Surgical removal of growth hormone-secreting pituitary adenomas with intensive microsurgical pseudocapsule resection results in complete remission of acromegaly

Endoscopic endonasal surgery for non-invasive pituitary neuroendocrinology tumors with incomplete pseudocapsule

Background

Pituitary neuroendocrinology tumors (PitNETs) with pseudocapsule can be effectively removed by the pseudocapsule-based extracapsular resection technique. In the areas without pseudocapsule, the tumor cells can spread into the adjacent tissues at the cellular level, which brings a great challenge to achieving total tumor resection.

Methods

Our surgical strategy for PitNETs with an incomplete pseudocapsule is to combine the pseudocapsule-based extracapsular resection technique with the intensive excision technique for the removal of the tumor. Specifically, the pseudocapsule-based extracapsular resection technique is applied in the areas with pseudocapsule, while in the areas without pseudocapsule, the intensive excision technique bounded by adjacent normal structures is adopted. Moreover, a pathological examination was performed to determine the situations of pseudocapsule and tumor cell remnant.

Results

All growth hormone-secreting PitNETs achieved biochemical remission after surgery. There was no deterioration of pituitary functions postoperatively, and the preoperative hypopituitarism had improved in all patients postoperatively. In total, two cases suffered a transient diabetes insipidus, and intraoperative cerebrospinal fluid leakage was observed in two cases but no postoperative cerebrospinal fluid leakage in all cases. There was no recurrence during the follow-up. The fragmental pseudocapsule and small tumor remnants were found in the majority of suspicious tissues by histological staining.

Conclusion

The effectiveness and safety of the surgical strategy were preliminarily explored for removing PitNETs without incomplete pseudocapsules. In overview, the pseudocapsule-based extracapsular resection technique is applied in areas with pseudocapsule, while the intensive excision bounded by adjacent normal structures is adopted in other areas.

Extra-Pseudocapsular Transsphenoidal Surgery for Microprolactinoma in Women

A recall for histological pseudocapsule (PS) and reappraisal of transsphenoidal surgery (TSS) as a viable alternative to dopamine agonists in the treatment algorithm of prolactinomas are getting vibrant. We hope to investigate the effectiveness and risks of extra-pseudocapsular transsphenoidal surgery (EPTSS) for young women with microprolactinoma, and to look into the factors that influenced remission and recurrence, and thus to figure out the possible indication shift for primary TSS. We proposed a new classification method of microprolactinoma based on the relationship between tumor and pituitary position, which can be divided into hypo-pituitary, para-pituitary and supra-pituitary groups. We retrospectively analyzed 133 patients of women (<50 yr) with microprolactinoma (≤10 mm) who underwent EPTSS in a tertiary center. PS were identified in 113 (84.96%) microadenomas intraoperatively. The long-term surgical cure rate was 88.2%, and the comprehensive remission rate was 95.8% in total. There was no severe or permanent complication, and the surgical morbidity rate was 4.5%. The recurrence rate with over 5 years of follow-up was 9.2%, and a lot lower for the tumors in the complete PS group (0) and hypo-pituitary group (2.1%). Use of the extra-pseudocapsule dissection in microprolactinoma resulted in a good chance of increasing the surgical remission without increasing the risk of CSF leakage or endocrine deficits. First-line EPTSS may offer a greater opportunity of long-term cure for young female patients with microprolactinoma of hypo-pituitary located and Knosp grade 0-II.

Development and Validation of a Prognostic Model for Post-Operative Recurrence of Pituitary Adenomas

Background

We aimed to assess clinical factors associated with tumor recurrence and build a nomogram based on identified risk factors to predict postoperative recurrence in patients with pituitary adenomas (PAs) who underwent gross-total resection (GTR).

Methods

A total of 829 patients with PAs who achieved GTR at Tongji Hospital between January 2013 and December 2018 were included in this retrospective study. The median follow-up time was 66.7 months (range: 15.6-106.3 months). Patients were randomly divided into training (n = 553) or validation (n = 276) cohorts. A range of clinical characteristics, radiological findings, and laboratory data were collected. Uni- and multivariate Cox regression analyses were applied to determine the potential risk factors for PA recurrence. A nomogram model was built from the identified factors to predict recurrence. Concordance index (C-index), calibration curve, and receiver operating characteristic (ROC) were used to determine the predictive accuracy of the nomogram. Decision curve analysis (DCA) was performed to evaluate the clinical efficacy of the nomogram.

Results

Pseudocapsule-based extracapsular resection (ER), cavernous sinus invasion (CSI), and tumor size were included in the nomogram. C-indices of the nomogram were 0.776 (95% confidence interval [CI]: 0.747-0.806) and 0.714 (95% CI: 0.681-0.747) for the training and validation cohorts, respectively. The area under the curve (AUC) of the nomogram was 0.770, 0.774, and 0.818 for 4-, 6-, 8-year progression-free survival (PFS) probabilities in the training cohort, respectively, and 0.739, 0.715 and 0.740 for 4-, 6-, 8-year PFS probabilities in the validation cohort, respectively. Calibration curves were well-fitted in both training and validation cohorts. DCA revealed that the nomogram model improved the prediction of PFS in both cohorts.

Conclusions

Pseudocapsule-based ER, CSI, and tumor size were identified as independent predictors of PA recurrence. In the present study, we developed a novel and valid nomogram with potential utility as a tool for predicting postoperative PA recurrence. The use of the nonogram model can facilitate the tailoring of counseling to meet the individual needs of patients.

Comparison of outcomes between intracapsular resection and pseudocapsule-based extracapsular resection for pituitary adenoma: a systematic review and meta-analysis

Background

Transsphenoidal surgery is the preferred first-line therapy for most pituitary adenoma(PA), and the conventional strategy of treatment is intracapsular resection(IR). The protocol of extracapsular resection(ER), which considers the pseudocapsule as the PA boundary for surgical removal, has also been introduced gradually. In this study, the clinical efficacies and complications were explored and compared between these two procedures.

Methods

A systematic literature review was performed in the PubMed, EMBASE, Web of Science and Cochrane databases. Articles comparing between IR and ER were included.

Results

There were 7 studies containing 1768 cases in accordance with the inclusion criteria. Although the meta-analysis showed no significant difference in complete resection, a sensitivity analysis revealed that ER was more conducive to total PA resection than IR. Moreover, we found a significant difference in favor of ER regarding biochemical remission. Furthermore, there was no significant difference in the incidence rate of certain complications, such as hormone deficiency, diabetes insipidus, intraoperative cerebrospinal fluid(CSF) and postoperative CSF leakage. However, a sensitivity analysis suggested that IR decreased the risk of intraoperative CSF leakage.

