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Biomedical subjects

J M Stevens

Publications and source records attributed to J M Stevens.

At least 127 records · Page 7Linked to original sources
PubMed1992

Hippocampal volumetric and morphometric studies in frontal and temporal lobe epilepsy.

The most common temporal lobe pathology is Ammons Horn sclerosis (AHS), and several different imaging techniques have been utilized to detect this with varying success. We describe the clinical application of magnetic resonance imaging (MRI) using a three-dimensional volume technique which allows total hippocampal volume to be measured and symmetry evaluated. Hippocampal surface area was calculated in sequential 1.5 mm thick contiguous images, using a GE IC workstation. Total volumes and surface areas were calculated. The cross-sectional surface area at 1.5 mm intervals was displayed graphically, permitting morphometric analysis of the hippocampus throughout its length. Focal atrophy within any part of the hippocampal formation (HF) and its extent could thus be assessed. Patients with well-lateralized temporal lobe epilepsy (TLE) (n = 20) and well-defined frontal lobe epilepsy (FLE) (n = 20) were studied, and volumes compared with normal values derived from 10 neurologically normal controls. Asymmetric hippocampal volume loss was demonstrated in all 20 patients with clinically typed TLE, but not in normal controls or patients with FLE. Volume loss distribution was anterior in 12 patients, posterior in one patient and widespread in seven patients. Secondarily generalized seizures were strongly associated with widespread loss. This method of surface area and volumetric analysis of the hippocampus in TLE can demonstrate asymmetry and focal involvement, and help distinguish between hippocampal and frontal pathologies.

Adult↗
PubMed1991

Extended use of cranial CT in the evaluation of patients with stroke and transient ischaemic attacks.

The hypothesis was explored that patterns of ischaemic brain damage shown by CT may be of greater value in estimating the relevance of angiographic stenosis in the carotico-vertebral arteries in some patients than presenting clinical features. Five angiographic and six CT abnormalities were defined and charted independently in a blinded manner in 312 patients whom clinical features and subsequent management were known. Charts were combined for statistical analysis. Statistically significant associations were found between two types of CT lesion and angiographic abnormalities, but these were present in only 18% of cases. The distribution of clinical features did not differ significantly within this subset compared to the whole population, from which it was concluded that the hypothesis was upheld. Furthermore significantly more patients in this subset were subjected to carotid endarterectomy, suggesting that management decisions may have been modulated by CT findings in some patients.

Adult↗
PubMed1991

Stepwise correction of anaemia by subcutaneous administration of human recombinant erythropoietin in patients with chronic renal failure maintained by continuous ambulatory peritoneal dialysis.

Sixteen anaemic CAPD patients (Hb less than 9 g/dl) were treated with thrice-weekly subcutaneous recombinant erythropoietin, epoetin-alfa. The dose was adjusted to induce a stepwise increase in haemoglobin. Fourteen patients reached a first target haemoglobin of 11.0-11.5 g/dl and eight of these a second of 13.0-13.5 g/dl, but one could not be maintained at this level. Failure to reach or maintain the second target in nine subjects was accounted for by incomplete responses associated with infection in one, extreme shortening of red-cell survival in another, and was unexplained in one subject. These three received the maximum dose studied of 450 IU/kg per week. Six other subjects were withdrawn from the study for reasons unrelated to treatment with erythropoietin. The median dose required to maintain the haemoglobin at 11.0-11.5 g/dl was 75 IU/kg per week and at 13.0-13.5 g/dl was 150 IU/kg per week. Quality of life, assessed in 12 patients at haemoglobin 11.0-11.5 g/dl, showed significant improvement in energy, and at 13.0-13.5 g/dl improvements in sleep and emotional wellbeing became significant. Twelve subjects required either institution of, or an increase in, treatment for hypertension. The thrice-weekly subcutaneous doses of erythropoietin were well tolerated and were a convenient and effective treatment for anaemia in patients on CAPD.

Adult↗
PubMed1991

Transoral decompression and posterior stabilisation in Morquio's disease.

