Incipient ferromagnetism in Tb2Ge2O7: application of chemical pressure to the enigmatic spin-liquid compound Tb2Ti2O7.

After nearly 20 years of study, the origin of the spin-liquid state in Tb2Ti2O7 remains a challenge for experimentalists and theorists alike. To improve our understanding of the exotic magnetism in Tb2Ti2O7, we synthesize a chemical pressure analog: Tb2Ge2O7. Substitution of titanium by germanium results in a lattice contraction and enhanced exchange interactions. We characterize the magnetic ground state of Tb2Ge2O7 with specific heat, ac and dc magnetic susceptibility, and polarized neutron scattering measurements. Akin to Tb2Ti2O7, there is no long-range order in Tb2Ge2O7 down to 20 mK. The Weiss temperature of -19.2(1) K, which is more negative than that of Tb2Ti2O7, supports the picture of stronger antiferromagnetic exchange. Polarized neutron scattering of Tb2Ge2O7 reveals that liquidlike correlations dominate in this system at 3.5 K. However, below 1 K, the liquidlike correlations give way to intense short-range ferromagnetic correlations with a length scale similar to the Tb-Tb nearest neighbor distance. Despite stronger antiferromagnetic exchange, the ground state of Tb2Ge2O7 has ferromagnetic character, in stark contrast to the pressure-induced antiferromagnetic order observed in Tb2Ti2O7.

Successive phase transitions and extended spin-excitation continuum in the S=1/2 triangular-lattice antiferromagnet Ba3CoSb2O9.

Using magnetic, thermal, and neutron measurements on single-crystal samples, we show that Ba3CoSb2O9 is a spin-1/2 triangular-lattice antiferromagnet with the c axis as the magnetic easy axis and two magnetic phase transitions bracketing an intermediate up-up-down phase in magnetic field applied along the c axis. A pronounced extensive neutron-scattering continuum above spin-wave excitations, observed below T(N), implies that the system is in close proximity to one of two spin-liquid states that have been predicted for a 2D triangular lattice.

The resurrection of vestibular neurectomy: a 10-year experience with 115 cases.

Between 1925 and 1945, Walter Dandy and Kenneth McKenzie performed more than 700 posterior fossa eighth nerve sections and vestibular neurectomies to treat the intractable vertigo accompanying Ménière's disease. During the past 10 years, with the aid of microsurgical techniques and the approach to the posterior fossa through the temporal bone, vestibular neurectomy has undergone a resurgence of popularity. When hearing is to be preserved, vestibular neurectomy is the surgical treatment of choice for patients who fail to undergo a remission of the vertigo attacks of Ménière's disease. This report reviews 115 consecutive vestibular neurectomies performed from 1978 to 1988 for the treatment of Ménière's disease. In 1978, retrolabyrinthine vestibular neurectomy (RVN), a procedure in which the posterior fossa is entered anterior to the sigmoid sinus and behind the labyrinth, was introduced. During the last 3 years, the approach to the posterior fossa has been a small dural opening behind the sigmoid sinus; this approach is known as the combined retrolabyrinthine retrosigmoid approach. There have been no cases of facial paralysis and no serious complications connected with this technique. A high incidence of headache (50%) resulted when the posterior wall of the internal auditory canal was drilled away for better exposure. Transient cerebrospinal fluid (CSF) leaking occurred in 7% of the patients undergoing RVN; however, no CSF leaks occurred when the combined retrolabyrinthine retrosigmoid approach was used. In the RVN series, wound infection occurred in 20% of the cases until perioperative antibiotics reduced the rate to 3%. The results in terms of curing or improving vertigo have been excellent (94%), and hearing has been preserved to within 20 dB preoperative levels in 76% of the cases. Until a cure for Ménière's disease is found, microsurgical posterior fossa vestibular neurectomy remains the best treatment.

Transmeatal labyrinthectomy with and without cochleovestibular neurectomy.

