A short-wavelength infrared emitting multimodal probe for non-invasive visualization of phagocyte cell migration in living mice.

For the non-invasive visualization of cell migration in deep tissues, we synthesized a short-wavelength infrared (SWIR) emitting multimodal probe that contains PbS/CdS quantum dots, rhodamine 6G and iron oxide nanoparticles. This probe enables multimodal (SWIR fluorescence/magnetic resonance) imaging of phagocyte cell migration in living mice.

Auditory brainstem implants: current state and future directions with special reference to the subtonsillar approach for implantation.

In this article, the authors describe the current state of the auditory brainstem implant (ABI), comparing it to that of the cochlear implant (CI). The CI restores hearing by stimulating the cochlear nerve in the cochlea in patients whose deafness has been caused by inner ear disease; the ABI restores hearing by stimulating the cochlear nucleus of the brainstem in patients who are deaf because of bilateral cochlear nerve dysfunction. Up to now, about 500 patients worldwide have undergone ABI and had their hearing restored, most of whom suffer from neurofibromatosis type 2. Hearing performance, however, is not as good as that offered by the cochlear implant. To improve the quality of hearing, new techniques such as advanced coding strategies and penetrating electrodes, are now being introduced.

Subtonsillar placement of auditory brainstem implant.

A 26-year-old female with NF2 underwent removal of an acoustic schwannoma via extended retrosigmoid approach with subtonsillar placement of the auditory brainstem implant. The patient had already shown palsy of the lower cranial nerves on the opposite side due to previous surgery. Differing from conventional routes such as the translabyrinthine and the retrosigmoid, the subtonsillar approach enabled us to observe the entire cochlear nucleus and avoid injury to the 9th and 10th cranial nerves when applying the electrode. Hearing in pure tone average was maintained almost at the preoperative level. We present a new use of this approach in placing the electrode and discuss its advantages.

Audiological findings in patients with myoclonic epilepsy associated with ragged-red fibres.

Sensorineural hearing loss is a common symptom in patients with myoclonic epilepsy associated with ragged-red fibres (MERRF), one of the mitochondrial encephalomyopathies, although the lesion causing hearing loss in such cases remains unknown. Here we describe the audiological features in three MERRF patients, all of whom exhibited a point mutation in their mitochondrial DNA at nucleotide 8344. Pure-tone threshold audiometry revealed bilateral, sloping-type, sensorineural hearing loss in all three patients. Distortion product otoacoustic emissions, electrocochleography, and auditory brainstem responses were variable, even differing between the right and left ears of the same patient. Taken together, our findings suggest that the primary lesion underlying hearing loss in MERRF patients is in the cochlea, although a retrocochlear lesion may be involved in some patients.

Cross-sectional shapes of the internal auditory canal in patients with acoustic neuromas.

Cross-sectional images of the internal auditory canal (IAC) were investigated in 23 patients with acoustic neuroma in order to clarify the widening of the IAC. The area of the IAC and the ratio of areas (neuroma side:normal side) were calculated. The shape of the IAC was fitted by an ellipse to obtain the length of the axes and the direction of the long axis. The area of the IAC was 34.2+/-12.2 mm2 in the neuroma side and 18.1+/-4.8 mm2 in the normal side. The neuroma side was larger than the normal side in all patients, and the mean ratio of areas was 1.9. However, the degrees of cochlear and vestibular damage did not correlate with the ratio of areas. The mean ratio of axes of the approximated ellipse was 1.17+/-0.09 in the neuroma side and 1.14+/-0.10 in the normal side; however, no significant difference was seen between the ratio of axes. The directions of the long axes were not always consistent with the positions of the originating nerves of the tumour. Referring to hypothetical models of enlargement of the IAC, our data suggest that the widening of the IAC in the acoustic neuroma was expansive. The data also indicated that symptoms of the acoustic neuroma were caused not only by compression of the nerves but also by other mechanisms, such as vascular insufficiency to the inner ear.

Postoperative vestibular-evoked myogenic potentials in cases with vestibular schwannomas.

