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Biomedical subjects

W Grodd

Publications and source records attributed to W Grodd.

At least 91 records · Page 5Linked to original sources
PubMed1996

Impaired procedural learning after damage to the left supplementary motor area (SMA).

Two paradigms of procedural learning, serial reaction time and tracking tasks, were given to a patient with damage to the supplementary motor area (SMA) of the left mesiofrontal cortex. This patient exhibited impaired procedural learning during the serial reaction time test and mirror reversed tracking. Unreversed tracking performance was normal. Therefore the SMA--as well as the cerebellum and the striatum--participate in the development of skills requiring internal elaboration of motor behaviour.

Adult↗
PubMed1996

Cerebral activity during visual stimulation: a positron emission tomography and functional magnetic resonance imaging study.

Stimulation of cerebral areas induces a regional increase in blood flow and metabolism. Positron emission tomography (PET) is an established procedure to localize cerebral regions of enhanced activity. Exposure to a radioactive indicator and limited spatial and temporal resolution are disadvantages of this method as compared with other imaging techniques, but anatomical orientation can be improved by matching PET images with high-resolution magnetic resonance imaging (MRI) scans. Recently, functional MRI (fMRI) has arisen as an alternative method. This procedure presumably detects changes in the paramagnetic properties of hemoglobin, depending on its oxygenation state, as well as an increased regional blood flow in activated cerebral areas. These structures can be visualized using sensitive scanning techniques and appear with bright signal intensities. Visual stimulation was performed with the help of a high-resolution color VDU for PET registration and of an LCD video projector for fMRI (1.5 T). Hemifield stimulation as well as subtraction between images of flickering and stable random dot stimuli showed a preferential activation of the primary visual cortex. In addition, the first MRI results obtained during stimulation with moving gratings are demonstrated; hereby, preferentially extrastriate regions presumably responsible for motion detection were activated.

Adult↗
PubMed1995

[Functional magnetic resonance tomography of psychological functions exemplified by experimentally induced emotions].

Changes in regional cerebral blood oxygenation during experimentally modified psychological activation can be measured with functional magnetic resonance imaging (fMRI). fMRI is a new imaging technique for perfusion-based signal intensities of the brain without the necessity of radioactivity and with superior anatomical and temporal resolution compared to positron emission tomography (PET). In this study a T2* FLASH sequence (TR 240ms, TE 60ms, slice thickness 4 mm, alpha = 40 degrees, matrix 64 x 128) was used to investigate changes in signal intensity within the temporal lobe and the amygdala during experimentally induced emotions. Visual stimuli of happy [sad] facial portraits were presented to volunteers to induce changes in the subjects' mood while lying in the tomograph. In agreement with a previous PET study, a significant increase in signal intensity in the left amygdala was found during induction of a sad mood, while no comparable effect was visible during induction of a happy mood.

Adult↗
PubMed1994

The effects of linearly increasing flip angles on 3D inflow MR angiography.

As recently demonstrated, spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using RF pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. We developed a model for calculating the signal distribution of proton flow within the excitation volume (slab) for different ramp slopes and compared the results with the measured distribution for the lower-leg arteries. The ramp pulses were generated using the Fourier transformation of the desired excitation profiles. With a bandwidth of 6 kHz and a pulse length of 2.56 ms satisfactory ramps with variable slopes were generated and applied in a standard flow-compensated 3D FISP sequence. The effects on the signal distribution in the resulting angiograms of the lower limbs revealed a considerable reduction of saturation losses in agreement with the calculations. Calculated optimal ramp slopes are provided for flow velocities ranging from 5 to 50 cm/s and excitation volumes ranging from 5 to 25 cm.

Algorithms↗
PubMed1994

The "dural tail" adjacent to meningiomas studied by dynamic contrast-enhanced MRI: a comparison with histopathology.

