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Biomedical subjects

I Ng

Publications and source records attributed to I Ng.

At least 19 recordsLinked to original sources
PubMed2006

Temporal changes in cerebral tissue oxygenation with cerebrovascular pressure reactivity in severe traumatic brain injury.

OBJECTIVE: To investigate the temporal relationship between cerebrovascular pressure reactivity and brain tissue oxygenation in patients with severe head injury. METHODS: In 40 patients, brain tissue oxygenation and intracranial pressure were monitored. Time-averaged values for intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP) and brain tissue oxygenation (PtiO2) were computed. The pressure reactivity index (PRx) was calculated. The mean values of the variables were obtained at the 6-h and 72-h post-injury time points, and the difference between the two time points for each of the variables was denoted as delta (delta). RESULTS: Of the 40 patients, 32 were survivors and 8 were non-survivors. Statistically significant differences were present between these two groups with regard to deltaMAP (p = 0.013), ICP at 6 h (p = 0.027), CPP at 72 h (p = 0.018), deltaCPP (p = 0.033), PRx at 6 h (p = 0.029), PRx at 72 h (p = 0.002), PtiO2 at 72 h (p < 0.0005) and deltaPtiO2 (p = 0.023) values, reflecting an improvement with time in survivors and a deterioration with time in non-survivors. In non-survivors, the magnitude of change in PtiO2 and CPP with time correlated in a negative linear fashion (p = 0.042 and 0.029, respectively) with the change in PRx with time, whereas no such relationship was seen in survivors. CONCLUSION: The severity of brain tissue oxygenation derangement correlates with increasing cerebrovascular dysautoregulation in patients succumbing to severe head injury, supporting the utility of PRx as a monitoring variable and the rationale for a target-driven approach to head injury management.

Adult↗
PubMed2006

Characterization of cerebrovascular reactivity after craniectomy for acute brain injury.

Analysis of slow waves in arterial blood pressure (ABP) and intracranial pressure (ICP) has been used as an index to describe cerebrovascular pressure-reactivity. It has been previously demonstrated that the pressure-reactivity index (PRx) can be used to reflect global cerebrovascular reactivity with changes in ABP. A positive PRx signifies a positive association between ABP and ICP, indicating a non-reactive vascular bed, while a negative PRx is reflective of intact cerebral autoregulation, where ABP waves provoke inversely correlated waves in ICP. To date, there has been no characterization of pressure-reactivity following decompressive craniectomy. In this prospective observational study, 33 patients who underwent surgery for acute brain injury with mass lesions for which the bone flap was left out were studied. The PRx was calculated as a moving correlation coefficient between 30 consecutive samples of values of ICP and ABP averaged for a period of 10 s. The time profiles of mean PRx values at 6-hourly intervals were analysed and compared with that in seven patients treated by medical therapy alone. The initial mean PRx 6 h after surgery was positive, indicative of disturbed pressure-reactivity. With time, PRx trended towards a more negative value, suggestive of an improving cerebrovascular autoregulatory reserve. The mean PRx 24 h after surgery was 0.28 (+/-0.26), while the mean PRx 72 h after surgery was 0.15 (+/-0.25) (p = 0.012). In contrast, the mean PRx in patients that were not decompressed did not change significantly with time (p = 0.357). Surgery in acute brain injury for which the bone flap is left out in anticipation of raised intracranial pressure in the postoperative period leads to an improved PRx as compared with controls. Craniectomy in this situation may have a contribution to the restoration of disturbed cerebrovascular pressure-reactivity.

Adult↗
PubMed2006

Investigating gender differences in outcome following severe traumatic brain injury in a predominantly Asian population.

The objective of this study was to investigate if there are possible gender differences in relation to outcome following closed severe traumatic brain injury (TBI) in a predominantly Asian population. A study was conducted using our prospectively maintained TBI database of 672 patients with severe TBI admitted into our neurosurgical intensive care unit. All patients were managed on a standardized protocol in accordance with the Guidelines to the management of severe traumatic brain injury. Glasgow Outcome Score was used to measure the outcome of patients 6 months postinjury. There were 525 males and 147 females, with the latter significantly older than their counterpart. Females had a significantly higher mortality and poorer outcome compared with males. However, this difference was no longer significant when variables (presence of multiple injuries, postresuscitation pupil abnormalities and Glasgow Coma Score) are controlled for. However, both crude and adjusted odd ratios revealed that females aged 60 and below were significantly more likely to have a poorer outcome.

Accidents↗
PubMed2006

Diffusion tensor imaging in a symptomatic patient with an intra-axial arachnoid cyst.

