[Clinical experiences and postoperative results with partially implantable middle ear implant]

A partially implantable middle ear implant using an ossicular vibrator of a piezoelectric ceramic bimorph has recently been developed in Japan as a new rehabilitative method for hearing. Four patients at the Miyazaki Medical College Hospital were implanted with this device between September 1994 and October 1996. Implantation of the internal component was performed under local anesthesia after confirmation of sufficient sensitivity to the ossicular vibrator in an intraoperative vibratory hearing test. All patients regained socially useful hearing with the middle ear implant without any foreign body reactions or recurrence of otitis media. None of the cases showed any elevations of bone conduction thresholds 2 to 4 years postoperatively. Natural and clear sounds without interference noise and howling due to acoustic feedback were highly satisfactory in all patients. However, the first case, who had an implant in an ear following cholesteatoma surgery using the intact canal wall technique, experienced about a 10dB deterioration of the average hearing level with the implant 2 years after implantation. Gradual deterioration appeared to be caused by the retracted tympanic membrane interfering with the mobility of the ossicular vibrator. The following three cases were implanted in ears previously operated on by radical mastoidectomy, showing stable or improving hearing results with the implant. Closure of the external canal skin at the cartilaginous portion at the time of implantation seemed appropriate to maintain a sufficient middle ear space for the ossicular vibrator to work properly. Our case study confirms that the partially implantable middle ear implant is a safe and useful tool for patients with mixed deafness which cannot be satisfactorily rehabilitated by tympanoplasty and/or a conventional hearing aid.

Expression of the Vax family homeobox genes suggests multiple roles in eye development

BACKGROUND

Homeobox gene products are thought to regulate target genes involved in the regional specification of tissues and organs. Several genes play roles in eye development.

RESULTS

We isolated two new mouse homeobox genes, Vax1 and Vax2, expressed in retina primordium. The two genes share the same gene organization, consisting of three exons with predicted amino acid sequences identical in the homeodomain but diversified in other regions. At 9. 5 days post coitum, both Vax genes were expressed in optic vesicles. At 11.5-14.5 dpc, Vax1 became restricted to the optic stalk, while Vax2 was expressed in the ventral half of the neural retina. Mapping of Vax2 between D6Mit3 and D6Mit8 on chromosome 6 indicated a possible linkage with Emx1.

CONCLUSIONS

The expression patterns of Vax genes suggest separate and specific involvement in eye development. Vax1 may contribute to differentiation of the neuroretina, pigmented epithelium and optic stalk, while Vax2 could function in the establishment of the dorso-ventral axis of the retina and the visual system. The chromosomal location of Vax2 suggests that Vax2-Emx1 and Vax1-Emx2 arose by chromosome duplication of the same ancestral gene.

Prussak's space: chronological development and routes of aeration

Investigation of Prussak's space and its relationship to adjacent spaces is important in elucidating the cause of retraction pocket and cholesteatoma formation in this space. This study was designed to quantitatively characterize the chronological development of Prussak's space and its relationship to adjacent spaces in temporal bones. One-hundred and forty-nine human temporal bone slides (115 normal, 28 with otitis media with effusion, three with retraction pockets and three with attic type cholesteatoma) including specimens ranging from fetal to adult bones were studied. Prussak's space was formed and sufficient aeration routes established by 4 years of age in normal temporal bones. In temporal bones with otitis media with effusion, however, the growth of Prussak's space was suppressed and few routes for aeration established until 10 years of age. In normal temporal bones, Prussak's space developed with aeration routes sufficient to avert the negative pressure which can result in retraction pocket formation in the pars flaccida of the tympanic membrane.

Utilization of nickel-titanium shape memory alloy for stapes prosthesis

A new type of stapes prosthesis made of nickel-titanium shape memory alloy wire was developed and its biocompatibility was examined in 24 ears of 12 cats. The prosthesis was implanted at the long crus of the incus. The incus was examined 27-355 days after operation. In 23 ears, the prosthesis was found macroscopically well implanted at the aimed position. In one ear the prosthesis was found to be dislocated and in another the prosthesis was slightly loosened. The incudes were removed and five specimens were prepared for scanning electron microscopy and the other specimens were observed under light microscopy. Histological studies revealed severe bone resorption of the long crus in the dislocated case and moderate bone resorption in the slightly loosened case. These bone resorptions were found to be caused by the inadvertent removal of the mucosal membrane during the implant operations. In seven ears under a light microscope and in one ear under a scanning electron microscope, slight bone resorption as bone erosion was seen at the contact area of the prosthesis. This bone resorption was induced by the mechanical pressure of the prosthesis and was not progressive due to fading of the pressure of the prosthesis. With the exception of pressure induced bone erosions, there was no progressive bone resorption which was prosthesis induced. The biocompatibility of the nickel-titanium alloy stapes prosthesis with the long crus of the incus was proved. The prosthesis should be implanted loosely at the long crus of the incus without removal of the mucosal membrane.

