Radiological abnormalities in progressive multifocal leukoencephalopathy: Identifying typical and atypical imaging patterns for early diagnosis and differential considerations.

Progressive multifocal leukoencephalopathy (PML) is a rare viral central nervous system (CNS) demyelinating disease primarily associated with a compromised immune system. PML is seen mainly in individuals with human immunodeficiency virus, lymphoproliferative disease, and multiple sclerosis. Patients on immunomodulators, chemotherapy, and solid organ or bone marrow transplants are predisposed to PML. Recognition of various PML-associated typical and atypical imaging abnormalities is critical for early diagnosis and differentiating it from other conditions, especially in high-risk populations. Early PML recognition should expedite efforts at immune-system restoration, allowing for a favorable outcome. This review aims to provide a practical overview of radiological abnormalities in PML patients and address differential considerations.

Multimodality imaging of neurodegenerative disorders with a focus on multiparametric magnetic resonance and molecular imaging.

Neurodegenerative diseases afflict a large number of persons worldwide, with the prevalence and incidence of dementia rapidly increasing. Despite their prevalence, clinical diagnosis of dementia syndromes remains imperfect with limited specificity. Conventional structural-based imaging techniques also lack the accuracy necessary for confident diagnosis. Multiparametric magnetic resonance imaging and molecular imaging provide the promise of improving specificity and sensitivity in the diagnosis of neurodegenerative disease as well as therapeutic monitoring of monoclonal antibody therapy. This educational review will briefly focus on the epidemiology, clinical presentation, and pathologic findings of common and uncommon neurodegenerative diseases. Imaging features of each disease spanning from conventional magnetic resonance sequences to advanced multiparametric methods such as resting-state functional magnetic resonance imaging and arterial spin labeling imaging will be described in detail. Additionally, the review will explore the findings of each diagnosis on molecular imaging including single-photon emission computed tomography and positron emission tomography with a variety of clinically used and experimental radiotracers. The literature and clinical cases provided demonstrate the power of advanced magnetic resonance imaging and molecular techniques in the diagnosis of neurodegenerative diseases and areas of future and ongoing research. With the advent of combined positron emission tomography/magnetic resonance imaging scanners, hybrid protocols utilizing both techniques are an attractive option for improving the evaluation of neurodegenerative diseases.

Clinical performance of a multiparametric MRI-based post concussive syndrome index.

Introduction: Diffusion Tensor Imaging (DTI) has revealed measurable changes in the brains of patients with persistent post-concussive syndrome (PCS). Because of inconsistent results in univariate DTI metrics among patients with mild traumatic brain injury (mTBI), there is currently no single objective and reliable MRI index for clinical decision-making in patients with PCS. Purpose: This study aimed to evaluate the performance of a newly developed PCS Index (PCSI) derived from machine learning of multiparametric magnetic resonance imaging (MRI) data to classify and differentiate subjects with mTBI and PCS history from those without a history of mTBI. Materials and methods: Data were retrospectively extracted from 139 patients aged between 18 and 60 years with PCS who underwent MRI examinations at 2 weeks to 1-year post-mTBI, as well as from 336 subjects without a history of head trauma. The performance of the PCS Index was assessed by comparing 69 patients with a clinical diagnosis of PCS with 264 control subjects. The PCSI values for patients with PCS were compared based on the mechanism of injury, time interval from injury to MRI examination, sex, history of prior concussion, loss of consciousness, and reported symptoms. Results: Injured patients had a mean PCSI value of 0.57, compared to the control group, which had a mean PCSI value of 0.12 (p = 8.42e-23) with accuracy of 88%, sensitivity of 64%, and specificity of 95%, respectively. No statistically significant differences were found in the PCSI values when comparing the mechanism of injury, sex, or loss of consciousness. Conclusion: The PCSI for individuals aged between 18 and 60 years was able to accurately identify patients with post-concussive injuries from 2 weeks to 1-year post-mTBI and differentiate them from the controls. The results of this study suggest that multiparametric MRI-based PCSI has great potential as an objective clinical tool to support the diagnosis, treatment, and follow-up care of patients with post-concussive syndrome. Further research is required to investigate the replicability of this method using other types of clinical MRI scanners.

Intracranial Abnormalities with Diffusion Restriction.

