Cerebrospinal Fluid Flow and Brain Motion in Chiari I Malformation: Past, Present, and Future.

Cranio-spinal volume and pressure changes associated with the cardiac-cycle and respiration are altered in Chiari I malformation (CMI) due to obstruction of cerebrospinal fluid (CSF) flow at the foramen magnum. With the introduction of motion-sensitive MRI sequences, it was envisioned that these could provide noninvasive information about volume-pressure dynamics at the cranio-cervical junction in CMI hitherto available only through invasive pressure measurements. Since the early 1990s, multiple studies have assessed CSF flow and brain motion in CMI. However, differences in design and varied approaches in the presentation of results and conclusions makes it difficult to fully comprehend the role of MR imaging of CSF flow and brain motion in CMI. In this review, a cohesive summary of the current status of MRI assessment of CSF flow and brain motion in CMI is presented. Simplified versions of the results and conclusions of previous studies are presented by dividing the studies in distinct topics: 1) comparing CSF flow and brain motion between healthy subjects (HS) and CMI patients (before and after surgery), 2) comparing CSF flow and brain motion to CMI severity and symptoms, and 3) comparing CSF flow and brain motion in CMI with and without syringomyelia. Finally, we will discuss our vision of the future directions of MR imaging in CMI patients. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: 5.

Association between resistance to cerebrospinal fluid flow and cardiac-induced brain tissue motion for Chiari malformation type I.

PURPOSE: Chiari malformation type I (CMI) patients have been independently shown to have both increased resistance to cerebrospinal fluid (CSF) flow in the cervical spinal canal and greater cardiac-induced neural tissue motion compared to healthy controls. The goal of this paper is to determine if a relationship exists between CSF flow resistance and brain tissue motion in CMI subjects. METHODS: Computational fluid dynamics (CFD) techniques were employed to compute integrated longitudinal impedance (ILI) as a measure of unsteady resistance to CSF flow in the cervical spinal canal in thirty-two CMI subjects and eighteen healthy controls. Neural tissue motion during the cardiac cycle was assessed using displacement encoding with stimulated echoes (DENSE) magnetic resonance imaging (MRI) technique. RESULTS: The results demonstrate a positive correlation between resistance to CSF flow and the maximum displacement of the cerebellum for CMI subjects (r = 0.75, p = 6.77 × 10-10) but not for healthy controls. No correlation was found between CSF flow resistance and maximum displacement in the brainstem for CMI or healthy subjects. The magnitude of resistance to CSF flow and maximum cardiac-induced brain tissue motion were not statistically different for CMI subjects with and without the presence of five CMI symptoms: imbalance, vertigo, swallowing difficulties, nausea or vomiting, and hoarseness. CONCLUSION: This study establishes a relationship between CSF flow resistance in the cervical spinal canal and cardiac-induced brain tissue motion in the cerebellum for CMI subjects. Further research is necessary to understand the importance of resistance and brain tissue motion in the symptomatology of CMI.

The Relationship Between Imbalance Symptom and Cardiac Pulsation Induced Mechanical Strain in the Brainstem and Cerebellum for Chiari Malformation Type I.

Chiari malformation Type I (CMI) is known to have an altered biomechanical environment for the brainstem and cerebellum; however, it is unclear whether these altered biomechanics play a role in the development of CMI symptoms. We hypothesized that CMI subjects have a higher cardiac-induced strain in specific neurological tracts pertaining to balance, and postural control. We measured displacement over the cardiac cycle using displacement encoding with stimulated echoes magnetic resonance imaging in the cerebellum, brainstem, and spinal cord in 37 CMI subjects and 25 controls. Based on these measurements, we computed strain, translation, and rotation in tracts related to balance. The global strain on all tracts was small (<1%) for CMI subject and controls. Strain was found to be nearly doubled in three tracts for CMI subjects compared to controls (p < 0.03). The maximum translation and rotation were ∼150 µm and ∼1 deg, respectively and 1.5-2 times greater in CMI compared to controls in four tracts (p < 0.005). There was no significant difference between strain, translation, and rotation on the analyzed tracts in CMI subjects with imbalance compared to those without imbalance. A moderate correlation was found between cerebellar tonsillar position and strain on three tracts. The lack of statistically significant difference between strain in CMI subjects with and without imbalance could imply that the magnitude of the observed cardiac-induced strain was too small to cause substantial damage to the tissue (<1%). Activities such as coughing, or Valsalva may produce a greater strain.

