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Biomedical subjects

L Symon

Publications and source records attributed to L Symon.

At least 145 records · Page 8Linked to original sources
PubMed1985

The management of cerebral arteriovenous malformations.

The presentation of 129 cases of cerebral angioma is reviewed. There were 4 main methods of presentation: haemorrhage, epilepsy, deteriorating neurological signs and headache. The fifth common method of presentation, heart failure, almost exclusively confined to infants, was not seen in the current series which includes no paediatric cases. Standard techniques of investigation principly angiography and CT scanning were used in diagnosis and the current indication for surgery was haemorrhage. The mortality rate per haemorrhage in the series considered in natural terms was 3.6%, neurological deficit as a result of the haemorrhage, either major or minor, occurred in a total of 8%, 4% each. Complete excision of the angioma was performed in 69 cases, although in 3 of these it was necessary to reoperate following postoperative angiography which was then used again to confirm total removal. There was 1 death in this series of radical removals, a mortality rate of 1.5%. Six cases however, showed significant neurological deterioration postoperatively, a major morbidity of 8.7%. From the period of observation of these cases and the instance of haemorrhage the annual bleeding rate would appear to be 4.2%. From follow-up of our cases where the lesion was not completely removed the re-bleeding rate would appear to be 2.6%.

Adolescent↗
PubMed1985

Colloid cysts of the third ventricle. A review of 36 cases.

Thirty-six colloid cysts were treated from 1949 to 1983. There were 26 male and 10 female patients, ranging in age from 12 to 65 years old, 60% between 31 and 40 years. Headache or disturbed mental function was the most frequent complaint, papilloedema the most frequent sign. The patients were classified into 3 groups by symptoms and signs; Group I (17 patients): Headache, papilloedema and no neurological signs. Group II (6 patients): Fluctuating or progressive dementia. Group III: Twelve cases with "classical" features, episodic headache and drop attacks. One patient could not be classified in any of these groups. Seventeen of 36 patients were diagnosed by ventriculography, 19 patients were diagnosed by CT scan. CT scan was the most reliable diagnostic study, but was unavailable in the earlier part of the series. All patients have been operated by transventricular exposure of the right foramen of Munro with incision of the middle frontal gyrus in an antero-posterior linear manner. Twenty-five of 36 patients showed an excellent operative result, and nine had a good result, one of the 9 patients dying of an unrelated intracerebral haemorrhage 4 years after operation. Two patients had a poor result, characterized by memory loss and confusion. One of these died of an unknown cause 5 years after operation.

Adolescent↗
PubMed1985

A comparative study of the portable regional CBF monitor and the portable mean hemispheral CBF monitor: advantages and disadvantages in clinical practice.

CBF determination can provide additional valuable information which can be used in clinical practice to enhance our capabilities in patient evaluation. The initial techniques requiring intraarterial injections have been largely replaced by the noninvasive inhalation and intravenous methods. The recent refinement of microcomputers and the development of portable CBF monitors have made CBF determination a nontraumatic, dependable and easily repeatable examination at the patient's bedside. In this communication we compare a portable region CBF monitor and a portable mean hemispheral CBF monitor; we study their advantages and disadvantages in clinical practice. Emphasis is placed on the practical characteristics and the information provided by each monitor and its contribution to patient evaluation. Illustrative cases are presented.

Brain↗
PubMed1985

Mean hemispheral cerebral blood flow changes after craniotomy. Significance and prognostic value.

The effects of craniotomy on cerebral haemodynamics remains controversial from a study of the literature. This report represents our experience with respect to CBF changes within 10 days of surgery. Our objective was twofold, first to study the effect of craniotomy on the cerebral circulation and second to determine whether the CBF pattern at different post-operative intervals could provide useful prognostic information. A total of 135 CBF measurements were performed at the bedside of 36 patients; 19 patients with an assortment of intracranial tumours and 17 patients with intracranial aneurysm in different clinical grades. Our results indicate a significant rise in CBF in the immediate post-operative period averaging 18% of the pre-operative value. We believe this reflects a normal reaction of the cerebral vasculature to the inevitable disturbance of surgery. Furthermore, this hyperaemia may be of prognostic value as it was observed in 85% of the patients with tumour discharged without post-operative deficit and in 80% of the patients with aneurysms discharged in clinical grade 1 or 2. This is in sharp contrast with its development in only 16% of the patients with tumour discharged with post-operative deficit and 16% of the patients with aneurysm discharged in grade 3 or 4. The study adds to the direct clinical utility of CBF determination as a prognostic tool.

Adolescent↗
PubMed1985

The application of flash visual evoked potentials during operations on the anterior visual pathways.

