Detecting the Uncommon Imaging Manifestations of Posterior Reversible Encephalopathy Syndrome (PRES) in Adults: a Comprehensive Illustrated Guide for the Trainee Radiologist.

Posterior reversible encephalopathy syndrome (PRES) has traditionally been described as a reversible leukoencephalopathy with a distinct pattern of posteriorly distributed vasogenic oedema involving the subcortical regions of parietal and occipital lobes. PRES commonly occurs in the setting of hypertensive emergencies, pre-eclampsia/eclampsia, impaired renal function, and immunosuppressive therapy. The various clinical presentations of PRES include encephalopathy, seizures, headache, visual, and focal neurological deficits. As knowledge of this entity grows, the range of clinical, and radiological features is seen to be much broader than originally described. The brain oedema may not always be posteriorly distributed and the syndrome may not be uniformly reversible. Of special note are some uncommon imaging features (unilateral cerebral involvement, and isolated posterior fossa involvement) and also some uncommon complications (haemorrhage, cytotoxic oedema, and vasoconstriction). These red herrings may lead to potential diagnostic challenges and pitfalls especially for trainee radiologists, who often read these scans in an emergency setting. Early and accurate diagnosis is crucial for prompt optimum management, thereby avoiding residual morbidity. This review article focusses on the atypical radiological features of PRES in adults with extensive case-based imaging examples. A brief description of the pathophysiology, clinical, and classic radiological features of PRES has also been included. A tabulated summary of potential mimics with diagnostic pearls is provided to highlight pertinent take home points and to serve as an easy guide for day-to-day clinical practice.

Pearls and Pitfalls in the Magnetic Resonance Diagnosis of Dural Sinus Thrombosis: A Comprehensive Guide for the Trainee Radiologist.

Dural sinus thrombosis (DST) is a potentially fatal neurological condition that can be reversed with early diagnosis and prompt treatment. Non-enhanced CT scan is often the first imaging investigation in patients presenting with acute neurological symptoms; however, its poor sensitivity in detecting DST is a major drawback. Magnetic resonance (MR) imaging offers multiple advantages such as excellent contrast resolution and unenhanced venography possibilities, making it the mainstay in the non-invasive diagnosis of DST. However, physiological variations, evolution of thrombi, and incorrect selection/application of MR techniques can lead to false positive and false negative interpretations impacting patient management and outcome. This article discusses the MR techniques useful to diagnose DST and describes pitfalls, with troubleshooting methods, to ensure an accurate diagnosis. We have used multiple diagrammatic illustrations and MR images to highlight pertinent take-home points and to serve as an easy guide for day-to-day clinical practice.

Acute subdural haemorrhage complicating cerebral venous thrombosis in a patient with protein C deficiency.

Cerebral venous thrombosis (CVT) directly causing subdural haemorrhage (SDH) is a rare entity. We present a case of an 18-year-old female patient who presented with severe occipital headache. Neuroimaging showed acute SDH and CVT. She was eventually discovered to have underlying protein C deficiency. She was treated with anticoagulation and made an uneventful recovery. We aim to highlight the epidemiology, risk factors and aetiopathogenesis of CVT. We have included a literature review of previously described 13 case studies/reports describing SDH associated with CVT and a brief discussion of the dilemmas associated with management.

Adult-onset diffuse leukoencephalopathy with axonal spheroids and pigmented glia presenting with acute stroke-like symptoms: A rare clinical scenario.

Adult-onset diffuse leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a rare progressive degenerative white matter disease caused by mutations in the colony-stimulating factor-1 receptor gene. Patients commonly present in the 4th or 5th decade with variable clinical presentations including behavioral changes, dementia, parkinsonism, and motor dysfunctions, eventually leading to death within a few years. Although the disease is typically hereditary, sporadic cases are known to occur. The classic MRI features of ALSP include T2 hyperintensities in the frontal and parietal white matter, scattered foci of restricted diffusion in the white matter, age-advanced cerebral involutional changes, thinning and signal changes in the corpus callosum, absence of infratentorial involvement and lack of enhancement. CT commonly shows tiny calcifications in the corpus callosum and deep white matter. We report a unique case of sporadic ALSP that initially presented as young stroke with acute onset of left-sided hemiparesis and no preceding history of cognitive decline. However, subsequent cognitive and behavioral changes lead to the consideration of an alternative diagnosis. Stroke-like symptoms is a very rare primary presentation of this disease entity. We have highlighted the classic MRI and CT features that helped to guide its diagnosis in our patient and prompted early corroborative genetic testing.

