Non-affected Hemispheres Research Articles

Dynamic But Not Static Cerebral Autoregulation Is Impaired in Acute Ischaemic Stroke

It remains unclear as to whether dynamic and static cerebral autoregulation (CA) are impaired in acute ischaemic stroke, and whether these changes are related to stroke subtype. This could have important implications with regard to post-stroke prognosis and the management of blood pressure (BP) in the acute post-ictal period. Using transcranial Doppler ultrasonography and non-invasive manipulation of BP, we compared both mechanisms in 61 patients with ischaemic stroke within 96 h of ictus, and 54 age- and sex-matched controls. There was no difference in static and dynamic CA indices between the various stroke subtypes. Combining all stroke subtypes dynamic autoregulation, as measured using thigh cuff release, was significantly impaired in both the affected and non-affected stroke hemispheres compared to controls (mean autoregulation index 4.1 ± 3.3, 4.8 ± 3.1 and 6.2 ± 2.3, respectively, p < 0.05). By comparison static autoregulation, assessed using isometric hand grip and thigh cuff inflation, was not significantly different. In conclusion, dynamic but not static CA appears to be globally impaired in acute ischaemic stroke. This deserves further study and may identify possibilities for therapeutic intervention.

Accuracy and Limitation of Functional Magnetic Resonance Imaging for Identification of the Central Sulcus: Comparison with Magnetoencephalography in Patients with Brain Tumors

The aim of the present study was to clarify the accuracy and limitation of functional magnetic resonance imaging (fMRI) for the identification of the central sulcus affected by brain tumors. Twelve normal volunteers and 11 patients with intracranial tumors adjacent to the central sulcus underwent fMRI and magnetoencephalography (MEG). Three patients were evaluated again after surgery. fMRI was performed with a 1.5 Tesla scanner during repetitive opening and closing of each hand. Cross-correlation function was used to identify activation areas, and the central sulcus was defined as the nearest sulcus to the highest activation spots that were determined by elevating correlation coefficient threshold. Somatosensory-evoked fields were measured using a whole head MEG system. The central sulcus was defined as the nearest sulcus to the N20m for the median nerve stimulus. fMRI and MEG coincided in defining the central sulcus in all 24 hemispheres of volunteers and all 10 examined nonaffected hemispheres of patients. The fMRI-defined central sulcus coincided with the MEG-defined central sulcus in nine (82%) but did not in two (18%) affected hemispheres of patients. The preoperative mismatch disappeared after surgery in one of the two patients. The present study indicates that fMRI successfully defined the central sulcus in most of the patients with brain tumors. However, in a few cases, fMRI was not reliable probably due to venous flow changes by tumor compression and/or compensational activity by brain tissues surrounding the primary sensorimotor cortex. For precise functional assessment of the brain affected by intracranial tumors, combination of fMRI and MEG will be recommended.

Relation of cerebral blood flow to motor and cognitive functions in chronic stroke patients.

The aim of this study was to examine the levels of cerebral blood flow in relation to motor and cognitive functions in 300 chronic unilateral stroke patients (age, 64 +/- 12 years; mean +/- SD). Cerebral blood flow was measured by the 133Xe inhalation method, adjusted for age, sex, and PCO2 level. Motor function was scored according to Brunnstrom hemiplegic staging and cognitive function according to the Hasegawa dementia rating scale tested in Japanese. Asymmetries of blood flow between affected and nonaffected hemispheres increased with lesion size and were highest in 11 embolic strokes (20 +/- 9%) and higher in 80 nonembolic cortical infarctions (11 +/- 11%) and 76 hemorrhages (9 +/- 7%) than in the group of 133 subcortical infarctions (2 +/- 6%) or 16 control subjects (1 +/- 2%). Severity of hemiparesis correlated with decreased cerebral blood flow in the affected hemisphere (P < .01) and increased hemispheric asymmetries of blood flow (P < 001). Cognitive impairments, after adjusting for age, correlated with decreased cerebral blood flow in the nonaffected hemisphere (P < .0001), left hemispheric lesions (P < .0005), and embolic stroke (P < .005) but not with asymmetries of blood flow. Among 67 patients having bilateral reductions of cerebral blood flow, 25 patients with left hemispheric lesions showed more severe cognitive impairments than among 42 patients with right hemispheric lesions (P < .05). We confirmed that severity of hemiparesis correlated with the degree of asymmetries of cerebral blood flow, reflecting the extent and location of the lesions. Bilateral reductions of cerebral blood flow in patients with left hemispheric lesions may in part contribute to cognitive impairments, indicating reductions of global neuronal activities in the contralateral hemisphere or diffuse cerebrovascular changes. Further studies of cerebral metabolism and follow-up of cerebral circulation are required to reveal the pathophysiology and clinical consequences.

Effects of Perfluorochemicals on the Depressed rCBF and Brain Metabolism shortly after the Hypertensive ICH

The effect of perfluorodecalin and perfluorotripropylamine, Fluosol DA-20% (FDA-20%), on the ischemic brain after hypertensive intracerebral hemorrhage (ICH) was evaluated and the mechanism investigated. Regional cerebral blood flow (rCBF), and cerebral metabolic ratios of oxygen (CMRO2) and glucose (CMRGlu) were measured before and after infusion of FDA-20%. The rCBF was estimated by single photon emission computed tomography using the 133Xe inhalation method, and CMRO2 and CMRGlu were determined by calculating arteriovenous difference between the femoral artery and the jugular bulb. The results showed: 1) The mean cerebral blood flow (mCBF) in both affected and non-affected hemispheres significantly increased by 10-20% over the control during 3 hours and 6-12 hours after infusion of 500 ml and 1000 ml FDA-20%, respectively. 2) Administration of 500 ml FDA-20% caused a maximal increase of 15% in CMRO2 and 24% in CMRGlu, and 1000 ml FDA-20% administration caused a maximal increase of 30% in CMRO2 and 75% in CMRGlu. 3) There was no significant change in mean blood pressure, arterial partial pressure of carbon dioxide and oxygen, or hematocrit before and after FDA-20% infusion. The results indicate that FDA-20% improved rCBF and brain metabolism in the ischemic brain of hypertensive ICH. FDA-20% may operate as an excellent oxygen carrier, and stimulate the brain metabolism directly.

Regional impairment of cerebral oxidative metabolism in Parkinson's disease.

Twenty-two patients affected by idiopathic Parkinsonism were studied using the oxygen-15 inhalation technique. The production of labelled metabolic water was found to be decreased in the parietal cerebral cortex, indicating an impairment in oxidative metabolism. This metabolic defect was localised mainly to the parietal cortex of the affected hemispheres; in non-affected hemispheres of patients presenting with unilateral Parkinsonism, the uptake was normal. In contrast, regional blood flow was not significantly altered. It is possible that this metabolic impairment is caused by chronic deafferentation.