Conclusions

This meta-analysis unveiled that ER contributed to biochemical remission. To some extent, our results also showed that ER played a positive role in complete resection, but that IR reduced the incidence of intraoperative CSF leakage. However, the available evidence needs to be further authenticated using well-designed prospective, multicenter, randomized controlled clinical trials.

Metachronous Double Pituitary Adenoma with Altered Transcriptional Factor Profile: A Case Report and Literature Review

Double pituitary adenomas (DPAs), especially metachronous DPAs, are extremely rare and there has been no report about DPAs with altered transcriptional factors. We describe the case of a 25-year-old man who presented with acromegaly 7 years after surgery for a non-functioning pituitary adenoma (NFPA). Before the initial surgery, endocrine evaluation confirmed NFPA or silent somatotroph pituitary adenoma (SPA) because of normal serum levels of insulin-like growth factor-1 (IGF-1) and insufficient suppression of growth hormone (GH) levels in the oral glucose tolerance test (OGTT). Immunohistochemistry of resected tissue obtained from gross total resection (GTR) with transsphenoidal surgery (TSS) was negative for follicle-stimulating hormone, luteinizing hormone, GH, and Pit-1 but positive for GATA3, which confirmed the gonadotroph pituitary adenoma (GPA) diagnosis. Seven years later, follow-up brain MRI revealed a 13.3 × 5.6 × 4.7 mm tumor within the sellar turcica. The endocrine evaluation confirmed acromegaly because of high serum levels of IGF-1 and insufficient suppression of GH levels upon OGTT. GTR with TSS was again performed, and immunohistochemistry was negative for GATA3 but positive for GH and Pit-1. Surprisingly, he showed altered transcription factor expressions between initial and recurrent surgery. Based on the overall clinical course and hormonal secretion findings, we speculated metachronous development of a DPA, i.e., SPA followed by GPA, wherein a few remaining cells of the SPA might have regrown after the initial surgery. We conducted a literature review of cases that documented altered hormone secretion at recurrence and emphasized the necessity of identifying a small adenoma when there is a discrepancy between pathological findings and hormone secretion tests.

Pseudocapsule-Based Resection for Pituitary Adenomas via the Endoscopic Endonasal Approach

Introduction

The endoscopic endonasal approach (EEA) is a safe and effective treatment for pituitary adenomas (PAs). Since extracapsular resection (ER) of PAs improves tumor resection and endocrine remission rates, the interface between the pseudocapsule and gland draws increasing attention. However, it is difficult to precisely dissect the tumor along the exact boundary, and complete removal of the tumor increases the risks of normal tissue damage and cerebrospinal fluid (CSF) leakage. In this study, we investigated the extracapsular resection as well as the pseudocapsule histology to evaluate the effectiveness and safety of pseudocapsule-related surgical interventions.

Methods

From December 2017 to December 2019, 189 patients of PAs via EEA in our single center were analyzed retrospectively. The images, operative details, and clinical follow-up of patients were collected. Sixty-four patients underwent pseudocapsule-based ER, and 125 patients also underwent traditional intracapsular resection (IR) with or without intensive excision for FPAs. The clinical characteristics, tumor resection, endocrinological outcomes, and postoperative morbidities of the two groups were compared. Informed consent for publication of our article was obtained from each patient. Histological examination of pseudocapsule was performed using hematoxylin and eosin and reticulin staining.

Results

The gross total recession was 62 (96.9%) in the ER group and 107 (85.6%) cases in the IR group, whereas the endocrine remission rate was 29/31 (93.5%) and 40/53 (75.5%) cases, respectively. Anterior pituitary functions were not aggravated postoperatively in any patient, but transient diabetes insipidus (DI) occurred more in the IR group (64.0%) than in ER (48.4%). Pseudocapsule specimens were obtained in 93 patients, and clusters of small cell aggregation were detected in 11 pseudocapsule specimens (11.8%) whereas other patients showed no remarkable developed pseudocapsule. Intraoperative CSF leak occurred more in the ER group (28.1%) than in the IR group (13.6%), but no difference was seen between two groups postoperatively. No case of intracranial hematoma or pituitary crisis occurred in both groups. After a mean follow-up of 22.8 months, tumor recurrence was observed in 4 (2.1%) cases.

Conclusion

Pseudocapsule-based extracapsular resection of PAs via EEA is an effective and safe procedure to achieve complete resection with high and sustained endocrine remission and without deteriorating pituitary function.

Pseudocapsule and pseudocapsule-based extracapsular resection in pituitary neuroendocrine tumors

Since Costello et al. proposed the concept of pseudocapsule of pituitary neuroendocrine tumors (PitNETs) in 1936, many studies have been published on its occurrence, development process, histopathology, and morphology. Pseudocapsule has been proposed as the anatomical interface between PitNETs and normal pituitary gland, therefore the so-called pseudocapsule-based extracapsular resection (ER) technique was developed as an extracapsular surgery method for PitNETs,which differs from the conventional intracapsular resection (IR). In recent years, ER has also been widely used in patients of different tumor types, sizes, and age groups, because the pseudocapsule can be identified more clearly under the endoscopy. Endoscopic transsphenoidal resection for PitNETs has become the preferred surgical method. We reviewed relevant literatures in the past 10 years, showing that ER could achieve better rate of gross total resection (GTR) and biochemical remission, and reduce tumor recurrence than IR, without increasing postoperative complications. Therefore, the pseudocapsule and ER should be valued by neurosurgeons and actively promoted clinically.

Pseudocapsular resection in elderly patients with non-functioning pituitary adenoma

OBJECTIVE

The safety of transsphenoidal surgery (TSS) for pituitary adenoma in elderly populations is becoming a new topic in our aging society. However, previous studies did not focus on the surgical procedures in elderly patients. We attempted to clarify the safety of TSS and the influence of pseudocapsular resection in elderly patients with non-functioning pituitary adenoma (NFPA).

METHODS

A total of 284 patients undergoing initial TSS for NFPA were categorized into two groups as follows: 1) Elderly group (n = 69; age ≥ 70 years); and 2) Younger group (n = 215; age < 70 years). Furthermore, all patients were newly divided into the two following categories: 1) Resected group (n = 121, with total pseudocapsule resection); and 2) Non-Resected group (n = 163, without total pseudocapsule resection). The main outcome measure was the incidence of perioperative complications and the rate of severe growth hormone deficiency (sGHD) after TSS.

