Biomedical subjects

D C Tong

Publications and source records attributed to D C Tong.

At least 19 recordsLinked to original sources

PubMed2005

Do the Brain Attack Coalition's criteria for stroke centers improve care for ischemic stroke?

BACKGROUND: In 2000, the Brain Attack Coalition (BAC) recommended 11 major criteria for the establishment of primary stroke centers. The BAC relied heavily on expert opinion because evidence supporting the criteria was sparse. OBJECTIVE: To assess primary stroke center elements, based on the criteria proposed by the BAC, with a questionnaire at 34 academic medical centers. METHODS: Patient characteristics and outcomes were collected for all patients (n = 16,853) admitted with ischemic stroke to each hospital from 1999 to 2001. Stroke center elements were evaluated as predictors of treatment with tissue plasminogen activator (tPA) and outcomes after adjustment for patient characteristics. RESULTS: The in-hospital mortality rate was 6.3% (n = 1,062), and 2.4% (n = 399) of patients received tPA. None of the 11 major stroke center elements was associated with decreased in-hospital mortality or increased frequency of discharge home. However, four elements predicted increased tPA use, including written care protocols, integrated emergency medical services, organized emergency departments, and continuing medical/public education in stroke (each odds ratio [OR] > 2.0, p < 0.05). Use of tPA also tended to be greater at centers with an acute stroke team, a stroke unit, or rapid neuroimaging (each OR > 2.0, p < 0.10). Institutions with a greater number of major stroke center elements used tPA more frequently. CONCLUSIONS: Of the 11 stroke center elements recommended by the BAC, 7 were associated with increased tPA use. Institutions with a greater number of these seven features used tPA more often, suggesting these key elements may be most important for primary stroke center designation, at least in terms of identifying centers that deliver IV tPA frequently.

Academic Medical Centers↗

PubMed2003

Efficacy of IV tissue plasminogen activator in acute stroke: does stroke subtype really matter?

BACKGROUND: The National Institute of Neurological Disorders and Stroke (NINDS) trial reported that stroke subtype (e.g., large-artery atherothrombosis, cardioembolism, and lacunae) does not affect response to IV thrombolytic treatment. However, these conclusions were based upon stroke subtypes determined prior to extensive diagnostic evaluation. Because such initial diagnoses are frequently inaccurate, the efficacy of IV recombinant tissue plasminogen activator (rt-PA) based upon verified specific stroke subtypes remains uncertain. METHODS: The records of consecutive acute stroke patients treated with IV rt-PA at two regional stroke centers were retrospectively reviewed. The final stroke subtype after complete diagnostic evaluation was determined. The relationship between final stroke subtype and response to thrombolytic therapy was then investigated and compared with the results reported in the NINDS trial. RESULTS: Ninety consecutive patients were studied. After adjusting for baseline NIH Stroke Scale scores, no significant difference in final outcome based on confirmed stroke mechanism was identified. CONCLUSIONS: These data are consistent with those of the NINDS trial that reported that the efficacy of IV thrombolysis within the 3-hour time window is similar between different stroke subtypes. Based upon these data, allocating treatment of stroke patients with IV rt-PA based upon presumed stroke mechanism may be unnecessary. Such testing may result in time delays that could compromise the efficacy of treatment.

Academic Medical Centers↗

PubMed2002

Endodontic implications of the maxillary sinus: a review.

The anatomical and clinical significance of the maxillary sinus in relation to conventional and surgical endodontic therapy is considered. The discussion includes a review on the development, anatomy and physiology of the maxillary sinus, the diagnostic evaluation of the sinus and the differential diagnosis of sinusitis. Endodontic implications of the maxillary sinus include extension of periapical infections into the sinus, the introduction of endodontic instruments and materials beyond the apices of teeth in close proximity to the sinus and the risks and complications associated with endodontic surgery.

Analgesics↗

PubMed2002

Concurrent oral lichen planus and primary sclerosing cholangitis.

