MRI Safety of Stapes Prostheses: A Systematic Review.

OBJECTIVE: To assess magnetic resonance imaging (MRI) safety of stapes prostheses. DATA SOURCES: Ovid MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus databases were searched from inception to November 2021 following PRISMA guidelines. REVIEW METHODS: Studies reporting evidence of stapes prosthesis displacement or interaction in adult or pediatric implant recipients undergoing MRI. Cadaveric, animal, and basic studies with nonhuman data were also included. RESULTS: From an initial search of 123 articles, 42 full-text studies were evaluated for eligibility and 19 studies that met the inclusion criteria were included. Motion artifact was reported in a few stainless steel prosthesis types in vitro; however, such displacement was not observed in human cadaver temporal bone studies and had no adverse reported outcomes. A small subgroup of patients in the 1980s received a ferromagnetic stainless steel stapes implant that was recalled and has not been used since 1987. Patients with implants performed in the 1980s should be directed to 1.5T scanners from an abundance of caution. CONCLUSION: Modern (post-1987) stapes prostheses do not pose a risk in vivo when exposed to the magnetic fields of MRI scanners.

Arachnoiditis, a complication of epidural blood patch for the treatment of low-pressure headache: A case report and systematic review.

OBJECTIVE: To report a case of arachnoiditis as a complication of epidural blood patch procedures and to systematically review the diagnostic workup, clinical outcomes, and treatment modalities reported in the literature. BACKGROUND: Epidural blood patching is an effective treatment for low-pressure headache secondary to spontaneous cerebrospinal fluid leak or iatrogenic post-dural puncture. Spontaneous intracranial hypotension is believed to be a rare headache disorder, but recently has been diagnosed at higher frequencies, making it an important differential diagnosis for intractable headaches. Arachnoiditis has surfaced as a rare complication of epidural blood patching. Symptom presentation does not always correlate with evidence of meningeal enhancement on imaging. Optimal methods for treatment remain largely unknown. METHODS: Databases Embase and PubMed were searched for all published studies on arachnoiditis post-epidural blood patch using a combination of the following medical subject headings and keywords: arachnoiditis, arachnoid inflammation, adverse event, and epidural blood patch. All original English-language articles that described arachnoid and/or meningeal inflammation in conjunction with epidural blood patch procedures were included for analysis. Title and abstract screening, data extraction, and risk of bias assessment were conducted independently and in duplicate by two reviewers. RESULTS: Seven other cases of arachnoiditis post-blood patch placement have been documented, most of which were diagnosed via magnetic resonance imaging. Six of these were a result of a spinal-epidural anesthesia for labor and delivery. Common symptoms reported were headache, back and radicular pain, paresthesia, and motor weakness. There are currently no proven consensus-based treatment recommendations available. While intravenous methylprednisolone followed by oral prednisone taper was found to be effective in the case presented, the benefit of other multi-modal therapies was unclear. CONCLUSIONS: Headache specialists who treat postural headache should be aware of arachnoiditis as a potentially severe complication of epidural blood patch. The case presented is the first of its kind to report arachnoiditis as a complication of high-volume blood patch for the treatment of spontaneous intracranial hypotension. More studies are required to determine suitable treatment options for post-epidural blood patch arachnoiditis.

Safety Considerations of 7-T MRI in Clinical Practice.

Although 7-T MRI has recently received approval for use in clinical patient care, there are distinct safety issues associated with this relatively high magnetic field. Forces on metallic implants and radiofrequency power deposition and heating are safety considerations at 7 T. Patient bioeffects such as vertigo, dizziness, false feelings of motion, nausea, nystagmus, magnetophosphenes, and electrogustatory effects are more common and potentially more pronounced at 7 T than at lower field strengths. Herein the authors review safety issues associated with 7-T MRI. The rationale for safety concerns at this field strength are discussed as well as potential approaches to mitigate risk to patients and health care professionals.

Pearls and Pitfalls of Spine Imaging.

There are many ways to image the spine. Although there is not one correct and many incorrect ways, the choice of sequences and parameters allows optimization of the protocol to the particular question that is to be answered and also to the particular preferences of the Radiologist.