Enterovirus-related rhombencephalitis and myelitis in the third trimester of pregnancy: A case report highlighting clinico-radiological findings at diagnosis and follow-up.

Rhombencephalitis (RE) refers to inflammatory diseases involving the brainstem and cerebellum. Although RE is a rare entity, it is associated with high morbidity and mortality. The management of such patients is often challenging in terms of identifying the etiology and defining prognosis. Infections, autoimmune and paraneoplastic conditions are commonly implicated. Patients with RE often present with a biphasic illness with an initial flu-like syndrome followed by brainstem dysfunction. CSF pleocytosis, abnormal brain MRI findings, isolation of organism or molecular (PCR/antigen) detection in CSF/blood cultures/stool samples and nasal/rectal swabs help in arriving at a definitive or probable diagnosis. Prompt aggressive treatment with antibacterial and antiviral drugs and/or immunoglobulins along with supportive therapy is crucial for avoiding a poor outcome. We present a case report of a 28-year old female patient who developed RE and myelitis in the third trimester of pregnancy. We aim to highlight the highly suggestive radiological findings which corroborated with the clinical diagnosis of enterovirus infection. The patient's radiological follow-up and neurological sequalae are also described. To the best of our knowledge, ours is the first report which describes the MRI features of this clinical scenario in the third trimester of pregnancy, and also the subsequent clinico-radiological follow up.

Role of MRI as first-line modality in the detection of previously undiagnosed otosclerosis: a single tertiary institute experience.

BACKGROUND: Otosclerosis causes conductive, sensorineural and mixed hearing loss (CHL, SNHL, MHL) and tinnitus in young adults. It is best diagnosed on high-resolution CT (HRCT). Occasionally, patients presenting with SNHL and/or tinnitus may undergo temporal bone MRI as the first investigation. In this study, we have described the role of MRI as the first-line modality in the detection of previously undiagnosed otosclerosis. Using search words 'MRI otosclerosis' we found 15 cases in the PACS of our institute, (University Hospitals, KU Leuven, Belgium) from 2003 to 2018. Of these, 2 were known cases of otosclerosis, hence excluded from the study. The remaining 13 patients underwent MRI as first-line investigation for unilateral SNHL (8/13), bilateral SNHL (3/13), unilateral MHL (1/13) and bilateral pulsatile tinnitus (1/13). All MRI studies were reported by the same senior radiologist. RESULTS: Of these 13 cases, 12 were reported as showing MRI features suspicious for otosclerosis. The typical positive findings in these cases were intermediate T1 signal and post-contrast enhancement in the perilabyrinthine/pericochlear regions. Out of 13 patients, 9 underwent subsequent HRCT, confirming otosclerosis in all. The single MRI which was reported as normal initially showed otosclerosis on HRCT. Retrospective evaluation of this MRI study showed subtle positive findings of otosclerosis. CONCLUSION: The end point of this study was to validate the subtle findings of otosclerosis on MRI, by comparison to the gold-standard modality HRCT. Our hypothesis is that in the appropriate clinical setting, familiarity with MRI features of otosclerosis would increase the diagnostic 'catch' in the first 'net' itself i.e. first-line MRI.

Gyriform restricted diffusion in adults: looking beyond thrombo-occlusions.

Gyriform restricted diffusion (GRD) refers to hyperintense signal involving the cerebral cortex on diffusion-weighted images (DWI) with corresponding hypointensity on apparent diffusion coefficient (ADC) images. These changes are commonly seen following a vascular occlusion, reflecting the limitation of water molecule movement across cell membranes (restricted diffusion) due to the failure of Na+/K+-ATPase pumps (cytotoxic oedema). However, GRD can occur in several other neurological conditions as well. A thorough understanding of these conditions and their anatomic predilection plays a critical role in identifying and differentiating them from vascular thrombo-occlusion, with impact towards appropriate clinical management. This review highlights the less commonly encountered, non-stroke causes of GRD in adults with case-based examples. A tabulated chart of the patterns of cortical and subcortical involvement associated with these aetiologies is provided for a quick, pattern-based reference for daily radiological reporting.

