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Biomedical subjects

E Meijer

Publications and source records attributed to E Meijer.

At least 37 records · Page 2Linked to original sources
PubMed1996

Suboccipital surgery for acoustic neuroma.

A retrospective study was performed on 106 consecutive patients with an acoustic neuroma who underwent suboccipital surgery for the first time between 1980 and 1992. Complete follow-up data were available for all the patients, including regular imaging up to 1 January 1994. Incomplete removal of the tumours was chosen in preference to radical surgery in a large proportion of the patients, to avoid the risk of post-operative morbidity. The recurrence rate in this series was 20%. Comparison of the results of suboccipital surgery to those obtained using other surgical approaches, while taking the tumour size into consideration, showed that better results can be obtained after total removal of the tumour without any additional risk to post-operative facial nerve function. The long-term results of subtotal removal using the suboccipital approach were disappointing. It is therefore necessary to review the indications for non-radical surgery in patients with an acoustic neuroma.

Audiometry, Pure-Tone↗
PubMed1995

Acoustic neuroma: correlation among tumor size, symptoms, and patient age.

Due to improved diagnostic techniques, acoustic neuromas more frequently are detected at an early stage. Subsequent treatment depends on such factors as expected tumor growth rate, tumor size, and patient age. The natural history of acoustic neuromas is still uncertain: This study was performed to examine possible correlations among tumor size, patient age, signs and symptoms, and duration of symptoms. The study included 164 patients with an acoustic neuroma who were treated at University Hospital Nijmegen, The Netherlands, over a period of 13 years. Comparisons were made between the findings of this study and the reports in the literature. No support was found for any of the correlations mentioned in other studies, and no relationships could be demonstrated between the parameters evaluated in this study. The authors therefore recommend that treatment policies be based only on well-established correlations.

Adolescent↗
PubMed1994

Hypoglycaemia unawareness.

Hypoglycaemia is a severe complication of insulin-dependent diabetes mellitus, especially when it is not preceded by warning signs. A patient unaware of a low blood glucose concentration may not take any remedial action, becomes severely hypoglycaemic and may lapse into a potentially fatal coma. Hypoglycaemic unawareness is associated particularly with good glycaemic control. Hypoglycaemia unawareness was first related to diabetic autonomic neuropathy. Subsequently it emerged that well controlled diabetic patients suffered from hypoglycaemia unawareness more often than poorly controlled patients. Next to autonomic neuropathy and good glycaemic control, the transfer of more slowly resorbed beef and porcine insulin to more rapidly resorbed human insulin has been incriminated as causing an increased incidence of hypoglycaemia unawareness. Reviewing the scientific literature concerning the connection between hypoglycaemia unawareness and the use of human insulin, there is no rationale for supporting the hypothesis that human insulin leads to hypoglycaemia unawareness any longer. While the pathophysiology of hypoglycemia unawareness remains unclear in patients with insulin-dependent diabetes mellitus of long duration, it may well be related to impaired adrenaline secretion. The cause of this impaired adrenaline secretion during hypoglycaemia is unknown and it does not seem to be a result of diabetic autonomic neuropathy.

Blood Glucose↗
PubMed1992

Suramin: rapid loading and weekly maintenance regimens for cancer patients.

PURPOSE: Suramin is an anticancer agent with a narrow therapeutic window and a terminal half-life of 45 to 55 days. These characteristics make it necessary to control accurately the serum concentrations of the drug. Therefore, the aim of the present study was to develop a rapid loading regimen, followed by weekly administration of suramin to maintain serum concentrations of between 150 and 300 micrograms/mL for 8 weeks. PATIENTS AND METHODS: Eligible patients were treated with five different loading regimens. Initially, weekly maintenance doses were estimated manually by the treating physician. Subsequently, computer-assisted dosing that used Bayesian pharmacokinetic modeling was used. RESULTS: Thirty-eight courses of suramin that were administered to 35 patients were studied. The optimal loading regimen consisted of a continuous infusion of 600 mg/m2 during a 24-hour period, which resulted in a mean serum concentration of 319 micrograms/mL. Potentially toxic concentrations that were observed with shorter infusions were avoided. Maintenance treatment, which used the weekly administration of suramin during a 6-hour period, seemed to be able to maintain mean suramin serum trough concentrations of 150 micrograms/mL, while preventing mean peak concentrations of more than 300 micrograms/mL. The use of Bayesian pharmacokinetics was superior to manual estimation in tailoring the optimal dose to the therapeutic window. CONCLUSIONS: Continuous infusion is the optimal way of delivering suramin during the loading phase. To maintain trough levels and peak levels within a narrower therapeutic window, suramin will have to be administered more frequently than once a week. Bayesian modeling based on individual serum levels and population pharmacokinetics allows accurate dosing to maintain suramin levels within the therapeutic window.

