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Biomedical subjects

P J Parkin

Publications and source records attributed to P J Parkin.

18 recordsLinked to original sources
PubMed2000

Brain stem stroke causing baroreflex failure and paroxysmal hypertension.

BACKGROUND: Paroxysmal neurogenic hypertension has been associated with a variety of diseases affecting the brain stem but has only rarely been reported after brain stem stroke. The mechanism is thought to involve increased sympathetic activity and baroreflex dysfunction. We undertook microneurographic recordings of muscle sympathetic nerve activity (MNSA) during beat-to-beat blood pressure (BP) monitoring to investigate this hypothesis. CASE DESCRIPTION: We investigated a 75-year-old woman who developed paroxysmal hypertension (BP 220/110 mm Hg) after a large left-sided medullary infarct. The paroxysms were triggered by changes in posture and were accompanied by tachycardia, diaphoresis, and headache. Serum catecholamines were substantially increased (norepinephrine level, 23.9 nmol/L 9 days after stroke; normal level, <3.8 nmol/L), and heart rate variability, measured by spectral analysis, was decreased in both low- and high-frequency domains (0.04 and 0.06 ms(2), respectively; normal level, 0.14+/-0.02 ms(2)). MNSA was increased in frequency (61 bursts per minute; normal level, 34+/-18 bursts per minute), and the burst amplitude was not inversely related to diastolic BP. BP and MNSA responses to cold pressor and isometric handgrip stimuli were intact. CONCLUSIONS: Extensive unilateral infarction of the brain stem in the region of the nucleus tractus solitarius may result in partial baroreflex dysfunction, increased sympathetic activity, and neurogenic paroxysmal hypertension.

Aged↗
PubMed2000

Real-time detection of epileptiform activity in the EEG: a blinded clinical trial.

The aim of this study was to determine the performance of a PC-based system for real-time detection and topographical mapping of epileptiform activity (EA) in the EEG during routine clinical recordings. The system incorporates a mimetic stage to locate candidate spikes (including sharp-waves) followed by two expert-system-based stages, which utilize spatial and wide-temporal contextual information in deciding whether candidate events are epileptiform or not. The data comprised 521 consecutive routine clinical EEG recordings (173 hours). Performance was evaluated by comparison with three independent electroencephalographers (EEGers-I). A second group of two EEGers (EEGers-II) separately interpreted the spike topographical maps and, for EEGs categorized as containing only questionable EA by the detection system, reviewed 6 sec segments of raw EEG centered on each questionable event. Thirty-eight of the EEGs were considered to contain definite EA by at least two of EEGers-I. The false detection rate of the system was 0.41 per hour. The system was found to have a sensitivity of 76% and a selectivity of 41% for EEGs containing definite EA. However, it only missed detection of EA in 5% of the recordings. EEGers-II agreed with EEGers-I on the distribution (generalized, lateralized, focal, multifocal) of EA in 79% of cases. This is by far the largest clinical evaluation of computerized spike detection reported in the literature and the only one to apply this in routine clinical recordings. The false detection rate is the lowest ever reported, suggesting that this multi-stage rule-based system is a powerful and practical tool in clinical electroencephalography and long-term EEG monitoring.

Adolescent↗
PubMed1993

Subcutaneous sumatriptan in acute treatment of migraine: a multicentre New Zealand trial.

AIM: To assess the effectiveness of subcutaneous sumatriptan (4 mg) in the acute treatment of migraine. METHODS: A randomised, double-blind, placebo controlled study was conducted in four New Zealand centres. On developing an acute attack of migraine, patients attended a centre where they were given either sumatriptan 4 mg or placebo by subcutaneous injection. Headache severity and clinical disability were measured over a 2 hour period. RESULTS: Fifty-one patients, aged 19-58 years with common or classical migraine were treated. Twenty-eight patients received 4 mg sumatriptan and 23 patients received placebo. Pretreatment headache severity was graded moderate in 76% and severe in 24%. Thirty-two percent of patients were sufficiently disabled to require bed rest and a further 48% had severe impairment of working ability. Sumatriptan was significantly more effective than placebo in relieving or reducing headache severity after 30 minutes. Sixty-four percent improved on sumatriptan compared to 27% on placebo. Functional disability, nausea, vomiting and photophobia were also greatly reduced. Adverse effects occurred in 17% of patients receiving placebo, and 82% receiving sumatriptan, the commonest being injection site reactions. CONCLUSION: Subcutaneous sumatriptan 4 mg is an effective and well-tolerated acute treatment in adult patients with moderate to severe common or classical migraine. The efficacy rate of 64% is lower than that found in recent controlled studies using a higher dose.

