Can auditory cues improve visuo-spatial neglect? Results of two pilot studies.

Although neglect is known to be a multimodal deficit, current interventions often address the visual modality only. Experimental studies, however, found that neglect patients can partially overcome their spatial inattention temporarily when being exposed to auditory cues that move towards the neglected side of space. Two pilot studies investigated the impact of dynamic auditory cueing on egocentric neglect severity in a clinical-therapeutic setting. In both studies, the patient groups received 15 sessions of intervention. Study 1, designed as double-blinded trial with a historical control group, targeted severely impaired early-acute patients who listened to music or audio books which were presented as moving dynamically from right to left. Results showed a reduction in egocentric neglect severity that persisted after therapy termination in the intervention but not in the historical control group. In study 2, based on the comparison with reported effect sizes of previous studies, dynamic meaningful auditory cues and optokinetic stimulation were combined in a computer-based training. Both studies found a significant reduction of neglect severity. Results provide evidence for the reduction of egocentric neglect severity after repetitive auditory cueing therapy in both severely and moderately impaired patients. Our promising findings should be verified thoroughly in randomized-controlled trials.

THRIVE score predicts clinical and radiological outcome after endovascular therapy or thrombolysis in patients with anterior circulation stroke in everyday clinical practice.

BACKGROUND AND PURPOSE: Based on the data of several trials the Totaled Health Risks in Vascular Events (THRIVE) score has been shown to predict outcome after either intravenous thrombolysis (IVT) or endovascular therapy (ET) in acute stroke patients. It is unknown whether the THRIVE score can also predict outcome in everyday clinical practice. Using our prospectively obtained stroke database the utility of the THRIVE score to predict clinical and radiological outcome in everyday clinical practice was analysed. METHODS: The relationships between THRIVE and good outcome (modified Rankin Scale ≤ 2 at discharge), poor outcome (modified Rankin Scale 5-6), in-hospital death, symptomatic intracranial haemorrhage (SICH) as well as infarct size were examined in patients with distal intracranial carotid artery, M1 and M2 occlusions after either IVT or ET. RESULTS: From January 2008 to October 2016 a total of 546 patients were treated with IVT and 492 patients received ET with stent retrievers (with or without IVT). In both treatment groups the THRIVE score predicted clinical outcome (Mantel-Haenszel chi-squared tests for trend P < 0.001 for good outcome, P < 0.001 for poor outcome and P < 0.001 for in-hospital death). In the ET group the THRIVE score remained an independent predictor of outcome after controlling for recanalization. The THRIVE score was associated with the infarct size after IVT or ET, whereas it did not predict SICH rates in either treatment group. CONCLUSIONS: In everyday clinical practice the THRIVE score strongly predicts clinical outcome and the extent of ischaemia after ET or IVT in patients with anterior circulation large vessel occlusions.

[Online survey of the organizational structures of emergency neurology in Germany]. / Onlineumfrage zur Struktur der Notfallneurologie in Deutschland 2016.

In 2007, the first poll among neurologists provided some insight into the organizational structures of emergency neurology in Germany. Given that emergency neurology as well as emergency medicine in general have undergone substantial changes during the last decade, the subcommittee Neurological Emergency Medicine of the German Neurological Society conducted a follow-up study to explore current structures supporting neurological emergency medicine in German neurological hospitals. Between July and September 2016, an online questionnaire was e­mailed to 675 neurologists in institutions participating in in-patient neurological care. Of these, some 32% (university hospitals 49%) answered. Neurological patients represent 12-16% and hence a significant proportion of emergency patients. The fraction of in-patients admitted to hospitals via emergency departments amounted to 78% (median) in general hospitals and 52% in university hospitals. Most emergency departments are organized as an interdisciplinary structure combining conservative with surgical disciplines frequently led by an independent department head. Neurology departments employ rather diverse strategies to organize neurological emergency care. Also, the way emergency patients are assigned to different disciplines varied largely. Currently, neurological patients represent a rather growing fraction of patients in emergency departments. An increasing proportion of neurology in-patients enter the hospital via emergency departments. Neurology departments in Germany face increasing challenges to cope with large numbers of neurological emergency patients. While most of the participating neurologists indicated suffering predominantly from scarce personal resources both in neurology and neuroradiology, an independent neurological emergency department was not considered an option.

