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Biomedical subjects

A J Fox

Publications and source records attributed to A J Fox.

At least 271 records · Page 15Linked to original sources
PubMed1975

Classification of radiological appearance and the derivation of a numerical score.

Approaches to the use of the International Labour Office U/C Classification of radiological appearances are considered in the context of multiple readers recording different degrees of abnormality. The Panel on Survey Radiology has been set up to provide a basis for standardization. An example of how the panel may be used in this role is given. The approach will depend on the standards maintained by the panel and on a greater understanding of the appearances associated with differing exposures.

Classification↗
PubMed1975

Myelographic cervical nerve root deformities.

Myelograms of nerve roots and adjacent subarachnoid space were reviewed to characterize 231 cervical root deformities from both symptomatic and asymptomatic patients. Good correlation between specific features of root deformities and clinical significance could not be demonstrated. Some features were slightly suggestive of clinical significance but occurred in a sufficient number of asymptomatic patients to make them unreliable. The most accurate determinants of root deformity significance are clincal and electromyographic findings.

Adult↗
PubMedDate not supplied

Modulation of cough and airway sensory fibres.

It is clear that there is still no definitive answer as to the role of RARs and C-fibres in cough, although the evidence would appear to implicate both fibre types, depending on the stimulus (Fig. 2). An upregulation of the activity of these fibres during disease states, by the action of inflammatory mediators, could contribute to an enhanced cough reflex, although the possible involvement of central sensitization provides another exciting possibility. Whilst an inhibition of the activity of airway afferents should conceivably lead to an inhibition of the cough reflex there remain few examples where this occurs. The available evidence suggests that agents such as opioids and cromoglycate can act on C-fibres, contributing to their antitussive activity, whilst frusemide has an inhibitory effect, on C- and A delta-fibres, only against certain stimuli. A more generalized inhibition of airway sensory nerves could be achieved by ion channel modulators, since these might act on both myelinated and non-myelinated fibres. It is interesting that the only clear examples of an inhibition of sensory nerve activity coupled with antitussive effects are provided by sodium channel blockers (local anaesthetics) and a potassium channel opener (NS1619). However, it should be borne in mind that cough is essentially a defensive reflex, becoming inappropriate during disease states. It might be desirable therefore to inhibit only the enhanced activity of sensory nerves seen during these conditions. Whether this is possible awaits further information on the changes in sensory nerve properties during inflammation.

Animals↗
PubMedDate not supplied

Iohexol cerebral angiography. Multicenter clinical trial.

Ionic contrast media currently used in cerebral angiography frequently cause discomfort due to hyperosmolality. This double-blind, multicenter trial compared two ionic media, meglumine iothalamate and meglumine-Na diatrizoate, with the new nonionic agent, iohexol, in 277 patients undergoing cerebral angiography. Vital signs, cardiovascular changes, and neurologic status were evaluated before, during, and after injection. Patients were observed for adverse reactions for up to 24 hours following studies. Patient discomfort and image quality were evaluated. Visualization was good or excellent with all media studied. No significant physiological differences were observed between the ionic and iohexol groups, but fewer iohexol patients experienced large increases (greater than 20 mmHg) in systolic blood pressure. Iohexol patients experienced significantly less discomfort; ionic patients reported severe discomfort 21/2 times more often. This finding was attributed to iohexol's low osmolality. Iohexol may be indicated particularly for use in selective angiograms where discomfort is a factor and for patients suspected of having blood-brain barrier disruption.

Adult↗
PubMedDate not supplied

Magnetic resonance imaging and 31P spectroscopy of an interictal cortical spike focus in the rat.

Magnetic resonance imaging (MRI) has proven to be an effective noninvasive technique for identifying lesions in patients with temporal lobe epilepsy. It has also been suggested that MRI may be sensitive to transient functional or metabolic changes in brain tissue. Increased brain electrical activity as monitored by electroencephalography causes changes in cerebral metabolism that may be responsible for focal or regional alterations in signal in the MRI of some patients. To test this hypotheses, experimental interictal cortical foci were produced in rats by topical application of penicillin to one hemisphere of the brain. In vivo MRI and phosphorous-31 (31P) spectroscopy of the focal and contralateral hemifield were performed in a 30-cm bore 1.89-T Bruker MSL system. 31P spectroscopy revealed no quantifiable differences in pH or in phosphocreatinine and ATP levels between the focal area and the contralateral hemisphere or between experimental and saline-treated control animals. There were also no differences in proton MRI. Similar areas of prolonged T2 were found near the cortex and in the deeper parenchyma in 55% of the experimental animals and 50% of the controls. These results suggest that the electrical activity from an interictal cortical spike focus is not severe enough to perturb cerebral metabolism sufficiently to be detectable by 31P spectroscopy or proton imaging techniques.

