Pearls & Oy-sters: Syndrome of Inappropriate Antidiuretic Hormone Secretion Presenting as Neuromyelitis Optica Spectrum Disorder Flare.

While it was previously believed that neuromyelitis optic spectrum disorder (NMOSD) mostly affected the optic nerves and the spinal cord, it is increasingly recognized that NMOSD can involve any area of the CNS where aquaporin-4 is highly expressed. These other areas can include the hypothalamus and the circumventricular organs that surround the third and fourth ventricles, serving as osmoregulators. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is one of the most common causes of hyponatremia and has been associated with NMOSD due to these lesions. In this report, we present a case of a patient with known NMOSD, who presented with dizziness, fatigue, and generalized weakness and whose workup revealed hyponatremia in the setting of SIADH and hypothalamic demyelinating lesions. This case illustrates an atypical presentation of NMOSD and the importance of looking for syndromes, such as SIADH. This can guide diagnostic testing, such as getting thin MRI cuts through the hypothalamus and brainstem, as well as advanced management techniques such as immunotherapy.

The black rim susceptibility sign in the MRI evaluation of intracranial colloid cysts.

BACKGROUND AND PURPOSE: Colloid cysts are relatively rare intracranial lesions located in the rostral aspect of third ventricle. They may produce acute hydrocephalus, brain herniation, and death. On conventional MRI, the appearance of a colloid cyst varies depending on its composition. Small isointense cysts can be missed. The purpose of this study is to introduce a new sign, "black rim susceptibility" sign for the accurate diagnosis of colloid cyst on susceptibility weighted imaging (SWI). METHODS: A retrospective case-control study consisted of 100 MRI brain scans (19 cases and 81 controls) performed from January 2012 to September 2018. Two fellowship trained neuroradiologists individually interpreted SWI sequences for the presence of the "black rim susceptibility" sign (thin rim of dark signal along the periphery of a rounded, hyperintense focus). RESULTS: The sample was 43% male and 57% female, with an average age of 51.8 ± 17.7. Out of 19 cases, 9 had undergone surgery in which pathology had confirmed colloid cyst. Sensitivity, specificity, and accuracy for reader 1 was 94.8%, 98.8%, and 98% and for reader 2 was 89.5%, 100%, and 98%, respectively. Positive predictive value and negative predictive value for reader 1 was 94.7% and 98.8% and for reader 2 was 100% and 97.6%, respectively. Interrater correlation between the two readers was calculated with kappa of 0.93. CONCLUSION: The black rim susceptibility appearance of colloid cyst on SWI is a novel description and an effective sign that can be used by radiologists for accurate diagnosis.

Pharyngeal Emergencies.

Pharyngeal emergencies, which can be subdivided into traumatic versus nontraumatic, are a common cause of Emergency Department visits. Patients often present to Emergency Department with a wide variety of pharyngeal symptoms, for which computed tomography imaging has become the first line imaging modality. Familiarity with these conditions enables a radiologist to make a prompt diagnosis, assess the extent of disease, and evaluate for potential complications. In this chapter, we present a brief overview of nontraumatic pharyngeal emergencies based on anatomic subdivisions (nasopharynx, oropharynx, and hypopharynx), discuss their etiologies, clinical presentations, computed tomography imaging findings, and management options. We will also discuss differential diagnoses based on imaging findings.

2D versus 3D fluoroscopy-based navigation in posterior pelvic fixation: review of the literature on current technology.

