DTI has been essential to understanding the complexity and variability in brain injuries among CP children [9].
In this study, we assessed abnormalities on diffusion magnetic resonance imaging associated with CP. CP group included 46 (65.7 %) preterm children and 24 (34.3%) term children. The mean gestational weight was 2812.86 ± 503.52 (range, 1600–3800 g). The gestational age in infants with CP was less than those in controls. The birth weight of children with CP (2812.86 ± 503.52) was significantly lower than birth weight among the control group (3161.54 ± 181.28) (p = 0.001).
Such findings followed those of Schieve et al. [10], who reported that low birth weight-preterm and average birth weight-preterm were associated with CP. Also, coping with the study done by McIntyre et al. [11], it described that the smaller the infant for gestational age and the lower the birthweight, the higher CP risk.
In this study, we found that 26 (37.1%) of children suffer from perinatal hypoxia, whereas 36 (51.4%) were admitted to the intensive care infant unit following delivery. These findings are in coping with a study done by Mcintyre et al. [11], which conclude that birth asphyxia was the powerful and the most reliable predisposing factor for CP and also with a study done by Ahlin et al. [12], which conclude that a neonatal encephalopathy and NICU admission are among the most substantial risk factors for CP.
This study revealed that the most common brain lesions on conventional MRI were white matter lesions (60%), followed by grey matter lesions (8.6%), brain malformations (5.7%), and lastly, postnatal events (2.9 %). Finally, 22.9% of studied patients had normal conventional MRI findings.
These findings were in agreement with those of Bax et al. [13], who observed that conventional MRI scans demonstrated that white matter injuries, such as PVL, were the most typical feature (42.5%), followed by basal ganglia affection (12.8%), cortical/subcortical lesions (9.4%), malformations (9.1%), focal infarcts (7.4%), and miscellaneous disorders (7.1%). Only 11.7% of children showed normal MRI study.
Also, our results are coping with a study done by Franki et al. [14], which observed that most of the recorded lesions in CP cases are composed of white matter lesions (66.9% of entire lesions) then grey matter affection (18.6%) and brain malformations (4.3%). Of note, postnatal lesions developed in 16 children (1%) and the miscellaneous group (1%), while they (8.2%) show no insult on conventional MRI.
In contrast to conventional MRI, this study demonstrated a significant decrease in fractional anisotropy and fiber count and the CST on the affected side compared with control subjects. Also, there has been an increase in MD observed in this tract.
Such findings are consistent with those of Scheck et al. [15], who reported decreased FA and increased MD within the corticospinal pathway. These findings propose a reduction in CST integrity in comparison with typically developing children. Diffusion MRI and tractography research revealed additional proof of injury or perturbed initial development of this pathway.
Our results are also in the same line with those of Cho et al. [16] study who displayed that many DTI and DTT researches had demonstrated evidence of deficits in the CST of CP cases. The most expected recorded findings were the reduction in the number of fibers [17], reduction in FA, and increase in MD values [18].
These findings were in disagreement with those of Rha et al. [17], who reported that the numbers of fibers, but not FA or MD values, are lower in the CSTs in children with low gross motor function. This difference is due to the small sample size in a study done by Rha et al. [17], and the standard deviations were large, which was associated with more possible false-negative results. Besides, narrow age ranges of cases in which DTT was performed (between 7 months and 2.9 years) may be considered another explanation.
This study showed significant involvement (decrease in DTI fiber count) of the superior thalamic radiation (in severe cases) with atrophy of the ATR or posterior thalamic radiations (PTR) in most cases with a significant reduction in FA and increase in MD values.
These findings are coping with a study done by Trivedi et al. [7] in which a significant decrease in FA values was noted in both corticothalamic tracts moving from controls to GMFCS level V. Also, all the studied groups showed higher MD values in tract than the control group.
Also, our results agree with the study done by Arrigoni et al. [19], which discover that FA was significantly reduced in the thalamic radiations; therefore, such findings revealed the significance of sensory integration in the determinism of the multilevel damage in CP.
