Publications by authors named "Sergei Terterov"

16 Publications

  • Page 1 of 1

Simultaneous cerebrospinal fluid and hematologic metastases in a high-grade ependymoma.

Surg Neurol Int 2018 26;9:93. Epub 2018 Apr 26.

Department of Neurosurgery, University of California, David Geffen School of Medicine, California, USA.

Background: Ependymomas are relatively uncommon tumors that constitute about 7% of all primary intracranial neoplasms. Among these, high-grade ependymomas are locally aggressive and recur most commonly at the primary site following resection. Ependymomas are also known to be the one glial neoplasm that tends to frequently metastasize inside and outside the central nervous system (CNS) that complicates workup and management. Metastasis due to surgical manipulation is common and neurosurgeons should be well-versed in the most effective methods to remove these tumors in order to avoid such metastases.

Case Description: Here, we report a case of a 28-year-old female who initially presented with a parenchymal World Health Organization (WHO) grade III anaplastic ependymoma of the occipital lobe without metastasis. After multiple resections, the patient showed no evidence of disease recurrence for 2 years. During follow-up, new metastasis to the frontal lobe as well as to the lung were discovered 2 years after the initial surgery, without recurrence at the tumor's primary site.

Conclusions: While uncommon, this case demonstrates the possibility for ependymomas to metastasize via cerebrospinal fluid to other locations within the CNS and hematologically to extraneural locations without recurring locally.
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http://dx.doi.org/10.4103/sni.sni_475_17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5938895PMC
April 2018

Surgical nuances of partial sacrectomy for chordoma.

Surg Neurol Int 2017 20;8:277. Epub 2017 Nov 20.

Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, USA.

Background: Sacral chordomas are rare, slow growing, locally aggressive tumors. Unfortunately, aggressive surgical resection is often associated with increased neurological morbidity.

Methods: This technical note focuses on the utilization of partial sacrectomy for the resection of complex spinal chordomas.

Results: The case presented documents the potential range of postoperative morbidity seen in patients undergoing partial sacrectomy for chordomas. Despite iatrogenic morbidity and tumor recurrence, with the cooperation of medical and surgical spine specialists, majority of patients can achieve good long-term outcomes.

Conclusions: Sacral chordomas are rare lesions and pose a therapeutic challenge for spinal surgeons and oncologists. surgical resection (e.g., partial sacrectomy) is the treatment of choice for these lesions, and the cooperation between subspecialists can lead to good neurologic outcomes, particularly if gross total resection is achieved.
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http://dx.doi.org/10.4103/sni.sni_230_17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5705930PMC
November 2017

Adult sacrococcygeal teratoma with coccygectomy: A case report with a review of the literature.

Surg Neurol Int 2017 24;8:260. Epub 2017 Oct 24.

Department of Neurosurgery, Kaiser Permanente Medical Center, Los Angeles, California, USA.

Background: Saccrococcygeal teratomas (SCT) are derived from embryonic germ cell layers. They frequently present at the base of the coccyx within the pelvis. While these tumors are common in children, they are exceedingly rare in adults. In adults, a majority of these tumors are intrapelvic and associated with a low risk of malignant transformation. Therefore, this contributes to a good prognosis following resection of mostly benign lesions.

Case Description: An adult female with chronic pelvic pain presented with a sacral teratoma. She failed conservative treatment and underwent a coccygectomy with an excision of the tumor. Microscopic histological analysis showed no evidence of immature or malignant elements, confirming the diagnosis of a mature, benign, cystic SCT.

Conclusions: Mature SCTs in adults are rare malignant lesions. In this case, the patient was cured following primary surgical excision requiring en-bloc coccygectomy.
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http://dx.doi.org/10.4103/sni.sni_224_17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5680643PMC
October 2017

Surgical nuances of circumferential lumbar spondylectomy: A case report and short literature review.

Surg Neurol Int 2017 24;8:253. Epub 2017 Oct 24.

Department of Neurosurgery, Kaiser Permanente Medical Center, Los Angeles, California, USA.

Background: Chordomas are uncommon malignant bone tumors that are often minimally symptomatic for several years. By the time they are diagnosed, these lesions are typically large, involve major neural, bony, and vascular structures, and are no longer readily resectable. This leads to a high recurrence rate.