Although still the subject of discussion, vestibular-evoked myogenic potentials (VEMPs) have been considered to reflect the function of the saccular and, more recently, the cochlear tracts. To accurately determine the precise afferent pathway carrying VEMPs, we studied the outcomes of VEMPs and other examinations in patients with unilateral vestibular schwannomas. Eleven patients with unilateral vestibular schwannomas resected using a middle cranial fossa approach were included in the study. Patients underwent pure-tone threshold audiometry, caloric tests and analysis of auditory brainstem responses (ABRs) and VEMPs pre- and postoperatively. The results were compared with those obtained in patients with intact superior or inferior vestibular and cochlear nerves. Among the 11 patients studied, 4 retained their VEMPs postoperatively. Three of the 10 patients with inferior vestibular schwannomas exhibited normal VEMPs, preserved hearing levels (20 dB HL) and anatomically intact superior vestibular nerves. In all of these cases, ABRs more closely correlated with VEMPs than with caloric responses. In one of the cases with inferior vestibular schwannomas, VEMPs were preserved postoperatively and VEMP latencies were shortened, which indicates the preoperative presence of a conduction block in either the cochlear or superior vestibular nerve. VEMPs may be conducted in both the superior vestibular and cochlear nerves, as well as in the inferior vestibular nerve. Thus, evaluation of saccular nerve function should be performed carefully, especially in cases where hearing is preserved. It appears that cochlear conduction may proceed along two pathways, one direct and the other via the brainstem, but this remains to be verified.

[Speech perception ability in a patient with a 8-channel auditory brainstem implant].

Auditory brainstem implant (ABI) is a central prosthesis that directly stimulates the cochlear nucleus in the brainstem for those who have interrupted auditory nerves and cannot benefit from the cochlear implantation. Speech perception in a recipient of the Nuclues 8 channel ABI, the first in Japan, is reported. A 25-year-old man with bilateral acoustic nerve tumors postlingually deafened due to tumor resection received auditory sensations with 5 channels. The correct answer using a coding strategy, SPEAK, was 35% for 5 vowels and 36% for 5 monosyllables. The use of ABI also improved his lip-reading ability on monosyllables and open-set words. This indicated that he benefited from ABI, although it was limited. Even after 1 year and 3 months of follow-up, he had no serious side effects such an infection or implant rejection.

Nerve origin of the acoustic neuroma.

Two hundred and seventy-one Japanese patients who underwent surgical removal of neuroma from the cerebello-pontine angle using the translabyrinthine approach were retrospectively reviewed in order to investigate the nerve origin on an anatomical basis. In 269 out of the 271 cases, the origin of the neuromas was identified. Among these cases, 84.8 per cent of tumours originated from the inferior vestibular nerve (IVN), followed by the superior vestibular nerve (SVN) (8.9 per cent). Of the 5.6 per cent of tumours arising from the vestibular nerve, however, it could not be determined whether they originated from the SVN or IVN. Two cases of neuromas originating from the facial nerve were seen (0.7 per cent). No neuroma arose from the cochlear nerve. Currently, the diagnosis of acoustic neuromas is best made with Gd-enhanced magnetic resonance imaging (MRI). However, our data indicate that the development of a functional test of the individual IVN can be useful for screening most cases of acoustic neuroma and in facilitating their early diagnosis.

Three-dimensional image for the middle fossa approach and its anatomical considerations.

OBJECTIVE: To investigate the usefulness and significance of three-dimensional images in the middle cranial fossa approach. STUDY DESIGN: Retrospective study. METHOD: Three-dimensional images of 12 patients with acoustic neuromas were made for surgical guidance. An image showing an ideal surgical view was prepared, which showed no overlap between the labyrinthine bone and internal auditory canal (IAC) with a slight gap between them. The IAC was located and opened referring to this image. RESULTS: Directions of the images in the ideal surgical view were anterior from lateral position in all cases. Viewing toward the vestibule, angle from lateral plane was 24 degrees +/- 12 degrees (mean +/- standard deviation). In 11 of 12 patients, the IAC was safely opened; in one patient the IAC could not be opened because of bleeding. Overall hearing preservation rate was 82%. CONCLUSION: Our method facilitated not only in the identification of the IAC but also in avoiding inner ear damage. Our data indicated that the center of craniotomy should be made anterior to the external auditory canal and surgery should be viewed from an anterolateral position for a safe procedure.

