Paradoxical response of a pineal immature teratoma to combination chemotherapy

A case of primary intracranial germ cell tumour is reported in a 5-year- old Chinese boy who presented with symptoms and signs of increased intracranial pressure. Computed tomography (CT) scan of the brain revealed a multicystic tumour over the pineal region. Stereotactic biopsy yielded enteric epithelium and isolated cells with hyperchromatic nuclei and high nuclear-to-cytoplasmic ratio, suggesting the diagnosis of an immature teratoma. Grossly elevated serum and cerebrospinal fluid (CSF) levels of α- fetoprotein and mildly elevated levels of β human chorionic gonadotrophin suggested the simultaneous presence of embryonal tissues. Combination chemotherapy with cisplatin, etoposide, and bleomycin resulted in a gradual but complete normalisation of the serum and CSF tumour markers. Paradoxically, the patient's consciousness deteriorated and repeat CT scan after 3 months of treatment showed that the tumour was actually increasing in size. Complete surgical removal was attempted and histologic sections of the specimen revealed only mature teratomatous tissues. The child is now well and remains disease-free with minimal left hemiparesis 12 months after completion of treatment. This case illustrates the importance of combined neoadjuvant chemotherapy and surgery in the management of intracranial non-germinomatous germ cell tumour harbouring both germ cell and teratomatous components, while monitoring of both biochemical and radiological parameters are necessary in assessing the clinical behaviour of mixed germ cell tumours.link_to_subscribed_fulltex

A computational fluid dynamic study of stent graft remodeling after endovascular repair of thoracic aortic dissections

Objectives: Significant stent graft remodeling commonly occurs after endovascular repair of thoracic aortic dissections because of continuing expansion of the true lumen. A suboptimal proximal landing zone, minimal oversizing, and lack of a healthy distal attachment site are unique factors affecting long-term stent graft stability. We used computational fluid dynamic techniques to analyze the biomechanical factors associated with stent graft remodeling in these patients. Patients and Methods: A series of computational fluid dynamic models were constructed to investigate the biomechanical factors affecting the drag force on a thoracic stent graft. The resultant drag force as a net change of fluid momentum was calculated on the basis of varying three-dimensional geometry and deployment positions. A series of 12 patients with type B aortic dissections treated by thoracic stent graft and followed up for more than 12 months were then studied. Computed tomography transaxial images of each patient shortly after stent graft deployment and on subsequent follow-up were used to generate three-dimensional geometric models that were then fitted with a surface mesh. Computational fluid dynamic simulations were then performed on each stent graft model according to its geometric parameters to determine the actual change in drag force experienced by the stent graft as it remodels over time. Results: The drag force on the stent graft model increases linearly with its internal diameter and becomes highest when the deployment position is closer to the proximal arch. Aortic curvature is not a significant factor. Serial computed tomography scans of patients showed an increase in mean inlet area from 1030 mm2 to 1140 mm2, and mean outlet area from 586 mm2 to 884 mm2 (increase of 11% and 58%, respectively; P = .05, .01). These increases are associated with a change in resultant drag force on the stent graft from 21.0 N to 24.8 N (mean increase, 19.5%; range, 0%-63.2%; P = .002). There is a positive relationship between increase in drag force and increase in stent-graft area. Conclusion: The drag force on thoracic stent grafts is high. A significant change in stent-graft diameter occurs after endovascular repair for type B dissections, which is associated with an increase in hemodynamic drag force. These stent grafts may be subjected to a higher risk of distal migration, and continuing surveillance is mandatory. © 2008 The Society for Vascular Surgery.link_to_subscribed_fulltex