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Robert J. Ogg, Fred H. Laningham, Dave Clarke, Stephanie Einhaus, Ping Zou, Michael E. Tobias and Frederick A. Boop

Object

In this study, the authors examined whether passive range of motion (ROM) under conscious sedation could be used to localize sensorimotor cortex using functional MR (fMR) imaging in children as part of their presurgical evaluation.

Methods

After obtaining institutional review board approval (for retrospective analysis of imaging data acquired for clinical purposes) and informed consent, 16 children underwent fMR imaging. All 16 had lesions; masses were found in 9 patients and cortical dysplasia was found in 4; the lesions in 3 patients were not diagnosed. Passive ROM was performed during blood oxygen level–dependent MR imaging sequences. Three of the patients also performed active motor tasks during the fMR imaging study. All patients were evaluated using passive ROM of the hand and/or foot; 3 patients were evaluated for passive touch of the face. In 9 cases, intraoperative electrocorticography (ECoG) was used. Five of the patients underwent intraoperative ECoG to evaluate for seizure activity. Four patients had intraoperative ECoG for motor mapping. Five of the patients had subdural grids placed for extraoperative monitoring.

Results

In 3 cases, the active and passive ROMs colocalized. In 4 patients ECoG was used to identify motor cortex, and in all 4 motor ECoG yielded results consistent with the passive ROM localization. Thirteen of 16 children have undergone resection based on passive ROM fMR imaging findings with no unanticipated deficits.

Conclusions

These preliminary data suggest that passive ROM fMR imaging can accurately detect functional hand, leg, and face regions of the sensorimotor cortex in the sedated child. This extends current extraoperative mapping capabilities to patients unable or unwilling to cooperate for active motor tasks.

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Weier Li, Scott D. Wait, Robert J. Ogg, Matt A. Scoggins, Ping Zou, James Wheless and Frederick A. Boop

Object

Advances in brain imaging have allowed for more sophisticated mapping of crucial neural structures. Functional MRI (fMRI) measures local changes in blood oxygenation associated with changes in neural activity and is useful in mapping cortical activation. Applications of this imaging modality have generally been restricted to cooperative patients; however, fMRI has proven successful in localizing the motor cortex for neurosurgical planning in uncooperative children under sedation. The authors demonstrate that the use of fMRI to localize the visual cortex in sedated children can be safely and effectively performed, allowing for more accurate presurgical planning to spare visual structures.

Methods

Between 2007 and 2009, 11 children (age range 1–11 years) underwent fMRI for neurosurgical planning while under sedation. Blood oxygen level–dependent fMRI was performed to detect visual cortex activation during stimulation through closed eyelids. Visual stimulation was presented in block design with periods of flashing light alternated with darkness.

Results

Functional MRI was successful in identifying visual cortex in each of the 11 children tested. There were no complications with propofol sedation or the fMRI. All children suffered from epilepsy, 5 had brain tumors, and 1 had tuberous sclerosis. After fMRI was performed, 6 patients underwent surgery. Frameless stereotactic guidance was synchronized with fMRI data to design an approach to spare visual structures during resection. There were no cases where a false negative led to unexpected visual field deficits or other side effects of surgery. In 2 cases, the fMRI results demonstrated that the tracts were already disrupted: in one case from a prior tumor operation and in another from dysplasia.

Conclusions

Functional MRI for evaluation of visual pathways can be safely and reproducibly performed in young or uncooperative children under light sedation. Identification of primary visual cortex aids in presurgical planning to avoid vision loss in appropriately selected patients.

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Nicholas S. Phillips, Robert A. Sanford, Kathleen J. Helton, Frederick A. Boop, Ping Zou, Tanya Tekautz, Amar Gajjar and Robert J. Ogg

✓Brainstem gliomas are a heterogeneous group of lesions that account for 15% of all pediatric tumors of the central nervous system. Diagnosis and treatment planning for these tumors is based on the observation of Epstein and Farmer that the growth of lesions with low malignant potential is limited by the anatomical structures of the brainstem. Surgery is offered only to those patients with a high probability of harboring a low-grade tumor, because the attendant risk for significant morbidity outweighs the therapeutic benefit of debulking the tumor in cases of high-grade tumors.

The authors report two cases that highlight the potential of diffusion tensor (DT) imaging to identify local white matter tracts in the pons, medulla, and cervical cord and to improve the preoperative assessment of low-grade gliomas. Preoperative DT imaging in both cases demonstrated that the white matter tracts were displaced by the bulk of the low-grade tumors but were structurally preserved. Intraoperative and neurological findings were consistent with the preoperative interpretation of the DT images. These cases demonstrate that DT imaging is a useful method for visualizing the relationship between tumor and normal brainstem white matter architecture, as well as for improving the surgical evaluation and management of pediatric brainstem tumors.

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Kathleen J. Helton, James K. Weeks, Nicholas S. Phillips, Ping Zou, Larry E. Kun, Raja B. Khan, Amar Gajjar, Maryam Fouladi, Alberto Broniscer, Frederick Boop, Chin-Shang Li and Robert J. Ogg

Object

Diffusion tensor (DT) imaging has been used to predict postoperative motor function in patients with supratentorial tumors. The authors sought to determine whether DT imaging and white matter tractography could detect axonal degeneration in patients with brainstem tumors.

Methods

A cross-sectional, retrospective study of 7 patients with brainstem tumors and 8 healthy volunteers was performed. The DT imaging data were normalized and regions of interest (ROIs) with the highest probability of sensory and motor connections were selected using the Talairach Atlas to identify the 3D millimetric coordinates of white matter tracts. An iterative process involving fractional anisotropy (FA), apparent diffusion coefficients (ADCs), and color maps was developed to precisely select ROIs in the bilateral sensory and motor tracts. The FA and ADC values were calculated for each ROI.

Results

The FA values of sensory and motor tracts significantly differed between the patient and healthy volunteer groups (p < 0.05), whereas no significant changes were found in the splenium or genu of the corpus callosum. The FA values were altered proximal and distal to the brainstem tumors with a bimodal peak of antegrade decreased FA involving second- and third-order sensory axons and retrograde decreased FA of motor axons.

Conclusions

This study demonstrates changes in diffusion properties of sensory and motor tracts consistent with degeneration to further characterize brainstem tumors in children, and the results warrant the planning of prospective trials. The rigorous methods the authors describe may provide valuable information when planning biopsies or debulking of unusual brainstem tumors, as well as improve prognostication of the possible functional tract recovery following therapy.