Low b-value diffusion weighted imaging is promising in the diagnosis of brain death and hypoxic-ischemic injury secondary to cardiopulmonary arrest.

BACKGROUND: Cardiorespiratory arrest can result in a spectrum of hypoxic ischemic brain injury leading to global hypoperfusion and brain death (BD). Because up to 40% of patients with BD are viable organ donors, avoiding delayed diagnosis of this condition is critical. High b-value diffusion weighted imaging (DWI) measures primarily molecular self-diffusion; however, low b-values are sensitive to perfusion. We investigated the feasibility of low b-value DWI in discriminating the global hypoperfusion of BD and hypoxic ischemic encephalopathy (HIE). METHODS: We retrospectively reviewed cardiorespiratory arrest subjects with a diagnosis of HIE or BD. Inclusion criteria included brain DWI acquired at both low (50 s/mm2) and high (1000-2000 s/mm2) b-values. Automated segmentation was used to determine mean b50 apparent diffusion coefficient (ADC) values in gray and white matter regions. Normal subjects with DWI at both values were used as age- and sex-matched controls. RESULTS: We evaluated 64 patients (45 with cardiorespiratory arrest and 19 normal). Cardiorespiratory arrest patients with BD had markedly lower mean b50 ADC in gray matter regions compared with HIE (0.70 ± 0.18 vs. 1.95 ± 0.25 × 10-3 mm2/s, p < 0.001) and normal subjects (vs. 1.79 ± 0.12 × 10-3 mm2/s, p < 0.001). HIE had higher mean b50 ADC compared with normal (1.95 ± 0.25 vs. 1.79 ± 0.12 × 10-3 mm2/s, p = 0.016). There was wide separation of gray matter ADC values in BD subjects compared with age matched normal and HIE subjects. White matter values were also markedly decreased in the BD population, although they were less predictive than gray matter. CONCLUSION: Low b-value DWI is promising for the discrimination of HIE with maintained perfusion and brain death in cardiorespiratory arrest.

Reproducibility of ABC/2 method to determine infarct volume and mismatch percentage with CT perfusion.

BACKGROUND: Our aim is to implement a simple, rapid, and reliable method using computed tomography perfusion imaging and clinical judgment to target patients for reperfusion therapy in the hyper-acute stroke setting. We introduce a novel formula (1-infarct volume [CBV]/penumbra volume [MTT] × 100%) to quantify mismatch percentage. METHODS: Twenty patients with anterior circulation strokes who underwent CT perfusion and received intravenous tissue plasminogen activator (IV tPA) were analyzed retrospectively. Nine blinded viewers determined volume of infarct and ischemic penumbra using the ABC/2 method and also the mismatch percentage. RESULTS: Interrater reliability using the volumetric formula (ABC/2) was very good (intraclass correlation [ICC] = .9440 and ICC = .8510) for hemodynamic parameters infarct (CBV) and penumbra (MTT). ICC coefficient using the mismatch formula (1-MTT/CBV × 100%) was good (ICC of .635). CONCLUSIONS: The ABC/2 method of volume estimation on CT perfusion is a reliable and efficient approach to determine infarct and penumbra volumes. The 1-CBV/MTT × 100% formula produces a mismatch percentage assisting providers in communicating the proportion of salvageable brain and guides therapy in the setting of patients with unclear time of onset with potentially salvageable tissue who can undergo mechanical retrieval or intraarterial thrombolytics.

The fetal posterior fossa: clinical correlation of findings on prenatal ultrasound and fetal magnetic resonance imaging.

OBJECTIVES: Recognize posterior fossa anomalies on ultrasound and magnetic resonance imaging and appreciate imaging pitfalls that may lead to misdiagnosis. MATERIALS AND METHODS: Cases are presented to illustrate normal development and various anomalies. Postnatal studies and autopsy are used for correlation with prenatal imaging. RESULTS: Normal anatomy and anomalies are demonstrated. Pitfalls such as cystic hygroma, pseudomasses, and use of nonstandard scan planes are illustrated. CONCLUSIONS: Recognizing normal developing structures is an important component of performing fetal ultrasound. Documentation of the cerebellum, vermis, and cisterna magna are required for posterior fossa evaluation in any American Institute of Ultrasound in Medicine-certified practice. Normal variations are common, and understanding the anatomy is vital to avoid misdiagnosis and to accurately characterize abnormalities.

