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Biomedical subjects

D C Tong

Publications and source records attributed to D C Tong.

At least 37 records · Page 2Linked to original sources
PubMed2000

The great auricular nerve: a case report and review of anatomy.

This report reviews the pertinent anatomy of the great auricular nerve. The clinical significance of this nerve is apparent in some patients undergoing lower third molar surgery under local anaesthesia. The great auricular nerve arises from the cervical plexus and overlaps territory from the trigeminal nerve supplying sensory innervation to the angle of the mandible. In certain instances, a separate infiltration may be needed to achieve total analgesia of the region.

Adult↗
PubMed1999

Evaluation of early reperfusion and i.v. tPA therapy using diffusion- and perfusion-weighted MRI.

OBJECTIVE: To characterize the effects of recombinant tissue plasminogen activator (rt-PA) therapy and early reperfusion on diffusion-weighted (DWI) and perfusion-weighted imaging (PWI) changes observed following acute ischemic injury. METHODS: Twelve patients were evaluated prospectively using echo planar DWI and bolus tracking PWI. Six patients received i.v. rt-PA 0.9 mg/kg and were compared with six patients who did not. Patients receiving rt-PA were initially imaged (T1) 3 to 5 hours postictus (mean, 4 hours 20 minutes) whereas those not treated with tissue plasminogen activator (tPA) were imaged 4 to 7 hours postictus (mean, 5 hours, 25 minutes). Follow-up imaging was performed 3 to 6 hours (T2), 24 to 36 hours (T3), 5 to 7 days (T4), and 30 days (T5) after the first scan in all patients. Lesion volumes were measured on both DWI and time-to-peak maps constructed from PW images. RESULTS: PWI was performed successfully at T1 and T3 in 11 of 12 patients. In the group that received i.v. tPA, initial PWI volumes were less than DWI volumes in five of six patients (83%), whereas only one of five patients (20%) not receiving tPA had PWI < DWI volume (p = 0.08). PWI normalized by 24 to 36 hours (T3) in 6 of 11 patients (early reperfusers), with 5 of 6 of these early reperfusers having received tPA. The aggregate apparent diffusion coefficient (ADC) values for the early reperfusers were consistently higher at T2 (p = 0.04), T3 (p = 0.002), and T4 (p = 0.0005). Five of six patients with early reperfusion demonstrated regions of elevated ADC within the ischemic zone (mean ipsilateral ADC/contralateral ADC, 1.46 +/- 0.19) by 24 to 36 hours, whereas none of the nonearly reperfusers showed these regions of elevated ADC (p = 0.015). CONCLUSION: Early reperfusion is seen more frequently with i.v. tPA therapy. In addition, the study showed that ADC may undergo early increases that are tied closely to reperfusion, and marked ADC heterogeneity may exist within the same lesion. Early reperfusion is seen more frequently with i.v. tPA therapy.

Aged↗
PubMed1999

Longitudinal magnetic resonance imaging study of perfusion and diffusion in stroke: evolution of lesion volume and correlation with clinical outcome.

A prospective longitudinal diffusion-weighted and perfusion-weighted magnetic resonance imaging (DWI/PWI) study of stroke patients (n = 21) at five distinct time points was performed to evaluate lesion evolution and to assess whether DWI and PWI can accurately and objectively demonstrate the degree of ischemia-induced deficits within hours after stroke onset. Patients were scanned first within 7 hours of symptom onset and then subsequently at 3 to 6 hours, 24 to 36 hours, 5 to 7 days, and 30 days after the initial scan. Lesion evolution was dynamic during the first month after stroke. Most patients (18 of 19, 95%) showed increased lesion volume over the first week and then decreased at 1 month relative to 1 week (12 of 14, 86%). Overall, lesion growth appeared to depend on the degree of mismatch between diffusion and perfusion at the initial scan. Abnormal volumes on the acute DWI and PWI (<7 hours) correlated well with initial National Institutes of Health (NIH) stroke scale scores, outcome NIH stroke scale scores, and final lesion volume. DWI and PWI can provide an early measure of metabolic and hemodynamic insufficiency, and thus can improve our understanding of the evolution and outcome after acute ischemic stroke.

Aged↗
PubMed1999

Intra-arterial rtPA treatment of stroke assessed by diffusion- and perfusion-weighted MRI.