Flash visual evoked potentials (F-VEP's) have been recorded in fifteen patients (thirty eyes) with anterior visual pathway compression lesions before, during and after the operation in relation to clinical visual testing. A grading system for the wide variety of abnormal F-VEP's has been established, based on changes in forty patients (eighty eyes). No significant correlation between change in F-VEP and visual acuity or visual field has been demonstrated. Intraoperative F-VEP's have been found to be sensitive to halothane and to surgical manipulation of the optic nerve and/or chiasm during dissection of the tumour. The technique is considered a useful means of identifying the optic pathway during operation and may assist in prevention of optic damage if the transphenoidal approach is used.

Adult↗
PubMed1985

The effects of halothane on somatosensory and flash visual evoked potentials during operations.

Intraoperative use of somatosensory evoked potentials (SEP's) to monitor intracranial aneurysm surgery and flash visual evoked potentials (F-VEP's) for parasellar surgery have been routinely employed in our clinic. We found that both EP modalities are sensitive to the changing concentration of our standard hypotensive agent, halothane. The prolongation of the N14-N20 interpeak latency to median nerve stimulation at the wrist, and prolongation of P100 latency with altered configuration of early VEP components to flash light stimulation, appear to be the results of direct pharmacological effects of the agent and not an effect of secondary hypotension. VEP is found easily abolished by halothane at a concentration of 2.0%, while the SEP is more resistant. Halothane is not ideal however when monitoring intraoperative VEP.

Adolescent↗
PubMed1985

Syringoperitoneal shunt for treatment of cord cavitation.

A series of twenty-nine patients with cord cavitation were treated by syringoperitoneal shunt. Twenty-two of them showed improvement after operation, five were unchanged and two worsened. Operation was performed in patients with post-traumatic cystic myelopathy, idiopathic syringomyelia, intramedullary tumours associated with cysts, and patients who had developed cystic myelopathy in association with spinal arachnoiditis. Pain improved in twenty patients, sensory symptoms and signs in eleven and weakness in ten.

Adolescent↗
PubMed1985

Relationship between hemispheric cerebral blood flow, central conduction time, and clinical grade in aneurysmal subarachnoid hemorrhage.

The relationship between central conduction time (CCT) and hemispheric cerebral blood flow (CBF) has been examined in 20 patients presenting with subarachnoid hemorrhage. A total of 63 combined CCT/CBF recordings were performed at various times throughout the hospital course of these patients, and the findings were correlated to clinical status. The initial-slope index of the CBF (CBF isi) was found to correlate well with clinical grade, and a gradation in flow was noted between the different neurological grades. Patients in Grades I and II (Hunt and Hess classification) had the highest flows (mean CBF isi = 47.2 +/- 8.1); Grade III patients had intermediate flows (mean CBF isi = 39.6 +/- 7.8); and Grade IV patients had the lowest flows (mean CBF isi = 32.0 +/- 6.4). While CCT tended to become increasingly prolonged with worsening grade, a significant difference could not be demonstrated between Grade I, II, and III patients. Only when Grade IV status was reached was the CCT significantly prolonged. When CBF isi and CCT were examined, a threshold relationship was noted between CBF isi and CCT prolongation. At flow values above 30, little change was noted in CCT, and CCT remained in the normal range. However, at flow values below 30, CCT became increasingly prolonged as blood flow diminished. The degree of CCT prolongation appeared to be directly proportional to the degree of blood flow diminution at flows below threshold.

Adult↗
PubMed1985

CBF and time thresholds for the formation of ischemic cerebral edema, and effect of reperfusion in baboons.

Ischemic cerebral edema has been studied in 41 baboons, with regional cerebral blood flow (CBF) determined by hydrogen clearance, and edema measured by microgravimetry. A threshold of ischemia has been identified for baboon cortex and subcortical white matter, which has to be crossed before edema formation begins. This threshold is 40.5% of normal CBF in cortex, and 34.4% of normal flow in subcortical white matter. A time threshold has also been determined, and the baboon brain can withstand 30 minutes of ischemia of the middle cerebral artery without significant edema formation. Reperfusion of ischemic brain has no effect on tissue water if the ischemic flow and time thresholds have not been crossed. Reperfusion of cortex, where water has begun to accumulate, exacerbates the water accumulation in proportion to the extent of the reperfusion. If these results are applicable to man, restoration of flow should not be attempted after an ischemic insult that reduces flow to less than 40% of normal unless it can be accomplished within 30 minutes of the insult. Provided CBF can be restored to above the 40% threshold within 30 minutes, reversal of the neurological deficit and prevention of ischemic edema can be expected.

