PubMed Health⌕ Search

Biomedical subjects

C Lindquist

Publications and source records attributed to C Lindquist.

At least 19 recordsLinked to original sources
PubMed1992

Biomechanical effect of a two-segment anterior cruciate ligament graft with separate femoral attachments and differing levels of prescribed load sharing.

The objective of this study was to analyze the biomechanical effect of varying the level of prescribed load sharing between two segments of an anterior cruciate ligament (ACL) graft, and of separating the femoral attachments of these segments. Total anterior-posterior (AP) laxity was measured using an instrumented spatial linkage. Forces in graft segments were measured using buckle transducers. The two-segment graft was formed using the middle third of the patellar tendon with bone blocks and a synthetic augmentation device. Proximal fixation was obtained using a fixture which allowed changing the individual locations of the femoral attachments of the tendon and augmentation segments. Distal fixation was achieved using a force-setting device which allowed the loads in each segment to be set to prescribed levels. Total graft force, load sharing, and total AP laxity were recorded during the application of 100-N AP tibial loads at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 110 degrees flexion, for various combinations of load sharing set at extension and locations of femoral attachment sites. The load sharing, total graft force, and AP laxity during AP loading at the five test flexion angles were not significantly affected by changing the prescribed level of load sharing set at extension for a given femoral attachment configuration. However, varying the separate hole locations of the graft segments for a given level of load sharing significantly affected load sharing, total graft force, and AP laxity. If the tendon graft was located posteriorly (on the medial surface of the lateral femoral condyle) and the augmentation segment proximally, the augmentation carried a greater portion of the total force in flexion. If the augmentation segment was changed to a more posterosuperior location and the tendon posteroinferior, the tendon carried a higher percentage of the total force in flexion. AP laxity in most reconstruction states was significantly greater than in the normal joint with an intact ACL. The nature of the load sharing between the graft segments under AP tibial load over the flexion range can be controlled by the appropriate choice of the segments' femoral attachment locations.

Analysis of Variance↗
PubMed1992

Radiosurgery.

Explore the source record for details and available documents.

Adolescent↗
PubMed1992

Radiation-induced edema after radiosurgery for pontine arteriovenous malformation. A case report and detection by magnetic resonance imaging.

A 29-year-old woman, who had undergone stereotactic radiosurgery for a pontine arteriovenous malformation, experienced sudden onset of facial nerve palsy with trigeminal nerve disturbance 19 months after irradiation. Magnetic resonance imaging revealed significant radiation-induced edema surrounding the nidus. Angiography demonstrated total obliteration of the arteriovenous malformation 24 months after irradiation. Further magnetic resonance imaging studies, performed 28 months after treatment, showed that, despite the persistence of symptoms, the radiation-induced edema had subsided.

Adult↗
PubMed1992

Long-term follow-up of radiosurgically treated arteriovenous malformations in children: report of nine cases.

Long-term follow-up results of nine children treated for cerebral arteriovenous malformation with a gamma unit are presented. Complete nidus obliteration was angiographically confirmed in six cases and significant decreases in arteriovenous malformation size were observed in the other three. There were no radiation-related deteriorations in physical or mental development. In seven patients who underwent endocrinological examination more than 3 years after irradiation, five were normal and the other two showed only low serum adrenocorticotropic hormone levels, which, however, did not necessitate replacement therapy. Neurodiagnostic imaging follow-up studies revealed no radiation-induced lesions in any of the nine cases.

Adolescent↗
PubMed1992

Long-term results of radiosurgery for arteriovenous malformation: neurodiagnostic imaging and histological studies of angiographically confirmed nidus obliteration.

Detailed follow-up results for 25 patients treated for cerebral arteriovenous malformation (AVM) with a gamma unit are presented. Complete nidus obliteration was angiographically confirmed in 16 (73%) of 22 cases receiving full-dose irradiation. There were no radiation- or AVM-related mortalities. However, we did experience one case of radiation-related morbidity and one of angiography-related mortality, the autopsy findings of which are discussed. Computed tomography scan and magnetic resonance imaging follow-up studies of radiosurgically treated AVMs indicated that increased enhancement of the nidus after contrast or gadolinium administration could persist even after obliteration of the AVM was angiographically confirmed.

Adolescent↗
PubMed1992

Clinical outcome of radiosurgery for cerebral arteriovenous malformations.

The clinical outcomes are described for 247 consecutive cases of arteriovenous malformation (AVM) treated with the gamma knife between April, 1970, and December 31, 1983. Headache resolved in 65 (66.3%) of the 98 patients presenting with this symptom and improved in an additional nine (9.2%). Of 59 patients admitted with seizures, 11 (18.6%) became seizure-free without anticonvulsant medication and an additional 30 patients (50.8%) became seizure-free with anticonvulsant medication. Pre-existing neurological deficits improved or totally disappeared following radiosurgery in 56.7% of affected cases. This improvement presumably occurred within the frame of the natural history. The protective effect of the ionizing beams against hemorrhage in incompletely obliterated AVM's is analyzed. To assess the rate of rebleeding, probability estimates were calculated using both the person-year method and the Kaplan-Meier life table. With the person-year method the actual rebleed rate is not too different from the values observed in the natural history of the disease (2% to 3%/yr). Analysis by Kaplan-Meier life-table estimates demonstrated a risk of nearly 3.7%/yr until 60 months after radiosurgery. Five years following treatment, the life table ends in a plateau which could be interpreted as an indication of decrease in the risk of hemorrhage. However, long flat regions at the right end of the life table do not imply that the real risk of rebleeding is negligible unless a large number of patients have been followed well into or beyond the flat region.

