Biomedical subjects

J Valk

Publications and source records attributed to J Valk.

At least 37 records · Page 2Linked to original sources

PubMed1998

Cine phase-contrast MR imaging in normal pressure hydrocephalus patients: relation to surgical outcome.

Phase-contrast cine MR flow imaging through the aqueduct was used to establish the diagnosis of normal pressure hydrocephalus (NPH), and to predict outcome after shunting. From 1990-1994 16 patients, who were participants in the Dutch Normal Pressure Hydrocephalus Study [3], were studied. The patients included in this study met clinical and CT-scan criteria as described in this study, underwent cine phase-contrast MR imaging prior to placement of a CSF shunt, and had a follow-up 12 months after the operation. Claustrophobic patients, patients with a pacemaker or extremely agitated patients were excluded. Normal Flux was calculated in each patients, as the average difference in caudal and rostral flux (Fdiff) +2 times standard deviation (0.97 cc/sec) [2]. The clinical outcome was measured with a modified scale of activities of daily living (ADL) as described by Rankin. Of the 16 patients, 8 could not be evaluated due to restlessness during MR measurements, disabling cerebral vascular accidents or death before the end of the follow-up period. Of the remaining 8 patients, 5 had a normal flux, of which only one improved. Two patients had a Fdiff twice the normal range, which improved in both patients. One patient had no measurable flux, consistent with an aqueduct stenosis; he too improved. Overall, there was a concordance of MR findings with final outcome after shunting in 7 out of 8 patients. This pilot study, therefore, support the need to further evaluate flow with MR imaging techniques to select patients with shunt responsive NPH.

Cerebrospinal Fluid Shunts↗

PubMed1998

MR imaging of anorectal malformations and associated anomalies.

Congenital anorectal malformations are found in many forms, and are frequently associated with other anomalies, especially of the spinal cord, spine, and urogenital system. Decisions concerning initial management of children with anorectal malformations can be made only after accurate determination of (a) the level and type of malformation, (b) the type of fistula, (c) the developmental state of the sphincter muscle complex, and (d) the presence of associated anomalies. Magnetic resonance imaging has proven to be the only modality to answer all these crucial questions, and has contributed to a better insight in the morphology and pathogenesis of such complex congenital malformations.

Abnormalities, Multiple↗

PubMed1998

Functional correlates of callosal atrophy in relapsing-remitting multiple sclerosis patients. A preliminary MRI study.

In multiple sclerosis (MS), periventricular lesions produce atrophy of the corpus callosum (CC), as evidenced by magnetic resonance imaging (MRI). We investigated whether CC atrophy in relapsing-remitting MS patients is related to functional deficits. We compared 14 mildly disabled (mean Expanded Disability Status Scale score 2.7) relapsing-remitting MS patients with 14 age- und sex-matched controls. CC size was determined using sagittal T1-weighted MRI. The function of the CC was studied using a neuropsychological battery and neurophysiological evaluation based on visual stimulation using a divided visual field paradigm. The total area of the CC in patients (mean 5.3 cm2) was significantly (P = 0.002) smaller than in controls (mean 6.6 cm2). Patients showed left ear extinction using the dichotic listening test and impaired name learning, which was correlated with atrophy of the splenium. There were no differences in interhemispheric transfer time between patients and controls. Marked atrophy of the CC can be encountered in relapsing-remitting MS patients. The associated cerebral disconnection correlated with atrophy of expected regions of the CC, thus supporting topographical organization.

Adult↗

PubMed1998

Symptoms and signs related to the trigeminal nerve: diagnostic yield of MR imaging.