RESULTS

There were no significant differences in the rates of perioperative complication between the Elderly and Younger groups. Furthermore, pseudocapsular resection did not increase the surgical risks in either group. On the other hand, sGHD only showed a significant improvement in the Younger group. The only factor predicting the new development of sGHD following TSS was an older age, not pseudocapsule resection.

CONCLUSIONS

Aging does not increase the perioperative complications of TSS for NFPA; however, aging has a negative influence on the postoperative function of GH secretion. In contrast, pseudocapsular resection does not have any negative influence on the perioperative complications or postoperative function of GH secretion, even in elderly patients, based on the authors' experience and surgical technique.

Effectiveness of the intraoperative magnetic resonance imaging during endoscopic endonasal approach for acromegaly

PURPOSE

Acromegaly is an acquired disorder usually caused by growth hormone-secreting pituitary adenoma, resolution of which requires correction of the excess hormone production. Recently, intraoperative magnetic resonance imaging (iMRI) was reported to be useful during the endoscopic endonasal approach (EEA) for pituitary adenoma. The present study was performed to quantitatively assess the role of iMRI in improving surgical outcomes in EEA for acromegaly.

METHODS

Twenty surgeries for acromegaly in EEA performed at Shinshu University Hospital between April 2016 and March 2020 were reviewed retrospectively. The inclusion criteria were cases without severe cavernous sinus tumor invasion (Knosp grade 0 - 3) or history of prior pituitary surgery. Fifteen consecutive patients were enrolled in this study. Clinical characteristics and postoperative clinical outcomes were compared between patients with and without use of iMRI during EEA for acromegaly.

RESULTS

Conventional navigation-guided surgery was performed in nine patients, and six underwent iMRI-guided EEA for acromegaly. Gross total resection (GTR) was obtained in the six (100%) patients in the iMRI group, and in four (44.4%) patients in the conventional group without iMRI. Postoperative clinical outcomes, including hormonal remission rate and surgical complications, were comparable between the two groups.

CONCLUSION

Although iMRI significantly increased the GTR rate, we found no direct evidence of increased hormonal remission rate by use of iMRI. It is important to confirm complete tumor resection carefully with not only iMRI findings, but also with intraoperative high-definition endoscopic direct visualization to increase the hormonal remission rate of acromegaly.

Novel Bendable Ring Curette for Endoscopic Transsphenoidal Surgery for Pituitary Tumors

OBJECTIVE

In transsphenoidal resection of pituitary tumors, even dedicated instruments sometimes cannot readily reach the surgical fields and they interfere with the endoscope and other instruments, making instrumental manipulations difficult and often ineffective. To solve these problems, we invented a bendable ring curette to further improve maneuverability and accessibility.

METHODS

The newly developed ring curette has a tip (14-mm long) that can bend spanning a range of 90°. Two types of ring curette are constructed; an upward-bending type, and a downward-bending type. We used the ring curette in 222 endoscopic pituitary surgeries.

RESULTS

The ring curette was easily operated with one hand, simply by manipulating the slider located at the handle to bend or straighten the tip. The bendable ring curette permits adequate access to sites where regular dedicated instruments such as the fixed-angle ring curette could not reach easily. The ring curette facilitated tumor resection as long as tumors were not too hard. Furthermore, the curette could be used as a dissector because the long tip provides greater horizontal and vertical forces.

CONCLUSIONS

Our newly developed bendable ring curette improves maneuverability and accessibility and can be efficiently used as a dissector in the far lateral and frontal sites, compared with the conventional fixed instrument.

Development and clinical validation of a grading system for pituitary adenoma consistency

OBJECTIVE

Pituitary adenoma (PA) consistency, or texture, is an important intraoperative characteristic that may dictate operative dissection techniques and/or instruments used for tumor removal during endoscopic endonasal approaches (EEAs). The impact of PA consistency on surgical outcomes has yet to be elucidated.

METHODS

The authors developed an objective 5-point grading scale for PA consistency based on intraoperative characteristics, including ease of tumor debulking, manipulation, and instrument selection, ranging from cystic/hemorrhagic tumors (grade 1) to calcified tumors (grade 5). The proposed grading system was prospectively assessed in 306 consecutive patients who underwent an EEA for PAs, and who were subsequently analyzed for associations with surgical outcomes, including extent of resection (EOR) and complication profiles.

RESULTS

Institutional database review identified 306 patients who underwent intraoperative assessment of PA consistency, of which 96% were macroadenomas, 70% had suprasellar extension, and 44% had cavernous sinus invasion (CSI). There were 214 (69.9%) nonfunctional PAs and 92 functional PAs (31.1%). Distribution of scores included 15 grade 1 tumors (4.9%), 112 grade 2 tumors (36.6%), 125 grade 3 tumors (40.8%), 52 grade 4 tumors (17%), and 2 grade 5 tumors (0.7%). Compared to grade 1/2 and grade 3 PAs, grade 4/5 PAs were significantly larger (22.5 vs 26.6 vs 27.4 mm, p < 0.01), more likely to exhibit CSI (39% vs 42% vs 59%, p < 0.05), and trended toward nonfunctionality (67% vs 68% vs 82%, p = 0.086). Although there was no association between PA consistency and preoperative headaches or visual dysfunction, grade 4/5 PAs trended toward preoperative (p = 0.058) and postoperative panhypopituitarism (p = 0.066). Patients with preoperative visual dysfunction experienced greater improvement if they had a grade 1/2 PA (p < 0.05). Intraoperative CSF leaks were noted in 32% of cases and were more common with higher-consistency-grade tumors (p = 0.048), although this difference did not translate to postoperative CSF leaks. Gross-total resection (%) was more likely with lower PA consistency score as follows: grade 1/2 (60%), grade 3 (50%), grade 4/5 (44%; p = 0.045). Extracapsular techniques were almost exclusively performed in grade 4/5 PAs. Assignment of scores showed low variance and high reproducibility, with an intraclass correlation coefficient of 0.905 (95% CI 0.815-0.958), indicating excellent interrater reliability.

CONCLUSIONS

These findings demonstrate clinical validity of the proposed intraoperative grading scale with respect to PA subtype, neuroimaging features, EOR, and endocrine complications. Future studies will assess the relation of PA consistency to preoperative MRI findings to accurately predict consistency, thereby allowing the surgeon to tailor the exposure and prepare for varying resection strategies.

