Biomedical subjects

Steve Smith

Publications and source records attributed to Steve Smith.

24 records · Page 2Linked to original sources

PubMed2002

A method for determining venous contribution to BOLD contrast sensory activation.

While BOLD contrast reflects hemodynamic changes within capillaries serving neural tissue, it also has a venous component. Studies that have determined the relation of large blood vessels to the activation map indicate that veins are the source of the largest response, and the most delayed in time. It would be informative if the location of these large veins could be extracted from the properties of the functional responses, since vessels are not visible in BOLD contrast images. The present study describes a method for investigating whether measures taken from the functional response can reliably predict vein location, or at least be useful in down-weighting the venous contribution to the activation response, and illustrates this method using data from one subject. We combined fMRI at 3 Tesla with high-resolution anatomic imaging and MR venography to test whether the intrinsic properties of activation time courses corresponded to tissue type. Measures were taken from a gamma fit to the functional response. Mean magnitude showed a significant effect of tissue type (p < 0.001) where CSF > veins approximately gray matter > white matter. Mean delays displayed the same ranking across tissue types (p < 0.001), except that veins > gray matter. However, measures for all tissue types were distributed across an overlapping range. A logistic regression model correctly discriminated 72% of the veins from gray matter in the absence of independent information of macroscopic vessels (ROC = 0.72). While tissue classification was not perfect for this subject, weighting the T contrast by the predicted probabilities materially reduced the venous component to the activation map.

Adult↗

PubMed2002

Effectiveness of intra-operative wound infiltration with long-acting local anaesthetic.

BACKGROUND: Postoperative pain relief is of importance to both patients and surgeons. One of the simpler techniques is infiltration of the surgical incision with long acting local anaesthetic. The literature is confusing, with numerous reports attesting to the value of this approach and a similar number disputing the demonstrable benefits. METHODS: A prospective, 'blinded', randomized trial was undertaken involving 18 females undergoing uncomplicated bilateral sapheno-femoral ligation. They received intraoperative bupivacaine infiltration into one or the other of their groin incisions. Postoperatively these patients were asked to assess a number of variables relating to their postoperative pain, each patient thereby acting as their own control. RESULTS: There was no significant difference in the postoperative pain experience between groins infiltrated with bupivacaine and those not infiltrated. Two patients developed wound infections and both of these occurred on the sides which had been infiltrated with bupivacaine, however this was not statistically significant. There was no difference found in pain experience with respect to pre- versus post-incision infiltration. CONCLUSION: Intraoperative wound infiltration with bupivacaine is widely employed as a method of minimizing postoperative pain. This study was unable to demonstrate a benefit of employing the technique in terms of a reduction in the patient's perception of pain. By having each patient act as their own control, we have avoided one of the major deficiencies of previous studies, namely, interpatient variability in assessment and perception of pain.

Adult↗

PubMed2002

Frontal plane knee angle affects dynamic postural control strategy during unilateral stance.

PURPOSE: Center of plantar pressure (COPP) location moves toward the forefoot as ankle plantar flexor muscles attempt to maintain postural control during single leg stance. This study evaluated relationships between frontal plane tibiofemoral joint angulation during relaxed bilateral stance and mean COPP locations during vision-denied single leg stance at 20 degrees knee flexion. METHODS: Fifty-six nonimpaired athletes (29 female, 27 male) were evaluated for frontal plane tibiofemoral joint angulation and standing foot angle by using two-dimensional videography (30 Hz). Mean anterior-posterior and mediolateral COPP locations were assessed during single leg stance on a mat (25 Hz, 15 s). One-way ANOVA and Tukey HSD tests evaluated group differences (P < or = 0.05) based on frontal plane tibiofemoral joint angulation. RESULTS: Group 1 (genu varus or genu valgus < 5 degrees ) displayed a mean anterior-posterior COPP location of 54.2 +/- 6% from the (0,0) coordinate starting point at the anterolateral foot (10.3 +/- 2 cm from the posterior sensor edge). Group 2 (genu varus angulation > or = 5 degrees ) and group 3 subjects (genu valgus angulation > or = 5 degrees ) displayed mean anterior-posterior COPP locations of 60.6 +/- 8% and 60.7 +/- 7% (8.8 +/- 2 cm and 8.7 +/- 2 cm from the posterior sensor edges), respectively. Group 2 (12.5 +/- 3 N x kg(-1)) and group 3 (12.4 +/- 3.1 N x kg(-1)) subjects also displayed greater mean plantar force magnitude/body weight than group 1 (10.3 +/- 2 N x kg(-1)) subjects. Mean ankle plantar flexor moment magnitudes did not differ between groups. CONCLUSIONS: Rearfoot directed mean anterior-posterior COPP locations and greater plantar force magnitudes/body weight suggests that subjects with genu varus or genu valgus relied more on the subtalar and midtarsal joint control function of the ankle plantar flexor muscle group for lower extremity dynamic postural control.

