Silent cortical neuronal damage in atherosclerotic disease of the major cerebral arteries

Long-Term Cognitive Changes after Revascularization Surgery in Adult Patients with Ischemic Moyamoya Disease

Introduction

Revascularization surgery for adult moyamoya disease (MMD) with ischemic presentation changes cognitive function and prevents further cerebral ischemic events. Most studies however repeated neuropsychological evaluation within 1 year after surgery. Our previous prospective cohort study of adult patients with MMD with misery perfusion who underwent direct revascularization surgery showed cognitive improvement and decline in 31% and 44%, respectively, of the patients 2 months after surgery. The present prospective study aimed to elucidate the 5-year cognitive changes after direct revascularization surgery in adult patients with cerebral misery perfusion due to ischemic MMD by following the same patients.

Methods

In total, 31 patients were prospectively followed up for 5 years after direct revascularization surgery. Five types of neuropsychological tests were performed preoperatively, 2 months after surgery, and at the end of the 5-year follow-up. Cerebral blood flow (CBF) in the symptomatic cerebral hemisphere relative to that in the ipsilateral cerebellar hemisphere (hemispheric relative CBF [RCBF]) was measured using brain perfusion single-photon emission computed tomography preoperatively and at the end of the 5-year follow-up.

Results

Based on results of pre- and postoperative neuropsychological tests, 11, 10, and 10 patients showed cognitive improvement, no change in cognitive function, and cognitive decline, respectively, at the end of the 5-year follow-up. These ratios were not significantly different compared with those 2 months after surgery (cognitive improvement, no change in cognitive function, and cognitive decline in 10, 8, and 13 patients, respectively). Although hemispheric RCBF was significantly greater at the end of the 5-year follow-up than before surgery in patients with cognitive improvement (80.7 ± 6.1% vs. 92.9 ± 5.5%; p = 0.0033) and in those showing no change in cognitive function (85.6 ± 3.5 vs. 91.5 ± 5.2%; p = 0.0093), this value was significantly lower at the end of the 5-year follow-up than before surgery in patients with cognitive decline (83.8 ± 3.7 vs. 81.0 ± 5.8%; p = 0.0367).

Conclusion

One-third of adult patients with cerebral misery perfusion due to ischemic MMD who underwent direct revascularization surgery exhibited cognitive improvement, and one-third exhibited decline at the end of the 5-year follow-up. The former and latter patients had increased and decreased CBF, respectively, in the affected cerebral hemisphere at the end of the 5-year follow-up compared with preoperative brain perfusion.

Combined structural and diffusion tensor imaging detection of ischemic injury in moyamoya disease: relation to disease advancement and cerebral hypoperfusion

OBJECTIVE

The microstructural integrity of gray and white matter is decreased in adult moyamoya disease, suggesting covert ischemic injury as a mechanism of cognitive dysfunction. Establishing a microstructural brain imaging marker is critical for monitoring cognitive outcomes following surgical interventions. The authors of the present study determined the pathophysiological basis of altered microstructural brain injury in relation to advanced arterial occlusion, cerebral hypoperfusion, and cognitive function.

METHODS

The authors examined 58 patients without apparent brain lesions and 30 healthy controls by using structural MRI, as well as diffusion tensor imaging (DTI). Arterial occlusion in each hemisphere was classified as early or advanced stage based on MRA and posterior cerebral artery (PCA) involvement. Regional cerebral blood flow (rCBF) was measured with N-isopropyl-p-[123I]-iodoamphetamine SPECT. Furthermore, cognitive performance was examined using the Wechsler Adult Intelligence Scale, Third Edition and the Trail Making Test (TMT). Both voxel- and region of interest-based analyses were performed for groupwise comparisons, as well as correlation analysis, using parameters such as cognitive test scores; gray matter volume; fractional anisotropy (FA) of association fiber tracts, including the inferior frontooccipital fasciculus (IFOF) and superior longitudinal fasciculus (SLF); PCA involvement; and rCBF.

