Improved Measurement of the π→eν Branching Ratio.

A new measurement of the branching ratio R_{e/µ}=Γ(π^{+}→e^{+}ν+π^{+}→e^{+}νγ)/Γ(π^{+}→µ^{+}ν+π^{+}→µ^{+}νγ) resulted in R_{e/µ}^{exp}=[1.2344±0.0023(stat)±0.0019(syst)]×10^{-4}. This is in agreement with the standard model prediction and improves the test of electron-muon universality to the level of 0.1%.

Experimental constraints on left-right symmetric models from muon decay.

The TWIST Collaboration has completed a new measurement of the energy-angle spectrum of positrons from the decay of highly polarized muons. A simultaneous measurement of the muon decay parameters ρ, δ, and P(µ)(π)ξ tests the standard model in a purely leptonic process and provides improved limits for relevant extensions to the standard model. Specifically, for the generalized left-right symmetric model |(g(R)/g(L))ζ|<0.020 and (g(L)/g(R))m(2)>578 GeV/c(2), both 90% C.L.

Measurement of the Michel parameter rho in muon decay.

The TWIST Collaboration has measured the Michel parameter rho in normal muon decay, mu(+)--> e(+)nu(e)nu (mu). In the standard model, rho = 3/4. Deviations from this value imply mixing of left- and right-handed muon and electron couplings. We find rho=0.750 80+/-0.000 32(stat) +/- 0.000 97(syst) +/- 0.000 23, where the last uncertainty represents the dependence of rho on the Michel parameter eta. This result sets new limits on the W(L)-W(R) mixing angle in left-right symmetric models.

Parity violation in proton-proton scattering at 221 MeV.

The parity-violating longitudinal analyzing power, A(z), has been measured in pvectorp elastic scattering at an incident proton energy of 221 MeV. The result obtained is A(z) = [0.84+/-0.29(stat)+/-0.17(syst)]x10(-7). This experiment is unique in that it selects a single parity violating transition amplitude (3P2 - 1D2) and consequently directly constrains the weak meson-nucleon coupling constant h(pp)(rho). When this result is taken together with the existing pvectorp parity violation data, the weak meson-nucleon coupling constants h(pp)(rho) and h(pp)(omega) can, for the first time, both be determined.

Hearing results from endolymphatic sac surgery.

This report examines the effect of the endolymphatic shunt on hearing. The study group was drawn from 101 shunt operations for intractable vertigo between 1983 and 1987. Thirty ears met criteria for diagnosis, level of preoperative hearing impairment, and length of follow-up. The control group consisted of 30 ears with symptoms severe enough to prompt recommendations for shunt surgery, but the patients either opted against surgery or improved. The results were analyzed using the 1985 AAO-HNS reporting criteria. When looking at worst postoperative (or worst scores after 2 years of follow-up in controls) compared to worst preoperative (or worst scores in the first 6 months of presentation in controls), we found no significant difference between the study group (average loss of 9 dB pure-tone average [PTA] and 16% speech discrimination [SD]) as compared to the control group (average loss of 3 dB PTA and 10% SD). However, when using the first and last audiograms for the control group, there was a statistically significant difference as compared to the worst preoperative and postoperative scores in the shunt group. Using the first and last scores, the control group had a better outcome (PTA improved 2 dB, SD score dropped 5%). There was no significant difference between groups for percentage of patients whose hearing improved, remained the same, or worsened. In conclusion, the endolymphatic shunt operation did not significantly effect the long-term hearing results.

Prediction of behavioral threshold and comfort values for Nucleus 22-channel implant patients from electrical auditory brain stem response test results.

We have studied the prediction of behavioral threshold and comfort values for 11 patients who use the Nucleus 22-channel cochlear implant by means of the results of electrical auditory brain stem response (EABR) procedures. For prediction purposes, EABR and behavioral testing were done in the same electrode mode configuration for three specific electrodes. The results of this investigation suggest that EABR threshold current level is consistently near the behavioral comfort current level, rather than the patient's behavioral threshold level.

Electrically evoked auditory brain stem responses (EABR) and middle latency responses (EMLR) obtained from patients with the nucleus multichannel cochlear implant.

Electrical auditory brain stem responses (EABR) and electrical middle latency responses (EMLR) were recorded from patients who had received the Nucleus multichannel cochlear implant system. Twenty-five sequential patients had either intraoperative or outpatient EABR testing. We also recorded EMLRs from several outpatients. EABR results were consistent among all patients tested. Wave V mean latencies were the shortest (3.82 msec) for the most apical electrode (E20) and increased slightly for the medial (E12) and basal (E5) electrodes (3.94 and 4.20 msec, respectively). Absolute latencies for all EABR component waves were observed to be 1 to 1.5 msec shorter than typical acoustic auditory brain stem response (ABR) mean latencies. We have examined the relationships between patients' EABR/EMLR and their behavioral responses to electrical stimulation. Generally, the behavioral threshold and comfort current levels were lower than the predicted values based on EABR/EMLR findings. This observation may be due in part to psychophysical loudness differences noted for pulse rates of 10 to 500 pulses per second in some of the patients that we have studied in greater detail.

