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Biomedical subjects

R Iansek

Publications and source records attributed to R Iansek.

At least 73 records · Page 4Linked to original sources
PubMed1991

Motor function of the monkey globus pallidus. 2. Cognitive aspects of movement and phasic neuronal activity.

In order to study the role of the basal ganglia (BG) in cognitive aspects of movement, we recorded extracellularly from pallidal neurons in conscious monkeys while they performed a sequential wrist movement task consisting of a series of holds and ballistic jumps. The movement sequence had to be performed within specified time restraints and was predictable. We recorded the activity of 297 neurons whose discharges were related to the movement task. The movement-related response was found to be influenced by the contextual setting and by the degree of difficulty of the task in a subgroup of 82 neurons with a clear response to the first ballistic movement. Predictable and easy movements were usually represented by more prominent movement-related responses in 46% of these neurons; 35% of neurons from a different subset of 105 neurons also demonstrated a second phasic response just before the end of the final hold period of the task. This response was also found to be influenced by the predictability of the final hold period, both in its time duration and also by the direction of the following ballistic movement in double jump tasks. These findings were in keeping with a cognitive role for the BG in movement performance. In particular we suggest that the phasic neuronal activity was an internal cue generated by the BG for predictable movements of a subconscious nature which signals the end of a component of movement in a movement sequence. This cue is appropriately timed to terminate sustained neuronal activity in the SMA and to allow the next movement in the sequence to be executed.

Animals↗
PubMed1991

Intermittent subcutaneous apomorphine injection treatment for parkinsonian motor oscillations.

Eight patients with severe Parkinsonian motor oscillations have been treated with the dopamine receptor agonist apomorphine by intermittent subcutaneous self-injection as an adjunct to oral anti-Parkinsonian medication. The dopamine receptor antagonist domperidone was also given by mouth to prevent nausea. Six patients remain on chronic treatment (mean period 6.5 months) with improved control of motor function in each case. Four have had major enhancement of their quality of life. Benefits of this treatment stem from the training of patients to use intelligent behaviour to administer a promptly acting and effective pharmacological agent, thereby exercising a degree of direct control over previously unpredictable variations in motor performance.

Administration, Oral↗
PubMed1988

A prospective study of the predictive value of electroencephalographic abnormalities for epileptic loss of consciousness.

Patients referred to a neurology clinic with their first episode of loss of consciousness were studied prospectively in order to clarify the positive predictive value of an epileptic EEG for establishing an epileptic cause of the loss of consciousness. The clinical diagnosis was categorised as epileptic or non-epileptic. The EEG was reported as epileptic or non-epileptic, but abnormal or normal, according to recognised criteria. Patients were followed for a period ranging from 1 to 18 months to assess the accuracy of the original diagnosis. A total of 38 patients were available for analysis. Thirteen patients had a clinical diagnosis of epilepsy and 25 patients had a non-epileptic diagnosis. Five patients with an epileptic history had an epileptic EEG and 2 patients with a non-epileptic history had an epileptic EEG. Non-epileptic EEG abnormalities were present in a further 4 patients with a non-epileptic history. Follow-up was achieved for 53% of patients and in none of these was the final diagnosis different from the initial one. The positive predictive value of an epileptic EEG for a diagnosis of epilepsy was 71%, and the negative predictive value of a normal EEG for a diagnosis of non-epilepsy was 74%. The positive predictive value for any abnormality in the EEG for a diagnosis of epilepsy was 45%, and the negative predictive value of an absence of any abnormality in the EEG for a diagnosis of non-epilepsy was 70%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Value of visual evoked response and oligoclonal bands in cerebrospinal fluid in diagnosis of spinal multiple sclerosis.

To assess the predictive value of prolongation of visual evoked response (VER) plus the presence of oligoclonal bands in the cerebrospinal fluid (CSF) in the diagnosis of multiple sclerosis (MS) in patients with isolated cord lesions, the false-positive rate for the two tests combined was determined by a prospective analysis of 42 patients with a structural spinal cord lesion. The false-positive rate for the combination of VER and CSF abnormalities was zero, but the individual false-positive rates were 10% for VER and 12% for CSF protein oligoclonal bands. According to Bayes' theorem, and taking into account the false-positive rates of the tests in the population studied and the prevalence of MS and the true-positive rates for the tests as derived from published reports, abnormalities of VER and CSF protein together gave a probability of MS of 100%. However, if only either the VER or the CSF were abnormal, the probability of MS was 44% or 49%, respectively. An abnormal result for both tests thus indicates a sufficiently high probability of MS to exclude myelography, but a positive result in only one test warrants the procedure.

