Spontaneous intracranial hypotension: updates from diagnosis to treatment.

Spontaneous intracranial hypotension (SIH) is caused by spinal cerebrospinal fluid (CSF) leaks, which result in continued loss of CSF volume and multiple debilitating clinical manifestations. The estimated annual incidence of SIH is 5/100,000. Diagnostic methods have evolved in recent years due to improved understanding of pathophysiology and implementation of advanced myelographic techniques. Here, we synthesize recent updates and contextualize them in an algorithm for diagnosis and treatment of SIH, highlighting basic principles and points of practice variability or continued debate. This discussion includes finer points of SIH diagnosis, CSF leak classification systems, less common types and variants of CSF leaks, brain MRI Bern scoring, potential SIH complications, key technical considerations, and positioning strategies for different types of dynamic myelography. The roles of conservative measures, non-targeted or targeted blood patches, surgery, and recently developed endovascular techniques are presented.

MRI-guided focused ultrasound ablation of painful lumbar facet joints: a retrospective assessment of safety and tolerability in human subjects.

OBJECTIVE: To evaluate the safety and tolerability of MRI-guided focused ultrasound (MRgFUS) for the treatment of facet joint-mediated pain in human subjects for whom conventional treatment had failed. Secondarily, to evaluate effectiveness of the procedure. METHODS: Consecutive patients who underwent MRgFUS at our institution were retrospectively identified. Chart review was performed to obtain relevant clinical and technical data. All patients had chronic low back pain and positive comparative medial branch blocks. RESULTS: Twenty-six MRgFUS treatments in 20 patients were included. Mean sonication energy was 1436.6 Joules. The procedure was technically successful in all patients. Of the treated patients, 29.6% experienced short-term worsening of low back pain immediately after the procedure, all by 1-4 points on a 0-10 scale. One patient (3.8%) reported temporary worsening of preexisting radicular symptoms after the procedure. Of 21 treatments with clinical follow-up of at least 3 months available, 12 (57.1%) had >3 months' pain relief, 2 (10%) had <3 months' benefit, 6 (30%) reported no benefit, and 1 (5%) patient was lost to follow-up. In patients who reported at least some benefit with prior conventional radiofrequency ablation, 8/10 (80%) benefited from the MRgFUS procedure. CONCLUSION: The present study demonstrates that MRgFUS ablation of the lumbar facet joints is a safe and tolerable procedure in human subjects and could provide another option for patients for whom radiofrequency ablation had failed. More than half of all patients received significant durable pain relief, which jumped to 80% for patients who had experienced at least some benefit from prior radiofrequency ablations.

Safety profile and technical success rate of computed tomography-guided atlanto-axial lateral articulation injections.

OBJECTIVE: To describe the technique, safety profile, and outcome of computed tomography (CT)-guided atlanto-axial lateral articulation injections performed at our institution. METHODS: Consecutive cases of all CT-guided atlanto-axial injections performed from January 2017 to April 2022 at our institution were searched in the electronic medical records. Patient charts were reviewed for demographics, characterization of pain, potential altered anatomy, pain level before and immediately after the procedure, procedure technique, complications, and follow-up outcomes, if available. RESULTS: Forty-five injections in 40 different patients were included. The average age was 67.4 years, and 28 (70%) of the patients were female. Of the 45 injections, 43 (96%) were technically successful. The average change in pain score (0-10) from immediately before to immediately after the injection was -3.36 (SD = 2.87, range = -8 to +3). Of all injections, 14 (31%) had a postprocedural pain score of zero. In 2 cases (4%), patients reported an increase in pain score immediately after the injection. In 3 cases (7%), transient non-vertebral artery vascular uptake of contrast was documented during the procedure, which could be cleared with needle repositioning. There were no complications. CONCLUSION: CT-guided atlanto-axial lateral articulation injection is a safe procedure with a high technical success rate. It allows for direct visualization of vital structures and provides an alternative option to the traditional fluoroscopic guidance, especially in cases of prior technically unsuccessful fluoroscopically guided injection or altered anatomy.

Successful fusion versus pseudarthrosis after spinal instrumentation: a comprehensive imaging review.