On the relation between self-reported cognitive fatigue and the posterior hypothalamic-brainstem network.

BACKGROUND AND PURPOSE: Various causes have been suggested for multiple sclerosis (MS) related fatigue. Hypothalamus-brainstem fibres play a role in sleep-wake regulation and in hypothalamic deactivation during inflammatory states. Hence, they may play a role for experiencing fatigue by changing bottom-up hypothalamic activation. METHODS: Multiple sclerosis patients with and without self-reported cognitive fatigue and healthy controls were analysed with respect to the integrity of hypothalamus-brainstem fibres using diffusion-tensor imaging based tractography, focusing on the anterior, medial and posterior hypothalamic areas, controlling for clinical impairment and excluding participants with depressive mood. RESULTS: Multiple sclerosis patients without self-reported cognitive fatigue showed increased axial and radial diffusivity levels specifically for fibres connecting the right posterior hypothalamus with the right locus coeruleus, but not for the medial hypothalamus and the corpus callosum. Moreover, there were no differences between MS patients with and without fatigue in brain atrophy and lesion load, which could explain our results. CONCLUSION: Multiple sclerosis patients not experiencing fatigue show increased axial and radial diffusivity for fibres connecting the posterior hypothalamus and the brainstem, which might prevent bottom-up activation of the posterior hypothalamus and therefore downregulation of structures responsible for wakefulness and exploratory states of mind.

Impact of ASPECTS on computed tomography angiography source images on outcome after thrombolysis or endovascular therapy in large vessel occlusions.

BACKGROUND AND PURPOSE: Endovascular therapy (ET) is superior to intravenous thrombolysis (IVT) in selected patients with anterior circulation large vessel occlusions. However, it is unclear if this positive effect also applies to patients with extensive early ischaemic changes. The aim of this study was to analyze the impact of the Alberta Stroke Program Early Computed Tomography Score (ASPECTS) on the CT angiography source images (SI) on outcome after ET or IVT. METHODS: Using our prospectively obtained stroke database and the admission SI-ASPECTS divided into three groups (0-5, 6-7 and 8-10), primarily the rates of good outcome [modified Rankin Scale (mRS) ≤2 at discharge] after either ET (n = 255) or IVT (n = 479) were compared. RESULTS: A favorable SI-ASPECTS (8-10) was present in 501 patients, 132 patients had a moderately favorable SI-ASPECTS (6-7) and 101 patients had an unfavorable SI-ASPECTS (0-5). Irrespective of the treatment modality, no patient with an unfavorable SI-ASPECTS had a good outcome and 38% died during hospital stay. Whilst significantly more patients with a favorable SI-ASPECTS had a good outcome after ET than after IVT (51% vs. 35%, P < 0.01), there was only a non-significant trend towards a good outcome after ET than after IVT in patients with a moderately favorable ASPECTS (25% vs. 14%, P = 0.1). CONCLUSION: Patients with extensive early ischaemic changes on CT scans (SI- ASPECTS ≤5) might not profit from ET. The impact of ET on outcome in patients with moderately favorable SI-ASPECTS should be addressed in further trials.

The influence of clinical characteristics on prism adaptation training in visuospatial neglect: A post-hoc analysis of a randomized controlled trial.