Adolescent↗

PubMed2002

Endoscopic resection of a nasal septal chondrosarcoma: first report of a case.

Advances in endoscopic sinus surgery technique and technology have provided the otolaryngologist with a wide array of surgical options for the management of nasal and paranasal sinus diseases that were once limited to procedures requiring invasive surgery. We describe the case of a patient with a chondrosarcoma of the posterior nasal septum that was resected endoscopically. There have been fewer than 30 reports in the English-language literature of chondrosarcomas arising at this location, and the reported approaches to surgical excision in these case involved craniofacial procedures, facial degloving, facial splitting, and maxillectomy techniques. Until now, no case of endoscopic removal has been reported.

Aged↗

PubMedDate not supplied

Interferon beta-1a for brain tissue loss in patients at presentation with syndromes suggestive of multiple sclerosis: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: In patients who present with clinically isolated syndromes suggestive of multiple sclerosis, interferon beta-1a is effective in delaying evolution to clinically definite disease and in reducing MRI-measured disease activity. We aimed to assess whether this drug can also reduce the rate of brain volume decrease in such patients enrolled in the ETOMS (early treatment of multiple sclerosis) trial. METHODS: MRI data for brain volume measurements at baseline, month 12, and month 24 were available from 131, 111, and 112 patients assigned treatment (22 microg interferon beta-1a), and 132, 98, and 99 patients assigned placebo respectively. Normalised brain parenchymal volume (NBV) at baseline and percentage brain volume changes (PBVC) were measured with a fully-automated segmentation technique. The primary endpoint was conversion to clinically definite multiple sclerosis due to clinical relapse. Analysis was by intention to treat. FINDINGS: 41 (31%) of 131 patients on interferon beta-1a and 62 (47%) of 132 on placebo converted to clinically definite multiple sclerosis (odds ratio 0.52 [95% CI 0.31-0.86], p=0.0115). Mean PBVC for patients on placebo was -0.83% during the first year, -0.67% during the second year, and -1.68% during the entire study period. Respective values for treated patients were -0.62%, -0.61%, and -1.18%. The changes in brain volume were significant in both groups at all timepoints. A significant treatment effect was detected for month 24 versus baseline values (p=0.0031). The number of new T2 lesions formed during the first year correlated weakly with PBVC during the second year. INTERPRETATION: Early treatment with interferon beta-1a is effective in reducing conversion to clinically definite multiple sclerosis and in slowing progressive loss of brain tissue in patients with clinically isolated syndromes. The modest correlation between new lesion formation and brain volume decrease suggests that inflammatory and neurodegenerative processes are, at least partly, dissociated from the earliest clinical stage of multiple sclerosis onwards.

Adolescent↗

PubMedDate not supplied

What's "unstable" in unstable angina?

The role of emotional distress (e.g., anger, depression, and anxiety) in anginal chest discomfort (ACD) may have been underestimated. The authors review the empirical studies in this area, which are inconsistent with the standard theory on the ischemia-angina relationship; summarize the substantial evidence indicating a strong and consistent cross-sectional/prospective epidemiological association of emotional distress and ischemia/ACD; review the distress-targeted, interventional evidence confirming a causal relationship (i.e., reduced chest discomfort and health system utilization), thus confirming clinical utility of such interventions; and explore the possible mechanisms that might account for the relationship between emotional distress and chest discomfort. Substantial clinical benefit may be achieved by aggressively detecting and treating emotional distress in ACD patients.

Affect↗