Multiple pathologic conditions can cause changes in the random movement of water, which can be detected with diffusion-weighted imaging (DWI). DWI plays a powerful clinical role in detecting restricted diffusion associated with acute brain infarction. Other disorders can also result in restricted diffusion. This article focuses on showing examples of common and uncommon disorders that have restricted diffusion secondary to cytotoxic and/or intramyelinic edema. These disorders include ischemia, infection, noninfectious demyelinating diseases, genetic mutations affecting metabolism, acquired metabolic disorders, toxic or drug exposures, neoplasms and tumorlike lesions, radiation treatment, trauma, and denervation.

Post-concussive mTBI in Student Athletes: MRI Features and Machine Learning.

Purpose: To determine and characterize the radiomics features from structural MRI (MPRAGE) and Diffusion Tensor Imaging (DTI) associated with the presence of mild traumatic brain injuries on student athletes with post-concussive syndrome (PCS). Material and Methods: 122 student athletes (65 M, 57 F), median (IQR) age 18.8 (15-20) years, with a mixed level of play and sports activities, with a known history of concussion and clinical PCS, and 27 (15 M, 12 F), median (IQR) age 20 (19, 21) years, concussion free athlete subjects were MRI imaged in a clinical MR machine. MPRAGE and DTI-FA and DTI-ADC images were used to extract radiomic features from white and gray matter regions within the entire brain (2 ROI) and the eight main lobes of the brain (16 ROI) for a total of 18 analyzed regions. Radiomic features were divided into five different data sets used to train and cross-validate five different filter-based Support Vector Machines. The top selected features of the top model were described. Furthermore, the test predictions of the top four models were ensembled into a single average prediction. The average prediction was evaluated for the association to the number of concussions and time from injury. Results: Ninety-one PCS subjects passed inclusion criteria (91 Cases, 27 controls). The average prediction of the top four models had a sensitivity of 0.80, 95% CI: [0.71, 0.88] and specificity of 0.74 95%CI [0.54, 0.89] for distinguishing subjects from controls. The white matter features were strongly associated with mTBI, while the whole-brain analysis of gray matter showed the worst association. The predictive index was significantly associated with the number of concussions (p < 0.0001) and associated with the time from injury (p < 0.01). Conclusion: MRI Radiomic features are associated with a history of mTBI and they were successfully used to build a predictive machine learning model for mTBI for subjects with PCS associated with a history of one or more concussions.

Domain-Specific Diaschisis: Lesions to Parietal Action Areas Modulate Neural Responses to Tools in the Ventral Stream.

Neural responses to small manipulable objects ("tools") in high-level visual areas in ventral temporal cortex (VTC) provide an opportunity to test how anatomically remote regions modulate ventral stream processing in a domain-specific manner. Prior patient studies indicate that grasp-relevant information can be computed about objects by dorsal stream structures independently of processing in VTC. Prior functional neuroimaging studies indicate privileged functional connectivity between regions of VTC exhibiting tool preferences and regions of parietal cortex supporting object-directed action. Here we test whether lesions to parietal cortex modulate tool preferences within ventral and lateral temporal cortex. We found that lesions to the left anterior intraparietal sulcus, a region that supports hand-shaping during object grasping and manipulation, modulate tool preferences in left VTC and in the left posterior middle temporal gyrus. Control analyses demonstrated that neural responses to "place" stimuli in left VTC were unaffected by lesions to parietal cortex, indicating domain-specific consequences for ventral stream neural responses in the setting of parietal lesions. These findings provide causal evidence that neural specificity for "tools" in ventral and lateral temporal lobe areas may arise, in part, from online inputs to VTC from parietal areas that receive inputs via the dorsal visual pathway.

Malformed vertebrae: a clinical and imaging review.

