Acute subarachnoid hemorrhage: MR imaging with fluid-attenuated inversion recovery pulse sequences

Reversible sulcal fluid-attenuated inversion recovery hyperintensity after combined bypass surgery for moyamoya disease - A "crevasse" sign

Background

Transient fluid-attenuated inversion recovery (FLAIR) hyperintensity is often observed on the operated brain surface after direct or combined bypass surgery for moyamoya disease, but its pathophysiology and clinical significance are still obscure. This study was aimed to clarify the underlying mechanism and clinical significance.

Methods

This prospective study included 106 hemispheres of 61 patients with moyamoya disease and analyzed their radiological findings before and after combined bypass surgery. This study also included 11 patients who underwent superficial temporal artery to middle cerebral artery anastomosis for occlusive carotid artery diseases as the controls. Magnetic resonance imaging examination was serially repeated, and cerebral blood flow was measured before and after surgery. Signal intensity ratio (SIR) in the cortical sulci and cortex to the adjacent white matter on FLAIR images was calculated, and the postoperative SIR changes were semi-quantitatively evaluated to assess the temporal profile of postoperative FLAIR hyperintensity.

Results

Postoperative FLAIR hyperintensity occurred within the cortical sulci on the operated hemispheres in all moyamoya patients but not in patients with occlusive carotid artery diseases. SIR values started to increase immediately after surgery, peaked at about 4-fold at 4-13 days post-surgery, then declined, and recovered to baseline values over 28 days or later. The magnitude of this phenomenon was proportional to the severity of cerebral ischemia but not to postoperative hyperperfusion.

Conclusion

Reversible sulcal FLAIR hyperintensity specifically occurs in the operated hemispheres after direct bypass surgery for moyamoya disease. This "crevasse sign" may represent the mixture of the extensive leakage of oxygen and proteins from the pial arteries into the CSF.

Spontaneous Non-Aneurysmal Convexity Subarachnoid Hemorrhage: A Scoping Review of Different Etiologies beyond Cerebral Amyloid Angiopathy

Spontaneous convexity subarachnoid hemorrhage (cSAH) is a vascular disease different from aneurysmal SAH in neuroimaging pattern, causes, and prognosis. Several causes might be considered in individual patients, with a limited value of the patient's age for discriminating among these causes. Cerebral amyloid angiopathy (CAA) is the most prevalent cause in people > 60 years, but reversible cerebral vasoconstriction syndrome (RCVS) has to be considered in young people. CAA gained attention in the last years, but the most known manifestation of cSAH in this context is constituted by transient focal neurological episodes (TFNEs). CAA might have an inflammatory side (CAA-related inflammation), whose diagnosis is relevant due to the efficacy of immunosuppression in resolving essudation. Other causes are hemodynamic stenosis or occlusion in extracranial and intracranial arteries, infective endocarditis (with or without intracranial infectious aneurysms), primary central nervous system angiitis, cerebral venous thrombosis, and rarer diseases. The diagnostic work-up is fundamental for an etiological diagnosis and includes neuroimaging techniques, nuclear medicine techniques, and lumbar puncture. The correct diagnosis is the first step for choosing the most effective and appropriate treatment.

Imaging of pediatric brain tumors: A COG Diagnostic Imaging Committee/SPR Oncology Committee/ASPNR White Paper

Tumors of the central nervous system are the most common solid malignancies in children and the most common cause of pediatric cancer-related mortality. Imaging plays a central role in diagnosis, staging, treatment planning, and response assessment of pediatric brain tumors. However, the substantial variability in brain tumor imaging protocols across institutions leads to variability in patient risk stratification and treatment decisions, and complicates comparisons of clinical trial results. This White Paper provides consensus-based imaging recommendations for evaluating pediatric patients with primary brain tumors. The proposed brain magnetic resonance imaging protocol recommendations balance advancements in imaging techniques with the practicality of deployment across most imaging centers.

Two Similar Cases of a Misdiagnosed Anterior Communicating Aneurysm Rupture

The misdiagnosis of a ruptured aneurysm directly endangers patient's life and health due to the high risk of rebleeding and its sequelae. In this paper, we present two uncommon cases of anterior communicating artery aneurysm rupture with a relatively small intracerebral bleeding, seemingly without a diffuse subarachnoid hemorrhage (SAH), and a relatively mild clinical presentation. In these cases, the initial diagnosis failed, leading to missed aneurysmal ruptures. The atypical or mild clinical presentation, and the absence of SAH on computed tomography (CT) and/or magnetic resonance imaging (MRI) scan or absent blood in the cerebrospinal fluid (CSF) are all factors which could lead to a false or delayed diagnosis. Meticulous evaluation of patient's symptoms, CT, MRI scans, and CSF findings are mandatory. The possibility of a small blood clot without a diffuse SAH must be considered.

Evaluation of cortical superficial siderosis in patients with cognitive dysfunction using 3D FLAIR and 3D DIR

OBJECTIVES

Our aim was to evaluate the detectability of cortical superficial siderosis (cSS) by 3D FLAIR and 3D DIR images in comparison with the SWI images in patients with cognitive dysfunction.

METHODS

We studied 246 patients with cognitive dysfunction (144 women, 102 men; mean age: 75.5 ± 7.53 years) who visited a memory clinic at our hospital and underwent MR examinations at 3 T. Specifically, 16 patients with Alzheimer disease (AD) (n = 11) and AD with cerebrovascular disease (n = 5) manifested cSS based on SWI. Each set of MR images (3D FLAIR and 3D DIR) was reviewed by two reviewers separately for the detection of sulcal hyperintensity that suggested cSS.