Four patients with concomitant oral lichen planus (OLP) and primary sclerosing cholangitis (PSC) are presented. Associations have been made between OLP and chronic liver disease, namely hepatitis C and primary biliary cirrhosis, but the aetiology and commonality between the diseases has yet to be confirmed. An immunological link is currently favoured. PSC may be a further association with OLP, possibly involving the immune system.

Adult↗

PubMed2002

Serious facial fractures in New Zealand from 1979 to 1998.

We present data on the incidence, aetiology, age, sex and ethnic distribution of facial fractures in New Zealand for the 20-year period from 1979-1998. Most facial fractures (78.9%) occurred in males with a rate of 65.5/100,000, person-years compared with 21% in females with an incidence of 17/100,000. While the injury rate peaked in males between the ages of 20-24 years (200/100,000), it peaked between 15-19 years (34.7/100,000) in females. The most common causes of facial fracture in both genders were assault (14/100,000) and being unintentionally struck by an object or person (9.5/100,000) which is consistent with similar data from South Africa and the USA. The rates of fracture in Maori (68.1/100,000) were approximately twice those of Pacific Islanders (37/100,000) or other ethnic groups (34.2/100,000).

Accidents, Traffic↗

PubMed2001

Displaced polishing discs: two case reports.

Routine dental treatment is not without its hazards. Two cases of trauma to the buccal soft tissues caused by displaced polishing discs are reported and suggestions made regarding the long-term use and maintenance of dental instruments.

Adipose Tissue↗

PubMed2001

Prediction of hemorrhagic transformation following acute stroke: role of diffusion- and perfusion-weighted magnetic resonance imaging.

BACKGROUND: Acute diffusion-weighted (DWI) and perfusion-weighted (PWI) magnetic resonance imaging (MRI) findings may correlate with secondary hemorrhagic transformation (HT) risk in patients with stroke. This information could be of value, particularly in individuals being considered for thrombolytic therapy. OBJECTIVE: To determine the relationship between DWI and PWI findings and the risk of secondary HT in patients with acute stroke. DESIGN: Retrospective case series. SETTING: Academic medical center. PATIENTS: Twenty-seven patients with acute stroke capable of being evaluated with DWI/PWI 8 hours or less after symptom onset. MAIN OUTCOME MEASURES: Apparent diffusion coefficient values, perfusion delay measurements, and subsequent MRI or computed tomographic scans detected HT. RESULTS: The mean +/- SD apparent diffusion coefficient of ischemic regions that experienced HT was significantly lower than the overall mean +/- SD apparent diffusion coefficient of all ischemic areas analyzed (0.510 +/- 0.140 x 10(-3) mm(2)/s vs 623 +/- 0.113 x 10(-3) mm(2)/s; P =.004). This difference remained significant when comparing the HT-destined ischemic areas with the non-HT-destined areas within the same ischemic lesion (P =.02). Patients receiving recombinant tissue-type plasminogen activator (rt-PA) experienced HT significantly earlier than patients not receiving rt-PA (P =.002). Moreover, a persistent perfusion deficit in the area of subsequent hemorrhage at 3 to 6 hours after the initial MRI scan was identified in significantly more patients who experienced HT than in those who did not (83% vs 30%; P =.03). CONCLUSION: Both DWI and PWI scans detect abnormalities that are associated with HT. These findings support a role for MRI in identifying patients who are at increased risk for secondary HT following acute ischemic stroke.

Acute Disease↗

PubMed2001

Evolution of cerebral infarct volume assessed by diffusion-weighted magnetic resonance imaging.