Case Description: In this case report, we present a 67-year-old male with nonmechanical axial back pain, neurogenic claudication, and a large mass centered at the L3 level on magnetic resonance imaging consistent with a locally invasive chordoma. The patient underwent surgical resection that required a complete lumbar spondylectomy utilizing a three-stage approach, leading to incomplete tumor excision. The patient's residual postoperative symptoms included paresthesias/numbness in the right anterior thigh and a partial (4/5) right-sided foot drop. At the time of discharge, there were plans for future proton beam therapy.

Conclusions: Because of their relative resistance to chemotherapeutic agents, the optimal surgical management of chordomas is gross total excision. Unfortunately, this is rarely feasible.
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http://dx.doi.org/10.4103/sni.sni_225_17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5680665PMC
October 2017

Adjuvant Stereotactic Radiosurgery and Radiation Therapy for the Treatment of Intracranial Chordomas.

J Neurol Surg B Skull Base 2016 Feb 3;77(1):38-46. Epub 2015 Aug 3.

Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States; Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California, United States.

Objective Chordomas are locally aggressive, highly recurrent tumors requiring adjuvant radiotherapy following resection for successful management. We retrospectively reviewed patients treated for intracranial chordomas with adjuvant stereotactic radiosurgery (SRS) and stereotactic radiation therapy (SRT). Methods A total of 57 patients underwent 83 treatments at the UCLA Medical Center between February 1990 and August 2011. Mean follow-up was 57.8 months. Mean tumor diameter was 3.36 cm. Overall, 8 and 34 patients received adjuvant SRS and SRT, and the mean maximal dose of radiation therapy was 1783.3 cGy and 6339 cGy, respectively. Results Overall rate of recurrence was 51.8%, and 1- and 5-year progression-free survival (PFS) was 88.2% and 35.2%, respectively. Gross total resection was achieved in 30.9% of patients. Adjuvant radiotherapy improved outcomes following subtotal resection (5-year PFS 62.5% versus 20.1%; p = 0.036). SRS and SRT produced comparable rates of tumor control (p = 0.28). Higher dose SRT (> 6,000 cGy) (p = 0.013) and younger age (< 45 years) (p = 0.03) was associated with improved rates of tumor control. Conclusion Adjuvant radiotherapy is critical following subtotal resection of intracranial chordomas. Adjuvant SRT and SRS were safe and improved PFS following subtotal resection. Higher total doses of SRT and younger patient age were associated with improved rates of tumor control.
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http://dx.doi.org/10.1055/s-0035-1554907DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4777625PMC
February 2016

Angiographically occult vascular malformation of the intracranial accessory nerve: case report.

J Neurosurg 2016 07 13;125(1):167-72. Epub 2015 Nov 13.

Departments of 1 Neurosurgery and.

Angiographically occult cerebral vascular malformations (AOVMs) are usually found in the supratentorial brain parenchyma. Uncommonly, AOVMs can be found within the cavernous sinus or basal cisterns and can be associated with cranial nerves. AOVMs involving the intracranial segment of the spinal accessory nerve have not been described. A 46-year-old female patient presented with a history of episodic frontal headaches and episodes of nausea and dizziness, as well as gait instability progressing over 6 months prior to evaluation. Imaging revealed a well-circumscribed 3-cm extraaxial T1-weighted isointense and T2-weighted hyperintense contrast-enhancing mass centered in the region of the right lateral cerebellomedullary cistern. The patient underwent resection of the lesion. Although the intraoperative appearance was suggestive of a cavernous malformation, some histological findings were atypical, leading to the final diagnosis of vascular malformation, not otherwise specified. The patient's postoperative course was uneventful with complete resolution of symptoms. To the authors' knowledge, this is the first report of an AOVM involving the intracranial portion of the accessory nerve. For any AOVM located within the cerebellomedullary cistern or one suspected of involving a cranial nerve, the authors recommend including immunohistochemistry with primary antibody to neurofilament in the histopathology workup.
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http://dx.doi.org/10.3171/2015.6.JNS131105DOI Listing
July 2016

Predictors of recurrence following resection of intracranial chordomas.

J Clin Neurosci 2015 Nov 22;22(11):1792-6. Epub 2015 Jul 22.

