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.

Chronic cerebral vasospasm: effect of calcium antagonists.

The efficacy of the calcium antagonists nifedipine and nimodipine was evaluated in a multiinjection canine model of severe chronic cerebral vasospasm. Each of 21 adult mongrel dogs (15 to 20 kg) was assigned to one of four experimental groups. All animals received a total of 15 ml of fresh, unheparinized arterial blood via three cisterna magna injections. Selective left vertebral arteriography was performed 1 week before and exactly 7 days after the simulated subarachnoid hemorrhage. Treatment with calcium antagonists was initiated at 24 hours and continued for 7 consecutive days. Comparisons were based on the percentage of reduction in basilar artery diameter. On a milligram/kilogram basis, we used the manufacturer's maximal recommended daily dosages of nifedipine, whereas the dosages of nimodipine used were 3 to 7 times greater than that reported to be therapeutically effective in reducing the incidence of severe deficits from vasospasm in patients with aneurysmal subarachnoid hemorrhage. In this laboratory trial, systemic treatment with calcium antagonists did not prevent or significantly reduce chronic arterial narrowing. In the control group, spasm reduced basilar artery diameter an average of 71% +/- 11 (SD). In the group treated with nifedipine, 10 mg orally every 6 hours, vessel diameter was reduced an average of 58% +/- 13%. In those animals treated with nimodipine, 20 or 40 mg orally every 4 hours, the basilar artery diameter was decreased an average of 59% +/- 8 and 56% +/- 7, respectively. A preliminary trial using direct intracisternal administration of these agents demonstrated increased vessel diameter within 20 minutes in four of six animals, supporting other reports that this route of administration may prove more efficacious in the treatment of chronic cerebral vasospasm.

Chronic cerebral vasospasm: effect of volume and timing of hemorrhage in a canine model.

The effect of altering the volume and timing of hemorrhage on the severity of spasm was studied in a canine model. All animals received three cisterna magna injections of fresh unheparinized autologous arterial blood. Selective left vertebral arteriograms were obtained during the week before and exactly 7 days after the initial subarachnoid injection. Increasing volumes of hemorrhage (from 9 to 15 ml of blood) delivered over 24 hours produced increasingly more severe arterial spasm, with reductions in basilar artery diameter of 37% +/- 14 (SD) and 58% +/- 15, respectively. Delay of the final injection of blood to 96 hours in the 15-ml hemorrhage group resulted in even more intense spasm, with an average 71% +/- 12 reduction in basilar artery diameter. Serial angiographic evaluation demonstrated the resolution of spasm in this group over approximately 3 weeks. Finally, small, late rebleeding episodes resulted in the rapid onset of intense spasm. Our results support the clinical impression of previous studies that the severity of spasm is related to the volume of hemorrhage and, in addition, suggest that the time course of hemorrhage may play a significant role in determining the overall severity of chronic cerebral vasospasm.

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.

Acute fulminant toxoplasma meningoencephalitis in a homosexual man.

A homosexual man with a history of sexually transmitted infections including recent giardiasis and high cytomegalovirus (CMV) titer was admitted with generalized weakness, headache, and depression. He rapidly became comatose and developed signs of increased intracranial pressure. CT scan revealed a right cerebral lesion. Pathologic examination disclosed an acute necrotizing granulomatous toxoplasmosis involving the cerebrum. This case represents an example of an opportunistic infection in a male homosexual associated with fulminant clinical course, probably on the basis of immune deficiency.

Cerebral revascularization during barbiturate coma in primates and humans.

Extracranial-intracranial arterial bypass was performed in five baboons to assess the effectiveness of the procedure in preventing acute cerebral ischemia following middle cerebral artery occlusion in our primate model. Thirty minutes following middle cerebral artery occlusion, the animals were placed in barbiturate coma while the extracranial-intracranial artery bypass was being completed. In the three animals with patent extracranial-intracranial arterial bypasses, infarction was prevented. In the two with occluded extracranial-intracranial arterial bypasses, a large infarction in the territory of the middle cerebral artery occurred. In a clinical correlate, postoperative ischemia was presumably prevented in three patients by barbiturate administration and revascularization for unanticipated intracranial vessel occlusion.

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.

Spontaneous opening of large occipital-vertebral artery anastomosis during embolization. Case report.

A patient undergoing external carotid artery therapeutic embolization for obliteration of a dural arteriovenous malformation suddenly developed a large occipital artery to vertebral artery shunt. A devastating stroke was averted because the appearance of the shunt was observed by fluoroscopy, the embolization was stopped, and the shunt verified on a subsequent angiogram. The risk of external carotid artery embolization without constant fluoroscopic control is emphasized.

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.

Temporal sequencing of verbal and nonverbal materials: the effect of laterality of lesion.

The effect of laterality of cerebral lesion on sequencing ability, which is an ability to process two or more stimulus events with respect to the order in which they occur, was examined. Patients with either left or right hemisphere lesions performed on verbal and nonverbal sequencing tasks. Left hemisphere lesioned patients were inferior to the right hemisphere lesioned patients on verbal sequencing tasks, while the right hemisphere lesioned patients were inferior to the left hemisphere lesioned patients on nonverbal sequencing tasks. Impaired performance of the right hemisphere lesioned patients on sequencing tasks raises questions with respect to the notion that sequencing per se is processed in the left hemisphere. Our results demonstrate that sequencing ability, as many other abilities, follows the rule of material-specific laterality of hemispheric asymmetry: the left hemisphere associated with verbal sequencing ability and the right hemisphere associated with nonverbal sequencing ability.

Congenital arteriovenous malformation of the head and neck.

A discussion of congenital arteriovenous malformation of the head and neck based on five patients followed from three to twenty years is presented. Definition of the lesion and its progression as followed by angiography is described. The poor response to surgery is ascribed to the ischemic nature of the area of involvement. The concept of supplying normal tissue with normal vascularity to the involved area is advocated.

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.