Adult↗
PubMed1993

Inclusion body myositis presenting solely as dysphagia.

Two patients presenting with dysphagia due to cricopharyngeal muscle dysfunction developed limb weakness 2 to 3 years later. Cricopharyngeal and limb muscle biopsies demonstrated changes typical of inclusion body myositis (IBM). Both patients improved following cricopharyngeal myotomy. IBM should be considered in patients presenting with dysphagia.

Biopsy↗
PubMed1990

Eaton-Lambert myasthenic syndrome: two cases with typical and atypical features.

Eaton-Lambert myasthenic syndrome is a rare disorder of neuromuscular transmission. We are unaware of previous New Zealand reports and present two patients. Characteristic abnormalities in compound muscle action potential amplitude following repetitive nerve stimulation and on single fibre electromyography were present. Both patients also showed mild patchy abnormalities in peripheral nerve conduction. The clinical picture resembled Guillain-Barre syndrome in one patient who developed severe generalised weakness and respiratory failure. In both patients the neurological presentation lead to the recognition of a previously asymptomatic small cell lung carcinoma.

Aged↗
PubMed1990

Improvement in chronic hepatocerebral degeneration following liver transplantation.

Chronic progressive hepatocerebral degeneration with spastic paraparesis, dementia, dysarthria, ataxia, tremor, and neuropsychiatric symptoms follows long-standing portal-systemic shunting, is associated with structural changes in the central nervous system, and does not respond to conventional therapy for hepatic encephalopathy. A case of advanced chronic liver disease with severe, progressive hepatocerebral degeneration after 23 yr of portal-systemic shunting is reported in whom there was significant objective improvement in intellectual function and in the chronic neurological signs 3 mo after orthotopic liver transplantation and further improvement 12 mo after transplantation.

Adult↗
PubMed1989

Impairment and recovery of ipsilateral sensory-motor function following unilateral cerebral infarction.

After unilateral cerebral hemisphere stroke, resulting in contralateral arm symptoms but largely sparing higher cerebral function, ipsilateral arm function is generally considered to be unaffected. In this study, 8 subjects with acute unilateral cerebral infarction (confirmed by CT scan) and primarily motor deficits underwent 11 computerized and 6 clinical assessments between 11 days and 12 months poststroke, and were compared with 12 normal subjects. Computerized tests comprised 3 pursuit tracking tasks (preview-random, step and a combination of these), designed to measure different aspects of integrated sensory-motor (S-M) function, and 12 tasks aimed at breaking tracking into various sensory, perceptual and motor components (joint movement sense, visual resolution, object perception, static and dynamic visuospatial perception, range of movement, grip and arm strength, reaction time, speed, static and dynamic steadiness). The asymptomatic arm was impaired on all but one of the computerized tests throughout the 12-month period, although to a lesser degree than the symptomatic arm. Grip strength was marginally impaired initially. Incomplete neurological recovery was seen in the asymptomatic arm for all functions except strength, speed and steadiness, possibly indicating their resistance to improvement. Clinical assessment detected no asymptomatic arm impairment and only a mild transient deficit of higher mental function. Our data suggest that (1) all cerebral hemisphere areas involved in S-M functions can exert some degree of bilateral motor control; (2) ipsilateral influence is never greater than contralateral influence, and is usually considerably less; and (3) the proportion of ipsilateral to contralateral control is closely related to the degree of continuous sensory feedback required by the particular task. The mechanism and degree of ipsilateral dysfunction can be explained by a 3-tier cerebral model of S-M integration comprising a lower level of functions with high contralateral specificity (somatosensory and motor), a middle level of non-limb-specific partially lateralized functions (ideomotor praxis and visuospatial perception) and an upper level of global mental activities (intellect, alertness, etc.).

Adult↗
PubMed1985

Severe hypertension and raised haematocrit: unusual presentation of Guillain-Barré syndrome.

