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Changes in the middle cerebral artery (MCA) spectrum during contrast-transcranial Doppler (c-TCD) demonstrating the effectiveness of performed Valsalva maneuver. During the strain phase of the maneuver, MCA flow velocity decreases of about 50% compared to baseline evaluation. After realising the maneuver, some microembolic signals (MES) appear suggesting; in this case, a mild paradoxical shunt