Adult↗
PubMed1991

[Postoperative irradiation in grade III and IV astrocytoma].

The aim of this paper is to contribute to the discussion on the value of postoperative radiotherapy in patients with astrocytoma grade III-IV. One hundred and fifteen of the 243 patients with histologically proven astrocytoma grade III-IV received postoperative radiotherapy at the St. Radboud University Hospital Nijmegen. According to the protocol all patients with a fairly good performance status were irradiated. The extent of surgery consisted of biopsy alone in 11%, subtotal tumour resection in 85% and macroscopically complete tumour removal in 4%. All patients received a whole brain irradiation of 40 Gy with a boost of 10-15 Gy in the tumour. Patients with grade III who underwent surgical resection had a median survival of 2.1 months, those with grade IV 2.7 months. Patients who underwent surgical resection and radiotherapy had a median survival of 12 months (grade III) and 8.6 months (grade IV). The extent of surgery and grade of malignancy were the only prognostic factors. Because of the selection of patients this study produces no additional arguments in favour of postoperative radiotherapy. However, we continue our treatment strategy to irradiate patients with grade III-IV tumours because the median survival obtained with this strategy is high in comparison with data from literature.

Adolescent↗
PubMed1991

Results of follow-up after removal of non-functioning pituitary adenomas by transcranial surgery.

The records of 53 patients who had undergone transcranial surgery for a non-functioning pituitary adenoma were reviewed. The most common symptom in these patients was visual loss (51 patients). Headache was the presenting symptom in 25 and hypopituitarism in 18. After surgery 17 of the patients were symptom free, 26 were improved, while seven remained unchanged. Three patients died. Other complications occurred in 12 patients but without serious long-term morbidity. Radiation therapy was given to patients in whom subtotal resection of tumour was achieved. None of these patients had tumour recurrence in a mean follow-up period of 76 months, while of the patients in whom tumour extirpation seemed to be complete, 36% had tumour recurrence.

Adenoma↗
PubMed1990

Astrocytoma in childhood: survival and performance.

Seventy-nine children (35 female, 44 male) with proven or presumed astrocytoma were treated from 1967 to 1987. The tumors were supratentorial located in 24 children, cerebellar in 21 children, and pontine in 34 children. If possible, a radical tumor resection (4%), a subtotal tumor resection (51%), or a biopsy (8%) was performed. The predominant pathological Kernohan grading for the supratentorial, cerebellar, and pontine located tumors were grades II, II, and IV respectively. Histology was unknown in 15 out of 34 pontine tumors and in 1 out of 24 supratentorial tumors. Low-graded tumors (46%) were irradiated with a local field (1.8/45-50 Gy) and children with high-graded tumors (34%) received a total brain irradiation (1.8/40 Gy) followed by a boost irradiation (10 Gy) in 5 or 6 fractions. Overall 1-, 5-, and 10-year survivals of children with supratentorial, cerebellar, and pontine located tumors were 96%-91%-46%, 95%-95%-95%, and 35%-20%-20% respectively. For all tumor locations, 77% of deaths occurred within 2 years of treatment. The performance status of both children with supratentorial and cerebellar astrocytoma showed an increase during the first year of treatment and then stabilized on a rather high level (mean performance after 5 years of 60% and 70% respectively). Children with pontine tumors showed a steep decrease in performance status during the first year of treatment and then stabilized on a low level (mean performance after 5 years of 15%). In our study, children with supratentorial astrocytoma showed improvement in both survival and performance status after irradiation following surgical removal of the tumor.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1989

Predictive factors for initial cure and relapse rate after pituitary surgery for Cushing's disease.