RESULTS

SWI detected a greater number of cSS sulci than 3D DIR and 3D FLAIR. The sensitivity and specificity for the detection of sulcal hyperintensity were the same between 3D FLAIR and 3D DIR (87.5%/100%). However, 3D DIR detected a greater number of cSS sulci than 3D FLAIR (p = .005).

CONCLUSIONS

Our study showed that 3D DIR and 3D FLAIR can detect sulcal hyperintensity related to cSS although they are less sensitive to cSS lesions than SWI.

KEY POINTS

• 3D FLAIR and 3D DIR can show sulcal signal abnormalities related to cSS in patients with cognitive dysfunction. • 3D FLAIR and 3D DIR detect sulcal hyperintensity of cSS, although they are less sensitive to cSS than SWI. • Signal alterations due to cSS are more detectable in 3D DIR than in 3D FLAIR.

Magnetic Resonance Imaging in Aneurysmal Subarachnoid Hemorrhage: Current Evidence and Future Directions

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) is associated with an unacceptably high mortality and chronic disability in survivors, underscoring a need to validate new approaches for treatment and prognosis. The use of advanced imaging, magnetic resonance imaging (MRI) in particular, could help address this gap given its versatile capacity to quantitatively evaluate and map changes in brain anatomy, physiology and functional activation. Yet there is uncertainty about the real value of brain MRI in the clinical setting of aSAH.

METHODS

In this review, we discuss current and emerging MRI research in aSAH. PubMed was searched from inception to June 2017, and additional studies were then chosen on the basis of relevance to the topics covered in this review.

RESULTS

Available studies suggest that brain MRI is a feasible, safe, and valuable testing modality. MRI detects brain abnormalities associated with neurologic examination, outcomes, and aneurysm treatment and thus has the potential to increase knowledge of aSAH pathophysiology as well as to guide management and outcome prediction. Newer pulse sequences have the potential to reveal structural and physiological changes that could also improve management of aSAH.

CONCLUSION

Research is needed to confirm the value of MRI-based biomarkers in clinical practice and as endpoints in clinical trials, with the goal of improving outcome for patients with aSAH.

Common and Uncommon Artifacts in T1 FLAIR SAG Sequences of MRI Brain

OBJECTIVE

This study aims at identifying, classifying, and measuring the frequency the different artifacts that show up in the images of the Sagittal T1 Fluid Attenuated Inversion Recovery (FLAIR) sequence.

MATERIALS AND METHODS

A total of 101 subjects underwent brain magnetic resonance imaging examination with the following sequences: Axial T1 FLAIR, Axial T2-weighted imaging, Diffusion Weighted Imaging, 2D Multiple Echo Recombined Gradient Echo, Sagittal T1 FLAIR, Coronal T2 Turbo Spin Echo, Spin Echo T1-weighted imaging, and 3D Fast Spoiled Gradient-echo. In these images, we observed the following categories of artifacts: (a) ghost artifacts, (b) aliasing behind the occipital bone, (c) aliasing inside the sphenoid cavity, (d) susceptibility artifacts, and (e) pulsation artifacts. In order to recognize and verify the artifacts, we used not only the Sagittal T1 FLAIR sequence, but also Sagittal reconstructions from the 3-dimensional Fast Spoiled Gradient-echo sequence and the other routine sequences.

RESULTS

Aliasing artifacts and especially aliasing of nose are present in 41% of the cases. In 45% of these cases the uncommon aliasing artifacts, which took place into the brain parenchyma (sphenoid cavity, subarachnoid bay, or pituitary) originated from nose. In 33% of the subjects, ghost artifacts are presented, which stem from the nose, the orbits, or other pulsating structures (pulsation artifacts) or even from fat tissue. Moreover, susceptibility artifacts comprise 8% of all the artifacts. Finally, 19% of brains were presented without artifact.

CONCLUSIONS

We suggest in addition to T1 FLAIR, the application of Sagittal SE or TSE sequences in magnetic resonance imaging examination of brain, trying to include the nose in the square of FOV.

Clinical Significance of the CSF Pulsation Flow Sign in the Foramen of Monro on FLAIR in Patients with Aneurysmal SAH -Preliminary Report

It is known that the cerebrospinal fluid (CSF) pulsation flow sign in the lateral ventricles directly above the foramen of Monro (CPF-M) on axial fluid attenuated inversion recovery (FLAIR) is a normal physiological finding as an artifact of FLAIR. In this study, whether CPF-M can be used as a neuroradiological finding related to pathological conditions in patients with acute aneurysmal subarachnoid hemorrhage (aSAH) was investigated. CPF-M-related clinical features were retrospectively evaluated in 147 aSAH patients who underwent adequate serial MRI examinations without massive intraventricular hemorrhage (IVH) of the lateral ventricle within 48 h of ictus. The frequency of the CPF-M in the control group was 32% (57/178), 33% (40/123), and 38% (45/117) for the normal control, chronic cerebral infarction, and deep white matter lesion (WML) groups, respectively. In aSAH patients, the overall prevalence of the CPF-M was 57% (84/147), significantly higher than in the three control groups. Multivariate analysis showed that age <70 years, lower IVH Hijdra score of the fourth ventricle, absence of T₁-FLAIR mismatch, deep WMLs, old infarction, diffuse brain swelling, symptomatic delayed cerebral ischemia (DCI), shunt-dependent chronic hydrocephalus (SDCH), and favorable outcome were significantly associated with the CPF-M. Although limited to SAH patients without massive IVH of the lateral ventricles, one can conclude that, in acute aSAH, the presence of CPF-M on admission MRI suggests that the circulatory dynamics of the CSF from the basal cistern to the ventricles are approximately normal. Thus, this finding may appear to offer an indicator of a good outcome without DCI and SDCH.