We examined 32 patients with intracranial tumors (17 meningiomas, 8 neuromas, 7 pituitary adenomas) by conventional and dynamic contrast-enhanced MRI. Our aim was to clarify whether the pathological dural contrast enhancement adjacent to meningiomas (the "dural tail") is specific to meningiomas and, more important, whether it represents neoplastic dural infiltration or hypervascularization as a tumor accompanying reaction. A "dural tail" was found in 9 of 17 meningiomas. None of the other extra-axial tumours (neuromas, pituitary adenomas) showed comparable dural enhancement. Dynamic examinations with an ultrafast single slice imaging technique (snapshot-FLASH) after a bolus injection of contrast medium showed a "dural tail" in seven out of these nine meningiomas, while in two cases the "dural tail" turned out to be a cortical vein with a characteristic dynamic contrast enhancement pattern. In the dynamic study all seven "dural tails" were found to have earlier, steeper contrast enhancement than the corresponding tumours. All the tumours and part of the adjacent dura mater in four of the seven meningiomas with dural enhancement were examined histopathologically. In none of these four cases was neoplastic tissue found more than 2 mm away from the main tumour. The results strongly support the suggestion that the "dural tail" adjacent to meningiomas represents a hypervascular, non-neoplastic dural reaction.

Adenoma↗
PubMed1994

[MR angiography of the neck vessels with optimized linearly increasing flip angles].

Spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using radio-frequency (RF) pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. MR angiograms of the cervical arteries of five healthy volunteers and eleven patients suffering from stenosis of the internal carotid arteries were acquired using a standard flow-compensated 3D FISP sequence with a single volume technique. Compared with the conventional MR angiograms acquired with constant flip angles, the MR angiograms could be considerably improved using the ramp pulses. Especially the distal parts of the vessels were depicted more clearly due to significantly reduced saturation effects. Since the vessel signal largely depends on the shape of the ramp pulses, we developed a model for calculating the signal distribution of the flowing protons for different ramp shapes and a given excitation volume (slab). The calculated signals were largely consistent with the signals in the MR angiograms, thus permitting numerical optimization of the shape of the ramp pulses for the cervical arteries. This optimized shape of the ramp pulse provided a high homogeneous vessel signal across the slab.

Blood Flow Velocity↗
PubMed1994

Congenital hemiparesis and periventricular leukomalacia: pathogenetic aspects on magnetic resonance imaging.

The authors report on the clinical examination and magnetic resonance imaging (MRI) of 41 children (29 term and 12 preterm) whose diagnosis of congenital hemiparesis was confirmed after the first year of life. Periventricular leukomalacia was the most predominant MRI finding (found in 15 term and eight preterm infants). The uniform pattern of lesions observed through MRI (without clear correlation with gestational age) suggests a common aetiopathogenesis in this subgroup. Comparison of these MR images with the periventricular leukomalacia observed in preterm children with spastic diplegia supports the thesis that ischaemia occurring between the 28th and 35th weeks of gestation could be the main cause.

Adolescent↗
PubMed1993

Systemic vasculitis positive for circulating anti-neutrophil cytoplasmic antibodies and with predominantly neurological presentation.

A 57-year-old male patient suffering from dramatically deteriorating diffuse and focal central nervous system symptoms was admitted to hospital after a short prodromal period in a somnolent state. He was diagnosed as having systemic vasculitis positive for circulating anti-neutrophil cytoplasmic antibodies, primarily involving the brain, but also most other organ systems. Circulating anti-neutrophil cytoplasmic antibodies are highly specific for Wegener granulomatosis, though they have been detected in rare cases of other vasculitic syndromes. Central nervous system lesions as presenting signs in Wegener granulomatosis have to be regarded as rare. This case nonetheless suggests that Wegener granulomatosis has to be considered in patients with a predominantly cerebral manifestation of a vasculitic syndrome.

Antibody Specificity↗
PubMed1993

Numerically optimized RF-refocusing pulses in localized MR proton spectroscopy.