Animals↗
PubMedDate not supplied

Angiographic study of vasospasm following subarachnoid hemorrhage in monkeys.

A model for producing chronic cerebral vasospasm in monkeys by injecting autologous blood into the basal cistern is described. Spasm/narrowing was observed by angiography one hour after SAH in 8 out of 10 monkeys and in 5 of these 8, spasm was observed both one and two weeks later. No narrowing of the vessels was observed in the control cases. In monkeys that showed spasm one week after SAH, narrowing of the extracranial vertebral arteries was also observed. Repeated injections of blood at intervals of one and two weeks caused intensification of spasm in the intracranial portion of vertebral arteries and the basilar arteries. It is suggested that cerebral vasospasm following SAH may in part be mediated by a central control mechanism acting through the sympathetic nervous system in that extracranial vessels remote from direct contact with blood showed reactive narrowing.

Animals↗
PubMedDate not supplied

Intracranial internal carotid artery stenosis.

The advent of EC/IC Bypass surgery has focused attention on selected patients who might benefit from this innovative procedure. There is a poverty of natural history data pertaining to all such lesions. Two centres (Memphis, Tennessee and London, Ontario) pooled their resources to carry out a retrospective review of 58 patients with angiographically-proven intracranial internal carotid artery stenosis. Only 33% of the patients were alive and free from subsequent cerebral vascular events at the end of the mean follow-up of 30 months. Forty-three percent of the patients died during follow-up: 36% due to stroke and 44% because of cardiac disease. Forty-three percent of the patients suffered cerebral vascular events during the follow-up period: there were 17 strokes (29%) including 9 fatal strokes. The incidence of ipsilateral stroke was 19%; 65% of the strokes were appropriate to the stenotic intracranial carotid lesion under study. The annual ipsilateral stroke rate for patients with this lesion was 7.6% per year. This lesion detected on angiography is indicative of severe atheroma, and carries a serious risk of death due to ischemic heart disease or stroke.

Adult↗
PubMedDate not supplied

CT visualization of intracranial arterial thromboembolism.

Eight cases of presumed acute occlusion of intracranial arteries, 7 middle cerebral and 1 posterior cerebral, demonstrated the occluded artery as an abnormal high density structure on non-enhanced computed tomography. Three cases underwent subsequent angiography which confirmed the diagnosis. CT scanning is therefore able to visualize acute thromboembolism in the intracranial arteries. In the appropriate clinical setting of acute stroke, an artery visualized on non-contrast CT scan as diffuse high density and higher in density than other visualized vessels should be suspected as acutely occluded by clot.

Acute Disease↗
PubMedDate not supplied

Occurrence and mechanisms of occlusion of the anterior cerebral artery.

Occlusion of the anterior cerebral artery is a rare condition. A review of CT scans from 413 patients with ischemic infarction confirmed this low relative incidence: only 3% of CT scans evidencing infarction involved the territory of the anterior cerebral artery. Four major mechanisms of anterior cerebral artery occlusion have been identified in this series: Emboli in unusual hemodynamic circumstances such as patients presumed to have increased flow through the anterior communicating artery because of unilateral internal carotid artery occlusion. Propagation of thrombotic material from an occluded internal artery into the intracranial branches. Spasm, emboli or propagating thrombosis associated with anterior communicating aneurysm.

Adult↗
PubMedDate not supplied

Digital subtraction angiography: current clinical applications.

The applications of digital subtraction angiography (DSA) in neurologic diagnosis have been evolving as clinical experience with this technology accumulates. Initial enthusiasm with the intravenous contrast material injections has been tempered by often equivocal results. Intravenous DSA (IV-DSA) is still an accurate screening technique for extracranial carotid atherosclerosis, comparable to duplex ultrasound. Intracranial imaging is less satisfying with intravenous injections but reliable information is available in the assessment of the venous sinuses and parasellar internal arteries. The future of DSA lies with intraarterial contrast injections, as this technique substantially decreases the risks and costs of definitive cerebrovascular investigation.

Aged↗