Current and Future Challenges of Functional MRI and Diffusion Tractography in the Surgical Setting: From Eloquent Brain Mapping to Neural Plasticity.

Decades ago, Spetzler (1986) and Sawaya (1998) provided a rough brain segmentation of the eloquent areas of the brain, aimed to help surgical decisions in cases of vascular malformations and tumors, respectively. Currently in clinical use, their criteria are in need of revision. Defining functions (eg, sensorimotor, language and visual) that should be preserved during surgery seems a straightforward task. In practice, locating the specific areas that could cause a permanent vs transient deficit is not an easy task. This is particularly true for the associative cortex and cognitive domains such as language. The old model, with Broca's and Wernicke's areas at the forefront, has been superseded by a dual-stream model of parallel language processing; named ventral and dorsal pathways. This complicated network of cortical hubs and subcortical white matter pathways needing preservation during surgery is a work in progress. Preserving not only cortical regions but most importantly preserving the connections, or white matter fiber bundles, of core regions in the brain is the new paradigm. For instance, the arcuate fascicululs and inferior fronto-occipital fasciculus are key components of the dorsal and ventral language pathways, respectively; and their damage result in permanent language deficits. Interestedly, the damage of the temporal portions of these bundles -where there is a crossroad with other multiple bundles-, appears to be more important (permanent) than the damage of the frontal portions - where plasticity and contralateral activation could help. Although intraoperative direct cortical and subcortical stimulation have contributed largely, advanced MR techniques such as functional MRI (fMRI) and diffusion tractography (DT), are at the epi-center of our current understanding. Nevertheless, these techniques posse important challenges: such as neurovascular uncoupling or venous bias on fMRI; and appropriate anatomical validation or accurate representation of crossing fibers on DT. These limitations should be well understood and taken into account in clinical practice. Unifying multidisciplinary research and clinical efforts is desirable, so these techniques could contribute more efficiently not only to locate eloquent areas but to improve outcomes and our understanding of neural plasticity. Finally, although there are constant anatomical and functional regions at the individual level, there is a known variability at the inter-individual level. This concept should strengthen the importance of a personalized approach when evaluating these regions on fMRI and DT. It should strengthen the importance of personalized treatments as well, aimed to meet tailored needs and expectations.

Positive Impact of Professionalism on the Perception of Global Well-Being: A Study in Healthcare Professionals Starting Their First Working Experience in Peruvian Rural Areas.

Introduction: In Peru, recently graduated physicians and nurses who are willing to start working in the public healthcare system, first have to work in their newly acquired profession in the programme denominated "Servicio Rural Urbano y Marginal de Salud" (SERUMS). The SERUMS programme is a 1-year contract in rural areas of the country. The aim of this study was to confirm the following hypothesis: the development of abilities associated to professionalism has a positive effect on the perception of global well-being in the professionals beginning SERUMS. Material and methods: In the study two cohorts of medical and nursing professionals that started SERUMS in 2017 and 2019 were included. The perception of global well-being and general health condition were measured with the Scale of Life Satisfaction (SWLS) and the General Health Questionnaire (GHQ-28), respectively. Professionalism was measured using Jefferson's scales of empathy (JSE), teamwork (JSAPNC), and lifelong learning (JeffSPLL). An analysis in phases using the R language was applied to develop a multiple regression model that would explain the lineal relationship between the global perception of well-being and the studied variables. Results: The study sample included 303 professionals (108 men and 195 women) with a mean age of 26 years, ranging from 22 to 39 years (SD = 4). Based on their profession, 230 were medical doctors and 67 were nurses. The multiple regression model evidenced that age (p < 0.001), social dysfunction (p < 0.001), severe depression (p < 0.001), and inter-professional collaborative work abilities (p < 0.001) explain 38% of the variability in the global perception of well-being. Moreover, a second model explained 44% of the variability in the inter-professional collaborative work abilities based on a lineal relationship with empathy (p < 0.001), lifelong learning (p < 0.001), and future professional orientation (p = 0.01). Both models complied with the necessary conditions for statistic inference and showed large effect sizes. Conclusions: These findings confirm that professionalism has an important role in improving the global well-being of the professionals initiating SERUMS. This influence is direct in the case of inter-professional collaborative work, whereas it is indirect in the case of empathy and lifelong learning.