Cerebral Hemorrhage↗
PubMed1991

Gamma knife surgery for cerebral metastasis.

Twenty-six cerebral metastatic tumours treated with the Gamma knife employing a large single dose were followed by repeated clinical and CT examinations. In most cases Gamma knife surgery was the only treatment. The follow up time has been longer than 6 months with a median follow up of 9 months. In all but one of the cases a remarkable progressive shrinkage of the tumour started 2-4 months after the therapy. The therapeutic results indicate that radiosurgery used even as the only form of treatment is the best treatment alternative for cerebral metastasis presently available.

Aged↗
PubMed1991

Colocalization of neurotransmitters analyzed by in situ hybridization.

In situ hybridization and Northern blot analysis has been used to analyse in some detail the localization and regulation of the messenger molecules adrenaline, noradrenaline and neuropeptide tyrosine (NPY) within cells of the sympathetic nervous system and the adrenal medulla. In the rat adrenal gland, a novel NPY containing population of ganglion cells was found. Synthetic oligonucleotide probes complementary to mRNA coding for the catecholamine synthesizing enzymes phenylethanolamine N-methyltransferase (PNMT), tyrosine hydroxylase (TH) and NPY were used to analyse the regulation of these genes following administration of the catecholamine depleting drug reserpine. Twenty-four hours after a single dose of reserpine, a differential regulation of PNMT, TH and NPY was found. Thus, a dramatic decrease in PNMT mRNA was observed in the adrenal medulla. In contrast, mRNA for both TH and NPY exhibited an increase. Different regulatory mechanisms may thus operate for these three compounds coexisting in chromaffin cells of the adrenal medulla. The regulation of enzymes and peptides was also studied in human sympathetic ganglia. After brief electrical preganglionic stimulation of thoracic ganglia in humans, in situ hybridization was performed with synthetic oligonucleotide probes complementary to TH, dopamine beta-hydroxylase (DBH) and NPY mRNA respectively. A several fold increase in all three mRNAs was found in the principal ganglion cells. The results point to a very rapid regulation of genes involved in signal transmission in the sympathetic nervous system of humans. The results also suggest a novel way to define neuronal projections by visualizing increases in mRNA levels following electrical stimulation.

Adrenal Glands↗
PubMed1991

Functional neurosurgery--a future for the gamma knife?

The Gamma Knife is currently the only radiosurgical device which has been used in functional neurosurgery. This mode of utilization is possible because the instrument can make lesions in normal brains with a volume as small as 50 mm3. The experience of functional radiosurgery accumulated at the Karolinska Institute over 21 years is reviewed, and the possible implications of the new developments in imaging techniques for the future of functional radiosurgery are considered. The review covers gamma thalamotomy for pain and tremor, radiosurgery for trigeminal neuralgia, gamma capsulotomy for severe anxiety and obsessive-compulsive neurosis, and Gamma Knife surgery for focal epilepsy. The important role of stereotactic MRI localization in functional radiosurgery is pointed out, and a preliminary report of the recent experience with stereotactic magnetoencephalography combined with stereotactic MRI for physiological and anatomic target localization is given. It is concluded that functional radiosurgery should only be performed with radiation of very small volumes of brain, as the very high doses required would be devastating if delivered to even small volumes.

Adult↗
PubMed1990

Maxillofacial fractures related to work accidents.

Work-related maxillofacial fractures were studied retrospectively over a six-year period. There were 98 cases accounting for 4.5% of all facial bone fractures treated in our hospital between 1981 and 1986. Of the patients, 89.8% were male. The mean age of the injured was 36.4 years. The incidence of work-related maxillofacial fractures was 0.37 per 1000 workers. Most of the injuries (66%) occurred in factories and construction work. Such work was associated with an to 15 times higher risk of maxillofacial fracture than service and office work. Of the fractures, 20.4% were sustained on the way to or coming from work. At the place of work, the commonest causes of injury were blows from objects or falls from a height (70%). On the way to or coming from work, the aetiological factor was most often a traffic accident. Assault and battery had caused facial bone fractures in 11.2% of cases. Fifty-five patients with midface and 45 patients with mandibular fractures were found, of these, 8 patients had bimaxillary fractures. In 6 cases, only dentoalveolar fractures were found. Of the patients, 55.1% were treated operatively. Sixty-six patients were hospitalized, the mean length of hospital stay being 3.2 days (range 1-12 days).

Accidents, Occupational↗
PubMed1989

Rapid increase in enzyme and peptide mRNA in sympathetic ganglia after electrical stimulation in humans.

