PubMed · 14270893
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J S RIESCO-MAC-CLURE. 1964. CALORIC TESTS: METHODS AND INTERPRETATION.. https://pubmed.ncbi.nlm.nih.gov/14270893/
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Diffusion weighted MRI offers the possibility to study the course of the cerebral white matter tracts. In the present manuscript, the basics, the technique and the limitations of diffusion tensor imaging and anisotropic diffusion weighted MRI are presented and their applications in various neurological and neurosurgical diseases are discussed with special emphasis on the visual system. A special focus is laid on the combination of fiber tract imaging, anatomical imaging and functional MRI for presurgical planning and intraoperative neuronavigation of lesions near the visual system.
The application of functional magnetic resonance imaging (fMRI) in studies of the visual system provided significant advancement in our understanding of the organization and functional properties of visual areas in the human cortex. Recent technological and methodological improvements allowed studies to correlate neuronal activity with visual perception and demonstrated the ability of fMRI to observe distributed neural systems and to explore modulation of neural activity during higher cognitive processes. Preliminary applications in patients with visual impairments suggest that this method provides a powerful tool for the assessment and management of brain pathologies. Recent research focuses on obtaining new information about the spatial localization, organization, functional specialization and participation in higher cognitive functions of visual cortical areas in the living human brain and in further establishment of the method as a useful clinical tool of diagnostic and prognostic significance for various pathologic processes affecting the integrity of the visual system. It is anticipated that the combined neuroimaging approach in patients with lesions and healthy controls will provide new insight on the topography and functional specialization of cortical visual areas and will further establish the clinical value of the method for improving diagnostic accuracy and treatment planning.
To date functional magnetic resonance imaging (fMRI) has not been extensively used in presurgical evaluation of patients with intractable epilepsy. Patient S.P. presented with left frontal originating seizures, secondary to a large porencephalic cyst that encompassed much of his occipital and temporal cortex and a substantial portion of ipsilateral parietal cortex. Nevertheless, S.P. did not demonstrate any gross impairments of praxis or speech. Scalp electroencephalogram (EEG) telemetry revealed reduced background activity in the left hemisphere, an absence of identifiable normal sleep states, and confirmed the left frontal origin of his seizures with a prolonged postictal state, suggesting that the remaining cortex in S.P.'s left hemisphere did not function normally despite his apparently normal appearance. Dichotic listening results also suggested that S.P. had an atypical language representation suggestive of either bilateral or right hemisphere speech representation. Surgical intervention to remove the remaining left hemisphere cortex was a serious consideration for treatment of S.P.'s seizures. We used fMRI to evaluate whether or not the remaining cortex in S.P.'s left hemisphere supported any cognitive or motor functions. Even though the volume of cerebral cortex was severely reduced and displaced in the left hemisphere, fMRI revealed significant activation in this remaining tissue in response to motor, somatosensory, and word generation tasks. In other words, we were able to demonstrate using fMRI that the remaining tissue in S.P.'s left hemisphere continued to support some motor and cognitive functions. The possible implications of these findings in terms of functional reorganisation are discussed briefly.