PURPOSE: To assess the diagnostic yield of magnetic resonance (MR) imaging in patients with symptoms and signs related to the trigeminal nerve. MATERIALS AND METHODS: Medical records and MR imaging studies in 112 consecutive patients referred for MR imaging over 5 years were evaluated. MR images were independently reviewed by two neuroradiologists unaware of the clinical findings. Signs and symptoms at presentation were associated with either a positive or negative MR imaging outcome. Logistic regression analysis was performed to identify clinical variables related to imaging results. RESULTS: Sixty-eight (61%) patients had positive MR imaging findings related to symptoms and signs. Trigeminal neuralgia was correlated with a negative MR imaging outcome (P < .001). Numbness (P < .01), impaired sensation (P < .001), other neurologic symptoms and signs (P < .01), progression of symptoms and signs (P < .001), and duration of symptoms of less than 1 year (P < .001) corresponded to a positive MR imaging outcome. Two regression models, each with three clinical parameters (progression, duration < 1 year, and trigeminal neuralgia or impaired sensation), had comparable accuracy for prediction of the MR imaging outcome. CONCLUSION: Clinical findings can be used to identify groups in which a high or a low yield of MR imaging is correlated with symptoms and signs related to the trigeminal nerve.

Cranial Nerve Diseases↗

PubMed1998

Patterns of brain magnetic resonance abnormalities on T2-weighted spin echo images in clinical subgroups of multiple sclerosis: a large cross-sectional study.

To substantiate differences in magnetic resonance (MR) patterns in clinical subgroups of multiple sclerosis (MS), we analyzed T2-weighted MR images of a large regional population of MS patients (n = 188). The patients had already been classified according to recent consensus definitions regarding the clinical course of MS into relapsing-remitting (RR), secondary progressive (SP) or primary progressive (PP). Significant (p < 0.01; Spearman test) differences were present between RR and SP patients regarding total lesion load, size and location of lesions. RR and PP patients showed similar MR patterns. PP and SP patients differed in total lesion load, small and medium-sized lesions. The degree of atrophy was highest for SP patients. The clinical progression rate [Expanded Disability Status Scale (EDSS)/disease duration] was similar for various subgroups; the MR progression rate (total lesion score/disease duration) was significantly larger for SP than for PP patients. The lesions load disability quotient (total lesion load/EDSS) differed between RR and PP patients and also between SP and PP patients. In SP patients, the total lesion load correlated significantly (Spearman rank correlation coefficient of 0.52) with EDSS. We conclude that PP patients differ in MR abnormalities from SP patients, that PP and RR patients have similar MR abnormalities and that RR and SP patients are at a different end of the same spectrum of the disease. As the dynamics and clinical impact of MS lesions are different in the various clinical subgroups, they should be considered separately in clinical trials.

Adult↗

PubMed1998

Histopathologic correlate of hypointense lesions on T1-weighted spin-echo MRI in multiple sclerosis.

Postmortem unfixed whole brains from five multiple sclerosis (MS) patients were examined by MRI using a T2- and T1-weighted spin-echo (SE) sequence and histology to investigate the histopathologic characteristics of hypointense lesions on T1-weighted SE MR images. The degree of hypointensity was scored semiquantitatively by two blinded observers in reference to normal-appearing white matter. Signal intensities of the lesions and the normal-appearing white matter were measured to obtain contrast ratios. Hematoxylin-eosin stain was used to assess degree of matrix destruction (decrease of density of the neuropil) and cellularity of a lesion, Klüver-Barrera stain for degree of demyelination, Bodian stain for axonal density, and immunostaining of glial fibrillary acid protein for reactive astrocytes and fibrillary gliosis. Nineteen lesions were selected for analysis. Nearly all lesions were compatible with the chronic MS plaque: hypocellularity, absence of myelinated axons, in the presence of reactive astrocytes. Contrast ratios of the lesions were highly correlated (R = -0.90; p < 0.01), with degree of hypointensity scored semiquantitatively. Degree of hypointensity on T1-weighted SE images did not correlate with degree of demyelination or number of reactive astrocytes, but was associated with axonal density (R = -0.71; p = 0.001). A trend was found with degree of matrix destruction (R = 0.45; p = 0.052). We conclude that, in our limited sample, hypointense lesions seen on T1-weighted SE MR images are associated histopathologically with severe tissue destruction, including axonal loss. Our results need to be substantiated in a larger study on more varied patient material to evaluate the use of hypointense lesions as a surrogate marker of persistent deficit in MS patients.