Restoration of hearing with an auditory brainstem implant in a patient with neurofibromatosis type 2--case report.

A 25-year-old male with neurofibromatosis type 2 had hearing restored with an auditory brainstem implant (ABI) after removal of an acoustic schwannoma. The ABI allows the patient to discern many different environment sounds and is a significant adjunct to lip-reading, enabling conversation with people who have clear pronunciation without the necessity for writing.

Tumor volume measurements of acoustic neuromas with three-dimensional constructive interference in steady state and conventional spin-echo MR imaging.

The purpose was to compare three-dimensional (3D) constructive interference in steady state (CISS) and conventional spin-echo (SE) MR imaging in tumor volume measurements of acoustic neuromas. Twenty-two patients with acoustic neuromas were examined using high-resolution 3D-CISS and SE imaging at a 1.5-T system. Tumor volume determined by SE imaging with the ellipsoid formula was overestimated by 692 mm(3)(35%) on average as compared with that at 3D-CISS with the voxel-count method (the reference standard). Intra- and interobserver variations in SE imaging were poor as compared with 3D-CISS imaging. However, tumor volume results with SE imaging showed a high correlation with those using 3D-CISS imaging (P <. 0001). On the basis of diameters shown on SE images, the tumor volume could be assessed using the following equation (P <.0001): (Tumor volume) = -26.407 + 0.387 x (maximum diameter along the pyramid) x(maximum diameter perpendicular to the pyramid) x (maximum height). J. Magn. Reson. Imaging 2000;12:826-832.

Prediction of the nerves of origin of vestibular schwannomas with vestibular evoked myogenic potentials.

OBJECTIVE: To determine whether the nerves of origin of vestibular schwannomas can be predicted using vestibular evoked myogenic potentials (VEMPs). STUDY DESIGN: The study was a retrospective analysis. SETTING: The ear, nose, and throat department of Tokyo Medical and Dental University. PATIENTS: Twenty-eight patients undergoing removal of vestibular schwannomas were included in the study. INTERVENTIONS: Patients underwent pure tone audiometry, VEMP testing, caloric testing, and magnetic resonance imaging preoperatively. Hearing level, caloric weakness, maximum tumor size, and the nerves of origin of tumors were compared with VEMP testing. MAIN OUTCOME MEASURE: Results of VEMP testing. RESULTS: Comparisons between VEMPs and results of the other three examinations revealed no correlations. Complete disappearance of VEMPs was observed only in patients with tumors arising from inferior vestibular nerves. Patients in whom hearing was preserved tended to have preserved VEMPs. Some patients showed damaged hearing and normal VEMP results, although with inferior vestibular schwannomas. A patient with a tumor arising from a cochlear nerve exhibited preservation of VEMP, preserved caloric response, and moderate hearing loss. CONCLUSIONS: Inferior vestibular nerve function and hearing level were reflected in VEMP results. Prediction of the nerve of origin of a tumor was possible only in certain restricted cases.

A clinically oriented video-based system for quantification of eyelid movements.

A field-worthy system was developed to quantify the eyelid movements in clinical sites. The system consists of a home-use charge-coupled device video camera, a processing unit, and a personal computer. A white marker of 4-mm diameter and 30-mg weight is attached to the lower margin of the upper eyelid. The processing unit automatically detects the vertical displacement of the upper edge of the marker. One marker is attached to each eye so that the movements of the both eyelids are measured with one camera simultaneously. The measurement error of the system was evaluated in experiments on eight healthy subjects and eight patients with eyelid paralysis. The mean of the absolute error of peak amplitudes occurring in 2 min was 0.81 mm, with the worst error being +1.7 mm. The reproducibility of the mean peak amplitude measured on five consecutive days was within 1 mm. The mean peak amplitudes of both eyes were measured preoperatively and postoperatively for approximately three months for three patients who were operated on to remove vestibular schwannoma. The results demonstrated basic clinical utility of the system.

