Biomedical subjects

M A Hamilton-Bruce

Publications and source records attributed to M A Hamilton-Bruce.

6 recordsLinked to original sources

PubMed1994

Calibration assessment in quantitative electroencephalographic brainmapping and evoked potential studies.

Acquisition of a Cadwell Spectrum 32 resulted in the introduction of quantitative electrophysiological brainmapping techniques in our neurophysiology laboratory. To ascertain the accuracy and consistency of our equipment, we performed the following tests: inputting a calibration signal and measuring the resultant amplitudes for quantitative electroencephalographs (qEEGs) and evoked potentials (EPs) in the mapping and standard montages, inputting a synchronous calibration signal and mapping it at varying times for qEEGs and EPs, as well as re-analysing the same electroencephalographic (EEG) epochs previously selected from 20 control subjects. QEEG amplitudes varied from -5.4% to +5.8% and EPs by 9.5% or less, and after an EP software upgrade, by 5.5% or less. QEEG voltage mapping showed variation of only one color increment across the map, which could, in our example, represent up to 25.2% of the scale used. Re-analysis of previously selected epochs yielded identical results. We have established some of the accuracy and consistency limits of the hard- and software of our system with respect to the quantitative and topographic data. We conclude that such systems need to be calibration-checked in the laboratories in which they are used, with an independent signal generator. Users also need to be aware that scaling of topographic maps could lead to erroneous conclusions, as perceived amplitude changes could affect the interpretation of both initial and serial studies.

Brain Mapping↗

PubMed1994

Quality assurance in a neurophysiology laboratory.

In order to assess patient satisfaction with the Neurophysiology Services within our department, we undertook a pilot study using a simple questionnaire designed by staff members (MAHB and ABB). Patients were approached after their tests (nerve conduction tests (NCTs), electromyography (EMG) and electroencephalography (EEG)) were completed, by staff not involved in the testing. 31 patients were approached and all completed the questionnaire. None reported being inconvenienced by an undue waiting time. All felt that adequate information about the test had been provided, that their personal comfort and feelings were considered, and that they were adequately informed of the time and place at which the test results would be available. 61% considered their overall treatment excellent, the remainder good. To date, increased departmental awareness has resulted in staff participation in program evaluation, design of an outcomes hierarchy for the department, redesigning the patients' waiting area and, overall, a more active participation in quality assurance. We see this pilot study as a baseline for future more in-depth client and staff evaluations thereby promoting quality performance improvement.

Electroencephalography↗

PubMed1991

Interoperator variability in quantitative electroencephalography.

The purpose of the study was to determine whether quantitative or discriminant analysis of the electroencephalograph (EEG) would vary significantly when the same EEG was analysed by 3 different operators. EEGs on 10 healthy volunteers were recorded on the Cadwell Spectrum AT 386, using the Electrocap (10-20 system). The EEGs were analysed independently, with each operator selecting the first 48 artifact-free epochs. The results were analysed using the non-parametric Friedman two-way analysis of variance (ANOVA) for the discrimination analysis and a one-way ANOVA for the monopolar and bipolar Absolute Power raw measures. Statistical analysis of the discriminant data showed no significant differences between operators, with 7 of 10 studies yielding the same results. The remaining 3 studies were classified either as borderline or normal when analysed by different operators. Although a series of "t" tests comparing 2 operators showed most variability occurring in Absolute Power as compared with Relative Power, Power Asymmetry and Coherence, ANOVA of the raw mono- and bipolar Absolute Power measures showed no significant differences between the operators at the P = 0.05 level. Thus the differences between the operators were non-significant when comparing quantitative EEG analyses with respect to both the raw measures and the discriminant analyses.

Analysis of Variance↗

PubMed1991

Familial spastic paraplegia: an electrophysiological study of central sensory conduction pathways.

An electrophysiological assessment has been performed studying somatosensory, visual and auditory pathways in clinically affected and unaffected members from 4 pedigrees with the autosomal form of 'pure' familial spastic paraplegia (n = 32). In some members from 2 families, testing of all 3 sensory pathways showed abnormal results, even in those clinically unaffected. In another family, some had abnormal somatosensory and visual pathways, with no involvement of the auditory pathway. In a further family, the somatosensory and brainstem auditory pathways were abnormal, with sparing of the visual pathway. These findings indicate that the neuronal degeneration in familial spastic paraplegia extends beyond the spinal cord and involves the visual and auditory pathways. The differences between families, and the asymptomatic abnormalities in clinically unaffected members, suggest diversity in the expression of the genetic defect.

Evoked Potentials, Auditory, Brain Stem↗

PubMed1989

Evaluation of evoked potentials and cerebrospinal fluid analysis in the differential diagnosis of multiple sclerosis.

During the 6 years to December 1988, 191 patients underwent evoked potential (EP) studies and cerebrospinal fluid (CSF) analysis for oligoclonal bands at the Queen Elizabeth Hospital, for the differential diagnosis of multiple sclerosis (MS). Clinical data at the time of study separated patients into 3 groups, as follows: (i) multiple sclerosis (n = 90) - McDonald and Halliday Classification, 1977, (ii) other neurological disease (n = 82) and (iii) no neurological disease (n = 19). In cases of clinically definite MS, visual evoked potentials (VEPs) were abnormal and oligoclonal bands were detected in 64% and 59% of cases, respectively. However, only 15% of patients with suspected MS had abnormal VEPs, and only 23% had oligoclonal bands. Other studies have shown figures differing from these, though not necessarily significantly. We found a substantial number of EP (20%) but few CSF (4%) abnormalities in disorders other than MS, and no abnormalities in cases without neurological disease. The various figures for abnormal results in cases assessed for the differential diagnosis of MS are influenced not only by laboratory methods, but by the degree of clinical suspicion in relation to the cases selected, as well as by differences in populations from which cases are derived. Long-term prospective studies of diagnostically indeterminate cases are still required to determine the diagnostic weighting that can be applied on the basis of abnormal investigational results. Magnetic resonance imaging will not resolve these questions since it has limitations of its own, particularly with regard to specificity.

Adult↗

PubMed1988

The flight of colours test. Its value as an indicator of dysfunction of the visual pathways.

The flight of colours (FOC) test was compared with visual evoked potentials (VEPs) in 135 patients in a 2 year prospective study, to determine whether the FOC test is a sensitive and reliable alternative. We obtained an 80% overall agreement between the tests, confirming the levels of agreement reported by Rolak (87%) and Swart and Millac (92%). Abnormal VEPs, however, were more closely associated with cases of clinically definite multiple sclerosis (MS) while abnormal FOCs were more frequent in cases of non-demyelinating disease and cases without clinically evident optic nerve or other ocular disorder. We cannot explain this result by any demonstrated superiority of the FOC test over VEPs in non-demyelinating visual disturbances, whether clinically evident or not. Thus the study does not confirm the earlier expectation that the FOC test would be a reliable alternative to the study of VEPs in the differential diagnosis of MS.

Adolescent↗