Previous studies indicate that the effect of prism adaptation training (PAT) on unilateral neglect may depend on clinical characteristics. In this explorative work, we re-analyzed data from a previously conducted randomized controlled trial (N = 23) to investigate whether age, etiology, severity of motor impairments, and visual field deficits affect the efficacy of PAT. Additionally, we reviewed PAT studies that reported lesion maps and distinguished responders from non-responders. We transferred these maps into a common standard brain and added data from 12 patients from our study. We found patients suffering from subarachnoid bleeding appeared to show stronger functional recovery than those with intracranial hemorrhage or cortical infarction. Furthermore, patients with visual field deficits and those with more severe contralateral motor impairments had larger after-effect sizes but did not differ in treatment effects. In addition, patients with parietal lesions showed reduced recovery, whereas patients with lesions in the basal ganglia recovered better. We conclude that PAT (in its current form) is effective when fronto-subcortical areas are involved but it may not be the best choice when parietal regions are affected. Overall, the present work adds to the understanding on the effects of clinical characteristics on PAT.

Hyperdense Artery Sign in Patients With Acute Ischemic Stroke-Automated Detection With Artificial Intelligence-Driven Software.

Background: Hyperdense artery sign (HAS) on non-contrast CT (NCCT) can indicate a large vessel occlusion (LVO) in patients with acute ischemic stroke. HAS detection belongs to routine reporting in patients with acute stroke and can help to identify patients in whom LVO is not initially suspected. We sought to evaluate automated HAS detection by commercial software and compared its performance to that of trained physicians against a reference standard. Methods: Non-contrast CT scans from 154 patients with and without LVO proven by CT angiography (CTA) were independently rated for HAS by two blinded neuroradiologists and an AI-driven algorithm (Brainomix®). Sensitivity and specificity were analyzed for the clinicians and the software. As a secondary analysis, the clot length was automatically calculated by the software and compared with the length manually outlined on CTA images as the reference standard. Results: Among 154 patients, 84 (54.5%) had CTA-proven LVO. HAS on the correct side was detected with a sensitivity and specificity of 0.77 (CI:0.66-0.85) and 0.87 (0.77-0.94), 0.8 (0.69-0.88) and 0.97 (0.89-0.99), and 0.93 (0.84-0.97) and 0.71 (0.59-0.81) by the software and readers 1 and 2, respectively. The automated estimation of the thrombus length was in moderate agreement with the CTA-based reference standard [intraclass correlation coefficient (ICC) 0.73]. Conclusion: Automated detection of HAS and estimation of thrombus length on NCCT by the tested software is feasible with a sensitivity and specificity comparable to that of trained neuroradiologists.

Hemorrhagic complications after systemic thrombolysis in acute stroke patients with abnormal baseline coagulation.

BACKGROUND AND PURPOSE: As patients with abnormal baseline coagulation were excluded from the large randomized trials, the safety of intravenous thrombolysis after ischaemic stroke in this patient population remains controversial. METHODS: We assessed the risk of symptomatic intracerebral hemorrhage (SICH) after systemic thrombolysis in patients with elevated baseline international normalized ratios (INRs) (≥1.3) or activated partial thromboplastin times (aPTT) (>37 s) using a prospectively recorded database from 2006 to 2010. An intracerebral hemorrhage leading to a deterioration of ≥4 points on the National Institutes of Health Stroke scale (NIHSS) was classified as symptomatic. RESULTS: Amongst 688 patients (mean age, 72 years; median NIHSS, 11, median onset-to-treatment time, 135 min), 36 patients (5%) had an abnormal baseline coagulation. Twenty-nine of these patients had taken oral anticoagulants leading to elevated baseline INRs (median INR: 1.5; IQR 1.4-1.9), whereas seven patients had elevated aPTTs because of heparin therapy (n = 2), a coagulation disorder (n = 2), or for unknown reasons (n = 3). The rate of SICH did not differ significantly between patients with abnormal and normal baseline coagulation (4.4% vs. 0%; P = 0.6). Moreover, the in-hospital mortality was not significantly different between both treatment groups (8.3% in patients with abnormal baseline coagulation vs. 8.7% in patients with normal baseline coagulation, P = 1.0). CONCLUSIONS: The risk of SICH following intravenous thrombolysis after ischaemic stroke does not appear to be increased in patients with abnormal baseline coagulation.

