John Margetis OTD, OTR/L
Associate Professor of Clinical Occupational Therapy
John Margetis specializes in neurologic and critical care rehabilitation with clinical interests in vascular/acquired brain injury, stroke, neuroimaging and neurocognitive dysfunction. In addition to providing direct patient care, Dr. Margetis mentors fellow faculty members, doctoral residents and Levels I and II fieldwork students. During his doctoral residency he authored a position paper defining the role of occupational therapy in acute care settings, and has been an invited lecturer on congenital amputations at USC and Children’s Hospital Los Angeles.
Doctorate of Occupational Therapy (OTD)
2013 | University of Southern California
Master of Arts (MA)
in Occupational Therapy
2012 | University of Southern California
Bachelor of Science (BS)
in Occupational Therapy
2011 | University of Southern California
Bachelor of Arts (BA)
2011 | University of Southern California
Liew, S.-L., Schweighofer, N., Cole, J. H., Zavaliangos-Petropulu, A., Lo, B. P., Han, L. K. M., Hahn, T., Schmaal, L., Donnelly, M. R., Jeong, J. N., Wang, Z., Abdullah, A., Kim, J. H., Hutton, A. M., Barisano, G., Borich, M. R., Boyd, L. A., Brodtmann, A., Buetefisch, C. M., Byblow, W. D., Cassidy, J. M., Charalambous, C. C., Ciullo, V., Bastos Conforto, A., Dacosta-Aguayo, R., DiCarlo, J. A., Domin, M., Dula, A. N., Egorova-Brumley, N., Feng, W., Geranmayeh, F., Gregory, C. M., Hanlon, C. A., Hayward, K., Holguin, J. A., Hordacre, B., Jahanshad, N., Kautz, S. A., Khlif, M. S., Kim, H., Kuceyeski, A., Lin, D. J., Liu, J., Lotze, M., MacIntosh, B. J., Margetis, J. L., Mataro, M., Mohamed, F. B., Olafson, E. R., Park, G., Piras, F., Revill, K. P., Roberts, P., Robertson, A. D., Sanossian, N., Schambra, H. M., Seo, N. J., Soekadar, S. R., Spalletta, G., Stinear, C. M., Taga, M., Tang, W. K., Thielman, G. T., Vecchio, D., Ward, N. S., Westlye, L. T., Winstein, C. J., Wittenberg, G. F., Wolf, S. L., Wong, K. A., Yu, C., Cramer, S. C., & Thompson, P. M. (2023). Association of brain age, lesion volume, and functional outcome in patients with stroke. Neurology, 100(20), e2103-e2113. https://doi.org/10.1212/WNL.0000000000207219 Show abstract
Background and objectives. Functional outcomes after stroke are strongly related to focal injury measures. However, the role of global brain health is less clear. Here, we examined the impact of brain age, a measure of neurobiological aging derived from whole brain structural neuroimaging, on post-stroke outcomes, with a focus on sensorimotor performance. We hypothesized that more lesion damage would result in older brain age, which would in turn be associated with poorer outcomes. Related, we expected that brain age would mediate the relationship between lesion damage and outcomes. Finally, we hypothesized that structural brain resilience, which we define in the context of stroke as younger brain age given matched lesion damage, would differentiate people with good versus poor outcomes.
Methods. We conducted a cross-sectional observational study using a multi-site dataset of 3D brain structural MRIs and clinical measures from ENIGMA Stroke Recovery. Brain age was calculated from 77 neuroanatomical features using a ridge regression model trained and validated on 4,314 healthy controls. We performed a three-step mediation analysis with robust mixed-effects linear regression models to examine relationships between brain age, lesion damage, and stroke outcomes. We used propensity score matching and logistic regression to examine whether brain resilience predicts good versus poor outcomes in patients with matched lesion damage.
Results. We examined 963 patients across 38 cohorts. Greater lesion damage was associated with older brain age (β=0.21; 95% CI: 0.04, 0.38, P=0.015), which in turn was associated with poorer outcomes, both in the sensorimotor domain (β=-0.28; 95% CI: -0.41, -0.15, P<0.001) and across multiple domains of function (β=-0.14; 95% CI: -0.22, -0.06, P<0.001). Brain age mediated 15% of the impact of lesion damage on sensorimotor performance (95% CI: 3%, 58%, P=0.01). Greater brain resilience explained why people have better outcomes, given matched lesion damage (OR=1.04, 95% CI: 1.01, 1.08, P=0.004).
