Medium-Term Outcomes after Reversal of Roux-en-Y Gastric Bypass

BACKGROUND

Roux-en-Y gastric bypass (RYGB) can be reversed into normal anatomy (NA) or into sleeve gastrectomy (NASG) to address undesired side effects. Concomitant hiatal hernia repair (HHR) may be required. Before reversal, some patients benefit from placement of a gastrostomy, mostly to predict the result of recreating the native anatomy.

METHODS

Retrospective study on mid-term effects of RYGB reversal to NA and NASG, including clinical and weight evolution, surgical complications, and incidence of gastro-esophageal reflux (GERD).

RESULTS

Undesired side effects leading to reversal included early dumping syndrome, hypoglycemia, malnutrition, severe diarrhea and excessive nausea and vomiting. Twenty-five participants to the study, 13 NA, 12 NASG, and 15 HHR. Mean follow-up time was 5.3 ± 2.3 years. Reversal corrected early dumping, malnutrition, diarrhea, and nausea/vomiting. For hypoglycemic syndrome, resolution rate was 6/8 (75%). NA caused significant weight regain (14.2 ± 13.7 kg, (p = .003)). NASG caused some weight loss (4.8 ± 15.7 kg (NS)). Gastrostomy placement gave complications at reversal in five of seven individuals. Eight patients suffered a severe complication, including leaks (one NA vs. three NASGs). Eight out of 14 (57.1%) patients who previously had never experienced GERD developed de novo GERD after reversal, despite HHR.

CONCLUSIONS

RYGB reversal is effective but pre-reversal gastrostomy and concomitant HHR may be aggravating factors for complications and development of de novo GERD, respectively.

Hearing Aids Using Binaural Processing Principles

The performance of normal human hearing in noisy circumstances is helped considerably by its ability to focus on a specific sound source. This ability is derived from the binaural nature of hearing. In this paper we present signal-processing techniques that can partially replace the binaural hearing in situations where a monaural hearing aid is used (monaural deafness, cochlear implants). First, simple noise cancellation and beam forming solutions, which are applicable to speech, are presented. Then full adaptive filter versions and a successful combination of both are proposed. A key element to the success of all these algorithms is the use of a noise versus speech discrimination criterion on which basis selected parts of the adaptive filter structure are adapted at any given moment.

Pitch perception by cochlear implant subjects

Direct electrical stimulation of the auditory nerve can be used to restore some degree of hearing to the profoundly deaf. Percepts due to electrical stimulation have characteristics corresponding approximately to the acoustic percepts of loudness, pitch, and timbre. To encode speech as a pattern of electrical stimulation, it is necessary to determine the effects of the stimulus parameters on these percepts. The effects of the three basic stimulus parameters of level, repetition rate, and stimulation location on subjects' percepts were examined. Pitch difference limens arising from changes in rate of stimulation increase as the stimulating rate increases, up to a saturation point of between 200 and 1000 pulses per second. Changes in pitch due to electrode selection depend upon the subject, but generally agree with a tonotopic organization of the human cochlea. Further, the discriminability of such place-pitch percepts seems to be dependent on the degree of current spread in the cochlea. The effect of stimulus level on perceived pitch is significant but is highly dependent on the individual tested. The results of these experiments are discussed in terms of their impact on speech-processing strategies and their relevance to acoustic pitch perception.

Current Spreading and Speech-Processing Strategies for Cochlear Prostheses

It is well known that current spreading in the cochlea causes a blurring at the excitable neural tissue of spatial details when the electrode array is stimulated. This paper describes techniques for compensating for current spreading by computing the pseudoinverse of the spreading function and applying a stimulation pattern to the electrode array, which produces the desired current pattern at the neural tissue. Specific examples are given assuming several current spreading functions, and the limits of applicability of the techniques in the domain of severe current spreading are explored.

Comparison of different speech processing strategies on patients receiving the same implant

Two subjects with transcutaneously connected 8-electrode scala tympani implants were given subsets of the Minimal Auditory Capabilities test during stimulation with five speech processing strategies--two single channel and three multichannel. While there were significant (p = 0.05%) scores on some items with all types of stimulation, one subject did as well with single channel analog as with multichannel stimulation. She is an enthusiastic full-time user of single channel stimulation. The other, a nonuser of the same device, preferred (and performed better with) one of multichannel stimulation. This is an interim report because neither subject has yet had the opportunity of nonlaboratory use of the multichannel schemes.