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J L Merx

Publications and source records attributed to J L Merx.

At least 19 recordsLinked to original sources
PubMed1998

Falcine sinus and occipital encephalocele: a magnetic resonance venography study.

OBJECT: Occipital encephaloceles are relatively frequently encountered. Many investigators have addressed the embryogenesis of these formations, but the dural system has never before been studied. In this retrospective analysis the authors sought to gain a better understanding of the origins of these defects. METHODS: The charts and radiological examinations, especially the magnetic resonance venography studies, were reviewed in seven patients. In six patients the straight sinus was absent. Drainage of the galenic system took place through a sinus within the falx, also known as a falcine sinus. The tentorium was not seen in five patients. CONCLUSIONS: The combination of an absent straight sinus and dysplastic tentorium is no coincidence: both develop within the same mesenchyme in the mesencephalic flexure. Distortion of the mesenchyme by a neural tube defect, causing an occipital encephalocele, will lead not only to disorders of the tentorium but also of the straight sinus.

Adult↗
PubMed1996

[Functional MRI: imaging of motor cortex function].

OBJECTIVE: To image the motor cortex with functional MRI (fMRI), and locate the activated area with the proportional grid of Talairach. DESIGN: Descriptive. SETTING: St. Radboud Academic Hospital Nijmegen. METHODS: In ten volunteers functional images of the motor cortex were made during execution of a motor task (finger movements). From the functional images the positions of activated areas were calculated using the 3D Talairach grid system. RESULTS: fMRI of the motor cortex was possible using a 1.5 T MRI scanner. Task activation of the motor cortex gave a signal increase in Brodmann's area 4, the precentral gyrus. CONCLUSION: Imaging of the active motor cortex with fMRI is feasible. The use of the 3D Talairach proportional grid system for the calculation of the position of an activated area in the motor cortex is possible with adequate accuracy.

Adult↗
PubMed1995

MRI in patients with suspected vascular parkinsonism.

To determine whether MRI can reveal more vascular lesions in patients clinically suspected of having vascular parkinsonism, we compared 15 such patients with 15 patients who had idiopathic Parkinson's disease and 10 hypertensive controls. Patients with suspected vascular parkinsonism had significantly more subcortical lesions than those with Parkinson's disease or hypertension. The cutoff point that best distinguished patients with suspected vascular parkinsonism from patients with Parkinson's disease was a 0.6% level of lesioned brain tissue volume. There were two types of vascular parkinsonism: one had an acute onset and lesions located in the subcortical gray nuclei (striatum, globus pallidus, thalamus); the other had an insidious onset and lesions diffusely distributed in the watershed areas.

Aged↗
PubMed1994

Focal dystonia and speech impairment responding to anticholinergic therapy.

Focal dystonia of the right hand and speech impairment as a result of a circumscribed left-sided anterior thalamic lesion is reported in a 9-year-old girl with borderline normal psychomotor development. Both focal dystonia and speech impairment improved during anticholinergic treatment and worsened after drug withdrawal.

Cerebral Infarction↗
PubMed1994

Renal artery stenosis in moyamoya syndrome.

Extracranial manifestations of vascular occlusive disease, such as renovascular hypertension, are rare in moyamoya syndrome. Histopathological examination suggests a common denominator. Surgical or endoluminal correction of these lesions is feasible. Moyamoya syndrome is not considered to be a contraindication for organ donation for transplantation.

Adult↗
PubMed1991

Asymmetric onset of sympathetic blockade in epidural anaesthesia shows no relation to epidural catheter position.