Iodine-123 metaiodobenzylguanidine myocardial imaging in patients with pulmonary hypertension

Iodine-123-metaiodobenzylguanidine [123I-MIBG] has been used to evaluate the cardiac sympathetic nervous system. We evaluated the effect of pulmonary hypertension on the sympathetic neuronal function of the left ventricle in patients with pulmonary hypertension. We studied 20 patients with either chronic lung disease or pulmonary vascular disease. The patients were divided into a pulmonary hypertensive group and a control group. Single photon emission tomography was performed in the resting state 15 min and 4 h after administration of 123I-MIBG. Regions of interest (ROI) were set in the left ventricular (LV) free wall, the interventricular septum (IVS) and outside the LV free wall on short-axis images. The washout rate and the ROI/LV uptake ratio were calculated in each ROI. The IVS:LV uptake ratio was significantly lower in the pulmonary hypertensive group than in the control group. Our results suggest that left heart sympathetic neuronal dysfunction initially occurs in the IVS before it involves the LV free wall subsequently.

Iodine-123-metaiodobenzylguanidine myocardial imaging in patients with right ventricular pressure overload

Iodine-123-metaiodobenzylguanidine ([123I]MIBG) has been used to evaluate the cardiac sympathetic nervous system, particularly that of the left heart. To clarify whether the right ventricular (RV) sympathetic neuronal function could be evaluated by [123I]MIBG myocardial imaging, we applied the technique in patients with pulmonary hypertension that was associated with either chronic pulmonary diseases or pulmonary vascular diseases.

METHODS

All patients underwent right heart catheterization, and right heart hemodynamics were determined during a clinically stable state. SPECT was performed in the resting state 15 min (early imaging) and 4 hr (delayed imaging) postadministration of [123I]MIBG. Seven regions of interest (ROI) were selected on the delayed short-axis images on the RV free wall, left ventricular (LV) free wall and interventricular septum (IVS). We calculated the IVS-to-LV uptake ratio from the scintillation counts of the ROI. Thallium-201 myocardial imaging was also performed within 1 wk after [123I]MIBG imaging.

RESULTS

Images obtained with these techniques were analyzed for the RV-to-LV uptake ratio. The IVS-to-LV ratio on [123I]MIBG correlated negatively and significantly with the mean pulmonary arterial pressure (PAm). The RV-to-LV uptake ratio on 201Tl images correlated significantly with PAm.

CONCLUSION

Our results suggest that the uptake ratio of [123I]MIBG in the IVS is a useful index for evaluating the severity of pulmonary hypertension, and that chronic RV pressure overload contributes to disturbances of the cardiac sympathetic nervous system.

[Tympanic electrocochleography with disposable electrode]

Extratympanic recording of electrocochleography (ECochG) has played an important role in the differential diagnosis of inner ear diseases. We used a special electrode, which was wrapped in a cotton ball at the tip and covered with a silicon sheath over the entire length, and recorded ECochG from the tympanic membrane (tympanic ECochG). Our method was found to be more convenient and less traumatic than recording with an ear canal electrode. Tympanic ECochG records from 10 normal volunteers showed no influence of iontophoretic anesthesia on the tympanic membrane. The effects on the conductive hearing mechanism were negligible. The input-output curve of the action potential (AP) by click stimuli was fairly stable and comparable to that obtained with transtympanic recording. We performed tympanic ECochG in patients with Meniere's disease or other sensory hearing loss, and compared the amplitude ratios of the summating potential (SP) and AP (SP/AP ratio) with those in normal hearing subjects. The SP/AP ratios in patients with Meniere's disease were significantly increased, an observation consistent with the results of other studies. The SP/AP ratio was also elevated in patients with autoimmune sensory hearing loss or perilymphatic fistula. Based on the results of the present study, we speculate that it is possible to diagnose an inner ear disorder by comparing the tympanic ECochG findings with not only records from normal subjects, but also the contralateral record of tympanic ECochG from the same subject. We conclude that tympanic ECochG using disposable electrodes can provide useful information on inner ear function, because of its convenience, non invasiveness and safety in clinical use. We found tympanic ECochG to be useful in the glycerol dehydration test and for monitoring inner ear function during acoustic neurinoma surgery.

