Bending the curve: preoperative determination of bypass graft length and trajectory with curved planar reformatted computed tomography angiography: technical note.

BACKGROUND AND IMPORTANCE: Cerebral revascularization continues to be an important technique for the treatment of cerebrovascular and vaso-occlusive diseases, and determination of appropriate graft sources and recipients is paramount to the success of the procedure. A tension-free anastomosis requires that harvested grafts be of an appropriate length to avoid complications. Volume-rendered contrast-enhanced computed tomography data sets may be useful in determining the desired length and path of the bypass graft and in the evaluation of appropriate recipient vessels. Curved planar reformation techniques may allow these properties to be determined in a novel, inexpensive, and efficient manner. CLINICAL PRESENTATION: A 63-year-old patient with a left hemispheric perfusion deficit and without an external carotid artery was in need of high-flow cerebral revascularization. A radial artery graft spanning from the vertebral artery to the middle cerebral artery was proposed. Preoperative determination of graft length necessary and most efficient subcutaneous placement was desired. A standard computed tomography angiogram of the head and neck was obtained and imported into a computer workstation with curved planar reformatting capabilities. CONCLUSION: Curved planar reformation technique can be used for preoperative planning of cerebral bypass procedures and is a novel, inexpensive, and efficient means of determining the desired length and path of the bypass graft and in the evaluation of appropriate recipient vessels.

Outcomes in children with perforated tympanic membranes after tympanostomy tube placement: results using a pilot treatment algorithm.

PURPOSE: The objective of this study was to examine the success of a pilot treatment algorithm for tympanic membrane perforations in children after tympanostomy tube placement. MATERIALS AND METHODS: A retrospective chart review of children with diagnosed tympanic membrane perforations after tympanostomy tube placement from 1998 to 2003 at a tertiary care children's hospital was performed. The patients had been treated according to an algorithm used by 2 pediatric otolaryngologists for management of tympanic membrane perforations: observation vs myringoplasty. Success rates were examined. RESULTS: Ninety-five children were identified, 27% of whom had nonhealing perforations after tube extrusion; 73% of the perforations were caused by a retained tube. The median duration of tube retention was 48 months, ranging from 13 to 120 months. After the treatment protocol, 76% of the patients underwent gelatin film or paper patch myringoplasty, 23% had adipose myringoplasty, and 1% were observed. Overall, 91% had healed perforations after the first intervention. Among those requiring a second intervention, the sizes of initial perforations were between 15% and 40%, with postrepair perforation sizes between 5% and 40%. In addition, 75% of those requiring a second intervention underwent tympanoplasty repair and 25% had fat patch myringoplasty. None required a third intervention. CONCLUSIONS: Our treatment algorithm for children with tympanic membrane perforations after tympanostomy tube placement appears to be successful and is an excellent model for other clinicians.

The role of Trp side chains in tuning single proton conduction through gramicidin channels.

We present an extensive set of measurements of proton conduction through gramicidin A (gA), B (gB), and M (gM) homodimer channels which have 4, 3, or 0 Trp residues at each end of the channel, respectively. In gA we find a shoulder separating two domains of conductance increasing with concentration, confirming the results of Eisenman, G., B. Enos, J. Hagglund, and J. Sandblom. 1980. Ann. NY. Acad. Sci. 339:8-20. In gB, the shoulder is shifted by approximately 1/2 pH unit to higher H(+) concentrations and is very sharply defined. No shoulder appears in the gM data, but an associated transition from sublinear to superlinear I-V values occurs at a 100-fold higher [H(+)] in gM than in gA. The data in the low concentration domain are analyzed using a configuration space model of single-proton conduction, assuming that the difference in the proton potential of mean force (PMF) between gA and its analogs is constant, similar to the results of Anderson, D., R. B. Shirts, T. A. Cross, and D. D. Busath. 2001. Biophys. J. 81:1255-1264. Our results suggest that the average amplitudes of the calculated proton PMFs are nearly correct, but that the water reorientation barrier calculated for gA by molecular dynamics using the PM6 water model (Pomès, R., and B. Roux. 1997. Biophys. J. 72:246a) must be reduced in amplitude by 1.5 kcal/mol or more, and is not rate-limiting for gA.