Submesoscale inverse energy cascade enhances Southern Ocean eddy heat transport.

Oceanic eddy-induced meridional heat transport (EHT) is an important process in the Southern Ocean heat budget, the variability of which significantly modulates global meridional overturning circulation (MOC) and Antarctic sea-ice extent. Although it is recognized that mesoscale eddies with scales of ~40-300 km greatly contribute to the EHT, the role of submesoscale eddies with scales of ~1-40 km remains unclear. Here, using two state-of-the-art high-resolution simulations (resolutions of 1/48° and 1/24°), we find that submesoscale eddies significantly enhance the total poleward EHT in the Southern Ocean with an enhancement percentage reaching 19-48% in the Antarctic Circumpolar Current band. By comparing the eddy energy budgets between the two simulations, we detect that the primary role of submesoscale eddies is to strengthen mesoscale eddies (and thus their heat transport capability) through inverse energy cascade rather than directly through submesoscale heat fluxes. Due to the submesoscale-mediated enhancement of mesoscale eddies in the 1/48° simulation, the clockwise upper cell and anti-clockwise lower cell of the residual-mean MOC in the Southern Ocean are weakened and strengthened, respectively. This finding identifies a potential route to improve the mesoscale parameterization in climate models for more accurate simulations of the MOC and sea ice variability in the Southern Ocean.

C2 dumbbell-shaped peripheral nerve sheath tumors: Surgical management and relationship with venous structures.

OBJECTIVES: This study focuses on the adjacent venous structures of tumors and their treatment in patients with second cervical (C2) dumbbell-shaped peripheral nerve sheath tumors (PNSTs). PATIENTS AND METHODS: The authors retrospectively analyzed the clinical outcome and the venous structures involved with tumors in 16 patients with C2 dumbbell-shaped PNSTs treated surgically between 2008 and 2015. RESULTS: The venous structures at the craniocervical junction could be visualized in all 16 patients on contrast-enhanced T1-weighted magnetic resonance imaging. The venous structures could be identified during surgery. The common locations of venous structures were noted as follows: the suboccipital cavernous sinus was located anterolateral and toward the top of the tumor; the vertebral venous plexus was located ventral to the tumor; and the vertebral artery venous plexus was shifted anteriorly and laterally by the tumor. Total excision was achieved in all 16 patients. Clinical improvements were observed in all 16 patients postoperatively. CONCLUSIONS: The C2 dumbbell-shaped PNSTs were closely related to the suboccipital venous structures. Understanding and proper management of these venous structures is critical for reduced bleeding and successful surgery.

[Distinguish reasons for the variety of intraoperative transcranial magnetic motor evoked potential: the anaesthesia or the operative injury].

OBJECTIVE: To find a way to discriminate operative reason from anaesthesia reason for the changes of intraoperative transcranial magnetic motor evoked potentials (MEPs). METHODS: In 26 patients under Etomidate/Fentanyl anesthesia from February 2001 to June 2004, MEPs elicited by transcranial magnetic stimulation were recorded from tibialis anterior muscles, simultaneously bispectral index (BIS) and train-of-four stimulation (TOF) were used to monitor the anesthesia depth and neuromuscular blockade respectively. MEP, BIS and measurements of TOF at different anesthesia depth and muscular relaxation were recorded synchronously, statistical analysis of this data set was done in order to find the inherent relationship between these variables. RESULTS: Under anesthesia, MEP amplitude was always positively correlated with the corresponding BIS and TOF value. A regression equation could be built, with which the MEP amplitude could be reckoned based on realtime BIS and T(1)/T(c). In case of spinal cord injury, the measured amplitude value would significantly deviate from predicted one, which suggested that the change of MEP was because of the operation, but not the anaesthesia or neuromuscular blockade. Each patient had his or her own regression equation, which was different from each other. CONCLUSIONS: The establishment of regression equation from MEPs, BIS and TOF is very useful to distinguish reasons of the changes of transcranial magnetic MEPs during surgery, and with this technique, the intraoperative MEP monitoring should be more reliable and practicable.