Pseudo-Subarachnoid Hemorrhage; Chronic Subdural Hematoma with an Unruptured Aneurysm Mistaken for Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) usually occurs due to aneurysmal rupture of intracranial arteries and its typical computed tomography (CT) findings are increased attenuation of cisterns and subarachnoid spaces. However, several CT findings mimicking SAH are feasible in diverse conditions. They are so-called as pseudo-SAH, and this report is a case of pseudo-SAH which is misdiagnosed as aneurysm rupture accompanied by bilateral chronic subdural hematoma (cSDH). A 42-year-old male with severe headache visited our institute. Non-contrast brain CT images showed increased attenuation on basal cistern, and cSDH on both fronto-temporo-parietal convexity with midline shifting. Trans-femoral cerebral angiography was done and we confirmed small aneurysm at right M1 portion of middle cerebral artery. Under diagnosis of SAH, we planned an operation in order to clip aneurysmal neck and remove cSDH. cSDH was removed as planned, however, there was no SAH and we also couldn't find the rupture point of aneurysm. Serial follow-up CT showed mild cumulative cSDH recurrence, but the patient was tolerant and had no neurologic deficit during hospitalization. We have checked the patient via out-patient department for 6 months, there are no significant changes in volume and density of cSDH and the patient also have no neurologic complications.

MRI quality assurance based on 3D FLAIR brain images

OBJECTIVE

Quality assurance (QA) of magnetic resonance imaging (MRI) often relies on imaging phantoms with suitable structures and uniform regions. However, the connection between phantom measurements and actual clinical image quality is ambiguous. Thus, it is desirable to measure objective image quality directly from clinical images.

MATERIALS AND METHODS

In this work, four measurements suitable for clinical image QA were presented: image resolution, contrast-to-noise ratio, quality index and bias index. The methods were applied to a large cohort of clinical 3D FLAIR volumes over a test period of 9.5 months. The results were compared with phantom QA. Additionally, the effect of patient movement on the presented measures was studied.

RESULTS

A connection between the presented clinical QA methods and scanner performance was observed: the values reacted to MRI equipment breakdowns that occurred during the study period. No apparent correlation with phantom QA results was found. The patient movement was found to have a significant effect on the resolution and contrast-to-noise ratio values.

DISCUSSION

QA based on clinical images provides a direct method for following MRI scanner performance. The methods could be used to detect problems, and potentially reduce scanner downtime. Furthermore, with the presented methodologies comparisons could be made between different sequences and imaging settings. In the future, an online QA system could recognize insufficient image quality and suggest an immediate re-scan.

3D double inversion recovery MR imaging: Clinical applications and usefulness in a wide spectrum of central nervous system diseases

Double inversion recovery (DIR) imaging provides two inversion pulses that attenuate signals from cerebrospinal fluid and normal white matter. This review was undertaken to describe the principle of the DIR sequence, the clinical applications of 3D DIR in various central nervous system diseases and the clinical benefits of the 3D DIR compared with those of other MR sequences. 3D DIR imaging provides better lesion conspicuity and topography than other MR techniques. It is particularly useful for diagnosing the following disease entities: cortical and subcortical abnormalities such as multiple sclerosis, cortical microinfarcts and cortical development anomalies; sulcal abnormalities such as meningitis and subacute/chronic subarachnoid hemorrhage; and optic neuritis caused by multiple sclerosis or neuromyelitis optica.

Imaging of Intracranial Hemorrhage

Intracranial hemorrhage is common and is caused by diverse pathology, including trauma, hypertension, cerebral amyloid angiopathy, hemorrhagic conversion of ischemic infarction, cerebral aneurysms, cerebral arteriovenous malformations, dural arteriovenous fistula, vasculitis, and venous sinus thrombosis, among other causes. Neuroimaging is essential for the treating physician to identify the cause of hemorrhage and to understand the location and severity of hemorrhage, the risk of impending cerebral injury, and to guide often emergent patient treatment. We review CT and MRI evaluation of intracranial hemorrhage with the goal of providing a broad overview of the diverse causes and varied appearances of intracranial hemorrhage.

FLAIR signal increase of the fluid within the resection cavity after glioma surgery: generally valid as early recurrence marker?

OBJECTIVE Recent studies have indicated that a signal intensity increase of the fluid within the resection cavity on FLAIR images may predict tumor recurrence after glioma surgery. The aim of this study was to assess the increase in FLAIR signal intensity in a large patient cohort and in subgroups to assess its prognostic value for early tumor recurrence in glioma patients. METHODS A total of 212 patients (213 cases) who had undergone surgery for an intracranial glioma (WHO Grade IV [n = 103], WHO Grade III [n = 57], and WHO Grade II [n = 53]) were included in this retrospective study. FLAIR signal within the resection cavity at the time of tumor recurrence/last contact and on the previous MRI study was assessed qualitatively and quantitatively. Appearance of FLAIR signal increase was studied over time using Kaplan-Meier estimates in subgroups. RESULTS Patients with WHO Grade II glioma and connection of the resection cavity to CSF who did not undergo radiotherapy did not regularly develop this sign and were excluded from further analysis. For the remaining 87 cases, FLAIR signal intensity increase was observed in 27 cases. Recurrent disease was found in 26 of these 27 cases, resulting in a specificity of 80.0%, a sensitivity of 31.7%, and positive and negative predictive values of 96.3% and 6.7%, respectively. In 4 cases this sign had been observed prior (range 2.8-8.5 months) to tumor recurrence defined by standard criteria. Quantitative analysis underlined the results of qualitative analysis, but it did not add a diagnostic value. CONCLUSIONS Signal intensity increase of the fluid within the resection cavity on FLAIR images is a rare but highly specific and early sign for tumor recurrence/tumor progression in completely and incompletely resected high-grade glioma without connection of the resection cavity to CSF and with radiotherapy.

