Imaging of spinal chordoma and benign notochordal cell tumor (BNCT) with radiologic pathologic correlation.

Benign notochordal cell tumor (BNCT) and chordoma are neoplasms of notochordal differentiation. BNCT represents notochordal rests, commonly an incidental lesion present in the spine in 19% of cadaveric specimens. BNCTs are often radiographically occult. CT of BNCT frequently reveals patchy sclerosis between areas of maintained underlying trabeculae. BNCT demonstrates marrow replacement on T1-weighted MR images with high signal intensity on T2-weighting. BNCTs are frequently smaller than 35 mm and lack significant enhancement, bone destruction, cortical permeation, or soft tissue components. Biopsy or surgical resection of BNCT is usually not warranted, although imaging surveillance may be indicated. Chordoma is a rare low-grade locally aggressive malignancy representing 1-4% of primary malignant bone tumors. Chordoma is most frequent between the ages of 50-60 years with a male predilection. Clinical symptoms, while nonspecific and location dependent, include back pain, numbness, myelopathy, and bowel/bladder incontinence. Unfortunately, lesions are often large at presentation owing to diagnosis delay. Imaging of chordoma shows variable mixtures of bone destruction and sclerosis, calcification (50-70% at CT) and large soft tissue components. MR imaging of chordoma reveals multilobulated areas of marrow replacement on T1-weighting and high signal intensity on T2-weighting reflecting the myxoid component within the lesion and areas of hemorrhage seen histologically. Treatment of chordoma is primarily surgical with prognosis related to resection extent. Unfortunately, complete resection is often not possible (21-75%) resulting in high local recurrence incidence (19-75%) and a 5-year survival rate of 45-86%. This article reviews and illustrates the clinical characteristics, pathologic features, imaging appearance spectrum, treatment, and prognosis of BNCT and spinal chordoma.

Primary Tumors of the Pituitary Gland: Radiologic-Pathologic Correlation.

Primary tumors of the pituitary gland are the second most common histologic category of primary central nervous system tumors across all age groups and are the most common in adolescents to young adults, despite originating from a diminutive endocrine gland that is often described as "about the size of a pea." The vast majority of these represent primary tumors of the adenohypophysis, specifically pituitary adenomas, which can be either functional or silent with regard to hormone hypersecretion. According to the fourth edition of the World Health Organization classification of endocrine tumors, published in 2017, cellular lineage and immunohistochemical stains for pituitary hormones and/or transcription factors help with making the correct pathologic diagnosis. From a radiologic standpoint, microadenomas pose challenges for accurate detection and avoiding false-negative or false-positive results, while macroadenomas pose challenges from local mass effect on surrounding structures. Pituitary carcinoma and pituitary blastoma also arise from the adenohypophysis and are characterized by metastatic disease and infantile presentation, respectively. While primary tumors of the adenohypophysis are common, a second category comprising primary tumors of the Rathke pouch (ie, craniopharyngioma) are uncommon, and a third category comprising primary tumors of the neurohypophysis (eg, pituicytoma) are rare. The authors review all three categories of pituitary tumors, with emphasis on radiologic-pathologic correlation, including the typical neuroimaging, histologic, and molecular features that may point toward a specific diagnosis. Work of the U.S. Government published under an exclusive license with the RSNA.

Intramedullary Masses of the Spinal Cord: Radiologic-Pathologic Correlation.

Spinal cord tumors are a challenge for patients and neurosurgeons because of the high risk of neurologic deficits from the disease process and surgical interventions. Spinal cord tumors are uncommon, and approximately 2%-3% of primary intra-axial tumors of the central nervous system occur in the spinal cord. Primary intra-axial tumors are usually derived from neuroepithelial tissue, especially glial cells. This often leads to a classic intramedullary mass differential diagnosis of ependymoma or astrocytoma, which together constitute up to 70% of spinal cord tumors. For example, ependymomas occur predominantly in adults, and astrocytomas (specifically pilocytic astrocytomas) occur predominantly in children. While that is an excellent starting point, in order to refine the differential diagnosis, the authors review the radiologic-pathologic features of specific neoplastic categories and entities recognized by the World Health Organization (WHO) in the 2016 WHO Classification of Tumours of the Central Nervous System and a few additional congenital-developmental entities. Radiologists can add value by providing a reasonable preoperative differential diagnosis for the patient and neurosurgeon, in many cases by favoring the most common conditions, and in other cases by identifying radiologic features that may point toward a less common entity. Some of the less common entities include intramedullary myxopapillary ependymoma, spinal subependymoma, and spinal hemangioblastoma. Whenever possible, the characteristic imaging features and locations of these tumors are explained or traced back to the underlying cell of origin and findings seen at histopathologic examination.See discussion on this article by Buch.