1. The surgical anatomy and approach to the internal audiotory canal through the transmeatal route is presented. 2. The results of 22 patients undergoing transmeatal labyrinthectomy with cochleovestibular neurectomy indicated that 15 of 20, or 75 percent, had vertigo cured or markedly improved. The best results were found in patients with Ménière's disease (10/10). 3. Similar results were found regarding the symptoms of tinnitus. Fifteen of 22 patients, or 68 percent, had tinnitus cured or markedly improved in a six-month to 36-month follow-up. The best results, again, were found in patients with Ménière's disease (8/10). 4. Patients undergoing transmeatal labyrinthectomy without cochleovestibular neurectomy showed only one of six cases with improvement of tinnitus and three of six cases with vertigo cured or markedly improved. 5. Transmeatal labyrinthectomy with cochleovestibular neurectomy appears to have the following advantages over transmeatal labyrinthectomy or translabyrinthine section of the VIIIth nerve: a. The surgical time is shortened by the direct route to the internal auditory canal. b. A second procedure is avoided by not having to obtain abdominal adipose tissue for obliteration of the mastoid cavity. c. Complete unilateral ablation of vestibular function is assured. d. Best chance of alleviation or improving tinnitus. e. The internal auditory canal is routinely inspected to be sure no acoustic neuroma or other pathology is found. f. Skill is obtained in transecting the "singular nerve."

The effect of the endolymphatic subarachnoid shunt operation on vestibular function.

Preoperative vestibular function was studied in 56 patients undergoing the endolymphatic subarachnoid shunt procedure for Ménière's disease by electronystagmographic recording of bithermal air caloric stimulation. Fifty-two percent had normal vestibular function while 48% had a reduced vestibular response on the affected side using 20% difference as being significant. Best results of surgery with relief of vertigo were found in the group of patients with normal preoperative vestibular function (82%) while the group with reduced vestibular response preoperatively showed 63% with a good result. Postoperatively, 81% had a reduced vestibular response in the operated-on ear with 62% obtaining relief of vertigo. In patients with normal vestibular function postoperatively excellent relief of vertigo was obtained. Of patients with normal vestibular function preoperatively, 69% developed a reduced vestibular response postoperatively with only 55% having relief of vertigo. The results of surgery could be predicted more accurately using the results of vestibular function tests than audiometric data. It appears that for best results the endolymphatic subarachnoid shunt procedure should be performed early in the course of Ménière's disease when hearing is fluctuating and vestibular function is normal.

A comparison of retrosigmoid IAC, retrolabyrinthine, and middle fossa vestibular neurectomy for treatment of vertigo.

A new procedure, the retrosigmoid internal auditory canal (IAC) vestibular neurectomy has been developed and presented. It involves a 3-cm retrosigmoid craniotomy removing the posterior wall of the IAC to the singular canal, with transection of the superior vestibular nerve and posterior ampullary nerve. This produces a complete denervation of the vestibular labyrinth and preserves the patient's hearing. All ten patients with Meniere's disease had their vertigo cured. Hearing was preserved to within 11 dB of the preoperative pure tone average in 9 of 10 cases. There were no serious complications, no cases of facial paralysis, and no cases of total hearing loss. These results compare favorably with the MFVN and the RVN. The retrosigmoid IAC vestibular neurectomy is an important improvement in the evolution of vestibular neurectomy for the treatment of vertigo.

Compatibility of the argon and KTP lasers with middle ear implants.

Visible-spectrum lasers (argon, KTP) are becoming common tools in otology. Concern over transmission of disease by homograft tissue has focused attention on synthetic materials such as Silastic, Polycel, hydroxylapatite, and Teflon. This study sought to determine the effects of argon and KTP lasers on materials used in stapes and chronic ear surgery. Silastic sheeting, hydroxylapatite and polycel total ossicular replacement prostheses (TORPs) and partial ossicular replacement prostheses (PORPs), and platinum wire/Teflon stapes prostheses were exposed to argon and KTP laser energy at clinical power settings. Effects of the two lasers were similar. The presence of pigment (char or blood) was necessary to produce any effect. Silastic transmitted energy to underlying material. Hydroxylapatite cracked and shattered. Polycel vaporized and melted, as did Teflon. Clinical implications of these interactions on primary and revision otologic surgeries will be discussed.

Wide surgical exposure for singular neurectomy in the treatment of benign positional vertigo.

Since 1972, singular neurectomy has been performed on 58 patients who had classical benign positional vertigo. The procedure is done under general anesthesia; a wide postauricular exposure is made and the external auditory canal is maximally enlarged until the vertical portion of the facial nerve is identified. This gives an excellent view of the round window niche. Our results indicate vertigo was completely cured in 80% of the cases and improved in 17%. There has been no incidence of total hearing loss in the last 49 cases and only 3 of 49 patients (6%) had sensorineural loss. Although singular neurectomy can be mastered, it will remain a procedure done by few surgeons. The wide exposure technique is safer for preservation of cochlear function and the posterior ampullary nerve is easier to find than using the transmeatal approach as described by Gacek.

Small fenestra stapedotomies with and without KTP laser: a comparison.