A 3.5 year old boy with Morquio's disease was referred with a persisting left hemiparesis four months after a fall and was found to have craniocervical junction compression due to atlantoaxial subluxation and significant anterior soft tissue compression. Transient unconsciousness at the time of the fall was probably due to medullary concussion as a result of hyperextension, not a head injury. Spinal cord compression due to atlantoaxial subluxation at the craniovertebral junction is a major cause of disability and death in these patients. Once cervical myelopathy appears, early posterior occipitocervical fusion has been advocated in order to arrest the progression of neurological disability and this is successful in most cases. This conventional approach was considered unsafe because of the significant anterior compression. A combined anterior transoral decompression with posterior fusion to deal with this particularly difficult problem is described.

Child, Preschool↗
PubMed1991

Damaged ligaments at the craniocervical junction presenting as an extradural tumour: a differential diagnosis in the elderly.

An extradural mass at the craniocervical junction causing progressive neurological disability in five elderly patients is described. The lesion, which might be confused with a meningioma or other tumour, is composed of amorphous degenerate fibrocartilaginous material and could be due to degeneration of the ligaments responsible for atlanto-axial stability. Recognition of the condition early is important as the patient's clinical condition will deteriorate without decompression. Anterior transoral removal is relatively simple, unlike surgery for tumours in the area, and will not destabilise the craniovertebral junction. It is likely that a proportion of these lesions are undetected, misdiagnosed or untreated to the detriment of the patient.

Aged↗
PubMed1991

The odontoid process in Morquio-Brailsford's disease. The effects of occipitocervical fusion.

High definition computed cervical myelograms have been made in flexion and extension in 13 patients with Morquio-Brailsford's disease. We observed that: 1) odontoid dysplasia was present in every case, with a hypoplastic dens and a detached distal portion which was not always ossified; 2) atlanto-axial instability was mild, and anterior atlanto-axial subluxation was absent in most cases; 3) severe spinal cord compression, when present, was due to anterior extradural soft-tissue thickening; 4) this compression was not relieved by flexing or extending the neck and was manifested early in life; 5) posterior occipitocervical fusion resulted in disappearance of the soft-tissue thickening and normalisation of subsequent development of the dens. We conclude that the severity of neurological involvement at the craniovertebral junction was determined by soft-tissue changes, not by the type of odontoid dysplasia nor by subluxation. Posterior occipitocervical fusion proved to be an effective treatment.

Adult↗
PubMed1990

Identifiable causes for poor outcome in surgery for cervical spondylosis. Post-operative computed myelography and MR imaging.

Outcome from surgery for cervical spondylosis is often disappointing. To identify possible causes of poor outcome 56 such patients referred for post-operative computed myelography or MRI were evaluated, 22 of which eventually had further surgery. Alternative diagnoses to cervical spondylosis were eventually established in 14.3%; 26.8% had spinal cord atrophy 15.6% of which also had myelomalacia; 28.6% had diffuse spinal canal stenosis; and in 57.1% surgery had failed to decompress the spinal canal. These findings can be partly explained by patient selection criteria; nevertheless they do serve to emphasises the point often ignored in discussions of the efficacy of surgery in cervical spondylosis, that operations significantly often fail to achieve adequate decompression. Furthermore there was no evidence in this material that osteophytes regress after spinal fusion.

Adult↗
PubMed1990

Clinical Utility of cranial CT in HIV positive and AIDS patients with neurological disease.

An analysis was made of the clinical, pathological and radiological data relating to 117 requests for cranial CT on 83 patients who were HIV positive or had AIDS in one year at St Mary's Hospital. Central to the design was grouping of the patients according to clinical presentation. The aim was to establish whether there was evidence to support the view that, because of their immunocompromised state, these patients may commonly harbour serious, potentially treatable intracranial disease without the usual overt clinical signs. No patient who was only HIV antibody positive had treatable intracranial disease without focal neurological signs. In patients with AIDS, treatable or potentially treatable lesions were mainly confined to those with objective neurological signs or seizures. There is little evidence in this data to support the original hypothesis. While it would be inappropriate to advise that CT should never be carried out in the absence of focal signs or seizures, the results of this study should be useful in ascribing an appropriate degree of urgency to requests for cranial CT in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1990

The operative management of basilar impression in osteogenesis imperfecta.

