Magnetic resonance imaging in degenerative ataxic disorders.

MRI of the brain was performed in 53 patients with a variety of degenerative ataxias and related disorders and 96 control subjects. Atrophy of intracranial structures was not seen in patients with the pure type of hereditary spastic paraplegia, or in early cases of Friedreich's ataxia. In advanced Friedreich's ataxia there was atrophy of the vermis and medulla. The MRI features of early onset cerebellar ataxia with retained reflexes were variable, and suggest heterogeneity. In autosomal dominant cerebellar ataxias, most patients had cerebellar and brainstem atrophy, probably reflecting the pathological process of olivopontocerebellar atrophy; there was no clearly defined group with both clinical and imaging features of isolated cerebellar involvement. The MRI abnormalities in idiopathic late onset cerebellar ataxia were predominantly those of cerebellar and brainstem atrophy or pure cerebellar atrophy. The clinical and imaging features of brainstem abnormalities were discordant in several patients. Pure cerebellar atrophy was associated with slower progression of disability. Cerebral atrophy was common in the late onset ataxias. Cerebral white matter lesions, although usually few in number, were observed in significantly more patients than controls, particularly those aged over 50 years.     

Magnetic resonance imaging of experimental cerebral oedema.

Triethyl tin(TET)-induced cerebral oedema has been studied in cats by magnetic resonance imaging (MRI), and the findings correlated with the histology and fine structure of the cerebrum following perfusion-fixation. MRI is a sensitive technique for detecting cerebral oedema, and the distribution and severity of the changes correlate closely with the morphological abnormalities. The relaxation times, T1 and T2 increase progressively as the oedema develops, and the proportional increase in T2 is approximately twice that in T1. Analysis of the magnetisation decay curves reveals slowly-relaxing and rapidly-relaxing components which probably correspond to oedema fluid and intracellular water respectively. The image appearances taken in conjunction with relaxation data provide a basis for determining the nature of the oedema in vivo.     

Magnetic resonance imaging in pediatric neurologic disorders

We present our initial experience with magnetic resonance imaging (MRI) in 301 pediatric patients with a variety of neurologic disorders. MRI does not require ionizing radiation and can be done easily and safely in children. It is equal or superior to computed cranial tomographic (CT) scans in demonstrating most types of pediatric neurologic disorders. MRI is often superior to CT scans in demonstrating intracranial tumors, although both studies are usually abnormal in highly malignant tumors. No clear advantage was shown with either MRI or CT scans for fluid-filled intracranial lesions. Lesions of the brain stem and upper cervical region, such as Chiari malformation, are well delineated by MRI. Increased signal from the paranasal sinuses was frequently evident by MRI, but, in most instances, there was no clinical indication of sinus disease. Large arteries can be visualized as an area of diminished signal, and intracranial hemorrhage, dural sinus thrombosis, and cerebral infarction were demonstrated. The increased anatomic detail pictured by MRI allows the diagnosis of congenital defects, such as agenesis of the corpus callosum or septum pellucidum, that are not always apparent with CT scans. Although our experience with spinal cord lesions was not extensive, fluid-filled lesions within the cord can be reliably demonstrated.     

Magnetic resonance imaging of brain tumors

Since MR is a new imaging modality, a major question to answer is, "What is the role of MRI in relation to older, more traditional diagnostic techniques?" Several studies comparing CT and MRI for brain evaluation have shown MRI to be more sensitive, although not more specific. The advantages of MRI center around its ability to reveal abnormalities that may not be detectable or only poorly seen on CT. In cases in which only a nonspecific mass effect may be depicted on CT, the MR may define the precise extent and location of a tumor. Furthermore, MRI with its increased contrast discrimination and its ability to obtain images in many planes can better define the precise location of a lesion relative to key neuroanatomic structures. This is extremely important for optimal surgical and radiotherapy planning. The disadvantages of MRI include the fact that small calcifications cannot be seen and one cannot yet evaluate the presence of an altered blood-brain barrier. Despite these disadvantages, we feel that MRI should be the primary study for diagnosis of brain abnormalities. When an abnormality is detected and further information is desired, a complementary CT study should be performed in order to evaluate areas of blood-brain barrier alteration and the presence of abnormal calcification.     