Conclusions. We provide evidence that younger brain age is associated with superior post-stroke outcomes and modifies the impact of focal damage. The inclusion of imaging-based assessments of brain age and brain resilience may improve the prediction of post-stroke outcomes compared to focal injury measures alone, opening new possibilities for potential therapeutic targets.
Harding, P., Holguin, J., & Margetis, J. L. (2022, November 1). Enhancing client and caregiver training: Content and process considerations for supplemental multimedia education. SIS Quarterly Practice Connections, 7(4). Full text
Holguin, J. A., Margetis, J. L., Narayan, A., Yoneoka, G. M., & Irimia, A. (2022). Vascular cognitive impairment after mild stroke: Connectomic insights, neuroimaging, and knowledge translation. Frontiers in Neuroscience, 16, 905979. https://doi.org/10.3389/fnins.2022.905979 Show abstract
Contemporary stroke assessment protocols have a limited ability to detect vascular cognitive impairment (VCI), especially among those with subtle deficits. This lesser-involved categorization, termed mild stroke (MiS), can manifest compromised processing speed that negatively impacts cognition. From a neurorehabilitation perspective, research spanning neuroimaging, neuroinformatics, and cognitive neuroscience supports that processing speed is a valuable proxy for complex neurocognitive operations, insofar as inefficient neural network computation significantly affects daily task performance. This impact is particularly evident when high cognitive loads compromise network efficiency by challenging task speed, complexity, and duration. Screening for VCI using processing speed metrics can be more sensitive and specific. Further, they can inform rehabilitation approaches that enhance patient recovery, clarify the construct of MiS, support clinician-researcher symbiosis, and further clarify the occupational therapy role in targeting functional cognition. To this end, we review relationships between insult-derived connectome alterations and VCI, and discuss novel clinical approaches for identifying disruptions of neural networks and white matter connectivity. Furthermore, we will frame knowledge translation efforts to leverage insights from cutting-edge structural and functional connectomics research. Lastly, we highlight how occupational therapists can provide expertise as knowledge brokers acting within their established scope of practice to drive substantive clinical innovation.
Zavaliangos-Petropulu, A., Lo, B., Donnelly, M. R., Schweighofer, N., Lohse, K., Jahanshad, N., Barisano, G., Banaj, N., Borich, M. R., Boyd, L. A., Buetefisch, C. M., Byblow, W. D., Cassidy, J. M., Charalambous, C. C., Conforto, A. B., DiCarlo, J. A., Dula, A. N., Egorova-Brumley, N., Etherton, M. R., Feng, W., Fercho, K. A., Geranmayeh, F., Hanlon, C. A., Hayward, K. S., Hordacre, B., Kautz, S. A., Khlif, M. S., Kim, H., Kuceyeski, A., Lin, D. J., Liu, J., Lotze, M., MacIntosh, B. J., Margetis, J. L., Mohamed, F. B., Piras, F., Ramos-Murguialday, A., Revill, K. P., Roberts, P. S., Robertson, A. D., Schambra, H. M., Seo, N. J., Shiroishi, M. S., Stinear, C. M., Soekadar, S. R., Spalletta, G., Taga, M., Tang, W. K., Thielman, G. T., Vecchio, D., Ward, N. S., Westlye, L. T., Werden, E., Winstein, C., Wittenberg, G. F., Wolf, S. L., Wong, K. A., Yu, C., Brodtmann, A., Cramer, S. C., Thompson, P. M., & Liew, S.-L. (2022). Chronic stroke sensorimotor impairment is related to smaller hippocampal volumes: An ENIGMA analysis. Journal of the American Heart Association, 11(10), e025109. https://doi.org/10.1161/JAHA.121.025109 Show abstract
Background. Persistent sensorimotor impairments after stroke can negatively impact quality of life. The hippocampus is vulnerable to poststroke secondary degeneration and is involved in sensorimotor behavior but has not been widely studied within the context of poststroke upper-limb sensorimotor impairment. We investigated associations between non-lesioned hippocampal volume and upper limb sensorimotor impairment in people with chronic stroke, hypothesizing that smaller ipsilesional hippocampal volumes would be associated with greater sensorimotor impairment.
