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Biomedical subjects

B A Bell

Publications and source records attributed to B A Bell.

At least 19 recordsLinked to original sources
PubMed1998

Posterior fossa meningiomas: surgical experience in 52 cases.

BACKGROUND: Early reports of the surgical management of posterior cranial fossa meningiomas (PCFM) yielded poor results with high rates of mortality and morbidity. With the advent of modern neuroimaging and microsurgical techniques the results of surgery have improved markedly, but despite these advances removal of these lesions remains a challenge. METHODS: The results of the surgical treatment of PCF meningiomas were examined with the aim to identify particular features associated with increased mortality and morbidity. RESULTS: Of 713 patients with meningioma, 52 patients were identified with PCFM. Total macroscopic excision was achieved in 44 patients (84%). Postoperative complications occurred in 28 patients (54%) with permanent sequelae in 18 (35%). There were no mortalities in the immediate postoperative period. Follow-up ranged from 14 to 174 months (mean 42), tumour has recurred in 11 patients (21%) with a long-term mortality of 11%. At their latest follow-up 41 (79%) of patients achieved Glasgow outcome scores of 4 or 5. CONCLUSIONS: Total excision of tumour should remain the goal of treatment in patients with PCFM. Despite the recent advances in preoperative planning and surgical techniques, the morbidity associated with surgery remains significant. Notwithstanding, the majority of patients achieve a good outcome with surgical treatment.

Adolescent↗
PubMed1998

Wrapping of solitary ruptured intracranial aneurysms, outcome at five years.

Previous follow up studies of patients who have had ruptured intracranial aneurysms treated by a wrapping technique have largely been in the pre-microsurgical era. Our objective was to ascertain whether wrapping aneurysms with the aid of the operating microscope provides protection against rebleeding in the short and long term. The study involved retrospective analysis of patients with ruptured aneurysms treated by wrapping over a six-year period. Twenty-nine patients were identified with wrapped aneurysms, of these 15 had wrapping of a solitary ruptured aneurysm, the remainder were excluded because of clip/wrap combination, multiple aneurysms, and unruptured aneurysms. Of the 15 patients who had a solitary ruptured aneurysm wrapped, none had rebled at one year follow up. One patient died of a myocardial infarction at 4 years, the remaining 14 patients had no episodes of rebleeding with all patients achieving Glasgow outcome scores of four or five at 5 years follow-up. Although surgical clipping of intracranial aneurysms is the definitive method of treatment, our findings suggest that wrapping of ruptured intracranial aneurysms with the aid of the operating microscope confers good protection against both early and late rebleeding in those cases considered 'unclippable'.

Adult↗
PubMed1998

Cerebral blood flow and tissue oxygenation monitoring during aneurysm surgery.

Regional cerebral blood flow may be compromised during aneurysm surgery. This may occur during vessel occlusion by temporary clips or result from malposition of the definitive aneurysm clip. Post-operative cerebral vasospasm may also compromise cerebral blood flow and is an important cause of morbidity. This study addresses the need for a sensitive indicator of compromised cerebral function during aneurysm surgery by measuring brain tissue oxygenation and laser Doppler flow. Four patients were studied, all of whom had ruptured middle cerebral artery aneurysms. Brain tissue oxygenation measurements were made with a closed polarographic sensor placed in the ipsilateral cerebral hemisphere to the aneurysm. A laser Doppler flow probe and intracranial pressure monitor were similarly placed. The data were simultaneously processed using multimodality recording monitoring. The monitoring was continued during the post-operative period and totalled over 190 hours. Data were analysed as specific events and as trends. Initial tissue oxygen levels were low but improved in all cases as the intracranial pressure was reduced. This effect was independent of the cerebral perfusion pressure. Laser Doppler flow provided an indicator of compromised brain function and tissue oxygenation an indicator of established ischemia.

Aged↗
PubMed1996

Wylie McKissock--reminiscences of a commanding figure in British neurosurgery.