Comparing the benefit of ASPECTS on maximum intensity projection images of computed tomography angiography to source images and noncontract computed tomography in predicting infarct volume and collaterals extent.

INTRODUCTION: In acute ischemic strokes (AIS), the Alberta Stroke Program Early Computed Tomography Score (ASPECTS) and CT perfusion (CTP) are commonly used to determine mechanical thrombectomy eligibility. Prior work suggests that CTA source image (CTA-SI) ASPECTS (CTAasp) and a newly described CTA maximum intensity projection (CTA-MIP) ASPECTS (MIPasp) better predict the final infarct core. Our goal was to compare MIPasp to CTAasp and non-contrast CT ASPECTS (NCCTasp) for predicting ischemic core and collaterals established by CTP. METHODS AND MATERIALS: A single institution, retrospective database for AIS due to internal carotid artery (ICA) or proximal middle cerebral artery (MCA) occlusions between January 2016 and February 2021 was reviewed. We rated ASPECTS on NCCT, CTA-SI, and CTA-MIP at baseline, then used the automated RAPID software to measure CTP ischemic core volume. The accuracy of each ASPECTS in predicting ischemic core volume (ICV) >70 cc and Hypoperfusion intensity ratio (HIR) >0.4 was compared using the receiver operating characteristic (ROC) curve. RESULTS: 122/319 patients fulfilled the inclusion criteria. Area under the curve (AUC) for MIPasp was significantly higher than NCCTasp and CTAasp for predicting ICV >70 cc (0.95 vs. 0.89 and 0.95 vs. 0.92, P =0.03 and P = 0.04). For predicting HIR >0.4, AUC for MIPasp was significantly higher than NCCTasp and CTAasp (0.85 vs. 0.72 and 0.85 vs. 0.81, P < 0.001 and P < 0.01). CONCLUSION: The predictive accuracy of detecting ischemic stroke with ICV >70cc and HIR >0.4 can be significantly improved using the MIPasp instead of CTAasp or NCCTasp.

MRI findings differentiating tonsillar herniation caused by idiopathic intracranial hypertension from Chiari I malformation.

PURPOSE: Some patients with idiopathic intracranial hypertension (IIH) have cerebellar tonsillar herniation ≥ 5 mm mimicking Chiari malformation I (CMI), which can result in misdiagnosis and unjustified treatment. Our purpose was to identify IIH patients with tonsillar herniation ≥ 5 mm (IIHTH) and compare with CMI patients to assess imaging findings that could distinguish the two conditions. METHODS: Ninety-eight patients with IIH, 81 patients with CMI, and 99 controls were retrospectively assessed. Two neuroradiologists blindly reviewed MR images. IIHTH patients were compared with CMI patients and controls regarding the extent of tonsillar herniation (ETH), bilateral transverse sinus stenosis (BTSS), hypophysis-sella ratio (HSR), and bilateral tortuosity of optic nerve (BTON). RESULTS: 13/98 (13.2%) IIH patients had tonsillar herniation ≥ 5 mm (IIHTH) and were significantly younger and had higher BMI compared with CMI patients and controls. ETH was significantly less in the IIHTH than CMI (6.5 ± 2.4 mm vs. 10.9 ± 4.4 mm; p < 0.001). BTSS and HSR < 0.5 were more common in IIHTH than CMI (p < 0.001 and p = 0.003, respectively). No differences were seen between CMI and controls. BTON was significantly more common in IIHTH compared to control (p = 0.01) but not to the CMI (p = 0.36). Sensitivity and specificity to differentiate IIHTH from CMI were 69.2% and 96.1% for BTSS and 69.2% and 75.3% for HSR < 0.5. CONCLUSION: The presence of BTSS and/or HSR < 0.5 in patients with ETH ≥ 5 mm should suggest further evaluation to exclude IIH before considering CMI surgery.

Shortened total spine MRI protocol in the detection of spinal cord compression and pathology for emergent settings: a noninferiority study.