Infectious Spondylitis Mimics: Mechanisms of Disease and Imaging Findings.

Infectious processes of the spine are on the rise; in this scenario recognition of entities imitating infection is very important. The discovertebral unit is regarded as one of the most important and active sites in the spine. Importantly, the vertebral bony rim and the anterior corners of the vertebral bodies have significant vascularization, they are the last regions to ossify in the developmental process and suffer mechanical forces. Early septic or aseptic discitis-osteomyelitis, properly called spondylitis, involves these anterior regions. Early degeneration is characterized by disc desiccation; however, there is preferential involvement for the corners of the vertebral bodies as well. Many entities to include degenerative changes, inflammatory spondyloarthropathies, neuropathic spine, or pseudo arthrosis, among others, affect the discovertebral unit and can imitate infection. With some exceptions, important imaging findings for the identification of an infectious mimic include the absence of soft tissue enhancement or fluid collections in the paraspinal or epidural regions, and the involvement of multiple levels or the posterior elements. We review developmental, anatomical, and pathologic concepts correlating with imaging clues. Overall, our goal is to increase awareness and to improve recognition of mimicking entities.

Stroke Mimics: The Quest for Leptomeningeal Anastomoses and Isolated Diffusion-Weigthed MR Signal.

Stroke is caused by occlusion of a medium- or large-sized vessel in the brain. The treatment with either intravenous or intra-arterial thrombolysis is based on an accurate and time-sensitive diagnosis. On clinical and imaging grounds a number of entities-seizures, toxic-metabolic, infectious, or demyelinating diseases-can mimic stroke. Identifying them is paramount as the treatment differs significantly. Prior imaging reviews have focused on the nonterritorial distribution of these mimics. However, some important questions arise here. Are the vascular territories and their boundaries invariable in the human brain? Where should we draw the lines separating arterial territories? van der Zwan and colleagues addressed these questions decades ago. For him and others, the leptomeningeal anastomoses-a contentious concept for some but increasingly linked to collateral flow in stroke-is an important anatomic structure with significant variations in their distribution and pathophysiology. Variations in blood supply appear larger that traditionally taught. We revisit this concept and entertained their implications in cases of stroke mimics. For instance, the distribution of abnormalities in some toxic-metabolic processes appear to correlate with areas where rich leptomeningeal anastomoses are expected. We will also explore the concept of hyperintense signal on diffusion weighted-imaging with no correlated changes on apparent diffusion coefficient maps. We name this finding as "isolated DWI signal" and lay-out its importance in the recognition of many entities mimicking stroke. Taking together, the discussed anatomic and imaging concepts will help radiologists and clinicians to recognize not only the common but the unusual entities imitating stroke in the emergency room.

Pitfalls in the Imaging Interpretation of Intracranial Hemorrhage.

Intracranial hemorrhage (ICH) is one of the most common pathologic findings in the emergent computed tomography (CT) imaging. ICH presents as hyperattenuation in parenchymal, subarachnoid, subdural, or epidural location. However, the initial interpretation of areas of hyperattenuation can be challenging as other pathologic or nonpathologic processes (eg, calcifications, vascular malformations, highly cellular tumors, iodinated contrast, or beam-hardening artifacts) can have similar appearance. ICH can also present as isoattenuation on CT, being difficult to distinguish from the brain parenchyma. Dual-energy CT can separate hemorrhage from other causes of hyperattenuation. Albeit, this type of technology has limited availability. Pitfalls on magnetic resonance imaging (MRI) are possible but less common. The characterization of hemorrhage on conventional MR sequences, and particularly on gradient recall echo or susceptibility-weighted imaging is improved. Thus, MRI is considered a problem-solving technique. Radiologists have a prominent role in the interpretation of the initial head CT, recognizing potential pitfalls or alternative diagnosis and if necessary recommending additional work-up. Key imaging findings and technical considerations in common and uncommon pitfalls of ICH are reviewed here.

Comparison of normal facial nerve enhancement at 3T MRI using gadobutrol and gadopentetate dimeglumine.