Animals↗
PubMed1985

Radical excision of craniopharyngioma. Results in 20 patients.

A series is presented of 20 craniopharyngioma patients who were treated between 1977 and 1981. All 20 cases underwent radical tumor resection via a frontotemporal craniotomy, with a concomitant temporal tip resection. All operations were performed by the senior author. The operative mortality rate was 5%, and the major morbidity rate 22.2%. The average follow-up period was 3.1 years. The role of radical surgical extirpation in adults is emphasized: the results compare favorably with the current radiotherapeutic and more conservative surgical statistics.

Adolescent↗
PubMed1984

Arteriovenous malformations of the spinal cord.

The operative experience in Zürich of forty-one cases of spinal AVM with major intramedullary components showed that it was possible, with the aid of precise microsurgical techniques, to remove completely 60% of these lesions with improvement, or, at least, without deterioration in neurological condition. A further 12% could be apparently effectively palliated by subtotal removal. Radical surgery may be justified in patients with irreversible neurological deficits to treat pain and to prevent fatal SAH. The best results have generally been obtained in patients with less severe neurological deficits and with lesions in the cervical region rather than the thoracolumbar region. The natural history of intramedullary spinal AVMs--that of deterioration after recurrent haemorrhage--is analogous to that of intracranial aneurysms--and the need for earlier diagnosis and for early preventive surgery is the same for both. It would, perhaps, be preferable to treat all cases of spinal AVM by transvascular occlusion to obviate the risk of open surgery and of spinal deformity, but some AVMs will remain impossible to treat by this means and the long term results of embolization still require full analysis before it can be accepted as definitive treatment. Comprehensive and exact superselective spinal angiography is a mandatory prerequisite to surgery and preoperative partial embolization may facilitate operation considerably in the future. However, even the most careful angiographic studies do not always totally define the lesion and the surgeon must be prepared to find unexpected vascular relationships at operation. A simple classification of intramedullary and mixed extra/intramedullary lesions is described. The experiences with dural arteriovenous malformations in Queen Square again show that the best results are obtained in patients who have mild or moderate neurological deficit preoperatively. There is no doubt that progressive neurological deficits finally become irreversible and it is therefore clear that once the diagnosis is suspected, it should be definitively established and operation should follow immediately. The prime, indeed the only, necessary investigation is selective spinal angiography, which demands a high degree of radiological skill and experience, but given these prerequisites, may be performed with little hazard. While embolization of these lesions is possible, the simple surgical disconnection of the nidus of the shunt from the coronal venous plexus is effective in most cases, apparently permanently, and is substantially without risk.

Adolescent↗
PubMed1984

Extracellular pH, potassium, and calcium activities in progressive ischaemia of rat cortex.

We measured the relationships between changes in extracellular pH (pHe), potassium (Ke), and calcium (Cae) activities and DC potential (DCe) in progressive ischaemia of rat cerebral cortex. pHe and Ke, or Cae and Ke, were measured at the same point simultaneously, using triple-barrelled, double-ion-sensitive microelectrodes. Ischaemia was produced using bilateral carotid artery occlusion and hypotension in rats under 50% N2O-0.4% halothane anaesthesia. Unilateral carotid artery occlusion did not affect blood flow, but bilateral occlusion reduced flow to approximately 40% of normal. Autoregulation of blood pressure (BP) changes was lost after bilateral occlusion, and so progressive hypotension produced a linear decrease in flow. pHe began to decrease at high levels of flow (30-35 ml 100 g-1 min-1) and showed stepwise acidotic shifts with reductions in BP. Ke was affected at flows of approximately 15 ml 100 g-1 min-1, during which time it was critically dependent on BP. When Ke reached 6 mM, it increased rapidly to 40 mM and was associated with a negative shift in DCe. When Ke reached approximately 10 mM, Cae decreased rapidly to approximately 0.1 mM. pHe had reached 6.87 when Ke increased rapidly and showed a transient alkalotic shift of approximately 0.14 units at that time. Possible mechanisms for the sequence of ion changes described are discussed.

Animals↗
PubMed1984

Cerebral extracellular calcium activity in severe hypoglycemia: relation to extracellular potassium and energy state.

