modal distribution with a smaller peak corresponding to long range fibers (Fig. 2). When the fibers corresponding to this 2nd peak were isolated, the average length of these long fibers was significantly higher in ASD than in controls (P = 0.026 for both left and right hemispheres). In order to examine whether there is excessive short range connectivity, we also investigated the number of short and long association fibers in the frontal lobe. We did not find any differences between the 2 groups (P = 0.429 for left hemisphere and P = 0.217 for right hemisphere). The number and length of fibers is summarized in Table 3.

Bottom Line: The fiber length distribution was significantly more positively skewed in the normal population than in the ASD group (P < 0.001).The long range association fibers of frontal lobe were significantly longer in ASD group (P = 0.026 for both left and right hemispheres).Lack of evidence for excessive short range connectivity in ASD in this study may need to be re-examined with future advances in DTI technology.

View Article: PubMed Central - PubMed

Affiliation: Carman and Ann Adams Department of Pediatrics, Children's Hospital of Michigan, 3901 Beaubien Blvd, Detroit, MI 48201, USA. ssundaram@pet.wayne.edu

ABSTRACT
To investigate frontal lobe white matter in children with autism spectrum disorder (ASD), we performed diffusion tensor imaging (DTI) in 50 ASD children (mean age: 57.5 +/- 29.2 months, 43 males) and 16 typically developing children (mean age: 82.1 +/- 41.4 months, 11 males). The apparent diffusion coefficient (ADC) was significantly higher for whole frontal lobe (P = 0.011), long (P < 0.001) and short range (P = 0.0126) association fibers in ASD group. There was a trend toward statistical significance in the fractional anisotropy (FA) of whole frontal lobe fibers (P = 0.11). FA was significantly lower in ASD group for short range fibers (P = 0.0031) but not for long range fibers (P = not significant [NS]). There was no between-group difference in the number of frontal lobe fibers (short and long) (P = NS). The fiber length distribution was significantly more positively skewed in the normal population than in the ASD group (P < 0.001). The long range association fibers of frontal lobe were significantly longer in ASD group (P = 0.026 for both left and right hemispheres). Abnormal frontal FA and ADC may be due to white matter organization abnormalities in ASD. Lack of evidence for excessive short range connectivity in ASD in this study may need to be re-examined with future advances in DTI technology.

Show MeSH
Related in: MedlinePlus