Adult↗
PubMed1987

Impairment of consciousness in migraine.

A series is reported of 25 subjects with migraine, whose attacks on some occasions involved impairment of consciousness. The disorder did not necessarily involve younger people, or occur early in the course of the malady.

Adolescent↗
PubMed1987

Cervical spondylosis and headaches.

The incidence of headaches in well documented cases of cervical spondylosis with neurological disability was reviewed. This was compared to that in a series of cases with a clinical diagnosis of tension headache in order to determine if there were any identifiable differences between the two types of headache. Fifty-nine cases of cervical spondylosis were reviewed. Five of these patients had headaches. Fifty patients with tension headaches were also reviewed. No differences were seen when location or other qualitative features of the headaches were compared between the two groups of patients. We conclude that the incidence of headache is low in cervical spondylosis and that the pattern of headache has no features that distinguish it from that of tension headache, suggesting that the pathogenesis is similar. We therefore suggest that the basis of headache in patients with cervical spondylosis is secondary muscle contraction.

Cervical Vertebrae↗
PubMed1986

An assessment of the possible protective effect of allopurinol in acute stroke.

Allopurinol has been shown to have a protective effect on ischaemic tissue by the indirect prevention of excessive purine loss. This property was tested in the gerbil model of acute stroke. A total of 69 animals were pretreated with an intraperitoneal injection of either allopurinol (50 mg/kg) or sterile water and then subjected to unilateral ligation of the left common carotid artery under general anaesthesia. The clinical effect of the ligation was grouped into three categories of normal, mild to moderate defect (splayed leg, turning behaviour) and severe defect (death, nonresponsiveness and seizures). More normal animals and fewer severely affected animals were present in the allopurinol treated group compared to controls, but only at 2 to 4 hours after carotid ligation (p less than 0.05). Histological examination of brain tissue from the normal category failed to reveal any difference in subclinical ischaemic damage between the two groups. It was concluded that allopurinol may have a protective effect in acute stroke and that this property warrants further elucidation.

Acute Disease↗
PubMed1986

Hypoglossal-facial nerve anastomosis: a clinical and electrophysiological follow-up.

Eight patients with acoustic neuroma and five patients with hemifacial spasm, who had undergone hypoglossal-facial nerve anastomosis 1-14 years previously, were reviewed clinically and electrophysiologically with an electrically elicited blink reflex. Functional recovery from the anastomosis, as rigorously judged on a scale of good, fair and poor, was fair to poor. Electrically it was found that the blink reflex was present in eight patients, suggesting facial nerve re-innervation of the facial musculature. This was confirmed by the mild recurrence of hemifacial spasm in four patients. Implications for the future role of this operative procedure are discussed.

Facial Muscles↗
PubMed1985

Bayesian diagnosis in presence of pre-existing disease.

Clinicians are increasingly facing complex diagnostic problems in patients who have a pre-existing disease and in whom new symptoms develop which may be complications of that disease or manifestations of another, perhaps more common, condition. The neurological complications of malignancy fall into this situation. The results of diagnostic tests applied under these circumstances run the risk of being misinterpreted, largely due to lack of appreciation of the powerful effect of the pre-existing disease on a priori estimates of disease which enter the differential diagnosis. A bayesian analysis outlines the basic structure of these novel problems--a transient neurological disturbance in a man with lung cancer but a negative computerised tomographic scan illustrating the points. Bayesian probability revision yields accurate estimates of the predictive values of tests that tend to be different from those generated by intuitive clinical reasoning.

Bayes Theorem↗
PubMed1985

A decision analytic approach to the role of visual evoked response and cerebrospinal fluid abnormalities in the management of singular spinal sclerosis.

With the use of Bayesian decision analytic techniques we assess the role of visual evoked response (VER) and cerebrospinal fluid (CSF) examinations in the investigation of patients with suspected singular spinal sclerosis. An abnormal VER increases the probability of multiple sclerosis by 50%. An associated CSF abnormality does not affect this probability. In a setting of a negative VER, CSF abnormalities increase the probability of multiple sclerosis by 27%. On currently available data, VER should therefore be the primary investigation in patients with suspected singular spinal sclerosis. If the result is abnormal myelography may be omitted. CSF examinations are only useful if VER facilities are not available.

Bayes Theorem↗
PubMed1985

The prognostic significance of intraventricular haemorrhage.