PURPOSE: Following spinal instrumentation and fusion, differentiating between successful arthrodesis and pseudoarthrosis on imaging can be challenging. Interpretation of such examinations requires understanding both the expected evolution of postoperative findings and the subtle indicators of pseudoarthrosis across multiple imaging modalities. Due to this level of intricacy, many clinicians lack familiarity with the subject beyond the more rudimentary concepts. METHODS: This review provides an in-depth overview of the imaging of the post-operative spine, with particular emphasis on differentiating between pseudoarthrosis and arthrodesis. RESULTS: A comprehensive overview of imaging of the post-operative spine is given, including the most common imaging modalities utilized, the expected post-operative findings, imaging findings in pseudoarthrosis, and imaging definitions of fusion. CONCLUSION: Differentiating between pseudoarthrosis and arthrodesis in the postoperative spine is complex, and requires a robust understanding of various findings across many different modalities.

Lateral decubitus dynamic CT myelography for fast cerebrospinal fluid leak localization.

Dynamic CT myelography is used to precisely localize fast spinal CSF leaks. The procedure is most commonly performed in the prone position, which successfully localizes most fast ventral leaks. We have recently encountered a small subset of patients in whom prone dynamic CT myelography is unsuccessful in localizing leaks. We sought to determine the added value of lateral decubitus dynamic CT myelography, which is occasionally attempted in our practice, in localizing the leak after failed prone dynamic CT myelography. We retrospectively identified 6 patients who underwent lateral decubitus dynamic CT myelography, which was performed in each case because their prone dynamic CT myelogram was unrevealing. Two neuroradiologists independently reviewed preprocedural spine MRI and all dynamic CT myelograms for each patient. Lateral decubitus positioning allowed for precise leak localization in all 6 patients. Five of six patients were noted to have dorsal and/or lateral epidural fluid collections on spine MRI. One patient had a single prominent diverticulum on spine MRI (larger than 6 mm), whereas the others had no prominent diverticula. Our study suggests that institutions performing dynamic CT myelography to localize fast leaks should consider a lateral decubitus study if performing the study in the prone position is unrevealing. Furthermore, the presence of dorsal and/or lateral epidural fluid collections on spine MRI may suggest that a lateral decubitus study is of higher yield and could be considered initially.

Injection into the Space of Okada During Transforaminal Epidural Steroid Injections.

OBJECTIVE: Ensuring medication delivery to the epidural space is crucial for effective transforaminal epidural steroid injections. Epidural needle placement is determined by injecting a small amount of contrast at the final needle position. The purpose of this study is to illustrate the appearance of contrast flow in the retrodural retroligamentous space of Okada during computed tomography- and fluoroscopy-guided cervical and lumbar transforaminal epidural steroid injections. DESIGN: This retrospective study will use a series of cases to demonstrate contrast within the space of Okada during epidural transforaminal steroid injections. SETTING: Tertiary medical center. SUBJECTS: Study subjects are adult patients who underwent transforaminal epidural steroid injection at our institution. METHODS: Cases were identified through the use of a search engine of existing radiology reports at our institution. Epidural steroid injection procedural reports were searched for the terms "Okada" and "retrodural space." Images from the procedure were reviewed by the authors (all proceduralists with dedicated training in spinal injections) to confirm the presence of contrast within the space of Okada. RESULTS: This case series illustrates six examples of contrast injection into the retrodural space of Okada during cervical and lumbar transforaminal epidural steroid injections. CONCLUSIONS: Contrast uptake in the retrodural space of Okada may be seen during transforaminal epidural injections. Although relatively uncommon, it is likely underrecognized. It is extremely important that providers who perform transforaminal epidural steroid injections be familiar with this non-epidural contrast flow pattern so they can adjust needle positioning to deliver steroid to the epidural space.

Vessel wall imaging features of Moyamoya disease in a North American population: patterns of negative remodelling, contrast enhancement, wall thickening, and stenosis.