Diagnosis of a subarachnoid hemorrhage with only mild symptoms using computed tomography in Japan

Background

Japan is currently an aging society, with a huge proportion of elderly citizens. Consequently, the incidence and severity of subarachnoid hemorrhage (SAH) is predicted to increase in the future. Computed tomography (CT) is very important in the initial diagnosis of SAH. The proportion of hospitals owning CT systems in Japan is around four times greater than the mean number of systems owned by hospitals in other countries belonging to the Organisation for Economic Co-operation and Development. Because CT is readily available in Japan, it follows that this technique, with its impressive diagnostic power, might be more in demand in Japan compared to other countries. However, misdiagnosis of SAH is a relatively common problem and is associated with increased mortality and morbidity, even in individuals who initially present in good condition.

Case presentation

We describe a patient with subtle clinical and CT signs of SAH. A 39-year-old Japanese man visited our hospital with a 3-day history of mild headache, shoulder stiffness, and a feeling of dizziness. His physical examination was normal aside from mild neck stiffness. Although CT did not reveal obvious abnormalities, we noticed subtle signs of SAH on CT images, which have been observed in SAH patients with mild symptoms. Thus, we diagnosed our patient with SAH and provided appropriate treatment (aneurysm clipping). Following this, the patient progressed without development of the initial complications, and he was subsequently discharged from our hospital without sequela.

Conclusion

Thus, physicians should be able to recognize subtle characteristics of CT imaging in case of SAH patients with low grade symptoms, as this can facilitate early diagnosis.

Turbo-FLAIR Sequence in Brain MRI

To compare a turbo-FLAIR sequence with Proton Density (PD) and T2-weighted Turbo Spin-Echo (TSE) sequences in several different brain diseases, 276 MRI examinations were performed on a 1.0 Tesla system.

The positive cases were assessed for lesion detection and lesion conspicuity. Four quantitative criteria were also used to compare the contrast of the two techniques: lesion to background contrast, lesion to background contrast to noise ratio (CNR), lesion to Cerobrospinal fluid (CSF) contrast, lesion to CSF contrast to noise ratio.

The turbo FLAIR sequence was found to be superior to PD and T2-weighted TSE for lesion detection: this sequence detected more lesions in 74 patients than PD and in 42 patients than T2, but missed some subtentorial lesions. For lesion conspicuity turbo-FLAIR was judged equivalent to PD and T2-weighted TSE respectively in 27% and 45% of the cases and better in 71% and 53% of the cases. Lesion to background contrast and lesion to background CNR were found to be significantly greater for turbo-FLAIR than for PD (p<0.001). Compared with T2-weighted TSE, turbo-FLAIR showed a significantly higher lesion to background contrast (p<0.001) and inferior lesion to background CNR (p<0.001).

Our study indicates that turbo-FLAIR can replace PD TSE scans in most cases and can be used as a first choice sequence for cerebrovascular diseases, multiple sclerosis and for the evaluation of gliosis.

Acute Headache and Subarachnoid Haemorrhage: A Retrospective Review of CT and Lumbar Puncture Findings

Aim: Assess and correlate the clinical presentation, cranial CT and lumbar puncture (LP) findings in patients presenting with acute headache, clinically suspicious of subarachnoid haemorrhage, from the Accident and Emergency (A/E) department of a main teaching hospital. Method: We retrospectively reviewed over a 1-year period all patients referred for cranial CT from the A/E department, with clinically suspected nontraumatic SAH. Patients with a negative CT, with a diagnosis of SAH on LP, had their initial CT examination reassessed in a double blind review. Results: 116 consecutive patients were included in the study. Patients were divided into 3 groups post CT results: diagnostic of SAH (19), abnormal without evidence of SAH (16) and normal (81). The clinical management of the latter group was analysed with particular emphasis on the performance and results of lumbar puncture (LP). 81 patients, clinically suspicious of SAH in our study had a normal cranial CT and were eligible for LP. 49% had an LP, which was positive in 13% and contributed 24% to the total number diagnosed with SAH. LP was not performed in 51% of eligible patients. Conclusion: This study reviews the varying clinical presentations of SAH and the difficulty in clinically diagnosing SAH where headache is the only symptom. We review the wide differential diagnosis on cranial CT and on discharge of patients presenting with symptoms clinically suspicious of SAH. In addition this study identifies a high proportion of patients without detailed clinical notes and discharged without a diagnosis. The study reaffirms that a significant proportion of patients are diagnosed on LP and stress the importance of performing a LP in all cases with clinically suspected SAH with a negative CT. This latter point requires highlighting in the medical literature as over half of eligible patients did not have a LP performed despite this being accepted diagnostic protocol.

Imaging of Traumatic Brain Injury

Imaging plays an important role in the management of patients with traumatic brain injury (TBI). Computed tomography (CT) is the first-line imaging technique allowing rapid detection of primary structural brain lesions that require surgical intervention. CT also detects various deleterious secondary insults allowing early medical and surgical management. Serial imaging is critical to identifying secondary injuries. MR imaging is indicated in patients with acute TBI when CT fails to explain neurologic findings. However, MR imaging is superior in patients with subacute and chronic TBI and also predicts neurocognitive outcome.