PURPOSE: Percutaneous sacroiliac (SI) fixation of unstable posterior pelvic ring injuries is a widely accepted procedure. The complex sacral anatomy with narrow osseous corridors for SI screw placement makes this procedure technically challenging. Techniques are constantly evolving as a result of better understanding of the posterior pelvic anatomy. Recently developed tools include fluoroscopy-based computer-assisted navigation, which can be two-dimensional (2D) or three-dimensional (3D). Our goal is to determine the relevant technical considerations and clinical outcomes associated with these modalities by reviewing the published research. We hypothesize that 3D fluoroscopy-based navigation is safer and superior to its 2D predecessor with respect to lower radiation dose and more accurate SI screw placement. METHODS: We searched four medical databases to identify English-language studies of 2D and 3D fluoroscopy-based navigation from January 1990 through August 2015. We included articles reporting imaging techniques and outcomes of closed posterior pelvic ring fixation with percutaneous SI screw fixation. Injuries included in the study were sacral fractures (52 patients), sacroiliac fractures (88 patients), lateral compression fractures (20 patients), and anteroposterior compression type pelvic fractures (8 patients). We excluded articles on open reduction of posterior pelvic ring injuries and solely anatomic studies. We then reviewed these studies for technical considerations and outcomes associated with these technologies. RESULTS: Six studies were included in our analysis. Results of these studies indicate that 3D fluoroscopy-based navigation is associated with a lower radiation dose and lower rate of screw malpositioning compared with 2D fluoroscopy-based systems. CONCLUSIONS: It may be advantageous to combine modern imaging modalities such as 3D fluoroscopy with computer-assisted navigation for percutaneous screw fixation in the posterior pelvis.

Second-Opinion Subspecialty Consultations in Musculoskeletal Radiology.

OBJECTIVE: The purpose of this article is to evaluate the significance of subspecialty second-opinion consultations for CT and MRI examinations in musculoskeletal (MSK) radiology. MATERIALS AND METHODS: All 3165 MSK CT and MRI examinations referred to one academic institution for second-opinion consultation during a 24-month period were reviewed by three MSK-trained radiologists. Outside and inside reports were compared by two independent MSK radiology fellows using a previously published 5-point scale. Clinically important differences (categories 4 and 5) were defined as those likely to change patient management. Statistical comparisons of rates were performed using a chi-square test with Bonferroni corrections. Interobserver reliability was reported using linear weighted kappa statistics and the percentage of agreement. RESULTS: Of all second-opinion examinations, 73.5% (2326/3165) had an outside report available for comparison and inclusion in this study. There were 610 of 2326 (26.2%) examinations with clinically important differences. The rate of clinically important discrepant readings was even higher in oncologic cases (36.3%; 331/911). When the final diagnosis was determined from pathology reports performed after internal interpretation, the second-opinion consultation was noted to be correct in 82.0% (334/407) of examinations with category 4 or 5 discrepancies. There was very good agreement (κ = 0.93) in scoring the discrepancies between second-opinion consultants. CONCLUSION: The subspecialty second-opinion consultation was more accurate than outside reports in 82.0% of examinations when pathologic confirmation was made. A moderate rate (26.2%) of discrepant interpretations was noted between outside and inside MSK imaging examinations, especially in tumor cases (36.3%). Most discrepancies were in interpreting rather than detecting abnormalities.

Patellar instability: CT and MRI measurements and their correlation with internal derangement findings.

PURPOSE: To test the inter-observer and inter-method reliability among the measures suggesting patellofemoral joint disorder on both CT and MRI in the same subject and find possible association with internal derangements of the patellofemoral joint on MRI. METHODS: Institutional review board approval was obtained with waiver of the informed consent in this HIPPA-compliant study. CT and MRI were evaluated in 32 knees in 32 respective subjects (10 men/22 women, mean age 38 ± 19 years). Three trained observers assessed tibial tuberosity-trochlear groove (TT-TG) distance, trochlear angle and trochlear depth on both CT and MRI. Intra-class correlation coefficient (ICC) was used to evaluate inter-observer and inter-method reliability. Two radiologists' consensus reading was used to evaluate their association with soft tissue abnormalities of the patellofemoral joint. Chi-square test was used to assess the statistical significance of the qualitative variables. RESULTS: There was an excellent inter-observer reliability (ICC for CT >0.89 and for MRI >0.90) and inter-method reliability (ICC >0.86) for all the quantitative measurements. There was a significant association between increased TT-TG distance value on MR imaging and lateral facet patellar cartilage abnormality and joint effusion (p < 0.05). CONCLUSION: Quantitative trochlear parameters can be reliably calculated on MRI, and an abnormal TT-TG distance is the most useful measurement among various static MR imaging parameters to correlate with patellar chondrosis and joint effusion. TT-TG distance should be reported in patellofemoral pain syndrome patients. LEVEL OF EVIDENCE: IV.