We present a case of an elderly lady with a symptomatic large intra-axial right frontoparietal arachnoid cyst displacing the corticospinal tract (CST) posteromedially on diffusion tensor imaging. This information assisted the surgeons in confirming the symptomatic nature of the lesion, in planning an appropriate surgical procedure, as well as in prognostication of recovery.

Aged↗
PubMed2006

Demographical profiles of adult severe traumatic brain injury patients: implications for healthcare planning.

INTRODUCTION: In Singapore, severe traumatic brain injury (TBI) continues to be a major public health problem and devastating condition, with significant mortality and morbidity. By understanding the incidence, prevalence and implications of severe TBI in Singapore, strategic plans to meet the unique needs of these patients in the local context may be developed. METHODS: The demographical profiles of the adult severe TBI patients in Singapore were studied in this retrospective review of 528 patients admitted to the National Neuroscience Institute (NNI) from January 1999 to December 2003. RESULTS: There were 420 male and 108 female patients, age ranging from 15 to 96 years old, with a mean and standard deviation (SD) of 44.6 +/- 19.9 years, admitted to NNI during the study period. Motor vehicle and fall-related accidents were the leading causes of severe TBI. Three high-risk groups identified were young adults, elderly, and foreign workers. CONCLUSION: Preventive measures targeting at these high-risk groups are important to reduce the incidence of severe TBI.

Accidental Falls↗
PubMed2005

The Biomolecular Interaction Network Database and related tools 2005 update.

The Biomolecular Interaction Network Database (BIND) (http://bind.ca) archives biomolecular interaction, reaction, complex and pathway information. Our aim is to curate the details about molecular interactions that arise from published experimental research and to provide this information, as well as tools to enable data analysis, freely to researchers worldwide. BIND data are curated into a comprehensive machine-readable archive of computable information and provides users with methods to discover interactions and molecular mechanisms. BIND has worked to develop new methods for visualization that amplify the underlying annotation of genes and proteins to facilitate the study of molecular interaction networks. BIND has maintained an open database policy since its inception in 1999. Data growth has proceeded at a tremendous rate, approaching over 100 000 records. New services provided include a new BIND Query and Submission interface, a Standard Object Access Protocol service and the Small Molecule Interaction Database (http://smid.blueprint.org) that allows users to determine probable small molecule binding sites of new sequences and examine conserved binding residues.

Animals↗
PubMed2005

Linear correlation between stable intracranial pressure decrease and regional cerebral oxygenation improvement following mannitol administration in severe acute head injury patients.

OBJECTIVES: We investigated the relationship between stable decrease in intracranial pressure (ICP) following mannitol administration and variations in regional oxygenation (PtiO2) in severe traumatic brain injured (STBI) patients. METHODS: Fourteen STBI patients (Glasgow Coma Scale score < or = 8) admitted to the neurointensive care unit during a 12-month period were studied. Multiparameter data, including parenchymal tissue oxygen (PtiO2) and carbon dioxide tension, cerebral perfusion pressure, mean arterial pressure; temperature, pH and pressure reactivity index were measured. Point values from 53 mannitol administrations were extracted every five seconds and divided into five consecutive 30-minute epochs. Mean values and trends were identified. Postadministration epoch with maximum decrease in ICP was selected along with the means of the corresponding variables. These data were compared with baseline to derive the delta values. Mean deltaICP was then compared with deltaPtiO2 in each patient using linear correlation. FINDINGS: In patients with ICP0 > 20 mmHg (group A), PtiO2 increased in 69.6% of samples, whereas in group B (ICP0 < 20 mmHg), PtiO2 increased in only 50% of the samples. There was a significant negative correlation between mean deltaICP and deltaPtiO2 in both groups; Group A: r = -0.79 (P = 0.01); Group B: r = -0.92 (P = 0.01). CONCLUSIONS: There is a strong negative correlation between stable decrease in ICP following mannitol administration and improvement in regional oxygenation around the peri-contusional area. The data suggest a potentially favourable interaction between mannitol therapy and cerebral internal milieu in STBI patients.

Acute Disease↗
PubMed2005

Changes in cerebral hemodynamics and cerebral oxygenation during surgical evacuation for hypertensive intracerebral putaminal hemorrhage.