Misleading FLAIR imaging pattern after glioma surgery with intraoperative MRI

Intraoperative MRI (iMRI) allows a more detailed appreciation of the extent of resection than does conventional neurosurgery and results in longer overall survival in patients with malignant glioma. However, it is unknown whether the intraoperative application of contrast agent influences the early postsurgical MRI. The preceding iMRI could alter the signals of MR sequences in the early postsurgical MRI, especially in sequences influenced by T1 contrast. Hereby, we investigate such iMRI-induced influences on the fluid-attenuated inversion recovery (FLAIR) sequence. We retrospectively analyzed postsurgical T2w, T1w, and FLAIR images by visual inspection and by signal measurements in 46 patients with malignant gliomas after tumor resection. Of these, n = 25 patients were operated with conventional microsurgery, and n = 21 patients were operated with contrast-enhanced iMRI-guided microsurgery. We measured signal intensity in the resection cavity, in the cerebrospinal fluid (CSF) of the ventricles, and in the normal brain tissue contralateral to the tumor-bearing hemisphere on axial FLAIR images and T1-weighted and T2-weighted images. In 18 patients, the FLAIR sequence revealed hyperintense signal changes of the CSF in the subarachnoid or ventricular spaces. Seventeen of these 18 patients had received intraoperative MRI. In both FLAIR and T1-weighted images, the signal of the CSF in the ventricles was significantly higher in patients with iMRI than in patients without iMRI. The intraoperative application of contrast agent that is used for iMRI significantly influences postsurgical MRI within the first 72 h. We found hyperintense signal changes of the CSF in the FLAIR sequence in the subarachnoid and intraventricular spaces mimicking subarachnoid hemorrhage. The findings may result in a misdiagnosis of subarachnoid hemorrhage (SAH) in these patients.

Detection of aneurysmal subarachnoid hemorrhage 3 months after initial bleeding: evaluation of T2* and FLAIR MR sequences at 3 T in comparison with initial non-enhanced CT as a gold standard

OBJECTIVE

To investigate the ability of T2* and fluid-attenuated inversion recovery (FLAIR) MR sequences to detect hemosiderin deposition 3 months after aneurysmal subarachnoid hemorrhage (SAH) in comparison with early non-enhanced CT (NECT) as a gold standard.

MATERIALS AND METHODS

From September 2008 through May 2013, patients with aneurysmal SAH were included if a NECT less than 24 h after the onset of symptoms showed a SAH, and MRI, including T2* and FLAIR sequences, was performed 3 months later. All aneurysms were treated endovascularly. NECT and MR sequences were blindly analyzed for the presence of SAH (NECT) or hemosiderin deposition (MRI). When positive, details of the spatial distribution of SAH or hemosiderin deposits were noted. Sensitivities were calculated for each patient. Sensitivities, specificities, and positive predictive values (PPVs) were calculated for each location.

RESULTS

Forty-nine patients (mean age 52.9 years) were included. Bleeding-related patterns were identified in 43 patients (87.8%) on T2* and 10 patients (20.4%) on FLAIR. T2* was highly predictive of the location of the initial hemorrhage, especially in the Sylvian cisterns (PPVs 95% and 100%) and the anterior interhemispheric fissure (PPV 90%).

CONCLUSIONS

The T2* sequence can detect and localize a previous SAH a few months after aneurysmal bleeding.

Revisiting neuroimaging of abusive head trauma in infants and young children

OBJECTIVE

The purpose of this article is to use a mechanism-based approach to review the neuroimaging findings of abusive head trauma to infants. Advanced neuroimaging provides insights into not only the underlying mechanisms of craniocerebral injuries but also the long-term prognosis of brain injury for children on whom these injuries have been inflicted.

CONCLUSION

Knowledge of the traumatic mechanisms, the key neuroimaging findings, and the implications of functional imaging findings should help radiologists characterize the underlying causes of the injuries inflicted, thereby facilitating effective treatment.

Novel Magnetic Resonance Imaging Techniques in Brain Tumors

Magnetic resonance imaging is a powerful, noninvasive imaging technique with exquisite sensitivity to soft tissue composition. Magnetic resonance imaging is primary tool for brain tumor diagnosis, evaluation of drug response assessment, and clinical monitoring of the patient during the course of their disease. The flexibility of magnetic resonance imaging pulse sequence design allows for a variety of image contrasts to be acquired, including information about magnetic resonance-specific tissue characteristics, molecular dynamics, microstructural organization, vascular composition, and biochemical status. The current review highlights recent advancements and novel approaches in MR characterization of brain tumors.

Assessment of sedated pediatric brain with 3D-FLAIR sequence at 3T MRI

BACKGROUND AND PURPOSE

In sedated pediatric brains, 2D-FLAIR causes increased signal intensity of the cerebrospinal fluid (CSF) leading to false-positive diagnoses. Our aim is to determine whether increased CSF signal intensity is observed on 3D-FLAIR images.

METHODS

In this institutional review board-approved study, a 2-year retrospective analysis of our MRI database was conducted which revealed 48 sedated pediatric patients with normal cranial MRI findings and 3D-FLAIR sequence. One adult volunteer was imaged before and after O2 inhalation with 2D and 3D-FLAIR sequences. The hyperintensity in the subarachnoid spaces and basal cisterns were quantified as follows: 0: artifact free; 1: homogeneous minimal CSF signal; 2: abnormal CSF signal. Inter-observer agreement was assessed with kappa agreement analysis.

RESULTS

Grade 0 and grade 1 signals were observed at inferior to Liliequist membrane (LLQ) in 48/48 and 0/48 cases; prepontine cistern 47/48 and 1/48; superior to LLQ 26/48 and 22/48; 4th ventricle 16/48 and 32/48; 3rd ventricle 34/48 and 14/48; lateral ventricle 3/48 and 45/48; subarachnoid space 36/48 and 12/48, respectively. No patients showed grade 2 signal. Inter-observer agreement was 0.81-1. In the volunteer, after O2 inhalation, grade 2 signal intensity was evident on 2D-FLAIR however; 3D-FLAIR did not show any signal increase.

CONCLUSIONS

In sedated pediatric brains, 3D-FLAIR suppresses CSF signal, and enables reliable assessment free from CSF artifacts.