Methods and Results. Cross-sectional T1-weighted magnetic resonance images of the brain were pooled from 357 participants with chronic stroke from 18 research cohorts of the ENIGMA (Enhancing NeuoImaging Genetics through Meta-Analysis) Stroke Recovery Working Group. Sensorimotor impairment was estimated from the FMA-UE (Fugl-Meyer Assessment of Upper Extremity). Robust mixed-effects linear models were used to test associations between poststroke sensorimotor impairment and hippocampal volumes (ipsilesional and contralesional separately; Bonferroni-corrected, P<0.025), controlling for age, sex, lesion volume, and lesioned hemisphere. In exploratory analyses, we tested for a sensorimotor impairment and sex interaction and relationships between lesion volume, sensorimotor damage, and hippocampal volume. Greater sensorimotor impairment was significantly associated with ipsilesional (P=0.005; β=0.16) but not contralesional (P=0.96; β=0.003) hippocampal volume, independent of lesion volume and other covariates (P=0.001; β=0.26). Women showed progressively worsening sensorimotor impairment with smaller ipsilesional (P=0.008; β=−0.26) and contralesional (P=0.006; β=−0.27) hippocampal volumes compared with men. Hippocampal volume was associated with lesion size (P<0.001; β=−0.21) and extent of sensorimotor damage (P=0.003; β=−0.15).
Conclusions. The present study identifies novel associations between chronic poststroke sensorimotor impairment and ipsilesional hippocampal volume that are not caused by lesion size and may be stronger in women.
Liew, S., Zavaliangos‐Petropulu, A., Jahanshad, N., Lang, C. E., Hayward, K. S., Lohse, K. R., Juliano, J. M., Assogna, F., Baugh, L. A., Bhattacharya, A. K., Bigjahan, B., Borich, M. R., Boyd, L. A., Brodtmann, A., Buetefisch, C. M., Byblow, W. D., Cassidy, J. M., Conforto, A. B., Craddock, R. C., Dimyan, M. A., Dula, A. N., Ermer, E., Etherton, M. R., Fercho, K. A., Gregory, C. M., Hadidchi, S., Holguin, J. A., Hwang, D. H., Jung, S., Kautz, S. A., Khlif, M. S., Khoshab, N., Kim, B., Kim, H., Kuceyeski, A., Lotze, M., MacIntosh, B. J., Margetis, J. L., Mohamed, F. B., Piras, F., Ramos‐Murguialday, A., Richard, G., Roberts, P., Robertson, A. D., Rondina, J. M., Rost, N. S., Sanossian, N., Schweighofer, N., Seo, N. J., Shiroishi, M. S., Soekadar, S. R., Spalletta, G., Stinear, C. M., Suri, A., Tang, W. K. W., Thielman, G. T., Vecchio, D., Villringer, A., Ward, N. S., Werden, E., Westlye, L. T., Winstein, C., Wittenberg, G. F., Wong, K. A., Yu, C., Cramer, S. C., & Thompson, P. M. (2022). The ENIGMA Stroke Recovery Working Group: Big data neuroimaging to study brain–behavior relationships after stroke. Human Brain Mapping, 43(1), 129-148. https://doi.org/10.1002/hbm.25015 Show abstract
The goal of the Enhancing Neuroimaging Genetics through Meta‐Analysis (ENIGMA) Stroke Recovery working group is to understand brain and behavior relationships using well‐powered meta‐ and mega‐analytic approaches. ENIGMA Stroke Recovery has data from over 2,100 stroke patients collected across 39 research studies and 10 countries around the world, comprising the largest multisite retrospective stroke data collaboration to date. This article outlines the efforts taken by the ENIGMA Stroke Recovery working group to develop neuroinformatics protocols and methods to manage multisite stroke brain magnetic resonance imaging, behavioral and demographics data. Specifically, the processes for scalable data intake and preprocessing, multisite data harmonization, and large‐scale stroke lesion analysis are described, and challenges unique to this type of big data collaboration in stroke research are discussed. Finally, future directions and limitations, as well as recommendations for improved data harmonization through prospective data collection and data management, are provided.
