Lhermitte-Duclos disease: a critical appraisal of different radiologic methods.
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Adult↗
Biomedical subjects
J Frahm
Publications and source records attributed to J Frahm.
Correlational imaging of thalamocortical coupling in the primary visual pathway of the human brain.
While the anatomy of the human brain is well defined, the functional connectivity of its structures is far less understood. Modern neuroimaging techniques offer the unique opportunity of visualizing physiologic activation in central nervous structures and of identifying the elements underlying distributed networks for information processing. Following improved spatial resolution of deoxyhemoglobin-sensitive magnetic resonance imaging, we were able to detect simultaneous signal changes in the lateral geniculate nucleus and primary visual cortex during periodic photic stimulation. Visualization of coupled activation by cross-correlation analysis resulted in the first demonstration of thalamocortical interaction in the primary visual pathway of the intact human brain.
Adult↗
The effect of acetazolamide on regional cerebral blood oxygenation at rest and under stimulation as assessed by MRI.
The sensitivity of gradient echo magnetic resonance imaging (MRI) to changes in cerebral blood oxygenation (CBO) has been introduced for mapping functional brain activation. Here, we report that this approach allows monitoring autoregulation in the human brain under vasodilatory stress. Following the administration of acetazolamide, signal intensities of deoxyhemoglobin-sensitive images increased in cortical and subcortical gray matter and to a lesser extent in white matter. This result reflects a venous hyperoxygenation stemming from an increase in cerebral perfusion with oxygen consumption remaining constant. In addition, pharmacologic induction of vasodilation attenuated activity-related MRI signal changes in the visual cortex under photic stimulation. Although intersubject variability was high, this finding indicates individually persisting autoregulatory responsiveness to functional challenge despite an "exhausted" reserve capacity. It is suggested that recording CBO by MRI will foster our understanding of modulation of vasomotor tone and cerebral perfusion. Furthermore, this technique may prove valuable for assessing the cerebrovascular reserve capacity in patients with carotid artery occlusive disease.
Acetazolamide↗
Functional cooperativity of human cortical motor areas during self-paced simple finger movements. A high-resolution MRI study.
Magnetic resonance imaging of changes in cerebral blood oxygenation (CBO) delineated areas of neural activation during self-paced unilateral middle finger tapping in five normal volunteers. Four contiguous imaging sections parallel to the bicommissural plane covered the hand area of the primary sensori-motor cortex bilaterally. All measurements were performed at 2.0 T using rapid gradient-echo sequences (TR/TE = 63/30 ms) with high spatial resolution (0.8 x 1.6 x 4 mm) and both strong (40 degrees flip angle) and weak (10 degrees) radiofrequency excitation pulses. This allows differentiation of flow and CBO contributions to the observed signal alterations. Functional cooperativity was analysed by a pixel-by-pixel correlation of signal intensity time courses with the stimulus protocol. Areas of activation included the contralateral primary motor cortex, the homologue part of the primary sensory cortex, the supplementary motor area (SMA) and the lateral premotor areas in all volunteers. Task-related activation of ipsilateral primary motor cortex above a threshold correlation coefficient of 0.5 was seen in two out of five volunteers (at 40 degrees) and one out of five (at 10 degrees) when performing the right-hand task. The present MRI findings readily demonstrate in single subjects that the SMA is involved in self-paced finger tapping. Only sparse activation in the ipsilateral primary motor cortex is consistent with the motor paradigm used.
Adult↗
Creatine deficiency in the brain: a new, treatable inborn error of metabolism.
In a patient with extrapyramidal movement disorder and extremely low creatinine concentrations in serum and urine, in vivo proton magnetic resonance spectroscopy disclosed a generalized depletion of creatinine in the brain. Oral substitution of arginine, a substrate for creatine synthesis, resulted in an increase of brain guanidinoacetate as the immediate precursor of creatine but did not elevate cerebral creatine levels. In contrast, oral substitution of creatine-monohydrate led to a significant increase of brain creatine, a decrease of brain guanidinoacetate, and a normalization of creatinine in serum and urine. Phosphorus magnetic resonance spectroscopy of the brain revealed no detectable creatine-phosphate before oral substitution of creatine and a significant increase afterward. Partial restoration of cerebral creatine concentrations was accompanied by improvement of the patient's neurologic symptoms. This is the first report of a patient with complete creatine deficiency in the brain. Magnetic resonance spectroscopy during arginine and creatine treatment point to an inborn error of creatine biosynthesis at the level of guanidinoacetete-methyltransferase.
Arginine↗
Proton spectroscopy in patients with Leigh's disease and mitochondrial enzyme deficiency.
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Brain Chemistry↗
In vivo proton magnetic resonance spectroscopy of the brain in a patient with L-2-hydroxyglutaric acidemia.
