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Biomedical subjects

A J Strong

Publications and source records attributed to A J Strong.

At least 37 records · Page 2Linked to original sources
PubMed1995

Surgical cure of hypertension in a patient with brainstem capillary haemangioblastoma containing neuropeptide Y.

We describe a 29-year-old woman with persistent arterial hypertension which resolved following complete excision of a capillary haemangioblastoma from within the spinal cord at the cervico-medullary junction. Immunohistochemical staining was positive for neuropeptide Y in capillary walls and nerves in the tumour. This raises the possibility of an association between neuropeptide Y and the central control of blood pressure in man.

Adult↗
PubMed1994

Digital imaging of umbelliferone clearance: a method for repeated measurements of cerebral cortical blood flow with high temporal and spatial resolution.

We have developed a procedure for digital imaging of the exposed cerebral cortex during elution of a fluorescent dye. This avoids disturbing the cortex and has provided a method for the repeated estimation of regional CBF (rCBF) with a high topographical resolution. Under varying conditions of MABP and arterial blood gases, grey-level images of the exposed cortex irradiated with ultraviolet light (340 or 370 nm) were digitised (8 bits) at 15-s intervals after the injection of 1-2 ml of saturated umbelliferone solution into the lingual or external carotid artery of anaesthetised cats and rabbits. Specifically designed software allowed (a) regions of interest (ROIs) in the exposed cortex to be defined that were automatically applied to the sequence of images in a selected clearance and (b) solution of the initial slope equation for rCBF from the decay in grey-level fluorescence by exponential regression. Separate software that solved the equation at the level of a single pixel allowed a pseudocolour map of cortical rCBF to be generated. The factors affecting the resolution of this technique have been identified and quantified. Thus consistent and reproducible results were obtained provided that the fluorescence enhancement exceeded 20 grey levels and the r2 coefficient for regression was 90% or above. Mean rCBF values of 99.5 [95% confidence interval (CI), 89.4-110] ml 100 g-1 min-1 were obtained for rabbits (N = 12; mean MABP = 75.2; mean PaCO2 = 32.9; PaO2 = 111.8; pH 7.38) and 65.1 (95% CI, 55.1-75.1) ml 100 g-1 min-1 for cats (N = 8; mean MABP = 92.8; PaCO2 = 31.5; PaO2 = 114.6, pH 7.40).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Accurate frameless registration of MR and CT images of the head: applications in planning surgery and radiation therapy.

PURPOSE: To evaluate the feasibility and efficacy of a three-dimensional image registration technique for planning skull base surgery, performing frameless image registration for stereotaxic neurosurgery, and staging nasopharyngeal carcinoma. MATERIALS AND METHODS: Computed tomographic (CT) and magnetic resonance (MR) images from 35 patients were registered by identifying 12-16 homologous landmarks with each modality. Images were displayed as overlaid sections or rendered three-dimensional scenes. The clarity of the combined images from 15 patients undergoing skull base surgery was compared with that of the conventional displays. RESULTS: Images were combined for three applications, with an accuracy of 1-2 mm. For the 15 patients undergoing skull base surgery, the combined images were significantly better at depicting the relationship between bone and lesion than conventional display (P < .01). CONCLUSION: MR and CT images of the head can be accurately registered without using external markers or substantially altering image acquisition protocols. The resulting images can show the radiologic information more clearly than conventional viewing.

Adult↗
PubMed1994

Combined and three-dimensional rendered multimodal data for planning cranial base surgery: a prospective evaluation.

Magnetic resonance (MR), X-ray computed tomography (CT), and angiographic images best depict soft tissue, bone, and blood vessels respectively. No one on its own is sufficient in the preoperative assessment of cranial base lesions. We have developed and evaluated a computational technique for the three-dimensional (3D) combination and display of multimodality images for planning cranial base surgery. This evaluation was prospective and performed in such a way that the results could be quantified. Eight patients (three acoustic neuromas, four subfrontal and suprasellar meningiomas, and one petrous apex meningioma) underwent MR, CT, and MR angiographic investigations. These images were registered with anatomical landmarks rather than an external frame. Two techniques were used to display the resulting combined images: multiple slices in which bone from CT was overlaid on soft tissue from registered MR and pseudo-3D-rendered movie sequences showing bone from CT, lesions and optic nerves from MR, and blood vessels from MR angiography. The advantages of the combined displays compared with those of conventional methods of viewing were assessed prospectively by the operating surgeon and by an independent surgeon, and the results were compared with operative findings. The preoperative assessment showed a significant improvement (P < 0.05, sign test) in the depiction of both individual structures (lesion and bone from overlaid slices and lesion and vasculature from 3D-rendered displays) and structural relationships (tumor-bone relationships from overlaid slices and of tumor-vasculature relationships from 3D-rendered displays). The operative findings indicated that a more accurate interpretation of this information was possible from the combined images.