Peel-off resection of the pituitary gland for functional pituitary adenomas: pathological significance and impact on pituitary function

PURPOSE

Functional pituitary adenomas (FPAs) lacking a well-defined pseudocapsule can invade the adjacent pituitary gland. In such situations, peel-off resection of the adjacent pituitary gland after selective adenomectomy might lead to complete tumor removal, resulting in optimal endocrinological outcomes. Here, we present the significance of peel-off resection of the pituitary gland in patients with FPA in whom complete extracapsular tumor removal cannot be achieved.

METHODS

We performed a retrospective review of 21 patients with FPA who underwent transsphenoidal surgery (TSS). After selective adenomectomy, peel-off resection of the adjacent pituitary gland was performed in 13 patients because complete extracapsular resection could not be achieved, while peel-off resection was not performed in the remaining 8 patients because complete extracapsular resection was accomplished. The clinical outcomes of these groups were compared. The pituitary tissues obtained by peel-off resection were pathologically examined for tumor cells.

RESULTS

Early postoperative biochemical remission was achieved in 20 patients (95.2%). Anterior pituitary functions were not aggravated postoperatively in any patient: however, transient diabetes insipidus (DI) occurred in 2 patients. There were no statistically significant differences in the clinical outcomes of the two groups. A pseudocapsule was pathologically detected in the adjacent anterior pituitary even in patients in whom no pseudocapsule was intraoperatively detected. Tumor cells were pathologically detected in 7 (58.3%) of 12 pituitary tissues examined.

CONCLUSIONS

Peel-off resection of the pituitary gland, which can remove a small tumor cell remnant in the adjacent pituitary, might maximize the effectiveness of TSS with minimal impact on postoperative pituitary function.

Removal of the Medial Wall of the Cavernous Sinus for Functional Pituitary Adenomas: A Technical Report and Pathologic Significance

BACKGROUND

Removal of the medial wall of the cavernous sinus (MW) is challenging for neurosurgeons. We describe a practical method of endoscopic MW removal via endonasal transsphenoidal approach to minimalize intraoperative blood loss and postoperative morbidities. We also present the pathologic significance of this technique for functional pituitary adenomas (FPAs).

METHODS

We performed MW removal in patients with FPA with no well-defined pseudocapsule and a tumor in direct contact with the MW. The MW was judged to have tumor invasion based on the intraoperative appearance, and it was removed regardless of the appearance of MW involvement. Intraoperative findings and postoperative clinical, endocrinologic, and pathologic outcomes were retrospectively reviewed.

RESULTS

Fourteen patients underwent MW removal for FPA, including 12 patients with acromegaly and 2 with Cushing disease. Mean intraoperative blood loss was 170 mL (range, 32-400 mL), and none of the patients required blood transfusion. Among the 7 patients without intraoperative apparent MW involvement, 4 (57.1%) had pathologically confirmed tumor invasion into the MW (occult invasion). Biochemical remission by surgery alone was achieved in 13 patients (92.9%). Transient oculomotor palsy occurred in 1 patient (7.1%).

CONCLUSIONS

Occult tumor invasion into the MW was often detected in patients with FPA without a well-defined pseudocapsule but in direct contact with the MW. Our technique can enhance the effectiveness of surgery with minimal postoperative morbidities.

Resection of pituitary macroadenomas via the pseudocapsule along the posterior tumor margin: a cohort study and technical note

OBJECTIVE Extracapsular resection of pituitary microadenomas improves remission rates, but the application of pseudocapsular techniques for macroadenomas has not been well described. In larger tumors, the extremely thin, compressed normal gland or its complete absence along the tumor's anterior surface limits the application of the traditional pseudocapsular technique that can be used for microadenomas. However, in the authors' experience, the interface between the pseudocapsule at the posterior margin of the adenoma and the compressed normal gland behind it is universally present, providing a surgical dissection plane. In mid-2010, the authors began using a new surgical technique to identify and use this interface for the resection of larger macroadenomas, a technique that can be used with the microscope or the endoscope. METHODS The authors performed a cohort study using prospectively collected preoperative imaging reports and operative details and retrospectively reviewed postoperative images and clinical follow-up of patients with a pituitary macroadenoma 20-40 mm in maximum diameter undergoing microscopic transsphenoidal resection. Since dissection of the tumor capsule only pertains to encapsulated tumor within the sella and not to tumor invading the cavernous sinus, assessment of tumor removal of noninvasive tumors emphasized the entire tumor, while that of invasive tumors emphasized the intrasellar component only. The incidence of residual tumor on postoperative imaging, new-onset endocrinopathy, and recovery of preoperative pituitary deficits was compared between patients who underwent surgery before (Group A) and after (Group B) implementation of the new technique. RESULTS There were 34 consecutive patients in Group A and 74 consecutive patients in Group B. Tumors in 18 (53%) Group A and 40 (54%) Group B patients had no evidence of cavernous sinus invasion on MRI. Use of the posterior pseudocapsule technique reduced the incidence of intrasellar residual tumor on postoperative MRI for tumors without cavernous sinus invasion (39% [Group A] vs 10%, p < 0.05) and in all tumors regardless of invasion (50% vs 18%, p < 0.005). The incidence of new endocrinopathy was less likely (25% vs 12%, p = 0.098) and the recovery of prior deficits more likely (13% vs 27%, p = 0.199) among patients treated using the pseudocapsule approach, although the differences are not statistically significant. CONCLUSIONS Use of the posterior pseudocapsule dissection plane can enhance the resection of pituitary macroadenomas.

The Surgical Side Effects of Pseudocapsular Resection in Nonfunctioning Pituitary Adenomas

OBJECTIVE

Pseudocapsular resection is a useful surgical technique for removing functioning pituitary adenomas; however, the significance of this procedure in nonfunctioning pituitary adenomas (NFPAs) had not been discussed in detail. We clarify the safety of pseudocapsular resection in NFPAs based on the incidence of surgical complications and evaluation of pituitary function.

METHODS

In 143 patients, initial surgery for NFPAs was performed with preoperative and postoperative pituitary provocation tests. Patients were categorized into 3 groups: total group (n = 65), in which the pseudocapsule was totally removed; partial group (n = 11), in which the pseudocapsule was partially removed; and nonremoval group (n = 67), in which the pseudocapsule was not removed or did not exist. The main outcome measure was the incidence of surgical complications and postoperative pituitary functions.

RESULTS

Intraoperative cerebrospinal fluid leakage and temporary diabetes insipidus occurred more frequently in the total group than in the nonremoval group; however, the differences were not statistically significant. There was no difference in the incidence of any other complications, including postoperative cerebrospinal fluid leakage and permanent diabetes insipidus, between the total and nonremoval groups. Postoperative anterior pituitary function improved to the same degree in both the total and the nonremoval groups. Univariate and multivariate analyses revealed that pseudocapsular resection was not a factor in the postoperative deterioration of pituitary function.