BACKGROUND: Diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) are new techniques that can be used for the evaluation of acute ischemic stroke. However, their potential role in the management of patients treated with recombinant tissue plasminogen activator (rtPA) has yet to be determined. CASE DESCRIPTION: The authors present the case of a 73-year-old man who was treated with intra-arterial rtPA, and they compare findings on DWI and PWI scans with angiography. PWI revealed decreased cerebral perfusion corresponding to an area that was not successfully recanalized, but revealed no abnormality in regions in which blood flow was restored. DWI was unremarkable in the region that was reperfused early (3 hours) but revealed hyperintensity in an area that was reperfused 3. 5 hours after symptom onset and in the area that was not reperfused. CONCLUSIONS: Findings on PWI correlated well with angiography, and DWI detected injured tissue in the hyperacute stage, whereas conventional MRI findings were negative. This suggests that these techniques may be useful to noninvasively evaluate the success of thrombolytic therapy.

Aged↗
PubMed1999

Antithrombotic management of atrial fibrillation for stroke prevention in older people.

Atrial fibrillation (AF) is a common cardiac condition in the elderly population. The primary concern in individuals with AF is the risk of stroke. The management of AF for stroke prevention requires an understanding of the relative risks and benefits of antithrombotic therapy. Numerous randomized clinical trials have improved tremendously our understanding of the relative merits of anticoagulation and aspirin, and indicate that anticoagulation is the appropriate treatment for the majority of individuals with AF. In patients who have contraindications to anticoagulation, aspirin is recommended.

Aged↗
PubMed1999

Atypical migration of an impacted lower third molar.

This report describes the atypical migration of an impacted lower third molar tooth in a 42-year-old woman. Serial radiographs showed that, over a period of 13 years, the tooth migrated from its original disto-angular position posterior to and beneath the roots of the adjacent second molar to a more horizontal position beneath the roots of the first permanent molar. The tooth was surgically removed under general anaesthesia, with biopsy and curettage of soft tissue found in the bone posterior to the tooth along the path of migration. This pattern of tooth movement is highly unusual in an adult patient.

Adult↗
PubMed1998

Correlation of perfusion- and diffusion-weighted MRI with NIHSS score in acute (<6.5 hour) ischemic stroke.

BACKGROUND: Diffusion-weighted (DWI) and perfusion-weighted (PWI) MRI are powerful new techniques for the assessment of acute cerebral ischemia. However, quantitative data comparing the severity of clinical neurologic deficit with the results of DWI or PWI in the earliest phases of stroke are scarce. Such information is vital if MRI is potentially to be used as an objective adjunctive measure of stroke severity and outcome. OBJECTIVE: The authors compared initial DWI and PWI lesion volumes with subsequent 24-hour neurologic deficit as determined by National Institutes of Health Stroke Scale (NIHSS) score in acute stroke patients. Initial DWI and PWI volumes were also compared with T2W MRI lesion volume at 1 week to assess the accuracy of these MRI techniques for the detection of acute cerebral ischemia. METHODS: Patients with stroke underwent MRI scanning within 6.5 hours of symptom onset. Lesion volumes on DWI and PWI were measured and compared with 24-hour NIHSS score. Initial DWI and PWI volumes were also compared with T2W lesion size at 1 week. RESULTS: There was a high correlation between 24-hour NIHSS score and lesion volume as determined by PWI (r = 0.96, p < 0.001) or DWI (r = 0.67, p = 0.03). A similar high correlation was seen between T2W stroke size at 7 days and initial DWI and PWI lesion size (r = 0.99, p < 0.00001). CONCLUSIONS: Both DWI and PWI are highly correlated with severity of neurologic deficit by 24-hour NIHSS score. These findings may have substantial implications for the use of MRI scanning in the assessment and management of acute stroke patients.

Acute Disease↗
PubMed1998

Progressive facial hemiatrophy: abnormality of intracranial vasculature.

Progressive facial hemiatrophy (PFH) or Parry-Romberg syndrome is associated with ipsilateral brain lesions and neurologic symptoms. We describe a 35-year-old man with PFH and frequent hemiplegic migraine. On cerebral angiography, reversible vessel caliber changes were seen within the symptomatic hemisphere. An abnormality of the intracranial vasculature may be present in some patients with PFH and neurologic manifestations.

Adult↗
PubMed1998

Angiographically defined primary angiitis of the CNS: is it really benign?