Morphologic appearance and metabolic disturbances of the brain of a patient with L-2-hydroxyglutaric acidemia were investigated with use of magnetic resonance imaging and localized proton magnetic resonance spectroscopy in vivo. Whereas magnetic resonance imaging revealed increased internal and external cerebrospinal fluid spaces as well as patchy white matter lesions, metabolic deviations included a 50% decrease of N-acetylaspartate (neuronal marker), a 75% increase of myo-inositol (glial marker), and a 40% decrease of choline-containing compounds in white matter relative to age-matched controls. A clinical deterioration of the patient was clearly reflected in a follow-up examination 22 mo later, resulting in a further reduction of N-acetylaspartate and a more pronounced enhancement of myo-inositol. No elevation of lactate was observed. The magnetic resonance spectroscopy findings are in line with a generalized neurodegenerative process in L-2-hydroxyglutaric acidemia but also suggest a defect in phosphatidyl inositol metabolism of glial cells.
Adolescent↗
Molecular self-diffusion of intracellular metabolites in rat brain in vivo investigated by localized proton NMR diffusion spectroscopy.
Molecular self-diffusion coefficients of water (0.75 +/- 0.05), N-acetylaspartate (0.27 +/- 0.04), creatines (0.27 +/- 0.04), and cholines (0.28 +/- 0.08) x 10(-5) cm2 s-1 were obtained from localized proton NMR spectra of rat brain in vivo using diffusion-weighted stimulated-echo (STEAM) sequences with a diffusion time of (delta--delta/3) = 17 ms.
Animals↗
Functional MRI of human brain activation at high spatial resolution.
Functional activation maps of the human visual cortex were obtained at a spatial resolution almost two orders of magnitude better than achievable by positron emission tomography and within measuring times of a few seconds. Transient alterations in the concentration of paramagnetic deoxyhemoglobin were conveniently detected at 2.0-T with use of RF-spoiled FLASH MRI sequences employing gradient echo times of 6 to 60 ms and voxel sizes of 2.5 to 39 microliters.
Adult↗
Nuclear magnetic resonance studies of human brain in vivo: anatomy, function, and metabolism.
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Brain↗
Alterations of brain metabolites in metachromatic leukodystrophy as detected by localized proton magnetic resonance spectroscopy in vivo.
The brain morphology and chemistry of seven children with late infantile (4/7) and juvenile (3/7) forms of metachromatic leukodystrophy (MLD) were investigated by magnetic resonance imaging (MRI) and localized proton magnetic resonance spectroscopy (MRS). Patients who were examined at least 6 months after the onset of symptoms (6/7) had severe leukodystrophic changes on MRI. Proton MRS revealed a marked reduction of the neuronal marker N-acetylaspartate in white and grey matter and elevated lactate in demyelinated areas. In contrast to other leukodystrophies MLD patients showed a generalized increase of brain myo-inositol (2- to 3-fold in white matter), indicating a specific role in the pathophysiology of demyelination in MLD.
Adolescent↗
Dynamic high-resolution MR imaging of brain deoxygenation during transient anoxia in the anesthetized rat.
Transient alterations in brain oxygenation during 60-s periods of anoxia were visualized at high spatial resolution (voxel size < or = 0.15 microliter) with the use of serial long echo time FLASH (fast low-angle shot) magnetic resonance images (measuring time > or = 6 s) of halothane-anesthetized rats in vivo. Difference images from normoxia and anoxia exploit the signal decrease associated with increased levels of paramagnetic deoxyhemoglobin in the arterial and venous blood pool. Insights into the spatial heterogeneity of oxygen deprivation are complemented by physiologic information from the time course of pertinent signal changes in different regions of the brain.
Animals↗
Diffuse white matter disease in three children: an encephalopathy with unique features on magnetic resonance imaging and proton magnetic resonance spectroscopy.
Amongst 21 children with unclassified white matter diseases three patients could be characterised by an identical clinical picture, magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (MRS) findings as a probably distinct entity. Following a normal early development they later showed rapidly progressive motor symptoms (ataxia, spasticity) leading to severe handicap within one or two years after onset. Later on bulbar symptoms, optic atrophy and epileptic seizures occurred. The MRI showed a diffuse homogeneous hypodensity of the white matter almost identical to the signal of the ventricles. MRS revealed a near total absence of N-acetylaspartate, choline and creatine and an increase of lactate and glucose. One girl and one boy were siblings, indicating an autosomal recessive trait.
Aspartic Acid↗
Absolute concentrations of metabolites in the adult human brain in vivo: quantification of localized proton MR spectra.