Background and purpose The facial nerve is unique among cranial nerves in demonstrating normal enhancement of particular segments. The effect of varying T1 relaxivities of gadolinium-based contrast agents on facial nerve enhancement is unclear. In this study, we assess differences in normal facial nerve enhancement with two different gadolinium-based contrast agents, gadobutrol and gadopentetate dimeglumine. In addition, we evaluate differences in facial nerve enhancement with spin-echo (SE) T1 versus 3D inversion recovery prepared fast spoiled gradient-echo (FSPGR) post-contrast sequences. Methods A total of 140 facial nerves in 70 individuals were evaluated (70 with gadobutrol and 70 with gadopentetate dimeglumine) by two blinded reviewers. Differences in enhancement of facial nerve segments between the two agents were analyzed. Differences in enhancement between SE T1 and FSPGR imaging were also evaluated. Results There was no significant difference in facial nerve enhancement between gadobutrol and gadopentetate dimeglumine. Enhancement was commonly observed in the geniculate, tympanic and mastoid segments (98%-100%) with either contrast agent; enhancement was less common in the labyrinthine segments (9%-14%) and lateral canalicular segment (2%-5%). There was a smaller enhancing proportion of labyrinthine and tympanic segments with FSPGR as compared to SE T1 images with gadobutrol. Conclusion There is no significant difference in overall enhancement of the facial nerve between gadobutrol and gadopentetate dimeglumine. Mild enhancement of the lateral canalicular portion of the facial nerve may be a normal finding. With FSPGR sequence, there is lesser perceived enhancement of the labyrinthine and tympanic segments of the facial nerve with gadobutrol.

Variable MR and pathologic patterns of hemorrhage after iodinated contrast infusion in MCA occlusion/reperfusion model.

OBJECTIVE: To examine the hypothesis that IA reperfusion with iso-osmolar iodixanol, low-osmolar iopamidol, or saline causes different effects on MR signal changes and pathologic cut-brain section related to hemorrhagic transformation (HT) or iodinated radiographic contrast media (IRCM) deposition. METHODS: Infarct was induced in 30 rats by middle cerebral artery suture occlusion. Reperfusion was performed after 5 hours with iso-osmolar iodixanol (n=9), low-osmolar iopamidol (n=12) or saline (n=9). MR images were obtained immediately after reperfusion and rats were sacrificed at 24 hours. Hypointense areas within the infarction on T2-weighted (T2-WI) or gradient echo (GRE) images were recorded and compared with HT on pathology. Fisher's exact test was used for proportions, and receiver operator curve analysis to evaluate MRI discrimination of hemorrhage. RESULTS: Two types of HT were noted on pathology: confluent >0.2 mm petechial hemorrhage (PeH, 78%) or well-defined ≤0.2 mm hemorrhagic focus (HF, 22%). PeH was least common in the iodixanol subgroup (p<0.02). HF was more common in the IRCM group. Hypointense areas on T2-WI but not on GRE were significantly more common in the IRCM group (p<0.05). Hypointense areas on T2-WI and GRE discriminated HT (area under the curve: 0.714, p<0.002). CONCLUSIONS: IRCM and saline induced different MRI signal and pathologic patterns in our sample. We postulate that T2 hypointensity with no GRE hypointensity might be associated with IRCM deposition; and decreased frequency of PeH after iodixanol infusion and the presence of HF almost exclusively in the IRCM group might represent a direct/indirect effect of contrast infusion/deposition in the brain parenchyma after reperfusion. Our results support previous observations in IMS III and are hypothesis generating.

Vascular Diseases of the Spinal Cord: Infarction, Hemorrhage, and Venous Congestive Myelopathy.

Vascular pathologies of the spinal cord are rare and often overlooked. This article presents clinical and imaging approaches to the diagnosis and management of spinal vascular conditions most commonly encountered in clinical practice. Ischemia, infarction, hemorrhage, aneurysms, and vascular malformations of the spine and spinal cord are discussed. Pathophysiologic mechanisms, clinical classification schemes, clinical presentations, imaging findings, and treatment modalities are considered. Recent advances in genetic and syndromic vascular pathologies of the spinal cord are also discussed. Clinically relevant spinal vascular anatomy is reviewed in detail.

Spinal Cord Anatomy and Clinical Syndromes.

