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Objective: Blood oxygenation level dependent (BOLD) contrast functional MRI images show activated cortical areas by detecting a reduced concentration of deoxyhaemoglobin (deoxy-Hb) during neuronal activity; however, near infrared spectroscopy (NIRS) has shown various patterns of cerebral blood oxygenation (CBO) changes in the frontal lobe during cognitive tasks. To determine if various patterns of CBO changes occur in the frontal lobe when the brain is directly stimulated, changes in CBO in the frontal lobe induced by deep brain stimulation in patients with implanted electrodes were evaluated.Methods: Six patients were studied, including five with Parkinson's disease and one with essential tremor. To reduce tremor or rigidity, the electrodes were implanted at the thalamic nucleus ventralis intermedius (VIM: three Parkinson's disease and one essential tremor) or the globus pallidus internus (GPi: two Parkinson's disease). Using NIRS, changes of deoxy-Hb, oxyhaemoglobin (oxy-Hb) and total haemoglobin (total Hb) were measured in the bilateral frontal lobes during various stimulus conditions.Results: High frequency (120 Hz) GPi stimulation consistently increased oxy-Hb and total Hb with a decrease of deoxy-Hb in an intensity and time dependent manner. Oxy-Hb and total Hb increased immediately after the onset of stimulation and then gradually decreased when stimulation was continued. By contrast, high frequency (120 Hz) VIM stimulation decreased oxy-Hb, deoxy Hb and total Hb in an intensity dependent manner. In the severe tremor patient with VIM stimulation, frequency response was examined by decreasing stimulus frequencies; deoxy-Hb increased at high frequencies (70-40 Hz), and then decreased below the control level at low frequencies (30-0 Hz), whereas oxy-Hb and total Hb increased consistently at high and low frequencies.Conclusion: The electrical stimulation of GPi and VIM caused various CBO changes in the frontal lobe, which were similar to those found during cognitive tasks. Such a multiplicity of CBO changes in the frontal lobe may be caused by complex neuronal circuits in the frontal lobe which has many neuronal connections to other cortical areas or the basal ganglia. [ABSTRACT FROM AUTHOR]

Background. Superficial temporal artery–middle cerebral artery (STA–MCA) anastomosis has been used to prevent stroke in patients with moyamoya disease (MD) and non-moyamoya ischaemic disease (non-MD). However, little is yet known regarding the difference between these groups of patients in the extent to which the bypass contributes to maintaining adequate cerebral blood oxygenation (CBO), or the temporal changes after surgery. In the present study, we evaluated the CBO changes induced by bypass blood flow in patients with MD and non-MD during the peri-operative periods employing optical spectroscopy. Methods. We investigated 13 patients who underwent STA–MCA anastomosis, including 5 MD and 8 non-MD patients. We evaluated the effects of STA blood flow on the CBO in the MCA territory on the anastomosis side, employing visual light spectroscopy during surgery and near infrared spectroscopy (NIRS) at one week after surgery. Findings. In 4 MD patients and one non-MD patient, the STA blood flow increased the oxyhaemoglobin and cortical oxygen saturation (CoSO2), indicating that the bypass supplied blood flow to the ischaemic brain; the CBO changes were observed more frequently in MD than in non-MD patients (p < 0.02). The pre-anastomosis CoSO2 (65.4 ± 5.4%) in MD was significantly lower than that (72.8 ± 7.6%) in non-MD (p < 0.05). Postoperative NIRS demonstrated that the bypass began to supply blood flow to the brain in 5 non-MD patients whose bypass did not supply blood flow during surgery. Conclusions. Although MD has vessels of small diameter as compared to non-MD, the bypass begins to supply blood flow to the ischaemic brain earlier in MD than in non-MD after anastomosis. The fact that the CoSO2 in MD was lower than that in non-MD suggested that the perfusion pressure in MD was lower than that in non-MD, and this might account for the difference in the bypass blood supply after anastomosis between MD and non-MD. Our data suggest that, even if the bypass does not supply blood to the brain during surgery in non-MD, the bypass blood flow gradually increases after surgery. [ABSTRACT FROM AUTHOR]

