The role of transsphenoidal microsurgery in the management of sellar and parasellar meningioma

We report on eight meningiomas that have been operated on via the transsphenoidal route since May 1988. Six patients harbored cavernous sinus meningiomas with intrasellar extension. The intrasellar tumor extension and the parasellar tumor portion medial to the carotid artery were removed. Decompression of the pituitary gland with normalization of prolactin levels was achieved in all patients. It is a well-tolerated approach to confirm the diagnosis and still allows the option of major transcranial surgery in the event of tumor progression. Additionally, we report complete tumor removal in two rare cases with intrasellar and suprasellar merely subdiaphragmatic meningiomas.

Surgical management of acromegaly

Surgery is generally the primary therapy of choice in acromegaly, and the predominantly used transsphenoidal approach has proved to be efficient and safe. Surgical results are dependent on preoperative tumor size and extension and preoperative growth hormone levels. Invasion appears to be the most important factor in predicting surgical outcome. Growth hormone levels can be normalized in 71% of all cases and in more than 80% of microadenomas. Persistent growth hormone excess may require reoperation, radiotherapy, or medical treatment. With close interdisciplinary cooperation of neurosurgeons, endocrinologists, and radiotherapists, nearly all acromegalic patients can be successfully treated today.

Transsphenoidal microsurgery for craniopharyngioma

We report on our series of 32 craniopharyngiomas operated on by the transsphenoidal route since 1983. In 15 of 19 patients (79%) with primary transsphenoidal surgery and in 8 of 13 patients (62%) with a transsphenoidal approach following previous surgical procedures, the craniopharyngioma was totally removed. Primary transsphenoidal surgery is a safe and successful procedure for intrasellar and suprasellar infradiaphragmatic craniopharyngiomas. In secondary surgery and in the presence of tumor calcifications the indication for this approach must be considered more carefully. Postoperative posterior pituitary deficiency is a frequent occurrence. Anterior pituitary function usually remains unchanged after surgery except for normalization of hyperprolactinemia.

Interleukin-1 beta modulates the acute release of growth hormone-releasing hormone and somatostatin from rat hypothalamus in vitro, whereas tumor necrosis factor and interleukin-6 have no effect

There is clear evidence for communication between the immune and neuroendocrine systems. However, the effect of cytokines as major immune mediators on the hypothalamic growth peptides, GHRH and somatostatin (SRIH), is not well established. To investigate a possible hypothalamic action of the cytokines interleukin-1 beta (IL-1), interleukin-6, and tumor necrosis factor-alpha, on the release of GHRH and SRIH, we used a previously validated acute rat hypothalamic explant system. IL-1 caused a pronounced dose-dependent stimulation of SRIH in the dose-range 1-100 U/ml (P less than 0.01). GHRH showed a slight, but significant, increase in response to IL-1 tested in the dose-range 10-100 U/ml. Similar studies with mediobasal hypothalamic (GHRH and SRIH) or median eminence (SRIH) fragments produced no change in either GHRH or SRIH release. The effects of IL-1 were antagonized by the cyclo-oxygenase inhibitor, indomethacin (10 micrograms/ml). Stimulation of GHRH and SRIH could not be blocked by the CRH-antagonist alpha-helical CRH (9-41) at 10(-6) M. Interleukin-6, in the dose range 10-100 U/ml, and tumor necrosis factor-alpha, in the dose range 10-10,000 U/ml, had no effect on the acute hypothalamic release of either GHRH or SRIH. It is concluded that IL-1 stimulates the acute hypothalamic release of GHRH and SRIH, and that this effect is mediated by cyclo-oxygenase products. The marked IL-1 stimulation of hypothalamic SRIH release may override the minor increase of GHRH increase, and may thus contribute to disturbances in growth seen in the presence of chronic inflammation.

Calcium and calmodulin mediation of growth hormone-releasing hormone release from the rat hypothalamus in vitro