RESULTS

Compared to the early stages, advanced stages of arterial occlusion in the left hemisphere were associated with a lower Performance IQ (p = 0.031), decreased anterior cingulate volumes (p = 0.0001, uncorrected), and lower FA in the IFOF, cingulum, and forceps major (all p < 0.01, all uncorrected). There was no significant difference in rCBF between the early and the advanced stage. In patients with an advanced stage, PCA involvement was correlated with a significantly lower Full Scale IQ (p = 0.036), cingulate volume (p < 0.01, uncorrected), and FA of the left SLF (p = 0.0002, uncorrected) compared to those with an intact PCA. The rCBF was positively correlated with FA of the SLF, IFOF, and forceps major (r > 0.34, p < 0.05). Global gray matter volumes were moderately correlated with TMT part A (r = 0.40, p = 0.003). FA values in the left SLF were moderately associated with processing speed (r = 0.40, p = 0.002).

CONCLUSIONS

Although hemodynamic compensation may mask cerebral ischemia in advanced stages of adult moyamoya disease, the disease progression is detrimental to gray and white matter microstructure as well as cognition. In particular, additional PCA involvement in advanced disease stages may impair key neural substrates such as the cingulum and SLF. Thus, combined structural MRI and DTI are potentially useful for tracking the neural integrity of key neural substrates associated with cognitive function and detecting subtle anatomical changes associated with persistent ischemia, as well as disease progression.

DSC perfusion-based collateral imaging and quantitative T2 mapping to assess regional recruitment of leptomeningeal collaterals and microstructural cortical tissue damage in unilateral steno-occlusive vasculopathy

Leptomeningeal collateral supply is considered pivotal in steno-occlusive vasculopathy to prevent chronic microstructural ischaemic tissue damage. The aim of this study was to assess the alleged protective role of leptomeningeal collaterals in patients with unilateral high-grade steno-occlusive vasculopathy using quantitative (q)T2 mapping and perfusion-weighted imaging (PWI)-based collateral abundance. High-resolution qT2 was used to estimate microstructural damage of the segmented normal-appearing cortex. Volumetric abundance of collaterals was assessed based on PWI source data. The ratio relative cerebral blood flow/relative cerebral blood volume (rCBF/rCBV) as a surrogate of relative cerebral perfusion pressure (rCPP) was used to investigate the intravascular hemodynamic competency of pial collateral vessels and the hemodynamic state of brain parenchyma. Within the dependent vascular territory with increased cortical qT2 values (P = 0.0001) compared to the contralateral side, parenchymal rCPP was decreased (P = 0.0001) and correlated negatively with increase of qT2 (P  < 0.05). Furthermore, volumetric abundance of adjacent leptomeningeal collaterals was significantly increased (P < 0.01) and negatively correlated with changes of parenchymal rCPP (P = 0.01). Microstructural cortical damage is closely related to restrictions of antegrade blood flow despite increased pial collateral vessel abundance. Therefore, increased leptomeningeal collateral supply cannot necessarily be regarded as a sign of effective compensation in patients with high-grade steno-occlusive vasculopathy.

Combination of Single- and Paired-Pulse Somatosensory Evoked Potentials in Ischemic Monitoring: Preliminary Investigation in Carotid Endarterectomy

Introduction

Severe ischemia induces cerebral excitability imbalance before completion of infarct. To investigate the clinical availability of this imbalance with ischemic monitoring, paired-pulse somatosensory evoked potentials (SEPs) were performed in conjunction with conventional SEPs during carotid endarterectomy.

Methods

For carotid endarterectomy patients with hemodynamic deficits of the middle cerebral artery area (n = 34), the excitability imbalances (Q) were measured by paired-pulse SEPs, wherein the second response (A₂) was divided by the first (A₁; Q = A₂/A₁). Regional cerebral saturation (rSO₂) was also measured. Occlusion was performed twice using shunting.

Results

Each carotid occlusion induced a significant decrease in mean A₁ and rSO₂, and an increase in mean Q values (p < 0.001), which returned to the baseline level after occlusion. While neuronal imbalances were mostly transient, persistently increased Q values were observed in four cases (11.8%), all indicating postoperative abnormalities in diffusion-weighted magnetic resonance imaging (100%). Meanwhile, A₁ detected the postoperative abnormality in only one case (25%). Preoperative Q values at the time of surgery were significantly higher in symptomatic patients having the upper limb deficits than those without (p < 0.01), indicating persistent or permanent imbalances.