The effects of spinal cord compression on conduction of compound action potentials (CAPs) in the dorsal column fibers at various stimulus frequencies were analysed in pentobarbital anesthetised cats. The L 6 posterior root was given 1 to 500 Hz stimuli, and the CAPs were recorded from the L 2 posterior column. The 100th CAP was recorded at 100, 200 and 500 Hz. The L 4 cord segment was compressed by stepped increments (0.5 mm/5 min.) with a plastic plate (4 × 10 mm) until the responses at 1 Hz disappeared, then the compression was released. Before compression, each CAP at all frequencies showed almost uniform amplitudes and latencies. During compression, the CAPs were not altered significantly at any frequency until the spinal cord was compressed 2.5 - 4.0 mm. Further compression produced a progressive decrease in amplitude and increase in latency of the CAPs. At 500 Hz, however, the conduction block (amplitude loss, latency increase) was much severer than that produced at lower frequencies. After release of compression, the CAPs at all frequencies recovered progressively, and became almost stable after about 1 hour. The recovery rate of amplitude was only about 30% compared to the amplitude before compression at 500 Hz, and about 50% at 1 and 200 Hz. However, the recovery rate of amplitude at 100 Hz (65%) exceeded those at 1 and 200 Hz. To observe the difference in recovery rates among them, all the trains of CAPs were analyzed. Before compression, the amplitudes were almost uniform at stimulus frequencies as high as 500 Hz. After decompression, the amplitude decreased progressively at 500 Hz. At 100 Hz the amplitude increased and reached a steady level after the 5th CAP. At 200 Hz, the amplitude increased transiently and decreased to that of the 1st CAP. In conclusion, the inability of injured fibers to transmit impulses from high frequency stimuli indicates incomplete impairment of spike generation in the dorsal column fibers, which were injured by compression. [ABSTRACT FROM AUTHOR]

Background and Purpose: Blood oxygenation level dependent contrast functional magnetic resonance imaging (BOLD-fMRI) has been applied to functional mapping in brain disorders, based on the assumption that normal adults and patients with brain disorders exhibit similar evoked cerebral blood oxygenation (CBO) changes. This study compared evoked CBO changes measured by near infrared spectroscopy (NIRS) with the activation mapping obtained by BOLD-fMRI in patients with cerebral ischaemia.Methods: The study involved six normal adults and six patients with cerebral ischaemia. Hand grasping was performed as a motor task. All patients could perform the task similarly to the controls at the time of examination, but single photon emission computed tomography demonstrated low baseline cerebral blood flow and a decreased haemodynamic reserve in the primary sensorimotor cortex on the lesion side. Using NIRS, concentration changes of deoxyhaemoglobin (Deoxy-Hb), oxyhaemoglobin (Oxy-Hb), and total haemoglobin (Total-Hb) were measured in the primary sensorimotor cortex contralateral to the task. BOLD-fMRI signals were measured by 1.5 T magnetic resonance imaging using an echo-planar technique. Activation maps were calculated by statistical parametric mapping.Results: In the controls, Deoxy-Hb decreased in association with increases of Oxy-Hb and Total-Hb in the primary sensorimotor cortex during the task. However, in the patients, Deoxy-Hb increased significantly from baseline, while Oxy-Hb and Total-Hb also increased, indicating the presence of rCBF increases in response to neuronal activation. BOLD-fMRI demonstrated only limited activation areas in the primary sensorimotor cortex on the lesion side.Conclusion: The CBO changes in patients with cerebral ischaemia differed from those of normal adults; Deoxy-Hb was increased in activation areas of the patients. This implies that BOLD-fMRI may overlook activation areas in the patients unless both increases and decreases of signal are taken into consideration. [ABSTRACT FROM AUTHOR]