Natalizumab-Related Progressive Multifocal Leukoencephalopathy-Immune Reconstitution Inflammatory Syndrome: A Case Report Highlighting Clinical and MRI Features.

Multiple sclerosis (MS) patients treated with natalizumab often face the uncommon but severe complication of developing progressive multifocal leukoencephalopathy (PML). PML may be further complicated by immune reconstitution inflammatory syndrome (IRIS) after the removal of the drug. Since both PML and IRIS are associated with high morbidity and mortality rates, early clinical and radiological diagnosis of these complications is of paramount importance. Here, we report a case of an adult male patient who was diagnosed with PML after receiving natalizumab therapy for 6 years for the treatment of MS. Upon cessation of natalizumab, he presented with a paradoxical worsening of clinical and radiological findings consistent with an inflammatory brain injury due to IRIS. He was treated with high dose corticosteroid therapy followed by a gradual improvement in clinical and imaging findings. This article illustrates the magnetic resonance imaging (MRI) features of natalizumab-associated PML-IRIS, along with a brief overview of its clinical features, complications and management strategies.

The pterygopalatine fossa: imaging anatomy, communications, and pathology revisited.

UNLABELLED: The pterygopalatine fossa (PPF) is a small, clinically inaccessible, fat-filled space located in the deep face that serves as a major neurovascular crossroad between the oral cavity, nasal cavity, nasopharynx, orbit, masticator space, and the middle cranial fossa. Due to its inherent complex location and connections, it can potentially act as a natural conduit for the spread of inflammatory and neoplastic diseases across the various deep spaces in the head and neck. This review aims to acquaint the reader with the imaging anatomy of the PPF, its important communications, and to identify some major pathological conditions that can involve the PPF, especially in conditions where its involvement can have serious diagnostic and therapeutic implications, such as in perineural tumour spread. TEACHING POINTS: • The PPF is a small neurovascular junction in the deep face with important to-and-fro connections. • Awareness of anatomy of the PPF and its communications helps to simplify imaging of its pathology. • Perineural tumour spread is clinically the most important pathology in this region.

Imaging of facial nerve schwannomas: diagnostic pearls and potential pitfalls.

Schwannomas are uncommon in the facial nerve and account for less than 1% of tumors of temporal bone. They can involve one or more than one segment of the facial nerve. The clinical presentations and the imaging appearances of facial nerve schwannomas are influenced by the topographical anatomy of the facial nerve and vary according to the segment(s) they involve. This pictorial essay illustrates the imaging features of facial nerve schwannomas according to their various anatomical locations and also reviews the pertinent differential diagnoses and potential diagnostic pitfalls.

Orbital tumours and tumour-like lesions: exploring the armamentarium of multiparametric imaging.

Although the orbit is a small anatomical space, the wide range of structures present within it are often the site of origin of various tumours and tumour-like conditions, both in adults and children. Cross-sectional imaging is mandatory for the detection, characterization, and mapping of these lesions. This review focuses on multiparametric imaging of orbital tumours. Each tumour is reviewed in relation to its clinical presentation, compartmental location, imaging characteristics, and its histological features. We herein describe orbital tumours as lesions of the globe (retinoblastoma, uveal melanoma), optic nerve sheath complex (meningioma, optic nerve glioma), conal-intraconal compartment (hemangioma), extraconal compartment (dermoid/epidermoid, lacrimal gland tumours, lymphoma, rhabdomysarcoma), and bone and sinus compartment (fibrous dysplasia). Lesions without any typical compartmental localization and those with multi-compartment involvement (veno-lymphatic malformation, plexiform neurofibroma, idiopathic orbital pseudotumour, IgG4 related disease, metastases) are also reviewed. We discuss the role of advanced imaging techniques, such as MR diffusion-weighted imaging (DWI), diffusion tensor imaging, fluoro-2-deoxy-D-glucose positron emission tomography CT (FDG-PET CT), and positron emission tomography MRI (MRI PET) as problem-solving tools in the evaluation of those orbital masses that present with non-specific morphologic imaging findings. Main messages/Teaching points • A compartment-based approach is essential for the diagnosis of orbital tumours. • CT and MRI play a key role in the work-up of orbital tumours. • DWI, PET CT, and MRI PET are complementary tools to solve diagnostic dilemmas. • Awareness of salient imaging pearls and diagnostic pitfalls avoids interpretation errors.