[The utility of neuronavigation in the microsurgery for cerebral cavernous malformations].

OBJECTIVE: To evaluate the utility of neuronavigation in the microsurgery for cerebral cavernous malformations. METHODS: In a retrospective study, 47 patients with cavernous malformations were involved from January 1995 to December 2010. Fourteen cases admitted into hospital from January 1995 to December 2002 were treated without neuronavigation (conventional group), the focus localization was based on magnetic resonance imaging (MRI) images, anatomic landmarks, and the experiences of the neurosurgeon. In the other 33 cases admitted after February 2002 to December 2010, surgeries were performed with neuronavigation using the Medtronic Stealth Station TREON or TRIA system (neuronavigation group). Excision of the cavernomas were all performed microsurgically, surrounding gliotic rim and hemosiderin stained tissue were resected in the case of epilepsy, and a few patients underwent extended hippocampal resection or multiple subpial transection. RESULTS: With the use of neuronavigation, the extent of craniotomy reduced from 5.2 cm to 3.6 cm (P < 0.01), and deeper cavernoma focuses could be treated surgically. There were no changes with regard to the mean size of the cavernomas, the mean time of surgery and hospital stay (P > 0.05), but the mean time of anaesthesia was prolonged from 164 min to 197 min (P < 0.01). Cavernomas were resected completely in all 47 cases, which was confirmed by postoperative MRI recheck. The conditions of all patients were improved or remain unchanged, and no significant differences in the clinical outcome could be evaluated between the two groups. CONCLUSIONS: Application of neuronavigation-assisted microsurgery of intracranial cavernous malformations surgery, helps reduce the surgical trauma, and has security and reliability.

[Microsurgical management of tuberculum sellae meningiomas].

OBJECTIVE: To explore the approach and efficacy of microsurgery for tuberculum sellae meningiomas. METHODS: The clinical data of 56 patients with tuberculum sellae meningiomas treated at our department from 1991 - 2009 were analyzed retrospectively. There were 20 males and 36 females with an age range of 32 - 65 years old (mean: 46). All patients underwent microsurgery through pterional, unilateral subfrontal, orbitozygomatic or supraorbital keyhole approach. RESULTS: Among these patients, there were total resection (n = 51) and subtotal resection (n = 5). Postoperatively, 53 patients recovered well, 2 had a mild disability, 1 suffered a severe disability and there was no mortality. CONCLUSION: Most cases of tuberculum sellae meningiomas can be removed safely and totally. Several approaches may be employed to achieve the best outcomes. Microsurgery can markedly boost the total resection rate of tuberculum salle meningiomas and lower the postoperative complications and mortality.

[The utility of transcranial magnetic motor evoked potential monitoring during spinal surgery].

OBJECTIVE: To evaluate the practicability and validity of transcranial magnetic motor evoked potential monitoring (TMS-MEP) during spinal surgery. METHODS: From February 2001 to June 2004, 37 patients undergoing spinal surgery were involved, anaesthesia was maintained with volatile anesthetics in 11 operations and etomidate in 26. Analgesia was provided with fentanyl, and non-depolarizing muscle relaxant was given intermittently. MEPs elicited with transcranial magnetic stimulations were recorded from tibialis anterior muscles, simultaneously bispectral index (BIS) and train-of-four stimulation (TOF) were used to monitor the anesthesia depth and neuromuscular blockade respectively. The variety of MEP and its effect on surgical operation at different anesthesia depth and muscular relaxation were observed, and the muscle strength of the patients before and after operation were compared. RESULTS: The 11 cases anesthetized with isoflurane or enflurane gave no response to TMS, the other 26 cases in which anaesthesia was maintained with etomidate and fentanyl gave satisfactory TMS-MEPs, but with significantly attenuated amplitudes and prolonged latencies (P < 0.05). Intraoperative MEP showed a grossly unchanged waveform, and its amplitude and latency had little fluctuation when anaesthesia and neuromuscular blockade maintained stable. When T(1) value of TOF at 40% - 60%, a steady MEP could be acquired and the muscular contraction after TMS should not interfere the operation.Seven of 26 cases had a MEP amplitude drop up to 50% or more during the operation, the surgical team was notified to avoid further spinal injury, at last only 1 case had a worsen muscle power after operation. CONCLUSIONS: Myogenic TMS-MEP is a valid and practicable technique for intraoperative monitoring, and the etomidate + fentanyl technique is adequate for its anesthesia. BIS and TOF monitoring are helpful to maintain the steadiness of the anesthesia and MEPs, which is very important for monitoring the changes of the MEPs.

