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Biomedical subjects

Carl Counsell

Publications and source records attributed to Carl Counsell.

6 recordsLinked to original sources
PubMed2004

Monoamine oxidase type B inhibitors in early Parkinson's disease: meta-analysis of 17 randomised trials involving 3525 patients.

OBJECTIVE: To quantify more reliably the benefits and risks of monoamine oxidase type B inhibitors (MAOBIs) in early Parkinson's disease. DATA SOURCES: Searches of the Cochrane Library, Medline, Embase, PubMed, and Web of Science for years 1966-2003, plus major journals in the field, abstract books, and proceedings of meetings, for randomised trials comparing MAOBIs with placebo or levodopa. DATA EXTRACTION: Available data on mortality, motor complications, side effects, treatment compliance, and clinician rated disability (for example, unified Parkinson's disease rating scale) were extracted from 17 trials and combined using standard meta-analytic methods. RESULTS: No significant difference in mortality existed between patients on MAOBIs and control patients (odds ratio 1.13, 95% confidence interval 0.94 to 1.34; P = 0.2). Patients randomised to MAOBIs had significantly better total scores, motor scores, and activities of daily living scores on the unified Parkinson's disease rating scale at three months compared with patients taking placebo; they were also less likely to need additional levodopa (0.57, 0.48 to 0.67; P < 0.00001) or to develop motor fluctuations (0.75, 0.59 to 0.95; P = 0.02). No difference existed between the two groups in the incidence of side effects or withdrawal of patients. CONCLUSIONS: MAOBIs reduce disability, the need for levodopa, and the incidence of motor fluctuations, without substantial side effects or increased mortality. However, because few trials have compared MAOBIs with other antiparkinsonian drugs, uncertainty remains about the relative benefits and risks of MAOBIs. Further large, long term comparative trials that include patient rated quality of life measures are needed.

Antiparkinson Agents↗
PubMed2004

Movement Disorder Society Task Force report on the Hoehn and Yahr staging scale: status and recommendations.

The Movement Disorder Society Task Force for Rating Scales for Parkinson's disease (PD) prepared a critique of the Hoehn and Yahr scale (HY). Strengths of the HY scale include its wide utilization and acceptance. Progressively higher stages correlate with neuroimaging studies of dopaminergic loss, and high correlations exist between the HY scale and some standardized scales of motor impairment, disability, and quality of life. Weaknesses include the scale's mixing of impairment and disability and its non-linearity. Because the HY scale is weighted heavily toward postural instability as the primary index of disease severity, it does not capture completely impairments or disability from other motor features of PD and gives no information on nonmotor problems. Direct clinimetric testing of the HY scale has been very limited, but the scale fulfills at least some criteria for reliability and validity, especially for the midranges of the scale (Stages 2-4). Although a "modified HY scale" that includes 0.5 increments has been adopted widely, no clinimetric data are available on this adaptation. The Task Force recommends that: (1) the HY scale be used in its original form for demographic presentation of patient groups; (2) when the HY scale is used for group description, medians and ranges should be reported and analysis of changes should use nonparametric methods; (3) in research settings, the HY scale is useful primarily for defining inclusion/exclusion criteria; (4) to retain simplicity, clinicians should "rate what you see" and therefore incorporate comorbidities when assigning a HY stage; and (5) because of the wide usage of the modified HY scale with 0.5 increments, this adaptation warrants clinimetric testing. Without such testing, however, the original five-point scales should be maintained.

Feasibility Studies↗
PubMed2003

Systematic review of incidence studies of Parkinson's disease.

Incidence studies of Parkinson's disease (PD) are important for both health-care planning and epidemiological research. This report reviews the methods and results of previous incidence studies of PD and makes recommendations for future studies. Original articles that described the incidence of PD were located using several strategies. The methods were summarised, and the results of studies with similar methodologies were compared on a standardised population. Twenty-five incidence studies were included. Each used different methods to identify incident patients, although most screened both primary care and hospital records. Only eight studies were prospective, and only two of these had any follow-up. The diagnostic criteria for PD varied (11 studies used two or more cardinal motor features, four used the UK Brain Bank criteria), as did the exclusion criteria and the definition of an incident case. In 16 studies, attempts were made to confirm the diagnosis by examination of patients by a specialist as part of the study. None of the studies used identical methods, but five were sufficiently similar to merit comparison. Four of these gave a similar incidence (16-19/100000/year), but one from Italy had a much lower incidence (8.4/100000), the reason for which was unclear. Five studies found significantly greater incidence in men. This review highlights the difficulties in performing good quality incidence studies of PD. Further incidence studies using standardised methods are required. A set of minimal scientific criteria has been devised to improve the quality and consistency of future studies.

Adult↗
PubMed2003

Spatial channels of visual processing in cortical blindness.

Blindsight is the ability of some cortically blind patients to discriminate visual events presented within their field defect. We have examined a fundamental aspect of visual processing, namely the detection of spatial structures presented within the field defect of 10 cortically blind patients. The method outlined is based on the detection of high-contrast stimuli and is effective in flagging a 'window of detection' in the spatial frequency spectrum, should it exist. Here we report on the presence of a narrowly tuned psychophysical spatial channel optimally responding to frequencies less than 4 cycles/ degrees in eight out of 10 patients tested. The two patients who did not show any evidence of blindsight appear to have intact midbrain structures, but have lesions that extend from the occipital cortex to the thalamus. In addition, we have recorded subjective reports of awareness of the visual events in each trial. Detection scores of eight blindsight patients were subsequently subdivided based on the subjective reports of awareness. It appears that the psychophysical spatial channel-mediating responses in the absence of any awareness of the visual event have a narrower frequency response than those involved when the patients report some awareness of the visual event. The findings are discussed in relation to previous reports on the incidence of blindsight and performance on tasks involving spatial processing.

Adult↗
PubMed2002

Predicting outcome after acute and subacute stroke: development and validation of new prognostic models.

BACKGROUND AND PURPOSE: Statistical models to predict the outcome of patients with acute and subacute stroke could have several uses, but no adequate models exist. We therefore developed and validated new models. METHODS: Regression models to predict survival to 30 days after stroke and survival in a nondisabled state at 6 months were produced with the use of established guidelines on 530 patients from a stroke incidence study. Three models were produced for each outcome with progressively more detailed sets of predictor variables collected within 30 days of stroke onset. The models were externally validated and compared on 2 independent cohorts of stroke patients (538 and 1330 patients) by calculating the area under receiver operating characteristic curves (AUC) and by plotting calibration graphs. RESULTS: Models that included only 6 simple variables (age, living alone, independence in activities of daily living before the stroke, the verbal component of the Glasgow Coma Scale, arm power, ability to walk) generally performed as well as more complex models in both validation cohorts (AUC 0.84 to 0.88). They had good calibration but were overoptimistic in patients with the highest predicted probabilities of being independent. There were no differences in AUCs between patients seen within 48 hours of stroke onset and those seen later; between ischemic and hemorrhagic strokes; and between those with and without a previous stroke. CONCLUSIONS: The simple models performed well enough to be used for epidemiological purposes such as stratification in trials or correction for case mix. However, clinicians should be cautious about using these models, especially in hyperacute stroke, to influence individual patient management until they have been further evaluated. Further research is required to test whether additional information from brain imaging improves predictive accuracy.

Acute Disease↗