Department of Neurosurgery, University of California, 300 Stein Plaza, Suite 562, Fifth Floor, Wasserman Building, Los Angeles, CA 90095-6901, USA; Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA, USA. Electronic address:

Management of intracranial chordomas remains challenging, despite improvements in microsurgical techniques and radiotherapy. Here, we analyzed the prognostic factors associated with improved rates of tumor control in patients with intracranial chordomas, who received either gross (GTR) or subtotal resections (STR). A retrospective review was performed to identify all patients who were undergoing resection of their intracranial chordomas at the Ronald Reagan University of California Los Angeles Medical Center from 1990 to 2011. In total, 57 patients undergoing 81 resections were included. There were 24 females and 33 males with a mean age of 44.6 years, and the mean tumor diameter was 3.36 cm. The extent of resection was not associated with recurrence. For all 81 operations, the 1 and 5 year progression free survival (PFS) was 87.5 and 40.4%, and 88.0 and 33.6% for STR and GTR, respectively (p=0.90). Adjuvant radiotherapy was associated with improved rates of PFS (hazard ratio [HR] 0.20; p=0.009). Additionally, age >45 years (HR 5.88; p=0.01) and the presence of visual deficits (HR 7.59; p=0.03) were associated with worse rates of tumor control. Tumor size, sex, tumor histology, and recurrent tumors were not predictors of recurrence. Younger age, lack of visual symptoms on presentation and adjuvant radiotherapy were associated with improved rates of tumor control following surgery. However, GTR and STR produced comparable rates of tumor control. The surgical management of intracranial chordomas should take a conservative approach, with the aim of maximal but safe cytoreductive resection with adjuvant radiation therapy, and a major focus on quality of life.
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http://dx.doi.org/10.1016/j.jocn.2015.05.024DOI Listing
November 2015

Postcraniotomy superficial temporal artery pseudoaneurysm in the setting of triple H therapy: A case report and literature review.

Surg Neurol Int 2012 27;3:139. Epub 2012 Nov 27.

Department of Neurosurgery, David Geffen School of Medicine at UCLA, 757 Westwood Plaza, Suite 6236, Los Angeles, CA, USA.

Background: Superficial temporal artery (STA) pseudoaneurysm after a craniotomy is very rare with only five cases reported in the literature, none manifesting in the setting of cerebral vasospasm treatment with triple H therapy.

Case Description: A 31-year-old male was admitted after a syncopal episode. Imaging documented a ruptured anterior communicating artery aneurysm. He was taken to the operating room for aneurysm clipping, but the procedure was aborted due to intraoperative aneurysm re-rupture, at which point the patient underwent emergent coil embolization of the aneurysm. The postoperative course was complicated by severe cerebral vasospasm requiring prolonged triple H therapy. On postoperative day 22, a growing left temporal mass with a bruit was noted. The suspected diagnosis of STA pseudoaneurysm was confirmed by femoral angiography, and it was treated with coils and Onyx embolization.

Conclusion: We report the first case of a postcraniotomy STA pseudoaneurysm in the setting of induced hypertension for the treatment of cerebral vasospasm. Endovascular embolization is a viable option for the treatment of an STA pseudoaneurysm.
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http://dx.doi.org/10.4103/2152-7806.103877DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3515923PMC
December 2012

Intramedullary abscess of the spinal cord in the setting of patent foramen ovale.

World Neurosurg 2011 Sep-Oct;76(3-4):361.e11-4

Department of Neurological Surgery, University of Southern California, Keck School of Medicine, Los Angeles, California, USA.

Background: Intramedullary abscess of the spinal cord is a rare entity, especially in the setting of an intracardiac shunt, which, to our knowledge, has not been described in the literature. Here we present a case of an intramedullary spinal cord abscess in a patient with a patent foramen ovale.

Methods: The article includes a chart review and description of a clinical case presentation.

Results: A 59-year-old man was admitted with rapidly progressive quadriparesis. Magnetic resonance imaging of the cervical spine demonstrated a large intramedullary mass extending from the level of C3 to C7. The patient was taken to the operating room for biopsy and surgical evacuation of the mass. Intraoperative pathology was consistent with abscess, and subsequent cultures grew Streptococcus viridans. On further workup, the patient was found to have a patent foramen ovale with right-to-left flow. Postoperatively, the strength improved significantly in all extremities with residual weakness.

