Background: The time to maximum of the residue function (TMax) has been employed
to identify the penumbra in acute ischemic stroke. Cognitive impairment in patients with Carotid
Artery Stenosis (CAS) has been attributed to chronic cerebral hypoperfusion. The study aimed to
examine whether cognitive impairment can be detected based on a preliminary TMax cutoff in patients
with unilateral CAS.
Methods: Fifty unilateral CAS patients underwent dynamic susceptibility contrast MR perfusion.
The preliminary TMax cutoff (3 seconds) was derived on the basis of the upper limit of 95% confidence
interval of TMax in the Middle Cerebral Artery (MCA) contralateral to the CAS side. All
patients were allocated to the Right-delayed group (n=18), Left-delayed group (n=12), and Nondelayed
group (n=20) by the cutoff. Cognitive assessment was also administered on all patients and
22 healthy volunteers.
Results: No significant interhemispheric mean TMax differences of the Non-delayed group were
noted (p=0.75), but the mean TMax of ipsilateral MCA was significantly longer than that of the
contralateral MCA of the Left- and Right-delayed groups (ps<0.001), respectively. Compared to
healthy volunteers, the Right-delayed group performed significantly worse on most of the visuospatial
tests (ps<0.04), while the Left-delayed group performed significantly worse on most of the verbal
tests (ps<0.05). The performance of the Non-delayed group on all cognitive domains was similar
to that of healthy volunteers (ps>0.07).
Conclusion: TMax can be used to differentiate the chronic hypoperfusion state in unilateral CAS
patients. Prolonged TMax in the MCA of either hemisphere may lead to lateralized impairment in
cognition functions in patients with unilateral CAS.