Wylie McKissock founded the neurosurgical unit at Atkinson Morley's Hospital which has grown to become the largest neurosurgical unit serving London. He trained a large number of British and overseas neurosurgeons, six of whom achieved presidency of the Society of British Neurological Surgeons. McKissock made a great contribution to the development of British neurosurgery, and reminiscences from some of his trainees and colleagues are collected together in this article.

History, 20th Century↗
PubMed1996

Application of magnetic resonance neurography in the evaluation of patients with peripheral nerve pathology.

Currently, diagnosis and management of disorders involving nerves are generally undertaken without images of the nerves themselves. The authors evaluated whether direct nerve images obtained using the new technique of magnetic resonance (MR) neurography could be used to make clinically important diagnostic distinctions that cannot be readily accomplished using existing methods. The authors obtained T2-weighted fast spin-echo fat-suppressed (chemical shift selection or inversion recovery) and T1-weighted images with planes parallel or transverse to the long axis of nerves using standard or phased-array coils in healthy volunteers and referred patients in 242 sessions. Longitudinal and cross-sectional fascicular images readily distinguished perineural from intraneural masses, thus predicting both resectability and requirement for intraoperative electrophysiological monitoring. Fascicle pattern and longitudinal anatomy firmly identified nerves and thus improved the safety of image-guided procedures. In severe trauma, MR neurography identified nerve discontinuity at the fascicular level preoperatively, thus verifying the need for surgical repair. Direct images readily demonstrated increased diameter in injured nerves and showed the linear extent and time course of image hyperintensity associated with nerve injury. These findings confirm and precisely localize focal nerve compressions, thus avoiding some exploratory surgery and allowing for smaller targeted exposures when surgery is indicated. Direct nerve imaging can demonstrate nerve continuity, distinguish intraneural from perineural masses, and localize nerve compressions prior to surgical exploration. Magnetic resonance neurography can add clinically useful diagnostic information in many situations in which physical examinations, electrodiagnostic tests, and existing image techniques are inconclusive.

Adolescent↗
PubMed1995

Improving the acceptability of high-dose radiotherapy by reducing the duration of treatment: accelerated radiotherapy in high-grade glioma.

Radiotherapy, although clearly beneficial in patients with high-grade glioma, is largely palliative, and a protracted course of treatment may not be the most appropriate approach in the context of limited survival. We therefore assessed the feasibility, toxicity and survival results of a short accelerated radiotherapy regimen given twice daily over a period of 3 weeks. A total of 116 patients with high-grade glioma were treated with radiotherapy in a prospective study using an accelerated fractionation regimen. The total dose of 55 Gy was given in 32-36 fractions of 1.72-1.53 Gy, twice daily 5 days a week, with a minimum 6 h interval between fractions. Toxicity was assessed using Karnofsky performance status scale and in the later part of the study with the Barthel index. Survival data were compared with a control group treated with 60 Gy in 30 daily fractions in a previous MRC study, matched for known prognostic factors. The median survival of 116 patients treated with accelerated radiotherapy was 10 months. Survival comparison of accelerated patients with matched controls treated with conventional fractionation demonstrated a hazard ratio of 1.13 (95% confidence interval 0.85-1.51; P = 0.39). Early treatment toxicity was acceptable, with only seven patients developing transient decrease in performance status. The accelerated radiotherapy regimen was logistically feasible and acceptable to patients, carers and staff. Treatment time was reduced without apparent increase in early toxicity and there was no loss of survival benefit. The effectiveness and convenience of a short accelerated regimen makes this a suitable alternative to a 6 week course of radiotherapy in patients with high-grade glioma. However, a full randomised trial comparing conventional and accelerated radiotherapy may be required as proof of equivalence.

Actuarial Analysis↗
PubMed1995

Modulation of Ca(2+)-dependent currents in metabolically stressed cultured sensory neurones by intracellular photorelease of ATP.