A variety of structural developmental anomalies affect the vertebral column. Malformed vertebrae can arise secondary to errors of vertebral formation, fusion and/or segmentation and developmental variation. Malformations can be simple with little or no clinical consequence, or complex with serious structural and neurologic implications. These anomalies can occasionally mimic acute trauma (bipartite atlas versus Jefferson fracture, butterfly vertebra versus burst fracture), or predispose the affected individual to myelopathy. Accurate imaging interpretation of vertebral malformations requires knowledge of ageappropriate normal, variant and abnormal vertebral morphology and the clinical implications of each entity. This knowledge will improve diagnostic confidence in acute situations and confounding clinical scenarios.This review article seeks to familiarize the reader with the embryology, normal and variant anatomy of the vertebral column and the imaging appearance and clinical impact of the spectrum of vertebral malformations arising as a consequence of disordered embryological development.Teaching points • Some vertebral malformations predispose the affected individual to trauma or myelopathy. • On imaging, malformed vertebrae can be indistinguishable from acute trauma. • Abnormalities in spinal cord development may be associated and must be searched for. • Accurate interpretation requires knowledge of normal, variant and abnormal vertebral morphology.

Mechanical birth-related trauma to the neonate: An imaging perspective.

Mechanical birth-related injuries to the neonate are declining in incidence with advances in prenatal diagnosis and care. These injuries, however, continue to represent an important source of morbidity and mortality in the affected patient population. In the United States, these injuries are estimated to occur among 2.6% of births. Although more usual in context of existing feto-maternal risk factors, their occurrence can be unpredictable. While often superficial and temporary, functional and cosmetic sequelae, disability or even death can result as a consequence of birth-related injuries. The Agency for Healthcare research and quality (AHRQ) in the USA has developed, through expert consensus, patient safety indicators which include seven types of birth-related injuries including subdural and intracerebral hemorrhage, epicranial subaponeurotic hemorrhage, skeletal injuries, injuries to spine and spinal cord, peripheral and cranial nerve injuries and other types of specified and non-specified birth trauma. Understandably, birth-related injuries are a source of great concern for the parents and clinician. Many of these injuries have imaging manifestations. This article seeks to familiarize the reader with the clinical spectrum, significance and multimodality imaging appearances of neonatal multi-organ birth-related trauma and its sequelae, where applicable. Teaching points • Mechanical trauma related to birth usually occurs with pre-existing feto-maternal risk factors.• Several organ systems can be affected; neurologic, musculoskeletal or visceral injuries can occur.• Injuries can be mild and transient or disabling, even life-threatening.• Imaging plays an important role in injury identification and triage of affected neonates.

The cingulate cortex of older adults with excellent memory capacity.

Memory deterioration is the earliest and most devastating cognitive deficit in normal aging and Alzheimer's disease (AD). Some older adults, known as "Supernormals", maintain excellent memory. This study examined relationships between cerebral amyloid deposition and functional connectivity (FC) within the cingulate cortex (CC) and between CC and other regions involved in memory maintenance between Supernormals, healthy controls (HC), and those at risk for AD (amnestic mild cognitive impairment [MCI]). Supernormals had significantly stronger FC between anterior CC and R-hippocampus, middle CC (MCC) and L-superior temporal gyrus, and posterior CC (PCC) and R-precuneus, while weaker FC between MCC and R-middle frontal gyrus and MCC and R-thalamus than other groups. All of these FC were significantly related to memory and global cognition in all participants. Supernormals had less amyloid deposition than other groups. Relationships between global cognition and FC were stronger among amyloid positive participants. Relationships between memory and FC remained regardless of amyloid level. This revealed how CC-related neural function participates in cognitive maintenance in the presence of amyloid deposition, potentially explaining excellent cognitive function among Supernormals.

Lesions involving the outer surface of the bone in children: a pictorial review.

BACKGROUND: Lesions involving the outer cortical surface of the bone occur quite often among children. Broadly, these include benign cortical, juxtacortical and periarticular lesions, dysplasias affecting the cortical bone, regional and diffuse periosteal pathology and malignant tumours. Some of these lesions are unique to the paediatric population; others are more frequently seen among children than adults - yet others have an adult predilection but can occasionally be seen in children. METHODS: A complete list of differential considerations for lesions involving the outer cortical surface of the bone in children is presented. Imaging characteristics on plain film radiography and MR are described in association with multiple examples and illustrations. CONCLUSION: A pictorial review detailing the imaging features of surface lesions of the bone in children will be a useful aide for both radiologists and their clinical colleagues, and will help them sort their way through the maze of differential diagnoses for these abnormalities. Teaching Points • Surface lesions of bones in children comprise a distinct entity and differ from those in adults. • Imaging plays an important role towards classifying surface lesions of bones in children. • MRI features may be characteristic and aid precise diagnosis, thus guiding further management.