BACKGROUND: Primary angiitis of the CNS (PACNS) is a diagnostically challenging disorder. In patients whose diagnosis is ascertained solely by cerebral angiography without histologic verification, a benign monophasic clinical course with favorable response to a brief course of immunosuppressive therapy is often reported. METHODS: We performed a retrospective review of patients with PACNS seen at the Stanford Stroke Center. RESULTS: Patients were followed for a median of 27.5 months. Acute focal deficits (9 of 10) and headache (3 of 10) were the most frequent presenting symptoms. Significant recurrent neurologic symptoms occurred in 5 of 10 patients before the initiation of immunosuppressive treatment. Three of six patients had recurrent symptoms during prednisone therapy alone, whereas only one of seven patients had recurrent symptoms while receiving combination immunosuppressive therapy. None had recurrent stroke during immunosuppressive treatment. Dynamic arterial changes were seen in four of five patients who underwent follow-up angiography that often, but not always, correlated with disease activity. CONCLUSIONS: Patients with angiographically defined PACNS frequently did not have a benign outcome or monophasic course. Repeat angiography was useful in supporting the diagnosis of PACNS, but did not always correlate with disease activity. A prospective multicenter collaborative effort is required to better define the clinical course and optimal treatment of PACNS.

Adult↗
PubMed1997

Diffusion-weighted MRI in transient global amnesia precipitated by cerebral angiography.

BACKGROUND: Transient global amnesia is a well-described complication of cerebral angiography. Speculation about the pathophysiology exists but is as yet unsubstantiated. Diffusion-weighted MRI is a new imaging technique that is very sensitive in detecting acute ischemia. Its use in the evaluation of transient amnesia precipitated by cerebral angiography has not previously been reported. CASE DESCRIPTION: A 44-year-old man underwent posterior circulation cerebral angiography for the investigation of episodic vertigo. Shortly after completion of the procedure, he was noted to have symptoms of transient global amnesia. Diffusion-weighted MRI at 6 and 44 hours after the procedure demonstrated increased signal in the right hippocampus and other areas within the posterior circulation bilaterally consistent with ischemia from emboli. Abnormalities on conventional MRI images performed at the same time points were noted only in retrospect. A follow-up MRI at 2 months was normal. CONCLUSIONS: Ischemia from cerebral emboli may cause transient global amnesia precipitated by cerebral angiography. Diffusion-weighted MRI may be useful in defining the pathophysiology.

Adult↗
PubMed1997

Intravenous thrombolytic therapy in acute stroke.

The article reviews the experimental basis of thrombolytic therapy, and summarizes the results of the recent trials of thrombolysis. Five large clinical trails have evaluated intravenous thrombolytic therapy for the treatment of hyperacute (< 6 h) stroke. Three of these studies were negative, one was equivocal, and one was strongly positive. The failure of demonstrate efficacy definitively in four of these trials may be related to a number of methodological factors, including the type and dose of drug administered, the timing of drug administered, and the method of patient selection for treatment. The NINDS recombinant tissue plasminogen activator (rt-PA) study showed that thrombolytic therapy can be of substantial benefit when administered within 3 h of stroke onset using strict patient selection criteria and rt-PA is now FDA approved for treatment of acute stroke. However, the risk of clinically significant bleeding is elevated. To achieve the favorable risk/benefit ratio demonstrated in the NINDS trial, patients must be screened by experienced clinicians for contraindications to thrombolysis and the acute computerized tomography (CT) brain scan must be carefully evaluated for radiographic features that increase the risk of cerebral hemorrhage. Guidelines for the use of rt-PA are provided, as well as insights into future thrombolytic treatment strategies.

Acute Disease↗
PubMed1996

Unusual presentations of injuries associated with the mandibular condyle in children.

Condylar fractures are sustained commonly by children and are readily diagnosed in the main. Three case histories serve to illustrate the intricate anatomy of the area and how damage to it can produce unusual signs and symptoms which can mislead the unwary. Supplemental images, in particular coronal CTs, can be instrumental in arriving at the correct diagnosis and treatment.

Accidental Falls↗
PubMed1995

Transcranial Doppler-detected microemboli in patients with acute stroke.

BACKGROUND AND PURPOSE: Transcranial Doppler sonography (TCD) has been used to detect microembolic signals in a variety of clinical situations. We studied the prevalence of TCD-detected microemboli in 38 acute stroke patients. METHODS: Consecutive patients with acute anterior circulation stroke were stratified into high-risk (group 1), medium-risk (group 2), and low-risk (group 3) groups based on their risk factors for cerebral embolism. RESULTS: Microemboli were detected in 11% of patients. They were present in 17% of group 1, 10% of group 2, and 0% of group 3 patients. Emboli were present in patients with mechanical prosthetic valves, carotid stenosis (> 70%), and mitral valve strands with a patent foramen ovale. Patients with microemboli more frequently had a history of cerebral ischemia compared with patients without microemboli (P < .05). They also more frequently had recent (< 3 months) symptoms compared with patients without microemboli (P < .05). In patients with a cardiac source of embolization, the number of microemboli detected was directly proportional to the acuity of previous symptoms. CONCLUSIONS: These data suggest that TCD-detected microemboli are associated with an increased prevalence of prior cerebrovascular ischemia. The presence of TCD-detected microemboli could be a risk factor for cerebrovascular ischemia.