BACKGROUND: This study characterized vessel wall imaging (VWI) features of Moyamoya disease (MMD) in a predominantly adult population at a North American center. METHODS: Consecutive patients with VWI were included. Twelve arterial segments were analyzed for wall thickening, degree and pattern of contrast enhancement, and remodeling. RESULTS: Overall, 286 segments were evaluated in 24 patients (mean age = 36.0 years [range = 1-58]). Of 172 affected segments, 163 (95%) demonstrated negative remodeling. Complete vessel wall obliteration was most frequent in the proximal M1 (17/48, 35%). Affected segments enhanced in 72/172 (42%) (n = 15 for grade II; n = 54 for concentric and n = 18 for eccentric); 20 of 24 (83%) patients had at least one enhancing segment. Both enhancing and non-enhancing segments were present in 19/20 (95%) patients. Vessel wall enhancement was most common in the proximal segments and correlated to the degree of stenosis (p < 0.001), and outer wall diameter (p < 0.001), but not disease duration (p = 0.922) or Suzuki score (p = 0.477). Wall thickening was present in 82/172 (48%) affected segments and was associated with contrast enhancement (p < 0.001), degree of stenosis (p < 0.001), and smaller outer wall diameter (p = 0.004). CONCLUSION: This study presents VWI findings in North American patients with MMD. Negative remodeling was the most common finding. Most patients had both enhancing and non-enhancing abnormal segments. Vessel wall enhancement was most common in proximal segments, variable in pattern or degree and was correlated to the degree of stenosis and smaller outer wall diameter.

Agreement between neuroimages and reports for natural language processing-based detection of silent brain infarcts and white matter disease.

BACKGROUND: There are numerous barriers to identifying patients with silent brain infarcts (SBIs) and white matter disease (WMD) in routine clinical care. A natural language processing (NLP) algorithm may identify patients from neuroimaging reports, but it is unclear if these reports contain reliable information on these findings. METHODS: Four radiology residents reviewed 1000 neuroimaging reports (RI) of patients age > 50 years without clinical histories of stroke, TIA, or dementia for the presence, acuity, and location of SBIs, and the presence and severity of WMD. Four neuroradiologists directly reviewed a subsample of 182 images (DR). An NLP algorithm was developed to identify findings in reports. We assessed interrater reliability for DR and RI, and agreement between these two and with NLP. RESULTS: For DR, interrater reliability was moderate for the presence of SBIs (k = 0.58, 95 % CI 0.46-0.69) and WMD (k = 0.49, 95 % CI 0.35-0.63), and moderate to substantial for characteristics of SBI and WMD. Agreement between DR and RI was substantial for the presence of SBIs and WMD, and fair to substantial for characteristics of SBIs and WMD. Agreement between NLP and DR was substantial for the presence of SBIs (k = 0.64, 95 % CI 0.53-0.76) and moderate (k = 0.52, 95 % CI 0.39-0.65) for the presence of WMD. CONCLUSIONS: Neuroimaging reports in routine care capture the presence of SBIs and WMD. An NLP can identify these findings (comparable to direct imaging review) and can likely be used for cohort identification.

Advanced MRI techniques for transcranial high intensity focused ultrasound targeting.

Magnetic resonance guided high intensity focused ultrasound is a novel, non-invasive, image-guided procedure that is able to ablate intracranial tissue with submillimetre precision. It is currently FDA approved for essential tremor and tremor dominant Parkinson's disease. The aim of this update is to review the limitations of current landmark-based targeting techniques of the ventral intermediate nucleus and demonstrate the role of emerging imaging techniques that are relevant for both magnetic resonance guided high intensity focused ultrasound and deep brain stimulation. A significant limitation of standard MRI sequences is that the ventral intermediate nucleus, dentatorubrothalamic tract, and other deep brain nuclei cannot be clearly identified. This paper provides original, annotated images demarcating the ventral intermediate nucleus, dentatorubrothalamic tract, and other deep brain nuclei on advanced MRI sequences such as fast grey matter acquisition T1 inversion recovery, quantitative susceptibility mapping, susceptibility weighted imaging, and diffusion tensor imaging tractography. Additionally, the paper reviews clinical efficacy of targeting with these novel MRI techniques when compared to current established landmark-based targeting techniques. The paper has widespread applicability to both deep brain stimulation and magnetic resonance guided high intensity focused ultrasound.

Beyond plaque: A pictorial review of non-atherosclerotic abnormalities of extracranial carotid arteries.