Adult↗

PubMed1998

Visual activation patterns in patients with optic neuritis: an fMRI pilot study.

We studied the use of functional MRI (fMRI) with visual stimulation in nine patients with unilateral optic neuritis. Eight healthy subjects served as controls. Patients showed reduced activation upon stimulation of the affected eye, on average 33% (range 0 to 156%) of the average monocular activation in the control group. Decreased activation was also seen for the unaffected eye (61% of control values, range 3 to 133%). We conclude that fMRI with visual stimulation is feasible in patients with optic neuritis and deserves future study.

Adult↗

PubMed1998

Phenotypic variation in leukoencephalopathy with vanishing white matter.

OBJECTIVE: The objective of this study is to describe milder and later onset variants of a recently described leukoencephalopathy with vanishing white matter. BACKGROUND: The diagnostic criteria used currently for this disease include an early-childhood onset of neurologic deterioration. METHODS: Clinical, MRI, and spectroscopic findings of five patients were reviewed who fulfilled all inclusion criteria for the disease of vanishing white matter, apart from the age at onset. In one patient histopathologic findings were documented. RESULTS: Onset of the disease was in late childhood or adolescence in four patients, and one patient was still presymptomatic in his early twenties. The course of the disease tended to be milder than in the patients with early-childhood onset. MRI revealed a diffuse cerebral hemispheric leukoencephalopathy with evidence of white matter rarefaction. MRS of the abnormal white matter showed a serious decrease but not complete disappearance of all "normal" signals and, in some patients, the presence of extra signals from lactate and glucose. Changes in relative spectral peak heights were compatible with axonal damage or loss, but not with active demyelination or substantial gliosis. Autopsy in one patient confirmed the extensive rarefaction of the cerebral white matter. There was a commensurate loss of axons and myelin sheaths. Within the brainstem, pontine lesions were present, also involving the central tegmental tracts--a phenomenon previously described in early-onset patients. CONCLUSION: Later onset does occur in the disease of vanishing white matter, and both MRS and histopathology are compatible with a primary axonopathy rather than primary demyelination.

Adolescent↗

PubMed1998

MR imaging and proton spectroscopy in 3-hydroxy-3-methylglutaryl coenzyme A lyase deficiency.

Three patients with 3-hydroxy-3-methylglutaryl coenzyme A lyase deficiency were examined with MR imaging and proton MR spectroscopy. In two patients, both clinically normal, MR images showed a diffuse mild abnormality in signal intensity of the cerebral white matter, with multiple foci of more pronounced signal abnormality superimposed. In the third patient, who was clinically retarded and had a cerebral visual impairment, MR imaging showed, in addition to a diffuse signal abnormality of the cerebral white matter, atrophic scarring of the occipital lobes and abnormal signal intensity of the thalami and basal ganglia. It is highly probable that the additional lesions in the occipital lobes and basal nuclei were related to the episode of severe neonatal hypoglycemia the patient experienced. The MR spectroscopic abnormalities correlated with the degree of disease as evidenced by MR imaging.

Amino Acid Metabolism, Inborn Errors↗

PubMed1997

Magnetic resonance imaging in classification of congenital muscular dystrophies with brain abnormalities.