BACKGROUND AND PURPOSE: Spinal cord compression (SCC) requires rapid diagnosis in the emergent setting; however, current MRI protocols may be cumbersome for patients and clinicians. We sought to validate an abbreviated total spine MRI (TS-MRI) protocol using standard non-contrast sequences in the detection of SCC and other clinically significant findings (OCSF). METHODS: Two hundred six TS-MRI scans obtained over a 30-month period for SCC were included. Sagittal T2 (T2sag), sagittal T1 (T1sag), and sagittal STIR (IRsag), as well as axial T2 (T2ax) images, were individually assessed independently by 2 reviewers for SCC, cauda equina compression (CEC), and OCSF. A protocol consisting of all the sequences was considered the gold standard. Sensitivity and specificity of single and combined MRI sequences for SCC/CEC and OCSF were determined and were tested for noninferiority relative to standard non-contrast sequences using a 5% noninferiority margin. RESULTS: An abbreviated protocol of IRsag + T2ax provided the best performance with sensitivity and specificity of 100% (95%CI, 96.0-100.0) and 98.6% (95%CI, 95.6-99.7) for SCC/CEC and 100.0% (95%CI, 96.7-100.0), and 99.3% (95%CI, 96.6-99.9) for OCSF. The mean difference of sensitivity and specificity between IRsag + T2ax and standard protocol was 0.0% (95%CI, 0.0-4.0) and - 2.1% (95%CI, - 5.4 to - 0.6) for SCC/CEC and 0.0% (95%CI, 0.0-3.3) and - 1.5% (95%CI, - 4.8 to - 0.3) for OCSF, all within the noninferiority margin of 5%. CONCLUSIONS: An abbreviated TS-MRI protocol of IRsag + T2ax is noninferior to the standard non-contrast protocol, potentially allowing for faster emergent imaging diagnosis and triage.

Diagnostic yield of CT angiography performed for suspected cervical artery dissection in the emergency department.

BACKGROUND AND PURPOSE: Computed tomography angiographies are frequently performed in the emergency department (ED) for the assessment of cervical artery dissection (CeAD) due to the high risk of associated morbidity, but their diagnostic utility is not fully evaluated. We assessed the radiological outcomes and clinical correlates of CTAs performed for suspected CeAD. MATERIALS AND METHODS: CTAs for all indications (IndicationALL) over a 10-year period were evaluated to identify those with CeAD. A subgroup of CTAs performed for suspected CeAD (IndicationDISSECTION) was identified and further assessed for clinical findings predictive of CeAD. Magnetic resonance angiography/fat-saturated images (MRA/FSI) performed after CTA were also assessed. RESULTS: Nine-thousand-two-hundred-four CTAs were performed by our ED for IndicationALL of which 850 (9.2%) were for IndicationDISSECTION. CeAD was noted in 1.5% (142/9204) among IndicationALL and in 6.1% (53/850) of IndicationDISSECTION CTAs. The most common radiological findings were mural thrombus and eccentric lumen. In the IndicationDISSECTION group, new headache (OR: 2.5, 95%CI: 1.2-5.7) and partial Horner syndrome (OR: 14.4, 95%CI: 4.2-49.9) predicted carotid dissection and cervical fracture (OR: 5.5, 95%CI: 2.1-14.6) predicted vertebral artery dissections. MRA/FSI confirmed CeAD in all positive cases, but in 2 CTAs read as negative, MRA/FSI was positive for vertebral artery dissection. CONCLUSION: Although the yield of CTAs for clinically suspected CeAD is low, the paucity of reliable clinical predictors, high risk of morbidity, availability in ED, and comparable performance to MRA/FSI justifies its widespread utilization for initial diagnosis of CeAD.

Association Between Resistance to Cerebrospinal Fluid Flow Near the Foramen Magnum and Cough-Associated Headache in Adult Chiari Malformation Type I.