Risk of symptomatic intracerebral hemorrhage in patients treated with intra-arterial thrombolysis.

BACKGROUND: In intra-arterial (IA) thrombolysis trials, higher rates of symptomatic intracerebral haemorrhage (sICH) were found than in trials with intravenous (IV) recombinant tissue plasminogen activator (tPA); this observation could have been due to the inclusion of more severely affected patients in IA thrombolysis trials. In the present study, we investigated the rate of sICH in IA and combined IV + IA thrombolysis versus IV thrombolysis after adjusting for differences in clinical and MRI parameters. METHODS: In this multicenter study, we systematically analyzed data from 645 patients with anterior-circulation strokes treated with either IV or IA thrombolysis within 6 h following symptom onset. Thrombolytic regimens included (1) IV tPA treatment (n = 536) and (2) IA treatment with either tPA or urokinase (n = 74) or (3) combined IV + IA treatment with either tPA or urokinase (n = 35). RESULTS: 44 (6.8%) patients developed sICH. sICH patients had significantly higher scores on the National Institutes of Health Stroke Scale (NIHSS) at admission and pretreatment DWI lesions. The sICH risk was 5.2% (n = 28) in IV thrombolysis, which is significantly lower than in IA (12.5%, n = 9) or IV + IA thrombolysis (20%, n = 7). In a binary logistic regression analysis including age, NIHSS score, time to thrombolysis, initial diffusion weighted imaging lesion size, mode of thrombolytic treatment and thrombolytic agent, the mode of thrombolytic treatment remained an independent predictor for sICH. The odds ratio for IA or IV + IA versus IV treatment was 3.466 (1.19-10.01, 95% CI, p < 0.05). CONCLUSION: In this series, IA and IV + IA thrombolysis is associated with an increased sICH risk as compared to IV thrombolysis, and this risk is independent of differences in baseline parameters such as age, initial NIHSS score or pretreatment lesion size.

The contribution of white and gray matter differences to developmental dyslexia: insights from DTI and VBM at 3.0 T.

Developmental dyslexia is one of the most common neuropsychological disorders in children and adults. Only few data are available on the pathomechanisms of this specific dysfunction, assuming--among others--that dyslexia might be a disconnection syndrome of anterior and posterior brain regions involved in phonological and orthographic aspects of the reading process, as well as in the integration of phonemes and graphemes. Therefore, diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) were used to verify the hypothesis of altered white and gray matter structure in German dyslexic adults. DTI revealed decreased fractional anisotropy (FA) in bilateral fronto-temporal and left temporo-parietal white matter regions (inferior and superior longitudinal fasciculus). Significant correlations between white matter anisotropy and speed of pseudoword reading were found. In dyslexics, gray matter volumes (as measured by VBM) were reduced in the superior temporal gyrus of both hemispheres. So far, our results, based on a combined analysis of white and gray matter abnormalities, provide exceedingly strong evidence for a disconnection syndrome or dysfunction of cortical areas relevant for reading and spelling. Thus, we suggest that this imbalance of neuronal communication between the respective brain areas might be the crucial point for the development of dyslexia.

Early treatment after a symptomatic event is not associated with an increased risk of stroke in patients undergoing carotid stenting.

A recently symptomatic carotid artery stenosis carries a high risk of subsequent ischaemic events and thus requires rapid treatment. We investigated the influence of the time delay between the last symptomatic event of a carotid stenosis and subsequent carotid artery stenting (CAS) with respect to the combined 30-day outcome of stroke and death. In a group of 320 patients undergoing CAS the median delay before the intervention was 19 days (interquartile range 10-36) and the combined 30-day complication rate was 8.4%. Time delay was not significantly associated with peri-procedural complications, regardless of whether this variable was dichotomized (<14 days and > or =14 days), separated into interquartile ranges or analysed as a continuous variable. Our results indicate that early CAS is not associated with an increased complication rate in patients with a recently symptomatic carotid stenosis. Thus, if CAS has been selected as the treatment modality for a patient, it should be performed as soon as possible to maximize the benefit of the intervention in reducing the risk of stroke.

