James G. Smirniotopoulos

From the Archives of the AFIP : Central Nervous System Infections Associated with Human Immunodeficiency Virus Infection: Radiologic-Pathologic Correlation

Diseases of the central nervous system (CNS) in patients infected with the human immunodeficiency virus (HIV) result directly from HIV itself or from a variety of opportunistic agents. These infections include progressive multifocal leukoencephalopathy, toxoplasmosis, and cryptococcosis. A resurgence of tuberculosis and neurosyphilis has also been documented. Mass lesions, meningoencephalitis, demyelination, atrophy, and vascular lesions are the commonly encountered imaging findings. The introduction of highly active antiretroviral therapy (HAART) has improved both the clinical and radiologic findings in HIV-infected patients and reduced the number of opportunistic infections. In countries that use HAART, AIDS (acquired immunodeficiency syndrome) dementia complex is becoming the most common neurologic complication of HIV infection, whereas opportunistic infections are still the major cause of neurologic complications in patients from countries that do not commonly use HAART. Immune reconstitution inflammatory syndrome, which occurs in some patients in the weeks to months after the institution of HAART, may alter the typical imaging appearance of infectious diseases involving the CNS. Knowledge of the spectrum of imaging findings of these infectious diseases, as well as the effect that treatment has on imaging appearances, is important in the evaluation of HIV-infected patients.

Pigmented Lesions of the Central Nervous System: Radiologic-Pathologic Correlation

Pigmented lesions of the central nervous system (CNS) are a diverse group of entities that run the gamut from benign to malignant. These lesions may be well circumscribed or diffuse, and their imaging appearances are influenced by the degree of melanin content as well as the presence or absence of hemorrhage. Pigmented lesions include primary melanocytic lesions of the CNS and metastatic melanoma, as well as other CNS neoplasms that may undergo melanization, including schwannoma, medulloblastoma, and some gliomas. Primary melanocytic lesions of the CNS arise from melanocytes located within the leptomeninges, and this group includes diffuse melanocytosis and meningeal melanomatosis (seen in neurocutaneous melanosis), melanocytoma, and malignant melanoma. Primary melanin-containing lesions of the CNS must be differentiated from metastatic melanoma because these lesions require different patient workup and therapy. Absence of a known primary malignant melanoma helps in the differential diagnosis, but an occult primary lesion outside the CNS must be sought and excluded. Pigmented lesions of the CNS are uncommon, and knowledge of their imaging characteristics and pathologic features is essential for their identification.

Common data elements in radiologic imaging of traumatic brain injury.

Traumatic brain injury (TBI) has a poorly understood pathology. Patients suffer from a variety of physical and cognitive effects that worsen as the type of trauma worsens. Some noninvasive insights into the pathophysiology of TBI are possible using magnetic resonance imaging (MRI), computed tomography (CT), and many other forms of imaging as well. A recent workshop was convened to evaluate the common data elements (CDEs) that cut across the imaging field and given the charge to review the contributions of the various imaging modalities to TBI and to prepare an overview of the various clinical manifestations of TBI and their interpretation. Technical details regarding state‐of‐the‐art protocols for both MRI and CT are also presented with the hope of guiding current and future research efforts as to what is possible in the field. Stress was also placed on the potential to create a database of CDEs as a means to best record information from a given patient from the reading of the images. J. Magn. Reson. Imaging 2010;32:516–543.

From the Archives of the AFIP: Lesions of the Pineal Region: Radiologic-Pathologic Correlation

Lesions of the pineal region include a diverse group of entities. The most common neoplastic lesions are the germ cell tumors. Germ cell tumors may be hormonally active, and evaluation of serum or cerebrospinal fluid levels of oncoproteins assists in making the diagnosis. Neoplasms arising from the pineal parenchyma include the low-grade pineocytoma, pineal parenchymal tumor of intermediate differentiation, and the highly malignant pineoblastoma. Germ cell tumors and pineal parenchymal neoplasms do not have pathognomonic imaging findings, but imaging in combination with laboratory evaluation helps narrow the differential diagnosis. Neoplasms may also arise from the variety of cell types residing in the proximity of the pineal gland. These include lipomas, meningiomas, and astrocytomas. Congenital lesions such as epidermoid and dermoid cysts and lipomas can also occur. Knowledge of the variety of lesions that occur in the pineal region, their imaging appearances, and their clinical features assists in narrowing the radiologic differential diagnosis and optimizing patient treatment.