Liew, S.-L., Zavaliangos-Petropulu, A., Schweighofer, N., Jahanshad, N., Lang, C. E., Lohse, K. R., Banaj, N., Barisano, G., Baugh, L. A., Bhattacharya, A. K., Bigjahan, B., Borich, M. R., Boyd, L. A., Brodtmann, A., Buetefisch, C. M., Byblow, W. D., Cassidy, J. M., Charalambous, C. C., Ciullo, V., Conforto, A. B., Craddock, R. C., Dula, A. N., Egorova, N., Feng, W., Fercho, K. A., Gregory, C. M., Hanlon, C. A., Hayward, K. S., Holguin, J. A., Hordacre, B., Hwang, D. H., Kautz, S. A., Salah Khlif, M., Kim, B., Kim, H., Kuceyeski, A., Lo, B., Liu, J., Lin, D., Lotze, M., MacIntosh, B. J., Margetis, J. L., Mohamed, F. B., Nordvik, J. E., Petoe, M. A., Piras, F., Raju, S., Ramos-Murguialday, A., Revill, K. P., Roberts, P., Robertson, A. D., Schambra, H. M., Seo, N. J., Shiroishi, M. S., Soekadar, S. R., Spalletta, G., Stinear, C. M., Suri, A., Tang, W. K., Thielman, G. T., Thijs, V. N., Vecchio, D., Ward, N. S., Westlye, L. T., Winstein, C. J., Wittenberg, G. F., Wong, K. A., Yu, C., Wolf, S. L., Cramer, S. C., Thompson, P. M., & ENIGMA Stroke Recovery Working Group. (2021). Smaller spared subcortical nuclei are associated with worse post-stroke sensorimotor outcomes in 28 cohorts worldwide. Brain Communications, 3(4), fcab254. https://doi.org/10.1093/braincomms/fcab254 Show abstract
Up to two-thirds of stroke survivors experience persistent sensorimotor impairments. Recovery relies on the integrity of spared brain areas to compensate for damaged tissue. Deep grey matter structures play a critical role in the control and regulation of sensorimotor circuits. The goal of this work is to identify associations between volumes of spared subcortical nuclei and sensorimotor behaviour at different timepoints after stroke. We pooled high-resolution T1-weighted MRI brain scans and behavioural data in 828 individuals with unilateral stroke from 28 cohorts worldwide. Cross-sectional analyses using linear mixed-effects models related post-stroke sensorimotor behaviour to non-lesioned subcortical volumes (Bonferroni-corrected, P < 0.004). We tested subacute (≤90 days) and chronic (≥180 days) stroke subgroups separately, with exploratory analyses in early stroke (≤21 days) and across all time. Sub-analyses in chronic stroke were also performed based on class of sensorimotor deficits (impairment, activity limitations) and side of lesioned hemisphere. Worse sensorimotor behaviour was associated with a smaller ipsilesional thalamic volume in both early (n = 179; d = 0.68) and subacute (n = 274, d = 0.46) stroke. In chronic stroke (n = 404), worse sensorimotor behaviour was associated with smaller ipsilesional putamen (d = 0.52) and nucleus accumbens (d = 0.39) volumes, and a larger ipsilesional lateral ventricle (d = −0.42). Worse chronic sensorimotor impairment specifically (measured by the Fugl-Meyer Assessment; n = 256) was associated with smaller ipsilesional putamen (d = 0.72) and larger lateral ventricle (d = −0.41) volumes, while several measures of activity limitations (n = 116) showed no significant relationships. In the full cohort across all time (n = 828), sensorimotor behaviour was associated with the volumes of the ipsilesional nucleus accumbens (d = 0.23), putamen (d = 0.33), thalamus (d = 0.33) and lateral ventricle (d = −0.23). We demonstrate significant relationships between post-stroke sensorimotor behaviour and reduced volumes of deep grey matter structures that were spared by stroke, which differ by time and class of sensorimotor measure. These findings provide additional insight into how different cortico-thalamo-striatal circuits support post-stroke sensorimotor outcomes.