The slice selection properties of three different soft refocusing-pulses (sinc-pulse, Hanning filtered sinc-pulse, and the numerically optimized reburp-pulse) within a standard double spin-echo sequence for localized proton spectroscopy were examined and compared. The slice profiles were measured acquiring two-dimensional images of the selected volumes of interest (VOI) appending a gradient-echo imaging part at the end of the spectroscopic part of the sequence. A comparison of the reached signal strength with the different pulses using the same voxel size (same Full Width Half Maximum, FWHM) was performed by in vitro and in vivo measurements. Additionally theoretical calculations using the Schrödinger equation for spin 1/2 particles in combination with a phase averaging method that takes into account the magnetic field spoiling and selection gradients of the spectroscopy sequence were performed. Calculated and measured slice profiles did well correspond. The numerically optimized reburp-pulse showed significant better slice selection and phase behaviour properties compared to the sinc-pulses. Further, a signal gain of about 20% was measured using the reburp-pulse, which was in good agreement with the calculated signal gain of 23%.

Adolescent↗
PubMed1993

Proton spectroscopy in five patients with Leigh's disease and mitochondrial enzyme deficiency.

Five children with Leigh's disease and progressive neurological symptoms were compared with 14 control children. In all patients, MRI showed bilateral lesions of the putamina and caudate heads. Serum lactate was normal for four of the children, and CSF lactate slightly elevated for three. Volume-selective proton MR spectroscopy (1H-MRS) of the basal ganglia in the Leigh patients revealed elevated lactate, giving further evidence for a defect of energy metabolism in the brain. 1H-MRS is an important tool for non-invasive brain tissue analysis in Leigh's disease, particularly in the absence of peripheral lactate elevation.

Acidosis, Lactic↗
PubMed1993

Uncommon chiasmal lesions: demyelinating disease, vasculitis, and cobalamin deficiency.

We report on eight patients who presented for evaluation of unexplained visual loss. They all showed a typical chiasmal visual field defect (bitemporal hemianopia, junction scotoma). In all patients, high-resolution computer-assisted tomographic (CT) scans of the sellar region were normal, and neither the medical history nor additional ophthalmological findings pointed to any explanation for the underlying disease. Six patients seemed to have suffered from chiasmal optic neuritis. Magnetic resonance imaging (MRI) scans could elucidate the diagnosis in five cases: white-matter lesions typical of multiple sclerosis (MS) were found and, additionally, in four cases an enlargement of the chiasm or barrier defect was revealed in post-gadolinium MRI. In one patient, MRI was normal. He recovered completely after megadose steroid therapy. One patient developed motoric symptoms of MS during the following year, another patient had mild sensory symptoms and recurrence of severe optic neuritis. An MR-proven chiasmal lesion due to a leukocytoclastic immunovasculitis combined with small subcortical white-matter lesions was diagnosed in another patient. The field defects disappeared spontaneously. In a 28-year-old woman a low vitamin B12 level was found in routine blood samples. Parenteral vitamin B12 substitution led to an almost complete recovery of the visual field defects. Chiasmal optic neuritis may occur isolated or during the course of MS. Megadose steroids may be of value if contraindications have been ruled out. A chiasmal visual field defect caused by vitamin B12 deficiency is very uncommon. A similar case was reported in 1961.

Adult↗
PubMed1993

Normal and abnormal patterns of myelin development of the fetal and infantile human brain using magnetic resonance imaging.

Magnetic resonance imaging allows a noninvasive assessment of myelination during normal brain maturation as well as the detection of genetically determined and acquired diseases that affect the synthesis and maintenance of myelin. If this high sensitivity of magnetic resonance imaging for white matter changes is completed by adequate clinical and biochemical information, a unique diagnostic tool is available to gain new insights in the formation of myelin and pathogenesis of myelin disorders.

Brain↗
PubMed1991

Superficial siderosis of the central nervous system. A 37-year follow-up of a case and review of the literature.