The results of 33 small fenestra stapedotomies performed using conventional techniques were compared with the results of 33 stapedotomies performed using the argon or KTP laser. The ossicular chain was reconstructed using a Teflon wire piston of 0.6 mm diameter, and follow-up was at least 1 year. Over-closure of the air-bone gap or closure to within 10 dB was accomplished in 91% of the laser-treated group versus 72% of the conventionally treated group (p less than 0.10). The hearing results were statistically better in the laser group (p less than 0.05). Transient delayed vestibular symptoms, lasting from 1 to 3 weeks, were present in 39% of the laser-treated group and in 12% of the patients treated by conventional techniques (p less than 0.05). The KTP laser stapedotomy, using a micromanipulator mounted on the microscope, is a safe, efficient technique that reduces some of the technical difficulties associated with conventional stapes surgery. The main advantage of the laser is that it enables the surgeon to make an atraumatic, bloodless opening in a fixed or mobile stapes footplate without mechanical manipulation of the stapes. Using a lower wattage to vaporize the footplate and waiting several seconds between laser bursts may decrease the incidence of postoperative vestibular symptoms. The use of the KTP laser in stapes surgery represents a major advance in surgery for otosclerosis.

Permanent middle ear aeration: long-term follow-up of transosseous ventilating tubes.

A technique for achieving permanent middle ear aeration by inserting a flanged silicone tube (SPAT) through a hole drilled in the external auditory canal was introduced in 1970. Since 1970, we have used the transosseous procedure in 36 patients (11%) of cases that required middle ear ventilation. The average length of time the transosseous SPAT functioned was 51 months (range 0-138). Best results were obtained in patients over 16 years of age, when chronic ear surgery was not performed simultaneously. Transient otorrhea occurred in 23% of cases. Forty-four percent of tubes became blocked and required removal or were extruded. No patient developed facial weakness, middle ear cholesteatoma, or persistent tympanic membrane perforation. In selected cases, the transosseous SPAT provides long-term middle ear aeration without the risk of permanent tympanic membrane perforation.

Routine identification of the facial nerve using electrical stimulation during otological and neurotological surgery.

We routinely identify the facial nerve to avoid facial nerve injury during most otologic surgery. Since 1985, we have used a facial nerve stimulator/monitor as an added safety feature in 383 consecutive otologic and neurotologic cases. In our last 30 middle-ear, 8 retrolabyrinthine vestibular neurectomy, and 14 acoustic neuroma cases we used the monopolar stimulator probe-tip to determine threshold currents needed to produce facial twitch. Stimulation thresholds varied according to the amount of soft tissue or bone overlying the facial nerve. The stimulator was useful for predicting dehiscences in the bony facial canal during middle-ear and mastoid surgery. The exposed facial nerve usually stimulated at a level less than 0.1 mA (mean 0.05 mA), and the horizontal facial nerve covered by bone stimulated at 0.25 mA or greater (mean 0.6 mA). The stimulator was also used to predict the amount of bone overlying the vertical facial nerve at the annulus. An approximate relationship of 1.0 mA of threshold current to 1.0 mm of bony covering was found. After acoustic neuroma surgery, the stimulation threshold of the facial nerve at the brain stem helped predict postoperative facial function. Cases with current thresholds of 0.3 mA or less resulted in normal facial function. During ear surgery, routine identification of the facial nerve with the aid of a facial nerve stimulator will help avoid facial nerve injury.

Conservative management of acoustic neuroma in the elderly patient.

A subtotal resection through the translabyrinthine approach should be used in the treatment of large symptomatic acoustic neuromas in patients over the age of 65. This approach will consistently relieve the patient's symptoms of brain stem compression, reduce postoperative morbidity and complications, and preserve facial nerve function. In the elderly, after subtotal resection, the remaining tumor in 80% of cases appears to remain dormant during the average six year follow-up (1-16 year range). Eighty percent of acoustic neuromas not operated upon, appear to grow at a slow rate (0.2 cm/yr) while 20% grow at a fast rate (1 cm/yr). Patients over the age of 65 with small acoustic neuromas do not need surgical intervention. Yearly CT scanning is recommended to determine the growth rate of the acoustic neuroma. A conservative approach should be used in the treatment of all acoustic neuromas in the elderly.

Revision stapes surgery with and without laser: a comparison.