Double inversion recovery MR sequence for the detection of subacute subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The diagnosis of subacute subarachnoid hemorrhage is important because rebleeding may occur with subsequent life-threatening hemorrhage. Our aim was to determine the sensitivity of the 3D double inversion recovery sequence compared with CT, 2D and 3D FLAIR, 2D T2*, and 3D SWI sequences for the detection of subacute SAH.

MATERIALS AND METHODS

This prospective study included 25 patients with a CT-proved acute SAH. Brain imaging was repeated between days 14 and 16 (mean, 14.75 days) after clinical onset and included MR imaging (2D and 3D FLAIR, 2D T2*, SWI, and 3D double inversion recovery) after CT (median delay, 3 hours; range, 2-5 hours). A control group of 20 healthy volunteers was used for comparison. MR images and CT scans were analyzed independently in a randomized order by 3 blinded readers. For each subject, the presence or absence of hemorrhage was assessed in 4 subarachnoid areas (basal cisterns, Sylvian fissures, interhemispheric fissure, and convexity) and in brain ventricles. The diagnosis of subacute SAH was defined by the presence of at least 1 subarachnoid area with hemorrhage.

RESULTS

For the diagnosis of subacute SAH, the double inversion recovery sequence had a higher sensitivity compared with CT (P < .001), 2D FLAIR (P = .005), T2* (P = .02), SWI, and 3D FLAIR (P = .03) sequences. Hemorrhage was present for all patients in the interhemispheric fissure on double inversion recovery images, while no signal abnormality was noted in healthy volunteers. Interobserver agreement was excellent with double inversion recovery.

CONCLUSIONS

Our study showed that the double inversion recovery sequence has a higher sensitivity for the detection of subacute SAH than CT, 2D or 3D FLAIR, 2D T2*, and SWI.

Headaches caused by vascular disorders

The clinical association between stroke and headache is complex, ranging from the largely irrelevant to the highly specific. The incidence and clinical relevance of acute headache are highly dependent on stroke subtype and etiology. In this article the issue of headache accompanying acute stroke is addressed in some detail.

T2 FLAIR artifacts at 3-T brain magnetic resonance imaging

The purpose of this retrospective clinical study was to identify and evaluate the presence and frequency of T2 FLAIR artifacts on brain MRI studies performed at 3 T. We reviewed axial T2 FLAIR images in 200 consecutive unremarkable brain MRI studies performed at 3 T. All studies were reviewed for the presence of artifacts caused by pulsatile CSF flow, magnetic susceptibility and no nulling of the CSF signal. T2 FLAIR images introduce several artifacts that may degrade image quality and mimic pathology. Knowledge of these artifacts and increased severity and frequency at 3 T is of particular importance in avoiding a misdiagnosis.

Detecting subarachnoid hemorrhage: comparison of combined FLAIR/SWI versus CT

OBJECTIVES

Aim of this study was to compare the utility of susceptibility weighted imaging (SWI) with the established diagnostic techniques CT and fluid attenuated inversion recovery (FLAIR) in their detecting capacity of subarachnoid hemorrhage (SAH), and further to compare the combined SWI/FLAIR MRI data with CT to evaluate whether MRI is more accurate than CT.

METHODS

Twenty-five patients with acute SAH underwent CT and MRI within 6 days after symptom onset. Underlying pathology for SAH was head trauma (n=9), ruptured aneurysm (n=6), ruptured arteriovenous malformation (n=2), and spontaneous bleeding (n=8). SWI, FLAIR, and CT data were analyzed. The anatomical distribution of SAH was subdivided into 8 subarachnoid regions with three peripheral cisterns (frontal-parietal, temporal-occipital, sylvian), two central cisterns and spaces (interhemispheric, intraventricular), and the perimesencephalic, posterior fossa, superior cerebellar cisterns.

RESULTS

SAH was detected in a total of 146 subarachnoid regions. CT identified 110 (75.3%), FLAIR 127 (87%), and SWI 129 (88.4%) involved regions. Combined FLAIR and SWI identified all 146 detectable regions (100%). FLAIR was sensitive for frontal-parietal, temporal-occipital and Sylvian cistern SAH, while SWI was particularly sensitive for interhemispheric and intraventricular hemorrhage.

CONCLUSIONS

By combining SWI and FLAIR, MRI yields a distinctly higher detection rate for SAH than CT alone, particularly due to their complementary detection characteristics in different anatomical regions. Detection strength of SWI is high in central areas, whereas FLAIR shows a better detection rate in peripheral areas.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Thunderclap headache: diagnostic considerations and neuroimaging features

Thunderclap headache (TCH) is an acute and severe headache that has maximum intensity at onset; TCH can be primary or secondary. Primary TCH is diagnosed when no underlying cause is discovered; however, imaging is crucial in distinguishing secondary causes, which are wide-ranging. The radiologist should be aware of the list of potential diagnoses. Subarachnoid haemorrhage (SAH) is the most common cause of secondary TCH. Aneurysmal SAH accounts for the majority of cases, although other causes should also be considered and these include perimesencephalic haemorrhage, arteriovenous malformations, and dural arteriovenous fistula as well as reversible cerebral vasoconstriction syndrome. Conditions that may present with TCH, with or without SAH include cervical artery dissection and cerebral venous sinus thrombosis. Ischaemic stroke, pituitary apoplexy, and posterior reversible leucoencephalopathy are other potential causes, whereas non-vascular causes include colloid cysts of the third ventricle and spontaneous intracranial hypotension. Imaging features are reviewed with reference to clues gleaned from initial imaging using computed tomography, as well as characteristics that should be sought using magnetic resonance imaging or angiographic imaging.

