Near infrared spectroscopy and transcranial Doppler in monohemispheric stroke.

We simultaneously performed near infrared spectroscopy (NIRS) and transcranial Doppler (TCD) to evaluate the effects of hypercapnia as well as of scalp ischemia on the blood flow at two different depth levels within the brain and of the scalp vessels. A decrease in the backscattered light intensity, meaning an increment of blood volume, was detected at the end of hypercapnia in all healthy subjects. This decrement was partly masked by ischemia in the cutaneous vessels. In 2 patients with a monohemispheric lesion in the middle cerebral artery (MCA) territory, an increase in NIRS response was found in the healthy hemisphere, while in the stroke side the CO2-induced changes were negligible. TCD data showed a similar increment of blood flow velocity to the hypercapnia in both hemispheres, with no differences between the affected and normal side in 1 patient, whereas in the second one, no increment was observed on the affected side, probably due to internal carotid artery stenosis. The two methods nicely integrate: TCD mainly tests subcortical changes in the MCA flow, while NIRS is exquisitely sensitive to cortical arterioles and capillary blood flow modifications

Early cerebral hemodynamic changes during passive movements and motor recovery after stroke.

Recovery from hemiplegia is a complex phenomenon that depends on various adaptive processes involving both the affected and the unaffected hemisphere. Our aim in this study was to investigate changes in cerebral perfusion in hemiplegic stroke patients during passive movements and their correlation with the subsequent motor recovery. The study included 30 patients with single, subcortical ischemic cerebral lesions. Within 14 days (range 8 to 14 days) from stroke onset, all patients were examined for the effects of passive elbow movements on cerebral blood flow in the middle cerebral arteries (MCAs) by means of bilateral transcranial Doppler (TCD) ultrasonography. On the same day as TCD assessment, they were also evaluated clinically with the Canadian Neurological Scale (CNS) and with Medical Research Council (MRC) scale for motor deficit of the affected arm. A clinical evaluation using the same scales was repeated after two months of motor rehabilitation therapy. We investigated the relationship between changes of Mean Flow Velocity (MFV) during passive movements and degree of recovery after stroke. The logistic regression procedure indicated that out of all factors considered as possibly related to a good clinical motor deficit recovery of the affected arm, evaluated by means of MRC, only the MFV percentage increase played a predictive role. In particular, for each additional point of contralateral MFV percentage increase during passive movement of the affected arm, the relative probability of good clinical recovery increased 5.68 times (95% CI=1.76-18.40; p=0.004). Similar results were found when the clinical recovery was measured by means of the CNS (slope=0.40, p<0.001). Passive movements in hemiplegic stroke patients before clinical recovery elicit activation patterns that may be critical for the restoration of motor function.I n particular, early and consistent activation of the affected hemisphere, as detected with TCD, seems to predict the positive evolution of a motor deficit

Transcranial Doppler and near-infrared spectroscopy can evaluate the hemodynamic effect of carotid artery occlusion

Background and Purpose-Cerebral hemodynamic and metabolic changes can compensate for the decrease in cerebral blood flow occurring in patients with carotid occlusive disease. At present, a complete assessment of the cerebral adaptive status is only possible with positron-emission tomography. Near-infrared spectroscopy (NIRS) is a noninvasive technique that, providing a real time assessment of fluctuations in cerebral hemoglobin, has been used to estimate the cerebral blood volume and to measure cerebral vasomotor reactivity (VMR). Moreover, NIRS technology, by allowing the absolute measurement of absorption and scattering coefficients of brain, can determine the oxyhemoglobin and deoxyhemoglobin concentrations in situ in the blood stream. Methods-In order to evaluate different aspects of the cerebral hemodynamic status, 27 subjects with symptomatic and asymptomatic carotid artery occlusion and 30 healthy subjects underwent a simultaneous examination by means of transcranial Doppler (TCD), able to reliably detect collateral circulation and VMR, and NIRS at rest condition and during CO2 reactivity test. Results-The main finding of this study was the demonstration of a difference between asymptomatic and symptomatic patients in terms of mean flow velocity increase (52.4% versus 21.0%; P<0.001) estimated by TCD and of hemoglobin saturation increase measured by NIRS (6.8% versus 3.8%; P=0.015). Conclusions-The opportunity to perform NIRS and TCD simultaneously provides useful information about both hemodynamic and metabolic cerebral adaptive status in patients with occlusive disease in a simple, noninvasive, and reliable way

Transcranial Doppler and Near Infrared Spectroscopy can evaluate the hemodynamic effect of carotid artery occlusion

BACKGROUND AND PURPOSE: Cerebral hemodynamic and metabolic changes can compensate for the decrease in cerebral blood flow occurring in patients with carotid occlusive disease. At present, a complete assessment of the cerebral adaptive status is only possible with positron-emission tomography. Near-infrared spectroscopy (NIRS) is a noninvasive technique that, providing a real time assessment of fluctuations in cerebral hemoglobin, has been used to estimate the cerebral blood volume and to measure cerebral vasomotor reactivity (VMR). Moreover, NIRS technology, by allowing the absolute measurement of absorption and scattering coefficients of brain, can determine the oxyhemoglobin and deoxyhemoglobin concentrations in situ in the blood stream. METHODS: In order to evaluate different aspects of the cerebral hemodynamic status, 27 subjects with symptomatic and asymptomatic carotid artery occlusion and 30 healthy subjects underwent a simultaneous examination by means of transcranial Doppler (TCD), able to reliably detect collateral circulation and VMR, and NIRS at rest condition and during CO2 reactivity test. RESULTS: The main finding of this study was the demonstration of a difference between asymptomatic and symptomatic patients in terms of mean flow velocity increase (52.4% versus 21.0%; P<0.001) estimated by TCD and of hemoglobin saturation increase measured by NIRS (6.8% versus 3.8%; P=0.015). CONCLUSIONS: The opportunity to perform NIRS and TCD simultaneously provides useful information about both hemodynamic and metabolic cerebral adaptive status in patients with occlusive disease in a simple, noninvasive, and reliable way