Publications (84) View all
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Chapter: fMRI of Human Visual Pathways
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ABSTRACT: Functional magnetic resonance imaging (fMRI) of the human brain provides images of changes in local blood flow and oxygenation that are evoked by sensory, motor, or cognitive events. Functional MRI has been used since 1991 [1] to identify areas of the brain that respond to visual stimulation and the performance of vision-related tasks. Increasingly, fMRI is accompanied by diffusion tensor imaging (DTI), which provides images of the speed and direction of diffusion of water molecules in the brain. Fortuitously, this allows remarkable differentiation of cerebral white mater and the delineation of a variety of major white matter tracts including vision-related pathways such as the optic radiations. This chapter focuses primarily on fMRI, but DTI data are also discussed where relevant. Together, the two methods provide a wealth of information about the anatomical and functional status of key components of the visual system in individual patients even in the presence of pathology. For example, an imaging-based map of the visual system can be helpful for planning and guiding surgical resection of tumors impacting critical vision-related brain structures. This is especially true when mass effects or previous surgeries have distorted the normal anatomy making it difficult to know where key structures are located and if they are still functional. In difficult cases, identifying the region of “closest approach” of a planned resection to the cortical representation of central vision or to the optic radiations can help to minimize the risk to eloquent neural tissue and thereby avoid significant treatment-induced vision loss while still permitting maximum therapeutic effect.12/2011: pages 485-511; -
Article: Causes of misinterpretation of cross-sectional imaging studies for dissection of the craniocervical arteries.
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ABSTRACT: OBJECTIVE: This review presents some of the more common causes of false-positive and false-negative interpretations of cross-sectional imaging studies showing, or designed to show, dissection of the carotid or vertebral arteries. CONCLUSION: Dissection of the craniocervical arteries is a diagnosis that can be very difficult on cross-sectional imaging studies such as CT angiography, MRI, and MR angiography.American Journal of Roentgenology 01/2011; 196(1):45-52. · 2.78 Impact Factor -
Article: Current imaging assessment and treatment of intracranial aneurysms.
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ABSTRACT: OBJECTIVE: This article reviews current neuroimaging techniques used for screening, diagnosis, and follow-up of patients with intracranial aneurysms as well as neuroendovascular therapeutic options available to patients. CONCLUSION: The diagnosis and management of intracranial aneurysms have evolved dramatically in the past 20 years. MR angiography and CT angiography allow radiologists to reliably and noninvasively diagnose most intracranial aneurysms. Nonoperative endovascular techniques for treating intracranial aneurysms are now making treatment increasingly safer and more effective.American Journal of Roentgenology 01/2011; 196(1):32-44. · 2.78 Impact Factor -
Article: Crossed aphasia in a patient with congenital lesion in the right hemisphere
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ABSTRACT: Background: Described over 100 years ago by Bramwell (1899) as an example of atypical cerebral dominance, crossed aphasia is a clinical condition where a lesion in the right hemisphere in a right-handed person leads to aphasia. Occurring worldwide only in a few cases, it is not known what initially leads to the ontogenetic lateralisation of language to the right brain. However, we know that certain kinds of pre-existing congenital lesions in the brain, in utero or post-partum, can usually impact the language lateralisation such that it develops in the opposite hemisphere. Aims: We present neurolinguistic data from a right-handed patient with crossed aphasia, who had an atypical subcortical crossed aphasia marked with a fractionated lateralisation of functions. Early in her life she had an unsuspected, pre-existing congenital (subcortical AVM) abnormality in the right hemisphere. Methods & Procedures: Clinical data in this single-participant study was obtained from a 20-year-old female who was seen for an evaluation of her residual language functions at a university speech and hearing clinic after her ruptured right subcortical AVM. The participant was reassessed 5 years after the first examination and also received treatment for impaired verbal output. Data taken from two diagnostic evaluations are compared and discussed. Outcomes & Results: The patient's language nonetheless lateralised to the right hemisphere without any obvious consequence of the subcortical AVM. This would not be puzzling since a silently sitting AVM itself may not generally interfere with lateralisation. However our participant exhibited an atypical allocation of functions. The left hemisphere appeared to have lost its dominance for speech to the right hemisphere, while it nevertheless maintained the limb praxis control, since the participant was right-handed from the outset. Interestingly the right hemispheric inherent visuospatial functions remained unimpaired, while its paralinguistic functions were impaired to a certain extent. Conclusions: We present evidence of an atypical language-cognitive lateralisation in crossed aphasia in a participant with a congenital (subcortical AVM) abnormality in the right hemisphere. We discuss the mechanisms that might have contributed to the atypical allocation of the functions.Aphasiology 12/2010; 25(1):27-42. · 1.32 Impact Factor -
Article: Nicardipine infusion for blood pressure control in patients with subarachnoid hemorrhage.
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ABSTRACT: To evaluate the efficacy, tolerability, and safety of nicardipine infusion in controlling the elevated blood pressure after subarachnoid hemorrhage (SAH). Nicardipine infusion was initiated if the individual pre-specified systolic blood pressure (SBP) level goal, mandated by the admitting neurosurgeon, was not met. Systolic and diastolic BPs were measured on admission, hourly during the infusion and 12 h before and after the infusion. Twenty-eight patients with SAH required 50 nicardipine infusions in order to achieve a mean SBP goal of 152 mmHg. The 3,112 extracted BP measurements showed that mean infusion SBP was significantly lower than admission and pre-infusion SBP (mean 146.5 vs. 177.1 and 155.6 mmHg, P < 0.001, respectively) and significantly higher than post-infusion SBP (146.5 vs. 142.6 mmHg, P = 0.002). Five infusions were stopped prematurely, because of hypotension (n = 3), emergent surgery (n = 1), and failure to reach the SBP goal (n = 1). Rebleeding was not observed in any patient. Nicardipine achieved SBP control in 59.9% of hourly infusion measurements, with a trend for higher proportion of success with higher SBP goals. In this study, nicardipine infusion was a safe and moderately effective treatment for BP control in patients with SAH. Although SBP during nicardipine infusion was higher than the pre-specified goal in a significant percentage of hourly observations, this may be due to the drug administration protocol and other factors such as analgesia and sedation.Neurocritical Care 10/2010; 13(2):190-8. · 2.47 Impact Factor