Acute Disease↗
PubMed1994

Incidence of transcranial Doppler-detected cerebral microemboli in patients referred for echocardiography.

BACKGROUND AND PURPOSE: Transcranial Doppler can detect cerebral microemboli. These emboli may be a risk factor for embolic stroke. We studied the prevalence of microemboli in patients referred for echocardiography. METHODS: Forty-two patients were evaluated. Patients were studied with continuous monitoring over one middle cerebral artery for 30 minutes, and the number of microemboli was recorded. Patients were divided into three groups, those with prosthetic heart valves (group A, n = 15), atrial fibrillation (group B, n = 14), and no major cardiac risk factor (group C, n = 14). RESULTS: Seventeen percent (7 of 42) of all patients had microemboli. In group A, 5 of 15 (33%) had microemboli. In group B, 2 of 13 (15%) patients had microemboli. Twenty-five percent (7 of 28) of patients in groups A and B combined (A+B) had microemboli. No patients (0 of 14) in group C had microemboli. Groups A and A+B had significantly more emboli than group C (P < .05). Prosthetic heart valve patients with emboli more commonly had a history of prior stroke than valve patients without emboli (3 of 5 versus 2 of 10). The number of emboli seen per 30-minute monitoring session was greater in patients with a prior history of stroke than in patients without (10 microemboli versus 3). CONCLUSIONS: Microemboli can be found in a significant percentage of selected patients referred for echocardiography. The prevalence of microembolism is greater in patients with a known high risk of embolization (eg, prosthetic valves) and less in patients with a lower risk of embolization (eg, atrial fibrillation). These microemboli may be associated with an increased prevalence of previous stroke in patients with prosthetic valves.

Aged↗
PubMed1994

Periodontal complications following orthognathic surgery and genioplasty in a 19-year-old: a case report.

Bimaxillary osteotomies and a sliding genioplasty were performed to correct mandibular micrognathia and maxillary vertical hyperplasia in a 19-year-old white male with a Class II, division 1 malocclusion and anterior open bite. At a follow-up appointment with the orthodontist 4 weeks after the surgical procedure, the mandibular anterior teeth showed severe gingival recession, exposing labial root surfaces on the mandibular central incisors. Grafting procedures were able to restore labial soft tissue on the affected teeth. It is suggested that wound healing contraction of gingival tissue in the area of the incision for the genioplasty caused this complication.

Adult↗
PubMedDate not supplied

H2O2 oxidative damage in cultured oral epithelial cells: the effect of short-term vitamin C exposure.

Smoking is the main etiology of oral cancer and generates oxygen free radicals in the oral cavity. Free radicals have been implicated in apoptosis and in DNA damage inducing alteration of the cell cycle. The antioxidant vitamin C (VC) is reported to inhibit damage induced by free radicals. We exposed cultures of normal human oral epithelial cells to hydrogen peroxide (H2O2) in the presence and absence of VC. Generation of hydroxyl radicals was measured by electron paramagnetic resonance (EPR), cell cycle alterations by flow cytometry, cell death by SYTO 11 and morphology by organotypic culture. Human primary cell culture was given four treatments - control, VC alone, H2O2 alone and VC followed by H2O2. Cell cycle analysis indicated cultures treated with H2O2 had fewer cells in G1 phase (26%) and higher number of cells in S phase (44%) compared to the control (G1 70% & S 14%). Cell cycle of 48 hour VC treatment followed by H2O2 was similar to H2O2 alone. SYTO 11 showed 22% cell death when treated with H2O2 alone compared to 9% of normal control. By organotypic culture H2O2 alone induced a two-fold cell proliferation, loss of maturation, nuclear hyperchromatism and nuclear crowding. Our results suggest that H2O2 is capable of altering the cell cycle and morphology of cultured normal human oral epithelial cells. Forty-eight hour exposure to Vitamin C does not prevent the cell cycle changes caused by hydroxyl radicals.

Ascorbic Acid↗