Aortic calcification on plain chest radiography predicts embolic complications during carotid artery stenting.

BACKGROUND AND PURPOSE: Aortic arch calcification (AC) on conventional angiograms has recently been shown to be associated with embolic complications during carotid artery stenting (CAS). Because conventional angiography is not routinely carried out in patients prior to CAS, a less invasive, commonly available diagnostic modality is warranted to identify AC. METHODS: We investigated the occurrence of AC on routinely acquired chest radiographs and its influence on diffusion-weighted imaging (DWI) lesions as surrogate markers for stroke. RESULTS: A total of 152 patients (mean age: 67.5 +/- 8.9 years, 112 men) underwent CAS and completed pre- and post-procedural DWI. AC larger than 1 cm in length was classified as relevant and could be detected in 63 patients (41.4%) on plain chest radiographs. In patients with AC, significantly more new DWI-lesions were found than in patients without AC [median 2; interquartile range (IQR): 0-7 vs. median 1, IQR: 0-2; P < 0.05]. After multivariate regression analysis, AC was independently associated with new post-procedural DWI lesions. DISCUSSION: AC is a common finding in patients with a high-grade carotid stenosis and predicts embolic complications during CAS. Since AC can be detected on plain chest radiography, this diagnostic tool is useful to identify high-risk patients for CAS.

Preprocedural C-reactive protein levels predict stroke and death in patients undergoing carotid stenting.

BACKGROUND AND PURPOSE: Elevated baseline levels of C-reactive protein (CRP) are associated with an adverse outcome during coronary stent placement. The aim of this study was to evaluate whether preprocedural CRP levels also are predictive of stroke and death in patients undergoing carotid stent placement (CAS). MATERIALS AND METHODS: We reviewed data prospectively collected from 130 patients (97 men, 33 women; mean age, 68.5 +/- 10.1 years; range, 43-89 years) who underwent CAS for symptomatic carotid stenosis and from whom preprocedural CRP values had been obtained. A CRP value of >5 mg/L was considered to be elevated. The frequency of stroke and death within 30 days was compared between patients with and without elevated baseline CRP levels using chi(2) and multivariate logistic regression analysis. RESULTS: Baseline CRP values were normal in 94 (72.3%) patients but were elevated in 36 (27.7%) patients. The demographic and clinical characteristics were similar in both treatment groups. The 30-day stroke and death rate was significantly higher in patients with elevated CRP values (8/36; 22.2%) than in those without (3/94; 3.2%; P < .01). After adjusting for demographic characteristics, degree of carotid stenosis, and use of cerebral protection devices and/or statin therapy, an elevated CRP value before CAS remained a significant and independent predictor of stroke and death within 30 days after CAS (odds ratio, 7.7; 95% confidence interval: 1.8-32.8, P = .006). CONCLUSIONS: Baseline CRP is a powerful predictor of outcome in patients undergoing CAS, which underscores the role of inflammation in the pathogenesis of embolic complications during this procedure.

Effects of physiological aging and cerebrovascular risk factors on the hemodynamic response to brain activation: a functional transcranial Doppler study.

The influence of the vascular system on the coupling of cerebral blood flow (CBF) to focal brain activation during aging is incompletely understood. Using functional transcranial Doppler sonography and a hypercapnic challenge as a marker of intact cerebral vasoreactivity, we determined CBF velocity (CBFV) changes in response to a language and arithmetic task in a group of 43 healthy young subjects (mean age 32 +/- 8.6 years), 18 healthy old subjects (mean age 64 +/- 9.8 years) and 29 old subjects with risk factors for an atherosclerosis (mean age 69 +/- 8.4 years). Despite a similar performance during the cognitive tasks the CBFV changes were significantly lower in the group of old subjects with vascular risk factors compared with the healthy young and old subjects. Similarly, the CBFV changes during hypercapnia were significantly lower in the group of old subjects with vascular risk factors compared with the healthy young and old subjects. In contrast, both cognitive tasks and hypercapnia produced comparable CBFV changes in the group of healthy young and old subjects. These results suggest that the hemodynamic response to neuronal activation is unaffected by aging alone, whereas the presence of cardiovascular risk factors significantly diminishes the capability of cerebral vessels to react to vasodilating stimuli.