From the Archives of the AFIP Pediatric Orbit Tumors and Tumorlike Lesions: Osseous Lesions of the Orbit

Many extraocular masses involving the pediatric orbit have an osseous origin. The most common is the dermoid inclusion cyst; these cystic lesions may contain lipid and are most often found near the zygomaticofrontal suture, adjacent to an indolent-appearing erosion of bone. Some primary bone lesions may involve the orbit, producing a lytic or dense lesion with enlargement of the bone; these lesions include fibrous dysplasia, juvenile ossifying fibroma, and osteosarcoma. Fibrous dysplasia tends to produce a mass of ground-glass appearance with longitudinal osseous expansion, whereas juvenile ossifying fibroma is likely to produce a mixed lytic and sclerotic lesion and focal osseous enlargement. Osteosarcoma causes marked bone destruction and variable osteoid production. Langerhans cell histiocytosis, an idiopathic reticuloendothelial proliferative disorder, tends to involve the bones of the skull, especially the lateral orbital roof; it produces lytic destruction of bone with a sclerotic rim and a large intraorbital soft-tissue mass. Granulocytic sarcoma is a solid tumor that may occur in children with myelogenous leukemia. These tumors tend to arise in the subperiosteum of the lateral orbital wall, although they usually do not disrupt the bone. Finally, the orbit is a common site for bone metastases from neuroblastoma, which cause aggressive periosteal reaction in the orbital roof or lateral wall. The last three conditions are often bilateral. At imaging evaluation, osseous lesions may appear similar to each other and to nonosseous masses of the orbit. Knowledge of the pathologic features of these tumors and how these features are reflected in their imaging appearances may help radiologists differentiate them.

From the Radiologic Pathology Archives: Intraventricular Neoplasms: Radiologic-Pathologic Correlation

A variety of neoplasms may arise in the ventricular system. Intraventricular neoplasms may be discovered as an incidental finding at cross-sectional imaging or may manifest with varied symptoms depending on their location, including symptoms of increased intracranial pressure. These lesions may arise from various ventricular structures, including the ependymal lining (eg, ependymoma), subependymal layer (eg, subependymoma), or choroid plexus (eg, choroid plexus neoplasms), or they may have a cell of origin that has yet to be determined (eg, chordoid glioma). Other neoplasms involving the ventricular system include central neurocytoma, subependymal giant cell tumor, meningioma, rosette-forming glioneuronal tumor, and metastases. The differential diagnosis for intraventricular neoplasms can be broad, and many of them have similar patterns of signal intensity and contrast enhancement at imaging. However, the location of the lesion in the ventricular system-along with knowledge of the patients age, gender, and underlying conditions-will help narrow the differential diagnosis.

Bilateral Thalamic Lesions

OBJECTIVE The purpose of this study was to present the neuroimaging findings and differential diagnosis of bilateral thalamic lesions. CONCLUSION The limited differential diagnosis of bilateral thalamic lesions can be further narrowed with knowledge of the specific imaging characteristics of the lesions in combination with the patient history.

Lesions of the cauda equina: a clinical and pathology review from the Armed Forces Institute of Pathology

We reviewed the clinical records of 149 patients with pathologically proved cauda equina lesions in order to define the relative frequency and clinical presentations of the various diagnoses. The most common pathology was ependymomas (47 patients) followed in frequency by nerve sheath tumors (35 patients), metastases (27 patients), nonependymal glial neoplasms (six patients), meningiomas (six patients), lipomas (five patients), paragangliomas (five patients) and various other diagnoses (19 patients). Mean patient age at presentation for the various lesions included: metastases (51.5 years), nerve sheath tumors (49.7 years), nonependymal glial tumors (46.5 years), paragangliomas (41.2 years), ependymomas (38.3 years), meningiomas (34.7 years), and lipomas (18.4 years). ANOVA showed that the relationship between age and diagnosis for these groups to be statistically significant at a high level (P = 0.002). Low back pain was the most common symptom and occurred in 44 patients. Other symptoms included unilateral lower extremity pain or tenderness (24 patients), bilateral lower extremity pain or tenderness (16 patients), and bilateral lower extremity weakness (16 patients). No relationship between pathologic diagnosis and specific symptoms was found.

Retention of Radiographic Anatomy of the Chest by 4th-Year Medical Students

RATIONALE AND OBJECTIVES The authors performed this study to assess the ability of medical students to retain their knowledge of radiographic anatomy into the 4th year. MATERIALS AND METHODS One hundred ninety-four 4th-year medical students were quizzed on their ability to (a) identify 10 anatomic structures on chest radiographs and (b) search an abnormal radiograph to identify two important findings. Frontal and lateral views were used. The students had learned about radiographic anatomy of the chest and plain radiography search techniques in 1st- and 2nd-year courses and had proved their ability to perform these tasks, during their 2nd year of medical school, by achieving grades of 84% or more (average grade, 90%) on individual oral examinations administered by radiologists. RESULTS The mean test score was 4.47 out of 12. Only 10 students (5%) were able to identify the main pulmonary artery on the frontal view, and only nine (4%) identified the main bronchi on the lateral view. Of the 194 students, 192 failed to detect a collapsed vertebral body on the lateral view of a patient who had previously undergone a mastectomy. CONCLUSION Specific radiologic anatomy facts and search techniques are poorly retained by 4th-year medical students. Preclinical teaching of imaging probably should stress principles rather than specific details.

Intussuscepted meckel diverticulum: Radiologic-pathologic correlation

Nine cases of Meckel diverticulum presenting with intussusception were reviewed and correlated clinically, radiologically and pathologically. The appearance of intussuscepted Meckel diverticulum by small bowel series is not specific. However, by CT, a central fat density surrounded by a thick collar of soft tissue was noted in one case correlating well with the gross pathologic appearance. The pathologic material in all our cases suggests that this CT appearance is characteristic of an inverted Meckel diverticulum.