Mahta Karimpoor

All Publications

• Microstructural Alterations in Tract Development in College Football and Volleyball Players: A Longitudinal Diffusion MRI Study. Neurology Goubran, M., Mills, B. D., Georgiadis, M., Karimpoor, M., Mouchawar, N., Sami, S., Dennis, E. L., Akers, C., Mitchell, L., Boldt, B., Douglas, D., DiGiacomo, P. S., Rosenberg, J., Grant, G., Wintermark, M., Camarillo, D. B., Zeineh, M. 2023

  Abstract

  BACKGROUND AND OBJECTIVES: Repeated impacts in high-contact sports like American football can affect the brain's microstructure, which can be studied using diffusion MRI. Most imaging studies are cross-sectional, do not include low-contact players as controls, or lack advanced tract-specific microstructural metrics. We aimed to investigate longitudinal changes in high-contact collegiate athletes compared to low-contact controls using advanced diffusion MRI and automated fiber quantification.METHODS: We examined brain microstructure in high-contact (football) and low-contact (volleyball) collegiate athletes with up to 4 years of follow-up. Inclusion criteria included university and team enrollment. Exclusion criteria included history of neurosurgery, severe brain injury, major neurologic or substance abuse disorder. We investigated diffusion metrics along the length of tracts using nested linear mixed-effects models to ascertain the acute and chronic effects of sub-concussive and concussive impacts, and associations between diffusion changes with clinical, behavioral, and sports-related measures.RESULTS: Forty-nine football and twenty-four volleyball players (271 total scans) were included. Football players had significantly divergent trajectories in multiple microstructural metrics and tracts. Longitudinal increases in fractional anisotropy and axonal water fraction, and decreases in radial/mean diffusivity and orientation dispersion index, were present in volleyball but absent in football players (all findings |T-statistic|> 3.5, p-value < .0001). This pattern was present in the callosum forceps minor, superior longitudinal fasciculus, thalamic radiation, and cingulum hippocampus. Longitudinal differences were more prominent and observed in more tracts in concussed football players (n=24, |T|> 3.6, p < .0001). An analysis of immediate-post concussion scans (n=12) demonstrated a transient localized increase in axial diffusivity, mean/radial kurtosis in the uncinate and cingulum hippocampus (|T| > 3.7, p < .0001). Finally, within football players, those with high position-based impact risk demonstrated increased intra-cellular volume fraction longitudinally (T = 3.6, p < .0001).DISCUSSION: The observed longitudinal changes seen in football, and especially concussed athletes, could reveal diminished myelination, altered axonal calibers, or depressed pruning processes leading to a static, non-decreasing axonal dispersion. This prospective longitudinal study demonstrates divergent tract-specific trajectories of brain microstructure, possibly reflecting a concussive and repeated sub-concussive impact-related alteration of white matter development in football athletes.

  View details for DOI 10.1212/WNL.0000000000207543

  View details for PubMedID 37479529

• Longitudinal alterations of cerebral blood flow in high-contact sports. Annals of neurology Karimpoor, M., Georgiadis, M., Zhao, M. Y., Goubran, M., Moein Taghavi, H., Mills, B. D., Tran, D., Mouchawar, N., Sami, S., Wintermark, M., Grant, G., Camarillo, D. B., Moseley, M. E., Zaharchuk, G., Zeineh, M. M. 2023