Conclusion

Paired-pulse SEPs reliably identified transient, persistent or permanent neuronal imbalances, depending on the ischemic severity. These preliminary results indicated that paired-pulse SEPs, in combination with conventional SEPs (A₁), may offer better ischemic monitoring.

Acquired Hemicerebral Atrophy Secondary to Chronic Internal Carotid Steno-Occlusive Disease: A Case Series

Cerebral atrophy is a common finding in elderly patients; however, cerebrovascular disease causing progressive focal cerebral atrophy and dysfunction is unusual. In this report, we present 3 cases of hemicerebral atrophy due to ipsilateral internal carotid artery (ICA) stenosis or occlusion mimicking neurodegenerative conditions. Patient 1 had a frontal dysexecutive syndrome potentially consistent with a diagnosis of behavioral variant frontotemporal dementia; however, neuroimaging revealed a chronically occluded left ICA and a pattern of atrophy restricted to the left middle cerebral artery territory, suggestive of a vascular etiology. Patient 2 presented with progressively worsening seizures and right-sided weakness consistent with left hemispheric dysfunction, with radiographic evidence of left hemicerebral atrophy. Angiography revealed a chronic dissection of the left ICA leading to left cerebral hypoperfusion. Patient 3 had asymmetric parkinsonism, alien limb, and cognitive impairment consistent with a diagnosis of corticobasal syndrome. His imaging, however, revealed atrophy and encephalomalacia within the anterior circulation watershed territories with chronic, severe stenosis of the left ICA suggestive of a chronic hypoperfused state. In this case series, we report 3 examples of hemicerebral atrophy secondary to chronic ipsilateral ICA vascular disease with diverse progressive clinical symptoms mimicking primary neurodegenerative conditions. This case series highlights the importance of considering chronic hypoperfusion and large-vessel severe stenosis or occlusion in patients with cognitive impairment and evidence of asymmetric brain atrophy. In addition to symptomatic treatment, the management of vascular risk factors including treatment with antiplatelet agents, statins, and revascularization procedures can be considered.

Hemodynamics and oxygen extraction in chronic large artery steno-occlusive disease: Clinical applications for predicting stroke risk

Depending on the adequacy of collateral sources of blood flow, arterial stenosis or occlusion may lead to reduced perfusion pressure and ultimately reduced blood flow in the distal territory supplied by that vessel. There are two well-defined compensatory mechanisms to reduced pressure or flow - autoregulatory vasodilation and increased oxygen extraction fraction. Other changes, such as metabolic downregulation, are likely. The positive identification of autoregulatory vasodilation and increased oxygen extraction fraction in humans is an established risk factor for future ischemic stroke in some disease states such as atherosclerotic carotid stenosis and occlusion. The mechanisms by which ischemic stroke may occur are not clear, and may include an increased vulnerability to embolic events. The use of hemodynamic assessment to identify patients with occlusive vasculopathy at an increased risk for stroke is very appealing for several different patient populations, such as those with symptomatic intracranial atherosclerotic disease, moyamoya phenomenon, complete internal carotid artery occlusion, and asymptomatic cervical carotid artery stenosis. While there is very good data for stroke risk prediction in some of these groups, no intervention based on these tools has been proven effective yet. In this manuscript, we will review these topics above and identify areas for future research.

The Role of Circular RNAs in Cerebral Ischemic Diseases: Ischemic Stroke and Cerebral Ischemia/Reperfusion Injury

Cerebral ischemic diseases including ischemic stroke and cerebral ischemia reperfusion injury can result in serious dysfunction of the brain, which leads to extremely high mortality and disability. There are no effective therapeutics for cerebral ischemic diseases to date. Circular RNAs are a kind of newly investigated noncoding RNAs. It is reported that circular RNAs are enriched in multiple organs, especially abundant in the brain, which indicates that circular RNAs may be involved in cerebral physiological and pathological processes. In this chapter, we will firstly review the pathophysiology, underlying mechanisms, and current treatments of cerebral ischemic diseases including ischemic stroke and cerebral ischemia/reperfusion injury. Secondly, the characteristics and function of circular RNAs will be outlined, and then we are going to introduce the roles circular RNAs play in human diseases. Finally, we will summarize the function of circular RNAs in cerebral ischemic diseases.

