Journal of neuroimaging : official journal of the American Society of Neuroimaging
-
Evaluation of brain and spinal cord atrophy by magnetic resonance imaging (MRI) has become an increasingly important component of understanding the multiple sclerosis (MS) disease process. These destructive aspects of the disease develop early in the disease course. A growing body of data links brain and spinal cord atrophy to clinical impairment more closely than can be linked with conventional measures of overt lesions. ⋯ They compare the rate of atrophy among MS phenotypes and summarize the emerging data linking atrophy to neurological and neuropsychological impairment. Finally, they discuss the effect of disease-modifying immunotherapies on the rate of CNS atrophy in patients with MS. Future research to clarify the etiology and pathophysiology of brain and spinal cord atrophy should provide new targets for therapeutic development.
-
For more than a century, multiple sclerosis was viewed as a disease process characterized by oligodendrocyte and myelin loss, and research into the pathogenesis of multiple sclerosis was mainly focused on the mechanisms of inflammation. However, with development of more sophisticated neuroimaging and molecular biology techniques, attention has shifted to new aspects of pathogenesis of multiple sclerosis: axonal loss and neurodegeneration. Evidence is increasing that tissue destruction, primarily axonal loss and neurodegeneration, is a key element in the pathogenesis of multiple sclerosis. ⋯ However, these repair mechanisms eventually fail, and patients typically develop generalized brain atrophy, cognitive decline, and permanent disability. Although the exact mechanisms underlying central nervous system atrophy in patients with multiple sclerosis are largely unknown, evidence exists that atrophy may represent an epiphenomenon related to the effects of dynamic inflammation within the central nervous system, including demyelination, axonal injury, neuronal loss, Wallerian degeneration, and possibly iron deposition. This article summarizes the potential mechanisms involved in central nervous system atrophy in patients with multiple sclerosis.
-
Transcranial color-coded duplex sonography (TCCS), in contrast to "blind" conventional transcranial Doppler sonography (TCD), enables a sonographer to outline the intracranial bony and parenchymal structures, visualize the basal cerebral arteries in color, and measure angle-corrected blood flow velocities in a specific site of the artery in question. This makes measurements of flow velocity more valid than those obtained with conventional TCD. TCCS is becoming a reliable tool for detecting the occlusion and narrowing of major intracranial arterial trunks. ⋯ Large and medium-sized arteriovenous malformations can also be detected with TCCS. The rapid sonographic assessment of cerebral hemodynamics in a neurosurgical patient with increased intracranial pressure can guide further management. The use of sonographic contrast agents can increase the number of conclusive TCCS studies in patients with insufficient acoustic windows.
-
In multiple sclerosis (MS), the spinal cord is a common area of involvement, and its dysfunction is likely to be responsible for much of motor disability. It has been reported that atrophy in the cervical spinal cord occurs early and is detectable in patients presenting with a clinically isolated syndrome. ⋯ This review summarizes the underlying pathology responsible for spinal cord atrophy and the methods available to measure it. The relationships between spinal cord atrophy, other magnetic resonance imaging parameters, and clinical disability are also discussed.
-
Although conventional magnetic resonance imaging (cMRI) is widely used for diagnosing multiple sclerosis (MS) and monitoring disease activity and evolution, the correlation between cMRI and clinical findings is far from strict. Among the reasons for this "clinical-MRI paradox," a major role has been attributed to the limited specificity of cMRI to the heterogeneous pathological substrates of MS and to its inability to quantify the extent of damage in the normal-appearing tissue. Modern quantitative MRI techniques have the potential to overcome some of the limitations of cMRI. ⋯ Magnetic resonance spectroscopy can add information on the biochemical nature of such changes, with the potential to improve significantly our ability to monitor inflammatory demyelination and axonal injury. Finally, functional MRI might provide new insights into the role of cortical adaptive changes in limiting the clinical consequences of white-matter structural damage. This review outlines the major contributions given by MRI-based techniques to the diagnostic work-up of MS patients, to the understanding of the pathobiology of the disease, and to the assessment of the effects of new experimental treatments.