Pitfalls of 3D FLAIR brain imaging: a prospective comparison with 2D FLAIR

RATIONALE AND OBJECTIVES

To prospectively compare the image contrast of various brain lesions on two-dimensional (2D) and three-dimensional (3D) fluid-attenuated inversion-recovery (FLAIR) images and to highlight the pitfalls of 3D FLAIR.

MATERIALS AND METHODS

Institutional review board approval was obtained. We examined 94 brain lesions with 2D and 3D FLAIR at 3T. First, we optimized the repetition time and echo time of 3D FLAIR with a volunteer study. Then, we assessed the conspicuity and detection of the various lesions qualitatively, and the contrast ratio between the gray or white matter and lesions was calculated as a quantitative assessment. We also performed a phantom study to investigate the effects of different flow velocities on 2D and 3D FLAIR.

RESULTS

With regard to the conspicuity and detection of most lesions (multiple sclerosis, ischemic lesions or infarction, brain tumors, or chronic trauma), 3D FLAIR was equal or superior to 2D FLAIR. For these lesions, the mean contrast ratios were higher on 3D FLAIR than on 2D FLAIR images. In terms of lesion conspicuity in the patients with hippocampal sclerosis and leptomeningeal metastasis, however, 3D FLAIR was equal or inferior to 2D FLAIR. The ivy sign in patients with moyamoya disease was frequently obscured on 3D FLAIR. The phantom study demonstrated that the signal-intensity ratio on 3D FLAIR decreased more rapidly with increasing velocity than that on 2D FLAIR.

CONCLUSION

Although 3D FLAIR may replace 2D FLAIR images for most patients, radiologists should keep in mind that 3D has some pitfalls.

Diagnostic Ability of Fluid-Attenuated Inversion Recovery MR Imaging to Detect Remnant or Recurrent Meningiomas after Resection

It has been suggested that a difference in signal intensity (SI) between the resection cavity and normal cerebrospinal fluid (CSF) on fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) in partially resected gliomas indicates subsequent or coincident tumor progression. We considered that this would hold true for resected meningiomas as well. Hence, we aimed to assess whether or not such a difference in the SI during the follow-up evaluation helps predict residual or recurrent tumor in resected meningiomas. We evaluated 63 patients with resected meningiomas. The SI within the resection cavity observed on FLAIR images was qualitatively and quantitatively assessed during follow-up. Qualitative analysis comprised visual comparison of the SI in the resection cavity with that of normal CSF by neuroradiologists. The SI in the resection cavity was quantitatively assessed by region of interest (ROI) analysis and normalized against the background noise and CSF SI. Normalized SI recorded during follow-up was compared with that recorded immediately after resection. Tumor progression was defined as a 20% or greater increase in the diameter of the longest residual or recurrent meningioma (Response Evaluation Criteria in Solid Tumors). The sensitivity and specificity of the elevated SI in the resection cavity for indicating residual or recurrent tumor were calculated. Qualitative analysis by FLAIR MRI showed that patients with remnant tumor following surgery had a prolonged SI increase in the resection cavity. Further, SI increase could not always be observed before recurrence, and both SI increase and regrowth remnant/recurrence could be detected in the same MRI examination. In resected meningiomas, leakage of tumor elements into the resection cavity, presumably tumor cells, manifests as an SI increase on FLAIR images and indicates residual or recurrent tumor. However, unlike the previous reports on partially resected gliomas, we concluded that the SI change does not always precede tumor progression or recurrence.

Hyperintense vessels on flair imaging in reversible cerebral vasoconstriction syndrome

Objectives: To study the frequency and significance of distal hyperintense vessels (HVs) on fluid-attenuated inversion recovery (FLAIR) imaging in patients with reversible cerebral vasoconstriction syndrome (RCVS).

Methods: Patients with RCVS were recruited during 2002 through 2009. Prominence and location of HVs on FLAIR images during the acute and recovery stages were documented. Clinical profiles, vasoconstriction scores, mean flow velocities of the middle cerebral artery (VMCA) and posterior cerebral artery (VPCA), and the Lindegaard index (LI) were collected for analysis.

Results: Ninety-five patients with RCVS (11M/84F, mean age 47.8 ± 10.9 years) were recruited. Twenty-one (22.1%) had FLAIR HVs, which were noted at a mean of 14.3 ± 12.7 days and resolved by 44.9 ± 18.8 days. Compared with patients without HVs, patients with this finding had higher vasoconstriction scores for all arterial segments; higher VMCA (121.0 ± 39.5 cm/s vs. 93.3 ± 27.8, p = 0.002), VPCA (73.3 ± 35.0 vs. 50.5 ± 17.8 cm/s, p = 0.010), and LI (2.8 ± 1.2 vs. 1.9 ± 0.5, p = 0.018), and complications such as posterior reversible encephalopathy syndrome (PRES) [8/21 (38%) vs. 0/74 (0%), p < 0.001] or ischemic stroke [5/21 (24%) vs. 1/74 (1%), p = 0.002].

Conclusions: HVs in patients with RCVS might be attributed to the failure of cerebrospinal fluid (CSF) signal nulling on FLAIR imaging due to severe cerebral hemodynamic derangements and were associated with more frequent ischemic complications.

The unique features of traumatic brain injury in children. Review of the characteristics of the pediatric skull and brain, mechanisms of trauma, patterns of injury, complications and their imaging findings--part 1

Traumatic head/brain injury (TBI) is a leading cause of death and life-long disability in children. The biomechanical properties of the child's brain and skull, the size of the child, the age-specific activity pattern, and higher degree of brain plasticity result in a unique distribution, degree, and quality of TBI compared to adult TBI. A detailed knowledge about the various types of primary and secondary pediatric head injuries is essential to better identify and understand pediatric TBI. The goals of this review article are (1) to discuss the unique epidemiology, mechanisms, and characteristics of TBI in children, and (2) to review the anatomical and functional imaging techniques that can be used to study common and rare pediatric traumatic brain injuries and their complications.