Cochlear implantation in an intralabyrinthine acoustic neuroma patient after resection of an intracanalicular tumour

This case study describes a therapeutic strategy using a cochlear implant for a bilateral acoustic neuroma deafened patient. The cochlear nerve had previously been sacrificed on one side during tumour removal, but on the remaining side a functioning cochlear nerve was assessed by electric promontory stimulation in spite of a neuroma extending into the vestibular labyrinth. The patient was successfully stimulated with a Nucleus 22-channel implant after removal of the intracanalicular portion of the neuroma via a middle fossa approach.

[Middle ear cholesteatoma caused by cannonball foreign bodies impacted in the bony eustachian tube: a case report]

We present a 76-year-old male patient with adhesive-type cholesteatoma and with metal foreign bodies which were shown to be located in the bony eustachian tube by computed tomography. He sustained a burn injury of the left tympanic membrane when he was struck by a bomb 52 years ago, during World War II. The cannonball fragments that entered the tympanic cavity were apparently transported to and stuck in the eustachian tube isthmus by mucociliary action after spontaneous closure of the tympanic membrane perforation. Persistent tubal obstruction due to the impacted foreign bodies and surrounding granulation tissue seems to have caused chronic adhesive otitis, leading to cholesteatoma which developed in the attic and mastoid antrum. No foreign bodies became visible after cholesteatoma removal by an intact canal wall technique in conjunction with anterior tympanotomy for wide exposure of the supratubal recess and the tympanic osteum of the eustachian tube. Therefore, anterior tympanotomy was further extended anteriorly to open the enlarged bony eustachian tube, allowing visualization and safe removal of two cannonball-fragments firmly impacted within it. We call this surgical approach to the bony eustachian tube "extended anterior tympanotomy". The transmastoidal accessibility of the bony eustachian tube produced by this technique should be assessed by preoperative computed tomography.

Tl-201 SPECT in Kimura's disease involving the parotid glands and cervical nodes

Kimura's disease is a chronic inflammatory condition producing subcutaneous tumor-like nodules, mainly in the head and neck region. Most patients have involvement of regional lymph nodes and major salivary glands. The authors present two cases of Kimura's disease with parotid gland and postauricular lymph node involvement. With Tl-201 SPECT, elevated uptake was noted on early and delayed images. Kimura's disease should be included in the differential diagnosis when increased Tl-201 uptake in head and neck mass lesions is noted.

Noninvasive assessment of right heart function by 81mKr equilibrium radionuclide ventriculography in chronic pulmonary diseases

Noninvasive multigated equilibrium radionuclide ventriculography with krypton-81m (81mKr) was used to assess right heart relaxation in patients with chronic pulmonary diseases (CPD). The subjects consisted of 30 patients with CPD and 8 patients free of cardiopulmonary diseases admitted to our department. A region of interest (ROI) was selected on both the right atrium (RA) and right ventricle (RV). A time activity curve was obtained for each ROI. As a diastolic index of the right heart performance, the right atrial early emptying rate (RAER) was obtained from the right atrial time activity curve, while the right ventricular rapid filling rate (RVRFR) was obtained from the right ventricular time activity curve. The mean RAER was significantly lower in CPD patients compared with the control (CPD, 9.5 +/- 4.5; control, 16 +/- 3.4%/100 ms). Similarly, the mean RVRFR was significantly lower in CPD patients compared with the control (CPD, 27.3 +/- 9.9; control, 34 +/- 8.5%/100 ms). A strong negative correlation was noted between the mean pulmonary arterial pressure (mPAP) and RAER (r = -0.77; p < 0.001) and between the mPAP and the RVRFR (r = -0.63; p < 0.001). Our results suggest that RAER and RVRFR measured by 81mKr are clinically useful in the noninvasive assessment of right heart relaxation in patients with CPD.

Developmental anatomy of the supratubal recess in temporal bones from fetuses and children

The supratubal recess (STR), located superior to the bony eustachian tube and anterior to the attic and often the site of disease, is clearly separated from the attic by the presence of a bony partition. Its anatomic development in childhood, however, remains nuclear. We reviewed serial horizontal sections of fetal and children's temporal bones from the collection of the Otopathology Laboratory, University of Minnesota. Apparently, upward expansion of the bony eustachian tube begins at a late fetal stage and continues throughout childhood, thus forming the STR. Our finding that the STR had already developed in temporal bones without pneumatization of petrous bone suggests that its formation is independent of the air-cell system. Absorption of mesenchymal tissue in the STR tends to be slower than elsewhere in the temporal bone. Surrounded solely by petrous bone, the STR seems, both developmentally and anatomically, a distinctive compartment of the middle ear.