Adult↗
PubMed1993

Acoustic tumour volume and the prediction of facial nerve functional outcome from intraoperative monitoring.

The long-term facial function in 26 patients undergoing surgery to remove an acoustic neuroma has been related to the tumour volume (ml) estimated by computerized tomogram (CT) reconstruction techniques. Analysis of data allowed accurate categorization into 'small' (= < 5 ml) and 'large' (> 5 ml) tumours, which gave the maximum prognostic distinction between two groups for facial recovery. Thus, of the 14 patients with small volume tumours, 11 achieved a good (House grade I or II) facial outcome compared with 1 out of 12 patients with large tumours. Combined with the information derived from the assessment of intraoperative facial nerve electrical integrity using a combined nerve stimulator and EMG monitor, long-term facial function was predictable for all small tumours defined by volume. This represented a 15% improvement in prediction of facial recovery when defining tumour size by maximum linear dimension (small = < 2.5 cm, large > 2.5 cm). The calculations of volume obtained using a simplified ellipsoidal model compared well with CT reconstructed values (r2 = 0.85), and gave identical prediction and outcome comparisons.

Adolescent↗
PubMed1992

The Maudsley Mentation test: a method for extended monitoring of mental status after aneurysmal subarachnoid hemorrhage.

A new scale for the repeated, rapid assessment of mental function in patients with subarachnoid hemorrhage is described. Its reproducibility is evaluated and early experience with its use in the intended clinical setting is reported. The test (Maudsley Mentation Test) proved to be more sensitive to fluctuations in cerebral functioning than existing measures of conscious level, and the results were reproducible among observers with different backgrounds (surgeons, nurses, and psychologists). The results suggest a relationship between performance on mentation testing and quality of outcome. The Maudsley Mentation Test is thought to offer a suitable measure with which to monitor patients during the acute phase of their illness to supplement clinical assessment and provide evidence of deterioration at an early stage. It is also potentially useful as an end point in acute protection and treatment studies.

Adult↗
PubMed1991

Prediction of facial nerve function after surgery for cerebellopontine angle tumors: use of a facial nerve stimulator and monitor.

A series of 18 patients undergoing surgery for cerebellopontine angle tumors is reported. Patients were grouped according to size of tumor (0 to 2.5 cm, 11 cases; more than 2.5 cm, 7 cases). In all, the facial nerve was identified and conductance assessed by monitoring the facial electromyographic response to facial nerve stimulation. Postoperative facial nerve function was graded clinically after 3 months according to the House scale. Tumor removal was complete in all cases. In patients with tumors up to 2.5 cm the facial nerve was intact to visual inspection at the end of the procedure in all but one, where partial division was evident. In this group intraoperative facial nerve stimulation indicated electrical integrity in 8 of the 11 cases, all of which regained good facial nerve function postoperatively (House grades I and II). Nerve conduction was lost during the operation in the remaining three patients with small tumors; two subsequently developed a moderately severe (grade IV) dysfunction and the third, a total paralysis (grade VI). In the large (more than 2.5 cm) tumor group the facial nerve was anatomically intact in five of the seven cases, partially divided in one, and completely sectioned in the remaining case. Facial nerve stimulation indicated functional integrity in three patients, two of whom developed moderate (grade III) and the third a severe (grade V) dysfunction. In the other four cases nerve function could not be detected at operation; three of these developed a moderate facial nerve dysfunction (grade III/IV) and the final case a complete paralysis (grade VI). Intraoperative facial nerve monitoring appeared to predict eventual facial function accurately in the small tumor group, but did not predict facial nerve recovery reliably following surgery for larger tumors.

Journal Article↗
PubMed1991

Registration of MR and CT images for skull base surgery using point-like anatomical features.

