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Biomedical subjects

R F Young

Publications and source records attributed to R F Young.

At least 37 records · Page 2Linked to original sources
PubMed1996

Lesion size following Gamma Knife treatment for functional disorders.

In this study we investigated the reproducibility and consistency of the size of radiosurgical lesions produced for functional disorders. The T1 gadolinium-enhanced magnetic resonance (MR) images of 56 patients treated for parkinsonism, pain, or other functional diseases were used to measure 140 lesion sizes at various times after radiosurgical treatment (1-26 months, mean: 11.3 months). Only the 4-mm collimator was used to create the lesions. The maximum dose ranged from 110 to 180 Gy (mean: 145 Gy). In 42 cases (78%), one isocenter was used to create the lesion. Thirteen lesions (20%) were created with two isocenters and in 1 case, three isocenters were used. Lesions were detectable on MR images as early as 30 days after treatment. The maximum lesion volume was reached after 6-12 months and ranged from nondetectable to more than 4,000 mm3. Larger lesion volumes were strongly associated with the use of more than one isocenter. In addition, maximum doses of 160 Gy or more increased the likelihood of producing lesions larger than expected. It is therefore concluded that the use of the Gamma Knife for the treatment of functional disorders is safest when single-isocenter shots with the 4-mm collimator and a maximum dose of less than 160 Gy are used.

Adult↗
PubMed1996

Electrophysiological target localization is not required for the treatment of functional disorders.

A total of 117 patients underwent 124 functional stereotactic procedures with the Leksell Gamma Knife to treat trigeminal neuralgia, movement disorders and chronic pain. Target identification was performed with stereotactic magnetic resonance imaging alone without electrophysiologic localization. Clinical observation of these patients over 1-41 months indicates that the efficacy of the procedure is comparable with that seen with open stereotactic procedures where electrophysiological localization is used. Using current techniques, the complications of functional neurosurgery with the Gamma Knife are nearly nonexistent. We believe that functional neurosurgery can be performed effectively and safely without electrophysiological localization, using the Leksell Gamma Knife.

Chronic Disease↗
PubMed1996

Stereotactic radiosurgery for trigeminal neuralgia: a multiinstitutional study using the gamma unit.

A multiinstitutional study was conducted to evaluate the technique, dose-selection parameters, and results of gamma knife stereotactic radiosurgery in the management of trigeminal neuralgia. Fifty patients at five centers underwent radio-surgery performed with a single 4-mm isocenter targeted at the nerve root entry zone. Thirty-two patients had undergone prior surgery, and the mean number of procedures that had been performed was 2.8 (range 1-7). The target dose of the radiosurgery used in the current study varied from 60 to 90 Gy. The median follow-up period after radiosurgery was 18 months (range 11-36 months). Twenty-nine patients (58%) responded with excellent control (pain free), 18 (36%) obtained good control (50%-90% relief), and three (6%) experienced treatment failure. The median time to pain relief was 1 month (range 1 day-6.7 months). Responses remained consistent for up to 3 years postradiosurgery in all cases except three (6%) in which the patients had pain recurrence at 5, 7, and 10 months. At 2 years, 54% of patients were pain free and 88% had 50% to 100% relief. A maximum radiosurgical dose of 70 Gy or greater was associated with a significantly greater chance of complete pain relief (72% vs. 9%, p = 0.0003). Three patients (6%) developed increased facial paresthesia after radiosurgery, which resolved totally in one case and improved in another. No patient developed other deficits or deafferentation pain. The proximal trigeminal nerve and root entry zone, which is well defined on magnetic resonance imaging, is an appropriate anatomical target for radiosurgery. Radiosurgery using the gamma unit is an additional effective surgical approach for the management of medically or surgically refractory trigeminal neuralgia. A longer-term follow-up review is warranted.

Adult↗
PubMed1995

Technique of stereotactic medial thalamotomy with the Leksell Gamma Knife for treatment of chronic pain.