A radiological study was performed of the relation between onset of sympathetic blockade in lumbar epidural anaesthesia and the position of the epidural catheter. In 20 patients scheduled for extracorporeal shock wave lithotripsy (ESWL), the onset of sympathetic blockade after epidural anaesthesia (catheter insertion at the presumed level L2-L3, and injection of 20 ml prilocaine 2% with epinephrine 5 micrograms/ml) was objectively evaluated by photoplethysmography. The onset was asymmetrical in 18 patients, and symmetrical in only two. Just before the start of ESWL, the position of the epidural catheter was checked by radiography after injection of 0.5 ml iohexol 300 mg/ml (Omnipaque 300). The radiopaque contrast medium was found median (n = 2), right (n = 7) and left (n = 11) of the midline. In only 9 patients was the earliest onset of sympathetic blockade correlated with the side of the catheter position, and thus no relation between catheter position and onset of sympathetic blockade was found.

Anesthesia, Epidural↗
PubMed1991

[Subdural empyema. The importance of rapid diagnosis].

We describe a fourteen year old girl with a subdural empyema. A survey of the literature is given with regard to the diagnosis, treatment and outcome. We emphasise the importance of fast diagnosis and proper treatment.

Adolescent↗
PubMed1989

The tethered spinal cord syndrome: a correlation of radiological features and peroperative findings in 30 patients.

The aim of this investigation is to evaluate the accuracy of the diagnostic parameters of the radiological features, especially in conventional lumbar myelography, since these will be used in the future as a gold standard for new developing diagnostic methods like ultrasonography (US) and magnetic resonance imaging (MRI). A short review of the clinical symptoms and diagnostic radiology of the tethered spinal cord (TSC) is given. The radiological features of the TSC syndrome are compared with the peroperative findings in 30 patients investigated and operated in our hospital. All patients showed lumbar or sacral osseous malformations on the plain X-ray films. This means a high diagnostic sensitivity although the specificity for TSC is low. Conventional myelography had a sensitivity of 0.82 and positive predictive value of 0.94, while the specificity and negative predictive value are respectively 0.96 and 0.85. The positive predictive value of the total diagnostic procedure of plain X-ray films and lumbar myelography for TSC may be estimated at 1.

Humans↗
PubMed1989

Accuracy of ultrasonic evaluation of lumbar intervertebral discs by an anterior approach.

The aim of this investigation was to evaluate the diagnostic accuracy of sonography of the lower lumbar intervertebral discs. The results in 50 patients were compared to lumbar myelography. A short description of the sonographic appearance of the normal and pathological lumbar disc is given. The sonographic examination was inconclusive in 18% of the patients because of obesity, meteorism or diminution of the intervertebral disc space. In nearly half of these patients a herniation was found at myelography and confirmed at surgery. The study revealed a sensitivity varying from 0.63 to 0.77. Compared to lumbar myelography and CT scanning we find this too low to support its addition in lumbar disc disease because of non-invasiveness or lack of radiation alone.

Humans↗
PubMed1988

Quality analysis of DSA equipment.

In the framework of a quality analysis project for the improvement of digital subtraction angiography (DSA) equipment, an inventory was made of the image quality and radiation dose of DSA equipments in six hospitals in the Netherlands. The image quality was investigated with a contrast detail (CD) phantom. The entrance dose of the radiation on this phantom and the skin dose at the level of the eye lenses and the thyroid gland were measured in these hospitals using a human phantom during a standardised simulated DSA examination of the aortic arch and brachiocephalic arteries, by means of thermo-luminescence dosimeters (TLD). To establish the relation of these measurements on the human phantom and real patient examinations, the same measurements were carried out in our own hospital on 16 patients during a comparable DSA examination. To find the difference from the dose in conventional angiography (CA) the same measurements were carried out in our hospital on 11 patients during a comparable examination. These dose measurements were also carried out on the human phantom with the use of the same CA equipment. We found large differences in image quality in the various hospitals. Within one hospital, monitor images were better than hard copy images. These differences were strongly related to the amount of radiation used, to the technique of storing the images (digital or analogue) and to the quality of the equipment used to make hard copies (the imager). Recommendations are made for improvement and quality control.

Angiography↗
PubMed1988

Improvement of IVDSA of the brachiocephalic arteries using a non-ionic contrast medium.

