Loss of Insulin Resistance after Roux-en-Y Gastric Bypass Surgery: a Time Course Study

Background: Gastric bypass has repeatedly been shown to improve and even cure type 2 diabetes by substantially improving insulin resistance. The mechanism by which it achieves this is not currently known, but some have hypothesized that there may be important humoral effects brought about by the bypass of the stomach, duodenum or proximal jejunum. A better understanding of the time course of the changes in insulin resistance after surgery might assist our understanding of potential mechanisms. Methods: Intravenous glucose tolerance tests (IVGTT) were performed in 26 severely obese patients on the morning of gastric bypass surgery and again 6 days later. In addition insulin resistance was assessed in 71 patients undergoing gastric bypass surgery by the homeostasis model assessment (HOMA) method before surgery, and again at 6 days, 3, 6, 9, and 12 months. Patients were divided into 3 groups for analysis: diabetics, impaired glucose tolerance and normal glucose tolerance. Results: All 3 groups of patients were noted to have insulin resistance prior to surgery. This was greatest in the diabetic patients, as indicated by HOMA. There was marked loss of/improvement in insulin resistance within 6 days of gastric bypass by both IVGTT and HOMA methods in all groups, which was maintained over the 12-month period. The study included 31 diabetic patients, of whom only 3 required medication following hospital discharge. Conclusion: The changes in insulin resistance seen after gastric bypass, which are responsible for the resolution or improvement of type 2 diabetes occur within 6 days of the surgery, before any appreciable weight loss has occurred. This finding has implications for our understanding of the mechanism of insulin resistance in severely obese patients and is consistent with a humoral mechanism emanating from the GI tract.     

Endoscopic transsphenoidal resection of a mid-clival meningioma

Advances in transsphenoidal endoscopic surgery have allowed difficult clival tumours such as meningiomas causing effacement of the pons and basilar artery to be approached by this technique. We report a clival meningioma resected via a transsphenoidal endoscopic approach.     

Presacral neuroenteric fistula in a newborn presenting with an epidural abscess: case report and review of the literature

We describe a newborn infant (<24 hours of age) who presented with mild swelling on the back and buttocks attributable to a neuroenteric fistula complicated by an epidural parasacral abscess infected with mixed coliforms. Epidural abscesses in infancy are extremely rare, and one has not been observed previously in the newborn period. The infant was surprisingly mildly affected. Prompt intervention led to an excellent outcome. Coliforms may colonize the infant gut in <24 hours, even in the developed world. Unexplained swellings on the backs of infants should lead to a search for underlying malformations and an early surgical review, which is best conducted with a combined pediatric surgical and neurosurgical approach.     

Endoscopic endonasal transsphenoidal surgery: a mentoring surgical model

Background: We report the experience of endoscopic endonasal transsphenoidal surgery (EETS) for resection of pituitary region tumours at Wellington, the central regional referral centre for neurosurgery in New Zealand, and discuss the collaborative mentoring surgical model that enhanced the learning experience. Method: Between January 2007 and June 2009, a total of 47 operations on 46 patients were performed and reviewed retrospectively. All patients had perioperative clinical assessment, hormonal profile and magnetic resonance imaging studies for residual/recurrent disease. The collaborative model utilized two neurosurgeons with experience in the microsurgical resection of pituitary tumours: an endoscopic skull base fellowship trained rhinologist and an endoscopic skull base rhinologist with more experience who visited twice a year from Adelaide, Australia. Results: The pathology results included: 30 non‐functioning pituitary adenomas, 10 secreting pituitary adenomas, 3 meningiomas, 1 chordoma, 1 anterior skull base adenocarcinoma and 1 clival prostate metastasis. Complete tumour resection was intended and achieved in 38 cases. All 10 patients with secreting adenomas achieved improvement of hormonal profile. Nineteen out of 27 cases demonstrated improvement of vision. Perioperative complications included one epistaxis, three cerebrospinal fluid fistulae, one delayed chronic subdural haematoma and one persistent diabetes insipidus. Conclusion: Our results highlight the value of a collaborative mentoring surgical model for a single centre adopting the endoscopic transsphenoidal technique and demonstrate that excellent EETS outcomes can be achieved in a smaller endoscopic skull base unit in Australasia during the learning phase.