Nineteen patients underwent a total of 24 medial thalamic lesions made with the Leksell Gamma Knife for the treatment of chronic intractable pain after extensive prior medical and surgical intervention had failed to provide pain relief. The lesion locations were based on prior experience with open radiofrequency medial thalamotomies for the treatment of pain and were directed at the intralaminar, mediodorsal, centromedian, and parafascicular nuclei. All lesions were made with the 4 mm collimator helmet at radiosurgical doses from 140-180 Gray. Follow-up MRI scans indicated anatomically distinct lesions which developed 3-6 weeks after the procedure and were fully formed by 8-12 weeks. The lesion volumes averaged 300-400 mm3 for a single isocentre, 600-900 mm3 for two isocentres, and 900-1100 mm3 for three isocentres. One patient developed a lesion 5500 mm3 in volume after a two isocentre lesion at 160 Gray. Of 15 patients who have been followed for more than 3 months (average follow-up 12 months) four patients (27%) are virtually pain free and functioning normally, whereas five other patients (33%) achieved greater than 50% pain relief. Thus 9/15 patients (60%) have had worthwhile benefit from medial thalamotomy with the Gamma Knife. Medial thalamotomy with the Gamma Knife produces thalamic lesions which are reliable in size, shape and location with a low complication rate and offers a minimally invasive, cost effective treatment for certain selected patients with chronic intractable pain.

Chronic Disease↗
PubMed1995

The context of caregiving and well-being outcomes among African and Caucasian Americans.

This study examined the effects of race on caregiving outcomes among 180 African American and white American caregiver/care recipient dyads subsequent to a heart attack. Despite significant bivariate associations with caregiver characteristics, the caregiving situation, attitudes toward care provision, and burden, race had no effect on burden or depression when all caregiving context variables were controlled. Thus, caring for an ailing elder evoked more race similarities than differences. This suggests that some previously established models of cultural and racial differences in caregiving may need to be reconsidered.

Adaptation, Psychological↗
PubMed1995

Gamma Knife thalamotomy for the treatment of persistent pain.

Twenty patients who suffered persistent intractable pain from a variety of disorders underwent medial thalamotomy with the Leksell Gamma Knife. The lesions were directed at the intralaminar nuclei, the lateral portion of the medial dorsal nucleus, the centromedian and the parafascicular nuclei. Lesions were made with radiation doses from 140 to 180 Gy using a 4-mm beam collimator helmet and either a single isocenter (1 patient), two isocenters (17 patients) or three isocenters (2 patients). Two thirds of the patients experienced either excellent or good pain relief in a follow-up period between 1 and 22 months. One patient showed temporary complications which resolved, and 2 other patients also suffered complications which currently are improving. One patient died due to radiation necrosis following a bilateral thalamotomy. Gamma Knife thalamotomy may offer a potentially safe and effective alternative for the treatment of certain difficult persistent pain problems.

Chronic Disease↗
PubMed1995

Electrical stimulation of the trigeminal nerve root for the treatment of chronic facial pain.

Between March 1990 and December 1992, 23 patients with chronic intractable facial pain due to various forms of injury to the trigeminal nerve or nerve root underwent implantation of an electrical stimulating system to treat their pain. All patients had failed previous extensive pain treatment efforts. A monopolar platinum-iridium electrode was implanted on the trigeminal nerve root via percutaneous puncture of the foramen ovale. All patients experienced at least 50% reduction in pain intensity during a period of trial stimulation and underwent internalization of the electrode and connection to a completely implanted pulse generator. Independent assessment of the effect of stimulation was obtained by a specially trained nurse practitioner. Over a mean follow-up period of 24 months, six patients reported nearly complete relief of pain and six others reported at least a 50% reduction in pain intensity using a visual analog scale. Thus, 12 (52%) of the 23 patients achieved 50% or greater reduction in pain intensity. Although changes in the patterns of analgesic medication usage were few, six patients (26%) now experience a normal life style. Only one complication was seen, namely a dislocated electrode, which was easily replaced. Chronic electrical stimulation of the trigeminal nerve root appears to be an easy and safe technique for providing relief of chronic facial pain related to injury to the trigeminal nerve in a significant number of patients.