Intradural Extramedullary Spinal Neoplasms: Radiologic-Pathologic Correlation.

While intradural extramedullary spinal disease varies widely, identification of tumors in this location and their radiologic manifestations greatly facilitates narrowing of the diagnostic considerations. Meningioma and schwannoma are the two most common intradural extramedullary tumors, and both are associated with neurofibromatosis. Meningiomas are most common in the thoracic spine and show a strong female predilection and a clinical manifestation related to compression of the spinal cord or nerve roots. Schwannomas typically are associated with radicular pain and other sensory symptoms. Melanotic schwannoma frequently shows T1 hyperintensity at MRI related to the presence of paramagnetic free radicals in melanin. Neurofibroma, known for its T2 hyperintensity, frequently involves the cervical spine, where it may make surgical resection challenging. Less commonly, malignant peripheral nerve sheath tumor commonly mimics the imaging appearance of a schwannoma but has decidedly more aggressive biologic behavior. In the cauda equina, myxopapillary ependymoma and paraganglioma are believed to arise from the filum terminale and have characteristic imaging manifestations based on their underlying pathologic features. Recent identification of a common genetic marker has led to reclassification of what had previously been regarded as separate tumors and are now known as solitary fibrous tumor/hemangiopericytoma. In the proper clinical setting, the presence of nodular intradural enhancement strongly suggests the presence of leptomeningeal metastatic disease, even when results of cerebrospinal fluid analysis are negative. This article highlights the characteristic neuroimaging manifestations of these neoplasms, with emphasis on radiologic-pathologic correlation. See Illumination by Frazier .

MANAGEMENT AND OUTCOMES OF GIANT PROLACTINOMA: A SERIES OF 71 PATIENTS.

Objective: To describe outcomes of patients with giant prolactinoma (≥4 cm) and identify predictors of therapeutic response. Methods: In this retrospective study, complete biochemical and structural response were defined as prolactin (PRL) ≤25 ng/mL and no visible tumor at follow-up, respectively. Results: Giant prolactinoma (median size, 4.8 cm [range, 4 to 9.8 cm]; median PRL, 5,927 ng/mL [range, 120 to 100,000 ng/mL]) was diagnosed in 71 patients. Treatments included: dopamine agonists (DAs) (n = 70, 99%), surgery (n = 30, 42%), radiation (n = 10, 14%), and somatostatin analogs (n = 2, 3%). Patients treated with DA monotherapy were older compared with those who received subsequent therapies (47 years vs. 28 years; P = .003) but had similar initial PRL and tumor size. Surgically managed patients were younger compared with the nonsurgical group (35 years vs. 46 years; P = .02) and had lower initial PRL (3,121 ng/mL vs. 6,920 ng/mL; P = .02), yet they had similar tumor response. Hypopituitarism was more common following surgery compared to medical management: adrenal insufficiency (69% vs. 27%; P<.001), hypothyroidism (67% vs. 38%; P = .02), growth hormone deficiency (24% vs. 6%; P = .04), and diabetes insipidus (17% vs. 3%; P = .04). Therapeutic response did not correlate with sex, age, initial PRL, tumor size, or first-line therapy mode. At median follow-up of 4.8 years, the median PRL was 18.3 ng/mL (range, 0.6 to 12,680 ng/mL), and final volume was 0.9 cm3 (range, 0 to 43.0 cm3). In those with available data, 36/65 (55%) patients achieved PRL normalization, and 16/61 (26%) had no visible tumor at follow-up. Conclusion: Most patients with giant prolactinoma have excellent response to DA. Sex, age, initial PRL, and tumor size do not predict therapeutic response. Abbreviations: BRC = bromocriptine; CAB = cabergoline; CSF = cerebrospinal fluid; DA = dopamine agonist; MRI = magnetic resonance imaging; PRL = prolactin.