Carotid endarterectomy versus carotid stenting: an updated review of randomized trials and subgroup analyses.

Atherosclerotic disease of the carotid arteries is responsible for a significant portion of ischemic strokes. Carotid endarterectomy (CEA) is currently the accepted standard of treatment for patients with severe symptomatic carotid stenosis. In the past few years, however, carotid angioplasty and stenting (CAS) has emerged as a potential alternative endovascular treatment strategy for this disorder. In fact, spurred by the positive results of single center studies and small, pivotal randomized trials, some even consider CAS as the treatment modality of choice, especially in presumably surgical high-risk patients. Yet, randomized trials directly comparing CAS with CEA are sparse and have produced conflicting results. The aim of this article is to review the current trial data on this issue and to define the role of these techniques for the management of two important subgroups of patients. An updated meta-analysis of seven randomized trials comparing CEA with CAS demonstrates that CAS is associated with a significantly increased risk of any stroke or death within 30 days (OR. 1.41, 95% CI 1.07-1.87, p < 0.05). Focusing on patients with a symptomatic carotid stenosis, there was also a significant difference in the odds of treatment-related stroke and death between CAS and CEA (OR, 1.41 ; CI 1.05 to 1.88, p < 0.05). Data on all disabling strokes and deaths within 30 days was available from five trials. The odds of disabling stroke or death at 30 days were similar in the endovascular and surgical group (OR, 1.33, 95% CI 0.89 to 1.98). Overall, these data do not justify a blind enthusiasm for CAS and a widespread use of this procedure for the treatment of carotid artery stenosis. On the other hand, a closer inspection of the current literature on elderly patients and those with a contralateral carotid occlusion clearly indicates that CAS and CEA already now have a complementary role. While elderly patients should preferentially be treated with CEA, CAS appears to be the treatment of choice in patients with a symptomatic carotid artery stenosis and a contralateral carotid occlusion in experienced centers.

99mTc annexin V imaging of neonatal hypoxic brain injury.

BACKGROUND AND PURPOSE: Delayed cell loss in neonates after cerebral hypoxic-ischemic injury (HII) is believed to be a major cause of cerebral palsy. In this study, we used radiolabeled annexin V, a marker of delayed cell loss (apoptosis), to image neonatal rabbits suffering from HII. METHODS: Twenty-two neonatal New Zealand White rabbits had ligation of the right common carotid artery with reduction of inspired oxygen concentration to induce HII. Experimental animals (n=17) were exposed to hypoxia until an ipsilateral hemispheric decrease in the average diffusion coefficient occurred. After reversal of hypoxia and normalization of average diffusion coefficient values, experimental animals were injected with (99m)Tc annexin V. Radionuclide images were recorded 2 hours later. RESULTS: Experimental animals showed no MR evidence of blood-brain barrier breakdown or perfusion abnormalities after hypoxia. Annexin images demonstrated multifocal brain uptake in both hemispheres of experimental but not control animals. Histology of the brains from experimental animals demonstrated scattered pyknotic cortical and hippocampal neurons with cytoplasmic vacuolization of glial cells without evidence of apoptotic nuclei by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining. Double staining with markers of cell type and exogenous annexin V revealed that annexin V was localized in the cytoplasm of scattered neurons and astrocytes in experimental and, less commonly, control brains in the presence of an intact blood-brain barrier. CONCLUSIONS: Apoptosis may develop after HII even in brains that appear normal on diffusion-weighted and perfusion MR. These data suggest a role of radiolabeled annexin V screening of neonates at risk for the development of cerebral palsy.