We have developed a registration technique for combining magnetic resonance imaging (MRI) and computed tomography (CT) images of the skull base for use in surgical planning. The technique is based on user identification of point-like landmarks visible in both modalities. The combination of images involves a small amount of expert interaction, is relatively quick and preliminary evaluation indicates that it is accurate to within 1.5 mm. Registered or fused images can be viewed either on an image processing workstation, or fused images can be printed onto conventional film for convenience in clinical use. We present one patient in order to demonstrate the technique's indications and advantages.

Humans↗
PubMed1990

Insulin protects cognitive function in experimental stroke.

There is evidence from in vitro systems that the extent of neuronal loss in acute central nervous system ischaemia can be reduced by manoeuvres which restrict availability of glucose to the ischaemic area. Experiments were designed to test whether hypoglycaemia induced with insulin is associated with improved behavioural outcome in a recovery model of stroke. Rats learned a maze task as a test of working memory, believed to be subserved by the hippocampus, and then had a period of cerebral ischaemia, followed by reperfusion. After an interval of 14 days they were tested on the same maze, where lesioned animals had very significant (p less than 0.0001) impairment of working memory, whereas lesioned and treated (2.0 u/kg-1 insulin, minimum single plasma glucose value: 3.1 mmol/l-1) animals were indistinguishable from control animals. It is concluded that a striking degree of protection can be obtained with levels of mild hypoglycaemia which may be acceptable and practicable for use in humans.

Animals↗
PubMed1988

Simple peroperative antimicrobial chemoprophylaxis in elective neurosurgical operations.

From August 1981 to February 1982 postoperative infections due to different strains of penicillin-resistant Staphylococcus aureus occurred in 20 of 467 patients (4.3%) undergoing elective cranial and spinal operations. These infections were not attributable to defects in procedures or the theatre environment, therefore chemoprophylaxis was instituted. In the following 8 months, when patients were given penicillin G and sulphadiazine for 5 days commencing immediately postoperatively, S. aureus infections occurred in five of 579 patients (0.9%). In a subsequent randomized uncontrolled study, infections occurred in six of 265 patients receiving penicillin (2.3%), three of 270 receiving penicillin and sulphadiazine (1.1%) and one of 45 receiving erythromycin (2.2%) immediately postoperatively for 5 days. In a further study in which 587 patients received penicillin for 5 days commencing immediately preoperatively, infections due to S. aureus occurred in six (1.1%). Infections due to gram-negative organisms were seen in five (0.4%) of 1167 patients in the two uncontrolled studies.

Drug Therapy, Combination↗
PubMed1988

Changes in vascular and metabolic reactivity as indices of ischaemia in the penumbra.

The reactivities of cerebral cortical blood flow (hydrogen clearance) and of compensated NADH fluorescence to local cortical electrical stimulation were examined on the marginal gyrus before and after transorbital occlusion of the middle cerebral artery in cats. Prestimulus cerebral blood flow (CBF) was 38.2 +/- 12.9 (SD) ml 100 g-1 min-1 and fell to 19.8 +/- 11.1 following occlusion (p less than 0.02). Peak hydrogen clearance rate (percent increase above prestimulus clearance) was 81.6 +/- 53.6 and fell to 19.9 +/- 29.8 after middle cerebral artery occlusion (p less than 0.01). Steady-state NADH fluorescence rose from 33.5 +/- 10.7 to 40.5 +/- 17.6% full-scale deflection following MCAO (p less than 0.01). Latency from stimulus to maximal fluorescence depression in response to cortical stimulation increased from 12.2 +/- 8.2 to 22.1 +/- 11.9 s (p less than 0.01). Hyperaemic responses at anteromedial sites on the marginal gyrus significantly exceeded those at posterolateral sites. The results are interpreted as indicating early ischaemic metabolic change; however, the presence of residual vasodilator responses to stimulation suggests that flow reduction and early ischaemic change in the territory studied are not simply due to inadequate collateral input, but may also reflect deafferentation or functional suppression. The possible significance of diminished vascular reactivity in the penumbra as a cause of increased vulnerability to extracellular release of excitatory amino acids is discussed.

Animals↗
PubMed1987

A double-radionuclide autoradiographic method using N-isopropyl-iodoamphetamine for sequential measurements of local cerebral blood flow.