OBJECTIVES: The aim of this study was to evaluate the changes in cerebral hemodynamics, tissue oxygenation and blood flow before and after surgery for spontaneous intracerebral hematomas. METHODS: Eleven patients who underwent surgical decompression of spontaneous putaminal hematoma were studied. Intracranial pressure (ICP), cerebral perfusion pressure (CPP), brain tissue oxygen (PtiO2), and carbon dioxide tensions (PtiCO2), brain pH and regional cerebral blood flow (rCBF) were recorded prior to removing the bone flap and then on skin closure on completion of the operation. RESULTS: Following surgical decompression, mean ICP decreased significantly (P < 0.05); mean CPP, PtiO2, brain pH and rCBF improved although the changes were not significant. CONCLUSION: Surgical decompression for spontaneous intracerebral hematomas leads to significant reductions in ICP. This is accompanied by improvements in CPP, PtiO2 and rCBF in the penumbra.

Aged↗
PubMed2005

Brain tissue oxygenation monitoring in acute brain injury.

Cerebral ischemia is one of the most important causes of secondary insults following acute brain injury. While intracranial pressure monitoring in the intensive care unit constitutes the cornerstone of neurocritical care monitoring, it does not reflect the state of oxygenation of the injured brain. The holy grail of neuromonitoring is a modality that would reflect accurately real time the status of oxygenation in the tissue of interest, is robust, artefact free and that which provides information that can be used for therapeutic interventions and to improve outcome. Such a device could conceivably be used to augment the sensitivity of current multi-modality monitoring systems in the neurocritical management of brain injured patients. This article examines the availability of data in the literature to support clinical use of local tissue oxygen probes in intensive care.

Animals↗
PubMed2004

Spermine reduces infarction and neurological deficit following a rat model of middle cerebral artery occlusion: a magnetic resonance imaging study.

The role of nitric oxide (NO) in post-ischemic cerebral infarction has been extensively examined, but few studies have investigated its role on the neurological deficit. In the present study, we investigated the effect of spermine on the temporal evolution of infarct volume, NO production and neurological deficit using magnetic resonance imaging in a model of permanent focal cerebral ischemia in rats. Spermine given at 10 mg/kg 2 h after ischemia reduced the infarct volume by 40% and abolished brain NO production and improved the neurological score 24 h, 48 h and 72 h after ischemia. Spermine also reduced the neurological deficit as evaluated by rotamex, grip strength and neurological severity score tests.

Analysis of Variance↗
PubMed2004

Magnetic resonance screening of iron status in transfusion-dependent beta-thalassaemia patients.

The clinical utility of dual sequence (T1- and T2-weighted) magnetic resonance (MR) imaging in estimating liver iron concentration (LIC) in 32 transfusion-dependent beta-thalassaemia major (24 females; age 18.5+/-5.9 years) patients on desferrioxamine was evaluated. Signal intensity ratios (SIR) between liver, spleen and pancreas to psoas muscle were determined on both sequences. Relationships between clinical and MR parameters, and accuracy of SIR thresholds in determining adequacy of chelation from LIC were analysed. Liver T1- and T2-SIR were related to LIC (P < 0.001). T1-SIR < 0.60 predicted severe iron overload (LIC > 15 mg/g) with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%, 87%, 33% and 100% respectively. T2-SIR < 0.1 yielded 100% sensitivity, 93% specificity, 50% PPV and 100% NPV. T1-SIR > or = 1.1 predicted LIC < 7 mg/g with 69% sensitivity, 88% specificity, 85% PPV and 74% NPV. T2-SIR > or = 0.20 yielded 56.5% sensitivity, 94% specificity, 90% PPV and 71% NPV. LIC correlated with liver T1-SIR, liver T2-SIR and serum ferritin (r = -0.76, -0.65, 0.47, respectively; P < 0.01). Serum ferritin was inversely related to liver T1-SIR, liver T2-SIR and spleen T2-SIR (r = -0.35, -0.43, -0.40, respectively; P < 0.05). Mean total transfusion burden was not related to any MR parameter. Although neither MR sequence was a highly accurate predictor of LIC, SIR thresholds are useful to determine presence of iron overload and adequacy of chelation treatment.

Adolescent↗
PubMed2004

Patients who talk and deteriorate: a new look at an old problem.

