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Biomedical subjects

J R Madsen

Publications and source records attributed to J R Madsen.

At least 19 recordsLinked to original sources
PubMed1995

EEG prior to hemispherectomy: correlation with outcome and pathology.

Hemispherectomy, for the treatment of seizures, is highly successful but has a significant morbidity rate. The procedure is usually restricted to patients with an intractable seizure disorder and hemiparesis. Because of the inherent risk of surgery, patient selection is a critical issue. This report describes the evaluation of background activity and ictal patterns on surface and invasive EEG in 12 children who underwent both anatomical (7) and functional (5) hemispherectomy in order to determine the role of electroencephalography in the selection of patients for hemispherectomy, and to correlate EEG findings with underlying pathology and outcome. A favorable outcome was predicted by an interictal EEG with two or more of the following: suppression over the abnormal hemisphere, absence of contralateral slowing, absence of generalized discharges and absence of bilateral independent spiking; or by unilateral onset of ictal discharges on invasive intracerebral EEG recording. Outcome did not correlate with the underlying pathology. Hemispherectomy can be successful in patients with a variety of predominantly unilateral pathologic entities.

Brain↗
PubMed1995

Nitrous oxide depresses the H-reflex in children with cerebral palsy.

Hoffmann's reflex or H-reflex (HR) is an electrically elicited reflex that measures excitability of motoneurons and shares some physiologic properties with the deep tendon reflex. Children with tendon hyperreflexia due to cerebral palsy usually have higher amplitude HRs. Nitrous oxide (N2O) depresses the HR in patients with normal spinal reflexes, although the effect of N2O in conditions with hyperreflexia such as cerebral palsy is not known. We propose to determine the effect of N2O on the amplitude of the HR under general anesthesia in children with hyperreflexia due to cerebral palsy. We studied eight children undergoing selective dorsal rhizotomy (SDR) for the relief of spasticity. The maximum amplitudes of the HR (HRmax) and direct motor response (MRmax) were routinely evoked under the following anesthetic conditions: 1) sufentanil and 66% N2O/33% oxygen; and 2) sufentanil and 100% oxygen. The HRmax amplitude was significantly lower when N2O was part of the inspired gas mixture. The differences between the no N2O and the 66% N2O groups were significant. The MRmax did not change significantly. Abnormal spinal reflexes seen in spastic diplegia can be abolished by inhaled N2O. This finding also suggests that N2O-induced depression of spinal reflexes should be a consideration during physiologic monitoring of the spinal cord under general anesthesia.

Cerebral Palsy↗
PubMed1995

Use of subdural grids and strip electrodes to identify a seizure focus in children.

For patients with intractable seizures, the best surgical outcome is achieved following precise localization of the seizure focus. Scalp EEG monitoring may be insufficient and chronic subdural invasive EEG monitoring has therefore been advocated. At Children's Hospital in Boston, 31 children had chronic subdural monitoring from January 1990 through June 1994. The average age at implantation was 11 years. Most patients (22) had placement of grid electrodes combined with strip electrodes to map temporal and/or frontal regions bilaterally. Twenty of the patients eventually had a resective procedure based on the findings. During monitoring, cortical stimulations were performed to localize speech and somatosensory areas. There was only one complication, a subdural hematoma in a patient who had had previous surgery. Chronic subdural EEG monitoring is helpful in precisely localizing seizure foci in pediatric patients; it also allows motor and speech mapping and appears to be a safe modality in children.

Adolescent↗
PubMed1995

Corpus callosotomy in children.

All of the reports of corpus callosotomy have been limited by their necessarily retrospective nature, lack of control groups, and failure to quantify seizure frequency and duration before and after the surgery. In addition, interpretation of results has been confusing by inconsistent selection criteria of patients, varying surgical procedures employed, and short duration of follow-up. Nevertheless, this procedure remains a last hope for many children with severe intractable epilepsy and unquestionably assists in the management of many such children. There is a need to evaluate this surgical procedure fully to optimize its utilization further.

Adolescent↗
PubMed1995

The future of pediatric epilepsy surgery. Signposts and science.

Many of the advances in pediatric epilepsy surgery should reflect scientific, technical, and conceptual issues identical to those seen with adult epilepsy surgery. However, there are certainly some unique issues involving the developing brain, and these aspects require significant input from the discipline of developmental neurobiology and the study of cortical plasticity. These developmental disciplines may prove as critical as more traditional areas of electrophysiology thought to be key to the advancement of epilepsy surgery. Pediatric epilepsy surgery may turn out to be the major beneficiary of the basic scientific advancements in these burgeoning fields.

Adolescent↗
PubMed1994

H reflex studies in cerebral palsy patients undergoing partial dorsal rhizotomy.