A case report on 1-year follow-up of bilateral thalamic glioma.

Bilateral thalamic glioma is one of the rarest tumor occurrences, representing a small fraction of thalamic gliomas, which only accounts for 1-1.5% of all brain tumors. It is usually a diffuse, low-grade astrocytoma (WHO grade II), seen mainly in adults, with approximately 25% of them involving children under the age of 15. Radiotherapy is the main mode of treatment since surgical intervention is limited to a role of biopsy and management of secondary effects, due to the deep brain location of the lesion and the complexity of the involved structures. We report a 1-year follow-up of a 55-year-old female patient with bilateral WHO grade II thalamic astrocytoma. Following histological and neuroradiological consensus regarding the diagnosis, the patient was referred for radiotherapy. The effectiveness of available therapy and long-term neuroradiological follow-up is not reliably established due to rapid fatal evolution following diagnosis. Contrary to the norm, our patient showed stable disease with radiotherapy for a 1-year period.

Balo's Concentric Sclerosis with Acute Presentation and Co-Existing Multiple Sclerosis-Typical Lesions on MRI.

Balo's disease also known as Balo's concentric sclerosis (BCS) is a rare demyelinating disorder which is characterized pathologically and radiologically by concentric rings of demyelinated and relatively myelin-preserved white matter. We describe the case of a 25-year-old female presenting with stroke-like symptoms who was diagnosed with BCS on MRI. At clinical onset, she also showed co-existing multiple sclerosis (MS)-typical lesions in the brain. This report extends the recent concept that BCS may share similar pathogenesis and radiological progression as MS lesions, that they may occur simultaneously in the same patient and that they may represent different manifestations of the same disease process. Also, BCS needs not be a fulminant disease and may often show a benign self-limiting course as in our case.

Imaging of adult brainstem gliomas.

Brainstem gliomas (BSGs) are uncommon in adults accounting for about 2% of all intracranial neoplasms. They are often phenotypically low-grade as compared to their more common paediatric counterparts. Since brainstem biopsies are rarely performed, these tumours are commonly classified according to their MR imaging characteristics into 4 subgroups: (a) diffuse intrinsic low-grade gliomas, (b) enhancing malignant gliomas, (c) focal tectal gliomas and (d) exophytic gliomas/other subtypes. The prognosis and treatment is variable for the different types and is almost similar to adult supratentorial gliomas. Radiotherapy (RT) with adjuvant chemotherapy is the standard treatment of diffuse low-grade and malignant BSGs, whereas, surgical resection is limited to the exophytic subtypes. Review of previous literature shows that the detailed imaging of adult BSGs has not received significant attention. This review illustrates in detail the imaging features of adult BSGs using conventional and advanced MR techniques like diffusion weighted imaging (DWI), diffusion tensor imaging (DTI), MR perfusion weighted imaging (PWI), MR spectroscopy (MRS), as well as 18F-fluoro-ethyl-tyrosine positron emission tomography (18F-FET/PET). We have discussed the pertinent differences between childhood and adult BSGs, imaging mimics, prognostic factors and briefly reviewed the treatment options of these tumours.

Aggressive primary olfactory neuroblastoma of the sphenoclival region: a case report and literature review.

Olfactory neuroblastoma (ONB) is an uncommon malignant tumor of neural crest origin, which commonly arises in the superior nasal cavity. Ectopic origin of an ONB is exceedingly rare. We describe a rare case of an ectopic sphenoclival ONB with extensive involvement of the central skull base and with development of systemic metastases. To our knowledge, ours is the first case that describes the imaging features of this rare entity on computed tomography (CT), magnetic resonance imaging, 18 F-fluorodeoxyglucose-positron-emission tomography/CT, and digital subtraction angiography. We also describe the histological features, imaging differentials, and treatment options for this tumor along with a brief literature review.

