Marion Smits

Incorporating functional MR imaging into diffusion tensor tractography in the preoperative assessment of the corticospinal tract in patients with brain tumors

BACKGROUND AND PURPOSE: Our goal was to improve the preoperative assessment of the corticospinal tract (CST) in patients with brain tumors. We investigated whether the integration of functional MR imaging (fMRI) data and diffusion tensor (DT) tractography can be used to evaluate the spatial relationship between the hand and foot fibers of the CST and tumor borders. MATERIALS AND METHODS: We imaged 10 subjects: 1 healthy volunteer and 9 patients. Imaging consisted of a 3D T1-weighted sequence, a gradient-echo echo-planar imaging (EPI) sequence for fMRI, and a diffusion-weighted EPI sequence for DT tractography. DT tractography was initiated from a seed region of interest in the white matter area subjacent to the maximal fMRI activity in the precentral cortex. The target region of interest was placed in the cerebral peduncle. RESULTS: In the healthy volunteer, we successfully tracked hand, foot, and lip fibers bilaterally by using fMRI-based DT tractography. In all patients, we could track the hand fibers of the CST bilaterally. In 4 patients who also performed foot tapping, we could clearly distinguish hand and foot fibers. We were able to depict the displacement of hand and foot fibers by tumor and the course of fibers through areas of altered signal intensity. CONCLUSION: Incorporating fMRI into DT tractography in the preoperative assessment of patients with brain tumors may provide additional information on the course of important white matter tracts and their relationship to the tumor. Only this approach allows a distinction between the CST components, while visualization of the CST is improved when fiber tracking is hampered by tumor (infiltration) or perifocal edema.

Crossed Cerebrocerebellar Language Lateralization: An Additional Diagnostic Feature for Assessing Atypical Language Representation in Presurgical Functional MR Imaging

BACKGROUND AND PURPOSE: Determining language dominance with fMRI is challenging in patients with brain tumor, particularly in cases of suspected atypical language representation. Supratentorial activation patterns must be interpreted with great care when the tumor is in or near the presumed language areas, where tumor tissue or mass effect can lead to false-negative fMRI results. In this study, we assessed cerebrocerebellar language fMRI lateralization in healthy participants and in patients with brain tumors with a focus on atypical language representation. MATERIALS AND METHODS: Twenty healthy participants and 38 patients with a brain tumor underwent fMRI with a verb-generation task. Cerebral and cerebellar language lateralizations were separately classified as left-sided, right-sided, or symmetric. Electrocortical stimulation was performed in 19 patients. With the McNemar test, we evaluated the dependency between language lateralization in the cerebrum and cerebellum, and with Pearson correlation analysis, the relationship between the cerebral and cerebellar lateralization indices. RESULTS: There was a significant dependency between cerebral and cerebellar language activation, with moderate negative correlation (Pearson r = −0.69). Crossed cerebrocerebellar language activation was present in both healthy participants and patients, irrespective of handedness or typical or atypical language representation. There were no discordant findings between fMRI and electrocortical stimulation. CONCLUSIONS: Language lateralization in the cerebellum can be considered an additional diagnostic feature to determine language dominance in patients with brain tumor. This is particularly useful in cases of uncertainty, such as the interference of a brain tumor with cerebral language activation on fMRI and atypical language representation.

Language lateralisation after Melodic Intonation Therapy: an fMRI study in subacute and chronic aphasia

ABSTRACT Background: There is an ongoing debate whether the effect of Melodic Intonation Therapy (MIT) in patients with severe non-fluent aphasia depends on recruitment of right hemisphere (RH) structures for language functioning or on re-recruitment of left hemisphere (LH) language structures. So far, neuroimaging studies have produced conflicting evidence. Aims: To investigate whether a shift in language lateralisation occurs after intensive treatment in subacute (<3 months post onset) and chronic (>1 year post onset) stroke patients with aphasia. Method & Procedures: In a multiple case pilot study with pre-post-design 5 subacute and 4 chronic stroke patients received intensive MIT (6 weeks, 30 sessions). Pre- and post-treatment they underwent functional MRI scanning with a passive listening task to determine language lateralisation indices (LIs). Outcomes & Results: No consistent shift of language activation was found either to the LH or to the RH. With one exception, subacute patients showed symmetrical or right-lateralised language activation pretreatment, which tended to become more right lateralised after treatment. Language activation in chronic patients was left lateralised in two of the four participants, with a tendency towards stronger left lateralised activation after treatment. Conclusions: Data for the subacute patients provide some support for the classical notion that MIT promotes recruitment of RH structures for language processing. However, the contrasting activation patterns in chronic participants before as well as after treatment suggest that reorganisation of language after MIT occurs in interaction with a dynamic recovery process after stroke. Time post onset should be addressed systematically in studies of treatment-induced language recovery.

Qualitative agreement and diagnostic performance of arterial spin labelling MRI and FDG PET-CT in suspected early-stage dementia:Comparison of arterial spin labelling MRI and FDG PET-CT in suspected dementia

18FDG PET-CT is useful for early and differential diagnosis of dementia. ASL-MRI seems an attractive alternative. Visual agreement was calculated in 21 brain regions bilaterally in 9/11 patients with suspected early-stage dementia, excluding 2 patients due to ASL-MRI motion artefacts. Overall gross agreement was almost perfect and identical between and within modalities (κ=0.85-0.86, p<0.05). Intermodality regional agreement was variable, moderate (κ=0,56 in posterior cingulate) to perfect (including in precuneus), not different from intramodality agreement. Diagnostic accuracy was 5/9 (56%) for ASL-MRI and 7/9 (78%) for FDG PETCT. (p=0.31). Clinical experience and optimisation may further improve ASL-MRIs performance.