2005 Proceedings - ASNR

Wednesday
MATERIALS & METHODS
Seven right-handed patients affected by drug resistant
Parkinson’s disease (Hoehn & Yahr score ≥ 3), were studied
with BOLD-based functional MR imaging (fMRI). Patients
underwent bilateral implantation of electrodes in the STN.
Daily therapy was not changed the day of fMRI, performed
6 days after surgical implantation and before connection to
subcutaneous pacemaker. Left electrode was used for STN
stimulation during fMRI in 4 cases, right electrode in 2 cases
and both electrodes in 1 case. In 2 cases motor task was performed
also with the hand ipsilateral to the activated electrode.
Finger tapping task was performed using the contralateral
hand. An external pacemaker set for therapeutic
effects without collateral problems was used, connected with
intracerebral electrode with a 10 mt wire. Functional MR
imaging was divided into 3 phases: 1) pacemaker on and off
(DBS-on/off) without voluntary movements; 2) left electrode
not active (DBS-off) with 6 periods of rest and selfpaced
right hand movements; 3) activation of left electrode
(DBS-on) with 6 periods of rest and self-paced movements.
Tasks were performed with a 1.5 T scanner (64 MHz; 25
mT/m), using EPI sequences extended from the base to the
vertex positioned parallel to the commissural line (transmit/receive
head coil). Statistical parametric mapping
(SPM99) implemented in MatLab 6 was used for statistical
analysis using Student’s t-test (correct p value = 0.05 and
uncorrect p value = 0.001/0.01) for false positive.
RESULTS
One patient interrupted fMRI exam and 1 patient was not
valuable for motion artifacts. Five patients completed all
tasks: 1) no side effect was observed during and after MR
imaging protocol; 2) with DBS on/off tasks activations distant
from the STN were observed, in the limbic cortex and in
frontal cortex (suppl. motor area BA 6); 3) comparison of
DBS-off/DBS-on data obtained during self-paced movements
showed reduction of activated cortical areas when performed
with DBS-on. This suggested a selection and focalization
of neural activity especially in primary motor cortex
(BA 3/4) induced by NST stimulation.
CONCLUSION
In this specific condition BOLD-based fMRI demonstrated
to be safe even with DBS electrodes in the STN. Our preliminary
experience in this small group of patients showed
that DBS should facilitate neural circuits through the SMA.
Moreover DBS should facilitate voluntary movements
reducing activations of associative corticies and focusing
neural activity in primary motor cortex.
KEY WORDS: Functional MR imaging, Parkinson’s disease,
deep brain stimulation
174
Paper 327 Starting at 4:04 PM, Ending at 4:12 PM
Assessment of Diffusion Characteristics for Motor
Pathway Fiber Tracks in Multiple Sclerosis Using
Diffusion Tensor Imaging
Borg, B. 1 · Phillips, M. D. 1 · Marrie, R. 1 · Stone, L. 1 ·
Bhattacharyya, P. 1 · Hirsch, J. 2 · Gass, A. 2 · Lowe, M. J. 1
1 2 Cleveland Clinic Foundation, Cleveland, OH, Basel
Universitaetspital, Basel, SWITZERLAND
PURPOSE
To test the diffusion characteristics of individual fiber tracts
in patients with multiple sclerosis (MS) using diffusion tensor
imaging (DTI).
MATERIALS & METHODS
Six patients with early stage MS (median EDSS = 3 ± 2) and
six age- and gender-matched control subjects were recruited
to participate in this study. All subjects participated in a scan
session using a Siemens Allegra 3 T MR scanner that included
a high-resolution T1-weighted anatomical scan, an fMRI
activation study acquired during the bilateral finger tapping
and a six direction whole-brain diffusion tensor imaging
study utilizing 2 mm isotropic voxels. Functional MR imaging
activation maps were used to produce seed regions in the
white matter near the bilateral supplementary motor area
(SMA). Diffusion tensor imaging data were processed using
a multistep procedure consisting of eddy-current correction,
motion correction, followed by production of diffusion tensor
eigenvalues. For each voxel, the eigenvalues are used to
produce volume ratio index (VRI), a measure of white matter
anisotropy. The calculated diffusion tensor is used to
track fibers in the white matter pathways using the method
of Mori, et al. Threshold values used to terminate a given
track were VRI < 0.05, and deflection angle > 80 o . These
parameters were observed to allow tracking to progress
through some MS lesions. Using SMA seed regions tracks
passing through the body of the corpus callosum were selected
for further analysis. Mean VRI, mean principal eigenvalue
(L1), and mean quadrature sum of nonprincipal eigenvalues
(L2) were calculated for each callosal track in each subject.
RESULTS
Mean VRI values demonstrated reduced anisotropy in MS
subjects (0.348 ± 0.047) in comparison to controls (0.424 ±
-0.03)( p < 0.07). Mean L2 values showed a corresponding
increase in patients with MS (0.783 x 10 -3 mm 2 /s ± 0.073) in
comparison to controls (0.664 x 10 x 10 -3 mm 2 /s ± 0.039) (p
< 0.07). In contrast, mean L1 values were unchanged
between MS subjects (1.348 x 10 -3 mm 2 /s ± 0.050) and controls
(1.362 x 10 -3 mm 2 /s ± 0.039) (p < 0.9). Findings suggest
that reported decrease in white matter anisotropy in multiple
sclerosis is largely due to an increase in the diffusivity of
water perpendicular to fiber track axons while diffusivity
parallel to the direction of axons is apparently unaffected by
MS.
CONCLUSION
Incorporating a novel fMRI-based selection of cortical seed
regions for the DTI-based fiber tracking of inhemispheric
motor pathways the present study demonstrates a reduction
in diffusivity perpendicular to fiber tracts with preservation
of diffusivity parallel to fiber tracts. Findings suggest that the