FDG-PET/CT pitfalls in oncological head and neck imaging.

OBJECTIVES: Positron emission tomography-computed tomography (PET/CT) with fluorine-18-fluorodeoxy-D-glucose (FDG) has evolved from a research modality to an invaluable tool in head and neck cancer imaging. However, interpretation of FDG PET/CT studies may be difficult due to the inherently complex anatomical landmarks, certain physiological variants and unusual patterns of high FDG uptake in the head and neck. The purpose of this article is to provide a comprehensive approach to key imaging features and interpretation pitfalls of FDG-PET/CT of the head and neck and how to avoid them. METHODS: We review the pathophysiological mechanisms leading to potentially false-positive and false-negative assessments, and we discuss the complementary use of high-resolution contrast-enhanced head and neck PET/CT (HR HN PET/CT) and additional cross-sectional imaging techniques, including ultrasound (US) and magnetic resonance imaging (MRI). RESULTS: The commonly encountered false-positive PET/CT interpretation pitfalls are due to high FDG uptake by physiological causes, benign thyroid nodules, unilateral cranial nerve palsy and increased FDG uptake due to inflammation, recent chemoradiotherapy and surgery. False-negative findings are caused by lesion vicinity to structures with high glucose metabolism, obscuration of FDG uptake by dental hardware, inadequate PET scanner resolution and inherent low FDG-avidity of some tumours. CONCLUSIONS: The interpreting physician must be aware of these unusual patterns of FDG uptake, as well as limitations of PET/CT as a modality, in order to avoid overdiagnosis of benign conditions as malignancy, as well as missing out on actual pathology. TEACHING POINTS: • Knowledge of key imaging features of physiological and non-physiological FDG uptake is essential for the interpretation of head and neck PET/CT studies. • Precise anatomical evaluation and correlation with contrast-enhanced CT, US or MRI avoid PET/CT misinterpretation. • Awareness of unusual FDG uptake patterns avoids overdiagnosis of benign conditions as malignancy.

Imaging in otosclerosis: A pictorial review.

Otosclerosis is an otodystrophy of the otic capsule and is a cause of conductive, mixed or sensorineural hearing loss in the 2nd to 4th decades of life. Otosclerosis is categorised into two types, fenestral and retrofenestral. Imaging plays an important role in the diagnosis and management of otosclerosis. High-resolution CT (HRCT) of the temporal bone using 1-mm (or less) thick sections is the modality of choice for assessment of the labyrinthine windows and cochlear capsules. MRI has limited application in the evaluation of the labyrinthine capsules but is useful for assessment of the cochlear lumen prior to cochlear implantation in patients with profound hearing loss. The treatment of fenestral otosclerosis is primarily surgical with stapedectomy and prosthesis insertion. Patients with retrofenestral otosclerosis and profound hearing loss are treated medically using fluorides, but may derive significant benefit from cochlear implantation. This pictorial review aims to acquaint the reader with the pathology and clinical features of otosclerosis, the classical imaging appearances on CT and MRI, a radiological checklist for preoperative CT evaluation of otosclerosis, imaging mimics and a few examples of post-stapedectomy imaging and complications. Teaching points • Otosclerosis causes conductive, sensorineural and mixed hearing loss in adults.• HRCT of the temporal bone is the diagnostic imaging modality of choice.• Stapedectomy is used to treat fenestral otosclerosis.• Fluorides and cochlear implantation are used to treat retrofenestral otosclerosis.

Dedifferentiated laryngeal chondrosarcoma: combined morphologic and functional imaging with positron-emission tomography/magnetic resonance imaging.

Chondrosarcoma of the larynx is a rare, low-grade malignancy in terms of histology and clinical behavior. We present an unusual case of laryngeal chondrosarcoma, which developed a large dedifferentiated component on recurrence after primary surgery. The diagnosis of dedifferentiation was suggested in view of the morphological and metabolic findings on hybrid positron-emission tomography/magnetic resonance imaging (PET/MRI) and was subsequently confirmed surgically. Whole-organ, slice-by-slice radiologic-histologic correlation revealed excellent delineation of the well-differentiated and dedifferentiated tumor components with PET/MRI. PET/MRI can provide additional functional information to supplement the morphological mapping and histopathology of these tumors.