Patellofemoral friction syndrome: magnetic resonance imaging correlation of morphologic and T2 cartilage imaging.

OBJECTIVE: This study aimed to investigate whether patellofemoral T2 cartilage changes are associated with lateral patellofemoral friction syndrome (PFS), as indicated by an edema-like signal within the superolateral infrapatellar (Hoffa) fat pad. METHODS: In this institutional review board-approved retrospective study of 510 consecutive patients, 49 patients with 50 knee magnetic resonance imaging examinations demonstrating normal or low-grade patellofemoral cartilage abnormalities (whole-organ magnetic resonance imaging score [WORMS] score, ≤2) were included. Twenty-two examinations with PFS (cases) were compared with an age- and sex-matched cohort of 28 examinations without PFS (controls). A 3-T magnetic resonance imaging was performed with multi-echo, spin-echo T2 mapping. Two readers measured in consensus malalignment parameters, including patellar height index, tibial tuberosity to trochlear groove distance, and sulcus angle. Bulk T2 cartilage values in the lateral and medial patellofemoral compartment, central weight-bearing medial and lateral femoral condyles were measured independently. Interobserver agreement was quantified using concordance correlation coefficients. Demographics, anatomic measurements, whole-organ magnetic resonance imaging scores, and cartilage T2 values were compared between cases and controls using Fisher exact test, Wilcoxon rank sum test, and mixed-effects models. RESULTS: Cases demonstrated higher patellar height index (P = 0.002) and tibial tuberosity to trochlear groove distance (P = 0.02). Interobserver agreement for T2 values was good overall (concordance correlation coefficient range, 0.65-0.93). Cases demonstrated higher medial facet patellar bulk T2 (38.1 [7.5] ms) versus controls (33.6 [7.3] ms) (P = 0.02); otherwise, there were no significant differences in regional T2 values. CONCLUSIONS: T2 mapping in patients with PFS demonstrates increased cartilage T2 in the medial patellar facet, possibly reflecting collagen alteration from early chondromalacia (softening) or increased water content related to altered contact pressures.

Epithelioid sarcoma presenting as radial mononeuropathy: anatomical, magnetic resonance neurography and diffusion tensor imaging appearances.

The authors report an unusual case of radial mononeuropathy caused by epithelioid sarcoma and describe the anatomical 3-Tesla MR neurography and the functional diffusion tensor imaging findings of the case, which were subsequently confirmed on surgical excision and histopathology.

Recurrent ulnar nerve entrapment at the elbow: Correlation of surgical findings and 3-Tesla magnetic resonance neurography.

The authors describe the correlation between 3-Tesla magnetic resonance neurography (MRN) and surgical findings in two patients who underwent multiple previous failed ulnar nerve surgeries. MRN correctly localized the site of the abnormality. Prospectively observed MRN findings of perineural fibrosis, ulnar nerve re-entrapment abnormalities, medial antebrachial cutaneous neuroma and additional median nerve entrapment were confirmed surgically.

Les auteurs décrivent la corrélation entre la neurographie par résonance magnétique (NRM) 3-Tesla et les observations chirurgicales chez deux patients qui avaient déjà subi plusieurs opérations non réus-sies du nerf cubital. La NRM a permis de déterminer le foyer de l'anomalie. Les observations prospectives des résultats de la NRM faisant foi d'une fibrose périneurale, d'anomalies de recompression du nerf cubital, d'un névrome cutané de la partie médiale de l'avant-bras et d'une compression supplémentaire du nerf médian ont été confirmées lors de l'opération.