Embryonal Tumors of the Central Nervous System: From the Radiologic Pathology Archives.

Embryonal tumors of the central nervous system (CNS) are highly malignant undifferentiated or poorly differentiated tumors of neuroepithelial origin and have been defined as a category in the World Health Organization (WHO) classification since the first edition of the "Blue Book" in 1979. This category has evolved over time to reflect our ever-improving understanding of tumor biology and behavior. With the most recent update in 2016, many previous histologic diagnoses incorporate molecular parameters for the first time (genetically defined entities). While medulloblastoma and atypical teratoid/rhabdoid tumor are familiar carryovers from the 2007 CNS WHO classification, there are major changes to the embryonal tumor category: for example, elimination of the term CNS primitive neuroectodermal tumor and addition of a new genetically defined entity, embryonal tumor with multilayered rosettes, C19MC-altered. The purpose of this article is to discuss both the radiologic-pathologic features of CNS embryonal tumors and the new molecularly defined types/subtypes that will become the standard classification/terminology for future diagnoses and tumor research.

MRI findings in glutamic acid decarboxylase associated autoimmune epilepsy.

PURPOSE: Glutamic acid decarboxylase (GAD65) has been implicated in a number of autoimmune-associated neurologic syndromes, including autoimmune epilepsy. This study categorizes the spectrum of MRI findings in patients with a clinical diagnosis of autoimmune epilepsy and elevated serum GAD65 autoantibodies. METHODS: An institutional database search identified patients with elevated serum GAD65 antibodies and a clinical diagnosis of autoimmune epilepsy who had undergone brain MRI. Imaging studies were reviewed by three board-certified neuroradiologists and one neuroradiology fellow. Studies were evaluated for cortical/subcortical and hippocampal signal abnormality, cerebellar and cerebral volume loss, mesial temporal sclerosis, and parenchymal/leptomeningeal enhancement. The electronic medical record was reviewed for relevant clinical information and laboratory markers. RESULTS: A study cohort of 19 patients was identified. The majority of patients were female (84%), with a mean age of onset of 27 years. Serum GAD65 titers ranged from 33 to 4415 nmol/L (normal < 0.02 nmol/L). The most common presentation was medically intractable, complex partial seizures with temporal lobe onset. Parenchymal atrophy was the most common imaging finding (47%), with a subset of patients demonstrating cortical/subcortical parenchymal T2 hyperintensity (37%) or abnormal hippocampal signal (26%). No patients demonstrated abnormal parenchymal/leptomeningeal enhancement. CONCLUSION: The most common MRI finding in GAD65-associated autoimmune epilepsy is disproportionate parenchymal atrophy for age, often associated with abnormal cortical/subcortical T2 hyperintensities. Hippocampal abnormalities are seen in a minority of patients. This constellation of findings in a patient with medically intractable epilepsy should raise the possibility of GAD65 autoimmunity.

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.

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

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.

Central Nervous System Lesions in Immunocompromised Patients.

Immunodeficiency can affect different components of the immune system and predispose to different types of opportunistic infections. For example, a defect in neutrophil or humoral immunity increases risk from disseminated infection by extracellular pathogens, whereas a defect in cytotoxic activity by natural killer cells or CD8+ T lymphocytes increases risk from intracellular pathogens. The latter also increases risk from malignancies, due to impairment of normal immunosurveillance against abnormal neoplastic cells. The purpose of this article is to discuss central nervous system lesions that may be seen in the immunocompromised patient, organized into 5 categories: bacterial, fungal, parasitic, viral, and neoplastic.

Reoperation for sella haematoma after pituitary surgery.