We review the anatomy of the spinal cord, providing correlation with key functional and clinically relevant neural pathways, as well as magnetic resonance imaging. Peripherally, the main descending (corticospinal tract) and ascending (gracilis or cuneatus fasciculi and spinothalamic tracts) pathways compose the white matter. Centrally, the gray matter can be divided into multiple laminae. Laminae 1-5 carry sensitive neuron information in the posterior horn, and lamina 9 carries most lower motor neuron information in the anterior horn. Damage to the unilateral corticospinal tract (upper motor neuron information) or gracillis-cuneatus fasciculi (touch and vibration) correlates with ipsilateral clinical findings, whereas damage to unilateral spinothalamic tract (pain-temperature) correlates with contralateral clinical findings. Damage to commissural fibers correlates with a suspended bilateral "girdle" sensory level. Autonomic dysfunction is expected when there is bilateral cord involvement.

Abnormal Spinal Cord Magnetic Resonance Signal: Approach to the Differential Diagnosis.

T2-hyperintense signal abnormalities within the spinal cord on magnetic resonance imaging can evoke a broad differential diagnosis and can present a diagnostic dilemma. Here, we review and provide a succinct and relevant differential diagnosis based on imaging patterns and anatomical or physiopathologic correlation. Clues and imaging pearls are provided focusing on inflammatory, infectious, demyelinating, vascular, and metabolic involvement of the spinal cord.

Effects of iodinated contrast on various magnetic resonance imaging sequences and field strength: Implications for characterization of hemorrhagic transformation in acute stroke therapy.

AIM: To characterize the effects of iodinated contrast material (ICM) on magnetic resonance imaging (MRI) comparing different sequences and magnetic fields, with emphasis to similarities/differences with well-known signal characteristics of hemorrhage in the brain. METHODS: Aliquots of iopamidol and iodixanol mixed with normal saline were scanned at 1.5T and 3T. Signal intensity (SI) was measured using similar spin-echo (SE)-T1, SE-T2, gradient-echo (GRE) and fluid-attenuation-inversion-recovery (FLAIR) sequences at both magnets. Contrast to noise ratio (CNR) (SI contrast-SI saline/SD noise) for each aliquot were calculated and Kruskall-wallis test and graphic analysis was used to compare different pulse sequences and ICMs. RESULTS: Both ICM showed increased SI on SE-T1 and decreased SI on SE-T2, GRE and FLAIR at both 1.5T and 3T, as the concentration was increased. By CNR measurements, SE-T2 had the greatest conspicuity at 3T with undiluted iopamidol (92.6 ± 0.3, P < 0.00) followed by iodixanol (77.5 ± 0.9, P < 0.00) as compared with other sequences (CNR range: 15-40). While SE-T2 had greatest conspicuity at 1.5T with iopamidol (49.3 ± 1, P < 0.01), SE-T1 showed similar or slightly better conspicuity (20.8 ± 4) than SE-T2 with iodixanol (23 ± 1.7). In all cases, hypo-intensity on GRE was less conspicuous than on SE-T2. CONCLUSION: Iodixanol and iopamidol shorten T1 and T2 relaxation times at both 1.5T and 3T. Hypo-intensity due to shortened T2 relaxation time is significantly more conspicuous than signal changes on T1-WI, FLAIR or GRE. Variations in signal conspicuity according to pulse sequence and to type of ICM are exaggerated at 3T. We postulate T2 hypointensity with less GRE conspicuity differentiates ICM from hemorrhage; given the well-known GRE hypointensity of hemorrhage. Described signal changes may be relevant in the setting of recent intra-arterial or intravenous ICM administration in translational research and/or human stroke therapy.

MR imaging findings of endophthalmitis.

Endophthalmitis is a sight-threatening ophthalmologic emergency. The clinical diagnosis is often challenging, and delayed diagnosis may exacerbate the poor visual prognosis. B-scan ultrasonography or spectral domain optical coherence tomography are imaging aids at the clinician's office. Cross-sectional imaging such as CT and particularly MRI can also help in the assessment of disease extent or complications. MR imaging findings are rarely described in the literature. Here, we discuss the spectrum of imaging findings of endophthalmitis and correlate them with key anatomic and pathophysiologic details of the globe. Early disease is often subtle on MR imaging with thick uveal enhancement, while advanced disease demonstrates retinal/choroidal detachment, vitreal exudates and peribulbar inflammation. Other noninfectious inflammatory diseases of the globe can show similar findings; however, MR diffusion-weighted images help identify infectious exudates and evaluate response to therapy. Knowledge of the spectrum of imaging findings of this disease is important for radiologists and help in the management decision process.