Conclusion: This is the first published case of an intramedullary spinal cord abscess in the setting of an intracardiac right-to-left shunt. Although intramedullary spinal cord abscess is rare, there are certain predisposing conditions that increase the risk of its occurrence.
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http://dx.doi.org/10.1016/j.wneu.2010.01.008DOI Listing
November 2011

Symptomatic vertebral artery compression by the rod of a C1-C2 posterior fusion construct: case report and review of the literature.

Spine (Phila Pa 1976) 2011 May;36(10):E678-81

Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.

Study Design: Case report.

Objective: To report a rare complication of atlantoaxial fusion.

Summary Of Background Data: Vertebral artery injury is a serious complication of screw-based atlantoaxial fusion. To our knowledge, injury to the vertebral artery has only been described as a result of screw placement. We describe the first case of atlantoaxial fixation complicated by symptomatic and reversible external compression of the vertebral artery by the rod in a Harms construct.

Methods: Medical records and imaging reports were reviewed.

Results: A neurologically intact 84-year-old woman presented after a ground-level fall. Imaging revealed a nondisplaced type II odontoid fracture associated with a C1 ring fracture. She underwent a minimally invasive Harms atlantoaxial fusion. After surgery, she developed fluctuating level of consciousness in the setting of an otherwise normal neurologic and metabolic workup. A computed tomographic angiogram was obtained and showed good screw placement except for compression of the right vertebral artery from the right transfixing rod causing 75% luminal narrowing. She underwent a revision with rod shortening, and after surgery, improved neurologically, without any further episodes of altered mental status.

Conclusion: In atlantoaxial fusion, the incidence of vertebral artery compression by the rod component of fusion construct may be underreported because it is difficult to detect with noncontrast computed tomography without computed tomographic angiography, which is not routinely obtained unless there is a high suspicion for vascular injury. We recommend inserting the rods with the cut (sharp) end pointing inferiorly, to avoid lacerating the vertebral artery. A vertebral artery compression from the rod in the absence of screw violation of the foramen transversarium should be considered in a patient with altered mental status after atlantoaxial fusion.
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http://dx.doi.org/10.1097/BRS.0b013e3181faa6deDOI Listing
May 2011

Posttraumatic human cerebral myiasis.

World Neurosurg 2010 May;73(5):557-9

Department of Neurosurgery, Keck School of Medicine, University of Southern California Los Angeles, California, USA.

Objective: Only eight cases of cerebral myiasis in humans have been reported worldwide and only one in the United States. Presented here is a case of cerebral myiasis in the setting of head trauma in suburban Los Angeles.

Methods: The article includes chart review and description of a clinical case presentation.

Results: A 42-year-old HIV-positive man was found in a ditch after 2 weeks, the victim of apparent assault. He had multiple facial fractures along with open depressed bifrontal sinus fractures with necrotic bone, eroded dura, exposed cortex, and extensive maggot infestation of the left frontal lobe. The patient was taken urgently to the operating room, where the maggots where evacuated by irrigation and suction. Debridement of necrotic bone, dura, and brain was performed, the frontal sinuses were exenterated, and skull defects plated with titanium mesh. Intraoperative cultures revealed a polymicrobial meningitis/encephalitis, which was treated postoperatively with antibiotics. The patient's neurologic exam stabilized and the patient was transferred to a rehabilitation facility for further care, ultimately achieving functionality and holding a job.

Conclusion: This is the first published case of cerebral myiasis secondary to trauma, and to our knowledge, the first documented long-term survivor of extensive cerebral myiasis. Wide debridement to normal brain followed by 6 weeks of broad-spectrum antibiotic treatment is effective in managing this condition. A well-functioning outcome can be expected with prompt recognition and treatment of the disease. Larval infestation may have a protective effect against bacterial infection and may allow for greater tolerance of treatment delay.
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http://dx.doi.org/10.1016/j.wneu.2010.01.004DOI Listing
May 2010

Evaluation of intracranial cerebrospinal fluid cytology in staging pediatric medulloblastomas, supratentorial primitive neuroectodermal tumors, and ependymomas.