Cough-associated headaches (CAHs) are thought to be distinctive for Chiari malformation type I (CMI) patients and have been shown to be related to the motion of cerebrospinal fluid (CSF) near the foramen magnum (FM). We used computational fluid dynamics (CFD) to compute patient-specific resistance to CSF motion in the spinal canal for CMI patients to determine its accuracy in predicting CAH. Fifty-one symptomatic CMI patients with cerebellar tonsillar position (CTP) ≥ 5 mm were included in this study. The patients were divided into two groups based on their symptoms (CAH and non-CAH) by review of the neurosurgical records. CFD was utilized to simulate CSF motion, and the integrated longitudinal impedance (ILI) was calculated for all patients. A receiver operating characteristic (ROC) curve was evaluated for its accuracy in predicting CAH. The ILI for CMI patients with CAH (776 dyn/cm5, 288-1444 dyn/cm5; median, interquartile range) was significantly larger compared to non-CAH (285 dyn/cm5, 187-450 dyn/cm5; p = 0.001). The ILI was more accurate in predicting CAH in CMI patients than the CTP when the comparison was made using the area under the ROC curve (AUC) (0.77 and 0.70, for ILI and CTP, respectively). ILI ≥ 750 dyn/cm5 had a sensitivity of 50% and a specificity of 95% in predicting CAH. ILI is a parameter that is used to assess CSF blockage in the spinal canal and can predict patients with and without CAH with greater accuracy than CTP.

Role of C-reactive protein in effective utilization of emergent MRI for spinal infections.

PURPOSE: Emergent spinal MRI is recommended for patients with back pain and red flags for infection. However, many of these studies are negative due to low prevalence of spinal infections. Our purpose was to assess if C-reactive protein (CRP) can be used to guide effective utilization of emergent MRI for spinal infections. METHODS: 316/960 (33%) MRIs performed for infection by the emergency department over 75-month period had CRP levels obtained at presentation, after excluding patients receiving antibiotic or had spinal surgery in < 1 month. An MRI was considered positive when there was imaging evidence of spinal infection confirmed on follow-up by surgery/biopsy/drainage or definitive therapy. A CRP of ≤ 10 mg/L was considered normal and > 100 mg/L as highly elevated. RESULTS: CRP was normal in 95/316 (30%) and abnormal in 221/316 (70%) patients. MRI was positive in 43/316 (13.6%) patients, all of whom had abnormal CRP. CRP (p < 0.001) and intravenous drug use (IVDU; p = 0.002) were independently associated with a positive MRI. Receiver operator characteristic (ROC) analysis showed AUC of 0.76 for CRP, slightly improving with IVDU. Sensitivity, specificity, and negative predictive values for CRP level cut-off: 10 mg/L, 100%, 35%, and 100%, and 100 mg/L, 58%, 70% and 91%, respectively. CONCLUSION: Abnormal CRP, although extremely sensitive, lacks specificity in predicting a positive MRI for spinal infection unless highly elevated. However, a normal CRP (absent recent antibiotic or surgery) makes spinal infection unlikely, and its routine use as a screening test can help reducing utilization of emergent MRI for this purpose.

Brain Computed Tomography Angiography Maximum Intensity Projection Images for ASPECTS Derivation and Detection of Large Infarct Volumes: Preliminary Study.

PURPOSE: Non-contrast CT ASPECTS (NCCTasp) has an established role in determining eligibility for mechanical thrombectomy in centers without ready access to perfusion or DWI. Moreover, it has been suggested that CTA source ASPECTS (CTAasp) may be superior to NCCTasp in predicting final infarct volume (FIV). In this study, we hypothesized that CTA maximum intensity projection ASPECTS (MIPSasp) would be superior compared to both NCCTasp and CTAasp in predicting FIV as measured by DWI. MATERIALS AND METHODS: In 41 consecutive patients with MCA territory infarcts, NCCTasp, CTAasp and MIPSasp were visually assessed by 2 neuroradiologists. Disagreements were adjudicated by a third neuroradiologist, and the reconciled data used for all further analysis. MR-DWI was used as the standard for FIV determination. Receiver operating characteristic curve analysis was used to compare the area under the curve for all three CT-based methods in predicting FIV ≥70 ml. RESULTS: MIPSasp (AUC: 0.98, CI: 0.88-1.00) were statistically better than NCCTasp (AUC: 0.87, 95% CI: 0.72-0.95; p=0.01) in predicting FIV ≥70 ml. MIPSasp were also superior to CTAasp (AUC: 0.9, CI: 0.79-.98; p˂0.05). Optimal test performance for predicting FIV ≥70 ml for MIPSasp was ≤6 (sensitivity=100%, specificity=91.4%; Youden's J=0.98). CONCLUSION: Our preliminary study suggests that a novel CTA-MIPS derived ASPECTS better predicts large MCA territory infarcts compared to CTA source and non-contrast ASPECTS. Thus, MIPSasp may be a promising technique for future studies aimed at improving ischemic stroke treatment in centers using ASPECTS for stroke management.

