Positron emission tomography using [18F] fluorodeoxyglucose and [11C] l-methionine to metabolically characterize dysembryoplastic neuroepithelial tumors.

Dysembryoplastic neuroepithelial tumors are unique and benign congenital tumors occurring frequently in children and adolescents. Differentiation from other low-grade tumors is important for management. Five patients with confirmed dysembryoplastic neuroepithelial tumors were studied with positron emission tomography using glucose and protein metabolic uptake in an attempt to categorize these tumors metabolically. Functional brain mapping also was obtained to aid in operative management. Results of the study conclude that dysembryoplastic neuroepithelial tumors, although having similar neuroimgaing characteristics to other low-grade tumors, are distinguished by a unique metabolic profile. They are inactive tumors with no significant glucose or protein metabolic activity. The combination of preoperative positron emission tomographic metabolic studies with functional brain mapping allowed for prediction of tumor type, defined eloquent areas of cortical function, and improved approach and resection of the tumors with minimal risk of neurologic impairment.

Positron emission tomography in children with neurofibromatosis-1.

Neurofibromatosis-1 is an autosomal dominant genetic disorder commonly associated with neuropsychological complications. Focal areas of high signal intensity on magnetic resonance imaging (MRI) scans occur commonly but have shown inconsistent correlation with neuropsychological problems. Positron emission tomography (PET) scans utilizing [18F]fluoro-2-deoxy-D-glucose and MRI studies were performed on 10 children with neurofibromatosis-1 and multiple focal areas of high signal intensity to evaluate the regional cerebral metabolic rate for glucose of these lesions and other central nervous system structures. Co-registered PET and MRI studies confirmed reduced glucose metabolism of large focal areas of high signal intensity. Visual inspection and semiquantitative analysis of PET images demonstrated thalamic hypometabolism and varying degrees of cortical inhomogeneity in all cases of neurofibromatosis-1 compared to normal controls. Although a primary defect of the thalamus or cerebral cortex has not been defined, the metabolic abnormalities of this study suggest a potential relationship between these structures and the neuropsychological dysfunctions noted in neurofibromatosis-1.

Magnetic resonance imaging in the evaluation of the brainstem.

Magnetic resonance (MR) images of the brainstem region from 100 normal or asymptomatic individuals were reviewed in addition to those of 17 patients with intra-axial brainstem lesions and 15 patients with extra-axial masses around the brainstem. MR was able to demonstrate consistently the normal anatomy of the brainstem and adjacent cisterns, though the distinction between gray and white matter was seldom possible with the present technology. Masses in and around the brainstem were all accurately identified on MR and its sensitivity was superior to that of x-ray computed tomography (CT). These study results show that despite its technical limitations, MR is presently the examination of choice for the evaluation of brainstem abnormalities and eventually it will undoubtedly replace metrizamide CT cisternography.

Magnetic resonance imaging of the orbit: a preliminary experience.

Eleven patients with various space-occupying lesions in the orbit were examined, using a 0.3-tesla superconducting magnet to assess the capabilities and limitations of magnetic resonance (MR) imaging in the investigation of orbital lesions. Although the images provided valuable anatomic data, the bright signal intensity of fat and the partial volume effects of large section thickness resulted in loss of resolution for small, low-signal-intensity structures. The limitations of MR imaging were also reaffirmed by the lack of visualization of calcifications and of the bony orbit. These preliminary results show that MR offers no advantage over x-ray computed tomography except for its lack of ionizing radiation. Further technical improvements are needed before MR imaging will be made useful in this area.

Head trauma evaluated by magnetic resonance and computed tomography: a comparison.