BACKGROUND: Knowledge of the natural evolution of ischemic brain lesions may be a crucial aspect in the assessment of future stroke therapies. OBJECTIVE: To establish daily changes of ischemic cerebral lesion volume using diffusion-weighted magnetic resonance imaging. DESIGN: Prospective cohort study. SETTING: Referral center. PATIENTS AND METHODS: Serial magnetic resonance imaging scans were performed in consecutive untreated stroke patients. The baseline scan was obtained within 48 hours after symptom onset; subsequent scans, 12 to 48 hours, 3 to 4 days, 5 to 7 days, and 30 days after baseline. Lesion volumes were measured on each scan by 2 independent observers. MAIN OUTCOME MEASURE: Daily change in lesion volume. RESULTS: A total of 112 magnetic resonance imaging scans were obtained in 24 patients. An early increase in lesion volume was seen in all patients. Maximum lesion volume was reached at a mean of 74 hours. Lesion volumes increased by a mean (+/- SEM) of 21% +/- 12% during day 2 and 10% +/- 12% during day 3. No significant change occurred during day 4. During days 5, 6, and 7, statistically significant mean (+/- SEM) decreases of 6% +/- 8%, 3% +/- 4%, and 4% +/- 5%, respectively, were observed. CONCLUSIONS: Ischemic lesions follow a relatively consistent pattern of growth during the first 3 days and subsequent decrease in size. These data in conjunction with data regarding the evolution of lesion volume during the first 24 hours after symptom onset may be useful in the design of pilot studies of therapies for acute stroke.

Brain↗

PubMed2001

Evolution of apparent diffusion coefficient, diffusion-weighted, and T2-weighted signal intensity of acute stroke.

BACKGROUND AND PURPOSE: Serial study of such MR parameters as diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC), ADC with fluid-attenuated inversion recovery (ADC(FLAIR)), and T2-weighted imaging may provide information on the pathophysiological mechanisms of acute ischemic stroke. Our goals were to establish the natural evolution of MR signal intensity characteristics of acute ischemic lesions and to assess the potential of using specific MR parameters to estimate lesion age. METHODS: Five serial echo-planar DWI studies with and without an inversion recovery pulse were performed in 27 patients with acute stroke. The following lesion characteristics were studied: 1) conventional ADC (ADC(CONV)); 2) ADC(FLAIR); 3) DWI signal intensity (SI(DWI)); 4) T2-weighted signal intensity (SI(T2)), and 5) FLAIR signal intensity (SI(FLAIR)). RESULTS: The lesion ADC(CONV) gradually increased from low values during the first week to pseudonormal during the second week to supranormal thereafter. The lesion ADC(FLAIR) showed the same pattern of evolution but with lower absolute values. A low ADC value indicated, with good sensitivity (88%) and specificity (90%), that a lesion was less than 10 days old. All signal intensities remained high throughout follow-up. SI(DWI) showed no significant change during the first week but decreased thereafter. SI(T2) initially increased, decreased slightly during week 2, and again increased after 14 days. SI(FLAIR) showed the same initial increase as the SI(T2) but remained relatively stable thereafter. CONCLUSION: Our findings further clarify the time course of stroke evolution on MR parameters and indicate that the ADC map may be useful for estimating lesion age. Application of an inversion recovery pulse results in lower, potentially more accurate, absolute ADC values.

Aged↗

PubMed2001

Bite injuries: pathophysiology, forensic analysis, and management.

Bites are serious injuries that constitute 1 percent of all emergency-department visits in the United States of America. Human bite injuries may lead to loss of function, infection, and gross disfigurement, and often are associated with interpersonal and sexual violence, and child abuse. Issues with infection from oral contaminants, tissue damage, and difficult surgical reconstruction make the management of human bite injuries a challenge. The unique nature of teeth and the bite marks they produce are invaluable in forensic pathology. A systematic and detailed evaluation of bite injuries should be performed by a forensic odontologist in order to provide the necessary information for forensic purposes. Management of human bite injuries includes wound debridement, surgery to repair or replace damaged tissue, and long-term antibiotic therapy.

Age Distribution↗

PubMed2000

Yield of diffusion-weighted MRI for detection of potentially relevant findings in stroke patients.