Clinical utility of 2-D anatomic measurements in predicting cough-associated headache in Chiari I malformation.

PURPOSE: Cough-associated headache (CAH) is the most distinctive symptom of patients with Chiari I malformation (CMI) and indicates clinically significant disease. We determined the clinical utility of simple 2D anatomic measurements performed on a PACS workstation by assessing their diagnostic accuracy in predicting CAH in CMI patients. METHODS: Seventy-two consecutive CMI patients (cerebellar tonsillar herniation > 5 mm) with headache seen by neurosurgeons over 6 years were included. Sagittal T1 images were used by two readers to measure: extent of tonsillar herniation, lengths of the clivus and supra-occiput, McRae and pB-C2 lines, as well as clivus-canal, odontoid retroversion, and skull base angles. Neurosurgery notes were reviewed to determine presence of CAH. Mann-Whitney test was used to compare measurements between patients with and without CAH. Predictive accuracy was assessed by receiver operating characteristic (ROC) curve. RESULTS: 47/72 (65.3%) CMI patients reported CAH. Tonsillar herniation with CAH (10.2 mm, 7-14 mm; median, interquartile range) was significantly greater than those without CAH (7.9 mm, 6.3-10.9 mm; p = 0.02). Tonsillar herniation ≥ 10 mm showed sensitivity and specificity of 51% and 68%, and tonsillar herniation > 14 mm showed sensitivity and specificity of 30% and 100%, respectively, for predicting CAH. Other 2D measurements showed no statistically significant differences. CONCLUSIONS: Among the 2D measurements used, only the extent of tonsillar herniation is different between CMI patients with and without CAH. Although CMI is diagnosed with tonsillar herniation of only 5 mm, we found that a much higher extent of herniation is needed to be predictive of CAH.

Feasibility, safety, and utility of brain MRI for patients with non-MRI-conditioned CIED.

Feasibility, safety, and utility of brain MRI for patients with non-MRI-conditioned cardiac implantable electrical devices (CIEDs) remains controversial. While a growing number of studies have shown safe employment in select patients under strict protocols, there is an increasing clinical need for further off-label investigations. To assess the feasibility and utility of brain MRI in neurological and neurosurgical patients with non-MRI-conditioned CIEDs using off-label protocol. We retrospectively evaluated 126 patients with non-MRI-conditioned CIEDs referred to our hospital between 2014 to 2018 for MRI under an IRB-approved protocol. A total of 126 off-label brain MRI scans were performed. The mean age was 67.5 ± 13.0. Seventy percent of scans were performed on female patients. Indications for MRI are neurosurgical (45.2%), neurological (51.6%), and others (3.2%). MRI utilization for tumor cases was highest for tumor cases (68.3%), but employment was valuable for vascular (12.7%), deep brain stimulators (3.2%), and other cases (15.9%). In the tumor category, (37.2%) of the scans were performed for initial diagnosis and pre-surgical planning, (47.7%) for post-intervention evaluation/surveillance, (15.1%) for stereotactic radiosurgery treatment (CyberKnife). No clinical complications were encountered. No functional device complications of the CIED were identified during and after the MRI in 96.9% of the studies. A 49.6% of the off-label brain MRI scans performed led to a clinically significant decision and/or intervention for the patients. A 42.9% of obtained MRI studies did not change the plan of care. A 7.9% of post-scan decision-making data was not available. We demonstrate that off-label brain MRI scans performed on select patients under a strict protocol is feasible, safe, and relevant. Almost 50% of scans provided critical information resulting in clinical intervention of the patients.

Chiari I malformation and pregnancy: a comprehensive review of the literature to address common questions and to guide management.