Magnetic resonance (MR) images and computed tomograms of 25 patients with head trauma were compared. MR proved to be superior in many ways for demonstrating extracerebral as well as intracerebral traumatic lesions. Isodense subdural hematomas, which present a diagnostic dilemma on CT images were clearly seen on MR, regardless of their varying CT densities. In a case of epidural hematoma, the dura mater was shown directly as nearly devoid of signal on MR. Direct coronal images provided excellent visualization of extracerebral collections along the peritentorial space and subtemporal area. In a patient with intracerebral hematoma, CT failed to demonstrate residual parenchymal changes in a 3-month follow-up study, but MR clearly depicted the abnormalities. The superiority of MR over CT was also well illustrated in a patient with post-traumatic osteomyelitis of the calvarium.

NMR imaging of the spine.

The usefulness of nuclear magnetic resonance (NMR) images in the evaluation of spinal disorders below the craniocervical junction was studied. Six normal subjects and 41 patients with various spinal abnormalities were examined. NMR proved capable of demonstrating important normal and pathologic anatomic structures; it was useful in the evaluation of syringohydromyelia and cystic spinal cord tumors, and the bright signal intensity of lipoma was quite impressive. In the evaluation of herniated disk, NMR images offered a new perspective by visualizing abnormal degradation of the signal intensity of the nucleus pulposus itself. NMR images were least valuable in the evaluation of spondylosis and spinal stenosis. Although NMR imaging of the spine is still in a very early developmental stage, the absence of both ionizing radiation and risks associated with contrast material makes it especially attractive as a new diagnostic method. This limited experience with currently available equipment suggests that, with technical refinement, the efficacy of NMR of the spine will increase.

Intracarotid chemotherapy of glioblastoma after induced blood-brain barrier disruption.

Intracarotid chemotherapy has been suggested as an additional mode of therapy in patients with brain tumors. Seven comatose patients received intracarotid 5-fluorouracil and adriamycin after intracarotid infusion of 25% mannitol to open the blood-brain barrier at the tumor site. Five of seven patients became fully functional for 3-12 months. Another 11 patients entered the study, of which nine are currently receiving therapy and are functional, and two have died, one from brain herniation. The results are encouraging and support the need for further research of this therapeutic method.

Megalocephaly and hypodense extracerebral fluid collections.

Computed tomographic (CT) scans were identified and reviewed for 25 pediatric patients with enlarged heads and extracerebral fluid collections that showed cerebrospinal fluid-like attenuation. Mild to moderate enlargement of the subarachnoid space over the convexity, interhemispheric fissure, and the lateral ventricles was observed in most of the cases. The CT findings are not specific, and it is not always possible to determine the nature of the extracerebral fluid, whether it lies in the subarachnoid space, the subdural space, or both. The differential diagnosis included subdural effusions, hygromas, preclinical or external hydrocephalus, hypodense subdural hematomas, megalocephaly, and possibly a normal variant. CT remains the method of choice for the initial study of these patients and for subsequent follow-up in selected cases.

The radiographic anatomy of surgical extracranial-intracranial anastomoses.

Microvascular surgical techniques have been developed that allow anastomosis between extracranial arteries and cortical branches of intracranial arteries distal to a stenotic, occluded, or diseased arterial segment. Indications for this procedure other than cerebrovascular occlusive disease are discussed. The radiographic anatomy of the various surgical bypasses is described.

Angiographic and computed tomographic correlation in cerebral venous angiomas.

Venous angioma of the brain is a rare congenital vascular anomaly. In the last few years there have been several reports on the angiographic appearance of this lesion, but very little has been written about the findings on computed tomography (CT). Angiographically, the arterial phase is normal, while the capillary phase might demonstrate a blush. The major abnormality is the venous phase, where multiple dilated medullary veins converge centrally into a large drainage vein. The two cases presented here correlate the angiographic and CT appearances. It is felt that, with a knowledge of these findings, an accurate diagnosis of this condition can usually be reached.

Proptosis secondary to pneumocele of the maxillary sinus.

The third known case of a pneumocele of the maxillary sinus is reported. Radiographic findings included hyperlucency of a maxillary sinus with generalized expansion of its borders. Bone dehiscence was also visible with tomography. The present case emphasizes a gradual onset of clinical signs and manifested primarily by proptosis. Possible mechanisms in the production of this deformity are discussed.