OBJECTIVE: To determine whether diffusion-weighted imaging (DWI) could identify potentially clinically relevant findings in patients presenting more than 6 hours after stroke onset when compared with conventional MRI. METHODS: MRI with both conventional (T2 and proton density images) and echoplanar imaging (DWI and apparent diffusion coefficient maps) was performed 6 to 48 hours after symptom onset (mean, 27 hours) in 40 consecutive patients with acute stroke. All acute lesions were identified first on conventional images, then on DWI, by a neuroradiologist who was provided with the suspected lesion location, based on a neurologist's examination before imaging. Abnormalities were rated as potentially clinically relevant if they were detected only on DWI and 1) confirmed the acute symptomatic lesion to be in a different vascular territory than suspected clinically, 2) revealed multiple lesions in different vascular territories suggestive of a proximal source of embolism, or 3) clarified that a lesion, thought to be acute on conventional imaging, was not acute. RESULTS: The initial clinical impression of lesion localization was incorrect in 12 patients (30%). Clinically significant findings were detected by DWI alone in 19 patients (48%). DWI demonstrated the symptomatic lesion in a different vascular territory than suspected clinically or by conventional MRI in 7 patients (18%) and showed acute lesions in multiple vascular distributions in 5 patients (13%). In 8 patients (20%), DWI clarified that lesions thought to be acute on conventional MRI were actually old. CONCLUSION: In patients imaged 6 to 48 hours after stroke onset, DWI frequently provided potentially clinically relevant findings that were not apparent on conventional MRI.

Adult↗

PubMed2000

Advantages of adding diffusion-weighted magnetic resonance imaging to conventional magnetic resonance imaging for evaluating acute stroke.

BACKGROUND: Accurate localization of acute ischemic lesions in patients with an acute stroke may aid in understanding the etiology of their stroke and may improve the management of these patients. OBJECTIVE: To determine the yield of adding diffusion-weighted magnetic resonance imaging (DWI) to a conventional magnetic resonance imaging (MRI) protocol for acute stroke. DESIGN: A prospective cohort study. SETTING: A referral center. PATIENTS AND METHODS: Fifty-two patients with a clinical diagnosis of acute stroke who presented within 48 hours after symptom onset were included. An MRI scan was obtained within 48 hours after symptom onset. A neuroradiologist (A.M.N.) and a stroke neurologist (G.W.A.) independently identified suspected acute ischemic lesions on MRI sequences in the following order: (1) T2-weighted and proton density-weighted images, (2) fluid-attenuated inversion recovery images, and (3) diffusion-weighted images and apparent diffusion coefficient maps. MAIN OUTCOME MEASURES: Diagnostic yield and interrater reliability for the identification of acute lesions, and confidence and conspicuity ratings of acute lesions for different MRI sequences. RESULTS: Conventional MRI correctly identified at least one acute lesion in 71% (34/48) to 80% (39/49) of patients who had an acute stroke; with the addition of DWI, this percentage increased to 94% (46/49) (P<.001). Conventional MRI showed only moderate sensitivity (50%-60%) and specificity (49%-69%) compared with a "criterion standard." Based on the diffusion-weighted sequence, interrater reliability for identifying acute lesions was moderate for conventional MRI (kappa = 0.5-0.6) and good for DWI (kappa = 0.8). The observers' confidence with which lesions were rated as acute and the lesion conspicuity was significantly (P<.01) higher for DWI than for conventional MRI. CONCLUSION: During the first 48 hours after symptom onset, the addition of DWI to conventional MRI improves the accuracy of identifying acute ischemic brain lesions in patients who experienced a stroke.

Acute Disease↗

PubMed2000

Response of human oral epithelial cells to oxidative damage and the effect of vitamin E.