CONCLUSIONS

Pseudocapsular resection in NFPAs does not increase the risk of surgical complications or aggravate postoperative pituitary function.

Time to Revive the Value of the Pseudocapsule in Endoscopic Endonasal Transsphenoidal Surgery for Growth Hormone Adenomas

OBJECTIVE

To investigate the role of endoscopic endonasal transsphenoidal surgery and the pseudocapsule in the treatment of growth hormone adenomas.

METHODS

The study included 43 patients (age range, 21-64 years) with growth hormone adenomas treated with an endoscopic endonasal approach. We compared the tumor characteristics and surgical outcomes of cases with (group A, 21 cases, from November 2013 to January 2015) and without (group B, 22 cases, from October 2011 to October 2013) extra-pseudocapsule resection.

RESULTS

The preoperative demographics, tumor characteristics, and surgical complications were not significantly different between groups A and B. Postoperative remission without adjuvant therapy was achieved in 18 of 21 cases (85.7%) in group A, which was significantly greater than that observed in group B (12 of 22 cases [54.4%]). In group A, the pseudocapsules were verified by endoscopy and histopathology. The pseudocapsule was removed en bloc with the whole adenoma in only 5 cases (23.8%). For the remaining 16 patients (76.2%), following extra-pseudocapsule dissection, incomplete pseudocapsule removals with intracapsule procedures were achieved.

CONCLUSIONS

The combination of extra-pseudocapsule resection and endoscopy led to a high rate of gross total tumor resection and endocrinologicl remission in acromegalic patients compared with the group with intracapsular resection. Extra-pseudocapsule resection resulted in no additional postoperative complications.

Surgery induced hypopituitarism in acromegalic patients: a systematic review and meta-analysis of the results

PURPOSE

Hypopituitarism is a possible complication of the surgical treatment of acromegaly. However, there is a wide variability in the incidence rates of surgery-induced hypopituitarism. The purpose of this study was the systematic collection and synthesis of information on the incidence rates of hypopituitarism, panhypopituitarism, specific axis deficiencies and diabetes insipidus after surgery for acromegaly treatment.

METHODS

We systematically reviewed all the papers that have reported pituitary deficits after surgery for acromegaly published up until December 2014, in the PubMed database. We identified 92 studies enrolling 6988 patients. A meta-analysis was performed to evaluate the incidence rates. We also performed several subgroup analyses to evaluate the impact of both surgical technique, and treatment prior to surgery, on the results.

RESULTS

The weighted incidence rates were 12.79 % for hypopituitarism (95 % CI 9.88-16.00 %), 2.50 % for panhypopituitarism (95 % CI 1.24-4.15 %), 6.50 % for ACTH deficiency (95 % CI 4.07-9.44 %), 4.39 % for TSH deficiency (95 % CI 2.99-6.04 %), 6.70 % for FSH/LH deficiency (95 % CI 3.89-10.17 %), 14.95 % for GH deficiency (95 % CI 7.25-24.64 %), 10.05 % for transient (95 % CI 7.18-13.33 %) and 2.42 % for permanent diabetes insipidus (95 % CI 1.70-3.27 %).

CONCLUSION

Our study provides new data on the incidence rates of hypopituitarism, specific pituitary axis deficiencies and diabetes insipidus after surgical treatment of acromegaly. Somatotroph function appears to be more prone to deficit than the other axes. However, there is a high heterogeneity between studies and several factors may influence the incidence of hypopituitarism.

Extracapsular en bloc resection in pituitary adenoma surgery

PURPOSE

A pituitary pseudocapsule often contains tumor tissue and should be removed for radical resection. It can be used as a surgical plane for more radical resection of the tumor in many cases of pituitary adenomas. We evaluated the advantages and disadvantages of extracapsular en bloc capsulectomy.

METHODS

From 1992 until 2011, 1,089 treated patients were grouped according to the resection technique: en bloc capsulectomy, fragmented capsulectomy, or piecemeal resection. Their surgical and endocrinological outcomes and complications were evaluated.

RESULTS

Extracapsular tumor resection was performed in 263 patients; en bloc capsulectomy in 94 patients and fragmented capsulectomy in 169, whereas piecemeal resection was performed in 826. Extracapsular resection was performed more frequently in prolactin- and thyroid-stimulating hormone-secreting tumors. Total resection was more frequently achieved in extracapsular resection and its chance was 100% when tumors were removed in an en bloc fashion. For the functioning pituitary adenomas, endocrinological remission was achieved in all patients whose tumors were removed in an en bloc fashion and there was no recurrence. Postoperative cerebrospinal fluid (CSF) rhinorrhea developed in 4.2 and 2.7% in the extracapsular resection group and the piecemeal resection groups, respectively. The chance of postoperative aggravation of pituitary function was not statistically different between groups.

CONCLUSIONS

Extracapsular resection is critical for radical tumor resection and endocrinological remission. The removal of a pseudocapsule does not increase the risk of postoperative hypopituitarism nor postoperative CSF rhinorrhea.

Surgical management of Cushing's disease

BACKGROUND

Transsphenoidal selective adenomectomy is the first-line treatment for Cushing's disease. At experienced centers, early remission rates after transsphenoidal surgery range from 65 to 98%, however disease relapse frequently occurs with rates ranging from 2 to 35% at long-term follow up.

METHODS

This article discusses recently reported studies on the surgical outcomes from transsphenoidal surgery for Cushing's disease.

CONCLUSIONS

One of the keys to a successful long-term surgical outcome is meticulous dissection using the adenoma's pseudocapsule as a surgical plane for complete resection. MRI-negative and invasive ACTH-secreting adenomas pose particular challenges for pituitary surgeons.

Contemporary neurosurgical techniques for pituitary tumor resection

Approximately 5,000 trans-sphenoidal surgeries are performed for resection of pituitary tumors each year in the United States. The rise in popularity of the trans-spehnoidal approach, though described nearly a century ago, has been facilitated over the last decades by advances in technique and technology. In this review, we discuss the relative strengths of microscopic and endoscopic techniques for pituitary tumor resection. However, despite being the standard of care for patients with most pituitary tumors, cure rates for many subtypes of pituitary lesions, such as secretory macroadenomas or tumors with significant cavernous sinus invasion, remain unsatisfactory. We also describe two more recent advances in neurosurgical technique which may offer promise of increased rates of surgical cure: pseudocapsular resection and cavernous sinus approaches.