Chronological Changes in Brain Blood Flow and Central Benzodiazepine Receptor Binding Potential in a Patient with Symptomatic Epilepsy after Surgery for Aneurysmal Subarachnoid Hemorrhage: 123I-Iomazenil Single-Photon Emission Computed Tomography Studies

Early ¹²³I-iomazenil single-photon emission computed tomography (SPECT) images are correlated with blood flow in the brain, and late images are correlated with cortical benzodiazepine receptor binding potential. Reduced metabolism in the contralateral cerebral hemisphere is indicated by crossed cerebellar hypoperfusion (CCH). We present the case of a 63-year-old man who developed symptomatic epilepsy 13 days after surgery for an aneurysmal subarachnoid hemorrhage. Early images on ¹²³I-iomazenil SPECT 2 days after seizure onset revealed CCH and hyperperfusion in the affected cerebral hemisphere where benzodiazepine receptor binding potential was reduced in late images on ¹²³I-iomazenil SPECT. These abnormal findings resolved on repeated ¹²³I-iomazenil SPECT 1 month after seizure onset. The case we present here is consistent with the idea that the central benzodiazepine receptor system in the human brain undergoes changes that are related to seizures due to epilepsy.

Normobaric hyperoxia markedly reduces brain damage and sensorimotor deficits following brief focal ischaemia

'True' transient ischaemic attacks are characterized not only clinically, but also radiologically by a lack of corresponding changes on magnetic resonance imaging. During a transient ischaemic attack it is assumed that the affected tissue is penumbral but rescued by early spontaneous reperfusion. There is, however, evidence from rodent studies that even brief focal ischaemia not resulting in tissue infarction can cause extensive selective neuronal loss associated with long-lasting sensorimotor impairment but normal magnetic resonance imaging. Selective neuronal loss might therefore contribute to the increasingly recognized cognitive impairment occurring in patients with transient ischaemic attacks. It is therefore relevant to consider treatments to reduce brain damage occurring with transient ischaemic attacks. As penumbral neurons are threatened by markedly constrained oxygen delivery, improving the latter by increasing arterial O2 content would seem logical. Despite only small increases in arterial O2 content, normobaric oxygen therapy experimentally induces significant increases in penumbral O2 pressure and by such may maintain the penumbra alive until reperfusion. Nevertheless, the effects of normobaric oxygen therapy on infarct volume in rodent models have been conflicting, although duration of occlusion appeared an important factor. Likewise, in the single randomized trial published to date, early-administered normobaric oxygen therapy had no significant effect on clinical outcome despite reduced diffusion-weighted imaging lesion growth during therapy. Here we tested the hypothesis that normobaric oxygen therapy prevents both selective neuronal loss and sensorimotor deficits in a rodent model mimicking true transient ischaemic attack. Normobaric oxygen therapy was applied from the onset and until completion of 15 min distal middle cerebral artery occlusion in spontaneously hypertensive rats, a strain representative of the transient ischaemic attack-prone population. Whereas normoxic controls showed normal magnetic resonance imaging but extensive cortical selective neuronal loss associated with microglial activation (present both at Day 14 in vivo and at Day 28 post-mortem) and marked and long-lasting sensorimotor deficits, normobaric oxygen therapy completely prevented sensorimotor deficit (P < 0.02) and near-completely Day 28 selective neuronal loss (P < 0.005). Microglial activation was substantially reduced at Day 14 and completely prevented at Day 28 (P = 0.002). Our findings document that normobaric oxygen therapy administered during ischaemia nearly completely prevents the neuronal death, microglial inflammation and sensorimotor impairment that characterize this rodent true transient ischaemic attack model. Taken together with the available literature, normobaric oxygen therapy appears a promising therapy for short-lasting ischaemia, and is attractive clinically as it could be started at home in at-risk patients or in the ambulance in subjects suspected of transient ischaemic attack/early stroke. It may also be a straightforward adjunct to reperfusion therapies, and help prevent subtle brain damage potentially contributing to long-term cognitive and sensorimotor impairment in at-risk populations.