The common carotid artery (CCA) and extracranial internal carotid artery are subject to a wide variety of non-atheromatous pathologies. These entities are often overshadowed in both research and clinical realms by atherosclerotic disease. Nevertheless, non-atherosclerotic disease of the carotid arteries may have profound, even devastating, neurologic consequences. Hence, this review will cover both common and uncommon forms of extracranial carotid artery pathologies in a pictorial format, in order to aid the diagnostician in identifying and differentiating such pathologies.

MRI and tractography techniques to localize the ventral intermediate nucleus and dentatorubrothalamic tract for deep brain stimulation and MR-guided focused ultrasound: a narrative review and update.

The thalamic ventral intermediate nucleus (VIM) can be targeted for treatment of tremor by several procedures, including deep brain stimulation (DBS) and, more recently, MR-guided focused ultrasound (MRgFUS). To date, such targeting has relied predominantly on coordinate-based or atlas-based techniques rather than directly targeting the VIM based on imaging features. While general regional differences of features within the thalamus and some related white matter tracts can be distinguished with conventional imaging techniques, internal nuclei such as the VIM are not discretely visualized. Advanced imaging methods such as quantitative susceptibility mapping (QSM) and fast gray matter acquisition T1 inversion recovery (FGATIR) MRI and high-field MRI pulse sequences that improve the ability to image the VIM region are emerging but have not yet been shown to have reliability and accuracy to serve as the primary method of VIM targeting. Currently, the most promising imaging approach to directly identify the VIM region for clinical purposes is MR diffusion tractography.In this review and update, the capabilities and limitations of conventional and emerging advanced methods for evaluation of internal thalamic anatomy are briefly reviewed. The basic principles of tractography most relevant to VIM targeting are provided for familiarization. Next, the key literature to date addressing applications of DTI and tractography for DBS and MRgFUS is summarized, emphasizing use of direct targeting. This literature includes 1-tract (dentatorubrothalamic tract [DRT]), 2-tract (pyramidal and somatosensory), and 3-tract (DRT, pyramidal, and somatosensory) approaches to VIM region localization through tractography.The authors introduce a 3-tract technique used at their institution, illustrating the oblique curved course of the DRT within the inferior thalamus as well as the orientation and relationship of the white matter tracts in the axial plane. The utility of this 3-tract tractography approach to facilitate VIM localization is illustrated with case examples of variable VIM location, targeting superior to the anterior commissure-posterior commissure plane, and treatment in the setting of pathologic derangement of thalamic anatomy. Finally, concepts demonstrated with these case examples and from the prior literature are synthesized to highlight several potential advantages of tractography for VIM region targeting.

Comparison of non-contrast vessel wall imaging and 3-D time-of-flight MRA for atherosclerotic stenosis and plaque characterization within intracranial arteries.

PURPOSE: We compared the ability of intracranial high-resolution vessel wall imaging (VWI) without gadolinium and 3-D time-of-flight (3D-TOF) MRA techniques to characterize intracranial arterial stenosis and arterial wall plaque consistent with atherosclerotic plaque. METHODS: Consecutive intracranial VWI examinations performed within 2 months of a 3D-TOF exam with at least 1 noted plaque was included. Examinations assessed 17 vessel segments for plaque and diameters of stenotic and normal segments using double oblique reformatted images. Results were compared with the VWI and 3D-TOF exams considered the reference standard for plaque and luminal stenosis, respectively. RESULTS: Assessed segments totaled 286 from 17 patients. Proximal segment sensitivity and specificity for luminal stenosis detection with VWI was 92.5% and 82.1%, respectively, whereas for assessing plaque with 3D-TOF it was 59.4% and 98.3%, respectively. The mean intra-rater difference in luminal diameter measurements between VWI and 3D-TOF at normal segments and at the area of maximal stenosis was 0.02mm (SD 0.51mm) and 0.08mm (SD 0.66mm), respectively. CONCLUSIONS: Intracranial VWI demonstrated reasonably high sensitivity and specificity for luminal stenosis assessment using 3D-TOF as a reference standard, while 3D-TOF demonstrated low sensitivity for plaque detection. Our results suggest that VWI can be used for simultaneous assessment of luminal stenosis and plaque in the intracranial arteries.

Clinical Assessment of Metal Artifact Reduction Methods in Dual-Energy CT Examinations of Instrumented Spines.