H reflex studies were performed in ten spastic children with cerebral palsy who underwent partial dorsal rhizotomy (PDR). Under anesthesia prior to PDR, H reflex amplitude evoked by percutaneous peripheral nerve stimulation gradually declined in all patients and became unobtainable in five. Motor responses could still be evoked by apparent dorsal root stimulation in these five, but since it was shown that they were M responses and not reflexes, PDR was performed randomly. In the other five patients, in whom H reflexes were still evokable, dorsal root stimulation evoked motor responses which were true reflex responses, and PDR was performed "selectively." Compared to preoperative values, postoperative Hmax/Mmax ratios declined, but no more so in selective than in random PDR. We conclude that current intraoperative methods for selection of "abnormal" dorsal rootlets for section may be invalid and may have no bearing on successful outcome, since spasticity improves even with random PDR.

Analysis of Variance↗
PubMed1994

Technetium-99m HmPAO brain SPECT and outcome of hemispherectomy for intractable seizures.

With recent descriptions of the modified hemispherectomies and hemicorticectomy, there has been renewed interest in hemispherectomy for treatment of intractable seizures with hemiparesis. Because long-term outcome remains uncertain, patient selection remains difficult. 99mTc-HmPAO brain SPECT has been a helpful adjunct in the evaluation of epilepsy surgery candidates. We report SPECT scan findings in 7 patients who underwent hemispherectomy and compare these results with scalp EEG findings. Six patients had unilateral SPECT findings and all had a favorable outcome, regardless of surface EEG findings.

Adolescent↗
PubMed1994

[Target for anti-ulcer agents--pH, H. pylori or NO?].

Although until recently the reduction of gastric acid secretion was the primary aim in the treatment of peptic ulcer disease, it is now recognised that the presence of Helicobacter pylori and not only acid is required to produce duodenal ulcer. Accordingly, the part played by gastric acid has been relegated to the contributor to the effects of H pylori infection. Recent research into the pathogenesis and treatment of peptic ulcer disease suggests the locus of receptors for acid stimulants, such as acetylcholine, histamine and gastrin, to be the immune cell in the lamina propria of gastric mucosa, and not the parietal cell. Thus the effects of acid stimulants, as well as those of mediators of other gastro-intestinal functions, such as oesophageal and gastroduodenal bicarbonate secretion, may be directly transmitted to the effector cells via macrophages and plasma cells. Nitric oxide (NO) may be the agent mediating the interaction between immune and epithelial cells. If these findings are validated and confirmed in man, they may pave the way for new approaches to the treatment of acid-related disorders, resulting in therapeutic strategies that do not necessitate the eradication of H pylori.

Anti-Ulcer Agents↗
PubMed1993

Thallium-201 versus technetium-99m-MIBI SPECT in evaluation of childhood brain tumors: a within-subject comparison.

We previously found that 201TI SPECT is a highly specific agent for detection of metabolic activity of childhood brain tumors. To compare the relative diagnostic accuracy of 201TI and a technetium-based tumor-avid agent, we have obtained SPECT in 19 children using 201TI (37-111 MBq) followed immediately by 99mTc-methoxyisobutylisonitrile (MIBI) (370-740 MBq) intravenously. Moderate to intense focal uptake of both tracers characterized true positive cases (n = 6). Lesion boundaries were better defined by MIBI. Uptake of MIBI by choroid plexus occurred despite pretreatment with potassium perchlorate (6 mg/kg) and complicated interpretation of deep/paraventricular lesions. Preliminary assessment indicated sensitivity approximately 67% (TI and MIBI); specificity approximately 91% (TI); approximately 100% (MIBI). Two tumors (medulloblastoma, dysgerminoma) were TI/MIBI nonavid. Semi-quantitative assessment of tracer uptake was made using a ratio of radioactivity in tumor-containing areas compared to uninvolved brain. Ratio values were (mean +/- s.d.) 7.88 +/- 7.70 (TI) and 27.1 +/- 36.41 (MIBI). The spectrum of tumor avidity is similar for TI and MIBI. Clearer identification of boundaries by MIBI may be an advantage in applications, e.g., radiotherapy port planning.

Brain Neoplasms↗
PubMed1993

Chiari malformations, syringomyelia, and intramedullary spinal cord tumors.

Optimal management of congenital and acquired spinal cord lesions, such as Chiari malformations, syringomyelia, and intramedullary spinal cord tumors, depends on an understanding of the pathogenesis and natural history of these lesions. Magnetic resonance imaging and detailed physiologic investigations are shedding new light on these difficult-to-diagnose entities, and new surgical techniques are aiding in their management.

Arnold-Chiari Malformation↗
PubMed1992

[Chronic inflammatory bowel disease--current status].