Adult↗
PubMed1994

Medial thalamotomy with the Leksell Gamma Knife for treatment of chronic pain.

The authors describe 10 patients who underwent stereotactic medial thalamotomy with the Leksell Gamma Knife for treatment of chronic intractable pain. The pain was related to structural spinal disorders (4), postherpetic neuralgia (2), spinal cord injury (1), thalamic syndrome (1), anesthesia dolorosa of the face (1), and brainstem infarction (1). All patients had undergone extensive treatment with a variety of modalities prior to gamma thalamotomy. Nine patients underwent unilateral and one patient bilateral lesions. Magnetic resonance imaging (MRI) was used for target localization and the lesions were directed toward the intralaminar nuclei, the lateral portion of the medial dorsal nucleus, the centrum medianum and parafascicular nuclei. The lesions were made with radiation doses of 160-180 Gy using a 4 mm beam collimator and either a single isocenter (1 patient) or two isocenters (9 patients). Follow-up MRI scans in all patients showed well localized lesions. Three patients experienced excellent pain relief, four had good pain relief and three were failures. No complications were seen in any of the patients. In the past gamma thalamotomy was used mainly for treatment of pain related to malignancies but our results indicate that it may also be a safe and effective treatment for pain of nonmalignant origin as well.

Aged↗
PubMed1993

Control of gluconeogenic growth by pps and pck in Escherichia coli.

It is well-known that Escherichia coli grows more slowly on gluconeogenic carbon sources than on glucose. This phenomenon has been attributed to either energy or monomer limitation. To investigate this problem further, we varied the expression levels of pck, encoding phosphoenolpyruvate carboxykinase (Pck), and pps, encoding phosphoenolpyruvate synthase (Pps). We found that the growth rates of E. coli in minimal medium supplemented with succinate and with pyruvate are limited by the levels of Pck and Pps, respectively. Optimal overexpression of pck or pps increases the unrestricted growth rates on succinate and on pyruvate, respectively, to the same level attained by the wild-type growth rate on glycerol. Since Pps is needed to supply precursors for biosyntheses, we conclude that E. coli growing on pyruvate is limited by monomer supply. However, because pck is required both for biosyntheses and catabolism for cells growing on succinate, it is possible that growth on succinate is limited by both monomer and energy supplies. The growth yield with respect to oxygen remains approximately constant, even though the overproduction of these enzymes enhances gluconeogenic growth. It appears that the constant yield for oxygen is characteristic of efficient growth on a particular substrate and that the yield is already optimal for wild-type strains. Further increases in either Pck or Pps above the optimal levels become growth inhibitory, and the growth yield for oxygen is reduced, indicating less efficient growth.

Escherichia coli↗
PubMed1993

Multiple spinal meningiomas: a case of 47 distinct lesions in the absence of neurofibromatosis or identified chromosomal abnormality.

The authors present a unique case of multiple spinal meningiomas with the late development of intracranial lesions. The patient had 47 distinctly separate, yet histologically identical, lesions excised, with many others noted at the time of surgery and by radiographic studies. He was evaluated for neurofibromatosis and was found to have neither Type I nor Type II. Genetic analysis, including restriction fragment length polymorphism analysis, was performed and detected no abnormalities.

Adult↗
PubMed1993

Gender, recovery from late life heart attack, and medical care.

It has only recently been recognized that there are significant gender effects on heart disease and that women face increasing risks as they age. A longitudinal study of 246 older myocardial infarction (MI) patients included a 1/3 sample of women. Findings indicate that over the first post-MI year, women had greater risk of death, cardiac distress and reinfarction. Cardiac symptoms of men declined while those of women increased. Several medical care and social disadvantages were found among the post-MI women, including less aggressive cardiac care. Furthermore, since morbidity and mortality were related to medical care and social disadvantages, the results support gender-age stratification theories.

Aged↗
PubMed1993

Release of beta-endorphin and methionine-enkephalin into cerebrospinal fluid during deep brain stimulation for chronic pain. Effects of stimulation locus and site of sampling.