Endoscopic distinction between capsule and pseudocapsule of pituitary adenomas

BACKGROUND

Pseudocapsules were first identified in pituitary adenoma surgery in 1936. Since then, the distinction between pituitary capsules and pseudocapsules has been unclear, and the definitions of these entities have varied. In this study, pituitary capsules and extracapsular dissection were examined retrospectively, intra- and extrapseudocapsular resection was evaluated, and dissection of the pituitary adenoma and pseudocapsule was examined prospectively.

METHODS

Between January 2009 and May 2012, endoscopic transsphenoidal pituitary surgery was performed on 224 patients in the Department of Neurosurgery, Kocaeli University Faculty of Medicine, Turkey. Data for 174 patients were analyzed retrospectively between January 2009 and December 2011, and 50 patients treated between December 2011 and May 2012 were included in a prospective study.

RESULTS

In the retrospective phase of the study, capsules were examined in 21 of the 174 patients on whom extracapsular resection had been performed. In the 50 cases treated between December 2011 and May 2012, dissection of the pituitary capsule, adenohypophysis, and pseudocapsule was performed. In 30 patients in the prospective phase of the study, pseudocapsules were identified during intraoperative endoscopic observation. Remission was achieved in 28 of 33 functioning adenomas in the prospective study. The mean follow-up period in this group was 13 months.

CONCLUSION

The endoscopic and histopathological evidence provided in this study demonstrates that the pituitary capsule and pseudocapsule are distinct structures. In addition, it is also shown that extracapsular dissection can be performed in functioning adenomas that invade the suprasellar region. Significantly higher rates of total resection and higher remission rates were observed in cases where extra- and intrapseudocapsular dissection was required.

Surgical and endocrinological outcomes in the treatment of growth hormone-secreting pituitary adenomas according to the shift of surgical paradigm

BACKGROUND

Extensive data exist regarding the success rates and long-term outcomes of transsphenoidal adenomectomy (TSA) of growth hormone (GH)-secreting pituitary tumors; however, few data exist regarding the extent of adenomectomy.

OBJECTIVE

To evaluate surgical outcomes for the treatment of GH-secreting pituitary adenomas with regard to the extent of adenomectomy.

METHODS

A retrospective study of 282 patients with GH-secreting pituitary tumors who underwent TSA. Three surgical paradigms (1, 2, and 3) were applied, all of which differed in extent of adenomectomy. All participants were evaluated with oral glucose tolerance tests (OGTTs) at 6-month intervals for 1.5 years and combined pituitary function tests at 1.5-year intervals after TSA. All surgeries were conducted by a single neurosurgeon at a single medical center. Biochemical remission was defined with insulinlike growth factor 1 and OGTT results.

RESULTS

The overall surgical remission rates were 89%, 87%, 64%, 70%, and 50% (nadir GH <1 ng/mL on OGTTs: 96%, 95%, 73%, 84%, and 56%) for modified Hardy classifications I, II, IIIA, IIIB, and IV, respectively. The remission rates for modified Hardy classification I-IIIB improved to 42%, 68%, and 84% after application of surgical paradigms 1, 2, and 3, respectively (P = .002). Aggressive surgical resection did not worsen hypopituitarism. Among the 42 patients with modified Hardy classification IV, 24 (57%) achieved remission without recurrence after applying the aggressive paradigm 3 surgery.

CONCLUSION

An aggressive surgical approach may be critical to managing GH-secreting pituitary adenomas and does not increase the risk of postoperative hypopituitarism.

ABBREVIATIONS

ACTH, corticotropinCPFT, combined pituitary function testCV, coefficient of variationGH, growth hormoneOGTT, oral glucose tolerance testPRL, prolactinTSA, transsphenoidal adenomectomyTSH, thyroid-stimulating hormone.

Transsphenoidal microsurgical results of female patients with prolactinomas

OBJECTIVE

We investigated surgical cure rate and surgical complications of patients with macroprolactinomas who desired pregnancy to evaluate the efficacy of transsphenoidal surgery.

METHODS

Surgical cure rate was investigated in 138 female patients who were under 40 years old.

RESULTS

We found a significant correlation between serum prolactin levels and adenoma volume (r=0.004; p<0.0001), adenoma volume and age (r=-0.213; p<0.03), and proliferative index of the adenoma and age (r=-0.15; p<0.007). Seventy-seven out of 81 patients with enclosed macroadenoma were considered cured, and therefore the overall surgical cure rate was 95%. However, during long-term follow-up, recurrence of adenomas with hyperprolactinemia was seen in 5 out of 81 patients (6%), and the long-term cure rate in patients with enclosed macroadenomas was 89%. Adenomas that did not invade the cavernous sinus showed a significantly higher surgical curability and lower serum prolactin levels, and a smaller size than those adenomas that invaded the cavernous sinus.

CONCLUSIONS

The long-term surgical cure rate was found to be 89% and this success rate far surpasses the complication rate of 39% during pregnancy by dopamine agonist therapy. Thus, transsphenoidal surgery should be considered as a first-line treatment for female patients who desire pregnancy.

A novel simple real-time electrooculographic monitoring system during transsphenoidal surgeries to prevent postoperative extraocular motor nerve dysfunction

In transsphenoidal surgery (TSS) for pituitary tumors, the use of endoscopes allows approach to the lateral sides in and around the cavernous sinus. However, this approach is often associated with a risk of cranial nerve dysfunction causing impaired extraocular movement. We employed a novel, simple, and real-time monitoring system using electrooculography during TSS to avoid postoperative extraocular motor nerve dysfunction. A conventional electroencephalograph, which is available in every hospital, was used to detect effects induced by intraoperative manipulation on the cranial nerves related to extraocular movement (EOM) during TSS for pituitary adenomas. One hundred patients with pituitary adenomas who underwent endonasal endoscope-assisted TSS with EOM monitoring were included in the present study. When the extraocular motor nerves were stimulated mechanically directly or even indirectly by surgical procedures, abnormal extraocular muscle responses [electrooculograms (EOGm)] appeared on the monitor screen. When repeated or continuous EOGm were recorded, surgical procedures were discontinued briefly for around 5 to 10 s. The EOGm disappeared promptly when surgical procedures were stopped. Permanent extraocular dysfunction did not occur in the present series of patients. One, who was the fifth patient in the present series, of 100 patients (1.0 %) had transient delayed diplopia after TSS. We have not experienced any more postoperative EOM dysfunction since the first case. EOM monitoring during TSS is a novel, efficient, and simple method to prevent postoperative cranial nerve palsy related to EOM.