[Microsurgical management of anterior clinoidal meningiomas].

OBJECTIVE: To explore the method and efficacy of microsurgery for anterior clinoidal meningiomas. METHODS: The clinical data of 53 patients with anterior clinoidal meningiomas treated from 1991-2009 were analyzed retrospectively. There were 15 males and 38 females. The age range was 33 - 65.5 years old (mean: 45.5). All patients underwent microsurgery through pterional, extended pterional, frontotemporal, frontotemporal and orbitozygomatic approaches. RESULTS: Of 53 patients, total, subtotal and partial resections were performed in 38, 10 and 5 cases respectively. Postoperatively, 48 patients recovered well, 4 had mild disability, 1 severe disability and no dead case. CONCLUSION: Most anterior clinoidal meningiomas can be removed safely and effectively. Several approaches may be used to achieve the best results. Microsurgical operation can offer a great aid in an effective resection of anterior clinoidal meningiomas and reduce the postoperative complications and mortality. Postoperative radiotherapy should be carried out for the residual tumor invading cavernous sinus or internal carotid artery.

[Microsurgical treatment of spinal cavernous malformation].

OBJECTIVE: To investigate the characteristics of clinical manifestations, diagnostic imaging, pathology, and microsurgical treatment of spinal cavernous malformation. METHODS: The clinical data of 28 patients with spinal cavernous malformation undergoing total resection through posterior approach during 1991-2006, all receiving MRI examination and 22 also receiving spinal DSA examination, were analyzed. RESULTS: Among the 28 cases, 8 lesions were located in the cervical segment of the spinal cord; 12 lesions in the cervical-thoracic segment; 4 lesions in the thoracic segment; 2 in the lumbar segment, and 2 in the thoraco-lumbar segment. The MRI images looked like mulberry; a black ring around the cavernoma was indicated. The spinal cord tissues around the lesion were obviously stained by the deposited hemosiderin. Follow-up of 3 months to 6 year showed no recurrence. CONCLUSION: MRI is the most reliable method for diagnosis of spinal cavernous malformation and surgical resection is the best treatment method. The key of success is meticulous surgical techniques. DSA helps differentiate spinal cavernous malformation from other arterio-venous malformations.

[Treatment of spinal cord hemangioblastoma by microoperations combined with embolization].

OBJECTIVE: To investigate the effects of microoperations combined with embolization in treatment of spinal cord hemangioblastoma. METHODS: Thirty-six patients with spinal cord hemangioblastoma, 21 males and 15 females, aged 24.2 (12-48), underwent MRI and digital abstraction angiography. Twelve of them underwent pure microsurgical treatment and 24 of them underwent operation combined with remobilization. RESULTS: MRI showed clear boundary mass, and DSA showed round or oval high density images with clear boundary and definite supplying artery. 30 cases had their tumors totally removed; and 6 cases had their tumors subtotally removed. Complete functional recovery was seen in 27 of the 36 patients (67%). Four patients resumed their self-care ability,and 4 still needed someone's help. CONCLUSION: Embolization lowers the blood supply of the spinal cord hemangioblastoma, elevates the cure rate, and enlarges the indication of spinal cord hemangioblastoma operation.