A double-radionuclide autoradiographic method has been assessed for sequential determinations of local CBF (LCBF). It is based on two successive intravascular injections of N-isopropyl-p-iodoamphetamine (IMP) labelled with different radionuclides, whose concentrations can later be differentiated in the same tissue section using double-radionuclide autoradiography. Previous studies suggested that the distribution of IMP, up to 30 min after its administration, still represents LCBFs. Our data indicate that, provided the tracer is injected directly into the left ventricle, there is little back diffusion from normal brain to blood under physiological conditions for at least 35 min following the tracer injection and an injection of unlabelled IMP, in a dose larger than that used for blood flow determination, does not displace any labelled IMP previously taken up by the brain, nor does it displace any labelled IMP previously accumulated in the lung that would lead to secondary brain uptake. On the basis of these results, we conclude that sequential autoradiographic determinations of LCBF using IMP labelled with different radionuclides is possible. This is a promising experimental method for the simultaneous investigation of changes in LCBF in several CNS structures.

Amphetamines↗
PubMed1986

The effects of etomidate in the cat middle cerebral artery occlusion model of brain ischaemia. An experimental study.

The effects of etomidate on focal cerebral ischaemia following transorbital occlusion of the cat middle cerebral artery were investigated. Etomidate had no effect on CBF before or after onset of ischaemia by comparison with controls, but caused a greater fall in CBF in cats with high preocclusion or initial ischaemic CBF than in those in which CBF was lower. There were more sustained rises in Kp on SG. The established flow threshold for water accumulation was lost; more gyri with CBF above and fewer gyri with CBF below the flow threshold accumulated water. The relationship between mean occlusion CBF and in vitro GABA uptake was lost; uptakes from MG were lower and from SG and EG higher than expected. In the ischaemic penumbra there was a trend towards reduction in CBF, disruption of ion homeostasis and cerebral oedema formation, whilst in areas of lower flow there was some recovery of GABA uptake and less cerebral oedema following administration of etomidate.

Animals↗
PubMed1985

Protection of respiration of a crude mitochondrial preparation in cerebral ischaemia by control of blood glucose.

There is evidence that systemic hyperglycaemia influences the evolution of cerebral ischaemia adversely, through enhancement of brain lactic acidosis. A potential protective regimen based on induction of mild hypoglycaemia with insulin was therefore studied. Respiratory control in brain mitochondria prepared from the ischaemic hemisphere of rats subjected to unilateral common carotid artery occlusion for one hour was abolished, but was partially preserved in insulin-treated rats (p = 0.01).

Animals↗
PubMed1985

The effects of hyperglycaemia on changes during reperfusion following focal cerebral ischaemia in the cat.

The effects of isosmolar loads of glucose and saline after onset of focal cerebral ischaemia (middle cerebral artery occlusion) were compared in cats. In cats given saline cerebral blood flow (CBF) fell and then rose slightly on the marginal gyrus (infarct penumbra). There was a sustained fall in CBF on the suprasylvian and ectosylvian gyri (infarct core). Reperfusion restored blood flow to preocclusion levels with no overall postischaemic hypoperfusion. Below ischaemic flows of 14 ml/100 g/min brain specific gravity was reduced in a smaller proportion of gyri by contrast with non reperfused cortex, suggesting that in some gyri resolution of cerebral oedema had taken place. GABA uptake was normal in the infarct core, but was reduced within the ischaemic penumbra. In animals given glucose after occlusion, CBF fell on the marginal gyrus during reperfusion. The degree of resolution of cerebral oedema was less than in saline infused cats. GABA uptake showed a pattern of abnormality similar to that seen in saline infused cats, except that uptake values were lower in the infarct core. Pial surface potassium activity remained elevated in the penumbra following reperfusion in glucose infused cats, but returned to normal in saline infused cats. Implications for the management of cerebral ischaemia in man are discussed.

Animals↗
PubMed1985

[Hypotension and diffusion of Rb-86 in the rat brain].

Studies on the permeability of potassium at the blood-brain barrier of rats show that, under normal conditions, the concentration of this ion is kept constant although wide variations in plasma are present. 86Rb has been utilized as an analog of K+. The permeability constant for control animals (arterial blood pressure of 100 +/- 3 mmHg), has been determined in 0.926 +/- 0.02 ml X g-1 X h-1 (brain cortex), and 1.107 +/- 0.12 ml X g-1 X h-1 (cerebellum). The permeability constant for hypotensive animals (arterial blood pressure of 40 +/- 5 mmHg), has been determined in 0.473 +/- 0.03 ml X g-1 X h-1 (brain cortex), and 0.608 +/- 0.06 ml X g-1 X h-1 (cerebellum). During hypotension there is a marked decrease in the permeability constant of 86Rb at the blood-brain barrier of rats.

Animals↗