The course of a patient suffering from superficial siderosis of the central nervous system for 37 years is presented and diagnostic and therapeutic approaches are evaluated. The syndrome is clinically defined by slowly progressing deafness, cerebellar ataxia, myelopathy and neuropsychological deficits in combination with recurrent xanthochromia of the cerebrospinal fluid with siderophages. The diagnosis may be confirmed by computed tomography, which shows degeneration of the cerebellar vermis, and by magnetic resonance imaging, demonstrating iron deposits on the surface of brain, brain stem and spinal cord. Therapy should seek to identify and remove the source of bleeding, since pharmacotherapy with iron-depleting drugs is of limited effectiveness.

Brain Diseases↗
PubMed1991

Early onset cerebellar ataxia with retained tendon reflexes. Clinical, electrophysiological and MRI observations in comparison with Friedreich's ataxia.

Fourteen patients with the clinical diagnosis of early onset cerebellar ataxia with retained tendon reflexes (EOCA) were examined and compared with 11 patients with Friedreich's ataxia (FA). The mean age of onset in EOCA was 15.9 +/- 6.0 yrs (FA: 14.0 +/- 5.7 yrs). Annual progression rate and the percentage of patients who were wheelchair-bound was lower in EOCA as compared with FA, although the difference did not reach statistical significance. The latency until becoming wheelchair-bound, however, was significantly longer in EOCA than in FA. The segregation ratio in EOCA was significantly lower than 0.25. Clinically, EOCA and FA patients presented with a progressive cerebellar syndrome. Associated symptoms, such as muscle wasting, sensory disturbances, foot deformity, scoliosis and electrocardiographic abnormalities were encountered less frequently in EOCA than in FA patients. The electrophysiological findings in EOCA were variable and pointed to axonal degeneration in peripheral nerves and central pathways. Posturographic measurements revealed a higher incidence of anteroposterior sway direction in EOCA as compared with FA, suggesting a cerebellar type of ataxia in EOCA. Eleven out of the 14 EOCA patients had cerebellar atrophy in MRI. The characteristic MRI finding in FA was upper cervical cord shrinkage and only minor atrophy of the cerebellum. The demonstration of cerebellar atrophy in the majority of EOCA patients supports the view that EOCA is distinct from FA. It is uncertain, however, whether EOCA is a homogenous disease entity or a group of phenotypically similar syndromes.

Action Potentials↗
PubMed1991

Metabolic and destructive brain disorders in children: findings with localized proton MR spectroscopy.

The diagnostic potential of volume-selective proton magnetic resonance (MR) spectroscopy in vivo was evaluated in 20 children and young adults with various neurodegenerative brain disorders. All patients were examined with MR spectroscopy in conjunction with MR imaging of the brain on a whole-body imager at 1.5 T. Comparison of spectra in our patients with those of children with normal myelination (prominent signals from N-acetylaspartate [NAA], creatine/phosphocreatine, and choline) revealed a marked decrease of NAA in 12 of 17 patients with focal or generalized demyelination. In patients with Canavan disease, NAA signal intensity was markedly increased, but no choline signal was found. Increased signal intensity from lactate occurred in patients with Leigh disease, neuroaxonal dystrophy, Schilder disease, and Cockayne disease, which indicated a disturbed energy metabolism in the examined region. These results demonstrate that proton MR spectroscopy can be applied in a clinical environment to facilitate diagnosis of hereditary and acquired brain disorders in children.

Brain↗
PubMed1991

Myelinoclastic diffuse sclerosis (Schilder's disease): cliniconeuroradiologic correlations.

We report a 17-year-old boy with myelinoclastic diffuse sclerosis (Schilder's disease) presenting with left leg paresis, visual loss, and behavioral changes. CT and MRI showed two large lesions in the subcortical white matter of the occipital and parietal lobes of both hemispheres and increased intracranial pressure. Histology disclosed large areas of demyelination and perivascular infiltrates. The patient improved with coincident oral prednisolone treatment.

Adolescent↗