The authors systematically studied the release of the endogenous opioid peptides beta-endorphin and methionine (met)-enkephalin into the cerebrospinal fluid (CSF) during deep brain stimulation in patients suffering from otherwise intractable chronic pain. Nine patients were included in the study; six had stimulation electrodes placed in both the periventricular gray matter (PVG) and the thalamic nucleus ventralis posterolateralis (VLP) and three in the PVG only. Immunoreactivity of beta-endorphin and met-enkephalin (beta-EPir and MEir, respectively) was measured by radioimmunoassays in ventricular and lumbar CSF samples obtained before, during, and after stimulation. Prestimulation concentrations of beta-EPir and MEir were lower in ventricular than in lumbar CSF (6.6 +/- 0.5 vs. 13.7 +/- 1.0 pmol/liter, p = 0.0001, for beta-EPir; 33.6 +/- 5.1 vs. 48.3 +/- 3.2 pmol/liter, p < 0.05, for MEir). Ventricular CSF concentrations of both beta-EPir and MEir increased significantly during PVG stimulation, whereas VPL stimulation was without effect. No changes were seen in lumbar CSF levels of the peptides during stimulation in either site. A significant inverse relationship was found between the "during:before stimulation" ratios of visual analog scale ratings and beta-EPir levels during PVG stimulation. The beta-EPir and MEir concentration during:before stimulation ratios were positively correlated, whereas no correlation was present in prestimulation samples from ventricular or lumbar CSF. High-performance liquid chromatography of ventricular CSF pools obtained during PVG stimulation revealed that major portions of beta-EPir and MEir eluted as synthetic beta-endorphin and met-enkephalin, respectively, thus documenting the release of beta-endorphin and met-enkephalin into ventricular CSF during PVG stimulation. The finding of a direct relationship between beta-EPir release and pain alleviation may suggest a role for beta-endorphin in the analgesic mechanism of PVG stimulation.

Adult↗
PubMed1992

Intracranial pressure monitoring: fiberoptic monitor compared with the ventricular catheter.

Among the frequently utilized intracranial pressure (ICP) monitoring devices employed in neurosurgical practice is the Camino fiberoptic monitor. Several recent studies have described results with the Camino monitor and compared it with other forms of ICP monitoring with varying results and conclusions. The aim of this study was to compare simultaneous ICP readings from the Camino fiberoptic monitor placed in the brain parenchyma and from a ventricular catheter. ICP values were recorded for up to 118 hours in 10 patients. It was determined that the Camino ICP measurements exceeded those of a ventricular catheter in 66% of total measurements for the 10 patients. The mean ICP difference between the Camino fiberoptic system and the ventricular catheter was 9.2 +/- 7.8 mm Hg. This result suggests that the correlation between intraparenchymal pressure measured by the Camino fiberoptic monitor and the intraventricular pressure is not as close as previously described.

Catheterization↗
PubMed1992

Stimulation of glucose catabolism in Escherichia coli by a potential futile cycle.

Fifteen-fold overexpression of phosphoenolpyruvate synthase (Pps) (EC 2.7.9.2) in Escherichia coli stimulated oxygen consumption in glucose minimal medium. A further increase in Pps overexpression to 30-fold stimulated glucose consumption by approximately 2-fold and resulted in an increased excretion of pyruvate and acetate. Insertion of two codons at the PvuII site in the pps gene abolished the enzymatic activity and eliminated the above-described effects. Both the active and the inactive proteins were detected at the predicted molecular weight by polyacrylamide gel electrophoresis. Therefore, the observed physiological changes were due to the activity of Pps. The higher specific rates of consumption of oxygen and glucose indicate a potential futile cycle between phosphoenolpyruvate (PEP) and pyruvate. A model for the stimulation of glucose uptake is presented; it involves an increased PEP/pyruvate ratio caused by the overexpressed Pps activity, leading to a stimulation of the PEP:sugar phosphotransferase system.

Alleles↗