Four patients with osteogenesis imperfecta and neurologically significant basilar impression have been treated over the past 8 years. The experience has resulted in changes in our therapeutic strategy for this particularly difficult problem. These cases are discussed with respect to the disease process, neurological involvement, radiological findings, and modes of surgical therapy. The errors in management as well as the success resulting from our learning experience are described. Currently, we recommend the extensive removal of the anterior bony compression by a transoral approach. This should be followed by a posterior rigid fixation that transfers the weight of the head to the thoracic spine, in an effort to prevent further basilar invagination.

Adult↗
PubMed1990

Subcutaneous administration of recombinant human erythropoietin to subjects on continuous ambulatory peritoneal dialysis: an erythrokinetic assessment.

Erythrokinetic studies were performed in subjects on continuous ambulatory peritoneal dialysis, during a trial examining the effectiveness of subcutaneous administration of recombinant human erythropoietin (r-HuEPO) in correcting the anaemia associated with end stage renal disease. 15 subjects (mean haemoglobin concentration 6.9 g/dl, SD 1.1) entered the study, and during treatment 9 were restudied at a haemoglobin concentration of 11-11.5 g/dl and six underwent a third study at haemoglobin 13-13.5 g/dl. By adjusting the dose of r-HuEPO, a stepwise increase in haemoglobin concentration was achieved, and this was accompanied by increases in total red cell volume and erythron transferrin uptake. Plasma volume decreased as red cell volume increased, leaving total blood volume essentially unchanged. Red cell survival, modestly reduced before treatment (mean 64, range 44-96 d, n = 6) tended to increase during treatment and when subjects were retested at a haemoglobin concentration of 13-13.5 g/dl (after 38-62 weeks treatment), the mean increase in red cell survival was 20 d (95% confidence interval 1-39 d). Thus subcutaneous r-HuEPO is effective in correcting the anaemia of end stage renal disease when administered thrice weekly to subjects on continuous ambulatory peritoneal dialysis. It produces an increase in haemoglobin concentration primarily by expanding the erythron, and may have a secondary effect, seen after several months of treatment, of increasing red cell survival.

Adult↗
PubMed1990

Three cases of craniopharyngioma showing optic tract hypersignal on MRI.

Three patients presenting with visual failure had MRIs with hypersignal extending from the region of the optic chiasm along both optic tracts in 2 cases, and along 1 optic tract in the 3rd. In all patients intrinsic tumor of the chiasm was the most likely diagnosis based on MRI appearances, but all 3 had craniopharyngioma.

Adult↗
PubMed1989

Fourier transform infrared assay of membrane lipids immobilized to silica: leaching and stability of immobilized artificial membrane-bonded phases.

A nondestructive, sensitive assay to monitor the hydrocarbon content of silica-based chromatography particles has been developed. The assay requires a microscope accessory interfaced with a Fourier transform infrared (FTIR) spectrometer. For determining hydrocarbon content, undiluted alkyl-silica-bonded phases were pressed into a thin wafer. Hydrocarbon content was quantitated using the integrated hydrocarbon band intensity between 2995 and 2825 cm-1 [i.e., band area C-H] and the integrated silica oxide band intensity between 1945 and 1780 cm-1 [i.e., band area Si-O]. Plotting the [band area C-H]/[band area Si-O] ratio vs the carbon content determined by elemental analysis gave a correlation coefficient of r = 0.997. The FTIR assay was validated on 5-, 7-, and 12-microns silica particles using three different immobilized artificial membrane (IAM) silica-bonded phases. The utility of the FTIR assay in determining hydrocarbon content was demonstrated by evaluating hydrocarbon leaching from IAM phases exposed to mobile-phase solvents. The ability of organic solvents to leach hydrocarbon from IAM phases containing phosphatidylcholine (PC) as the immobilized ligand was chloroform greater than ethanol approximately methanol greater than ethyl acetate greater than methylene chloride greater than acetonitrile greater than acetone. Acetone and acetonitrile cause very little hydrocarbon leaching from HPLC-IAM.PC columns. When challenged with different mobile phases, IAM.PC columns perfused with mobile phase are more stable than IAM.PC-bonded phases stirred in mobile phases. IAM.PC contains lecithin linked to silica by amide bonds.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