Criteria of the efficacy of surgical brain revascularization in patients with chronic cerebral ischemia

PURPOSE

The article analyzes results of surgical revascularization in patients with symptoms of chronic cerebral ischemia caused by occlusion of the carotid arteries.

MATERIAL AND METHODS

We analyzed 404 surgeries for placement of extra-intracranial microvascular anastomoses (EICMAs) performed in 376 patients between 2000 and 2015. All patients underwent detailed neurological and neuropsychological examinations before surgery and throughout the follow-up period using the neurological deficit scale (NIHSS). Additionally, the medical history data, technical features of surgery, and results of instrumental tests were recorded. For a more detailed study of the cerebral circulation, a SCT perfusion examination was conducted in 58 patients before and after placement of EICMA.

RESULTS

All patients were divided into 3 groups, depending on the surgical treatment outcomes: improvement (53%), without significant changes (43%), and worsening of clinical symptoms (4%). A statistical analysis revealed that the efficacy of EICMA surgery ranged from 22 to 79% and was reliably confirmed by hemodynamic and anamnestic factors as well as by technical details of surgery.

CONCLUSION

When determining the indications for surgical revascularization in patients with ischemic stroke consequences, the patient's age, occlusion duration, location and size of ischemic lesions should be considered. Also, the choice of the acceptor artery and blood flow through the created anastomosis are of great importance.

[Perfusion criteria of the EICMA efficacy in patients with symptomatic occlusion of the internal carotid artery]

AIM

To investigate changes in cerebral perfusion in patients with unilateral internal carotid artery occlusion before and after surgical revascularization of the brain, depending on the clinical efficacy of surgical treatment.

MATERIAL AND METHODS

The study included 60 patients with unilateral ICA occlusions who underwent placement of an extra-intracranial microvascular anastomosis (EICMA). All patients underwent a CT perfusion study before and after cerebral revascularization. In addition, the degree of neurological deficit was evaluated before surgery and during follow-up (3 and 8-10 months) using the NIHSS score.

RESULTS

All patients were divided into 3 groups, depending on the results of surgical treatment: objective improvement (43 patients), no changes (14 patients), and worsening of clinical symptoms (3 patients). In each group, the absolute and relative perfusion parameters (MTT, CBV, and CBF) were analyzed to identify the perfusion criteria for the EICMA efficacy. A significant relationship between the clinical efficacy of EICMA and a baseline perfusion deficit and its change after anastomosis placement was found.

CONCLUSION

Placement of EICMA is effective treatment for patients with symptomatic ICA occlusions and an increase in the blood transit time in the hemisphere ipsilateral to occlusion by more than 40% compared to that in the opposite side provided that perfusion is recovered in more than one area of the MCA territory (in accordance with the ASPECTS scale).

Hypoxic viable tissue in human chronic cerebral ischemia because of unilateral major cerebral artery steno-occlusive disease

BACKGROUND AND PURPOSE

Positron emission tomography (PET) with radiolabeled 2-nitroimidazoles directly detects hypoxic but viable tissue present in an acute ischemic area in the human brain. This study using PET with 1-(2-(18)F-fluoro-1-[hydroxymethyl]ethoxy) methyl-2-nitroimidazole ((18)F-FRP170) aimed to determine whether tissue with an abnormally elevated uptake of (18)F-FRP170 exists in human chronic cerebral ischemia because of unilateral atherosclerotic major cerebral artery steno-occlusive disease.

METHODS

(18)F-FRP170 PET was performed, and cerebral blood flow and metabolism were assessed using (15)O-gas PET in 20 healthy subjects and 52 patients. A region of interest (ROI) was automatically placed in 3 segments of the middle cerebral artery territory in both cerebral hemispheres with a 3-dimensional stereotaxic ROI template using SPM2, and each PET value was determined in each ROI. The ratio of values in the affected versus contralateral hemispheres was calculated for the (18)F-FRP170 PET image.