Multiparametric Magnetic Resonance Imaging of Recurrent Prostate Cancer.

Multiparametric magnetic resonance (MR) imaging of the prostate combines both morphological and functional MR techniques by utilizing small field of view T1-weighted, T2-weighted, diffusion-weighted imaging, dynamic contrast-enhanced imaging, and MR spectroscopy to accurately detect, localize, and stage primary and recurrent prostate cancer. Localizing the site of recurrence in patients with rising prostate-specific antigen following treatment affects decision making regarding treatment and can be accomplished with multiparametric prostate MR. Several different treatment options are available for prostate cancer including radical prostatectomy, external beam radiation therapy, brachytherapy, androgen deprivation therapy, or a number of focal therapy techniques. The findings of recurrent prostate cancer can be different depending on the treatment the patient has received, and the radiologist must be able to recognize the variety of imaging findings seen with this common disease. This review article will detail the findings of recurrent prostate cancer on multiparametric MR and describe common posttreatment changes which may create challenges to accurate interpretation.

Magnetic resonance imaging of pineal region tumours.

OBJECTIVES: Pineal lesions can present as a heterogeneous collection of benign and malignant disease conditions. Pineal lesions include germ cell tumours, neoplasms arising from the pineal parenchyma, as well as other pineal region masses. METHODS: A variety of cases of pineal lesions are presented. The important clinical features and typical imaging findings of each pineal lesion are described with emphasis on their morphological appearance and signal intensity characteristics on magnetic resonance imaging (MRI). CONCLUSION: Knowledge of the imaging characteristics and clinical features of varying pineal lesions can assist in narrowing the differential diagnosis for more accurate and rational therapeutic planning. TEACHING POINTS: • Pineal parenchymal tumours show an "explosion" of normal pineal calcifications towards the periphery. • Pineoblastomas often have restricted diffusion, with apparent diffusion coefficient (ADC) values lower than germinomas. • Pineal teratomas and pineal lipomas display fat signal characteristics and fat saturation on MRI. • Pineal lesions in patients with known malignancy should raise suspicion of metastatic involvement. • Pineal cysts and arachnoid cysts show MRI signal characteristics similar to cerebrospinal fluid (CSF).

Intracranial lesions with high signal intensity on T1-weighted MR images: differential diagnosis.

Various substances, including methemoglobin, melanin, lipid, protein, calcium, iron, copper, and manganese, are responsible for the intrinsically high signal intensity observed in intracranial lesions at T1-weighted magnetic resonance (MR) imaging. Many of these substances have physical properties that lead to other specific imaging features as well. For example, lipid-containing lesions frequently produce chemical shift artifact, and some melanin-containing lesions exhibit a combination of high signal intensity on T1-weighted images and low signal intensity on T2-weighted images. The location and extent of a region of abnormal signal hyperintensity may be helpful for identifying rare diseases such as an ectopic posterior pituitary gland near the floor of the third ventricle, bilateral involvement of the dentate and lentiform nuclei in Cockayne syndrome, and involvement of the anterior temporal lobe and cerebellum in neurocutaneous melanosis. In cases in which diagnostically specific T1-weighted imaging features are lacking, findings obtained with other MR pulse sequences and other modalities can help narrow the differential diagnosis: An elevated glutamine or glutamate level at MR spectroscopy is suggestive of hepatic encephalopathy; a popcorn ball-like appearance at T2-weighted imaging, of cavernous malformations; and hyperattenuation at computed tomography, of mineral deposition disease. In many cases, a comparison of imaging features with clinical measures enables a specific diagnosis.

Hemorrhage of a cavernous malformation associated with accidental electrocution: Case report and review of the literature.