High speed diffusion magnetic resonance imaging of ischemia and spontaneous periinfarct spreading depression after thromboembolic stroke in the rat.

Spontaneous episodes of transient cell membrane depolarization (spreading depression [SD]) occur in the surroundings of experimental stroke lesions and are believed to contribute to infarct growth. Diffusion-weighted imaging (DWI) is capable of detecting the water shifts from extracellular to intracellular space associated with SD waves and ischemia, and can make in vivo measurements of these two features on a pixel-by-pixel basis with good temporal resolution. Using continuous high speed DWI with a temporal resolution of 12 seconds over a period of 3 hours, the in vivo contribution of spontaneous SDs to the development of ischemic tissue injury was examined in 8 rats using a thromboembolic stroke model. During the observation period, the initial lesion volume increased in 4 animals, remained unchanged in 1 animal, and decreased in 3 animals (most likely because of spontaneous clot lysis). Irrespective of the lesion evolution patterns, animals demonstrated 6.5 +/- 2.1 spontaneous SDs outside of the ischemic core. A time-to-peak analysis of apparent diffusion coefficient (ADC) changes for each SD wave demonstrated multidirectional propagation patterns from variable initiation sites. Maps of the time constants of ADC recovery, reflecting the local energy supply and cerebral blood flow, revealed prolonged recovery times in areas close to the ischemic core. However, repetitive SD episodes in the periinfarct tissue did not eventually lead to permanent ADC reductions. These results suggest that spontaneous SD waves do not necessarily contribute to the expansion of the ischemic lesion volume in this model.

Gender differences in cerebral blood flow and oxygenation response during focal physiologic neural activity.

Using functional magnetic resonance imaging techniques CBF and oxygenation changes were measured during sustained checkerboard stimulation in 38 right-handed healthy volunteers (18 men and 20 women). The average blood oxygenation level dependent (BOLD) contrast technique signal intensity change was 1.67 +/- 0.6% in the group of male volunteers and 2.15 +/- 0.6% in the group of female volunteers (P < .05). Baseline regional CBF (rCBF) values in activated gray matter areas within the visual cortex were 57 +/- 10 mL x 100 g(-1) x min(-1) in women and 50 +/- 12 mL x 100 g(-1) x min(-1) in men, respectively (P = .09). Despite a broad overlap between both groups the rCBF increase was significantly higher in women compared to men (33 +/- 5 mL x 100 g(-1) x min(-1) versus 28 +/- 4 mL x 100 g(-1) x min(-1), P < .01). The increase of rCBF was not correlated with the baseline rCBF (mL x 100 g(-1) x min(-1)) (r(s) = 0.01, P = .9). Moreover, changes of rCBF were not correlated with changes in BOLD signal intensities (r(s) = 0.1, P = .7). Enhanced rCBF response in women during visual stimulation could be related to gender differences in visual physiology or may reflect gender differences in the vascular response to focal neuronal activation. Gender differences must be considered when interpreting the results of functional magnetic resonance imaging studies.

Simultaneous monitoring of dynamic changes in cerebral blood flow and oxygenation during sustained activation of the human visual cortex.

Functional neuroimaging was used to investigate the effect of cerebral blood flow (CBF) adjustments on the blood oxygenation level dependent (BOLD) signal during visual stimulation. Temporal responses from both oxygenation- and perfusion-sensitized MRI revealed almost identical features during onset and ongoing activation, i.e. an activation-induced signal rise, and a gradual signal decrease during prolonged activation (overshoot). However, the post-stimulus responses exhibited a pronounced BOLD signal drop below prestimulus baseline (undershoot), but a rather rapid normalisation of the related CBF signal. Thus, an activation-induced initial BOLD signal rise and a gradual signal decrease reflect a coarse upregulation of CBF, which is followed by fine-tuning adjustments of flow. Regulations of other involved physiological parameters, including blood volume and oxidative metabolism give rise to a negative post-stimulus BOLD signal response.