Updated imaging of traumatic brain injury

Computed tomography (CT) and magnetic resonance (MR) play important roles in the evaluation of traumatic brain injury. Modern CT scanners allow for rapid and accurate diagnosis of intracranial hemorrhage and mass effect and allow the efficient implementation of emergent CT angiography. Newer sequences, such as gradient recalled echo, susceptibility-weighted imaging, and diffusion-weighted imaging, can provide greater sensitivity for specific types of diffuse posttraumatic brain injury. MR spectroscopy can provide additional chemical information, and diffusion tensor imaging can provide information about white matter injury. Patient treatment can be optimized using the diagnostic and prognostic information derived from current imaging techniques.

3D fluid-attenuated inversion recovery imaging: reduced CSF artifacts and enhanced sensitivity and specificity for subarachnoid hemorrhage

BACKGROUND AND PURPOSE

FLAIR images are highly sensitive for SAH. However, CSF flow artifacts caused by conventional FLAIR can produce false-positive results. Here, we compare 3D and 3D FLAIR sequences, focusing on their potential for containing these artifacts and their sensitivity and specificity for detection of SAHs.

MATERIALS AND METHODS

We evaluated the following 4 FLAIR sequences: 1) 2D FLAIR at 1.5T, 2) 2D FLAIR, 3) 2D PROPELLER-FLAIR, and 4) 3D Cube-FLAIR at 3T. All sequences were performed in 5 healthy volunteers; sequences 2 and 4 were also performed under routine conditions in 10 patients with focal epilepsy and in 10 patients with SAH. Two neuroradiologists independently conducted the analysis. The presence of flow artifacts in the ventricles and cisterns of healthy volunteers and patients with epilepsy was evaluated and scored on a 4-point scale. Mean values were calculated and compared by using paired t tests. Sensitivity and specificity for SAH detection in sequences 2 and 4 were determined.

RESULTS

Cube-FLAIR showed almost no CSF artifacts in the volunteers and the patients with epilepsy; therefore, it was superior to any other FLAIR (P < .001). Sensitivity and specificity of SAH detection by 3T FLAIR were 58.3% and 89.4%, respectively, whereas Cube-FLAIR had a sensitivity of 95% and a specificity of 100%.

CONCLUSIONS

Cube-FLAIR allows FLAIR imaging with almost no CSF artifacts and is, thus, particularly useful for SAH detection.

Phase-sensitive, dual-acquisition, single-slab, 3D, turbo-spin-echo pulse sequence for simultaneous T2-weighted and fluid-attenuated whole-brain imaging

Conventional T(2)-weighted turbo/fast spin echo imaging is clinically accepted as the most sensitive method to detect brain lesions but generates a high signal intensity of cerebrospinal fluid (CSF), yielding diagnostic ambiguity for lesions close to CSF. Fluid-attenuated inversion recovery can be an alternative, selectively eliminating CSF signals. However, a long time of inversion, which is required for CSF suppression, increases imaging time substantially and thereby limits spatial resolution. The purpose of this work is to develop a phase-sensitive, dual-acquisition, single-slab, three-dimensional, turbo/fast spin echo imaging, simultaneously achieving both conventional T(2)-weighted and fluid-attenuated inversion recovery-like high-resolution whole-brain images in a single pulse sequence, without an apparent increase of imaging time. Dual acquisition in each time of repetition is performed, wherein an in phase between CSF and brain tissues is achieved in the first acquisition, while an opposed phase, which is established by a sequence of a long refocusing pulse train with variable flip angles, a composite flip-down restore pulse train, and a short time of delay, is attained in the second acquisition. A CSF-suppressed image is then reconstructed by weighted averaging the in- and opposed-phase images. Numerical simulations and in vivo experiments are performed, demonstrating that this single pulse sequence may replace both conventional T(2)-weighted imaging and fluid-attenuated inversion recovery.

Imaging of the meninges and the extra-axial spaces

The separate meningeal layers and extraaxial spaces are complex and can only be differentiated by pathologic processes on imaging. Differentiation of the location of such processes can be achieved using different imaging modalities. In this pictorial review we address the imaging techniques, enhancement and location patterns, and disease spread that will promote accurate localization of the pathology, thus improving accuracy of diagnosis. Typical and unusual magnetic resonance (MR), computed tomography (CT), and ultrasound imaging findings of many conditions affecting these layers and spaces are described.

Primary thunderclap headache

Thunderclap headache is an uncommon type of headache, but recognition and diagnosis are important because of the possibility of a serious underlying brain disorder. In this chapter, primary thunderclap headache in relation to other primary headache disorders and secondary, symptomatic headache disorders are discussed. Most importantly, subarachnoid hemorrhage should be excluded. The first investigation is a computed tomography (CT) scan, and, if the CT scan is negative, investigation of the cerebrospinal fluid. Other symptomatic vascular causes are intracranial hemorrhage, cerebral venous sinus thrombosis, cervical artery dissection, or a reversible vasoconstriction syndrome. These and other serious underlying intracranial disorders should be detected by magnetic resonance imaging or the appropriate investigations. The remaining patients with thunderclap headache most likely represent a primary headache disorder, including migraine, primary cough headache, primary exertional headache, or primary headache associated with sexual activity. Within the group of primary headache disorders, primary thunderclap headache represents a distinct clinical entity; it is characterized by a sudden severe headache lasting from 1h up to 10 days and not attributed to another disorder. The pathogenesis of primary thunderclap headache is still not known, but the sympathetic nervous system may play an important role.