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Biomedical subjects

J Valk

Publications and source records attributed to J Valk.

At least 19 recordsLinked to original sources
PubMed1992

[Progressive multifocal leukoencephalopathy in AIDS].

This study was carried out to determine clinical features, abnormalities on CT scan and MRI, and course in patients with HIV-I-related progressive multifocal leukoencephalopathy (PML). There were 14 patients with a presumptive diagnosis of PML among 500 HIV-I infected patients with neurological complaints, examined between September 1982 and May 1991 in the University Medical Centre in Amsterdam by a neurologist. In these 14 patients clinical features, imaging abnormalities and course of the disease were analysed retrospectively. All patients presented with progressive focal neurological abnormalities. Cerebrospinal fluid analysis revealed aspecific abnormalities in 5/13 patients. CT scanning of the brain showed hypodense areas in the white matter, without mass effect and with contrast enhancing in only one patient. MR Imaging of the brain showed high signal intensity areas in white matter and in gray matter (10/13), without mass effect, and with contrast enhancement in two. Specimens for neuropathological examination were obtained from 7 patients; in all these cases the diagnosis of PML was confirmed. In patients with AIDS a presumptive diagnosis of PML can be based on clinical features, brain imaging abnormalities and course. However neuropathological confirmation remains the gold standard. Usually the course in these patients was steadily progressive. Most patients died within one year.

Acquired Immunodeficiency Syndrome↗
PubMed1992

1H and 31P magnetic resonance spectroscopy of the brain in degenerative cerebral disorders.

Proton and phosphorus magnetic resonance spectroscopy of the brain was performed in 35 patients with degenerative cerebral disorders: 24 patients had demyelinating (white matter) disorders and 11 patients had neuronal (gray matter) disorders. Four grades of demyelination and three grades of cerebral atrophy were distinguished by magnetic resonance imaging criteria. The spectroscopic data were compared with normal values previously obtained. With increasing degrees of demyelination, lower ratios of phosphodiesters to beta-ATP were found. This trend was statistically significant. Decreased phosphodiester-beta-ATP ratios occurred simultaneously with imaging abnormalities. The decrease in phosphodiester-beta-ATP ratio in demyelinated areas is attributed to white matter rarefaction. Increasing cerebral atrophy was accompanied by lower ratios of N-acetyl aspartate to creatine. This trend was statistically significant. The decrease in the N-acetyl aspartate-creatine ratio was demonstrated before the magnetic resonance images showed signs of cerebral atrophy in patients with neuronal disorders. As N-acetyl aspartate is located exclusively in neurons and their branches, a decrease of the N-acetyl aspartate-creatine ratio can be attributed to neuronal and axonal damage and loss.

Adult↗
PubMed1992

L-2-hydroxyglutaric acidemia: a novel inherited neurometabolic disease.

Routine screening for organic acids revealed increased and isolated urinary excretion of L-2-hydroxyglutaric acid in 8 mentally retarded patients from five unrelated families, including three pairs of siblings. L-2-Hydroxyglutaric acid concentration was also found to be increased in the cerebrospinal fluid (CSF) and to a lesser extent in plasma. The only other biochemical abnormality was an increased concentration of lysine, both in plasma and in CSF. No organic acid abnormality was found on screening of asymptomatic family members. Patients were of either sex, and became symptomatic during childhood, with moderate to severe mental deficiency in all and definite cerebellar dysfunction in 7. Magnetic resonance imaging revealed an identical abnormal pattern with subcortical leukoencephalopathy, cerebellar atrophy, and signal changes in the putamina and dentate nuclei, in all patients. No specific biochemical function or catabolic pathway involving L-2-hydroxyglutaric acid is known in mammals, including humans. Preliminary loading and dietary studies failed to reveal the origin of the compound. The elevated CSF/plasma ratio suggests that it is in part generated within the central nervous system. This report describes a novel inherited neurometabolic disease, probably autosomal recessive, with distinct clinical, biochemical, and neuroimaging features.

Adolescent↗
PubMed1992

Analysis of phospholipids in brain tissue by 31P NMR at different compositions of the solvent system chloroform-methanol-water.