A major role for Ca2+ and calmodulin in stimulus-secretion coupling has been suggested for several neuropeptides; however, the cellular mechanisms of GH-releasing hormone (GHRH) release have been little investigated so far. We have used a previously validated acute rat hypothalamic explant system in order to elucidate whether Ca2+ acts as a second messenger in the regulation of GHRH release, and whether calmodulin-dependent pathways are involved. Calcium dependence of somatostatin (SRIH) release was assessed in the same experiments. Calmodulin dependence of SRIH was not investigated in detail, as it has been established previously. The calcium-entry antagonist, verapamil, antagonized K(+)-stimulated GHRH and SRIH release in a dose-dependent manner, with maximal inhibition shown at 10(-4) M. The calmodulin antagonist W7 also blocked K(+)-evoked GHRH release in a dose-dependent manner, with significant inhibition in the dose range 5 X 10(-5) M to 2 X 10(-4) M; similarly, a more specific calmodulin inhibitor, the W7 derivative 5-iodo-C8 (W8), reversed K(+)-stimulated GHRH release, showing slightly higher potency than W7. W7 also reversed GHRH release in response to the calcium-ionophore A23187, although verapamil had no effect on A23187-evoked GHRH or SRIH release. Thapsigargin, which increases the efflux of Ca2+ from calciosomes, did not affect either GHRH or SRIH release at 10(-5) M or 10(-4) M. The basal release of GHRH was clearly suppressed by W7 and W8 (10(-4) M), whereas verapamil had no effect. We conclude that calcium influx is crucial for depolarization-induced GHRH and SRIH release. Calcium entrance in response to A23187 appears to be independent of verapamil-sensitive calcium channels. The lack of effect of thapsigargin suggests that increased intracellular Ca2+ from intracellular stores is not equivalent to an increase in Ca2+ influx. Both basal and depolarization-induced release of GHRH in this system are calmodulin dependent.

Long-term follow-up results in hormonally active pituitary adenomas after primary successful transsphenoidal surgery

The long-term results of transsphenoidal surgery for hormonally active pituitary adenomas were assessed in 3 follow-up studies. Eight out of 50 patients with microprolactinomas developed a persisting postoperative re-increase of prolactin levels during an average follow-up period of 4.1 years. None of the 43 acromegalic patients who had achieved a suppression of growth hormone to below 2 ng/ml during an oral glucose load shortly after surgery relapsed. However, when the remission criterion was only based on basal growth hormone below 5 ng/ml 4 out of 61 patients showed a re-increase of growth hormone levels to persistently elevated values during an average follow-up period of 6.1 years. 14 out of 66 patients followed-up for an average of 8.2 years after successful primary microadenomectomy for Cushing's disease developed recurrent hypercortisolism as documented by an abnormal suppression of cortisol after oral low dose dexamethasone.

Recurrence following transsphenoidal surgery for acromegaly

The long-term results of transsphenoidal adenomectomy and the incidence of possible recurrences were studied in 61 patients who had normal basal serum growth hormone (GH) levels 1 week after surgery. The patients were followed up for an average of 6.0 years (range: 1.5-14.0 years) by repeated measurements of GH, oral glucose tolerance testing (OGTT) and at the last follow-up visit also by assaying somatomedin C levels. In 4 of the patients, the basal GH levels had increased to values above 5 ng/ml. In 43 patients, a normal suppression of GH during an oral glucose load was observed shortly after surgery. In only 2 of these cases did a transiently inadequate suppression develop during the follow-up period, although clinical acromegaly did not recur and the somatomedin C levels remained normal. It is concluded that recurrence of active acromegaly is unlikely to occur in patients who achieve a normal glucose-induced suppression of GH levels shortly after adenomectomy. As such, an OGTT provides better prognostic information than basal human GH level measurements and may give a clearer and earlier indication of surgical success.

The coexistence of pituitary adenomas and meningiomas: three case reports and a review of the literature

A coexistence of pituitary adenomas and meningiomas is very rare. We have reported on three of our own cases and reviewed the 17 cases reported in the literature. One has to differenciate between the coexistence of a pituitary adenoma and a meningioma without previous irradiation, and the occurrence of a meningioma following the irradiation of a pituitary adenoma. In the cases without irradiation, the adenoma and the meningioma are diagnosed simultaneously. On the other hand meningiomas arising after irradiation of a pituitary tumour are usually diagnosed only after a long latent period. The coexistence of pituitary tumours and meningiomas resulting from hormone dependent growth as well as the induction of growth of meningiomas by irradiation are discussed.

Malate dehydrogenases. The lack of evidence for dissociation of the dimeric enzyme in kinetic analyses

The kinetic parameters of beef heart cytoplasmic and pig heart mitochondrial malate dehydrogenases have been examined over a wide range of enzyme concentration. No significant changes are observed in these properties. In conjunction with active enzyme sedimentation and sedimentation equilibrium experiments, it is concluded that there is no evidence for dissociation of the dimeric enzyme at any enyzme level in the kinetic analyses. Thus, if dissociation occurs, it must be too slow to be of significance in determining the kinetic properties of the enzyme. It is shown that unless a subunit and its dimeric form have identical kinetic and substrate binding characteristics, the kinetic parameters should change as a function of enzyme concentration.