Correlation between anatomic landmarks and fMRI in detection of the sensorimotor cortex in patients with structural lesions

Language lateralization in pre-adolescent children: FMRI study using visual verb generation and word pair paradigms

Background: FMRI is a noninvasive tool for mapping language networks, especially in children. We conducted FMRI studies in children in the age group 8- 12 years using 2 different paradigms for assessing language networks and lateralization. Aim: To map language networks in pre-adolescent children and to calculate lateralization index using two different visual paradigms. Methods and Materials: The study was conducted in normal right handed children in the age group 8-12 years. Sixteen normal subjects underwent FMRI using 2 paradigms- visual verb generation (VVG), word pairs paradigm (WPP) to stimulate language areas. FMRI data analysis was done using SPM8 (statistical parametric Mapping) software. Total activated voxels were calculated for each hemispheres in the pre-defined ROIs for both paradigms. Results: FMRI showed left language lateralization in 13 out of 16 children with both VVG and WPP and bilateral language lateralization in two subjects. With VVG there was more significant activation in the left inferior triangular gyrus (ITG) (P < 0.001), left inferior opercular gyrus (IOG) (P < 0.01), left middle frontal gyrus (MFG) (P < 0.05), left and right dorsolateral prefrontal cortex (P < 0.05). Left posterior superior temporal gyrus (STG or WA) (P < 0.001), Left AG (P < 0.03), Left SMG (P < 0.05) were significantly activated with WP paradigm. Conclusion: Our FMRI studies showed that VGP predominantly activated frontal language areas and WPP predominantly activated temperoparietal language areas. Several other brain regions were also involved in language processing apart from the classical language areas.

The reliability of identifying the Omega sign using axial T2-weighted magnetic resonance imaging

Preoperative identification of the eloquent brain is important for neurosurgical planning. One common method of finding the motor cortex is by localizing "the Omega sign." No studies have tested the reliability of imaging to identify the Omega sign. We identified 40 recent and consecutive patients who had undergone preoperative functional magnetic resonance imaging for identification of the hand motor area prior to tumor resection. We recruited 11 neurosurgical residents of various levels of training and one board-certified neurosurgeon to identify the hand motor cortex Omega. Testees were given axial images of T2-weighted MRI and placed marks where they expected to find the Omega. Two board-certified radiologists graded and quantified the localization attempts. Inter-rater reliability was assessed using the kappa statistic, and Rao-Scott chi-square tests were used to examine the relationship between clinical factors and testees' experience with correct identification of the Omega sign. The overall correct identification rate was 69.9% (95% CI = 63.4-75.7), ranging from 36.6% to 92.7% among all raters for the tumor side and from 46.2% to 97.4% for the non-tumor side. Anatomic distortion greatly affected correct identification ( p < 0.005). Senior residents had a significantly higher rate of identification of the Omega than junior residents ( p < 0.001). Overall, inter-rater reliability for the Omega sign is poor, with a Fleiss kappa of 0.23. We concluded that correct identification of the Omega sign is affected by tumor distortion and experience but overall is not reliable. This underscores the limitations of anatomic landmarks and the importance of utilizing multiple scanning planes and preoperative fMRI for appropriate localization.

Morphometry of the Hand Knob Region and Motor Function Change in Eloquent Area Glioma Patients

PURPOSE

The hand knob area is the cortical representation of motor hand function. The current study aimed to investigate the effects of eloquent area gliomas on the morphometry of the hand motor cortex and preoperative hand motor function.

METHODS

A retrospective study of 320 glioma patients was conducted. Seventy-eight patients with gliomas involving motor functional area were finally enrolled. Using axial T2-weight magnetic resonance images, the width and height of the hand knob were measured in both hemispheres, and differences were compared between the affected and unaffected hemispheres. Receiver operating characteristic (ROC) curve and logistic regression analysis were used to estimate the degree of correlation between distance measurements and motor impairment.