BACKGROUND: The optimal management of Chiari I malformation during pregnancy remains uncertain. Labor contractions, which increase intracranial pressure, and neuraxial anesthesia both carry the theoretical risk of brainstem herniation given the altered CSF dynamics inherent to the condition. Mode of delivery and planned anesthesia, therefore, require forethought to avoid potentially life-threatening complications. Since the assumed potential risks are significant, we seek to systematically review published literature regarding Chiari I malformation in pregnancy and, therefore, to establish a best practice recommendation based on available evidence. METHODS: The English-language literature was systematically reviewed from 1991 to 2018 according to PRISMA guidelines to assess all pregnancies reported in patients with Chiari I malformation. After analysis, a total of 34 patients and 35 deliveries were included in this investigation. Additionally, a single case from our institutional experience is presented for illustrative purposes but not included in the statistical analysis. RESULTS: No instances of brain herniation during pregnancy in patients with Chiari I malformation were reported. Cesarean deliveries (51%) and vaginal deliveries (49%) under neuraxial blockade and general anesthesia were both reported as safe and suitable modes of delivery. Across all publications, only one patient experienced a worsening of neurologic symptoms, which was only later discovered to be the result of a previously undiagnosed Chiari I malformation. Several patients underwent decompressive suboccipital craniectomy to treat the Chiari I malformation during the preconception period (31%), during pregnancy (3%), and after birth (6%). Specific data regarding maternal management were not reported for a large number (21) of these patients (60%). Aside from one abortion in our own institutional experience, there was no report of any therapeutic abortion or of adverse fetal outcome. CONCLUSIONS: Although devastating maternal complications are frequently feared, very few adverse outcomes have ever been reported in pregnant patients with a Chiari I malformation. The available evidence is, however, rather limited. Based on our survey of available data, we recommend vaginal delivery under neuraxial blockade for truly asymptomatic patients. Furthermore, based on our own experience and physiological conceptual considerations, we recommend limiting maternal Valsalva efforts either via Cesarean delivery under regional or general anesthesia or by choosing assisted vaginal delivery under neuraxial blockade. There is no compelling reason to offer suboccipital decompression for Chiari I malformation during pregnancy. For patients with significant neurologic symptoms prior to conception, decompression prior to pregnancy should be considered.

Performance of On-Call Radiology Residents in Interpreting Total Spine MRI Studies for the Detection of Spinal Cord Compression or Cauda Equina Compression.

OBJECTIVE. Accurate diagnosis of spinal cord compression (SCC) or cauda equina compression (CEC) is important in the emergency setting so management decisions may be made promptly. The purpose of this study is to evaluate the performance of on-call radiology residents in interpreting total spine MRI studies for the detection of SCC or CEC. MATERIALS AND METHODS. On-call radiology residents' preliminary interpretation of total spine MRI studies performed over a period of two and half years were evaluated. Agreements and disagreements were determined for SCC (defined as severe spinal stenosis with compression of the spinal cord and lack of surrounding CSF), CEC (defined as > 75% narrowing of the lumbar canal and lack of CSF in the thecal sac), and the presence of other significant findings that might impact clinical management. Studies with true-positive, true-negative, false-positive, and false-negative findings were identified. RESULTS. SCC or CEC was present in 72 of the 295 studies with preliminary interpretations done by on-call residents. The sensitivity and specificity for detecting SCC or CEC were 93.1% and 98.2%, respectively. Sensitivity was higher for 3rd- and 4th-year residents (97.7%) than for 2nd-year residents (86.2%). Other significant findings were present in 34 of the 295 studies. The overall sensitivity and specificity for the detection of other significant findings were 85.3% and 100.0%, respectively. The level of training did not affect the detection of other significant findings. CONCLUSION. The overall sensitivity of on-call radiology residents' interpretation of total spine MR images for the detection of SCC or CEC was high, improving with their level of training. However, residents' sensitivity was slightly less for the detection of other significant findings. Resident performance can be further improved with focused training and the use of a preliminary interpretation template.

Comparison of Automated CT Perfusion Softwares in Evaluation of Acute Ischemic Stroke.