Chronic inflammatory bowel disease (IBD) encompasses the disease entities, ulcerative colitis (UC) and Crohn's disease (CD). An aetiologic agent has not yet been defined and the diagnosis is based, therefore, on the sum of clinical, paraclinical, radiologic, endoscopic and histopathologic features. In recent years pathogenetic studies have focused on immune mechanisms, transmissible infectious agents, the potential role of the normal intestinal flora, dietary factors, enzymatic alterations and genetic features, in addition to vascular, neuromotor, allergic and psychologic factors. The prevalence of IBD is increased in first-degree relatives of patients and there is a high rate of disease concordance among monozygotic twins. Thus abnormal genes may encode for one or several immunoregulatory factors, while bacterial wall products seem to activate colonic inflammatory cells in a non-specific way, leading to increased production of cytokines, complement-derived peptides, eicosanoids, platelet activating factor, biogenic amines, kinins, chemotactic oligopeptides, and neuropeptides. The named soluble inflammatory mediators, in addition to free oxygen radicals, are considered responsible for the secondary amplification of the inflammatory process. The corner stones in medical therapy of IBD are still corticosteroids and sulphasalazine (SAZ). The new oral salicylates, which are analogues of SAZ or "slow release" preparations of 5-aminosalicylic acid (mesalazine), have provided a therapeutic progress, because they are tolerated better than SAZ. Immunosuppressive agents, such as azathioprine and 6-mercaptopurine, reduce the requirement for corticosteroids and are effective in refractory CD, but the effect is delayed up to several months. The therapeutic action of cyclosporine A is not sustained, but often associated with side effects. Metronidazole has a beneficial effect on perineal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Colitis, Ulcerative↗
PubMed1992

[Chronic inflammatory bowel disease].

Chronic inflammatory bowel disease (IBD) encompasses the disease entities, ulcerative colitis (UC) and Crohn's disease (CD). An aetiologic agent has not yet been defined and the diagnosis is based, therefore, on the sum of clinical, paraclinical, radiologic, endoscopic and histopathologic features. In recent years pathogenetic studies have focused on immune mechanisms, transmissible infectious agents, the potential role of the normal intestinal flora, dietary factors, enzymatic alterations and genetic features, in addition to vascular, neuromotor, allergic and psychologic factors. The corner stones in medical therapy of IBD are still corticosteroids and sulphasalazine (SAZ). The new oral salicylates, which are analogues of SAZ or "slow release" preparations of 5-aminosalicylic acid (mesalazine), have provided a therapeutic progress, because they are tolerated better than SAZ. Immunosuppressive agents, such as azathioprine and 6-mercaptopurine, reduce the requirement for corticosteroids and are effective in refractory CD, but the effect is delayed up to several months. The therapeutic action of cyclosporine A is not sustained, but often associated with side effects. Metronidazole has a beneficial effect on perineal disease. The efficacy of antimycobacterial drugs, sodium-cromoglycate, lidocaine, clonidine and sucralfate has been reported only in optimistic case stories and small open trials. A diet, rich in omega-3-fatty acids, modifies leukotriene (LT) production, but its clinical efficacy is insufficient. The first anti-leukotriene-drug, zileuton, has recently been evaluated and a significant, although insufficient, clinical response was obtained by a 70 per cent inhibition of rectal LTB4 synthesis. Dietary therapy may be useful as an adjunct to treatment of local complications in CD.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗
PubMed1989

[Prostaglandins and the resistance of the gastroduodenal mucosa].

The mechanisms responsible for maintaining the integrity of the gastroduodenal mucosa have been explored intensively in recent years. Prostaglandins seem to play a central role in mucosal defence. Important mechanisms by which prostaglandins may produce cytoprotection include regulation of the thickness and the composition of the mucus layer at the epithelial surface; modulation of active bicarbonate secretion by the surface epithelial cells; hydrophobicity of the surface epithelium; rapid cell proliferation and differentiation after mucosal damage; maintenance of interstitial bicarbonate; and the integrity of the microcirculation--in addition to synthesis of mucosal sulphhydryl groups. A defect mucosal defence is considered the most important pathogenetic factor in the majority of patients with peptic ulcer disease, but it is still unclear whether this is due to a deficiency in endogenous prostaglandins. Important risk factors for developing peptic ulcer disease, such as nonsteroidal antiinflammatory drugs and smoking, depress the formation of endogenous prostaglandins. The question of whether the use of direct cytoprotection may be relevant in ulcer therapy has yet not been solved and the rationale for substitution with prostaglandin analogues is to date empirical.

Animals↗
PubMed1989

[Prostaglandin analogues in the treatment of peptic ulcer disease].

The cytoprotective properties of native prostaglandins have been exploited for ulcer therapy through the development of analogous molecules, which are characterized by longer duration of action, more potent acid inhibitory effect and higher pharmacologic specificity. The therapeutic efficacy of prostaglandin analogues has been evaluated in a variety of controlled clinical trials, which are summarized briefly. The experience with arbaprostil, enprostil, misoprostol, rioprostil and trimoprostil shows that their effect on ulcer healing is superior to that of a placebo in acid inhibitory doses, which are also cytoprotective. Nevertheless, prostaglandin analogues are inferior to H2-receptor antagonists as regards their effects on ulcer healing, pain relief, and relapse prevention and less effective than expected from their acid inhibitory action. Placebo controlled trials of arbaprostil in acute upper gastrointestinal haemorrhage have failed to demonstrate any reduction in numbers of patients whose bleeding stopped, numbers with rebleeding or transfusion requirement. Diarrhoea occurs in 4%-34% of all patients and prostaglandin analogues are contraindicated in pregnant women. Although these drugs will probably not be marketed in Denmark for ulcer therapy, they may prove useful as replacement therapy in patients requiring nonsteroidal antiinflammatory drugs.

Humans↗