Wilcox, J., Peterson, K. S., Lewis, C. M., & Margetis, J. L. (2021). Occupational therapy during COVID-19–related critical illness: A case report. American Journal of Occupational Therapy, 75( Suppl. 1), 7511210010. https://doi.org/10.5014/ajot.2021.049196 Show abstract
The coronavirus disease 2019 (COVID-19) pandemic has presented unique challenges for occupational therapy practitioners working in acute and critical care settings. Using the best available evidence, this case report overviews a prototypical COVID-19 disease course and discusses key aspects of clinical reasoning for practitioners working with this novel population. Following a single patient admitted to a tertiary academic medical center, the authors review the occupational profile and medical history, common impairments, the intervention plan, and strategies to align the occupational therapy and medical goals of care.
Margetis, J. L., Wilcox, J., Thompson, C., & Mannion, N. (2021). Occupational therapy: Essential to critical care rehabilitation. American Journal of Occupational Therapy, 75, 7502170010. https://doi.org/10.5014/ajot.2021.048827 Show abstract
The coronavirus disease 2019 (COVID-19) pandemic reshaped the health care landscape, leading to the reassignment of essential health care workers to critical areas and widespread furloughs of providers deemed nonessential, including occupational therapy practitioners. Although multidisciplinary critical care teams often include occupational therapy practitioners, efforts to define, measure, and disseminate occupational therapy’s unique contributions to critical care outcomes have been overlooked. This editorial provides recommendations to improve the occupational therapy profession’s readiness to meet society’s current and future pandemic needs. We propose a three-pronged strategy to strengthen occupational therapy clinical practice, education, and advocacy to illuminate the distinct value of occupational therapy in critical care.
O'Leary, L., Margetis, J., Mills, E., & Velasco, P. (2018, June 22). Mind the gap: Navigating the transition from pediatric to adult health care [Radio segment]. Marketplace Weekend. Los Angeles, CA: American Public Media. Full text
Kuo, G., Cen, S., Zheng, L., Vazquez, A., Margetis, J., Holguin, J., Trummer, K., Emanuel, B., Kim-Tenser, M., & Bulic, S. (2018). Is the slope of optic nerve sheath diameter change in malignant middle cerebral artery stroke associated with mortality outcomes? Neurology, 90(15 Supplement), S40.006. Full text Show abstract
Objective. To investigate the association between optic nerve sheath diameter (ONSD) in malignant middle cerebral artery (MCA) strokes, progression to decompressive craniectomy and mortality outcomes.
Background. Malignant middle cerebral artery (MCA) stroke is a life-threatening condition with reported mortality of 80%, due to space-occupying cerebral edema and increased compartmental intracranial pressure (ICP). In current practice, decompressive craniectomy is known to improve mortality and functional outcomes. However, patient selection for surgical intervention can be difficult at times. Use of non-invasive surrogates for ICP could be valuable in managing malignant MCA syndromes. One possibility is through ONSD measurements, which has been shown to correlate to elevated intracranial pressures (ICPs) in studies across adult and pediatric patients. Currently, its utility in MCA syndromes has yet to be defined.
Design/Methods. 136 CT scans (1–6 per subject) from charts of 62 patients in a tertiary academic center were reviewed using previously published methodology. The outcomes of malignant MCA strokes were examined by utilizing mixed effects models to evaluate daily rate of change in optic parameters between deceased and non-deceased groups, craniotomy and non-craniotomy groups.
Results. Daily rate of change in optic parameters were significantly greater in deceased patients than non-deceased patients (0.16 vs −0.001μm/day, p=0.056 for ipsilateral optic nerve sheath (ONS); 0.32 vs −0.001 μm/day, p<0.0001 for contralateral ONS; 0.24 vs −0.0001 μm/day, p=0.0007 for averaged ONS, respectively). Daily rate of change in optic parameters did not differ significantly between craniectomy and non-craniectomy groups (0.036 vs 0.045μm/day, p=0.88 for ipsilateral ONS; 0.02 vs 0.07 μm/day, p=0.34 for contralateral ONS; 0.03 vs 0.06 μm/day, p=0.60 for average ONS, respectively).
Conclusions. A greater rate of change in ONSD is associated with greater mortality. Curiously, the rate of change of ONSD was not significantly affected by surgical intervention, possibly indicating that ONSD is indicative of cerebral edema and not necessarily ICP.