A survey was performed of magnetic resonance imaging (MRI) findings in 21 patients with congenital muscular dystrophy (CMD) with cerebral abnormalities to evaluate the contribution of MRI to the classification of CMD patients. In 5 patients with Walker-Warburg syndrome (WWS), MRI showed hydrocephalus due to aqueduct stenosis, generalized cerebral cortical agyric or pachygyric polymicrogyria, diffuse cerebral hemispheric white matter abnormalities, and malformations of posterior fossa structures. In 4 patients with muscle-eye-brain disease, MRI showed cortical dysplasia, but less severe than in WWS. The cerebral white matter either was normal or contained multiple focal abnormalities. Malformations of posterior fossa structures were present. Eight patients, classified as having classic merosin-deficient CMD (MD-CMD), had diffuse cerebral hemispheric white matter abnormalities, no other abnormalities. One patient with MD-CMD had only a few, focal white matter abnormalities. Three CMD patients had occipital agyria, otherwise normal gyration, multifocal or more diffuse cerebral white matter changes, and variable hypoplasia of pons and vermis. Two of the 3 patients had negative muscle merosin staining. The conclusion of the study is that MRI is an important adjunct in the classification of CMD patients. CMD with occipital agyria can be regarded as a newly recognized, separate CMD subtype.

Adolescent↗

PubMed1997

MR imaging in retinoblastoma.

We studied the appearance of retinoblastoma on unenhanced and gadolinium-enhanced images and the accuracy of tumour staging with MR imaging. The MR images were obtained in 18 children with retinoblastoma and compared with histopathological findings after enucleation. The MR imaging included T1-weighted and dual-echo T2-weighted images before, and T1-weighted images after, gadopentetate dimeglumine injection. The contrast between tumour and ipsilateral vitreous strongly increased (57 %) after gadolinium on T1-weighted images (p = 0.004). Tumour was strongly hypointense as compared with ipsilateral vitreous in all patients using heavily T2-weighted (TE = 120 ms) images (p = 0.001). The estimated T2 of tumour (mean 96 + 14 ms) did not correlate with histological grading or degree of calcification. Unenhanced T1-weighted MR images rightfully excluded extrascleral growth in 16 of 16 cases, but its presence was confirmed after enucleation in only one of 2 abnormal MR scans. Invasion of the optic nerve behind the cribriform plate was confirmed in 2 of 3 abnormal gadolinium-enhanced MR scans, but also in 1 of the 15 cases in which MR images were normal. The T2-weighted images were useful in assessing retinal detachment. We conclude that heavily T2-weighted images, unenhanced T1-weighted images and gadolinium-enhanced T1-weighted MR images are complementary in characterizing and staging retinoblastoma.

Contrast Media↗

PubMed1997

Bilateral white matter lesions following severe meningococcal meningoencephalitis.

Occasionally, striking abnormalities are found on MRI in patients with mild neurological disturbances. In most of these cases the diagnosis is not immediately evident and the history does not provide an unequivocal explantation. We present a patient with extensive symmetrical white matter abnormalities in the posterior temporal, temporo-occipital and parietal regions, 24 years after documented severe meningococcal meningoencephalitis. A meningitic vasculitis, affecting the insular branches of the middle cerebral arteries, could have been responsible for these changes.

Brain↗

PubMed1997

Quantitative computer-assisted analysis vs. visual estimation of MR imaging response of brain metastases to radiotherapy.

Using both quantitative computer-assisted analysis and visual estimation the MR imaging response of brain metastases to whole-brain radiotherapy (WBRT) was prospectively studied in 49 patients. Compared to the computer-assisted analysis, the precision of the visual estimation (by two readers in conference) of tumor response was determined. Also the radiological response was related to the clinical response. Six weeks after WBRT follow-up MR was performed in 27 of 49 patients. Of the remaining 22 patients without follow-up MR, 9 had died or deteriorated due to neurologic decline. In four patients (15%) tumor increase was demonstrated by computer-assisted analysis; in the other 23 patients tumor remained stable (15%) or decreased (70%). In 11 of the 27 patients, a second follow-up MR was obtained 26 wk after WBRT demonstrating tumor increase in seven patients (64%). Complete discordance between both assessment methods was noticed in only 4 of 38 MR scans (27 scans 6 wk after WBRT and 11 scans 26 wk after WBRT) with small quantitative changes in tumor volume. In 26 of 38 (68%) observations 6 and 26 wk after WBRT, there was a positive correlation between change in tumor volume and change in the Neurologic Status. Visual estimation analysis seems an appropriate method of routine therapy monitoring in individual patients with brain metastases. The computer-assisted analysis should be considered if precise response monitoring becomes critical.

