WILLIAM OMAR CONTRERAS LOPEZ

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  • article 5 Citação(ões) na Scopus
    Effects of sexed semen and interactive effects on commercial in vitro embryo production when oocytes are collected from cows of Bos indicus, and Bos taurus breeding and crossbred cows of these subspecies
    (2015) LOPEZ, William Omar Contreras; ALVIS-MIRANDA, Hernando Raphael; GAMARRA, Andres Felipe; RENDON, Bibiana; BORDA, Diego Armando Vega; ALBICKER, Ulrich; FONOFF, Erich Talamoni; MARTINEZ-DIAZ, Mario
    A large scale commercial in vitro embryo production and in vitro fertilization record is reported when there was use of oocytes from Bos taurus (BT), Bos indicus (BI), and Bos Taurus/indicus (BT/BI) crossbred subspecies fertilized with sexed (SS) and conventional (CS) semen. The aim of the study was to analyze the impacts of use SS in a commercial embryo production center in Colombia. Non-pregnant (n = 800), healthy, and estrous cycling BT, BI, and BI/BT crossbred cows were selected to be used as oocyte donors. Viable oocytes from 733 ovum pick up sessions in cows of the BT (4663) and BI (7305), BT/BI (3605) groups were matured and fertilized with frozen thawed semen from commercial sires. Of all cultured oocytes (n = 15,573), 52.3% of the embryos (n = 8607) underwent cleavage while 3062(19.7%) developed to the blastocyst stage. For cows of the BT, SS and CS groups, there were similar cleavage rates; however, use of SS decreased blastocyst formation (15.6% versus 18.9%). In the BI group, use of SS increased cleavage rates (59.1% versus 53%, respectively) although there was no effect on blastocyst rate development (22.9% versus 21.9). In the BI/BT groups, use of SS decreased cleavage (44.4% versus 57.1%, respectively) and blastocyst rate development compared with the CS group (15.3% versus 20.1%, respectively). Data from this study indicate embryos from cows of the BT purebred or BI/BT crossbred had less in vitro developmental capacity compared to embryos derived from oocytes of cows that were purebred BI in tropical-subtropical regions.
  • article 15 Citação(ões) na Scopus
    Neurosurgical treatment for dystonia: Long-term outcome in a case series of 80 patients
    (2014) MARTINEZ, Jairo Alberto Espinoza; PINSKER, Marcus O.; ARANGO, Gabriel J.; GARCIA, Xiomara; V, Oscar Andres Escobar; FURLANETTI, Luciano; REITHMEIER, Thomas; ARANDA, Inigo Alonso Aguirre; MARIN, Jorge Humberto; LOPEZ, William Omar Contreras
    Introduction: In this study, we assessed the outcomes of patients with dystonia who underwent surgery treatment following the same algorithm. Patients and methods: Eighty consecutive patients with dystonia were submitted to neurosurgical management by means of intrathecal pump implantation, pallidotomy or deep brain stimulation (GPi or VIM). These patients included 48 patients with primary dystonia and 32 patients with secondary dystonia. Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) was used to access pre- and postoperative outcomes. Patients were followed from 12 to 114 months. Results: Mean improvement in BFMDRS score among patients with PrD was 87.54% and 42.21% for SeD. Hemidystonic patients in both groups (PrD, SeD) showed a mean improvement in BFMDRS of 71.05% with GPiDBS. Patients with SeD due to previous perinatal insults showed a mean improvement in BFMDRS of 41.9%, with better results in purely dyskinetic patients (mean improvement of 61.2%). Conclusion: Use of the proposed algorithm facilitated surgical decision planning, which translated in improved diagnostic rates, earlier interventions, appropriate management plans, and outcomes for both groups (PrD, SeD). Therefore, neuroimaging findings had a positive prognostic significance in the response to treatment in patients with primary dystonia compared with patients with secondary dystonia or distortion of basal ganglia anatomy. However, further studies in this line are warranted.
  • article 17 Citação(ões) na Scopus
    Frame-based stereotactic neurosurgery in children under the age of seven: Freiburg University's experience from 99 consecutive cases
    (2015) FURLANETTI, Luciano L.; MONACO, Bernardo A.; CORDEIRO, Joacir G.; LOPEZ, William Omar Contreras; TRIPPEL, Michael
    Introduction: Stereotactic frame-based procedures proved to be precise, safe and are of widespread use among adult patients. Regarding pediatric patients few data is available, therefore the use of the stereotactic frame remains controversial in this population. This motivated us to report our experience in stereotactic procedures in the youngest patients and review the literature concerning this subject. Methods: All frame-based procedures performed in patients younger than seven years in the University of Freiburg during the last 10 years were retrospectively analyzed and discussed under the light of the current literature. Results: The studied population was composed of 72 patients under the age of seven (mean 3.4 +/- 2.1 years-old), in whom 99 stereotactic procedures were performed. Brain tumor was present in 60 patients, hydrocephalus in five, cystic lesions in three, intracranial abscess in three and epilepsy in one patient. Stereotactic surgery was performed in 36 cases for brachytherapy, in 29 for biopsy, in 20 cases for cyst puncture, in eight for stereotactically guided endoscopic ventriculostomy, in five for catheter placement and in one case for depth electrode insertion. The overall complication rate was 5%. There were three cases of pin penetration through the skull, one case of frame dislocation after extensive cyst drainage and two skull fractures. Neurologic deficit related to frame fixation was observed in none of the cases. In disagreement with other authors, no case of pin related infection, air embolism, hematoma or CSF leak was observed. Conclusion: Frame-based stereotactic neurosurgery is a safe technique also in the youngest patients. Rather than the simple use of torque-limiting devices training and experience in the manual adjustment of the stereotactic frame in children have been proven to be crucial factors that contribute to reducing pin related complications.
