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Biomedical subjects

P J Tyrrell

Publications and source records attributed to P J Tyrrell.

8 recordsLinked to original sources
PubMed1991

Progressive loss of speech output and orofacial dyspraxia associated with frontal lobe hypometabolism.

Three patients are described with slowly progressive loss of speech and dysarthria associated with orofacial dyspraxia, initially with intact written language, who subsequently developed more widespread cognitive abnormalities. Positron emission tomography (PET) revealed bifrontal hypometabolism in all of the patients, most marked in the inferior and lateral portions of both frontal lobes, with some extension into the parietal and temporal cortices in one case. These patients may represent a further example of focal progressive cortical degeneration.

Aged↗
PubMed1990

Clinical and positron emission tomographic studies in the 'extrapyramidal syndrome' of dementia of the Alzheimer type.

Extrapyramidal signs, particularly rigidity and tremor, have been reported in a proportion of patients with dementia of the Alzheimer type. To test the hypothesis that these extrapyramidal signs are similar clinically and neurochemically to the extrapyramidal signs of Parkinson's disease, a group of 20 patients satisfying clinical criteria for probable Alzheimer's disease were studied and assessed clinically for the presence of rigidity, tremor, and bradykinesia. In those patients with extrapyramidal signs, qualitative differences were observed between the signs in these patients and in subjects with Parkinson's disease. Fifteen of 20 patients underwent fluoro-18-dopa scans, which showed no significant difference in fluoro-18-dopa uptake into the caudate and putamen between normal subjects and the rigid and nonrigid patients with Alzheimer's disease, in contrast to the marked reduction in fluoro-18-dopa uptake into the putamen that is observed in Parkinson's disease. This provides clinical and in vivo neurochemical support for the hypothesis that extranigral factors may be involved in the pathogenesis of rigidity in Alzheimer's disease.

Adult↗
PubMed1990

Heterogeneity in progressive aphasia due to focal cortical atrophy. A clinical and PET study.

Six patients with a slowly progressive aphasic disorder due to degenerative cortical disease are reported. The length of history varied from 18 months to 6 years. In 5 patients, there was a naming deficit, associated in 4 of these with some abnormalities in comprehension. One patient had a progressive history of reduced speech output, which was associated with an orofacial dyspraxia. All patients were studied neuropsychologically, and in addition regional cerebral metabolism was measured using position emission tomography. A localized left hemisphere deficit was found in all patients except 1, who had the longest history and the most profound clinical deficit, and who also had right hemisphere hypometabolism. The major brunt of the deficit was in the anterior portion of the left temporal lobe in all but 1 case, the patient with poor speech output who had a more severe left posterior frontal deficit. These findings suggest that in progressive aphasia due to focal cortical atrophy there is heterogeneity in the clinical presentation and anatomical site of the deficit, with possible implications for the underlying aetiology.

Adult↗
PubMed1990

Progressive degeneration of the right temporal lobe studied with positron emission tomography.

A 79 year old man with a twelve year progressive history of prosopagnosia and recent naming difficulty, in whom other intellectual skills were preserved, is described. Positron emission tomography (PET) revealed an area of right temporal lobe hypometabolism, with an additional area of less severe hypometabolism at the left temporal pole. This may represent an example of progressive focal cortical degeneration similar to that associated with primary progressive dysphasia, but affecting the right temporal lobe.

Aged↗
PubMed1986

A microprocessor-controlled gas mixing device.

This paper describes the use of solenoid valves for the production of binary gas mixtures. The system is controlled by a microprocessor and is capable of delivering accurate flows and concentrations of gases over the ranges commonly used in anaesthesia. Since the flow produced by the valves is pulsatile, a system for mixing the gases and smoothing the pulses is described. A back pressure regulator is fitted downstream of each of two mixing/damping chambers and a method of using this as a flow transducer is described. The advantages of this system over conventional rotameters are discussed.

Anesthesia, Inhalation↗