OBJECTIVE: The purpose of this study was to evaluate the performance of three metal artifact reduction methods in dual-energy CT (DECT) examinations of instrumented spines. MATERIALS AND METHODS: Twenty patients with instrumented spines who underwent spine DECT were retrospectively identified. All scans were obtained on a dual-source 128-MDCT scanner. In addition to the original DE mixed images, DECT images were reconstructed using an iterative metal artifact reconstruction algorithm (DE iMAR), virtual monochromatic imaging (VMI) algorithm (DE Mono+), and a combination of the two algorithms DE iMAR and DE Mono+, which we refer to here as "DE iMAR Mono+." The four image series were anonymized and randomized for a reader study. Four experienced neuroradiologists rated the images in terms of artifact scores of four anatomic regions and overall image quality scores in both bone and soft-tissue display window settings. In addition, a quantitative analysis was performed to assess the performance of the three metal artifact reduction methods. RESULTS: There were statistically significant differences in the artifact scores and overall image quality scores among the four methods (both, p < 0.001). DE iMAR Mono+ showed the best artifact scores and quality scores (all, p < 0.001). The intraclass correlation coefficient for the overall image quality score was 0.779 using the bone display window and 0.892 using the soft-tissue display window (both, p < 0.001). In addition, DE iMAR Mono+ reduced the artifacts by the greatest amount in the quantitative analysis. CONCLUSION: The method that used DE iMAR Mono+ showed the best performance of spine metal artifact reduction using DECT data. These results may be specific to this CT vendor and implant type.

Contemporary and emerging magnetic resonance imaging methods for evaluation of moyamoya disease.

Numerous recent technological advances offer the potential to substantially enhance the MRI evaluation of moyamoya disease (MMD). These include high-resolution volumetric imaging, high-resolution vessel wall characterization, improved cerebral angiographic and perfusion techniques, high-field imaging, fast scanning methods, and artificial intelligence. This review discusses the current state-of-the-art MRI applications in these realms, emphasizing key imaging findings, clinical utility, and areas that will benefit from further investigation. Although these techniques may apply to imaging of a wide array of neurovascular or other neurological conditions, consideration of their application to MMD is useful given the comprehensive multidimensional MRI assessment used to evaluate MMD. These MRI techniques span from basic cross-sectional to advanced functional sequences, both qualitative and quantitative.The aim of this review was to provide a comprehensive summary and analysis of current key relevant literature of advanced MRI techniques for the evaluation of MMD with image-rich case examples. These imaging methods can aid clinical characterization, help direct treatment, assist in the evaluation of treatment response, and potentially improve the understanding of the pathophysiology of MMD.

Intracranial vessel wall imaging for evaluation of steno-occlusive diseases and intracranial aneurysms.

Cerebrovascular diseases have traditionally been classified, diagnosed and managed based on their luminal characteristics. However, over the past several years, several advancements in MRI techniques have ushered in high-resolution vessel wall imaging (HR-VWI), enabling evaluation of intracranial vessel wall pathology. These advancements now allow us to differentiate diseases which have a common angiographic appearance but vastly different natural histories (i.e. moyamoya versus atherosclerosis, reversible cerebral vasoconstriction syndrome versus vasculitis, stable versus unstable intracranial aneurysms). In this review, we detail the anatomical, histopathological and imaging characteristics of various intracranial steno-occlusive diseases and types of intracranial aneurysms and describe the role that HR-VWI can play in diagnosis, risk stratification and treatment.

The effects of statin therapy on carotid plaque composition and volume: A systematic review and meta-analysis.