In this study, the results of 76 revision stapes surgeries performed from 1974 to 1992 were reviewed. Either the KTP or the argon laser was used in 40 operations. Prosthesis problems were the most common cause for revision (63%) followed by eroded/necrotic incus (29%) and adhesions (29%). Overall "success" in air-bone gap closure (air-bone gap < or = 10 dB) was 46% for first revisions and 33% for second or greater revisions. The "improvement" rate (air-bone gap < or = 20 dB) was 65% for first revisions and 53% for second or greater revisions. There was no statistically significant difference in hearing results between laser surgery and conventional technique. However, an absence of adhesions was noted when the laser had been used in the primary procedure.

A comparison of PORP, TORP, and incus homograft for ossicular reconstruction in chronic ear surgery.

This report presents the results of 210 cases over a 10-year period using PORPs, TORPs, and notched incus homografts (NIH), for ossicular reconstruction in chronic ear surgery. There were 192 adults and 18 children. The surgical technique utilized temporalis fascia in an underlay technique with canal skin covering the outer surface of the fascia. Intact canal wall mastoid-tympanoplasty, as a one-stage procedure, was used for most cases. Homograft nasal cartilage was placed between the Plasti-Pore prosthesis and the graft. Notched incus homografts were prepared prior to surgery and stored in 4% formalin. There were 149 mastoid-tympanoplasties and 61 tympanoplasties performed. Revision of our cases was performed in 16.6%. Within 3 months of surgery, 86% of adults, and 44% (8/18) of children had dry, healed ears free of disease. The graft take rate was 96%. In adults, a total of 99 NIH, 50 TORPs, and 43 PORPs were implanted. In adults, the closure of the air-bone gap to 20 dB or less occurred in 58% using TORPs, 67% using PORPs, 76% using NIH-Partial replacement, and 20% using NIH-Total replacement. Excluding the cases that failed for reasons other than conductive hearing loss, the results improved to 69% for TORPs, 77% for PORPs, 77% for NIH-P, and 27% for NIH-T. In adults, the extrusion rate was 5.5% for Plasti-Pore and 3% for NIH. In children, the extrusion rate was 17% for Plasti-Pore prostheses. From this study, it appears that PORPs and TORPs with homograft nasal cartilage are satisfactory prostheses for chronic ear surgery in adults. In children, Plasti-Pore prostheses should be avoided unless the ear is healed, aerated, and stable. NIHs are good prostheses when the stapes is intact, but they are inferior to the TORP when placed on the footplate. Also, the NIH requires preparation prior to surgery and may be difficult to obtain. We plan to continue using PORPs and TORPs in chronic ear surgery until a better technique is found, or the complication rate becomes unacceptable.

Pediatric laser-assisted tympanostomy.

OBJECTIVE: To evaluate effectiveness of laser-assisted tympanostomy in treatment of pediatric patients with chronic otitis media with effusion. STUDY DESIGN: Retrospective review of 23 pediatric patients who received office laser-assisted tympanostomy. METHODS: A CO2 laser attached to an operating microscope with a microscope laser adaptor device or the handheld Oto-LAM (Needham, MA) was used to perform all of the tympanostomies. The average diameter of tympanostomy was 2 mm; on average, 13.6 W was applied for 0.13 seconds. RESULTS: Laser-assisted tympanostomy was performed on 37 pediatric ears (patient age range, 2-16 y) for the diagnosis of chronic otitis media with effusion. Average follow-up time was 4.7 weeks. At the time of the follow-up examination, 46% of the ears had no evidence of fluid and required no further intervention. Forty-nine percent of the ears required placement of pressure equalization tubes. The average SRT improved from 30.8 dB preoperatively to 21.03 dB postoperatively. CONCLUSIONS: Laser-assisted tympanostomy appears to be an effective treatment for chronic otitis media with effusion in pediatric patients.

Sudden sensorineural hearing loss after general anesthesia for nonotologic surgery.

Sudden sensorineural hearing loss (SNHL) is a well-recognized phenomenon that is attributed to a variety of etiologies. Sudden SNHL after cardiopulmonary bypass surgery has been well reported and is thought to be due to microemboli. However, a review of the English literature revealed only 15 cases of SNHL after general anesthesia for nonotologic surgery. Several etiologies for this loss have been suggested, but no proven pathogenesis is yet available. This report adds to the literature three additional cases of sudden SNHL after general anesthesia for nonotologic surgery. The literature is reviewed and proposed mechanisms of injury are discussed.

Prediction of facial nerve function following acoustic neuroma resection using intraoperative facial nerve stimulation.

