Background and aims: Fluctuations in neurological status are frequently seen during first few days in thrombolysed acute ischemic stroke (AIS) patients. Underlying mechanisms for these fluctuations often remain unclear. Cerebral homeostatic balance is regulated by autoregulation and neurovascular coupling (NVC). We hypothesized that neurovascular uncoupling in AIS contributes to the fluctuations in neurological status.
Methods: In this ongoing prospective study, consecutive and thrombolyzed AIS patients were recruited within 12 hours of symptom-onset. Serial CT perfusion (CTP) imaging (within 12 hours, at 24 and 72 hours after symptom-onset) were performed. Serial Quantitative EEG (QEEG) were performed, close to CTP imaging. Power within the alpha band (8-15Hz) was determined in each channel using epochs of 10-seconds % calculated for each hemisphere. Continuous transcranial Doppler (TCD) recording were obtained from both middle cerebral arteries, simultaneously with EEG. Neurological status was monitored with serial NIH stroke scale (NIHSS) scores. Neurovascular uncoupling was defined as a mismatch among CTP, QEEG and clinical findings. QEEG, CTP and TCD data were analysed independently by investigators blinded to the clinical findings.
Results: A total of 32 patients (19 male, median age 68 years (range 56-86) were included. Median NIHSS score at recruitment was 8 points (range 1-24). NIHSS fluctuations by 4 or more points (deterioration followed by improvement or deterioration following improvement in absence of re-occlusion) were noted in 13 (40%) cases. Increasing cerebral edema (2 cases) and regional hyperperfusion (4 cases) were seen on serial CTP. Remaining 7 cases showed serial improvement in CTP. QEEG showed significantly increased inter-hemispheric alpha band power ratio (unaffected hemisphere/affected hemisphere ratio more than 1.5), irrespective of the CTP and TCD results, suggestive of neurovascular uncoupling as the underlying mechanism for early neurological fluctuations.
Conclusion: Neurovascular uncoupling is a relatively frequent phenomenon during first few days of acute ischemic stroke. Multi-modal monitoring is useful in identifying these patients for appropriate therapeutic decision making.