Abstract
The exact spatial distribution of impaired cerebral autoregulation in carotid artery disease is unknown. In this pilot study, we present a new approach of multichannel near-infrared spectroscopy (mcNIRS) for non-invasive spatial mapping of dynamic autoregulation in carotid artery disease. In 15 patients with unilateral severe carotid artery stenosis or occlusion, cortical hemodynamics in the bilateral frontal cortex were assessed from changes in oxyhemoglobin concentration using 52-channel NIRS (spatial resolution ∼2 cm). Dynamic autoregulation was graded by the phase shift between respiratory-induced 0.1 Hz oscillations of blood pressure and oxyhemoglobin. Ten of 15 patients showed regular phase values in the expected (patho) physiological range.Five patients had clearly outlying irregular phase values mostly due to artifacts. In patients with a regular phase pattern, a significant side-to-side difference of dynamic autoregulation was observed for the cortical border zone area between the middle and anterior cerebral artery (p < 0.05). In conclusion, dynamic cerebral autoregulation can be spatially assessed from slow hemodynamic oscillations with mcNIRS. In high-grade carotid artery disease,cortical dynamic autoregulation is affected mostly in the vascular border zone. Spatial mapping of dynamic autoregulation may serve as a powerful tool for identifying brain regions at specific risks for hemodynamic infarction.
Highlights
Cerebral autoregulation protects the brain by maintaining cerebral perfusion stable against changes in systemic arterial blood pressure (ABP)
Using two-channel nearinfrared spectroscopy (NIRS), we have previously shown that such a phase shift can be observed with a certain intrinsic time lag between cerebral blood flow velocity (CBFV) and NIRS signals.[5]
We explored the potential of 52-channel NIRS to spatially measure impairment of dynamic cerebral autoregulation in patients with severe obstructive carotid artery disease
Summary
Cerebral autoregulation protects the brain by maintaining cerebral perfusion stable against changes in systemic arterial blood pressure (ABP). A noninvasive concept of assessing the individual integrity of autoregulation uses dynamic changes in cerebral blood flow velocity (CBFV) in basal cerebral arteries measured by transcranial Doppler sonography (TCD) and spontaneously occurring or noninvasively induced ABP changes (dynamic autoregulation).[2] TCD-based measures of autoregulation provide a mixture of the global autoregulatory function within the vascular territory of the insonated basal cerebral artery [e.g., middle cerebral artery (MCA)], not yielding information on specific areas with focal dysautoregulation Overall, it is not known so far whether there are specific areas of impaired autoregulation at all in carotid artery disease. Important both for the detection of patients with internal carotid artery (ICA) stenosis prone to ischemic infarction and for the pathophysiological understanding of the disease
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