A 36 year old man presented with headache, polyuria, thirst and weakness of the lower limbs. Hypertension and a high haematocrit were striking features on initial assessment. Subsequently the full picture of Guillain-Barré syndrome developed. Hormone measurement revealed marked sympathetic nervous system and renin-angiotensin system activation with a return to normal of both blood pressure and hormones with neurological recovery.

Adult↗
PubMed1984

Cerebral mucormycosis.

The clinical and pathological features of two patients who died of rhinocerebral mucormycosis are described. The cases illustrate two of the major mechanisms by which the brain may be affected in this condition. Although the diagnosis is often made only at post mortem the clinical features are often distinctive enough to allow recognition of this disease during life.

Adult↗
PubMed1984

Bilateral optic neuritis. A long-term follow-up.

We have endeavoured to determine the fate of the adults and children presenting with bilateral optic neuritis who were reported by Hierons and Lyle (1959) and Meadows (1969). We have follow-up information from a variety of sources on 31 of the 34 adults for up to thirty-seven years, and on 17 of 19 children after up to thirty-two years. Three adult cases were excluded after review. The visual prognosis was variable in the adults but excellent in the children. None of the children has developed clinically definite multiple sclerosis. Two of the 11 adults with simultaneous bilateral optic neuritis developed multiple sclerosis, compared with 8 of 20 with sequential optic neuritis. We conclude that the risk of developing multiple sclerosis after simultaneous bilateral optic neurities in childhood is low; in adult life it is probably higher, but some patients even after more than two decades have no clinical evidence of the disseminated disease. Bilateral optic neuritis is aetiologically and prognostically diverse.

Adolescent↗
PubMed1982

Amaurosis fugax: some aspects of management.

Fifty-one patients with amaurosis fugax were followed for a mean of 4.9 years from their first attack. Females predominated under the age of 50 years in contrast to men who presented in the older age group. Minor permanent visual sequelae occurred in only three patients, but cerebral vascular symptoms were present at some time in just under half the group. A range of abnormalities was identified on cerebral angiography and some of these correlated with certain clinical findings. Twenty patients were treated by surgery and permanent relief of significant improvement in symptoms occurred in 14. A group of patients who were at greater risk of cerebral vascular complications following angiography and surgery was identified. It is concluded that careful patient selection is necessary before surgery is recommended but that in a significant number of cases with relatively focal atheroma confined to one proximal internal carotid artery an excellent long term result following surgery may be expected.

Adult↗
PubMed1982

Effect of a synthetic pyrethroid deltamethrin on excitability changes following a nerve impulse.

Excitability changes following a nerve impulse were studied in the rat tail. Supernormal nerve excitability in control animals was present, as in other vertebrate nerve fibres, from 4-30 ms and was followed by a period of subnormal excitability extending up to 100-200 ms. Two to seven hours after intravenous administration of 1.5 mg/kg deltamethrin, supernormality was increased in degree and prolonged in duration for up to 400 ms. A minor effect was still detectable 24 hours after injection. This effect of deltamethrin on nerve excitability is probably due to persistent slight depolarisation of the nerve membrane resulting from its known effect of maintaining a proportion of sodium channels open for up to several hundred milliseconds following a nerve impulse.

Action Potentials↗
PubMed1978

Vertebral artery occlusion following manipulation of the neck.

A 23-year-old woman developed brainstem infarction following cervical manipulation. Vertebral angiography showed total occlusion of the left vertebral artery with a thrombus extending into the basilar artery. The literature dealing with this rare but serious complication of cervical manipulation is reviewed.

Adult↗
PubMedDate not supplied

Impairment and recovery profiles of sensory-motor function following stroke: single-case graphical analysis techniques.

Graphical analysis procedures have been developed to improve interpretation of sensory-motor tests from individual subjects following acute brain damage. The procedures have been applied to 11 unilateral stroke patients assessed serially over 12 months on a computerized quantitative sensory-motor test battery of which grip strength, arm speed, and tracking have been chosen for illustrative purposes. The results indicate that four graphs are necessary to fully demonstrate neurologic impairment and recovery of each sensory-motor function, although fewer graphs would be satisfactory in some applications. Such analyses have proven valuable in the display of serial performance of individual patients but demonstration of impairment and recovery is much more difficult than for group analyses.

Activities of Daily Living↗