1. The whole cell recording technique was used to study high voltage-activated Ca2+ currents and Ca(2+)-activated Cl- tail currents from cultured neonatal dorsal root ganglion neurones of the rat which were metabolically stressed. The neurones were metabolically stressed with 2-deoxy-D-glucose (5 mM) for 30 min to 3 h. The aim of the project was to examine the actions of intracellular photorelease of ATP on the properties of Ca(2+)-dependent currents and determine if the effects of metabolic stress could be reversed. 2. The mean duration of Ca(2+)-activated Cl- tail currents was significantly increased by metabolic stress and this effect was reversed by intracellular photorelease of approximately 300 microM ATP. Intracellular photolysis of 'caged' photolabile compounds was achieved with a xenon flash lamp. 3. Intracellular photorelease of ATP and adenosine 3':5'-cyclic monophosphate (cyclic AMP) (about 40 microM) also accelerated the inactivation of high voltage-activated Ca2+ currents evoked by 500 ms depolarizing step commands from -90 mV to 0 mV. This effect was prevented by intracellular application of the calcineurin (protein phosphatase-2B) inhibitor cyclosporin A (14 nM) and cyclophilin A (50 nM) either applied together or individually. In contrast the protein phosphatase 1 and 2A inhibitor, calyculin A, increased voltage-activated Ca2+ currents, but failed to prevent enhanced inactivation induced by intracellular photorelease of ATP. Intracellular photorelease of ATP had no effect on Ca2+ currents recorded from control neurones which were not metabolically stressed and supplied with glucose and ATP in the extracellular and patch pipette solutions respectively. 4. In conclusion, intracellular photorelease of ATP increases the decay of Ca2+-activated Cl- tail currents in metabolically stressed neurones suggesting that the efficiency of intracellular Ca2+ buffering was improved. Additionally, an ATP/cyclic AMP-dependent component of high voltage-activated Ca2+current inactivation which is mediated by calcineurin is revealed following photolysis of 'caged' ATP or cyclic AMP in metabolically stressed neurones.

Adenosine Triphosphate↗
PubMed1995

Comparison of rates of infection of two methods of emergency ventricular drainage.

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.

Adolescent↗
PubMed1995

Timing of postoperative intracranial hematoma development and implications for the best use of neurosurgical intensive care.

This study records the incidence and timing of postoperative hematomas in neurosurgical patients and analyzes the best use of neurosurgical intensive care. In 2305 patients undergoing freehand or stereotactic biopsy, elective or emergency craniotomy, or posterior fossa surgery, 50 (2.2%) developed a hematoma. Clinical deterioration as a result of postoperative hematoma occurred within 6 hours of surgery in 44 patients and more than 24 hours after surgery in six patients. Although patients undergoing posterior fossa surgery or emergency craniotomy warrant longer periods of intensive-care observation, patients having elective supratentorial operations can safely be transferred to a neurosurgical ward for observation, provided they have regained their preoperative neurological status by 6 hours postsurgery.

Cerebral Hemorrhage↗
PubMed1994

Microcephaly with large anterior fontanelle, generalized convulsions, micropenis, and distinct anomalies of the hands and feet. Another example of Wiedemann syndrome?

Wiedemann et al. (1985) described a rare syndrome characterised by microcephaly, psychomotor delay, short stature, short fingers and toes with stubby broad thumbs and halluces. Unilateral undescended testis, inguinal hernias, scrotal hypoplasia, and micropenis were also features. They described two males, first cousins, whose mothers and maternal grandfather had short broad thumbs and halluces. We report a male with identical features whose parents were normal. This is only the second report of this syndrome. Autosomal or X-linked dominant inheritance is most likely.

Abnormalities, Multiple↗
PubMed1994

Effects of metabolic blockers on Ca(2+)-dependent currents in cultured sensory neurones from neonatal rats.

