Noriaki Yokose

Bedside Monitoring of Cerebral Blood Oxygenation and Hemodynamics after Aneurysmal Subarachnoid Hemorrhage by Quantitative Time-Resolved Near-Infrared Spectroscopy

BACKGROUND Early detection of vasospasm is essential for the treatment of delayed ischemic neurological deficits in subarachnoid hemorrhage (SAH). We evaluated cerebral blood oxygenation (CBO) changes after SAH employing quantitative time-resolved near-infrared spectroscopy (TR-NIRS) for this purpose. METHODS We investigated 11 age-matched controls and 14 aneurysmal SAH patients, including 10 patients with WFNS grade V and 4 patients with grade II. Employing TR-NIRS, we measured the cortical oxygen saturation (CoSO(2)) and baseline hemoglobin concentrations in the middle cerebral artery territory. Measurements of TR-NIRS and transcranial Doppler sonography (TCD) were performed repeatedly after SAH. RESULTS In six patients, the CoSO(2) and hemoglobin concentrations remained stable after SAH; digital subtraction angiography (DSA) did not reveal vasospasm in these patients. In eight patients, however, CoSO(2) and total hemoglobin decreased abruptly between 5 and 9 days after SAH. DSA revealed diffuse vasospasms in six of eight patients. The reduction of CoSO(2) predicted occurrence of vasospasm at a cutoff value of 3.9%-6.4% with 100% of sensitivity and 85.7% of specificity. TCD failed to detect the vasospasm in four cases, which TR-NIRS could detect. Finally, TR-NIRS performed on Day 1 after SAH revealed significantly higher CoSO(2) than that of controls (p = .048), but there was no significant difference in total hemoglobin. CONCLUSION TR-NIRS detected vasospasm by evaluating the CBO in the cortex and may be more sensitive than TCD, which assesses the blood flow velocity in the M1 portion. The cerebral oxygen metabolism in SAH might be reduced by brain damage due to aneurysmal rupture.

Intraoperative EC-IC Bypass Blood Flow Assessment With Indocyanine Green Angiography in Moyamoya and Non-Moyamoya Ischemic Stroke

OBJECTIVE Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis has been used in moyamoya disease (MD) and non-moyamoya ischemic stroke (non-MD). It is important to monitor hemodynamic changes caused by bypass surgery for postoperative management. We evaluated the bypass blood flow during STA-MCA anastomosis by using indocyanine green (ICG) fluorescence angiography. METHODS We evaluated the bypass blood flow in 13 MD and 21 non-MD patients during STA-MCA anastomosis by means of ICG angiography with injection of ICG into the anastomosed STA. The ICG perfusion area was calculated when the ICG fluorescence intensity reached maximum. We measured cortical oxygen saturation before anastomosis by means of visual light spectroscopy. RESULTS ICG angiography demonstrated bypass blood flow from the anastomosed STA to the cortical vessels in all patients. The ICG perfusion area in MD (20.7 ± 6.6 cm(2)) was significantly larger than that in non-MD (8.4 ± 9.1 cm(2), P < 0.05). The cortical oxygen saturation (58.9% ± 8.3%) in MD was significantly lower than that in non-MD (73.4% ± 9.5%, P < 0.05). CONCLUSIONS ICG angiography with injection of ICG into the bypass artery allowed quantitative assessment of bypass blood flow. The bypass supplies blood flow to a greater extent in MD than in non-MD during surgery. This might be caused by a larger pressure gradient between the anastomosed STA and recipient vessels in MD. These observations indicate that MD requires careful control of systemic blood pressure after surgery to avoid cerebral hyperperfusion syndrome. ICG angiography is considered useful for facilitating safe and accurate bypass surgery and providing information for postoperative management.

Development of a new rehabilitation system based on a brain-computer interface using near-infrared spectroscopy.