RESULTS

A significant correlation was observed between oxygen extraction fraction and (18)F-FRP170 ratios (ρ=0.509; P<0.0001) in a total of 156 ROIs in 52 patients. The specificity and positive-predictive value for a combination of an elevated oxygen extraction fraction and a moderately reduced cerebral oxygen metabolism for detection of an abnormally elevated (18)F-FRP170 ratio (19 ROIs: 12%) were significantly greater than those for the individual categories (elevated oxygen extraction fraction, moderately reduced cerebral oxygen metabolism, or reduced cerebral blood flow).

CONCLUSIONS

Tissues with abnormally elevated uptake of (18)F-FRP170 exist in human chronic cerebral ischemia characterized by a combination of misery perfusion and moderately reduced oxygen metabolism because of unilateral atherosclerotic major cerebral artery steno-occlusive disease.

Does preoperative measurement of cerebral blood flow with acetazolamide challenge in addition to preoperative measurement of cerebral blood flow at the resting state increase the predictive accuracy of development of cerebral hyperperfusion after carotid endarterectomy? Results from 500 cases with brain perfusion single-photon emission computed tomography study

The purpose of the present study was to determine whether preoperative measurement of cerebral blood flow (CBF) with acetazolamide in addition to preoperative measurement of CBF at the resting state increases the predictive accuracy of development of cerebral hyperperfusion after carotid endarterectomy (CEA). CBF at the resting state and cerebrovascular reactivity (CVR) to acetazolamide were quantitatively assessed using N-isopropyl-p-[¹²³I]-iodoamphetamine (IMP)-autoradiography method with single-photon emission computed tomography (SPECT) before CEA in 500 patients with ipsilateral internal carotid artery stenosis (≥ 70%). CBF measurement using ¹²³I-IMP SPECT was also performed immediately and 3 days after CEA. A region of interest (ROI) was automatically placed in the middle cerebral artery territory in the affected cerebral hemisphere using a three-dimensional stereotactic ROI template. Preoperative decreases in CBF at the resting state [95% confidence intervals (CIs), 0.855 to 0.967; P = 0.0023] and preoperative decreases in CVR to acetazolamide (95% CIs, 0.844 to 0.912; P < 0.0001) were significant independent predictors of post-CEA hyperperfusion. The area under the receiver operating characteristic curve for prediction of the development of post-CEA hyperperfusion was significantly greater for CVR to acetazolamide than for CBF at the resting state (difference between areas, 0.173; P < 0.0001). Sensitivity, specificity, and positive- and negative-predictive values for the prediction of the development of post-CEA hyperperfusion were significantly greater for CVR to acetazolamide than for CBF at the resting state (P < 0.05, respectively). The present study demonstrated that preoperative measurement of CBF with acetazolamide in addition to preoperative measurement of CBF at the resting state increases the predictive accuracy of the development of post-CEA hyperperfusion.

Paradoxical reduction of cerebral blood flow after acetazolamide loading: a hemodynamic and metabolic study with (15)O PET

Paradoxical reduction of cerebral blood flow (CBF) after administration of the vasodilator acetazolamide is the most severe stage of cerebrovascular reactivity failure and is often associated with an increased oxygen extraction fraction (OEF). In this study, we aimed to reveal the mechanism underlying this phenomenon by focusing on the ratio of CBF to cerebral blood volume (CBV) as a marker of regional cerebral perfusion pressure (CPP). In 37 patients with unilateral internal carotid or middle cerebral arterial (MCA) steno-occlusive disease and 8 normal controls, the baseline CBF (CBF(b)), CBV, OEF, cerebral oxygen metabolic rate (CMRO2), and CBF after acetazolamide loading in the anterior and posterior MCA territories were measured by (15)O positron emission tomography. Paradoxical CBF reduction was found in 28 of 74 regions (18 of 37 patients) in the ipsilateral hemisphere. High CBF(b) (> 47.6 mL/100 mL/min, n = 7) was associated with normal CBF(b)/CBV, increased CBV, decreased OEF, and normal CMRO2. Low CBF(b) (< 31.8 mL/100 mL/min, n = 9) was associated with decreased CBF(b)/CBV, increased CBV, increased OEF, and decreased CMRO2. These findings demonstrated that paradoxical CBF reduction is not always associated with reduction of CPP, but partly includes high-CBF(b) regions with normal CPP, which has not been described in previous studies.