BACKGROUND: Cavernous malformations (CMs) are the second most common intracranial vascular lesions. They typically present after hemorrhage or as incidental findings. Several risk factors have been identified for hemorrhage, however, electrocution as a cause has not been described. We performed a literature review of electrocution associated with CM hemorrhage and of the mechanisms of pathological injury in the central nervous system (CNS) secondary to electrocution. We found no cases of hemorrhage of CMs associated with electrocution. CASE DESCRIPTION: A 19-year-old male electrician was accidentally electrocuted with 277 V of alternating current (AC) at a job site. He suffered no trauma or physical injuries and reported no immediate abnormal findings. He then experienced progressive nausea, emesis, and lethargy until he presented to the emergency department (ED) where it was discovered that he had a left thalamic/midbrain hemorrhage with hydrocephalus. His hydrocephalus was treated and he began to improve. Subsequent magnetic resonance imaging (MRI) of his head demonstrated characteristic features of a CM. CONCLUSIONS: There are several proposed mechanisms in the literature by which electrocution may cause CNS damage. It is conceivable that given the pathology of CMs and the proposed mechanisms of electrical injury, these lesions may have an increased risk of hemorrhage as result of electrocution and we are reporting the first case of such an association.

Merkel cell carcinoma of the foot: case report and review of the literature.

Merkel cell carcinomas are rare neuroendocrine tumors of the skin with highly malignant behavior. These tumors arise from Merkel cells, which are slowly adapting type 1 mechanoreceptors that occur in hair follicles and the basal layer of the epidermis. Merkel cell carcinomas are typically located in the dermis and frequently extend into the subcutaneous fat and lymphatics. This case report describes the magnetic resonance imaging and pathologic findings, surgical treatment, and postoperative results with review of the literature for Merkel cell carcinoma involving the foot of a 72-year-old man with a 2-month history of a painless, enlarging mass that interfered with his ability to wear a shoe.

Neurothekeoma in the upper extremity: magnetic resonance imaging and computed tomography findings.

Neurothekeomas are rare benign tumors of soft tissue that are of presumed neural sheath origin. This report describes the magnetic resonance imaging and computed tomography features of a neurothekeoma in the left forearm of a 38-year-old woman with a 2-year history of a painful mass. Magnetic resonance imaging showed a smooth-bordered ovoid lesion within the inner portion of the extensor digitorum muscle with a Hounsfield number of 15. The lesion had intermediate signal on T1-weighted images, high signal on T2-weighted images, and mild to moderate heterogeneous gadolinium contrast enhancement.

Choroid plexus carcinomas in children: MRI features and patient outcomes.

Choroid plexus carcinomas (CPC) are rare malignant intracranial neoplasms usually occurring in young children. The objectives of this study were to characterize the preoperative MRI features of CPC, determine the frequency of disseminated disease in the CNS at diagnosis, and assess patient outcomes. The preoperative cranial MR images of 11 patients with CPC were retrospectively reviewed for lesion location, lesion size, un-enhanced and enhanced MRI signal characteristics, and presence of disseminated intracranial tumor. Postoperative cranial and spinal MRI images were reviewed for residual, recurrent, and/or disseminated tumor. The study group included six male and five female patients ranging in age from 5 months to 5.3 years (median= 1.8 years). CPC were located in the lateral (n = 8), fourth (n = 1), and third (n = 1) ventricles, and foramen of Luschka (n = 1). Mean tumor size was 5.2 cm x 4.9 cm x 5.0 cm. On short-TR images, CPC had heterogeneous, predominantly intermediate signal with foci of high signal in 45% of lesions from areas of hemorrhage. On long-TR/long-TE images, solid portions of CPC typically had heterogeneous, intermediate-to-slightly-high signal. Small zones of low signal on long-TR/long-TE images were seen in 55% of the lesions secondary to areas of hemorrhage and/or calcifications. Tubular flow voids representing blood vessels were seen in 55% of the lesions. Zones of high signal comparable to CSF were seen in 64% of CPC secondary to cystic/necrotic zones. All CPC showed prominent contrast enhancement. Irregular enhancing margins suggesting subependymal invasion were seen in 73% of the lesions. Findings consistent with edema in the brain adjacent to the enhancing lesions were seen in 73% of CPC. CPC caused hydrocephalus in 82% of patients at diagnosis. Two patients died from hemorrhagic complications from surgical biopsies. Disseminated tumor in the leptomeninges was present in 45% of patients at diagnosis and was associated with a poor prognosis. The 1-year and 5-year survival probabilities were 55% and 45%, respectively. In conclusion, MRI features commonly associated with CPC include large intraventricular lesions with irregular enhancing margins; heterogeneous signal on long TR/long TE images and short-TR images; edema in adjacent brain; hydrocephalus; and presence of disseminated tumor. MRI evidence of disseminated tumor at diagnosis is associated with a poor prognosis.