BACKGROUND AND PURPOSE: Prior studies have demonstrated that statin use stabilizes and diminishes atherosclerotic lesions. The main objective of this systematic review and meta-analysis was to study the effects of statin therapy on carotid plaque composition as seen on serial high-resolution carotid plaque MRI. We hypothesized that statin therapy would result in significant improvements in lipid-rich-necrotic-core (LRNC) volumes, wall volumes and lumen volumes. MATERIALS AND METHODS: Prospective studies using serial high-resolution carotid plaque MRI (1.5 or 3T only) in patients on statin therapy to document changes in carotid plaque composition were included. All studies had a minimum of 10 patients and minimum follow-up duration of 3 months. Outcomes included change in LRNC volume, wall volume, and lumen volume at: (1) 1-6 months; (2) 7-12 months; (3) >12 months following initiation of statin therapy; and (4) at last follow-up. Meta-analysis was performed using the random effects model. Results were reported as weighted mean differences (WMD) and 95% confidence interval (CI). RESULT: Seven studies including 361 patients were included. There was no significant change in carotid wall volume or lumen volume at any time points. While there was no significant difference in LRNC at 1-6 months and at 7-12 months following initiation of statin therapy; at >12 months, there was significant decrease in LRNC volume (WMD=-9.9mm3, 95% CI=-8.9, -2.3). CONCLUSIONS: Our study suggests statin therapy is associated with significant reductions in LRNC at 1-year of statin therapy on serial carotid MRI. However, no significant reduction in carotid wall volume was seen.

Uncommon Manifestations of Intervertebral Disk Pathologic Conditions.

Beyond the familiar disk herniations with typical clinical features, intervertebral disk pathologic conditions can have a wide spectrum of imaging and clinical manifestations. The goal of this review is to illustrate and discuss unusual manifestations of intervertebral disk pathologic conditions that radiologists may encounter, including disk herniations in unusual locations, those with atypical imaging features, and those with uncommon pathophysiologic findings. Examples of atypical disk herniations presented include dorsal epidural, intradural, symptomatic thoracic (including giant calcified), extreme lateral (retroperitoneal), fluorine 18 fluorodeoxyglucose-avid, acute intravertebral (Schmorl node), and massive lumbar disk herniations. Examples of atypical pathophysiologic conditions covered are discal cysts, fibrocartilaginous emboli to the spinal cord, tiny calcified disks or disk-level spiculated osteophytes causing spinal cerebrospinal fluid (CSF) leak and intracranial hypotension, and pediatric acute calcific discitis. This broad gamut of disease includes a variety of sizes of disk pathologic conditions, from the tiny (eg, the minuscule calcified disks causing high-flow CSF leaks) to the extremely large (eg, giant calcified thoracic intradural disk herniations causing myelopathy). A spectrum of clinical acuity is represented, from hyperacute fibrocartilaginous emboli causing spinal cord infarct, to acute Schmorl nodes, to chronic intradural herniations. The entities included are characterized by a range of clinical courses, from the typically devastating cord infarct caused by fibrocartilaginous emboli, to the usually spontaneously resolving pediatric acute calcific discitis. Several conditions have important differential diagnostic considerations, and others have relatively diagnostic imaging findings. The pathophysiologic findings are well understood for some of these entities and poorly defined for others. Radiologists' knowledge of this broad scope of unusual disk disease is critical for accurate radiologic diagnoses. Online supplemental material is available for this article. (©)RSNA, 2016.

Temporal lobe anatomy: eight imaging signs to facilitate interpretation of MRI.

PURPOSE: The temporal lobe is anatomically and functionally complex. However, relatively few radiologic signs are described to facilitate recognition of temporal lobe sulci and gyri in clinical practice. We devised and tested 8 radiologic signs of temporal lobe anatomy. METHODS: Images from volumetric magnetization-prepared rapid gradient-echo imaging were analyzed of 100 temporal lobes from 26 female and 24 male patients. Patient age ranged from 1 to 79 years (mean 19 years; standard deviation 16 years). Standardized axial, coronal, and sagittal planes were evaluated and cross-referenced. Eight signs to delineate the superior temporal gyrus, Heschl gyrus (HG), parahippocampal gyrus, rhinal sulcus, collateral sulcus proper, or the occipitotemporal sulcus, or a combination, were evaluated in the sagittal or axial plane. Two neuroradiologists independently evaluated each sign; the sign was considered present only with positive reader agreement. RESULTS: All 8 signs were present in most patients. The most frequent signs were the posterior insular corner to identify HG in the axial plane (100 %), pointed STG to identify STG in the axial plane (98 %), and parahippocampal Y to identify the posterior parahippocampal gyrus in the sagittal plane (98 %). The frequencies were similar between the right and left cerebral hemispheres. CONCLUSIONS: Temporal lobe gyri and sulci can be reliably identified in multiple planes using anatomic signs.