Hearing results and control of vertigo after retrolabyrinthine vestibular nerve section.

To determine the effect of retrolabyrinthine vestibular nerve section (RVNS) on hearing, vertigo, and associated symptoms, we reviewed our experience in 48 patients. Of the 48, 39 responded to a questionnaire. Although RVNS appeared to have little effect on hearing in Meniere's patients, 91% of non-Meniere's patients had significant and often delayed postoperative sensorineural hearing loss. Our results for vertigo control compared favorably to previous reports with 96% of Meniere's patients and 69% of non-Meniere's patients reporting improvement. Presently, we more frequently recommend RVNS as the primary procedure for the control of severe vertigo in Meniere's patients. Patients with vertigo from other causes must be carefully selected.

Endolymphatic sac surgery in Mondini's dysplasia: a report of 16 cases.

This paper presents 12 patients (16 ears) with radiographic evidence of Mondini's dysplasia who underwent endolymphatic sac surgery. And additional 4 patients (7 ears) on whom surgery was not performed are included. Class I or II results were obtained in 81% of the ears. Pathophysiology, as it relates to the fluctuant nature of the hearing impairment, is discussed.

Summating potential in Meniere's disease.

This study assesses several electrocochleographic (ECoG) duration and amplitude measures in a clinically defined Meniere's group and compares the results with those from a normal hearing control group and a hearing loss group (cochlear). The summating potential (SP)/action potential (AP) amplitude ratio was the most efficient diagnostic measure, with 62% of the Meniere's group demonstrating abnormal ratios compared to 4% of the normal control group and 17% of the cochlear group. The SP changes were then studied from three angles: 1. Comparison of SP changes with glycerol test results; 2. Comparison of ECoG results before and after shunt surgery; and 3. Recording of SP's in guinea pig ears in which hydrops had been created by obliterating the endolymphatic duct.

Implanted cochlear prosthesis analogue in primates.

Electronic cochlear prostheses are currently being implanted in the profoundly deaf. Little, however, is known about the biologic effects of electrical stimulation of the auditory system. To study some effects of intracochlear electrical stimulation in monkeys, a totally implantable device that produces a constant current similar to that produced by devices now used in human implantation was designed and miniaturized. This paper reports on the characteristics of the device and a pilot project designed to test it in vivo. The feasibility of primate implantation and behavioral observation, as well as histopathologic study, was also determined. The device was implanted in each of two Macacca nemestrina monkeys, which were then observed. One monkey was killed and the implanted cochlea studied with scanning electron microscopy. Evidence of osteogenesis of the scala tympani was found.

Skull base approach to glomus jugulare.

The skull base approach to the jugular bulb provides a better opportunity to preserve facial nerve function. Specifically, this applies to glomus jugulare tumors. Adequate exposure to remove even an extensive glomus jugulare tumor may be obtained by the skull base approach, working between the VIIth nerve left in its bony sheath and the lateral process of the first cervical vertebra.

Ossicular abnormalities in Down's syndrome.

Down's syndrome has been associated with hearing loss and otitis media. Because of difficulty in examination, however, there have been few detailed otologic studies on this population. An understanding of the nature and frequency of ear disease in Down's syndrome is important, since it is common and occurs in more than one in every 600 live births. To define the aural manifestation of Down's syndrome, complete otologic and audiometric examination was performed on 107 consecutive patients. This included micropneumatic otoscopy, pure-tone and speech audiometry, impedance tympanometry, and, in some cases, electronystagmography. Deficient hearing was found in 64% of these patients, and of these hearing losses, 83% were conductive. Surprisingly, middle ear effusion or tympanic membrane perforation accounted for only 60% of the conductive hearing losses. This finding prompted us to examine five temporal bones of children with Down's syndrome. These histologic sections revealed middle ear abnormalities including fixation and superstructure deformity of the stapes and dehiscence of the fallopian canal. Operative findings in 16 procedures on patients with Down's syndrome and conductive hearing loss suport those findings.

Proplast in the middle ear and oval window of cats.

Poly(tetrafluoroethylene) carbon fiber implant material (Proplast), an all-plastic material, was evaluated for use in otologic surgery. Response to the implant was studied in the middle ear and vestibule of 14 cats by placing the Proplast in the oval window after stapedectomy. After a one year follow-up, it appears that Proplast was tolerated well, causing no inflammatory reaction in either the vestibule or cochlea, or in the middle ear cavity. Fibrous tissue ingrowth was found throughout the implant, and a fibrous tissue membrane covered both the vestibular and the tympanic surfaces of the Proplast. Being well tolerated by both middle ear and inner ear tissues, this porous, all-plastic material offers several otologic applications.

Salivary gland choristoma of the middle ear.

We discuss the eighth reported case of a benign salivary gland tumor in the middle ear. The lesion was a smooth lobulated mass and was found to be intimately associated with the tympanic portion of the facial nerve. Recommended treatment is biopsy without attempting removal. This concept of management is supported by a report of a similar case with a 15-year follow-up.