Kelly K. Koeller

Lacrimal gland tumors and simulating lesions. Clinicopathologic and MR imaging features.

The lacrimal gland region can be involved in a wide spectrum of orbital pathology, including inflammatory, lymphoproliferative, and epithelial tumors. This article focuses on benign and malignant epithelial tumors of lacrimal gland and simulating lesions. The clinical presentations, MR imaging, and pathologic findings of lacrimal gland tumors are reviewed.

Bacterial, Fungal, and Parasitic Infections of the Central Nervous System: Radiologic-Pathologic Correlation and Historical Perspectives: From the Radiologic Pathology Archives

Despite remarkable progress in prevention and treatment, infectious diseases affecting the central nervous system remain an important source of morbidity and mortality, particularly in less-developed countries and in immunocompromised persons. Bacterial, fungal, and parasitic pathogens are derived from living organisms and affect the brain, spinal cord, or meninges. Infections due to these pathogens are associated with a variety of neuroimaging patterns that can be appreciated at magnetic resonance imaging in most cases. Bacterial infections, most often due to Streptococcus, Haemophilus, and Neisseria species, cause significant meningitis, whereas the less common cerebritis and subsequent abscess formation have well-documented progression, with increasingly prominent altered signal intensity and corresponding contrast enhancement. Atypical bacterial infections are characterized by the development of a granulomatous response, classically seen in tuberculosis, in which the tuberculoma is the most common parenchymal form of the disease; spirochetal and rickettsial diseases are less common. Fungal infections predominate in immunocompromised hosts and are caused by yeasts, molds, and dimorphic fungi. Cryptococcal meningitis is the most common fungal infection, whereas candidiasis is the most common nosocomial infection. Mucormycosis and aspergillosis are characterized by angioinvasiveness and are associated with high morbidity and mortality among immunocompromised patients. In terms of potential exposure in the worldwide population, parasitic infections, including neurocysticercosis, toxoplasmosis, echinococcosis, malaria, and schistosomiasis, are the greatest threat. Rare amebic infections are noteworthy for their extreme virulence and high mortality. The objective of this article is to highlight the characteristic neuroimaging manifestations of bacterial, fungal, and parasitic diseases, with emphasis on radiologic-pathologic correlation and historical perspectives.

MESENCHYMAL CHONDROSARCOMA AND SIMULATING LESIONS OF THE ORBIT

Although an extremely rare neoplasm, orbital mesenchymal chondrosarcoma has a characteristic radiologic appearance. Suspicion of this lesion preoperatively can be of great value to the ophthalmologist because it tends to produce profuse bleeding at biopsy. This article reviews the clinical presentation, pathologic features, and radiologic findings of patients with orbital mesenchymal chondrosarcoma.

Viral and Prion Infections of the Central Nervous System: Radiologic-Pathologic Correlation: From the Radiologic Pathology Archives

Viral infections of the central nervous system (CNS) range in clinical severity, with the most severe proving fatal within a matter of days. Some of the more than 100 different viruses known to affect the brain and spinal cord are neurotropic with a predilection for producing CNS infection. The host response to viral infection of the CNS is responsible for the pathophysiology and imaging findings seen in affected patients. Viral CNS infections can take the form of meningitis, encephalitis, encephalomyelitis, or, when involving the spinal cord and nerve roots, encephalomyeloradiculitis. In 1982, an infectious particle termed a prion that lacked nucleic acid and therefore was not a virus was reported to produce the fatal neurodegenerative disease Creutzfeldt-Jakob disease and related disorders. These prion diseases produce characteristic neuroimaging findings that are distinct from those seen in most viral infections. The clinical and imaging findings associated with viral CNS infection are often nonspecific, with microbiologic analysis of cerebrospinal fluid the most useful single test allowing for diagnosis of a specific viral infection. This review details the spectrum of viral CNS infections and uses case material from the archives of the American Institute for Radiologic Pathology, with a focus on the specific clinical characteristics and magnetic resonance imaging features seen in these infections. Where possible, the imaging features that allow distinction of these infections from other CNS inflammatory conditions are highlighted.

Infektionen des zentralen Nervensystems durch Bakterien, Pilze und Parasiten: radiologisch-pathologische Korrelation und historischer Rückblick

Trotz beachtlicher Fortschritte in Pravention und Behandlung bleiben Infektionskrankheiten mit Beteiligung des zentralen Nervensystems eine wichtige Morbiditats- und Mortalitatsursache, insbesondere in weniger entwickelten Landern und bei immunkompromittierten Personen. Bakterielle, Pilz- und parasitare Pathogene sind lebende Organismen und greifen Gehirn, Ruckenmark oder Hirnhaute an. Infektionen durch diese Pathogene sind mit vielfaltigen Mustern in der Neurobildgebung assoziiert, die sich in den meisten Fallen am besten in der Magnetresonanztomografie darstellen lassen. Bakterielle Infektionen – am haufigsten auf Streptokokken-, Haemophilus- und Neisseria-Spezies zuruckzufuhren – verursachen eine signifikante Meningitis, wahrend die weniger haufige Zerebritis und die anschliesende Abszessbildung eine gut dokumentierte Progression aufweisen, mit zunehmend hervortretender Veranderung der Signalintensitat und entsprechender Kontrastmittelanreicherung. Atypische bakterielle Infektionen sind durch die Entwicklung einer granulomatosen Reaktion charakterisiert, die klassischerweise bei der Tuberkulose beobachtet wird; dabei ist das Tuberkulom die haufigste parenchymale Form der Erkrankung. Durch Spirochaten und Rickettsien verursachte Erkrankungen sind weniger haufig. Pilzinfektionen herrschen bei immunkompromittierten Wirten vor und werden durch Hefepilze, Schimmelpilze und dimorphe Pilze verursacht. Die Kryptokokkenmeningitis ist die haufigste Pilzinfektion, wahrend die Candidiasis die haufigste nosokomiale Infektion ist. Mukormykose und Aspergillose sind angioinvasiv und gehen mit einer hohen Morbiditat und Mortalitat bei immunkompromittierten Patienten einher. Hinsichtlich einer potenziellen weltweiten Exposition sind parasitare Infektionen, darunter Neurozystizerkose, Toxoplasmose, Echinokokkose, Malaria und Schistosomiasis, die groste Bedrohung. Seltene Amobeninfektionen sind wegen ihrer extremen Virulenz und hohen Mortalitat erwahnenswert. Das Ziel dieses Artikels ist es, die in der Neurobildgebung charakteristischen Manifestationen von Infektionen durch Bakterien, Pilze und Parasiten hervorzuheben; dabei liegt der Schwerpunkt auf der radiologisch-pathologischen Korrelation und dem historischen Ruckblick.