[Treatment of multisegmental intramedullary cervical spinal cord ependymomas].

OBJECTIVE: To discuss the possibility of microneurosurgery techniques in the treatment of multisegmental intramedullary cervical spinal cord ependymomas. METHODS: The clinical data of 26 cases of multisegmental intramedullary cervical spinal cord ependymomas patients was reviewed and analyzed. RESULTS: There were 14 cases of cervical spinal cord ependymomas, 12 cases of cervical and thoracic spinal cord ependymomas. 4.5 spinal cord segments were involved in average. Incompletely inferior paraplegia was in 18 cases, incompletely high paraplegia in 8 cases, dyspnea in 6 cases, sphincter dysfunction in 10 cases. MRI detected syringomyelia formation in 24 cases. Vertebral lamina reposition were done in 20 cases. Muscle strength recovered in 21 cases, no change in 4 cases, aggravated in 1 case. All cases had total resection and 1 cases vertebral had instability in MRI. CONCLUSIONS: Total resection of intramedullary cervical spinal cord ependymomas can be achieved by microneurosurgery. Most of the symptoms can be released after microsurgical treatment. After multisegmental laminotomy, the vertebral plate reposition should be done to ensure the stability.

[Minimally invasive surgery of the spinal cord hemangioblastoma].

OBJECTIVE: To clarify and discuss the diagnosis and minimally invasive surgery of spinal cord hemangioblastoma. METHODS: The clinical data of 16 patients with spinal cord hemangioblastoma who were operated on between 1992 and 2001 were analyzed retrospectively with a review of the literature. RESULTS: Twelve patients were subjected to MRI examination, nine to spinal cord angiography, and six to preoperative embolization. Thirteen patients underwent complete excision, and three underwent partial excision due to massive bleeding and anterior location of the tumor in spinal cord. Eleven patients showed improvement of their symptoms, four no change at all, and tumor recurrence was seen in one patient with aggravation. CONCLUSION: MRI and spinal angiography are essential for preoperative diagnosis and surgical planning. Early diagnosis and microsurgical resection greatly preserve the neurological function of the patients. Preoperative embolization sometimes is helpful in surgery.

A comparative immunohistochemistry of O6-methylguanine-DNA methyltransferase and p53 in diffusely infiltrating astrocytomas.

The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) removes mutagenic adducts from the O6 position of guanine, thereby protecting the genome against guanine : cytosine to adenine : thymine transition and, meanwhile, conferring tumor resistance to many anti-cancer alkylating agents commonly used in the treatment of malignant gliomas. Studies on the involvement of p53 protein in expression of the MGMT gene have provided conflicting results regarding the relation between p53 protein and MGMT gene expression. To examine the potential immunostaining pattern of MGMT expression and to evaluate the possible relationship between p53 and MGMT regulation, we assessed MGMT and p53 accumulation on 35 cases of diffusely infiltrating astrocytomas. With a few cases showing cytoplasmic staining, MGMT accumulation was mainly nuclear. The percentage of labeled tumor cells was lower in high-grade astrocytomas than in low-grade astrocytomas (P < 0.05). Additionally, p53-immunopositive tumor cells were usually immunonegative to MGMT. Thus, it is suggested that MGMT expression is reduced during malignant transformation of diffusely infiltrating astrocytomas, and that mutant p53 protein might be associated with down regulation of the MGMT expression.

[Microsurgical management of tethered cord syndrome].

OBJECTIVE: To assess the results of 26 patients with tethered cord syndrome (TCS) after microsurgical operation. METHODS: Twenty-six patients with TCS were treated microsurgically and their clinical data were analyzed retrospectively. RESULTS: 72% of the patients with TCS showed significant improvement. Surgical outcome was excellent in relieving pain and sensorimotor deficits, but bladder dysfunction. CONCLUSION: Early diagnosis and adequate surgical release are the keys to a successful outcome.