This result was different from that of Thomas et al. [20], whose research demonstrated significant involvement (decrease in DTI fiber count) of the superior thalamic radiation without a change in the ATR or PTR. Such difference between our results may be due to a small number of subjects included in Thomas et al. [20] with different age distribution.
This study also found a strong negative correlation of FA with a clinical motor grade in the corticothalamic and a corticospinal tract, which proposes that damaged corticothalamic tracts along with CST affection might have an essential role in the pathophysiology of motor dysfunction in CP cases.
Such findings are in the same line with a study done by Weinstein et al. [21], who described correlations between diffusion measures in motor and sensory tracts and motor functions.
This result was not coped with Lee et al. [22], who reported that FA mostly within CST demonstrated a more significant correlation with motor dysfunction in comparison with thalamocortical pathways. The difference in these results may be due to different CP (diplegic) types included in this study.
This study also revealed a significant negative correlation between fibers count and different levels of GMFCS with corresponding differences detectable on DTT in corticospinal tracts and corticothalamic radiation (Fig. 3). This agrees with that of Yoshida et al. [23], who observed that in CP cases with different GMF levels, there were difference in fiber count in CST and thalamic radiations.
The higher MD values in motor and sensory tracts of the CP cases compared with the control group may be secondary to increased extracellular water contents due to marked gliosis and microscopic/macroscopic cystic changes that occurred in affected areas [24]. In this study, the MD values in CP cases were higher in both sensory corticothalamic and motor corticospinal tracts compared to controls, with a significant positive correlation noticed among GMFCS grade and MD values in sensory and motor pathways, which reflects an increase in extracellular water content and gliosis with higher GMFCS levels.
These findings are coping with those of Trivedi et al. [7], who observed the significant correlation between MD values noted in sensory corticothalamic and motor corticospinal tracts with clinical motor grades assessed by GMFCS.
This study revealed high sensitivity and specificity of DTI quantitative and qualitative measures in evaluating the WM tracts injury underlying CP disorders. The current results confirmed that FA values had high diagnostic values. Significant variations in FA values were observed among CP patients, and controls with detectable cutoff values of FA within CST were 0.472 (left) and 0.449 (right) tracts, and within CTR were 0.44 (left) and 0.432 (right) tracts. The significant predictive power of FA within the CTR had the highest value of accuracy (AUC 0.965), showing 97.1% sensitivity, 76.9% specificity, 90.9% negative, and 91.9% positive predictive values on the left side and 94.3% sensitivity, 92.3% specificity, 85.7% negative, and 97.1% positive predictive values on the right side.
Previous research done in 2008 by Murakami et al. [25] demonstrated that an FA threshold of 0.5 within the CST was efficient in distinguishing CP and non-CP groups, and a study done by Jiang et al. [26] also revealed that FA threshold in CST for diagnosis of CP was 0.48 (left) and 0.49 (right).
This study suggests that sensory and motor tracts are affected in different degrees in CP cases, which lead to various clinical presentations in CP cases. These findings came following previous studies, which were carried out by Glenn et al. [27] and Thomas et al. [20], who suggest that both motor and sensory pathways are involved in CP patient with PVWI and a complex interplay of relative involvement of such pathways may define the terminal outcomes of such cases and not the degeneration of either of them alone.
Our results are in agreement with those of Scheck et al. [15], who demonstrated that marked impairment to descending motor and ascending sensorimotor tracts plays a role in the neuro-pathogenesis of CP and emphasize the significance of preservation of ascending sensorimotor networks in motor functions and also offer novel insights for the design of neurorehabilitation therapy.
Also, they consist of Jiang et al. [26] and Mailleux et al. [28], who demonstrated clear associations among upper limb function and white matter integrity of the descending CST and ascending thalamocortical tracts in unilateral CP cases.
The current study has some limitations. First, the parenchymal damage in CP cases, with loss of WM volume and ventricular enlargement, might interfere with creating a standard DTI template among cases and control and affect DTI outcomes. However, the current study displayed moderate to marked ventricular enlargement in 8.5% of CP cases. The second limitation is the lack of dyskinetic and ataxic types of CP.