Brain phospholipids can be quantitated by high-resolution 31P NMR of crude brain tissue extracts in the solvent system chloroform-methanol-water (+EDTA) which was introduced recently (P. Meneses and T. Glonek, J. Lipid Res. 29, 679 (1988)). Phospholipid resonance positions depend on the type of tissue extract and on solvent composition. The effects of systematic variation of the solvent system on phospholipid NMR profiles are presented. Resolution can be optimized by adjustment of the solvent composition. Virtually all phospholipid classes can be resolved, and the major phospholipids in brain: sphingomyelin and phosphatidyl-choline, -serine, -inositol, -ethanolamine, and -ethanolamine plasmalogen can be quantitated easily. Additional resonances have been assigned to phosphatidylcholine plasmalogen, alkylacyl-phosphatidylcholine and phosphatidylinositolbisphosphate. NMR offers a rapid method for quantitative analysis of the phospholipid composition in brain tissue which requires minimum sample handling.

Aged↗
PubMed1992

MR imaging of skeletal metastases from medulloblastoma.

The findings of MR imaging in 3 patients with bone metastases from medulloblastoma are reported. The first patient showed focal lesions of low signal intensity on T1-weighted spin echo images at a time when bone scintigraphy was negative for metastases. This patient later developed extensive osteosclerotic lesions visible on plain films. The bone marrow of the second patient showed diffuse low signal intensity on T1-weighted images. After chemotherapy the signal intensity of the bone marrow increased which correlated with a return of normal hematopoietic tissue. A response to chemotherapy was also found on MR imaging and repeat bone marrow biopsies in a third patient. A consistent finding was a low signal intensity on pre-gadolinium images, but the pattern (focal or diffuse abnormal signal intensity) was different in each patient. To our knowledge, this is the first report on MR imaging findings in bone metastases from medulloblastoma.

Acetabulum↗
PubMed1992

White matter lesions on magnetic resonance imaging in clinically diagnosed Alzheimer's disease. Evidence for heterogeneity.

In a prospective magnetic resonance imaging (MRI) study we evaluated the prevalence and severity of white matter changes in 29 patients with Alzheimer's Disease (AD) and 24 age-matched healthy elderly, all without cerebrovascular risk factors. The AD patients were divided into two groups according to age at onset of symptoms, one with presenile onset AD (n = 13) and one with senile onset AD (n = 16), who were matched for dementia severity. Signal hyperintensities were rated using a semiquantitative scoring method, separately in the periventricular region (PVH) and in the lobar white matter (WMH), as well as in the basal ganglia (BGH) and in the infratentorial region (ITFH). Cortical atrophy as a parameter of grey matter involvement was rated on a 0 (absent) to 3 (severe) scale. We found PVH, WMH and BGH scores to be significantly higher in senile onset AD patients than in age-matched controls. By means of multiple linear logistic regression we found that PVH, WMH and BGH scores were significantly dependent on the diagnosis of senile onset AD, while the PVH score also showed a significant age dependency. Cortical atrophy did not differ significantly between presenile onset AD and senile onset AD patients. These results indicate that presenile onset AD and senile onset AD patients differ with respect to white matter involvement, but not with respect to grey matter involvement on MRI. Since cerebrovascular risk factors were excluded these findings may indicate that senile onset AD patients display more small vessel involvement (arteriolosclerosis) than presenile onset AD patients, suggesting additional (microvascular) factors for the dementia syndrome in senile onset AD. Our data lend support to the growing body of evidence that AD is heterogeneous, consisting of at least two types. Based on our findings two forms can be distinguished: (i) a 'pure' form of the disease, usually with early disease onset, and no more white matter changes than normal for age; (ii) a 'mixed' form, usually with disease onset later in life, and showing more white matter changes on MRI than normal for age.

Aged↗
PubMed1992

Atrophy of medial temporal lobes on MRI in "probable" Alzheimer's disease and normal ageing: diagnostic value and neuropsychological correlates.