RESULTS

The width and height of the hand knob in the affected and unaffected hemispheres were significantly different (p < 0.0001). The width, height and distance from the tumor to hand knob were reduced in the functionally impaired group compared to the unimpaired group (p = 0.0003, p < 0.0001, p = 0.0005, respectively). The three parameters were significantly correlated and remained significant in ROC and logistic regression analysis. The optimal cut-off value of width, height and distance for identifying preoperative hand muscle strength were 5.73 mm, 5.80 mm and 5.92 mm, respectively.

CONCLUSION

The morphometry of the hand knob is often changed by the infiltration or extrusion of the tumors that were located in or near the hand knob. The width, height of hand knob and the distance from tumor to hand knob could serve as anatomic biomarkers related to preoperative neurological motor deficits.

The "White Gray Sign" Identifies the Central Sulcus on 3T High-Resolution T1-Weighted Images

BACKGROUND AND PURPOSE

The central sulcus is an important anatomic landmark, but most methods of identifying it rely on variable gyral and sulcal patterns. We describe and assess the accuracy of reduced gray-white contrast along the central sulcus, an observation we term the "white gray sign."

MATERIALS AND METHODS

We conducted a retrospective review of 51 fMRIs with a T1-weighted 3D inversion recovery fast-spoiled gradient-echo and concomitant hand-motor fMRI, which served as confirmation for the location of the central sulcus. To measure gray-white contrast across the central and adjacent sulci, we performed a quantitative analysis of 25 normal hemispheres along the anterior and posterior cortices and intervening white matter of the pre- and postcentral gyri. 3D inversion recovery fast-spoiled gradient-echo axial images from 51 fMRIs were then evaluated by 2 raters for the presence of the white gray sign as well as additional established signs of the central sulcus: the bracket, cortical thickness, omega, and T signs.

RESULTS

The mean gray-white contrast along the central sulcus was 0.218 anteriorly and 0.237 posteriorly, compared with 0.320 and 0.295 along the posterior precentral and anterior postcentral sulci, respectively (P < .001). Both raters correctly identified the central sulcus in all 35 normal and 16 abnormal hemispheres. The white gray sign had the highest agreement of all signs between raters and was rated as present the most often among all the signs.

CONCLUSIONS

Reduced gray-white contrast around the central sulcus is a reliable sign for identification of the central sulcus on 3D inversion recovery fast-spoiled gradient-echo images.

Success rates for functional MR imaging in children

BACKGROUND AND PURPOSE

Functional MR imaging is widely used for research in functional brain development in healthy children. However, obtaining high-quality brain imaging data from pediatric research participants requires cooperation that is challenging for young children. In this study, we examined success rates for fMRI in typically developing children in both longitudinal and cross-sectional research study designs to inform the recruitment needs of future pediatric brain imaging studies.

MATERIALS AND METHODS

In the cross-sectional study, 459 healthy children (5-18 years of age, 215 girls) were recruited. A subset of 30 healthy children 5-7 years of age from the cross-sectional cohort were selected and scanned for 10 consecutive years in the longitudinal arm of the study. Following anatomic scans, each participant attempted 4 functional MR imaging tasks. Success rate was defined as the proportion of fMRI tasks completed. Differences in success rates across sexes and in cross-sectional-versus-longitudinal cohorts were evaluated by using the Fischer exact test.

RESULTS

In the cross-sectional study, 74% of the children completed all tasks. Success rates for individual tasks ranged from 34% to 67% for children 5-7 years of age and 76%-100% for those 8-18 years of age. In the longitudinal study, 89% of children completed all tasks in all 10 years. We established significance (P < .0001) between the cross-sectional and longitudinal cohorts for both 0% and 100% task completion rates. There was no significance between sexes.

CONCLUSIONS

When designing pediatric fMRI studies in children, the sample sizes indicated by power analysis should be scaled up according to age (ie, 33% for ages 8-18 years, 50% for ages 5-7 years).