Thoracic ganglia in humans were studied after electrical, preganglionic stimulation using in situ hybridization with synthetic oligonucleotide probes against the catecholamine-synthesizing enzymes tyrosine hydroxylase (EC 1.14.16.2) and dopamine beta-hydroxylase (EC 1.14.17.1) and neuropeptide tyrosine. Immunohistochemical analysis was also performed. Following short peroperative stimulation a severalfold increase in all three mRNAs was found in principal ganglion cells, whereas no definite changes could be detected in enzyme or peptide levels with immunohistochemistry. The results suggest a very rapid and sensitive regulation of genes involved in signal transmission in the sympathetic nervous system of humans. Moreover, they indicate that electrical stimulation of neurons and/or pathways combined with in situ hybridization may be used as a method to define neuronal projections by visualizing increases in mRNAs for transmitter enzymes and/or peptide in target cells.

Autoradiography↗
PubMed1989

Gamma knife surgery for recurrent solitary metastasis of a cerebral hypernephroma: case report.

Gamma knife surgery employing a central dose of 70 Gy and a peripheral dose of 25 Gy caused progressive necrosis and shrinkage of a recurrent solitary metastasis of a cerebral hypernephroma, as verified by computed tomographic scan 2 and 4 months after treatment. Gamma knife surgery was an effective palliative treatment for this cerebral metastasis and was an alternative to craniotomy with microsurgical removal.

Adult↗
PubMed1989

Cerebral blood flow and metabolism during adenosine-induced hypotension in patients undergoing cerebral aneurysm surgery.

The effects of adenosine-induced hypotension on cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), and cerebral lactate production, together with systemic haemodynamics, were studied in 10 patients undergoing cerebral aneurysm surgery in neurolept anaesthesia with controlled hyperventilation. CBF changes were determined in six of the patients with a retrograde thermodilution technique in the jugular vein. Hypotension was induced with a continuous infusion of adenosine in the superior vena cava. The dose range was 0.06-0.35 mg/kg/min, and this caused a 42% reduction in mean arterial blood pressure (MABP) from 79 +/- 4 to 46 +/- 1 mmHg (10.5 +/- 0.5 to 6.1 +/- 0.1 kPa) through a profound reduction in systemic vascular resistance (SVR), which amounted to 61%. No significant change occurred in CBF. Whole body AV-difference of oxygen was decreased by 37%, and cerebral AV-difference by 28%, corresponding to reductions in whole body oxygen uptake and CMRO2 of 16 and 17%, respectively. Cerebral AV-difference of lactate did not change. In the posthypotensive period MABP was increased by 10%, together with a minor increase in CBF (15%). It is concluded, that adenosine-induced hypotension at MABP levels between 40-50 mmHg (5.3-6.7 kPa) does not affect cerebral oxygenation unfavourably, and may even offer a protective effect by reducing cerebral oxygen demand. The slight CBF increase in the posthypotensive period was probably secondary to an increase in MABP together with a blunted autoregulation, but in no case was this effect considered to be harmful for the patient.

Adenosine↗
PubMed1989

Electrophysiological aid in high thoracic sympathectomy for palmar hyperhidrosis.

High upper thoracic sympathectomy using microsurgical techniques aided by electrical stimulation of the sympathetic chain is described. Use of the microscope facilitates identification and dissection of the sympathetic chain and minimizes the risk of pleural damage. Electrical stimulation of the sympathetic chain establishes the correct functional level for surgical excision. At the correct level, the threshold for piloerection, sudomotor response, and decrease in blood flow of the ipsilateral hand to electrical stimulation was minimal, and a six-fold increase in stimulus current causing current spread was required to dilate the ipsilateral pupil. After identification of the proper level, surgical excision can be done without risking postoperative Horner's syndrome. Excision of the appropriate ganglia and intervening sympathetic chain with placement of surgical clips on the proximal and distal nerve stumps provides tissue for histological analysis, decreases the opportunity for regeneration, and facilitates localization on postoperative x-rays.

Electric Stimulation↗
PubMed1988

Use of mannitol during neurosurgery: interpatient variability in the plasma and CSF levels.

An i.v. infusion of mannitol was given over 15 min to 12 patients before they underwent intracranial surgery under general anesthesia. Samples of blood, CSF and urine were taken over 4 h. Mannitol disappeared from plasma in a bi-exponential manner. The mean maximal plasma concentration was 4.08 mg/ml at 15 min, and at 4 h it had declined to 0.53 mg/ml. The mean distribution rate constant was 11.2 h-1, corresponding to a plasma distribution half-life of 0.11 h. The mean elimination rate constant was 0.41 h-1, the plasma half-life was 2.2 h, the central distribution volume was 16.3 l, and total plasma clearance was 100.4 ml/min. The mean concentration of mannitol in CSF during the 4 h period increased up to 0.10 mg/ml. There were marked interindividual differences in the concentration ratio blood/CSF, and the CSF concentration varied 7.5 fold between patients. Optimal use of mannitol during neurosurgery requires further prolonged study of its pharmacokinetics.

Adult↗