Twenty-seven patients with Cushing's disease underwent transsphenoidal pituitary surgery. After the operation 16 patients were cured, and 11 remained hypercortisolemic. In the cured patients a significantly lower incidence of paradoxical responsiveness to TRH or to LRH was found preoperatively (1 of 16) than in the failures (6 of 11; P less than 0.02, by Fisher's chi 2 test). Furthermore, responsiveness of cortisol to CRH administration was significantly lower in the failures [maximum, 0.30 +/- 0.10 mumol/L (10.8 +/- 3.6 micrograms/dL) vs. 0.50 +/- 0.07 mumol/L (18.1 +/- 2.5 micrograms/dL) in the cured patients; P less than 0.05]. There were no differences in basal plasma cortisol levels, ACTH levels, or suppressibility by dexamethasone between the 2 groups. In the 16 patients who were cured initially, 4 patients relapsed after a mean period of 4 yr. These 4 patients had significantly higher basal cortisol levels postoperatively than those who remained in remission [0.14 +/- 0.03 mumol/L (5.1 +/- 0.8 micrograms/dL) vs. 0.04 +/- 0.01 mumol/L (1.4 +/- 0.3 micrograms/dL); P less than 0.01]. Cortisol responses to CRH after the operation positively correlated with the basal cortisol levels at that time (P less than 0.05, by Spearman's rank correlation test; r = 0.64), thus, the relapsing patients had higher cortisol responses to CRH than patients who stayed in remission [maximum response, 0.31 +/- 0.07 (11.2 +/- 2.5 micrograms/dL) vs. 0.12 +/- 0.03 mumol/L (4.3 +/- 1.1 microgram/dL), respectively; P less than 0.05]. We conclude that 1) patients responding paradoxically to TRH and/or LRH have a lower chance of being cured after pituitary surgery; and 2) patients with higher cortisol levels (greater than 0.10 mumol/L; 3.6 micrograms/dL) after being cured initially have a higher chance of recurrence of their disease.

Adenoma↗
PubMed1988

Which factors predict the results of pituitary surgery in acromegaly?

Thirty-one patients with acromegaly who underwent pituitary surgery were investigated for possible predictive factors of the surgical outcome. The patients were divided into two groups: those whose GH levels normalized (less than 5 micrograms/l) after operation, group A (N = 18), and those whose GH levels remained elevated, group B (N = 13). There were no differences in age, sex distribution and sellar volume between both groups. There was a tendency to a higher incidence of supra-sellar extension of the pituitary tumor in group B (P less than 0.10). The basal GH levels in group A (38 +/- 5 micrograms/l) before operation were significantly lower than in group B (100 +/- 22 micrograms/l, P less than 0.002). Somatomedin C levels after the operation were significantly lower in group A than in group B (P less than 0.05) and were more often in the normal range (P less than 0.05). No differences were found in the occurrence of paradoxical GH responses to TRH and/or to GnRH between the groups and neither were there any differences in GH responses to GHRH and to bromocriptine between the groups. The sensitivity to SRIH tended to be higher in group A. After operation, the paradoxical GH response to TRH disappeared in 7 out of 10 patients and to GnRH in 2 out of 5 patients of group A, whereas in group B this anomaly persisted in all 9 after TRH and all 3 patients after GnRH. Hypopituitarism developed in only 5 out of the 31 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1987

Coexistence of hypothalamic and pituitary failure after successful pituitary surgery in Cushing's disease?

The type of secondary adrenal failure, which occurs after successful pituitary surgery in Cushing's disease was studied using CRH administration. Eight patients with Cushing's disease were studied in the immediate postoperative period (9-18 days) of successful pituitary surgery. The results in these patients were compared with those in 13 healthy subjects, 7 patients with secondary adrenal failure of the pituitary type and 9 patients with secondary adrenal failure of the hypothalamic type. In all postoperative patients with Cushing's disease, except one, clear ACTH and cortisol responses occurred after CRH, demonstrating hypothalamic adrenal failure in these patients. This demonstration of hypothalamic adrenal failure after neurosurgery strongly argues against a pivotal role for endogenous CRH in the pathogenesis of Cushing's disease in these patients. The mean ACTH response to CRH in the postoperative patients with Cushing's disease was significantly lower than that in patients with adrenal failure of the hypothalamic type. This suggests the presence of pituitary failure in the postadenomectomy patients. In conclusion, this study provides arguments that the secondary adrenal failure after adenomectomy in Cushing's disease is caused by both hypothalamic and pituitary failure.

Adrenal Insufficiency↗
PubMed1979

Morphology of the cervical spinal cord on computed myelography.

To ensure adequate use of the technique of computed myelography (CM) it is necessary to have an exact picture of the morphology of the normal spinal cord as demonstrated by this technique. This has been obtained by studying the morphology and measuring the frontal and sagittal diameter of the cervical cord in 20 patients. The normal values are presented. The changes of this morphology in one patient with a tumour, one patient with atrophy of the spinal cord and in some patients with congenital malformations are also reported.

Adult↗