Magnetic resonance imaging (MRI) has shown a great reduction in medial temporal lobe and hippocampal volume of patients with Alzheimer's disease as compared to controls. Quantitative volumetric measurements are not yet available for routine clinical use. We investigated whether visual assessment of medial temporal lobe atrophy (MTA) on plain MRI films could distinguish patients with Alzheimer's disease (n = 21) from age matched controls (n = 21). The degree of MTA was ascertained with a ranking procedure and validated by linear measurements of the medial temporal lobe including the hippocampal formation and surrounding spaces occupied by cerebrospinal fluid. Patients with Alzheimer's disease showed a significantly higher degree of subjectively assessed MTA than controls (p = 0.0005). Linear measurements correlated highly with subjective assessment of MTA and also showed significant differences between groups. Ventricular indices did not differ significantly between groups. In Alzheimer's disease patients the degree of MTA correlated significantly with scores on the mini-mental state examination and memory tests, but poorly with mental speed tests. This study shows that MTA may be assessed quickly and easily with plain MRI films. MTA shown on MRI strongly supports the clinical diagnosis of Alzheimer's disease, is related to memory function, and seems to occur earlier in the disease process than does generalised brain atrophy.

Aged↗
PubMed1992

Global left ventricular perfusion: noninvasive measurement with cine MR imaging and phase velocity mapping of coronary venous outflow.

Velocity and volumetric flow of left ventricular venous outflow in the distal coronary sinus were measured with magnetic resonance (MR) velocity mapping techniques in 24 healthy men. A total of 16-21 velocity maps were acquired throughout the cardiac cycle. To determine the accuracy of the MR velocity-mapping pulse sequence, measurements were obtained with a flow phantom. Mean blood flow was 144 mL/min +/- 62 (standard deviation); mean velocity, 2.1 cm/sec +/- 1.0; and mean cross-sectional area, 1.2 cm2. Phasic measurements revealed a biphasic flow pattern in the coronary sinus, with a first peak in systole (257 mL/min +/- 174) and a second peak in early diastole (1,090 mL/min +/- 487). The cross-sectional area varied between 0.5 cm2 +/- 0.2 at end diastole and 1.9 cm2 +/- 0.6 in systole, a finding that suggests a capacitance function for venous outflow. Mean blood flow measurements were in agreement with measurements obtained invasively in previous studies. It is concluded that MR velocity mapping can enable noninvasive measurement of coronary venous outflow and global left ventricular perfusion and may become clinically useful in assessment of coronary blood flow reserve.

Adult↗
PubMed1992

A comparison of jaw muscle cross-sections of long-face and normal adults.

Long-face subjects have smaller maximum molar bite forces than do normal individuals. This has been attributed both to differences in moment arms and size of the jaw muscles. In this study, a comparison was made between the mid-belly cross-sectional areas of the jaw muscles of 13 long-face and 35 normal adults by means of serial MRI scans. The subjects were selected on the basis of anterior lower face height as a percentage of anterior total face height. These and other cephalometric variables were measured from lateral radiographs. In the long-face group, the cross-sectional areas of the masseter, medial pterygoid, and anterior temporal muscles were, respectively, 30%, 22%, and 15% smaller than in the control group. By a discriminant analysis and a multivariate analysis of variance, these differences were found to be significant (p less than 0.001). The findings of this study hint that differences in the sizes of the jaw muscles of long-face and normal subjects might explain, in part, the observed differences in maximum molar bite force.

Adult↗
PubMed1992

A correlative triad of gadolinium-DTPA MRI, EDSS, and CSF-MBP in relapsing multiple sclerosis patients treated with high-dose intravenous methylprednisolone.

In a prospective study, we compared the number of gadolinium-DTPA (Gd-DTPA) enhancing lesions on MRI with the CSF and clinical findings before and after a total of 20 courses of high-dose intravenous methylprednisolone in relapsing multiple sclerosis patients. Before treatment, there was a significant correlation of Gd-DTPA enhancement (seen on 16 of 20 scans) and CSF myelin basic protein (MBP). If enhancement with Gd-DTPA represents inflammation and CSF-MBP indicates myelin breakdown, the amount of inflamed tissue should correlate with the amount of myelin being damaged. Clinical improvement occurred following 15 of 20 courses, and decrease of Gd-DTPA enhancement in 12 of 16 scans; the mean CSF-MBP level was the only CSF variable to return to reference values. There was a significant correlative triad of decrease in CSF-MBP, Gd-DTPA enhancement, and clinical disability. Thus, the clinical effect of methylprednisolone might be accompanied by a reduction of inflammation and myelin breakdown.