Transsphenoidal pseudocapsule-based extracapsular resection for pituitary adenomas

BACKGROUND

In the past several years, increasing attention has been paid to the utility of a pseudocapsule in transphenoidal surgery for pituitary adenomas. However, prior studies focused more on the histological structure of the pseudocapsule and surgical technique. The objective of this study was to evaluate the overall therapeutic effectiveness of transsphenoidal pseudocapsule-based extracapsular resection for pituitary adenomas.

METHODS

Between January 2004 and October 2007, 78 patients with pituitary adenomas underwent transsphenoidal pseudocapsule-based extracapsular removal surgery (extracapsular resection group, ER group). During the same period, 64 patients underwent transsphenoidal intracapsular resection operations (intracapsular resection group, IR group).

RESULTS

Complete resection rates were achieved in 90.6%, 84.6% and 65.5%, 52.6% of modified Hardy types II and III in the ER and IR groups, showing a significant difference (both P < 0.05). Statistical significance in the remission rates was also found between the two groups with modified Hardy types II and III, respectively (both P < 0.05). Complications occurred in 29.5% of the ER group and 26.6% of the IR group, with no difference between groups (P > 0.05). The recurrence rate of the ER group (2.56%) was lower than that of the IR group (14.06%).

CONCLUSION

The transsphenoidal pseudocapsule-based extracapsular resection approach provides a more effective and safe alternative compared to the traditional intracapsular one because of its higher tumor removal and remission rates, and lower recurrence rate.

The pseudocapsule surrounding a pituitary adenoma and its clinical significance

The transsphenoidal approach is currently considered the preferred first-line treatment for pituitary adenoma. With the discovery and application of the pseudocapsule surrounding a pituitary adenoma, transsphenoidal surgery of pituitary adenoma further falls into two categories: "extracapsular" and traditional "intracapsular" resection methods, on the basis of where dissection is performed with respect to the pseudocapsule. Thus, the pseudocapsule can be used as a plane to guide the operation, helps in total resection of pituitary adenoma, and can guide subsequent treatment after surgery.

Histological findings at the boundary of craniopharyngiomas

Although a craniopharyngioma is grossly well circumscribed, microscopically the borders are frequently irregular and may be associated with gliosis in the adjacent brain tissue. In the current study, we investigated the histology of the interface between craniopharyngiomas and surrounding normal structures such as the hypothalamus and pituitary gland. Histologically, we classified the findings at the boundary of craniopharyngiomas into three types. In type 1, a relatively thick capsule-like tissue was identified at the boundary between the craniopharyngioma and surrounding normal structure composed of tumor cells and inflammatory changes. In type 2, a craniopharyngioma had a relatively clear cleavage between the surrounding gliosis. In type 3, the boundary had some interdigitation of the tumor in the surrounding gliotic layer adjacent to the craniopharyngioma. In types 1 and 3, surgeons may fail to accomplish complete resection of the tumor. These histological features may result in recurrence of craniopharyngioma even after gross total resection.

Tumor tissue identification in the pseudocapsule of pituitary adenoma: should the pseudocapsule be removed for total resection of pituitary adenoma?

OBJECTIVE

The microsurgical pseudocapsule can be found in the transition zone between an adenoma and the surrounding normal pituitary tissue. We investigated the precise histology of the pseudocapsule. Furthermore, we evaluated the remission rate, the changes in pituitary function, and the recurrence rate after intensive resection of the pseudocapsule.

METHODS

In 616 patients with pituitary adenomas (Hardy Types I-III) over a period of 14 years, we introduced intensive resection of the microsurgical pseudocapsule to achieve complete tumor removal. A combined pituitary function test and radiological study were performed on the patients before surgery, 1 year after surgery, and at subsequent 1.5-year intervals 2 to 13 years postoperatively.

RESULTS

Microsurgical pseudocapsules were identified in 343 (55.7%) of 616 patients, and the distinct microsurgical pseudocapsules were observed in 180 (52.5%) of these patients. In the remaining 163 patients, the microsurgical pseudocapsules were incompletely developed. Tumor cluster infiltration was present in the pseudocapsule in 71 (43.6%) of these patients. Aggressive resection of the microsurgical pseudocapsule was more often required in larger tumors than in smaller ones. The presence of a pseudocapsule was slightly more frequent in prolactin-secreting tumors (70.9%) than in growth hormone-secreting (55.0%) and adrenocorticotropic hormone-secreting (40.0%) tumors. In the 243 patients of the total resection group who underwent combined pituitary function tests more than 2 times after surgery, the surgical remission rate was 99.1% in clinically nonfunctional tumors, 88% in growth hormone-secreting, 70.6% in prolactin-secreting, and 100% in adrenocorticotropic hormone-secreting tumors. The surgical remission rate was 86.2% in the presence of a pseudocapsule and 94.3% in the absence of a pseudocapsule. Preoperative hypopituitarism improved in 140 patients (57.6%), persisted in 47 patients (19.3%), and was aggravated in 33 patients (13.6%). There was no statistical difference in improvement or deterioration of pituitary function according to the existence or absence of the pseudocapsule. The tumor recurrence rate was 0.8% in the total resection group and was 42.1% in the subtotal resection group.

CONCLUSION

We have shown that tumor tissue is frequently present within the pseudocapsule, suggesting that any tumor remnant in the pseudocapsule could be a source of recurrence and an obstacle to achieving complete remission. These results indicate that intensive resection of the pseudocapsule could result in a higher remission rate without deteriorating pituitary function.

Endoscopic trans-sphenoidal surgery for pituitary tumors

Trans-sphenoidal surgery, which is the most widely used technique for the treatment of pituitary tumors, has continued to evolve by introducing new approaches and technologies, such as the direct endonasal route and the endoscope. The endonasal approach is a minimally invasive route to the sella turcica with the advantages of using a simpler and more rapid nasal dissection and eliminating the nasal and lip complications. Restricted exposure provided by the endonasal approach is overcome by combined use of an endoscope that provides a more panoramic view of the surgical field beyond the area covered by the operating microscope. An operating microscope permits binocular vision and bimanual technique, which are familiar to neurosurgeons. Neurosurgeons should exploit the advantages of both modalities for the benefit of patients. This review describes the advances in trans-sphenoidal surgery focusing on the endoscopic approach.