In vivo concentrations of cerebral metabolites were obtained by means of 52 single-voxel, localized proton magnetic resonance (MR) spectroscopic examinations of different regions of the brain performed in 26 healthy adults aged 21-32 years. The study was performed at 2.0 T with use of a circularly polarized head coil to ensure homogeneous radio-frequency excitation and signal reception. Proton MR spectra were obtained in the stimulated-echo acquisition mode under fully relaxed conditions (repetition time > or = 6,000 msec) and at short echo times (20 msec) to minimize corrections due to T1 and T2 attenuation and depict the spectra of metabolites with strongly coupled resonances. Absolute concentrations were obtained by means of calibration of resonance signal areas with those of pertinent metabolite solutions from separate studies and correction for coil loading and partial volume effects (eg, with perfused capillary networks and cerebrospinal fluid). The results provide a quantitative basis for studies of both normal human neurochemistry in vivo and metabolic alterations in diseases of the brain.
Adult↗
Multiple sclerosis in children: cerebral metabolic alterations monitored by localized proton magnetic resonance spectroscopy in vivo.
In vivo proton magnetic resonance spectroscopy of 8 children (7-16 years) with established multiple sclerosis revealed distinct alterations in regional cerebral metabolism associated with different aspects of the disease: (1) Localized proton spectra (2 to 4-ml volumes of interest) from multiple sclerosis plaques were generally characterized by a decrease in N-acetylaspartate and creatine, and an increase in cholines and myo-inositol relative to age-matched control subjects, (2) neither chronic nor enhancing plaques (by gadolinium-diethylenetriamine pentaacetic acid) during an acute exacerbation showed elevated levels of lactate or lipids, (3) spectra from adjacent white matter that did not appear suspicious in magnetic resonance images were similar to those of normal control subjects, and (4) cortical gray matter related to neighboring multiple sclerosis lesions showed a notable reduction of N-acetylaspartate. The present results show that functional impairment in multiple sclerosis is linked to gross metabolic disturbances of neuronal cell chemistry. We suggest that focal demyelination is accompanied by increased membrane precursors of proliferative turnover and is associated with secondary neuronal shrinkage or loss, perhaps extending into related cortical gray matter.
Adolescent↗
Diffusion imaging of the human brain in vivo using high-speed STEAM MRI.
This paper describes a new method for diffusion imaging of the human brain in vivo that is based on a combination of diffusion-encoding gradients with high-speed STEAM MR imaging. The single-shot sequence 90 degrees-TE/2-90 degrees-TM-(alpha-TE/2-STE)n generates n = 32-64 differently phase-encoded stimulated echoes STE yielding image acquisition times of 576 ms for a 48 x 128 data matrix. Diffusion encoding is performed during the first TE/2-interval as well as during each readout period. Phantom studies reveal a quantitative agreement of calculated diffusion coefficients with literature values. EKG triggering completely eliminates motion artifacts from diffusion-weighted single-shot STEAM images of human brain in vivo. While signal attenuation of the cerebrospinal fluid (CSF) is predominantly due to flow, that observed for gray and white matter results from diffusion. Evaluated diffusion coefficients yield (1.0 +/- 0.1) x 10(-5) cm2 s-1 for gray matter, (0.5 +/- 0.1) x 10(-5) cm2 s-1 for white matter with the diffusion encoding parallel to the main orientation of the myelin sheath of the neurofibrils, and (0.3 +/- 0.1) x 10(-5) cm2 s-1 for white matter and a perpendicular orientation. All studies were performed at 2.0 T using a conventional 10 mT m-1 gradient system.
Brain↗
Decrease of glucose in the human visual cortex during photic stimulation.
Localized proton NMR spectroscopy was used to study cerebral metabolism in the visual cortex of healthy adults during rest and photic stimulation. Basal lactate levels showed considerable interindividual differences ranging from below detectability (less than 0.3 mM) to about 1 mM without consistent alteration during photic stimulation. Local brain glucose levels were significantly reduced (approximately 50%) during the entire period of photic stimulation and recovered to resting levels (approximately 0.8 mM) within 10 min after the end of stimulation. This decrease reflects the establishment of a new equilibrium due to enhanced delivery (blood flow) and enhanced consumption. The absence of lactate accumulation supports the hypothesis of a rapid efflux of lactate from brain tissue under activated conditions.
Adult↗
Acute demyelinating disease. Classification and non-invasive diagnosis.
Five young patients are described with biopsy-proven acute demyelinating disease. Two cases are classified as Schilder's disease, a particular childhood form of multiple sclerosis (MS) with atypical clinical manifestation, normal or atypical CSF-findings and large bilateral lesions in magnetic resonance imaging (MRI). Two further cases presented with a fulminant bout of MS with typical clinical picture and CSF-findings; they are classified as Marburg's disease. The last case was an acute second bout of classical MS. The biopsy seemed to be justified in 4 cases, but unnecessary in the last case. Localized proton magnetic resonance spectroscopy (MRS) performed in one case allowed us to examine the focal cerebral abnormalities directly and non-invasively. The spectra revealed a pattern typical of acute demyelination suggesting potential for a replacement of biopsy in the future.
Adult↗