BACKGROUND AND PURPOSE: Automated imaging software is integral to decision-making in acute ischemic stroke (AIS) during extended time windows. RAPID software is the most widely used and has been validated in landmark endovascular trials. Olea software is another commercially available and FDA-approved software, but has not been studied in AIS trials. We aimed to compare the diagnostic utility and accuracy of RAPID and Olea in everyday clinical practice outside of a clinical trial. METHODS: We analyzed prospectively-collected data from a consecutive cohort of 141 patients with suspected AIS who underwent computed tomography perfusion upon presentation followed by diffusion-weighted magnetic resonance imaging (DWI-MRI) within 24-48 hours. Core infarct was defined as the region with a relative cerebral blood flow (rCBF) less than 30% on RAPID and rCBF less than 40% on Olea (default settings). We also evaluated rCBF less than 30% on Olea to match RAPID's default setting. Infarct volume on DWI-MRI was measured using a semiautomated segmentation method. RESULTS: Twenty-one patients were excluded; 14 due to poor bolus tracking and/or motion artifact, and 7 due to software failure. The software failure rate was 4.7% [6/127] with RAPID versus .78% [1/127] with Olea (P = .12). For the remaining 120 patients, the sensitivity and specificity for detecting an acute infarct were 40.5% and 97.6% for RAPID; 50.6% and 85.4% for Olea; and for detecting large infarcts (≥70 mL on DWI-MRI) 73.7% and 81.2% for RAPID; 73.7% and 68.3% for Olea. Core infarct volume on RAPID was more closely correlated with DWI-MRI infarct volume (rho = .64) than Olea (rho = .42). CONCLUSIONS: Our head-to-head comparison of these 2 commonly-used softwares in the clinical setting elucidates the pros and cons of their use to guide decision-making for AIS management in the acute setting.

"Barbell Sign": A Diagnostic Imaging Finding in Progressive Multifocal Leukoencephalopathy.

The recently proposed diagnostic algorithm for progressive multifocal leukoencephalopathy underscores the importance of imaging and emphasizes the role of the radiologist in the diagnostic workup. We describe a case series of patients with visual symptoms and a typical pattern of brain involvement in definite progressive multifocal leukoencephalopathy, for which we have coined the term barbell sign.

Schwannoma of the trochlear nerve-an illustrated case series and a systematic review of management.

Schwannomas of cranial nerves in the absence of systemic neurofibromatosis are relatively rare. Among these, schwannomas of the trochlear nerve are even less common. They can be found incidentally or when they cause diplopia or other significant neurological deficits. Treatment options include observation only, neuro-ophthalmological intervention, and/or neurosurgical management via resection or sterotactic radiosurgery (SRS). In recent years, the latter has become an attractive therapeutic tool for a number of benign skull base neoplasm including a small number of reports on its successful use for trochlear Schwannomas. However, no treatment algorithm for the management of these tumors has been proposed so far. The goal of this manuscript is to illustrate a case series of this rare entity and to suggest a rational treatment algorithm for trochlear schwannomas, based on our institutional experience of recent cases, and a pertinent review of the literature. Including our series of 5 cases, a total of 85 cases reporting on the management of trochlear schwannomas have been published. Of those reported, less than half (40 %) of patients underwent surgical resection, whereas the remainder were managed conservatively or with SRS. Seventy-six percent (65/85) of the entire cohort presented with diplopia, which was the solitary symptom in over half of the cases (n = 39). All patients who presented with symptoms other than diplopia or headaches as solitary symptoms underwent surgical resection. Patients in the non-surgical group were mostly male (M/F = 3.5:1), presented at an older age and had shorter mean diameter (4.6 vs. 30.4 mm, p < 0.0001) when compared to the surgical group. Twelve patients in the entire cohort were treated with SRS, none of whom had undergone surgical resection before or after radiation treatment. Trochlear schwannoma patients without systemic neurofibromatosis are rare and infrequently reported in the literature. Of those, patients harboring symptomatic trochlear Schwannomas do not form a single homogenous group, but fall into two rather distinct subgroups regarding demographics and clinical characteristics. Among those patients in need of intervention, open microsurgical resection as well as less invasive treatment options exist, which all aim at safe relief of symptoms and prevention of progression. Both open microsurgical removal as well as SRS can achieve good long-term local control. Consequently, a tailored multidisciplinary treatment algorithm, based on the individual presentation and tumor configuration, is proposed.

White matter damage in maintenance hemodialysis patients: a diffusion tensor imaging study.

