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Using FLAIR MRI to Account for Hypoperfusion in Examinations of Brain-Behavior Relationships in Acute Stroke
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Poster C54 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Also presenting in Lightning Talks C, Wednesday, October 25, 10:00 - 10:15 am CEST, Auditorium
Lisa D. Bunker1, Argye E. Hillis1,2,3; 1Johns Hopkins University School of Medicine, Dept. of Neurology, 2Johns Hopkins University School of Medicine, Dept. of Physical Medicine & Rehabilitation, 3Johns Hopkins University School of Medicine, Dept. of Cognitive Science
Investigations of neuroanatomical structures associated with behavior are often conducted during chronic stages of stroke recovery. However, findings in this population may be influenced by functional reorganization and thus not reflect typical neurological function/organization. Ideally, investigations would be completed during the acute phase of recovery, before reorganization has occurred. Investigations in acute ischemic stroke present some unique challenges, though, such as needing to account for dysfunction associated with hypoperfusion in addition to the lesion. Currently, magnetic resonance perfusion weighted imaging (PWI) or CT perfusion are the gold standard for identifying hypoperfusion, but are not always available or may be contraindicated for some participants. Recently, Reyes and colleagues (2022) proposed an alternative method for quantifying hypoperfusion using hyperintense vessels—which reflect reduced blood flow—on fluid-attenuated inversion recovery (FLAIR) MRI (viz. the NIH-FHV score). This study examined the relationship between the locations of hypoperfusion on FLAIR compared to perfusion-weighted imaging (PWI; Bunker & Hillis, 2023). FLAIR and PWI scans for 101 individuals (48 female; median[range] age = 73[58-83]) with hyperacute ischemic stroke (i.e., prior to tissue-type plasminogen activator [tPA]) were scored for presence/absence of FLAIR hyperintense vessels (FHVs, the markers used to determine the NIH-FHV score) and hypoperfusion on PWI (time-to-peak >4sec) in six vascular regions: the anterior and posterior cerebral artery territories (ACA, PCA), and four sub-regions of the middle cerebral artery (MCA) territory including frontal, temporal, parietal, and insular. We examined associations between presence/absence of hypoperfusion on FLAIR/PWI using Pearson’s chi-square and Cramér’s V. There were significant associations (p’s ≤.001 after correction) in the location of hypoperfusion/hyperintense vessels in all vascular areas except for the ACA territory, presumably due to low power (only n=3 with FHVs and n=5 with PWI deficits in this region). Cramér’s V indicated that the associations were “strong” (ACA) and “very strong” (all other regions). Results replicate prior work establishing an association between the location of FHVs and perfusion deficits on PWI (Bunker et al., 2022). Likewise, these results validate prior investigations showing associations between various neurological and behavioral measures (e.g., NIHSS, naming, picture description, and neglect) and NIH-FHV scores in specific vascular regions independent of lesion volume (Bunker et al., 2022, Stein et al., 2022). Together, the current/previous studies provide validity that regions of hypoperfusion identified using the NIH-FHV score do indeed correspond with the location of perfusion deficits on PWI as well as various outcome measures. Since PWI may not always be collected with an MRI stroke protocol, whereas FLAIR is nearly always collected, the NIH-FHV score is an attractive alternative for quantifying the amount/location of hypoperfusion when PWI is not available. The NIH-FHV score has clinical utility in acute stroke care but also could be a useful tool for investigating brain-behavior relationships in acute stroke populations to account for dysfunction associated with hypoperfusion. We intend to present this work in conjunction with a tutorial of the background and methods of the NIH-FHV score (to support implementation), as well as our collective evidence supporting its application in clinical and research settings.
Topic Areas: Disorders: Acquired, Methods