BACKGROUND AND METHODS: We sought to review established prognostic indicators applied to Asian population, and to identify new risk factors for deterioration in patients who talked and deteriorated after traumatic brain injury (TBI). This retrospective study used our prospectively maintained TBI database. From August 1999 to July 2001, 324 patients were admitted to the neurosurgical intensive care unit (ICU). Thirty-eight patients (11.8%) talked between injury and subsequent deterioration into coma. Independent outcome predictors were studied. RESULTS AND CONCLUSION: Fourteen patients had subdural haematomas, 9 extradural haematomas, 19 contusions/haematomas and 3 subarachnoid haemorrhages. 81.5% of the patients had mass lesions potentially requiring surgery. Twenty patients had good functional recovery at 6 months (Glasgow Outcome Score 4 and 5); 18 were dead or vegetative. Age, gender, type of intracranial lesion and presence of coagulopathy were significantly correlated with outcome. Intracranial haematomas continue to be most significant in patients who talk and deteriorate. Coagulopathy was the strongest prognostic predictor of poor outcome with fibrinolytic parameters being reliable prognostic markers of head injury. Early identification, continued monitoring and treatment of coagulopathy should be our new look at improving outcome of these patients.

Adolescent↗
PubMed2003

Spinocerebellar ataxia type 3 presenting as an L-DOPA responsive dystonia phenotype in a Chinese family.

The clinical spectrum of spinocerebellar ataxia 3 (SCA 3) disease is wide and varied. We describe a Chinese patient with a mutation at the SCA 3 locus with clinical features of levodopa-responsive dystonia. The family history was suggestive of being autosomally dominant. Levodopa responsiveness though rare has been described in families with features of parkinsonism. Noteworthy is the relatively late onset of disease (>40 years) possibly explained by the low number of affected alleles at 59, the usual range being from 62 to 86, with the lowest recorded number at 56. This expands the wide and varied phenotypic manifestations of SCA 3, and highlights the observation that features suggestive of levodopa-responsive dystonia (DRD) such as focal dystonia, gait difficulty with diurnal fluctuation of symptoms, and a marked response to low doses of levodopa can be presenting features of SCA 3. SCA 3 should be considered a differential diagnosis in adult patients who present with DRD phenotype and with a positive family history.

Adult↗
PubMed2002

Prevalence and ethnic differences of autosomal-dominant cerebellar ataxia in Singapore.

We report the prevalence and ethnic differences of autosomal-dominant cerebellar ataxia (ADCA) in Singapore. Amongst 204 patients with ataxia who underwent genetic testing for dentatorubral-pallidoluysian atrophy (DRPLA) and for spinocerebellar ataxias (SCA) 1, 2, 3, 6, 7, 8, 10 and 12, 58 (28.4%) patients from 36 families tested positive. SCA 3 was identified in 31 (53.4%) patients from 15 families, SCA 2 in 17 (29.3%) patients from 12 families and SCA 1 in four (6.9%) patients from four families. Other SCA subtypes were rare. SCA 2 was the only subtype identified amongst ethnic Malay and ethnic Indian families. The estimated prevalence of ADCA in Singaporean families was at least 1 : 27,000. Based on the history and ancestry of Singaporeans, our study supported a founder effect for specific SCA subtypes and the association of ethnicity-specific SCA subtypes. Our findings suggest that SCA 2 is relatively common amongst the Malay race and that priority testing for SCA 3 and SCA 2 for ethnic Chinese, and SCA 2 for ethnic Malay, may be cost effective and relevant for the region.

Cerebellar Ataxia↗
PubMed2001

Prospective study of clinical and radiological outcome after anterior cervical discectomy.

Most surgeons undertaking anterior cervical discectomy (ACD) introduce a bone graft or cage into the disc space when the decompression is complete to prevent segmental collapse and preserve cervical spine alignment. We have conducted a prospective observational cohort study to investigate the relationship between cervical spine alignment and clinical outcome in 55 patients undergoing ACD without interbody graft or cage. At 12 months, the overall alignment of the cervical spine and the presence of segmental kyphosis at the operated level were correlated with clinical outcome measured by SF 36, Neck Disability Index and visual analogue neck pain score. Loss of the overall cervical lordosis was present in 30 patients and segmental kyphosis was found in 18. Analysis of clinical outcome showed no statistical differences between patients with preserved and abnormal cervical and segmental alignment. Disturbance of cervical and segmental alignment is common in patients following cervical discectomy, but does not appear to compromise clinical outcome at 12 months.

Adult↗
PubMed2001

Primary extramedullary plasmacytoma of the lacrimal gland.

Primary extramedullary plasmacytoma (EMP) of the lacrimal gland is rare. Here we describe the histopathologic and imaging findings in a 77-year-old patient with primary extramedullary plasmacytoma of the lacrimal gland. The usefulness of CD79a in the diagnosis of plasmacytoma and the good response of the tumor to combined surgery and radiotherapy are illustrated. Plamacytoma should be included in the differential diagnosis of lacrimal tumors.

Aged↗