Liew, S.-L., Sheng, T., Margetis, J. L., & Aziz-Zadeh, L. S. (2013). Both novelty and expertise increase action observation network activity. Frontiers in Human Neuroscience, 7, 541. https://doi.org/10.3389/fnhum.2013.00541 Show abstract
Our experiences with others affect how we perceive their actions. In particular, activity in bilateral premotor and parietal cortices during action observation, collectively known as the action observation network (AON), is modulated by one's expertise with the observed actions or individuals. However, conflicting reports suggest that AON activity is greatest both for familiar and unfamiliar actions. The current study examines the effects of different types and amounts of experience (e.g., visual, interpersonal, personal) on AON activation. fMRI was used to scan 16 healthy participants without prior experience with individuals with amputations (novices), 11 experienced occupational therapists (OTs) who had varying amounts of experience with individuals with amputations, and one individual born with below-elbow residual limbs (participant CJ), as they viewed video clips of goal-matched actions performed by an individual with residual limbs and by an individual with hands. Participants were given increased visual exposure to actions performed by both effectors midway through the scanning procedure. Novices demonstrated a large AON response to the initial viewing of an individual with residual limbs compared to one with hands, but this signal was attenuated after they received visual exposure to both effectors. In contrast, OTs, who had moderate familiarity with residual limbs, demonstrated a lower AON response upon initial viewing-similar to novices after they received visual exposure. At the other extreme, CJ, who has extreme familiarity with residual limbs both visually and motorically, shows a largely increased left-lateralized AON response, exceeding that of novices and experienced OTs, when viewing the residual limb compared to hand actions. These results suggest that a nuanced model of AON engagement is needed to explain how cases of both extreme experience (CJ) and extreme novelty (novices) can result in the greatest AON activity.
September 28, 2021
A patient of Dr. John Margetis reflects on her GBS diagnosis
August 20, 2020
Associate Clinical Professor Jamie Wilcox USC Chan clinical faculty members Jamie Wilcox MA ’13, OTD ’14 and John Margetis ’11, MA ’12, OTD ’13 shared insights and expertise gained from working with COVID-positive patients at Keck Hospital of USC during an Aug. 19 webinar hosted by the…
May 5, 2016
Physical drawbacks don’t hamper the life of a USC faculty member who was adopted as an infant
October 22, 2013
85 Trojan alumni and faculty will be presenting at the 2013 Conference of the Occupational Therapy Association of California, Oct. 24-27 at the Sacramento (Calif.) Convention Center. On the evening of Friday Oct. 25, be sure to join your USC Trojan Family at the conference's alumni cocktail mixer.…
April 29, 2013
The USC Division of Occupational Science and Occupational Therapy officially announced its entry into the Campaign for the University of Southern California on Apr. 27 before a capacity crowd of over 400 Trojans gathered at the Hilton San Diego Bayfront hotel ballroom. The kickoff celebration,…
April 23, 2013
128 USC alumni, faculty, and students are scheduled to present at the 2013 Conference of the American Occupational Therapy Association, April 25-28 at the San Diego Convention Center. Presentation formats include a pre-conference institute, workshops, short courses, research and professional posters…
May 16, 2011
Read Class of 2011 graduate John Margetis’ story.
Hydrocephalus Association | November 30, 2021
Assoc. Clinical Prof. John Margetis features in this preview of a video webinar hosted by the Hydrocephalus Association.
AOTA's Everyday Evidence Podcast | July 19, 2021
What have two frontline OT practitioners learned during the COVID-19 pandemic? In the first episode of our three-part “COVID-19 Case Applications” series, Jamie Wilcox, OTD, OTR/L, and John Margetis, OTD, OTR/L, share their experiences as occupational therapists in a critical care setting during the pandemic. This series of #AOTApodcast episodes will focus on the COVID-19 case applications published in the American Journal of Occupational Therapy.
Mike McNulty, in
USC News | April 29, 2013
The USC Division of Occupational Science and Occupational Therapy officially announced its entry into The Campaign for the University of Southern California on April 27 before a capacity crowd of more than 400 Trojans at the Hilton San Diego Bayfront ballroom.