Abstract P3-08-01: Cognitive impairment and cortical network dysfunction following chemotherapy

A common complaint of cancer patients is the experience of cognitive difficulty during and after chemotherapy. However, the mechanisms through which this occurs are still unknown. We hypothesized that chemotherapy-induced cognitive impairment may result from dysfunction in large-scale brain networks, particularly those involved in attentional control. These networks are evident when measuring task-based brain activity during attention-demanding tasks, but can also be studied using resting state functional connectivity magnetic resonance imaging (rs-fcMRI). In rs-fcMRI, connectivity between brain regions is measured using data collected while participants lie awake in the magnet with their eyes open, but performing no task. It reliably distinguishes known sensory, motor, and executive networks based on connectivity patterns. These data complement information about structural (white matter) connectivity obtained using diffusion tensor imaging (DTI).

Here we report a case-control study of women with a history of triple negative breast cancer (BrCa) who completed standard adjuvant chemotherapy within two years of study entry. The cases (n = 15) were defined as women who reported cognitive impairment by the Cognitive Failures Questionnaire and controls (n = 13) were women who did not report cognitive impairment. All participants eligible for MRI investigation underwent rs-fcMRI and DTI on a Siemens 3T TIM Trio scanner. DTI parameters measured included Fractional Anisotropy (FA), Mean Diffusivity (MD), Radial Diffusivity (RD), and Axial Diffusivity.

The study was conducted in its entirety at Washington University in St. Louis School of Medicine. Institutional review board approval was obtained prior to recruitment. The mean age of cases was 53.1 years and controls 51.6 years; all were diagnosed with invasive ductal or lobular BrCa.

For each participant, we extracted the timecourse of brain activity for regions of interest in frontoparietal and cingularopercular control systems, measured indirectly via blood oxygenation level dependent (BOLD) contrast, from the MRI scans, and additional regions of interest distributed across the brain. We excluded scans that showed motion artifact. Pairwise connectivity was calculated using Pearson correlation between all regions of interest; we also used these regions in seed-based analyses. We compared the strength of rs-fcMRI-defined network connections between the two groups and used nonparametric permutation tests to calculate statistical significance.

We found significant changes within several regions of the frontoparietal attention network, such that patients reporting greater cognitive difficulty showed weaker neural connectivity. In addition, DTI analyses revealed different patterns of anatomical connectivity between groups, including reduced FA (p<0.03) and increased MD and RD (p<0.02), both of which have been shown to be signatures of brain change in demyelinating disease.

Together our results suggest that standard therapeutic levels of chemotherapy for BrCa patients may result in structural and functional connectivity alterations in the brain networks supporting executive attention, which in turn may be a contributing factor in cognitive difficulty.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-08-01.

Impact of therapeutic hypothermia on MRI diffusion changes in neonatal encephalopathy

OBJECTIVE

The objective of this work was to determine the impact of therapeutic hypothermia (TH) on the magnitude and time course of mean diffusivity (MD) changes following hypoxic-ischemic encephalopathy (HIE) in newborns.

METHODS

Cerebral MRI scans of infants undergoing whole body TH for HIE from 2007 to 2010 were retrospectively reviewed. The data were analyzed identically to a control group of newborns with HIE previously published, prior to the development of TH. Anatomic injury was defined on T1- and T2-weighted ("late") MRI obtained after the fifth day of life. Since MD values vary regionally, the ratios of MD values for injured and normal tissue were calculated for areas of injury. Normal values were obtained from corresponding brain regions of 12 infants undergoing TH who had no injury on MRI studies.

RESULTS

Twenty-three of 59 infants who underwent TH and MRI displayed cerebral injury on late MRI and were included in the study. MD ratios were decreased in all injured infants within the first 7 days of life. The return of MD to normal (pseudonormalization) occurred after the tenth day as compared to 6-8 days in the control group. Infants with severest injury demonstrated greater reduction in MD, but no difference in time to pseudonormalization.

CONCLUSION

TH slows the evolution of diffusion abnormalities on MRI following HIE in term infants.

Disability in optic neuritis correlates with diffusion tensor-derived directional diffusivities

OBJECTIVE

To determine the potential of directional diffusivities from diffusion tensor imaging (DTI) to predict clinical outcome of optic neuritis (ON), and correlate with vision, optical coherence tomography (OCT), and visual evoked potentials (VEP).

METHODS

Twelve cases of acute and isolated ON were imaged within 30 days of onset and followed prospectively. Twenty-eight subjects with a remote clinical history of ON were studied cross-sectionally. Twelve healthy controls were imaged for comparison. DTI data were acquired at 3T with a surface coil and 1.3 x 1.3 x 1.3 mm(3) isotropic voxels.

RESULTS

Normal DTI parameters (mean +/- SD, microm(2)/ms) were axial diffusivity = 1.66 +/- 0.18, radial diffusivity = 0.81 +/- 0.26, apparent diffusion coefficient (ADC) = 1.09 +/- 0.21, and fractional anisotropy (FA) = 0.43 +/- 0.15. Axial diffusivity decreased up to 2.5 SD in acute ON. The decrease in axial diffusivity at onset correlated with visual contrast sensitivity 1 month (r = 0.59) and 3 months later (r = 0.65). In three subjects followed from the acute through the remote stage, radial diffusivity subsequently increased to > 2.5 SD above normal, as did axial diffusivity and ADC. In remote ON, radial diffusivity correlated with OCT (r = 0.81), contrast sensitivity (r = 0.68), visual acuity (r = 0.56), and VEP (r = 0.54).

CONCLUSION

In acute and isolated demyelination, axial diffusivity merits further investigation as a predictor of future clinical outcome. Diffusion parameters are dynamic in acute and isolated optic neuritis, with an initial acute decrease in axial diffusivity. In remote disease, radial diffusivity correlates with functional, structural, and physiologic tests of vision.