Smoking and periodontal inflammation are various conditions with the potential to induce oxidative stress and thus DNA damage in the oral cavity. In cellular defense systems, vitamin E is considered the most powerful lipid-soluble antioxidant. To investigate whether oxygen-free radicals alter normal progression of the cell cycle and whether vitamin E prevents this damage, we exposed cultured normal human oral epithelial cells to hydrogen peroxide (H2O2) in the presence or absence of vitamin E. Two primary cell lines were analyzed for the presence of hydroxyl radical, cell cycle distribution and morphology. Each cell line received five treatments: control, ethanol only, vitamin E only, H2O2 only or vitamin E followed by H2O2. Degradation of hydroxyl radicals was detected by electron paramagnetic resonance analysis, cell cycle by flow cytometry and morphology by organotypic technique. Hydroxyl radicals were generated in H2O2-treated cells at an initial concentration, which decreased over a period of time. Cell cycle analysis showed that H2O2-treated cells differed from normal cells in that the percentage of cells in the G1 phase decreased markedly (34.3 vs. 61.2% in control) and the S phase increased (35.5 vs. 15.6% in control). Organotypic cultures treated with H2O2 demonstrated nuclear hyperchromatism, loss of maturation and prominent nucleoli, features consistent with premalignant epithelial transformation. In conclusion, our data suggest that H2O2 produced hydroxyl radicals and altered the cell cycle. Also, vitamin E may have the potential to reduce oxidative damage caused by hydroxyl radicals.

Epithelial Cells↗

PubMed2000

Effect of brief exposure to mitomycin C on cultured human nasal mucosa fibroblasts.

PURPOSE: To observe the effect of mitomycin C (MMC) on cultured human nasal mucosa fibroblasts. METHODS: Cultured human nasal mucosa fibroblasts were exposed to MMC (0.1-0.4 mg/ml) for 1 to 5 minutes. The viability of the fibroblasts was determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay; DNA fragmentation (apoptosis) by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL); apoptotic percentage by flow cytometry; and morphology by light microscopy. RESULTS: A portion of the fibroblasts survived the mitomycin treatment and showed evidence of regrowth within 2 to 3 days. These cells reached confluence in 5 to 7 days. The inhibition rates by MTT assay of 0.4 mg/ml MMC for 5-minute exposures was 31.3%. Dose-response effect was noted with the lower concentrations and shorter exposure times where the inhibition rates were lower (but not significantly so). DNA fragmentation was observed in fibroblasts 24 hours after MMC exposure (0.4 mg/ml) for 5 minutes compared with normal control. The apoptotic rate of fibroblasts treated by 0.4 mg/ml MMC was significantly higher than the control (p < 0.05). CONCLUSIONS: Short MMC exposure times have a variable cytotoxic effect and inhibit proliferation of cultured nasal mucosa fibroblasts. MMC also can induce apoptosis with a 5-minute exposure time. Therefore, it is possible that MMC has a complex effect in dacryocystorhinostomy.

Alkylating Agents↗

PubMed2000

Diffusion and perfusion magnetic resonance imaging for the evaluation of acute stroke: potential use in guiding thrombolytic therapy.

Recent data indicate that diffusion/perfusion weighted imaging could eventually play a significant role in acute stroke management, particularly in determining the suitability of acute stroke patients for thrombolytic therapy. The evidence supporting these uses is reviewed, and the future role of diffusion and perfusion weighted imaging in acute stroke management is discussed.

Acute Disease↗

PubMed2000

Relationship between apparent diffusion coefficient and subsequent hemorrhagic transformation following acute ischemic stroke.

BACKGROUND AND PURPOSE: A method for identifying patients at increased risk for developing secondary hemorrhagic transformation (HT) after acute ischemic stroke could be of significant value, particularly in patients being considered for thrombolytic therapy. We hypothesized that diffusion-weighted MRI might aid in the identification of such patients. METHODS: We retrospectively analyzed 17 patients with ischemic stroke who received diffusion-weighted MRI within 8 hours of symptom onset and who also received follow-up neuroimaging within 1 week of initial scan. The apparent diffusion coefficient (ADC) for each pixel in the whole ischemic area was calculated, generating a histogram of values. Areas subsequently experiencing HT were then compared with areas not experiencing HT to determine the relationship between ADC and subsequent HT. RESULTS: A significantly greater percentage of pixels possessed lower ADCs (</=550x10(-)(6) mm(2)/s) in HT lesions compared with non-HT lesions (47% versus 19%; P:<0.001). Moreover, >40% of the pixels possessed values </=550x10(-)(6) mm(2)/s in all lesions experiencing secondary HT, compared with <31% of the pixels in the non-HT-destined lesions. CONCLUSIONS: HT-destined stroke regions possess a significantly great percentage of low ADC values than non-HT-destined regions. Early measurement of ADC values may be a useful tool for assessing secondary HT risk.