It is a generally held view that intraventricular haemorrhage carries a poor prognosis in cases of intracranial haemorrhage. We tested this view by retrospective analysis of the records of 258 patients who had intracranial blood on CT scans seen over a seven-year period. The mortality and morbidity for intraventricular and non-intraventricular haemorrhage were compared for the three major causes of intracranial bleeding, viz. aneurysm, trauma, and spontaneous intracerebral haemorrhage. No significant difference was found between the two groups for each aetiological category. It was concluded that the CT scan finding of intraventricular blood has no prognostic significance.

Brain Injuries↗
PubMed1984

The effects of reflex path length on clonus frequency in spastic muscles.

Clinical evaluation of clonus in spastic muscles was performed by comparing reflex path length with clonus frequency for different muscles in the same patient. It was found that clonus frequency varied inversely with reflex path length (r = 0.84, p less than 0.001). The findings confirm that clonus is generated by a peripheral mechanism of self re-excitation rather than a central spinal pacemaker.

Adult↗
PubMed1984

An analysis of the decision-making process in the management of malignant gliomas.

The decision to offer surgery or deep X-ray therapy to patients diagnosed as having malignant gliomas on CT scans is often problematical. Decision-tree analysis is used to make the underlying assumptions explicit in either strategy. Using biopsy and CT data obtained from our own experience, and survival figures from the literature, we are able to demonstrate that the decision is to a large extent related to value judgement. Specifically this relates to the assessment of the utility of long-term survival versus the immediate mortality and morbidity of biopsy in addition to possible difficulties in accepting long-term uncertainty of diagnosis if a biopsy is not performed.

Biopsy↗
PubMed1983

Application of decision analysis to management of cerebral arteriovenous malformation.

Consideration of cerebral arteriovenous malformation (AVM) illustrates how decision analysis may be used to evaluate systematically two treatment options--surgery before bleeding occurs or conservative management. The analysis balances risk of immediate surgical mortality and morbidity against the delayed risks inherent in conservative management. Because the condition is rare and local experience therefore scant, probability estimates have to be obtained from the literature. From these probability estimates and from estimates of attractiveness of various outcomes (made in this study by a clinician) a quantitative assessment of the risks and benefits of surgical versus medical management can be calculated. The finding is that conservative treatment is preferable to surgery in patients who present with an AVM before bleeding occurs, even when the probability estimates used are those obtained under conditions more favourable to surgery. The decision also remains unchanged when different attractiveness values are assigned to possible outcomes.

Adult↗
PubMed1981

Vasoactive peptides and hypertension: role of angiotensin converting enzyme.

Angiotensin converting enzyme plays a key role in the hormonal regulation of blood pressure. It is responsible for the production of the vasoconstrictor hormonal peptide angiotensin II as well as the destruction of the vasodilator peptide bradykinin. Recently, orally active specific inhibitors of angiotensin converting enzyme have become available. Captopril (SQ14225) blocks angiotensin I and potentiates bradykinin effects in vitro and in vivo. In man it leads to a fall in endogenous plasma angiotensin II, a rise in blood angiotensin I and renin, but no change in blood bradykinin can be detected. In sodium deplete normal subjects it lowers the blood pressure, but in sodium replete subjects it is without effect. Similarly, it will acutely lower blood pressure in renovascular and accelerated hypertension but not in essential hypertension. The acute hypotensive effect of captopril may therefore be due to inhibition of the renin-angiotensin system. However, in the long term, it is effective in lowering the blood pressure in patients with essential hypertension, especially when combined with a diuretic. This suggests that the long-term hypotensive effect differs from the short term effect, and involves mechanisms other than inhibition of the renin-angiotensin system. This may include local effects on blood vessels and the kidney and the kallikrein-kinin system.

Angiotensin I↗
PubMed1980

The monkey globus pallidus: neuronal discharge properties in relation to movement.

1. Recordings were made of the natural discharges of 388 pallidal neurones in awake, free-to-move monkeys in order to describe the discharge properties of such neurones in relation to normal movement performance. 2. Of the 388 neurones, 156 discharged only in association with one direction of movement of the forelimb about a specific joint. If that movement was not taking place the neurone would not discharge. 3. All joints and directions of movement for the upper limb were represented by clusters of cells within the pallidal population. 4. Twenty-nine per cent of neurones co-varied with movement of both contralateral and ipsilateral limb for the same direction of movement about a given joint; distal movements were represented with similar frequency to proximal movements in this group. 5. Afferent information provided by natural stimulation of peripheral receptors did not directly influence either the discharging or non-discharging pallidal neurones. 6. Movement related neurones were regionally organized and were found in the posterior part of the pallidum.

Action Potentials↗