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BACKGROUND: Although recent guidelines for obstructive sleep apnea recommend early postoperative use of continuous positive airway pressure (CPAP) after endonasal skull base surgery, the time of initiation of CPAP is unclear. In this study we used a novel, previously validated cadaveric model to analyze the pressures delivered to the cranial base and evaluate the effectiveness of various repair techniques to withstand positive pressure. METHODS: Skull base defects were surgically created in 3 fresh human cadaver heads and repaired using 3 commonly used repair techniques: (1) Surgicel™ onlay; (2) dural substitute underlay with dural sealant onlay; and (3) dural substitute underlay with nasoseptal flap onlay with dural sealant. Pressure microsensors were placed in the sphenoid sinus and sella, both proximal and distal to the repair, respectively. The effectiveness of each repair technique against various CPAP pressure settings (5-20 cm H2 O) was analyzed. RESULTS: Approximately 79%-95% of positive pressure administered reached the sphenoid sinus. Sellar pressure levels varied significantly across the 3 repair techniques and were lowest after the third technique. "Breach" points (CPAP settings at which sellar repair was violated) were lowest for the first group. All 3 specimens showed a breach after the first repair technique. For the second repair technique, only a single breach was created in 1 specimen at 20 cm H2 O. No breaches were created in the third group. CONCLUSION: Different skull base repair techniques have varying ability to withstand CPAP. Both second and third repair techniques performed in a nearly similar fashion with regard to their ability to withstand positive pressure ventilation.
Assuntos
Pressão Positiva Contínua nas Vias Aéreas , Procedimentos de Cirurgia Plástica/métodos , Base do Crânio/cirurgia , Apneia Obstrutiva do Sono/cirurgia , Cadáver , HumanosRESUMO
BACKGROUND: Obstructive sleep apnea is a common respiratory disorder that can have negative effects on health and quality of life. Positive pressure therapy (CPAP) is the primary treatment. There is a lack of consensus on the risk of postoperative CPAP after endoscopic sinus or skull base surgery. We present a proof-of-concept cadaver model for measuring sinonasal pressure delivered by CPAP. METHODS: Three fresh cadaver heads were prepared by removing the calvaria and brain. Sphenoidotomies were made and sellar bone was removed. Pressure sensors were placed in the midnasal cavity, sphenoid sinus, and sella. CPAP was applied and the delivered pressure was recorded at increasing levels of positive pressure. Paired t tests and intraclass correlation coefficients were used to analyze results. RESULTS: Increases in positive pressure led to increased pressure recordings for all locations. Nasal cavity pressure was, on average, 81% of delivered CPAP. Pressure was highest in the sphenoid sinus. The effect of middle turbinate medialization on intrasphenoid pressure was not statistically significant in 2 heads. Intrasellar pressure was 80% of delivered CPAP with lateralized turbinates and 84% with medialized turbinates. Pressure recordings demonstrated excellent reliability for all locations. All heads developed non-sellar-based cranial base leaks at higher pressures. Cribriform region leaks were successfully sealed with DuraSeal®. CONCLUSION: Our proof-of-concept cadaver model represents a novel approach to measure pressures delivered to the nasal cavity and anterior skull base by CPAP. With further study, it may have broader clinical application to guide the safe postoperative use of CPAP in this population.
Assuntos
Pressão Positiva Contínua nas Vias Aéreas/métodos , Seios Paranasais/fisiologia , Apneia Obstrutiva do Sono/terapia , Idoso de 80 Anos ou mais , Cadáver , Endoscopia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Anatômicos , Cavidade Nasal/cirurgia , Seios Paranasais/cirurgia , Guias de Prática Clínica como Assunto , Reprodutibilidade dos Testes , RiscoRESUMO
The purpose of this study was to evaluate the effect of posterior septectomy size on surgical exposure and surgical freedom during the endoscopic transsphenoidal approach to the sella and parasellar region. Dissections were performed on 10 embalmed cadaver heads. Dissections started with wide bilateral sphenoidotomies, lateralization of middle turbinates, and a 5-mm posterior septectomy. The posterior septectomy was increased in 5-mm increments to a maximum of 35 mm, followed by bilateral middle turbinectomies. Surgical exposure was defined as the distance between the ipsilateral and contralateral limit of exposure as allowed by the posterior septum along a midsphenoid horizontal meridian. Surgical freedom was defined as the angle between the ipsilateral and contralateral limit. The mean baseline width of the posterior sphenoid sinus was 29.4 ± 3.7 mm. With a 5-mm septectomy, the mean width of surgical exposure was 21.1 ± 2.8 mm. The surgical exposure increased significantly with progressively larger posterior septectomy until a 20-mm posterior septectomy, after which no further increase in surgical exposure or freedom was obtained. Bilateral lateral opticocarotid recesses were accessible with a 15-mm posterior septectomy. The addition of bilateral middle turbinectomies did not significantly increase lateral exposure within the sphenoid sinus compared with middle turbinate lateralization.
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Genomic recombination requires cutting, processing, and rejoining of DNA by endonucleases, polymerases, and ligases, among other factors. We have proposed that DNA recombination mechanisms may contribute to long-term memory (LTM) formation in the brain. Our previous studies with the nucleoside analog 1-beta-D-arabinofuranosylcytosine triphosphate (ara-CTP), a known inhibitor of DNA ligases and polymerases, showed that this agent blocked consolidation of conditioned taste aversion without interfering with short-term memory (STM). However, because polymerases and ligases are also essential for DNA replication, it remained unclear whether the effects of this drug on consolidation were attributable to interference with DNA recombination or neurogenesis. Here we show, using C57BL/6 mice, that ara-CTP specifically blocks consolidation but not STM of context fear conditioning, a task previously shown not to require neurogenesis. The effects of a single systemic dose of cytosine arabinoside (ara-C) on LTM were evident as early as 6 h after training. In addition, although ara-C impaired LTM, it did not impair general locomotor activity nor induce brain neurotoxicity. Importantly, hippocampal, but not insular cortex, infusions of ara-C also blocked consolidation of context fear conditioning. Separate studies revealed that context fear conditioning training significantly induced nonhomologous DNA end joining activity indicative of DNA ligase-dependent recombination in hippocampal, but not cortex, protein extracts. Finally, unlike inhibition of protein synthesis, systemic ara-C did not block reconsolidation of context fear conditioning. Our results support the idea that DNA recombination is a process specific to consolidation that is not involved in the postreactivation editing of memories.