Combination of blood flow asymmetry in the cerebral and cerebellar hemispheres on brain perfusion SPECT predicts 5-year outcome in patients with symptomatic unilateral major cerebral artery occlusion

BACKGROUND AND OBJECTIVE

Misery perfusion increases the risk of stroke recurrence in patients with symptomatic major cerebral artery occlusion. The ratio of brain perfusion contralateral-to-affected asymmetry in the cerebellar hemisphere to brain perfusion affected-to-contralateral asymmetry in the cerebral hemisphere (CblPR/CbrPR) indicates affected-to-contralateral asymmetry of oxygen extraction fraction (OEF) in the cerebral hemisphere. The purpose of the present study was to determine whether the CblPR/CbrPR on brain perfusion single-photon emission computed tomography (SPECT) predicts 5-year outcomes in patients with symptomatic unilateral occlusion of the middle cerebral artery (MCA) or internal carotid artery (ICA).

METHODS

Brain perfusion was assessed using N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) SPECT in 70 patients. A region of interest (ROI) was manually placed in the bilateral MCA territories and in the bilateral cerebellar hemispheres, and the CblPR/CbrPR was calculated. All patients were prospectively followed for 5 years. The primary end points were stroke recurrence or death.

RESULTS

A total of 17 patients exhibited the primary end points, 11 of whom experienced subsequent ipsilateral strokes. Multivariate analysis revealed that only high CblPR/CbrPR was significantly associated with the development of the primary end point or subsequent ipsilateral strokes (95% confidential limits [CIs], 1.130-3.145; P  =  0.0114 or 95% CIs, 2.558-5.140; P  =  0.0045, respectively). The CblPR/CbrPR provided 65% (11/17) or 91% (10/11) sensitivity and 88% (47/53) or 88% (52/59) specificity in predicting the primary end point or subsequent ipsilateral strokes, respectively.

CONCLUSIONS

The CblPR/CbrPR on brain perfusion SPECT predicts 5-year outcomes in patients with symptomatic unilateral occlusion of the MCA or ICA.

Selective neuronal loss in ischemic stroke and cerebrovascular disease

As a sequel of brain ischemia, selective neuronal loss (SNL)-as opposed to pannecrosis (i.e. infarction)-is attracting growing interest, particularly because it is now detectable in vivo. In acute stroke, SNL may affect the salvaged penumbra and hamper functional recovery following reperfusion. Rodent occlusion models can generate SNL predominantly in the striatum or cortex, showing that it can affect behavior for weeks despite normal magnetic resonance imaging. In humans, SNL in the salvaged penumbra has been documented in vivo mainly using positron emission tomography and (11)C-flumazenil, a neuronal tracer validated against immunohistochemistry in rodent stroke models. Cortical SNL has also been documented using this approach in chronic carotid disease in association with misery perfusion and behavioral deficits, suggesting that it can result from chronic or unstable hemodynamic compromise. Given these consequences, SNL may constitute a novel therapeutic target. Selective neuronal loss may also develop at sites remote from infarcts, representing secondary 'exofocal' phenomena akin to degeneration, potentially related to poststroke behavioral or mood impairments again amenable to therapy. Further work should aim to better characterize the time course, behavioral consequences-including the impact on neurological recovery and contribution to vascular cognitive impairment-association with possible causal processes such as microglial activation, and preventability of SNL.