We describe the set-up for an electrical muscle stimulation device based on near-infrared spectroscopy (NIRS), designed for use as a brain-computer interface (BCI). Employing multi-channel NIRS, we measured evoked cerebral blood oxygenation (CBO) responses during real motor tasks and motor-imagery tasks. When a supra-threshold increase in oxyhemoglobin concentration was detected, electrical stimulation (50 Hz) of the biceps brachii muscle was applied to the side contralateral to the hand grasping task or ipsilateral to the motor-imagery task. We observed relatively stable and reproducible CBO responses during real motor tasks with an average accuracy of 100%, and during motor imagery tasks with an average accuracy of 61.5%. Flexion movement of the arm was evoked in all volunteers in association with electrical muscle stimulation and no adverse effects were noted. These findings suggest that application of the electrical muscle stimulation system based on a NIRS-BCI is non-invasive and safe, and may be useful for the physical training of disabled patients.

Bedside Assessment of Cerebral Vasospasms After Subarachnoid Hemorrhage by Near Infrared Time-Resolved Spectroscopy

We examined the usefulness of near infrared time-resolved spectroscopy (TRS) for detection of vasospasm in subarachnoid hemorrhage (SAH). We investigated seven aneurysmal SAH patients with poor clinical conditions (WFNS grade V) who underwent endovascular coil embolization. Employing TRS, we measured the oxygen saturation (SO(2)) and baseline hemoglobin concentrations in the cortices. Measurements of TRS and transcranial Doppler sonography (TCD) were performed repeatedly for 14 days after SAH. In four of the seven patients, the SO(2) and hemoglobin concentrations measured in the brain tissue of the middle cerebral artery territory remained stable after SAH. However, in three patients, TRS revealed abrupt decreases in SO(2) and total hemoglobin between 5 and 9 days after SAH. Cerebral angiography performed on the same day revealed severe vasospasms in these patients. Although TCD detected the vasospasm in two of three cases, it failed to do so in one case. TRS could detect vasospasms after SAH by evaluating the cortical blood oxygenation.

Theoretical and Experimental Investigation of the Influence of Frontal Sinus on the Sensitivity of the NIRS Signal in the Adult Head

The sensitivity of the near-infrared spectroscopy signal to the brain activation depends on the thickness and structure of the superficial tissues. The influence of the frontal sinus, which is void region in the skull, on the sensitivity to the brain activation is investigated by the time-resolved experiments and the theoretical modelling of the light propagation in the head. In the time-resolved experiments, the mean-time of flight for the forehead scarcely depends upon the existence of the frontal sinus when probe spacing was shorter than 30 mm. The partial optical path length in the brain, which indicates the sensitivity of the near-infrared spectroscopy signal to the brain activation, in a simplified head model is predicted by Monte Carlo simulation. The influence of the frontal sinus on the sensitivity of the signal depends on the thickness of the skull and the depth of the frontal sinus.

EC-IC bypass function in Moyamoya disease and non-Moyamoya ischemic stroke evaluated by intraoperative indocyanine green fluorescence angiography.

Indocyanine green (ICG) emits near-infrared fluorescence when it is excited by near-infrared light. The near infrared fluorescence of ICG was applied to the imaging of cerebral vessels during neurosurgical operations such as clipping of aneurysms. In this study, ICG angiography was applied to extracranial-intracranial (EC-IC) bypass surgery to evaluate the hemodynamic changes induced by bypass in moyamoya disease (MD) and non-moyamoya ischemic diseases (non-MD). These patients underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. We compared the cortical areas where the bypass supplied blood flow between MD and non-MD. ICG angiography clearly demonstrated the bypass blood flow from the anastomosed STA to the cortical vessels including arteries, capillaries, and veins in both MD and non-MD. Interestingly, the anastomosed STA supplied blood flow to a larger cortical area in MD than non-MD. The bypass supplied greater extent of blood flow to the ischemic brain in MD than in non-MD. This difference might be caused by the fact that the perfusion pressure was lower in MD than in non-MD.