The introduction of IVDSA provides a safer method of angiographic investigation of the aortic arch and brachiocephalic arteries than conventional angiography in patients with cerebro-vascular disease. The quality of visualization however decreases. Instead of changing over to IADSA we find it worthwile to try to improve IVDSA in different ways. One of them is represented in this prospective double blind cross-over study in which we have investigated the effects of using an isotonic non-ionic contrast medium, iohexol (omnipaque), in comparison to meglumin-sodium-diatrizoate (urografin) which is widely used. Iohexol causes less severe side-effects, less severe artifacts and a better image quality. A statistical relation between parameters could not be established. A lag-effect exists for side-effects. The necessity of using low osmolar contrast media is discussed.

Angiography↗
PubMed1988

Comparison of brachiocephalic angiography and IVDSA in the same group of patients.

In this investigation for the first time conventional angiography (CA) and intravenous digital subtraction angiography (IVDSA) of the aortic arch and brachiocephalic vascular territory is compared in the same group of 25 patients. The quality of the image derived from IVDSA is inferior to that of CA and, moreover, varies with the location. If sufficiently good, IVDSA has an accuracy of 81 to 91% in comparison to CA for stenotic lesions depending on the site. Ulcerations are missed more frequently than with CA. Discrepancies between IVDSA and CA are caused mainly by misregistration. According to our investigation there are multiple stenotic lesions in the brachiocephalic territory in 84% of the patients. Adequate assessment of the need for surgery in symptomatic patients can therefore only be made after complete visualization of the aortic and brachiocephalic vascular territory. If non-invasive methods, like duplex-scanning, cannot fulfill this requirement, IVDSA is the only semi-invasive method that can provide the information. It is therefore desirable to improve IVDSA technique in the near future instead changing to intra-arterial DSA (IADSA). Now already the advantages outweight the drawbacks.

Adult↗
PubMed1988

CT in neuromuscular disorders: a comparison of CT and histology.

The value of CT-examination of the muscles compared to histology was studied in a retrospective analysis of 30 patients with clinical suspicion of neuromuscular disorder. In the evaluation of the CT-results descriptive criteria were used. The histologic diagnosis came from needle-biopsies taken from the quadriceps muscle. Considering the whole group of neuromuscular disorders, CT has an overall accuracy of 84.8%, a positive predictive value of 95.5% and a negative predictive value of 63.6%. This makes the use of CT as a diagnostic tool in neuromuscular disorders a reliable examination technique. In patients with a polymyositis there is even a 100% correlation between CT findings and biopsy results. Discrepancy between the biopsy results of the quadriceps muscle and the CT findings is remarkable: the number of abnormal histological findings is twice the number of abnormal CT findings. Using the more proximal gluteal region as a biopsy site would have decreased this discrepancy and would therefore have given a better correlation between CT and histology. The choice of protocol in determining the levels to be scanned is of great importance in achieving good reproducability in follow-up CT examinations.

Adolescent↗
PubMed1987

The absent cervical pedicle syndrome. A case report.

A recent case of the absent cervical pedicle syndrome is presented. Incorrect radiological interpretation resulted in inappropriate management. A review of the literature on this congenital abnormality and a complete differential diagnosis are presented.

Adult↗
PubMed1987

Bilateral direct carotid-cavernous fistulas of traumatic and spontaneous origin: two case reports.

In the present paper we discuss two cases with bilaterally located carotid-cavernous fistulas: one of traumatic origin and the other occurring spontaneously. Most traumatic fistulas are direct, unilateral and of a high flow type. In our first case we deal with traumatic bilateral direct fistulas with a low flow, a combination which must be considered rare and is not reported in the literature so far. In our second case there are bilaterally located fistulas, occurring spontaneously. Peculiarly they are direct, instead of indirect as is to be expected in spontaneously developing fistulas, and of a low flow type. This combination too must be considered extremely rare. In both cases conservative therapy was successful, despite their difference in etiology. It appears that neither the anatomy nor the manner of onset determines the success of conservative therapy, but the fact that a fistula is of a high- or low flow type.

Aged↗