Magnetic resonance imaging pattern recognition in hypomyelinating disorders

Hypomyelination is observed in the context of a growing number of genetic disorders that share clinical characteristics. The aim of this study was to determine the possible role of magnetic resonance imaging pattern recognition in distinguishing different hypomyelinating disorders, which would facilitate the diagnostic process. Only patients with hypomyelination of known cause were included in this retrospective study. A total of 112 patients with Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus-Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis, Salla disease and fucosidosis were included. The brain scans were rated using a standard scoring list; the raters were blinded to the diagnoses. Grouping of the patients was based on cluster analysis. Ten clusters of patients with similar magnetic resonance imaging abnormalities were identified. The most important discriminating items were early cerebellar atrophy, homogeneity of the white matter signal on T(2)-weighted images, abnormal signal intensity of the basal ganglia, signal abnormalities in the pons and additional T(2) lesions in the deep white matter. Eight clusters each represented mainly a single disorder (i.e. Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, infantile GM1 and GM2 gangliosidosis, Pelizaeus-Merzbacher-like disease and fucosidosis); only two clusters contained multiple diseases. Pelizaeus-Merzbacher-like disease was divided between two clusters and Salla disease did not cluster at all. This study shows that it is possible to separate patients with hypomyelination disorders of known cause in clusters based on magnetic resonance imaging abnormalities alone. In most cases of Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus-Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis and fucosidosis, the imaging pattern gives clues for the diagnosis.     

Magnetic resonance imaging of the brain in phenylketonuria

To investigate the correlation between the abnormalities of magnetic resonance imaging (MRI) of the brain and blood phenylalanine (Phe) levels in phenylketonuria (PKU) and hyperphenylalaninemia (HPA), we reviewed MRIs from 16 patients with early treated PKU and HPA. Their ages ranged from 4-24 years and were found by mass screening and treated from early infancy, and 5 patients with late detected PKU who were aged 24-33 years. The former patients had no remarkable neurological signs or symptoms. One patient of the latter had severe mental retardation and 3 patients had mild to border mental retardation. Axial T1-weighted and T2-weighted spin echo sequences, fluid attenuated inversion recovery MR sequences (FLAIR) through the brain were performed. The scans were graded according to the extent of increased signal intensity of white matter on T2-weighted and FLAIR sequences. To investigate the influence of plasma Phe levels, three approaches were used. Firstly an average of all yearly serial blood Phe concentration was calculated for each patient, then Phe was determined for a period of 6 months and 12 months prior to MRI, and also for their lifetime up to their age at the time this study began. These average blood Phe levels were classified into four categories: group A:Phe level below 5 mg/dl, group B:5-8 mg/dl, group C:9-12 mg/dl, group D:above 12 mg/dl. MRI findings were not significant in group A. Remarkable high signals of white matter were obtained in group C and D, except for one patient in group D whose MRI finding was normal. MRI findings correlated to long-term dietary control stronger than those of 6 months prior to MRI. The clinical significance of MRI abnormalities is still unclear, and further study is required to clarify the relationship of the MRI findings and clinical conditions.     

Magnetic resonance imaging of the child's brain

The most significant difference between magnetic resonance imaging (MRI) and computed tomography (CT) is that the former graphic representation of the cerebrospinal axis and its structures does not use ionizing radiation or the injection of contrast material. The physical principles of MRI and the very characteristic appearances of some pathological processes common in children require special study. Low-proton density areas are generally dark; the short T ₁ value is responsible for white matter appearing clear; inversion recovery sequences permit study of the progression of myelination.     

Magnetic resonance imaging of the fetal brain

US remains the key imaging technique for prenatal screening of CNS pathology. However, MR imaging of the fetal brain is a powerful tool to further characterize CNS anomalies, especially during the third trimester. The prognosis of CNS anomalies detected at fetal MR imaging is not always known. As such, management may be problematic with regards to medical interruption of pregnancy. A multidisciplinary approach is essential in order to insure comprehensive evaluation and management of the pregnancy.     

Magnetic resonance brain tumor imaging in canine glioma

This study investigates a canine model of experimental brain tumor. Particularly addressed was the usefulness of gadolinium contrast-enhanced MRI for differentiating brain tumor tissue from cerebral edema. Cultured canine glioma cells were injected into the left hemispheres of six adult mongrel dogs. All dogs developed brain tumors. Serum samples drawn prior to and serially after tumor inoculation showed development of antibodies reactive to the tumor. All tumors were visualized with MRI. Contrast-enhanced T1-weighted imaging was the most sensitive with gadolinium producing tumor enhancement due to blood-brain barrier breakdown. Gross and microscopic autopsy findings correlated well with MRIs.     

Correlates of brain-stem oculomotor disorders in multiple sclerosis. Magnetic resonance imaging

Three patients with focal brain-stem oculomotor disturbances (nuclear sixth nerve syndrome, sixth nerve palsy, bilateral internuclear ophthalmoplegia) as a consequence of multiple sclerosis have been studied with high-volume delayed computed tomography and high-field magnetic resonance imaging. In all of them, high-volume delayed computed tomography was inconclusive in the brain stem, but magnetic resonance imaging showed an area of prolonged T1 and/or T2 in the region appropriate to the oculomotor findings. Magnetic resonance imaging is the imaging technique of choice of small plaques in the brain stem. It can considerably aid clinicotopographic correlation in multiple sclerosis.     