Adult↗
PubMed1992

Do metastases in vertebrae begin in the body or the pedicles? Imaging study in 45 patients.

We analyzed CT scans of the spine obtained in patients with vertebral metastases to determine what specific portion of the vertebra is initially involved by metastasis. The CT findings were then correlated with the abnormalities seen on plain films. Forty-five patients with histologically proved metastases in 95 vertebrae were included in the study. In all patients, CT scans and plain films of the spine were obtained within 1 week of each other. Analysis of the CT scans showed that the vertebral body was the portion of the vertebra that was most frequently destroyed by the metastases. Destruction of a pedicle was never identified in the absence of involvement of the body. The opposite was true on plain films, in which the most common finding was destruction of the pedicles. CT showed that the position of the metastases in the vertebra correlated with the sites of entry of the vertebral vessels. Our results show that the initial anatomic location of metastases within vertebrae is in the posterior portion of the body. Analysis of CT scans shows that the body is involved before the pedicles, although destruction of the pedicles is the most common finding on plain films. The pedicles are not the primary site of metastatic involvement. Destruction of the pedicles occurs only in combination with involvement of the vertebral body.

Adult↗
PubMed1992

Relapsing-remitting multiple sclerosis: sequential enhanced MR imaging vs clinical findings in determining disease activity.

OBJECTIVE: Sequential MR imaging frequently shows disease activity (clinically silent new brain lesions) in subgroups of patients with multiple sclerosis and therefore is valuable in monitoring the effects of treatment. Monitoring of disease activity in patients being treated for relapsing-remitting multiple sclerosis will increase in importance as new and safe therapies are developed. We studied sequential enhanced MR images of patients with early relapsing-remitting multiple sclerosis to define the MR features that indicate disease activity in this subgroup of patients and to compare MR imaging and clinical findings for this purpose. SUBJECTS AND METHODS: Seven patients with relapsing-remitting definite multiple sclerosis were examined monthly for 4-12 months. For each image, a standard repositioning protocol consisting of three images was used to ensure reproducibility of axial (double oblique) image planes, planned according to internal landmarks. A total of 58 unenhanced T2-weighted and enhanced T1-weighted MR images were obtained. RESULTS: MR images showed new enhancing lesions in six of the seven patients. On 25 (43%) of the 58 enhanced T1-weighted MR images, a total of 50 new enhancing lesions were observed, and on one image a reenhancing lesion was seen. The unenhanced T2-weighted images showed corresponding abnormalities for 92% of the new enhancing lesions. At follow-up, most lesions (86%) were enhanced on only one occasion: 4% were enhanced on more than two consecutive monthly MR examinations. Forty-nine percent of the lesions seen on T2-weighted images "disappeared" (beyond the resolution of the imaging system) after a mean follow-up of 3.5 months, especially lesions that were initially smaller than 5 mm. During the study, only five clinical relapses occurred in three patients (all at times when MR images showed contrast-enhancing lesions), and fixed disability did not increase. On 21 additional occasions, MR images showed new enhancing or reenhancing lesions in patients who were clinically stable at the time (4.2 times more clinically silent disease activity). CONCLUSION: Our results suggest that contrast-enhanced MR imaging is more sensitive than clinical monitoring for detecting new disease activity in patients with relapsing-remitting multiple sclerosis and that MR imaging might be useful in the evaluation of therapeutic regimens.

Adult↗
PubMed1991

Magnetic resonance imaging vs palpation of cervical lymph node metastasis.

In a series of 100 patients with head and neck carcinoma, the preoperative histopathologic findings of palpation and magnetic resonance imaging were compared with regard to both laterality and lymph node level (I through V). The overall error for palpation in detecting affected sides was 32%. Gadolinium-enhanced magnetic resonance images reliably upgraded 60% of the clinically negative necks, the overall error of magnetic resonance imaging being 16%. However, for both modalities, the sensitivity per level was too low to allow for selective neck dissections in case of only one positive level. These findings show that apart from primary tumor grading, magnetic resonance imaging can improve the preoperative grading of cervical lymph nodes. In selected cases, this may change the treatment plan to a "wait-and-see" policy or a more conservative type of neck dissection.

