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Ultrasound Med Biol. 2020 Jan 27. pii: S0301-5629(19)31639-4. doi: 10.1016/j.ultrasmedbio.2019.12.019. [Epub ahead of print]

Time-Resolved Response of Cerebral Stiffness to Hypercapnia in Humans.

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Institute of Medical Informatics, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Department of Mathematics, Technical University Berlin, Berlin, Germany.
Berlin Center for Advanced Neuroimaging (BCAN), Berlin, Germany.
Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany. Electronic address:


Cerebral blood flow, cerebral stiffness (CS) and intracranial pressure are tightly linked variables of cerebrovascular reactivity and cerebral autoregulation. Transtemporal ultrasound time-harmonic elastography was used for rapid measurement of CS changes in 10 volunteers before, during and after administration of a gas mixture of 95% O2 and 5% CO2 (carbogen). Within the first 2.2 ± 2.0 min of carbogen breathing, shear wave speed determined as a surrogate parameter of CS increased from 1.57 ± 0.04 to 1.66 ± 0.05 m/s (p < 0.01) in synchrony with end-tidal CO2 while post-hypercapnic CS recovery was delayed by 2.7 ± 1.4 min in relation to end-tidal CO2. Our results indicate that CS is highly sensitive to changes in CO2 levels of inhaled air. Possible mechanisms underlying the observed CS changes might be associated with cerebrovascular reactivity, cerebral blood flow adaptation and intracranial regulation, all of which are potentially relevant for future diagnostic applications of transtemporal time-harmonic elastography in a wide spectrum of neurologic diseases.


Brain stiffness; Hypercapnia; Intracranial pressure; Time-harmonic elastography; Transtemporal ultrasound; Vasodilatation

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Conflict of interest disclosure The authors have no conflicts of interest to disclose

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