Changes in Cerebral Blood Oxygenation and Hemodynamics After Endovascular Treatment of Vascular Malformation Measured by Time-Resolved Spectroscopy

Although endovascular treatment has a high success rate, it is not clear how endovascular treatment affects cerebral perfusion and hemodynamics during the perioperative period. We evaluated changes in cerebral blood oxygenation (CBO) repeatedly after endovascular treatment employing time-resolved spectroscopy (TRS). We investigated a patient (10 months old, female) who suffered cerebral arteriovenous fistula. Cerebral angiography demonstrated a pial arteriovenous fistula with three feeders (left PICA, SCA, and AICA). TRS demonstrated a decrease of oxyhemoglobin, total hemoglobin, and oxygen saturation associated with an increase of deoxyhemoglobin in all of the regions measured just after embolization, indicating that embolization improved hyperemia caused by the AV shunt. Interestingly, progressive improvement of hyperemia was observed 3 and 8 days after embolization of the feeders. The present study demonstrated that embolization of the feeders caused progressive changes in CBO and hemodynamics during the perioperative period. TRS may be a useful tool for monitoring cerebral blood perfusion changes after endovascular surgery.

S8-4. Detection of cerebral ischemia employing time-resolved spectroscopy

We evaluated cerebral blood oxygenation (CBO) changes after SAH employing quantitative time-resolved near infrared spectroscopy (TR-NIRS). We investigated 11 age-matched controls and 14 aneurysmal SAH patients. Employing TR-NIRS, we measured the cortical oxygen saturation (CoSO 2 ) and baseline hemoglobin concentrations in the middle cerebral artery territory. Measurements of TR-NIRS and transcranial Doppler sonography (TCD) were performed repeatedly after SAH. In six patients, the CoSO 2 and hemoglobin concentrations remained stable after SAH; DSA did not reveal vasospasm in these patients. In eight patients, however, CoSO 2 and total hemoglobin decreased abruptly between five and nine days after SAH. DSA revealed diffuse vasospasms in six out of eight patients. The reduction of CoSO 2 predicted occurrence of vasospasm at a cut of value of 3.9–6.4% with 100% of sensitivity and 85.7% of specificity. TCD failed to detect the vasospasm in four cases, which TR-NIRS could detect. Finally, TR-NIRS performed on day 1 after SAH revealed significantly higher CoSO 2 than that of controls; but there was no significant difference in total hemoglobin. TR-NIRS detected vasospasm by evaluating the CBO in the cortex, and may be more sensitive than TCD. The cerebral oxygen metabolism in SAH might be reduced by brain damage due to aneurysmal rupture.

Primary central nervous system malignant lymphoma in a patient with rheumatoid arthritis receiving low-dose methotrexate treatment

Abstract We report the first case of primary central nervous system lymphoma (PCNSL) developing in a patient with rheumatoid arthritis (RA) undergoing low-dose methotrexate therapy (LD-MTX). The characteristic clinical management and course in our experience of the present case illustrate the important points about PCNSL in methotrexate-associated lymphoproliferative disorders (MTX-LPD). The number of cases of MTX-LPD in RA patients may increase in the future, since current treatment strategies for RA recommend starting MTX use in early stage RA, and recent insights have tended to show an increase with higher doses.

131. Changes in cerebral blood flow and oxygenation in cerebral ischemia investigated by NIRS, SPECT and BOLD contrast functional MRI

Pain is a multidimensional sensory experience including discriminative, affective, and cognitive components. Functional neuroimaging has revealed that those components are represented in multiple, discrete brain areas (pain matrix) including the thalamus, primary and secondary somatosensory (S1/S2), insular, anterior cingulate, and prefrontal cortices. Using functional magnetic resonance imaging (fMRI), we have found that the pain-related blood oxygenation level-dependent (BOLD) signals decay rapidly and suppress the BOLD signals by visually guided saccade, a totally different modality from pain. We hypothesized that pain-related brain activity includes an inhibitory component, and developed a hierarchical model of pain matrix where the bottom-up and top-down components interact with each other. This model explains the modulatory effects of top-down cognitive modalities such as expectation, attention, emotion, hypnosis, and placebo in pain-related activation. Chronic pain is explained as an exaggerated top-down component in the medial nociceptive system eventually leading to gray matter atrophy. In a model of chronic low back pain (LBP) using mechanical stimulation and fMRI, the LBP matrix consisted of the anterior insular, posterior cingulate, prefrontal cortices, and the premotor area, but spared the S1/S2. The LBP matrix predominantly involves the top-down, medial nociceptive system, and less of the bottom-up, lateral nociceptive system.