Aged↗
PubMed1991

Malformations of the spinal cord in 53 patients with spina bifida studied by magnetic resonance imaging.

The incidence of associated malformations of the hindbrain and spinal cord in patients with spina bifida was investigated by a clinical and magnetic resonance study. The incidence of these malformations in combination with spina bifida was 49/53 (92.5%). Fifty-tree children born with spina bifida aperta (40 patients) or spina bifida occulta (13 patients) formed the study group. The incidence of the various malformations were: Chiari malformations, type I, 10/53 (19%), and type II, 20/53 (38%); syringomyelia, 13/53 (24.5%); hydromyelia 4/53 (7.5%); tethered cord malformation, 35/53 (66%); diastematomyelia 2/53 (4%). Thirty-seven of the 49 patients with associated malformations had no clinical signs at the time of our study. The results point to the fact that in the pediatric age group, associated spinal defects often remain asymptomatic.

Abnormalities, Multiple↗
PubMed1991

Pattern recognition in magnetic resonance imaging of white matter disorders in children and young adults.

Magnetic resonance imaging (MRI) is considered to be a highly sensitive modality for visualizing white matter abnormalities. Estimations of its specificity are far less positive. However, diagnostic specificity depends upon both the inherent qualities of MRI and on the quality of image interpretation. Systematic and detailed analysis of many image elements, and substantial prior experience improve the quality of image interpretation and thus improve diagnostic specificity. The present study has been set up to develop a pattern recognition system which combines sensitivity and specificity, systematic analysis of image elements and prior experience. This pattern recognition is based on the data of 277 patients with white matter disorders referred for MRI. The information was stored in a data base and computer analyzed. Twenty-two MRI patterns were discerned in as many disease categories. The frequency of occurrence of each MRI abnormality was assessed per disease category to establish the pattern of abnormalities characteristic for each separate disease category. The pattern recognition program was also written so that: (a) when fed data about MRI abnormalities observed in a new case, the computer produces a differential diagnosis with probabilities and 95% confidence intervals for each differential diagnosis; (b) specific data on the MRI findings of new cases could be added to the data base to improve the experience and accuracy of the program. This program for pattern recognition of abnormalities in the MR images of white matter disorders enhances the specificity of image interpretation and provides a wonderful aid for teaching purposes.

Adolescent↗
PubMed1991

Neuroimaging in lissencephaly type I.

The CT scan's of 22 patients with lissencephaly type I, a severe developmental disorder of the cerebral cortex, were studied. In 6 patients a magnetic resonance (MR), scan was also performed. The CT and MR scans of the lissencephaly patients were compared to a control group consisting of 49 patients with a normal CT or MR scan. In lissencephaly the cortical thickness was always larger than 10 mm, as compared to less than 7 mm in the normal situation. In lissencephaly the WSF/DSF index (with/depth of the sylvian fissure) was always larger than 0.29, while in the normal situation less than 0.25.

Adolescent↗
PubMed1991

The MR spectrum of peroxisomal disorders.

In the last decade an increasing number of peroxisomal disorders has been recognized. Almost all peroxisomal disorders affect the central nervous system. Many of them lead to demyelination, some of them lead to migrational disturbances. The MR pattern of X-linked adrenoleukodystrophy is well known, but the pattern of the other peroxisomal disorders is less well known. We evaluated the gray and white matter abnormalities of 20 patients on 32 occasions. We compared the results with histological data and in this way came to the description of a number of characteristic MR patterns occurring in peroxisomal disorders: (1) Neuronal migrational disturbances in combination with hypomyelination, dysmyelination or demyelination. (2) Symmetrical demyelination of posterior limb of the internal capsule, cerebellar white matter and brain stem tracts with a variable affection of cerebral hemispheres. (3) Symmetrical demyelination, exhibiting two zones, starting in the occipital area and spreading outwards and forwards; affection of brain stem tracts. (4) Less characteristic patterns of demyelination. The patterns are illustrated and differentiation from other disorders is discussed.

Adolescent↗