Aged↗

PubMed2000

Cervene (Nalmefene) in acute ischemic stroke : final results of a phase III efficacy study. The Cervene Stroke Study Investigators.

BACKGROUND AND PURPOSE: The goals of the present study were to assess the efficacy and safety of nalmefene (Cervene) in patients with acute (< or =6 hours) ischemic stroke and to investigate the safety of combined recombinant tissue plasminogen activator and nalmefene in a separate subset of patients. Nalmefene, an opioid antagonist with relative kappa receptor selectivity, has shown neuroprotective effects in multiple experimental central nervous system injury and ischemic models. Results from an earlier phase II study in patients with acute ischemic stroke suggested that nalmefene was safe and tolerable and may be effective for patients <70 years old. METHODS: This investigation was a phase III, placebo-controlled, double-blind, randomized study of a 24-hour infusion of nalmefene. Patients with acute ischemic stroke who had an onset of symptoms within 6 hours and a baseline score of > or =4 on the NIH Stroke Scale were randomized to receive either 60 mg nalmefene administered as a 10-mg bolus over 15 minutes and then a 50-mg infusion over 23.75 hours or placebo. The primary efficacy outcome was the proportion of patients achieving a score of > or =60 on the Barthel Index and a rating of "moderate disability" or better on the Glasgow Outcome Scale at 12 weeks. Assessments were performed at baseline (predose), hours 12 and 24, days 2 and 7, and week 12. RESULTS: A total of 368 patients were randomized at 42 centers, including 32 patients treated with recombinant tissue plasminogen activator and study drug. Nalmefene was well tolerated. Overall, there was no significant difference in 3-month functional outcome for nalmefene treatment compared with placebo on any of the planned analyses. A prospective secondary analysis also failed to find a treatment effect in patients <70 years old. CONCLUSIONS: Although nalmefene appears to be safe and well tolerated, this study failed to find any treatment benefit in stroke patients treated within 6 hours.

Acute Disease↗

PubMed2000

Antibiotic prophylaxis in dentistry: a review and practice recommendations.

BACKGROUND: The American Heart Association, or AHA, and the American Dental Association recently changed their recommended protocols for antibiotic prophylaxis against bacterial endocarditis. A new recommendation also has been issued by the ADA and the American Academy of Orthopaedic Surgeons, or AAOS, against routine antibiotic prophylaxis in patients with prosthetic joint replacements. These changes reflect increasing scientific evidence and professional experience in opposition to widespread use of antibiotic prophylaxis in these specific situations and others faced in dentistry. METHODS: The authors reviewed the medical and dental literature for scientific evidence regarding the use of antibiotics to prevent local and systemic infections associated with dental treatment. Situations commonly considered by dentists for potential use of prophylactic antibiotics were reviewed to determine current evidence with regard to use of antimicrobial agents. This included prevention of distant spread of oral organisms to susceptible sites elsewhere in the body and the reduction of local infections associated with oral procedures. RESULTS: There are relatively few situations in which antibiotic prophylaxis is indicated. Aside from the clearly defined instances of endocarditis and late prosthetic joint infections, there is no consensus among experts on the need for prophylaxis. There is wide variation in recommended protocols, but little scientific basis for the recommendations. The emerging trend seems to be to avoid the prophylactic use of antibiotics in conjunction with dental treatment unless there is a clear indication. CONCLUSIONS: Aside from the specific situations described, there is little or no scientific basis for the use of antibiotic prophylaxis in dentistry. The risk of inappropriate used of antibiotics and widespread antibiotic resistance appear to be far more important than any possible perceived benefit. CLINICAL IMPLICATIONS: Dentists are wise to use antibiotic prophylaxis in only those specific situations in which there is a valid scientific basis for it. Whenever possible, dentists should follow the standard protocols recommended by the ADA, AHA or AAOS.

American Dental Association↗