Adult↗

PubMed1997

Comparison of four potential MR parameters for severe tissue destruction in multiple sclerosis lesions.

The purpose of this study was, first, to evaluate correlations between four potential magnetic resonance (MR) parameters for severe tissue destruction in multiple sclerosis (MS) lesions. Second, to evaluate the effect of incidental magnetization transfer (MT) effect on hypointense lesions in multislice T1 spin echo (SE) imaging. In 49 lesions, from 10 MS patients, MT ratio (MTR), T1 relaxation time, signal intensity (SI) on T1-weighted SE images normalized to normal-appearing white matter (NAWM), and SI normalized to cerebrospinal fluid (CSF) were measured. Differences in contrast of hypointense lesions were measured between single slice and multislice imaging. MTR correlated significantly (p < .001) with longitudinal relaxation rates (1/T1) (r = 0.84), SI normalized to NAWM (r = 0.78), and SI normalized to CSF (r = 0.75). The degree of reduction in contrast, caused by multislice imaging, correlated significantly with MTR of lesions (r = 0.60, p < .001), leading to reduction of hypointense lesion load (p < .01). We conclude that all four MR markers for severe tissue destruction are highly correlated when applied to selected hypointense lesions on T1-weighted SE images. Due to "incidental" off-resonance excitation, contrast and hypointense lesion load will be reduced in multislice T1-weighted SE images.

Adult↗

PubMed1997

MRI assessment of myelination of motor and sensory pathways in the brain of preterm and term-born infants.

A study was performed in 48 neurologically normal preterm and term-born infants, with a postconceptional age at MRI varying between 30 2/7 and 46 weeks and a mean age of 34 2/7 weeks. The purpose of the study was to determine the normal progress of myelination on MRI in that age range. T1- and T2-weighted images of the brain were assessed for changes in signal intensity of white matter relative to gray matter. Multiple sites in the brainstem, cerebellum and cerebral hemispheres were assessed separately. The findings were correlated with the ages of the infants. As judged from relative signal intensities, myelin was present at the post-conceptional age of 30-34 weeks in the following structures: tegmentum pontis (in particular medial lemniscus), superior and inferior colliculi, decussation of the superior cerebellar peduncles, crura cerebri, ventrolateral thalamus, lateral globus pallidus, dorsolateral putamen, dentate nucleus, middle and superior cerebellar peduncles, vermis cerebelli, cortex bordering the central sulcus and hippocampus. Little progress in myelination was noticed up to the post-conceptional age of 46 weeks. Between 34 and 46 weeks, myelin appeared in the lateral part of the posterior limb of the internal capsule and in the central part of the corona radiata and became more prominently visible in the cortex bordering the central sulcus.

Age Factors↗

PubMed1997

Comparison of MRI criteria at first presentation to predict conversion to clinically definite multiple sclerosis.

We compared MRI criteria used to predict conversion of suspected multiple sclerosis to clinically definite multiple sclerosis. Seventy-four patients with clinically isolated neurological symptoms suggestive of multiple sclerosis were studied with MRI. Logistic regression analysis was used to remove redundant information, and a diagnostic model was built after each MRI parameter was dichotomized according to maximum accuracy using receiver operating characteristic analysis. Clinically definite multiple sclerosis developed in 33 patients (prevalence 45%). The optimum cut-off point (number of lesions) was one for most MRI criteria (including gadolinium-enhancement and juxta-cortical lesions), but three for periventricular lesions, and nine for the total number of T2-lesions. Only gadolinium-enhancement and juxta-cortical lesions provided independent information. A final model which, in addition, included infratentorial and periventricular lesions, had an accuracy of 80%, and having more abnormal criteria, predicted conversion to clinically definite multiple sclerosis strongly. The model performed better than the criteria of Paty et al. (Neurology 1988; 38: 180-5) and of Fazekas et al. (Neurology 1988; 38: 1822-5). We concluded that a four-parameter dichotomized MRI model including gadolinium-enhancement, juxtacortical, infratentorial and periventricular lesions best predicts conversion to clinically definite multiple sclerosis.