Flexible, transparent, and noncytotoxic graphene electric field stimulator for effective cerebral blood volume enhancement

Enhancing cerebral blood volume (CBV) of a targeted area without causing side effects is a primary strategy for treating cerebral hypoperfusion. Here, we report a new nonpharmaceutical and nonvascular surgical method to increase CBV. A flexible, transparent, and skin-like biocompatible graphene electrical field stimulator was placed directly onto the cortical brain, and a noncontact electric field was applied at a specific local blood vessel. Effective CBV increases in the blood vessels of mouse brains were directly observed from in vivo optical recordings of intrinsic signal imaging. The CBV was significantly increased in arteries of the stimulated area, but neither tissue damage nor unnecessary neuronal activation was observed. No transient hypoxia was observed. This technique provides a new method to treat cerebral blood circulation deficiencies at local vessels and can be applied to brain regeneration and rehabilitation.

Cortical thickness is associated with gait disturbances in cerebral small vessel disease

Although gait disturbances are present in a substantial portion of patients with cerebral small vessel disease (SVD), their pathogenesis has not been clarified as they are not entirely explained by the white matter lesions (WMLs) and lacunar infarcts. The role of cortical thickness in these patients remains largely unknown. We aimed to assess the regions of cortical thickness associated with distinct gait parameters in patients with SVD, and whether these associations were dependent on WMLs and lacunar infarcts. MRI data were obtained from 415 subjects with SVD, aged between 50 and 85 years. We assessed cortical thickness using surface-based cortical thickness analysis, and gait performance using the GAITRite system. Cortical thickness of predominantly the orbitofrontal and ventrolateral prefrontal cortex, the inferior parietal lobe, cingulate areas and visual association cortices was positively related to stride length. Thickness of the primary and supplementary motor cortices and the cingulate cortex was positively related to cadence, while thickness of the orbitofrontal and ventrolateral prefrontal cortex, anterior cingulate cortex and especially the inferior parietal lobe and superior temporal gyrus was negatively related to stride width. The associations with stride length and width were partially explained by the subcortical WMLs and lacunar infarcts. Cortical thickness may therefore be important in gait disturbances in individuals with SVD, with different cortical patterns for specific gait parameters. We suggest that cortical atrophy is part of the disease processes in patients with SVD.

Central benzodiazepine receptor binding potential and CBF images on SPECT correlate with oxygen extraction fraction images on PET in the cerebral cortex with unilateral major cerebral artery occlusive disease

Oxygen extraction fraction (OEF) is a key predictor of stroke recurrence in patients with symptomatic major cerebral arterial occlusive disease. The purpose of the present study was to compare central benzodiazepine receptor binding potential (BRBP) and cerebral blood flow (CBF) images on SPECT with OEF images on PET in patients with chronic unilateral middle cerebral artery (MCA) or internal carotid artery (ICA) occlusive disease.

METHODS

OEF, CBF, and BRBP were assessed using (15)O PET and N-isopropyl-p-(123)I-iodoamphetamine and (123)I-iomazenil SPECT, respectively, in 20 healthy subjects and in 34 patients with unilateral MCA or ICA occlusive disease. All images were transformed into the standard brain size and shape by linear and nonlinear transformation using statistical parametric mapping for anatomic standardization. A region of interest (ROI) was automatically placed according to the arterial supply using a 3-dimensional stereotactic ROI template, and the ratio of the value in the affected side to that in the contralateral side was calculated in each image.

RESULTS

Among patients with occlusive disease, a significant positive correlation was observed between PET OEF and SPECT BRBP/CBF ratios in 3 cerebral cortical regions (r = 0.851, P < 0.0001, for anterior cerebral artery [ACA] ROI; r = 0.807, P < 0.0001, for MCA ROI; and r = 0.774, P < 0.0001, for posterior cerebral artery [PCA] ROI), but there were no correlations between these 2 parameters in the basal ganglia or the cerebellum. When an abnormally elevated PET OEF ratio was defined as a value greater than the mean + 2 SDs obtained in healthy subjects, sensitivity and specificity were, respectively, 100% and 96% for the ACA ROI, 100% and 89% for the MCA ROI, and 100% and 93% for the PCA ROI for the SPECT BRBP/CBF ratio for detecting an abnormally elevated PET OEF ratio.

CONCLUSION

BRBP/CBF images on SPECT correlate with OEF images on PET in a specific clinical setting-that is, in the cerebral cortex of patients with chronic unilateral MCA or ICA occlusive disease.