Novel flexible forceps for endoscopic transsphenoidal resection of pituitary tumors: technical report

The endoscope has become an essential tool for transsphenoidal pituitary surgeries because of the panoramic view and the ability to visualize structures beyond the direct line of vision. However, the regular dedicated instruments for these surgeries sometimes do not reach the areas visualized by an angled endoscope, and instrument maneuverability is limited. To overcome or minimize these problems, we constructed a new flexible tumor forceps that can be manipulated to change shape after placing into the surgical fields via the endonasal or sublabial route, to reach any desirable location for tumor dissection and excision. We applied this newly developed instrument in endonasal endoscopic resection complementing microsurgical procedure in 20 cases of pituitary tumors. The flexible forceps was able to access sites where regular dedicated instruments for transsphenoidal pituitary surgeries could not readily reach despite endoscopic visualization. No complication was observed in the present series, confirming the safety of the newly designed flexible forceps. Our newly developed flexible forceps improves the instrument maneuverability of endoscopic transsphenoidal resection of pituitary tumors, especially those located laterally at the cavernous sinuses or with frontal extension. The use of this instrument makes the best use of endoscopic panoramic visualization for tumor removal.

Perioperative plasma active and total ghrelin levels are reduced in acromegaly when compared with in nonfunctioning pituitary tumours even after normalization of serum GH

OBJECTIVE

Ghrelin is a novel gastric peptide known to stimulate GH secretion, but the relationship between ghrelin and the GH-insulin-like growth factor (IGF)-1 axis in GH excess or deficiency is poorly understood. This study investigated dysregulation of ghrelin secretion in acromegaly and its short-term postoperative recovery.

METHODS

A prospective study was conducted on eight patients who underwent complete transsphenoidal resection of GH-producing pituitary adenomas (acromegaly group) and 22 for endocrinologically nonfunctioning pituitary tumours (control group). Active and total plasma ghrelin levels were measured serially before and after surgery.

RESULTS

Preoperative active and total plasma ghrelin concentrations (mean +/- SD; fmol/ml) were significantly reduced in acromegalic patients when compared with those in the controls (9.6 +/- 4.3 and 157.4 +/- 65.6 vs. 21.8 +/- 13.0 and 267.1 +/- 111.4; P = 0.023 and P = 0.021, respectively). Both levels were still significantly suppressed on postoperative Day 7 in the acromegaly group when compared with those in the control group (11.7 +/- 4.3 and 197.8 +/- 68.9 vs. 22.5 +/- 12.6 and 302.7 +/- 100.0; P = 0.038 and P = 0.018, respectively). The ratios of active to total ghrelin were not significantly different between the two groups before and after operation. In acromegalic patients, active and total ghrelin levels remained significantly suppressed even after normalization of serum GH levels.

CONCLUSIONS

The putative negative feedback mechanism of GH on ghrelin secretion may in part account for the low ghrelin levels observed in acromegalic patients, and the mechanism may persist even after normalization of serum GH.

Development of a histological pseudocapsule and its use as a surgical capsule in the excision of pituitary tumors

OBJECT

The presence of a histological pseudocapsule around pituitary tumors was noted in the early 1900s. Since that time there has been no emphasis on the sequence of the stages of its development or on the relationship between these stages and the capacity to identify very small pituitary tumors at surgery in patients in whom preoperative imaging has been nondiagnostic. In addition, limited emphasis has been given to the pseudocapsule's use for selective and complete resection of pituitary adenomas.

METHODS

The development of the pseudocapsule was examined by performing histological analysis of portions of pituitary glands removed during 805 operations for Cushing disease. Twenty-five adenomas, each measuring between 0.25 and 4 mm in maximum diameter, were detected in the excised specimens; 17 were adenocorticotropic hormone-positive adenomas and eight were incidental tumors (four prolactin-secreting and four nonsecreting lesions). In 16 tumors the size of the adenoma could be established. The distribution of tumor size in relation to the presence of a histological pseudocapsule indicates a transition from the absence of a reticulin capsule (tumor diameter < or =1 mm) through the initial compression of surrounding tissue (tumor diameter 1-2 mm) to the presence of a multilayered reticulin capsule observed when adenomas become larger (tumor diameter 2-3 mm).

CONCLUSIONS

The absence of a reticulin capsule in cases of very small tumors may contribute to limited localization of these lesions during surgical exploration of the pituitary gland. In this article the authors describe surgical techniques in which the histological pseudocapsule is used as a surgical capsule during pituitary surgery. In their experience, recognition of this surgical capsule and its use at surgery has contributed to the identification of microadenomas buried in the pituitary gland, aided the recognition of subtle invasion of the pituitary capsule and contiguous dura mater, and enhanced the consistency of complete tumor excision with small and large tumors.

Hyponatremia after transsphenoidal surgery for hypothalamo-pituitary tumors

Transient diabetes insipidus is a well-known complication after transsphenoidal surgery (TSS). On the other hand, transient hyponatremia has been reported as being a delayed complication of TSS. Transient hyponatremia has been attributed to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), but the details of hyponatremia have not been clarified. In the present study, we retrospectively reviewed 110 consecutive patients (39 males and 71 females, age 9-80 years) operated on transsphenoidally for pituitary and hypothalamic tumors. We investigated the frequency, time of onset, duration of hyponatremia after TSS, and analyzed possible factors associated with it. A postoperative sodium concentration <135 mEq/l was observed in 29 (26%) patients. Five patients were excluded from this study because their hyponatremia could be due to either overdose of desmopressin or SIADH for meningitis. Therefore, we investigated 24 (22%) patients with hyponatremia in this study. The sodium levels in the patients with hyponatremia ranged from 110 to 134, with a mean of 126.2 +/- 5.3 mEq/l. Hyponatremia was observed on average on postoperative day 9.5 +/- 2.4, the serum sodium levels normalized within 3.8 +/- 1.7 days. Hyponatremia occurred in patients with non-functioning pituitary adenoma (26%, 11/42), Rathke's cleft cyst (29%, 5/17), prolactinoma (31%, 4/13) and acromegaly (15%, 4/27). 18 patients (75%, 6/24) who developed hyponatremia had macrotumor (>10 mm), and 6 patients (25%, 6/24) had microtumor. The plasma arginine vasopressin (AVP) levels in the patients with hyponatremia ranged from 0.21 to 2.1, with a mean of 0.79 +/- 0.46 pg/ml, and the levels were inversely correlated with plasma osmolality (r = -0.80, p = 0.002). The urine to plasma osmolality ratios were >1. All the patients received appropriate hormonal replacement, including hydrocortisone. These data showed that postoperative hyponatremia after TSS was not rare, and the hyponatremia was mainly associated with SIADH. As the hyponatremia could be a life-threatening complication, all patients should be screened for serum electrolytes after TSS.