Spectrum of high-resolution MRI findings in diabetic neuropathy.

OBJECTIVE: Diabetes is the most common cause of neuropathy. Focal diabetic neuropathy, although less common than entrapment neuropathy, clinically mimics entrapment neuropathy. This article depicts the spectrum of MR abnormalities in diabetic subjects- from abnormal T2 hyperintensity and fascicular enlargement in the acute and subacute stages to atrophic-appearing fascicles with intraepineurial fat deposition in the chronic stage-on high-resolution high-field (3-T) MRI. CONCLUSION: A spectrum of imaging abnormalities is observed in diabetic neuropathy. It is important for radiologists to understand the pathophysiology and recognize high-resolution MR appearances of these lesions and of related entities in the differential diagnosis for appropriate diagnosis and patient treatment.

Imaging the postoperative spine.

Imaging assessment of the postoperative spine is complex and depends on many factors. Postoperative imaging studies evaluate the position of implants, adequacy of decompression, fusion status, and potential complications. This article provides a review of various imaging techniques, with their advantages and disadvantages, for the evaluation of the postoperative spine. It also gives an overview of normal and abnormal postoperative appearances of the spine as seen via various modalities, with an emphasis on postoperative complications.

Current perspectives on the advantages of 3-T MR imaging of the wrist.

The use of 3-T magnetic resonance (MR) imaging systems with improved coil designs and high-resolution MR imaging sequences allows visualization of the musculoskeletal anatomy in exquisite detail and accurate characterization of abnormalities both in soft tissues and in bone. Current high-field-strength MR systems offer particular advantages for diagnostic imaging of the small joints of the extremities, especially the wrists, where multiple overlapping soft-tissue structures may be visually inseparable at lower field strengths because of limited contrast resolution. Diagnostic accuracy obtained with 3-T MR imaging of the wrist performed with an acquisition protocol that includes three-dimensional and proton density-weighted imaging sequences is nearly commensurate with that obtained with MR arthrography. Abnormalities of the ligaments, tendons, cartilage, nerves, blood vessels, and bone are clearly depicted, allowing accurate characterization of perforations, tears, and fractures, as well as various soft-tissue and intraosseous lesions (eg, ganglion cysts), vascular malformations, aneurysms, and neuropathies.

Sciatic nerve tumor and tumor-like lesions - uncommon pathologies.

Sciatic nerve mass-like enlargement caused by peripheral nerve sheath tumors or neurocutaneous syndromes such as neurofibromatosis or schwannomatosis has been widely reported. Other causes of enlargement, such as from perineuroma, fibromatosis, neurolymphoma, amyloidosis, endometriosis, intraneural ganglion cyst, Charcot-Marie-Tooth disease, and chronic inflammatory demyelinating polyneuropathy are relatively rare. High-resolution magnetic resonance imaging (MRI) is an excellent non-invasive tool for the evaluation of such lesions. In this article, the authors discuss normal anatomy of the sciatic nerve and MRI findings of the above-mentioned lesions.

Cartilage magnetic resonance imaging techniques at 3 T: current status and future directions.

Magnetic resonance imaging (MRI) remains the imaging modality of choice for morphological and compositional evaluation of the articular cartilage. Accurate detection and characterization of cartilage lesions are necessary to guide the medical and surgical therapy and are also critical for longitudinal studies of the cartilage. Recent work using 3.0-T MRI systems shows promise in improving detection and characterization of the cartilage lesions, particularly with increasing use of high-resolution and high-contrast 3-dimensional sequences, which allow detailed morphological assessment of cartilage in arbitrary imaging planes. In addition, implementation of biochemical sequences in clinically feasible scan times has a potential in the early detection of cartilage lesions before they become morphologically apparent. This article discusses relative advantages and disadvantages of various commonly used as well as experimental MRI techniques to directly assess the morphology and indirectly evaluate the biochemical composition of the articular cartilage.