Basis for abnormal desquamation and permeability barrier dysfunction in RXLI.

Mutations in the gene for steroid sulfatase (SSase), are responsible for recessive x-linked ichthyosis (RXLI). As a consequence of SSase deficiency, its substrate, cholesterol sulfate (CSO4), accumulates in the epidermis. Accumulation of this amphipathic lipid in the outer epidermis provokes both a typical scaling phenotype and permeability barrier dysfunction. Research on RXLI has illuminated several, potentially overlapping pathogenic mechanisms and provided insights about the role of SSase and CSO4 in normal differentiation, barrier maintenance, and desquamation. We now show here that SSase is concentrated in lamellar bodies (LB), and secreted into the SC interstices, along with other LB-derived lipid hydrolases. There, it degrades CSO4, generating some cholesterol for the barrier, while the progressive decline in CSO4 (a serine protease (SP) inhibitor) permits corneodesmosome (CD) degradation leading to normal desquamation. Two molecular pathways contribute to disease pathogenesis in RXLI: 1) excess CSO4 produces nonlamellar phase separation in the stratum corneum (SC) interstices, explaining the barrier abnormality. 2) The increased CSO4 in the SC interstices inhibit activity sufficiently to delay CD degradation, leading to corneocyte retention. We also show here that increased Ca++ in the SC interstices in RXLI could contribute to corneocyte retention, by increasing CD and interlamellar cohesion. RXLI represents one of the best understood diseases in dermatology--from the gene to the SC interstices, its etiology and pathogenesis are becoming clear, and assessment of disease mechanisms in RXLI led to new insights about the role of SSase and CSO4 in epidermis terminal differentiation.

Contrast dynamics during CT pulmonary angiogram: analysis of an inspiration associated artifact.

OBJECTIVE: Several artifacts have been observed during contrast-enhanced CT of the pulmonary arteries. We describe a physiological artifact caused by a transient interruption of the contrast column in the pulmonary arteries associated with inspiration immediately prior to imaging. This results from a variable inflow of unopacified blood from the inferior vena cava (IVC). MATERIALS AND METHODS: From 327 consecutive pulmonary CT-angiograms, all performed on a single detector scanner at 3 mm collimation (1.5 mm incremental reconstruction), 50 positive studies, 46 indeterminate studies, and 33 negative studies (129 exams) were retrospectively reviewed by a blinded observer to determine the frequency of the described contrast interruption, its severity (mild, moderate, or severe), and its possible contribution to misinterpretation of studies. The numerical change in Hounsfield units was assigned within the right ventricular chamber for each examination to correlate with the subjective evaluation of severity. Statistical significance was determined with P = 0.05%. RESULTS: The artifact was present in 48 (37.2%) of the 129 evaluated studies. It was greater in frequency (50.0%) with the negative studies. The presence was 25% with positive studies and 36.7% with indeterminate exams. The interruption was more often mild (<100 HU change) in severity (45.8%). Three (6.6%) definite false positives were detected where the misinterpretation was directly attributed to the artifact. Three (6.6%) other examinations called positive were also directly related to the interrupted contrast column. However, since no further pulmonary vascular evaluation was performed, these examinations can only be considered indeterminate. Two of the latter 3 studies demonstrated a severe (>150 HU change) and the other study demonstrated a moderate (100-150 HU) interruption of contrast opacification. CONCLUSIONS: During inspiration, there is a variable increase in unopacified venous blood from the IVC, briefly diluting the contrast column entering from the SVC. This interruption is common, though usually mild in severity. However, a short severe interruption of vascular opacification can lead to misinterpretation as a pulmonary embolus or contribute to an indeterminate examination.