False Negative Reactions↗

PubMed1997

Relationships between the orientation and moment arms of the human jaw muscles and normal craniofacial morphology.

It has been suggested that subjects with increased vertical craniofacial dimensions have relatively oblique orientated jaw muscles with a reduced possibility to restrain the vertical component of craniofacial growth. To test this hypothesis, relationships were investigated between the spatial orientation of the jaw muscles and the craniofacial morphology. Computer reconstructions of the external shape of the jaw muscles of 30 adult males with a normal skull were made with the use of serial magnetic resonance imaging (MRI) scans. The orientation of the jaw muscles was defined by a regression line through the centroids of the serial cross-sections. Sagittal and frontal projections of the moment arms of the muscles were measured with respect to the centre of the ipsilateral condyle. Craniofacial morphology was analysed three-dimensionally using lateral head films and coronal MRI scans. The cephalometric data were analysed statistically using regression and factor analyses. Six cephalometric factors with Eigen values higher than 1 were correlated with jaw muscle orientation and moment arm data, using a multiple regression analysis. The anterior face height factor was significantly correlated with the orientation of the jaw opening muscles in the sagittal plane but was not significantly correlated with the orientation of the mandibular elevators. The sagittal moment arms of the mandibular elevators showed significant correlations with the factors describing the gonial angle and the posterior face height. It was concluded that the variation of spatial orientation of the human jaw closing muscles is predominantly associated with the variation of mandibular morphology (expressed by the gonial angle) and the posterior face height. The orientation of the jaw opening muscles shows significant relationships with anterior vertical craniofacial dimensions. The hypothesis that persons with an increased anterior face height have relatively oblique orientated jaw elevators was rejected.

Adult↗

PubMed1997

Clinical utility of two-dimensional magnetic resonance angiography in detecting coronary artery disease.

AIMS: The accuracy of magnetic resonance angiography in detecting proximal coronary artery stenoses is unclear. We postulated that fast magnetic resonance angiography is capable of (1) imaging proximal coronary arteries, and (2) detecting stenoses of > or = 50% of their luminal diameter. METHODS AND RESULTS: Thirty-five patients, referred for analysis of angina pectoris, underwent both conventional angiography and magnetic resonance angiography of coronary arteries. A fast k-space segmented gradient-echo technique was used during breath-holds. Two observers, blinded to the results of conventional angiography, independently analysed the magnetic resonance studies for (1) length of visualized segments, and (2) presence of signal voids indicative of stenoses. From 140 proximal arteries, 15 (11%) were excluded because of incomplete imaging or degraded image quality. Mean length of the visualized segments was 9 +/- 4 mm for the left main, 62 +/- 16 mm for the left anterior descending, 21 +/- 9 mm for the left circumflex and 89 +/- 32 mm for the right coronary artery. Sensitivity for detecting > or = 50% luminal diameter stenoses was 0.00 for the left circumflex, 0.53 for the left anterior descending coronary artery, 0.71 for the RCA and 1.00 for the left main artery. Specificity varied from 0.73 for the left anterior descending coronary artery to 0.96 for the left circumflex. Inter-observer agreement was 0.90. CONCLUSION: Thus, segmented magnetic resonance angiography is capable of non-invasive imaging of proximal coronary anatomy. Its good accuracy in detecting left main coronary artery disease, intermediate accuracy in detecting right coronary artery and left anterior descending coronary artery stenoses, and low accuracy in detecting left circumflex lesions fit within a range of sensitivities and specificities found by others. Further technical advances are necessary to make the technique clinically robust.

Coronary Angiography↗