Three-dimensional imaging of the internal auditory canal in patients with acoustic neuroma.

Three-dimensional imaging of the internal auditory canal (IAC) was carried out in 21 patients with acoustic neuromas using helical computed tomography. The IAC was widened in 20 patients, but no irregularities of the canal walls were seen. In addition, the shape of the enlarged IAC corresponded to that of the tumor on magnetic resonance imaging. The data suggest that widening of the IAC in acoustic neuroma patients is due to enlargement of the tumor. Other mechanisms, for example, tumor invasion or destruction caused by release of a specific mediator from the tumor, are unlikely to explain these findings; however, further investigation is needed.

Relationship between cystic change and rotatory vertigo in patients with acoustic neuroma.

Acoustic neuromas are benign neoplasms that most often arise from the vestibular nerve. Many patients with this tumor experience some degree of vestibular symptoms. However, patients rarely complain of rotatory vertigo. Acoustic neuromas are known to exhibit a cystic appearance in some patients. It was hypothesized that cystic change might be a causative factor for rotatory vertigo. A retrospective study of 178 patients with unilateral acoustic neuroma who underwent surgery in the Department of Otolaryngology at Tokyo Medical and Dental University was carried out. The cystic appearance of the tumors was detected preoperatively by magnetic resonance imaging and confirmed at surgery. The relationship between cystic change of the tumor and presentation with rotatory vertigo was examined. Of the 178 patients studied, only 10 had both cystic change of the tumor and rotatory vertigo, and 120 had neither cystic tumor nor rotatory vertigo. Of the remaining 48 patients, 24 experienced rotatory vertigo with negative findings for cystic tumor and the other 24 had evidence of cystic tumor but no rotatory vertigo. Tumor with cystic change was observed in 34 patients, accounting for 19.1% of all patients studied. Rotatory vertigo was also experienced in 34 patients (19.1%). Of the 34 patients with cystic lesions, 29.4% (10) had rotatory vertigo. The difference in percentage of the two groups did not reach statistical significance. It is suggested that there may be other factors causing rotatory vertigo in patients with acoustic neuromas than cystic change of the tumor.

The arcuate eminence is not a protrusion of the superior semi-circular canal but a trace of sulcus on the temporal lobe.

Thirteen cadavers (26 temporal bones) were examined to show the arcuate eminence, especially its correspondence to the superior semicircular canal and inferior surface of the temporal lobe. Arc-like eminences on the petrous bone were observed in 92 per cent of specimens, however, they did not exactly correspond to the superior semi-circular canal. Some eminences corresponded to sulci of the temporal lobe of which most were traces of the occipitotemporal sulcus. On the other hand, a dull, smooth and even domed eminence existed in nine temporal bones independently of the arc-like eminence. Those eminences corresponded to each superior semi-circular canal in only three out of nine specimens. The arcuate eminence was listed as an important landmark in the middle cranial fossa approach. However, in order to drill out the internal auditory canal safety, surgeons should rely on other landmarks or apply other methods from our data.

Detection of antibody to sialyl-i, a possible antigen in patients with Meniere's disease.