J Neurosurg Pediatr 2010 Aug;6(2):131-6

Division of Neurosurgery, Childrens Hospital Los Angeles, Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.

Object: The objective of this study was to determine the role of intracranial CSF examination in detecting true cases of early tumor dissemination. Cerebrospinal fluid dissemination is an ominous feature of pediatric brain tumors, occurring in as many as 30% of medulloblastomas, 25% of supratentorial primitive neuroectodermal tumors (PNETs), and 5% of ependymomas at diagnosis. Detecting early dissemination is important for determining both treatment and prognosis. Dissemination can be detected by evaluating imaging of the full neuraxis and by examining CSF cytology. Neuraxis MR imaging and lumbar CSF cytology evaluation are widely accepted methods for determining dissemination. However, the value of examining intracranial CSF cytology in detecting early dissemination is uncertain.

Methods: Under an institutional review board-approved protocol, medical records, pathology reports, and radiology reports for 150 patients who had undergone resection of brain tumors (88 with medulloblastomas, 21 with supratentorial PNETs, and 41 with ependymomas) and who had been evaluated using neuraxis MR imaging studies in the last 15 years were retrospectively reviewed. Radiology results were compared with the CSF cytology results and long-term disease outcomes.

Results: Between lumbar and intracranial CSF cytology results, 7 of 40 were discordant: in 2 intracranial CSF was negative and lumbar CSF was positive, and in 5 the reverse was true. The discordance percentage was 18%, with a kappa statistic of 0.36. Between MR imaging and lumbar CSF cytology results, 11 of 65 were discordant: in 9 the lumbar CSF was negative and MR imaging was positive, and in 2 the reverse was true. The discordance percentage is 17%, with a kappa statistic of 0.27. Between MR imaging and intracranial CSF cytology results, 8 of 52 were discordant: in 3 intracranial CSF was negative and MR imaging was positive, and in 5 the reverse was true. The discordance rate was 15%, with a kappa statistic of 0.41. Patients with positive and negative results on perioperative neuraxis MR imaging studies had a median survival of 26.8 and 33.1 months, respectively (p = 0.02). Patients with positive and negative results on perioperative lumbar CSF cytology had a median survival of 20.1 and 31.4 months, respectively (p = 0.11). Patients with positive and negative results on intracranial CSF cytology had a median survival of 31 and 31.4 months, respectively (p = 0.84).

Conclusions: Discordance exists between the results of neuraxis MR imaging and lumbar and intracranial CSF cytology in perioperative detection of tumor dissemination for pediatric medulloblastoma, supratentorial PNETs, and ependymoma. In 1 case in this series, perioperative dissemination was detected by intracranial CSF cytology, but not by lumbar CSF cytology or neuraxis MR imaging. Isolated intracranial CSF cytology positivity may represent an earlier stage of disseminated disease. Complementary use of perioperative neuraxis MR imaging and lumbar and intracranial CSF cytology can reduce the incidence of missed diagnoses of dissemination. Survival analysis revealed that perioperative neuraxis MR imaging findings are correlated with survival, whereas perioperative lumbar and intracranial CSF cytology findings are not.
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http://dx.doi.org/10.3171/2010.5.PEDS09333DOI Listing
August 2010

Cerebral vasospasm and concurrent left ventricular outflow tract obstruction: requirement for modification of hyperdynamic therapy regimen.

Neurocrit Care 2010 Apr;12(2):265-8

Department of Neurosurgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.

Background: Medical treatment of arterial vasospasm following aneurysmal subarachnoid hemorrhage (SAH) generally consists of triple H therapy, which frequently relies on inotropic agents in order to increase cardiac output (CO). Patients with concurrent left ventricular outflow tract (LVOT) obstruction may have paradoxical decreases in CO following administration of inotropic pressors, placing them at significant risk for cerebral ischemia and stroke.

Methods: The clinical courses of two patients with SAH-induced arterial vasospasm and underlying left ventricular outflow obstruction are reported. Both patients had hypotension and low cardiac output that were refractory to medical management with triple H therapy. Echocardiography in both patients demonstrated LVOT obstruction secondary to hypertrophic obstructive cardiomyopathy (HOCM).