OBJECTIVE: Although occasionally discussed as a general complication in large pituitary series, the incidence of reoperation for postoperative sella haematoma is unclear. We retrospectively reviewed a large pituitary surgical series to determine the incidence and associated factors of this complication. DESIGN: We reviewed all pituitary surgery at Mayo Rochester from January 1987 until January 2007. There were 2312 transsphenoidal procedures during this period. PATIENTS: All patients had proven pituitary pathology by computed tomography (CT) or magnetic resonance imaging and pituitary function studies. MEASUREMENTS: Reoperation for sella haematoma and perioperative clinical correlations were the only measurement tools. It is indeterminate how many patients had postoperative sella haematoma without visual loss because routine postoperative CT scanning was not performed. RESULTS: Three patients underwent reoperation for postoperative haematoma in the sella by three different endocrine neurosurgeons, and all three patients had progressive postoperative visual loss. All initial operations were for large macroadenomas; two had early postoperative hypertension that may have been a contributor; and one had markedly thickened bone felt to be the source of bleeding and deterioration 24 h later. CONCLUSIONS: Reoperation for postoperative sellar haematoma is uncommon. However, postoperative progressive visual loss was clinically present in all three patients, and labile hypertension postoperatively may play a role.

Cochlear Implant Electrode Localization Using an Ultra-High Resolution Scan Mode on Conventional 64-Slice and New Generation 192-Slice Multi-Detector Computed Tomography.

HYPOTHESIS: A new generation 192-slice multi-detector computed tomography (MDCT) clinical scanner provides enhanced image quality and superior electrode localization over conventional MDCT. BACKGROUND: Currently, accurate and reliable cochlear implant electrode localization using conventional MDCT scanners remains elusive. METHODS: Eight fresh-frozen cadaveric temporal bones were implanted with full-length cochlear implant electrodes. Specimens were subsequently scanned with conventional 64-slice and new generation 192-slice MDCT scanners utilizing ultra-high resolution modes. Additionally, all specimens were scanned with micro-CT to provide a reference criterion for electrode position. Images were reconstructed according to routine temporal bone clinical protocols. Three neuroradiologists, blinded to scanner type, reviewed images independently to assess resolution of individual electrodes, scalar localization, and severity of image artifact. RESULTS: Serving as the reference standard, micro-CT identified scalar crossover in one specimen; imaging of all remaining cochleae demonstrated complete scala tympani insertions. The 192-slice MDCT scanner exhibited improved resolution of individual electrodes (p < 0.01), superior scalar localization (p < 0.01), and reduced blooming artifact (p < 0.05), compared with conventional 64-slice MDCT. There was no significant difference between platforms when comparing streak or ring artifact. CONCLUSION: The new generation 192-slice MDCT scanner offers several notable advantages for cochlear implant imaging compared with conventional MDCT. This technology provides important feedback regarding electrode position and course, which may help in future optimization of surgical technique and electrode design.

Radiologic Features of Sinonasal Tumors.

Imaging evaluation of sinonasal tumors is most often conducted with computed tomography, which excels at identifying the effects of these masses on adjacent osseous structures, and magnetic resonance imaging that is ideal for distinguishing pathologic masses from mucosal thickening and fluid that are common in the sinonasal spaces and depicting extension into the surrounding soft tissues, orbits, and intracranial compartment. Accordingly, the two studies are complementary exams and both are commonly utilized in the assessment of these masses. Less commonly, positron emission tomography can provide additional metabolic evaluation of potential metastatic disease in patients with malignant disease. While these imaging modalities are excellent for the portrayal of an abnormality, there is considerable overlap in the imaging appearance of these tumors and specific imaging manifestations linked to a particular tumor are frequently lacking. Therefore, while the mass may be readily identified, narrowing the differential diagnosis to a single specific entity is rare. Nevertheless, cross-sectional imaging plays an essential role in patient management and valuable guidance for successful biopsy or surgical resection in virtually all cases. This review emphasizes essential imaging manifestations that correlate with sinonasal tumors in general and highlight certain features that may implicate a specific disease process.

Extranodal Lymphoma of the Central Nervous System and Spine.

With a strong predilection for immunocompromised groups and a poorly explained increase in prevalence among those with normal immune status, lymphoma now accounts for approximately 6% of all primary brain tumors. Recent advances in multiagent chemotherapy and monoclonal antibody therapy have promoted longer-term survival, although a definitive cure remains elusive. Extranodal lymphoma of the spine is more often caused by secondary dissemination from systemic disease and less often the primary site of origin. This article reviews a broad spectrum of clinical, etiologic, and pathologic features that frequently intersect with common radiologic findings of this disease.