The changes in extracellular Ca2+ (Cae) and K+ (Ke) activities were studied in the rat brain during insulin-induced hypoglycemia. At about the time of onset of isoelectric EEG in severe insulin-induced hypoglycemia (300-g male Wistar rats under 70% N2O anaesthesia), there was an increase in Ke which, at approximately 13 mM, was associated with a fall in Cae. Ke peaked at 48 +/- 12 mM, and Cae at 0.18 +/- 0.28 mM. This ion change began to normalise, but before recovery was complete a second ion change, of magnitude similar to that of the first, occurred from which the cells did not recover. The Cae recovered to only 66% of normal in the time available before the second depolarisation. Measurements on brains frozen at different stages during the sequence of ion changes revealed that ATP and phosphocreatine (PCr) concentrations and energy charge (EC) were not reduced before the first depolarisation. During the first depolarisation there was a 72% decrease in PCr and a 37% fall in ATP level, leading to a 23% drop in EC. These levels decreased further by the 10th minute of isoelectricity , but only the fall in ATP concentration was significant. The results indicate that the first ion change was a spreading depression and that cellular energy state was not the only factor in determining the response of tissue in the early stages of the comatose state.

Animals↗
PubMed1984

Comparison of the effects of ischaemia on early components of the somatosensory evoked potential in brainstem, thalamus, and cerebral cortex.

In 14 ventilated, normocapnic baboons anaesthetised with alpha-chloralose, local CBF (hydrogen clearance) and the amplitude and latency of local components of the somatosensory evoked potential (SEP, median nerve stimulation) were measured bilaterally in ventrobasal thalamus (VPL), medial lemniscus (ML), and cerebral cortex before and during progressive ischaemia, produced by occlusion of the right middle cerebral artery and subsequent controlled reductions in mean systemic blood pressure (MSBP). The first significant reduction from control of the left cortical SEP amplitude occurred in the range of 30-40 mm Hg MSBP, but those of the VPL and ML responses only below 30 mm Hg; in the range of 20-30 mm Hg, the average SEP amplitudes in cortex, VPL, and ML were 8.6, 72.6, and 90.7% of control, respectively. In terms of local CBF, the cortical SEP threshold was in the range of 15-20 ml/100 g/min (as in previous work), that of VPL in the range of 10-15 ml/100 g/min, but the ML response was only markedly reduced below 10 ml/100 g/min. Thus, the differential ischaemic sensitivity of the SEP between the three regions was clearly demonstrated. These results indicate that as one descends the neuraxis, there is an increasing resistance of electrophysiological function to systemic hypotension, together with a decreasing threshold for local ischaemia.

Animals↗
PubMed1984

Granular cell tumor of the fifth cranial nerve: further evidence for Schwann cell origin.

Granular cell tumors arising from the cranial nerves are rare. We describe a granular cell neoplasm of the fifth cranial nerve in a 66-year-old male. Light microscopic appearances included rows and clusters of cells with small peripheral nuclei and abundant eosinophilic cytoplasm. Ultrastructurally the cytoplasm of these cells contained numerous dense bodies, multivesicular bodies and vacuoles. In some areas tumor cells were intermingled with myelinated and unmyelinated nerve fibers showing the same relationships as do Schwann cells and nerve fibers. The association between tumor cells and axon seen in this case lends further support to the putative Schwann cell origin of this neoplasm.

Aged↗
PubMed1984

Influence of severe hypoglycemia on brain extracellular calcium and potassium activities, energy, and phospholipid metabolism.

In the cerebral cortices of rats, during insulin-induced hypoglycemia, changes in the concentrations of labile phosphate compounds [ATP, ADP, AMP, and phosphocreatine (PCr)] and glycolytic metabolites (lactate, pyruvate, and glucose) as well as phospholipids and free fatty acids (FFAs) were studied in relation to extracellular potassium and calcium activities. Changes in extracellular calcium and potassium activities occurred at approximately the onset of isoelectricity . The extracellular calcium activity dropped from 1.17 +/- 0.14 mM to 0.18 +/- 0.28 mM and the potassium activity rose from 3.4 +/- 0.94 mM to 48 +/- 12 mM (means +/- SD). Minutes prior to this ionic change the levels of ATP, PCr, and phospholipids were unchanged while the levels of FFAs remained unchanged or slightly elevated. Following the first ionic change the steady-state levels of ATP decreased by 40%, from 2.42 to 1.56 mumol/g. PCr levels decreased by 75%, from 4.58 to 1.26 mumol/g. Simultaneously, the levels of FFAs increased from 338 to 642 nmol/g, arachidonic acid displaying the largest relative increase, 33 to 130 nmol/g. The first ionic change was followed by a short period of normalization of ionic concentrations followed by a sustained ionic change. This was accompanied by a small additional decrease in ATP (to 1.26 mumol/g). The FFA levels increased to 704 nmol/g. There was a highly significant negative correlation between the levels of FFAs and the energy charge of the tissue. The formation of FFAs was accompanied by a decrease in the phospholipid pool. The largest relative decrease was observed in the inositol phosphoglycerides, followed by serine and ethanolamine phosphoglycerides.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