Results: Intervention in both patients included discontinuation of inotropic agents and maintenance of hypervolemia to a target pulmonary capillary wedge pressure range, resulting in improved cardiac output and mean arterial pressure.

Conclusion: Medical treatment for cerebral vasospasm with inotropic pressor agents may result in paradoxical decreases in hemodynamic parameters and cerebral perfusion in patients with LVOT obstruction. While HOCM is the most likely structural abnormality to cause this phenomenon, it can be induced by several physiological conditions encountered in the neurocritical care setting. Modifications in triple H therapy regimens may be required in order to optimize cerebral perfusion and prevent cerebral ischemia and stroke in these patients.
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http://dx.doi.org/10.1007/s12028-009-9286-9DOI Listing
April 2010

Survival in lymph node negative adenocarcinoma of the esophagus after R0 resection with and without neoadjuvant therapy: evidence for downstaging of N status.

J Am Coll Surg 2009 Apr;208(4):553-6

Department of Surgery, University of Southern California, Los Angeles, CA, USA.

Background: After esophagectomy, many patients who received neoadjuvant therapy have no evidence of lymph node involvement (N0 disease). Whether lymph nodes were initially involved and eradicated by the neoadjuvant therapy (down-staged) or if the nodes were never involved is a subject of debate. To address this issue, we compared clinical outcomes in N0 patients treated with neoadjuvant therapy with outcomes in patients treated with surgery alone.

Study Design: We reviewed records of 100 consecutive patients who underwent R0 esophagectomy for adenocarcinoma with pathologic N0 status. Seventy-five patients were treated by operation alone and 25 received neoadjuvant therapy. Tumor characteristics including length, depth, lymphovascular invasion, and degree of differentiation were compared and longterm survival was assessed by Kaplan-Meier analysis at a median of 46 months (interquartile range 26 to 77 months).

Results: Tumor characteristics were similar between groups. Recurrence was more common in patients who received neoadjuvant therapy compared with those treated with surgery alone (10 of 25 versus 10 of 75, p=0.0063). Patients with N0 disease after neoadjuvant therapy had a significantly worse survival than patients treated by surgery alone (49% versus 85%, p=0.005).

Conclusions: Although neoadjuvant therapy may eradicate lymph node metastases, it does not result in the same outcomes as those achieved in patients with N0 disease treated with surgery alone. The poor clinical outcomes observed in N0 patients after neoadjuvant therapy suggest that they initially had node involvement and were downstaged by eradication of lymph node disease.
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http://dx.doi.org/10.1016/j.jamcollsurg.2009.01.017DOI Listing
April 2009

Conformational analyses of 2,3-dihydroxypropanoic acid as a function of solvent and ionization state as determined by NMR spectroscopy.

Magn Reson Chem 2006 Mar;44(3):210-9

Gates and Crellin Laboratories of Chemistry, California Institute of Technology, Pasadena, California 91125, USA.

Vicinal (1)H--(1)H coupling constants were used to determine the conformational preferences of 2,3-dihydroxypropanoic acid (1) (DL-glyceric acid) in various solvents and its different carboxyl ionization states. The stereospecific assignments of J(12) and J(13) were confirmed through the point-group substitution of the C-3 hydrogen with deuterium, yielding rac-(2SR,3RS)-[3-(2)H]-1, and the observation of only J(13) in the (1)H NMR spectra. While hydrogen bonding and steric strain may be expected to drive the conformational equilibrium, their role is overshadowed by a profound gauche effect between the vicinal hydroxyl groups that mimics other substituted ethanes, such as 1,2-ethanediol and 1,2-difluoroethane. At low pH, the conformational equilibrium is heavily weighted toward the gauche-hydroxyl rotamers with a range of 81% in DMSO-d(6) to 92% in tert-butyl alcohol-d(10). At high pH, the equilibrium exhibits a larger dependence upon the polarity and solvating capability of the medium, although the gauche effect still dominates in D(2)O, 1,4-dioxane-d(8), methanol-d(4), and ethanol-d(6) (96, 89, 85, and 83% gauche-hydroxyls respectively). The observed preference for the gauche-hydroxyl rotamers is believed to stem primarily from hyperconjugative sigma(C--H) --> sigma*(C--OH) interactions.
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http://dx.doi.org/10.1002/mrc.1758DOI Listing
March 2006