T2 Fluid-Attenuated Inversion Recovery Imaging of Uveal Melanomas and Other Ocular Pathology.

BACKGROUND/AIMS: This study describes patterns of intraocular lesions on T2 fluid-attenuated inversion recovery (FLAIR) imaging, exploring a prospective role of FLAIR imaging sequence in diagnosis and treatment. METHODS: A retrospective study of orbital magnetic resonance imaging (MRI) studies from the years 2000 to 2015 was performed. MRI sequences included: pre-contrast T1-weighted, T2-weighted, T2 FLAIR, and postcontrast T1 and T2 imaging gadolinium, which were evaluated by a neuroradiologist. Two cases of melanoma were correlated to their pathology. RESULTS: Twenty-four patients with intraocular pathology were evaluated. All lesions, regardless of pigmentation, revealed previously described melanotic patterns on T1- and T2-weighted images; 80% of 10 melanomas localized were hyperintense on T2 FLAIR, which better delineated lesion margins. All of the four inflammatory pathologies on T2 FLAIR were hyperintense, as were 80% of the amelanotic neoplasms. Pathology of two large uveal melanomas paralleled the findings seen on T2 FLAIR. CONCLUSIONS: T2 FLAIR appears beneficial in the demarcation of pigmented ocular lesions and may aid in determining protein content or previous treatment. Data also promote previous assertions that blood flow impacts intensity of lesions on T2 FLAIR. Further research is warranted.

From the archives of the AFIP: Oligodendroglioma and its variants: radiologic-pathologic correlation.

Oligodendroglioma is the third most common glial neoplasm and most commonly arises in the frontal lobe. It occurs in males more frequently, and the peak manifestation is during the 5th and 6th decades. Children are affected much less commonly. The clinical presentation is often of several years duration with most patients presenting with seizures, reflecting the strong predilection of this tumor to involve the cortical gray matter. Current histopathologic classification schemes recognize two main types of tumors: well-differentiated oligodendroglioma and its anaplastic variant. Less commonly, neoplastic mixtures of both oligodendroglial and astrocytic components occur and are termed oligoastrocytomas, with both well-differentiated and anaplastic forms. Surgical resection is the mainstay of initial treatment, and many patients experience a long progression-free period. Recent genotyping has revealed chromosomal loss of 1p and 19q as a genetic signature in most oligodendrogliomas, and these tumors respond favorably to chemotherapy. Hence, radiation therapy is now generally reserved for partially resected tumors and cases that failed to benefit from chemotherapy. At cross-sectional imaging, the tumor characteristically involves the cortical gray matter and frequently contains calcification. Robust enhancement is not a common feature and suggests transformation to a higher histologic grade. Advanced magnetic resonance imaging techniques and metabolic imaging play increasingly important roles in both pre- and postoperative assessment of these complex neoplasms.

From the archives of the AFIP: a comprehensive review of fetal tumors with pathologic correlation.

Fetal tumors are a diverse group of neoplasms, which are unique in their histologic characteristics, anatomic distribution, and pathophysiology. The biologic behavior of tumors in the fetus may differ dramatically compared with that of the same tumor detected later in life. Teratomas are the dominant histologic type and constitute the majority of both extracranial and intracranial neoplasms. Although often histologically mature, they may prove lethal because of their location and metabolic demands on the fetus. Large solid tumors may lead to cardiovascular compromise and hydrops fetalis. Extracranial teratomas are most commonly located in the sacrococcygeal area, followed by the head and neck, chest, and retroperitoneum. Fetuses with intracranial tumors have a poor prognosis regardless of histologic type. There are, however, two notable exceptions: lipomas and choroid plexus papillomas, both of which have a more favorable outcome. Neuroblastoma is the most common fetal malignancy. It may be either solid or cystic and is more often located on the right side. It typically has favorable biologic markers and stage at presentation. The prognosis for prenatally diagnosed cases is excellent. Other fetal neoplasms include soft-tissue tumors (both benign and malignant), leukemia, mesenchymal hamartoma of the kidney, and liver tumors (hemangioendothelioma, mesenchymal hamartoma, and hepatoblastoma).

Can Preoperative Imaging Predict Tumor Involvement of the Anterior Clinoid in Clinoid Region Meningiomas?