Magnetic resonance imaging of the brain and spine

Summary The efficacy of magnetic resonance imaging (MRI) in the diagnosis of diseases of the central nervous system is reviewed. MRI, computed tomography (CT) and certain radionuclide studies are compared in the evaluation of intracranial tumours, cerebral vascular disease, multiple sclerosis and other white matter diseases, dementia, head injury, infection, epilepsy, spinal lesions and in paediatric central nervous system disorders. The measurement of cerebrospinal fluid volumes and dynamics by MRI is discussed. MRI most clearly has advantages where CT is degraded by bone hardening and streak artefacts (spine, skull base, posterior and temporal fossa, sella and parasellar regions) and in diseases in which the X-ray attenuation of the suspected lesion differs little from normal parenchyma (paediatric brain disorders, demyelination and dysmyelination, early oedema associated with infarction, infection or low-grade infiltrating neoplasm, subacute and chronic haemorrhage and lesions in the spinal subarachnoid space and cord). Elsewhere MRI and CT should be seen as complementary rather than competitive methods of imaging. In spite of an absence of information about the contribution of MRI to management decisions and a lack of rigorous, prospective controlled trials, MRI will play an increasing role in the diagnosis of diseases of the central nervous system.     

Magnetic resonance imaging of human brain macrophage infiltration

Macrophage tracking by magnetic resonance imaging (MRI) with iron oxide nanoparticles has been developed during the last decade for numerous diseases of the CNS. Experimental studies on animal models were confirmed by first clinical applications of MRI technology of brain macrophages for multiple sclerosis, ischemic stroke lesions, and tumors. As activated macrophages act in concert with other immune competent cells, this innovative MRI approach provides new functional data on the immune reaction in these CNS diseases. The MRI detection of brain macrophages defines precise spatial and temporal patterns of macrophage involvement that helps to characterize individual neurological disorders. This approach is being explored as an in vivo marker for the clinical diagnosis of cerebral lesion activity, in experimental models for the prognosis of disease development, and to determine the efficacy of immunomodulatory treatments under clinical evaluation. Comparative brain imaging follow-up studies of blood-brain barrier leakage by MRI with gadolinium-chelates, microglia activation by positron emission tomography with radiotracer ligand PK11195 and MRI detection of macrophage infiltration provide more precise information about the pathophysiological cascade of inflammatory events in cerebral diseases. Such multimodal characterization of the inflammatory events should help in the monitoring of patients, in defining precise time intervals for therapeutic interventions, and in developing and evaluating new therapeutic strategies.     

Magnetic resonance imaging in clinically isolated lesions of the brain stem.

Twenty-seven patients with an isolated brain stem syndrome, thought to be due to demyelination, were examined by magnetic resonance imaging (MRI). A brain stem lesion was identified in 25, and clinically silent lesions outside the brain stem were demonstrated in 20. MRI was more sensitive than evoked potentials in detecting brain stem and other lesions. The scan findings were compared with those in 23 patients with multiple sclerosis, who had chronic brain stem dysfunction, with particular reference to the distribution of abnormalities and the MRI characteristics of the lesions. The relaxation times, T1 and T2, of the lesions were measured by MRI. These values were seen to fall in serial studies of acute lesions, but remained unchanged in the chronic lesions. MRI may therefore allow the age of lesions to be assessed.     

Magnetic resonance imaging in parkinsonism.

MRI is a relatively simple, safe, in vivo technique that has proved to be of great value in differentiating patients with Parkinson's disease from those with atypical parkinsonism, and it is the first laboratory marker to be able to do so. By permitting the in vivo detection of increased iron in the nigra and striatum of patients with parkinsonism, MRI may also have provided a clue into the mechanism of cell death in neurodegenerative disorders. Finally it is conceivable that MRI scanning may serve as a screening tool that permits the early recognition of pathologic iron accumulation before the development of clinical symptoms. This is reasonable to anticipate for patients with atypical parkinsonism in whom large quantities of iron appear to accumulate in the putamen early in the disease. It is possible that with some refinement, abnormalities in the nigra may be detected on MRI with a higher level of certainty. In an era in which we may be able to provide neuroprotective therapy, MRI might be an important technique for defining a population of patients at risk for the development of Parkinson's disease who might benefit from presymptomatic therapy.