  Abstract

  Repetitive head trauma is common in high-contact sports. Cerebral blood flow (CBF) can measure changes in brain perfusion that could indicate injury. Longitudinal studies with a control group are necessary to account for interindividual and developmental effects. We investigated whether exposure to head impacts causes longitudinal CBF changes.We prospectively studied 63 American football (high-contact cohort) and 34 volleyball (low-contact controls) male collegiate athletes, tracking CBF using 3D-pseudo-continuous arterial-spin-labeling (ASL) MRI for up to four years. Regional relative CBF (rCBF, normalized to cerebellar CBF) was computed after co-registering to T1-weighted images. A linear-mixed-effects model assessed the relationship of rCBF to sport, time, and their interaction. Within football players, we modeled rCBF against position-based head impact risk and baseline SCAT (Standardized Concussion Assessment Tool) score. Additionally, we evaluated early (1-5 days) and delayed (3-6 months) post-concussion rCBF changes (in-study concussion).Supratentorial gray matter rCBF declined in football compared to volleyball (sport-time interaction p=0.012), with a strong effect in the parietal lobe (p=0.002). Football players with higher position-based impact-risk had lower occipital rCBF over time (interaction p=0.005), while players with lower baseline SCAT score (worse performance) had relatively decreased rCBF in the cingulate-insula over time (interaction effect: p=0.007). Both cohorts showed a left-right rCBF asymmetry that decreased over time. Football players with an in-study concussion exhibited an early increase in occipital lobe rCBF (p=0.0166).These results suggest head impacts may result in an early increase in rCBF, but cumulatively a long-term decrease in rCBF. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/ana.26718

  View details for PubMedID 37306544

• Neuroradiologic Evaluation of MRI in High-Contact Sports. Frontiers in neurology McAllister, D., Akers, C., Boldt, B., Mitchell, L. A., Tranvinh, E., Douglas, D., Goubran, M., Rosenberg, J., Georgiadis, M., Karimpoor, M., DiGiacomo, P., Mouchawar, N., Grant, G., Camarillo, D., Wintermark, M., Zeineh, M. M. 2021; 12: 701948

  Abstract

  Background and Purpose: Athletes participating in high-contact sports experience repeated head trauma. Anatomical findings, such as a cavum septum pellucidum, prominent CSF spaces, and hippocampal volume reductions, have been observed in cases of mild traumatic brain injury. The extent to which these neuroanatomical findings are associated with high-contact sports is unknown. The purpose of this study was to determine whether there are subtle neuroanatomic differences between athletes participating in high-contact sports compared to low-contact athletic controls. Materials and Methods: We performed longitudinal structural brain MRI scans in 63 football (high-contact) and 34 volleyball (low-contact control) male collegiate athletes with up to 4 years of follow-up, evaluating a total of 315 MRI scans. Board-certified neuroradiologists performed semi-quantitative visual analysis of neuroanatomic findings, including: cavum septum pellucidum type and size, extent of perivascular spaces, prominence of CSF spaces, white matter hyperintensities, arterial spin labeling perfusion asymmetries, fractional anisotropy holes, and hippocampal size. Results: At baseline, cavum septum pellucidum length was greater in football compared to volleyball controls (p = 0.02). All other comparisons were statistically equivalent after multiple comparison correction. Within football at baseline, the following trends that did not survive multiple comparison correction were observed: more years of prior football exposure exhibited a trend toward more perivascular spaces (p = 0.03 uncorrected), and lower baseline Standardized Concussion Assessment Tool scores toward more perivascular spaces (p = 0.02 uncorrected) and a smaller right hippocampal size (p = 0.02 uncorrected). Conclusion: Head impacts in high-contact sport (football) athletes may be associated with increased cavum septum pellucidum length compared to low-contact sport (volleyball) athletic controls. Other investigated neuroradiology metrics were generally equivalent between sports.

  View details for DOI 10.3389/fneur.2021.701948

  View details for PubMedID 34456852

  View details for PubMedCentralID PMC8385770

• Neuroradiologic Evaluation of MRI in High-Contact Sports FRONTIERS IN NEUROLOGY McAllister, D., Akers, C., Boldt, B., Mitchell, L. A., Tranvinh, E., Douglas, D., Goubran, M., Rosenberg, J., Georgiadis, M., Karimpoor, M., DiGiacomo, P., Mouchawar, N., Grant, G., Camarillo, D., Wintermark, M., Zeineh, M. M. 2021; 12

  View details for DOI 10.3389/fneur.2021.701948

  View details for Web of Science ID 000685118200006