1. The whole cell variant of the patch clamp technique was used to record high voltage-activated Ca2+ currents and Ca(2+)-activated Cl- tail currents from cultured neonatal rat dorsal root ganglion neurones. The aim of the project was to use these currents as physiological indices of intracellular Ca2+ regulation under control conditions and in the presence of metabolic inhibitors. 2. Carbonyl cyanide p-trifluoromethoxyphenylhydrazone (5 microM) and sodium cyanide (1 microM) inhibited Ca2+ currents within 20 s, even when ATP was present in the patch pipette solution, suggesting a direct action on Ca2+ channels. These metabolic inhibitors did not affect Ca2+ current 'run down' or inactivation kinetics. 3. Cultured neonatal dorsal root ganglion neurones of the rat were relatively insensitive to the removal of glucose and ATP from the recording solutions for up to 3 h. These data suggest that the Ca2+ homeostatic mechanisms in these cells are highly resistant to metabolic insult. 4. However 2-deoxy-D-glucose (5 mM) in the extracellular recording medium with no ATP or glucose present did prolong the deactivation time of Ca(2+)-activated Cl- tail currents and increase the total charge flow following activation of a 500 ms voltage-activated Ca2+ current. This effect was prevented by inclusion of D-fructose 1,6-diphosphate (500 microM) in the patch pipette solution. 5. We conclude that some agents used to induce chemical hypoxia, such as carbonyl cyanide p-trifluoromethoxyphenylhydrazone and sodium cyanide, may interact directly with voltage-activated Ca2+ channels and are therefore not appropriate for use in studying disturbed neuronal Ca2+ homeostasis. However, the use of 2-deoxy-D-glucose in the absence of glucose and ATP does represent a model of disturbed Ca2+ homeostasis in cultured dorsal root ganglion neurones. In this study we have combined the whole cell recording technique with cultured neurones under conditions which produce a degree of metabolic stress as reflected by prolonged Ca(2+)-activated Cl- tail currents. The reduced efficiency of handling of intracellular Ca2+ loads may be an important factor contributing to the onset of neuronal damage during hypoxia and ischaemia.

Adenosine Triphosphate↗
PubMed1994

Calcitonin gene-related peptide reduces brain injury in a rat model of focal cerebral ischemia.

BACKGROUND AND PURPOSE: Calcitonin gene-related peptide is an endogenous vasodilating neuropeptide with a dense concentration in the trigeminocerebrovascular system. It is hypothesized that depletion of this peptide contributes to delayed cerebral ischemia after subarachnoid hemorrhage and that an exogenous supply of calcitonin gene-related peptide will augment ischemic cerebral blood flow and reduce neuronal injury. METHODS: In this study we have investigated the effect of an intravenous infusion of calcitonin gene-related peptide (100 ng/kg per minute), started 1 hour before and continued throughout 4 hours of focal cerebral ischemia, on cerebral blood flow and the volume of brain injury in a rat model of middle cerebral artery occlusion. RESULTS: Calcitonin gene-related peptide produces a significant improvement in ischemic cerebral blood flow (32 +/- 2 compared with 13 +/- 2 mL/100 g per minute in the controls; t = 6.92, P < .0001) with a concomitant reduction in the volume of ischemic brain injury (102 +/- 22 compared with 234 +/- 19 mm3; t = 4.47, P < .001). CONCLUSIONS: These findings lend support for the potential use of this peptide in the prophylactic treatment of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

Animals↗
PubMed1994

Prolactinomas in men masquerading as invasive skull base tumours.

Four giant prolactin-secreting tumours invading the skull base are described. All of them occurred in men. The presenting features were sufficiently diverse to be clinically misleading. We advocate the estimation of prolactin levels before embarking on complicated skull base surgery in men where doubt remains regarding the diagnosis after clinical and radiological study.

Adolescent↗
PubMed1994

Subgaleal haematoma resulting in extradural compression following craniotomy. Report of two cases.

We describe two patients who underwent intracranial aneurysm surgery and developed postoperative subgaleal haematomas which, in the presence of an unfixed bone flap, resulted in significant extradural compression and a marked clinical deterioration. The application of a pressure dressing to tamponade a developing scalp haematoma is unwise unless the bone flap has been rigidly fixed in place.

Adult↗