An autoimmune hypothesis for the etiology of Meniere's disease has been proposed. In this study, we focused on gangliosides as potential antigens for autoantibodies in Meniere's disease patients. In an attempt to investigate ganglioside antigens which respond to the serum of patients with Meniere's disease, we analyzed gangliosides of human acoustic neurinomas, and used them as antigens to broadly explore gangliosides that react to serum. All the acoustic neurinoma samples used in the present study showed a similar ganglioside profile on TLC (thin-layer chromatography). For the microscale ganglioside analysis, a newly developed TLC blotting/secondary ion mass spectrometry (SIMS) system together with TLC immunostaining method was employed. Most of the ganglioside bands could be analyzed, and they were identified as GM3, GM2, SPG, GM1a, GD3, S-i (sialyl-i ganglioside) and GD1a. GD1a was the predominant ganglioside and many neolactoseries gangliosides were recognized by immunological analysis. Next, the immune reactivity of serum samples, from patients with Meniere's disease, with the acoustic neurinoma gangliosides was studied by TLC immunostaining. The result showed that five of 11 patients with Meniere's disease and one of eight normal subjects reacted with a specific band, which was identified as S-i by the TLC blotting/SIMS system. The findings of the present study indicate that S-i ganglioside is an autoantigen and possibly involved in the pathogenesis of Meniere's disease.

Electrocochleographic study in patients with vestibular schwannomas and U-shaped audiograms.

To determine the nature of sensorineural hearing loss in the middle-frequency range (U-shaped audiogram), we compared the differences in electrocochleographic findings for 15 ears with vestibular schwannomas and 10 ears without tumours. Short-tone bursts of 0.5, 1, 2, and 4 kHz were used to evoke cochlear microphonics (CM). Ears with tumours had normal or lower CM detection thresholds than ears without tumours. Input-output curves for 1-kHz frequency were normal in 10 ears with tumours and in 1 ear without tumours. These indicate that tumour ears have no or mild cochlear dysfunction. In addition, CM detection thresholds of ears with tumours were lower than audiometric thresholds, particularly at the 1- and 2-kHz region. These findings suggest that the loss seen by audiometry in ears with vestibular schwannomas was from a retrocochlear component.

Cochlear microphonics for hearing preservation in vestibular schwannoma surgery.

OBJECTIVES: To determine whether cochlear function is beneficial in decision-making concerning the selection of hearing preservation surgery for vestibular schwannoma. STUDY DESIGN: Retrospective review of 44 patients undergoing tumor resection with a middle fossa approach. METHODS: Cochlear microphonics in electrocochleography together with tumor size, pure-tone average (PTA), speech discrimination score (SDS), auditory brainstem response (ABR), and compound action potentials were examined. As acoustic stimuli, short tone-bursts with frequencies of 0.5, 1, and 2 kHz were employed to measure cochlear microphonics and a click was used to obtain compound action potentials. We determined detection thresholds of cochlear microphonics and action potentials. RESULTS: The overall rate of preservation of serviceable hearing was 59.1% (26/44). There were significant differences between patients with and without serviceable postoperative hearing in PTA, SDS, finding of ABR, compound action potential detection threshold, and mean cochlear microphonic detection threshold (at 0.5, 1, and 2 kHz). However, tumor size was unrelated to hearing outcome. Serviceable hearing was preserved in 23 (76.7%) of 30 patients, with a mean cochlear microphonic detection threshold of 40 dB nHL or less, suggesting normal or slightly impaired cochlear function. Hearing recovery was recognized in three patients, who also had a mean cochlear microphonic detection threshold of 40 dB nHL or less. Of the three patients, two had lower cochlear microphonic detection thresholds than audiometric thresholds, demonstrating the existence of a retrocochlear component in their hearing loss. CONCLUSIONS: The cochlear microphonic detection threshold predicts not only hearing preservation but also hearing improvement in patients with vestibular schwannomas.

Progressive sensorineural hearing impairment in professional fishery divers.

There have been many reports of a high rate of hearing impairment in divers. A prospective study was performed to determine whether sensorineural hearing acuity in the same divers deteriorated faster than in a normal population as they continued diving. After an observation period of approximately 5 years, audiometric examination was performed on a group of professional fishery divers who had normal hearing or sensorineural hearing loss at the time of initial study. Thirty-three ears of 18 divers were included in statistical analyses. The average hearing deterioration in the divers in 5 years, after elimination of the aging effect, was 6.6 dB (SD 4.5) and was statistically significant. We concluded that the hearing acuity of our subjects deteriorated faster than that of normal Japanese.