BACKGROUND: Patients treated with dialysis have high rates of brain infarcts, brain atrophy, and white matter disease. There are limited data regarding the presence of more subtle damage to brain white matter. METHODS: In the Cognition and Dialysis Study, we compared brain structure using diffusion tensor imaging in hemodialysis (HD) patients to individuals without known kidney disease, using tract based spatial statistics (TBSS) to compare Fractional Anisotropy (FA) and Mean Diffusivity (MD). Statistical comparison of each overlaid voxel was age controlled using a permutation based corrected p value of <0.05. RESULTS: Thirty-four HD patients and twenty six controls (52 vs 51 years for HD vs control) had adequate magnetic resonance imaging for analysis. The HD group had fewer women (38% vs 23%) and a higher prevalence of diabetes (29% vs 8%), heart failure (29% vs 0%) and clinical stroke (15% vs 0%). Hemodialysis patients had significantly lower FA across multiple white matter fiber tracts, with fronto-temporal connections, the genu of the corpus callosum and the fornix more significantly affected than posterior regions of the brain. Similarly, HD patients had significantly higher mean diffusivity in multiple anterior brain regions. Results remained similar when those with a prior history of stroke were excluded. CONCLUSIONS: In HD patients, there is more white matter disease in the anterior than posterior parts of the brain compared to controls without kidney disease. This pattern of injury is most similar to that seen in aging, suggesting that developing chronic kidney disease and ultimately kidney failure may result in a phenotype consistent with accelerated aging.

Three-dimensional brain MRI for DBS patients within ultra-low radiofrequency power limits.

BACKGROUND: For patients with deep brain stimulators (DBS), local absorbed radiofrequency (RF) power is unknown and is much higher than what the system estimates. We developed a comprehensive, high-quality brain magnetic resonance imaging (MRI) protocol for DBS patients utilizing three-dimensional (3D) magnetic resonance sequences at very low RF power. METHODS: Six patients with DBS were imaged (10 sessions) using a transmit/receive head coil at 1.5 Tesla with modified 3D sequences within ultra-low specific absorption rate (SAR) limits (0.1 W/kg) using T2 , fast fluid-attenuated inversion recovery (FLAIR) and T1 -weighted image contrast. Tissue signal and tissue contrast from the low-SAR images were subjectively and objectively compared with routine clinical images of six age-matched controls. RESULTS: Low-SAR images of DBS patients demonstrated tissue contrast comparable to high-SAR images and were of diagnostic quality except for slightly reduced signal. CONCLUSIONS: Although preliminary, we demonstrated diagnostic quality brain MRI with optimized, volumetric sequences in DBS patients within very conservative RF safety guidelines offering a greater safety margin.

Transient Decrease in Cerebrospinal Fluid Motion is Related to Cough-Associated Headache in Chiari I Malformation (Original Research Article).

INTRODUCTION: Short-lasting cough-associated Headache (CAH) in patients with Chiari I Malformation (CMI) is believed to be due to transient worsening of CSF flow obstruction at the foramen magnum. We assessed changes in CSF flow in response to coughing in CMI patients with CAH and compared to those without CAH and healthy participants (HP) using real-time MRI. MATERIALS AND METHODS: Seventeen CMI patients (12 with CAH, 5 without CAH) and 6 HP were prospectively assessed using real-time pencil-beam imaging (PBI) MR sequence. A 64-mm length PBI cylinder was placed at the cranio-cervical junction. CSF stroke volume (SVCSF) was assessed during resting, post-coughing and relaxation phases via a 90-second scan. SVCSF was measured at six levels at 5-mm intervals between 10 and 35 mm below the foramen magnum. During each phase, SVCSF was compared between CMI with and without CAH and HP and corrected for multiple comparisons. RESULTS: At multiple consecutive levels, post-coughing SVCSF was significantly lower in CMI with CAH compared to both CMI without CAH and HP (p <0.05). No differences in post-coughing SVCSF were seen between CMI without CAH and HP. At rest or relaxation phase, no differences in SVCSF were seen between patients with and without CAH but minimal differences were seen between CMI with CAH and HP. CONCLUSIONS: A decrease in CSF flow after coughing in CMI patients with CAH supports the notion that CAH is caused by transient worsening of CSF flow obstruction at the foramen magnum.