Methods of monitoring the facial nerve during posterior fossa surgery continue to evolve. In an effort to predict acute and final facial nerve function following acoustic neuroma resection, the lowest current applied to the facial nerve at the brainstem necessary to elicit facial muscle response was measured using strain gauge and electromyographic facial nerve monitors. A retrospective analysis of 121 patients who had undergone acoustic neuroma surgery was performed. Sixty-five patients had intraoperative facial nerve monitoring and 44 had sufficient data for inclusion in this study. The acute and final facial nerve functions, according to the House-Brackmann classification, were assessed with regard to intraoperative stimulation-current thresholds. Nineteen of 20 patients who required 0.10 mA or less to elicit a facial muscle response had a House-Brackmann grade I facial nerve outcome. The upper limit of the 95% confidence interval of stimulation threshold for patients with a final grade I facial nerve function is 0.17 mA. All of the patients in this study, with stimulation thresholds ranging up to 0.84 mA, had a final grade III or better result. A poor outcome in our series, a final grade III facial nerve function, is best predicted by a poor acute result, specifically an acute grade VIA facial nerve function. We suggest that it is possible to predict the facial nerve function based on intraoperative threshold testing.

Preservation of the stapedius tendon in laser stapes surgery.

OBJECTIVES/HYPOTHESIS: The stapedius tendon is routinely transected during stapes surgery. The objective of this study was to evaluate the technique of stapedial tendon preservation during stapes surgery and to compare results of these cases with cases where the stapedial tendon was not preserved. STUDY DESIGN: Retrospective study. METHODS: Four groups of patients were evaluated. Two groups had undergone stapes surgery with preservation of the stapedial tendon. One of these groups underwent a laser stapedotomy minus prosthesis (laser STAMP) procedure, while the other group had a prosthesis inserted. The other two groups had undergone laser stapedotomy with one of two different prostheses being used. Audiometric data were obtained and reviewed both preoperatively and at approximately 6 weeks postoperatively. RESULTS: All groups had overall successful results demonstrating that stapedial tendon preservation is technically possible and does not compromise outcomes. CONCLUSIONS: Based on the results, it is recommended that the stapedius tendon be preserved whenever possible during laser stapes surgery. Reasons justifying its preservation are discussed.

Effect of melatonin on tinnitus.

OBJECTIVE: Evaluate melatonin as a treatment for subjective tinnitus. STUDY DESIGN: Randomized, prospective, double-blind, placebo-controlled crossover trial. Patients were given 3.0 mg melatonin, which was taken nightly for 30 days followed or preceded by a placebo nightly for 30 days, with a 7-day washout period between medications. SETTING: Outpatient, private, neurotology practice. PATIENTS: Thirty patients with subjective tinnitus. MAIN OUTCOME MEASURES: Tinnitus matching, Tinnitus Handicap Inventory (THI), patient questionnaire and interview. RESULTS: The average pretreatment THI score was 33.91 as compared with 26.43 after the placebo and 26.09 after melatonin. The difference in the THI scores between melatonin and placebo treatment were not statistically significant. The average pretreatment THI score for patients who reported overall improvement with melatonin was statistically higher (P = 0.02) than the average pretreatment THI score for patients who reported no improvement with melatonin. Among subjects reporting difficulty sleeping attributable to their tinnitus, 46.7% reported an overall improvement after melatonin compared with 20.0% for placebo (P = 0.04). There was also a statistically significant difference in improvement with melatonin for those patients with bilateral tinnitus compared with those with unilateral tinnitus (P = 0.02). CONCLUSION: Melatonin has been shown to be useful in the treatment of subjective tinnitus. Patients with high THI scores and/or difficulty sleeping are most likely to benefit from treatment with melatonin. In light of its minimal side effects, melatonin should be a part of the physician's armamentarium in the treatment of tinnitus.

Laser-assisted tympanostomy.

Laser-assisted tympanostomy (LAT) was performed in 70 ears to ventilate the middle ear space without using a pressure-equalizing tube. Using a CO2 laser attached to an operating microscope with a Microslad (microscope laser adaptor device), tympanostomies of 1.0 to 3.0 mm (average, 1.6 mm) in diameter were created and remained patent for an average of 3.14 weeks. Patency time was directly related to the size of the opening. Nearly all (97.9%) of the tympanostomies healed with no noticeable scarring and no persistent perforations. Seventy-eight percent of patients at the Florida Ear & Sinus Center (FESC, Sarasota, Fla.) and 84% of patients at the Head & Neck Surgery Group (New York) showed no evidence of recurrent effusion after a minimum follow-up of 3 months. LAT appears to be a safe, cost-effective procedure which can easily be performed in an office setting when bloodless opening in the tympanic membrane is needed for either treatment or diagnosis using endoscopes.