BACKGROUND: Anterior clinoid region meningiomas may infiltrate the bone over which they arise, therefore requiring an anterior clinoidectomy to achieve a Simpson grade 1 resection. A clinoidectomy, however, is not without risks. OBJECTIVE: We performed a study of diagnostic accuracy investigating whether preoperative imaging could predict tumor involvement of the clinoid, and thereby tailor the degree of bony removal. METHODS: Patients having undergone resection of a clinoid region meningioma between 2001 and 2011 were identified. Included in further analysis were those patients in whom a clinoidectomy was performed with subsequent pathologically confirmed presence or absence of tumor in the clinoid process on decalcified specimens. Two neuroradiologists, blinded to pathology results, independently reviewed available preoperative imaging and stated whether or not they anticipated the clinoid to be involved by tumor. Interobserver agreement and the ability to accurately predict tumor involvement of the clinoid were then analyzed. RESULTS: Sixty-two patients were included in the final analysis. Interobserver agreement was 100%. Sensitivity and specificity of preoperative imaging to predict tumor involvement was 89% and 52%, respectively, with positive and negative likelihood ratios of 1.85 and 0.20. Positive and negative predictive values were 73% and 76%, respectively. CONCLUSION: Preoperative imaging of clinoid region meningiomas can accurately predict the presence or absence of tumor involvement of the clinoid in only approximately 75% of cases. In light of the fact that a quarter of patients with radiographically negative clinoids will have tumor present on pathological analysis, we recommend a clinoidectomy for all clinoid region meningiomas.

From the archives of the AFIP: pilocytic astrocytoma: radiologic-pathologic correlation.

Pilocytic astrocytoma is the most common pediatric central nervous system glial neoplasm and the most common pediatric cerebellar tumor. This tumor has a noteworthy benign biologic behavior that translates into an extremely high survival rate-94% at 10 years-that is by far the best of any glial tumor. Most patients present in the first 2 decades, and clinical symptoms and signs are usually of several months duration and directly related to the specific location of the tumor. The cerebellum, optic nerve and chiasm, and hypothalamic region are the most common locations, but the tumor can also be found in the cerebral hemisphere, ventricles, and spinal cord. Surgical resection is the treatment of choice for all tumors, except for those involving the optic pathway and hypothalamic region, which may be treated with radiation therapy and chemotherapy. Cross-sectional imaging often demonstrates a classic appearance: a cystic mass with an enhancing mural nodule. Less common appearances are quite nonspecific. Surrounding vasogenic edema is rarely present, and this feature provides a valuable clue to the correct diagnosis. Accurate interpretation of imaging studies plays an essential role in directing treatment of these tumors, particularly when they arise in the optic pathway of patients with neurofibromatosis type 1. Disseminated disease and recurrence are extremely rare.

From the archives of the AFIP: medulloblastoma: a comprehensive review with radiologic-pathologic correlation.

Medulloblastoma is the most common pediatric central nervous system malignancy and the most common primary tumor of the posterior fossa in children. This highly malignant neoplasm occurs more frequently in males and usually before 10 years of age. Clinical symptoms and signs are generally brief, typically less than 3 months in duration, and reflect the strong predilection of this tumor to arise within the cerebellum, most often in the vermis. Although much less common, the disease may also occur in adults, usually in the 3rd and 4th decades of life. Surgical resection, radiation therapy, and chemotherapy have substantially lowered the mortality associated with this tumor, with 5-year survival rates now commonly well above 50%. Still, both dissemination at the time of diagnosis and recurrence remain obstacles in achieving a cure. The tumor has characteristic hyperattenuation on unenhanced computed tomographic scans that reflects the high nuclear-cytoplasmic ratio seen at histologic analysis. The tumor typically appears heterogeneous on images, findings that are related to cyst formation, hemorrhage, and calcification and that are even more pronounced with magnetic resonance (MR) imaging. Evidence of leptomeningeal metastatic spread is present in 33% of all cases at the time of diagnosis and is well evaluated with contrast-enhanced MR imaging of the brain and the spine. Although controversial, postoperative surveillance with MR imaging is performed at most institutions in the hope of facilitating a better outcome. With continued research, treatment of these common neoplasms should improve, perhaps even achieving a cure in the future.