  • article 7 Citação(ões) na Scopus
    Microendoscopy-guided percutaneous cordotomy for intractable pain: case series of 24 patients
    (2016) FONOFF, Erich Talamoni; LOPEZ, William Omar Contreras; OLIVEIRA, Ywzhe Sifuentes Almeida de; TEIXEIRA, Manoel Jacobsen
    OBJECTIVE The aim of this study was to show that microendoscopic guidance using a double-channel technique could be safely applied during percutaneous cordotomy and provides clear real-time visualization of the spinal cord and surrounding structures during the entire procedure. METHODS Twenty-four adult patients with intractable cancer pain were treated by microendoscopic-guided percutaneous radiofrequency (RF) cordotomy using the double -channel technique under local anesthesia. A percutaneous lateral puncture was performed initially under fluoroscopy guidance to localize the target. When the subarachnoid space was reached by the guiding cannula, the endoscope was inserted for visualization of the spinal cord and surrounding structures. After target visualization, a second needle was inserted to guide the RF electrode. Cordotomy was performed by a standard RF method. RESULTS The microendoscopic double -channel approach provided real-time visualization of the target in 91% of the cases. The other 9% of procedures were performed by the single -channel technique. Significant analgesia was achieved in over 90% of the cases. Two patients had transient ataxia that lasted for a few weeks until total recovery. CONCLUSIONS The use of percutaneous microendoscopic cordotomy with the double-channel technique is useful for specific manipulations of the spinal cord. It provides real-time visualization of the RF probe, thereby adding a degree of safety to the procedure.
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    Characteristic activity pattern obtained by MER to demarcate the borders between the caudal zona incerta and STN for stereotactic treatment of post-traumatic tremor
    (2014) FONOFF, E. T.; LOPEZ, W. O. Contreras; REIS, P. R.; NEVILLE, I.; NAVARRO, J.; JACOBSEN, M. T.
  • article 2 Citação(ões) na Scopus
    Aesthetically optimal deep brain stimulation technique in patients with alopecia
    (2015) FONOFF, Erich Talamoni; TEIXEIRA, Manoel Jacobsen; NASCIMENTO, Clarissa Nobrega Gambarra; LOPEZ, William Omar
  • article 0 Citação(ões) na Scopus
    A ying and yang brain
    (2015) LOPEZ, W. O.; PATERNINA, J. J. G.; TIERNEY, T.
  • article 11 Citação(ões) na Scopus
    Clinical neurotransplantation protocol for Huntington's and Parkinson's disease
    (2013) LOPEZ, William Omar Contreras; NIKKHAH, Guido; KAHLERT, Ulf D.; MACIACZYK, Donata; BOGIEL, Tomasz; MOELLERS, Sven; SCHUELTKE, Elisabeth; DOEBROESSY, Mate; MACIACZYK, Jaroslaw
    Purpose: The concept of transplantation of neuronal cells to treat Huntington's and Parkinson's diseases is based on the proven principle that dopaminergic and GABA-ergic progenitor neurons (from the human developing ventral mesencephalon and whole ganglionic eminence) can survive, differentiate and functionally integrate into an allogenic host brain. However, several donor and host-specific variables play a major role in the safety and outcome of this procedure. In this paper, we seek to summarize an updated neural transplantation protocol, based on our institutional experience and many years of collaboration with other neurotransplantation centers. Methods: We present a detailed clinical neurotransplantation protocol for Parkinson's (PD) and Huntington's (HD) diseases with special emphasis in understanding the anatomical relationships of the human fetal tissue that are relevant for selection of the desired cell populations. Results: Two detailed step-wise neurotransplantation protocols are presented, outlining strategies facilitating the avoidance of possible procedure-related complications. Conclusions: In this paper we delineated some crucial technical factors enabling the execution of a safe and effective neural transplantation. The protocols presented here might contribute to further development of the experimental clinical neurotransplantation towards a routine therapeutic procedure.
  • article 6 Citação(ões) na Scopus
    Hypertrophic Olivary Degeneration: A Neurosurgical Point of View
    (2016) CARVALHO, Carlos Henrique; KIMMIG, Hubert; LOPEZ, William Omar Contreras; LANGE, Manfred; OECKLER, Reinhard
    Hypertrophic olivary degeneration (HOD) is a rare form of transsynaptic degeneration characterized by hypertrophy of the inferior olivary nucleus situated in the olivary body, part of the medulla oblongata, representing a major source of input to the cerebellum. HOD typically results from focal lesions interrupting connections from the inferior olive within the dentato-rubro-olivary pathway, a region also known as the triangle of Guillain-Mollaret (TGM) (red nucleus, inferior olivary nucleus, and contralateral dentate nucleus). Clinically, HOD presents classically as palatal tremor and can include dentatorubral tremor and/or ocular myoclonus. The pathologic changes associated with HOD feature radiologic changes with the inferior olivary nucleus appearing larger and increasing its T2-weighted signal intensity on magnetic resonance images. HOD is commonly managed with pharmacotherapy but may require surgical intervention in extreme cases. HOD has been found to develop as a consequence of any injury that disrupts the TGM pathways (e.g., pontine cavernoma). These findings highlight the critical importance of a thorough knowledge of TGM anatomy to avoid secondary HOD. We present a patient who developed HOD secondary to resection of a tectal plate cavernous malformation and review the literature with an emphasis on the current knowledge of this disorder.