[Hearing results after anterior tympanotomy in cholesteatoma surgery]

Between 1987 and 1993, 71 ears of attic type cholesteatoma and 20 ears of adhesive type were operated on using the intact canal wall technique combined with anterior tympanotomy. Pre- and postoperative pure tone hearing after the surgery were analyzed, especially to determine whether anterior tympanotomy is harmful to the inner ear. Mean values of 500, 1000 and 2000Hz of air conduction threshold immediately, before and about 1 year after the operation were compared. In attic cholesteatoma, type 1, type 3, and type 4 of ossiculoplasty revealed significant improvement of 8.4dB, 9.3dB, and 8.0dB respectively. In adhesive cholesteatoma, results obtained were 8.4dB, 0.8dB, and -3.0dB. Differences between pre- and postoperative bone conduction threshold at 4000Hz were 1.5dB in type 1, 1.3dB in type 3, and 5.0dB in type 4 in attic cholesteatoma. Those in adhesive cholesteatoma were -2.5dB, -0.2dB, and -10.0dB respectively. From the results obtained, we concluded that (1) our results were satisfactory with regards to hearing ability following all types of ossiculoplasty in attic cholesteatoma and in type 1 in adhesive cholesteatoma, (2) anterior tympanotomy itself is not a harmful procedure to the inner ear in both types of cholesteatoma, (3) an increase in bone threshold in adhesive cholesteatoma is due to the surgical procedure at the stapes and/or the oval window.

Development of endocochlear potential and its negative component in mouse cochlea

The chronological developmental processes of endocochlear potential (EP) and negative endocochlear potential (-EP) were investigated as a function of age from birth in the basal and second cochlear turns in normal ICR-strain mice. The EP of the basal turn developed between 5 and 17 days after birth (DAB). The -EP of the basal turn attained to its mature level on 11 DAB and it increased its absolute value further between 12 and 16 DAB and then, recovered to its mature level again on 20 DAB. The developmental processes of EP and -EP of the second turn followed similar courses to those of the basal turn although they were several millivolts different on each day in detail. The results suggest that the developmental processes of the +EP and the -EP are different. The time of reaching minimum -EP during anoxia were measured and the rate of EP decline were calculated on each animal. The rate of EP decline increased rapidly on 10 DAB, almost coinciding the day which EP began to increase abruptly. Although the rate of EP decline is influenced by several processes, this result showed one of the possibility that the sensitivity of the stria vascularis to hypoxia may develop parallel to the development of the EP.

[Postoperative MRI findings after cholesteatoma surgery]

This study was designed to show MRI findings of postoperative middle ear pathologies and to discuss the usefulness of Gadolinium-enhanced MRI in evaluating the postoperative state of cholesteatoma. Thirty-eight ears which underwent intact canal wall tympanoplasty for cholesteatoma were examined. Recurrent cholesteatoma was detected as an iso-intensity area on T1-weighted images with negative enhancement. Notably, residual cholesteatoma were generally depicted as a round iso-intensity area with negative enhancement. Residual cholesteatoma less than 5mm in diameter were, however, not generally detectable with our MRI scanner. Granulation tissue can be separated from cholesteatoma as an area with positive enhancement. Cholesterol granuloma shows a characteristic high signal pattern on both T1 and T2-weighted images. Hypovascular fibrous tissue and fluid collection may be depicted as a pattern similar to that of cholesteatoma. However, the signal is usually more homogeneous than that of cholesteatoma. We conclude that Gadolinium-enhanced MRI is useful for detecting postoperative cholesteatoma and avoiding unnecessary second-look operations after cholesteatoma surgery, by the canal-up procedure.

Effects of experimental round window membrane laceration on the free amino acid profile of perilymph

To evaluate biochemical changes of inner ear fluid following perilymphatic fistula (PLF), free amino acid (FAA) profiles of perilymph in experimental PLF were determined using high performance liquid chromatography (HPLC). Thirty-five guinea pigs were anesthetized and prepared as PLF models by perforating the round window membrane (RWM) of the left ear. Right ears served as controls. Samples (2 microliters) were aspirated from scala tympani through a RWM perforation. Animals were divided into two groups according to time of sampling following PLF induction: 2-week group (n = 17) and 4-week group (n = 18). Compound action potential (CAP) evoked by 1, 2, 4 and 8 kHz tone bursts were measured using a round window electrode from the left ear before PLF induction and from both ears before final sampling. RWM perforations were completely closed at the time of the final sampling in 8 of 17 animals from the 2-week group, and 15 of 18 animals from the 4-week group. In comparison with that in control ears, concentrations of FAA throughout all profiles was dramatically elevated in the PLF ears with a healed RWM perforation. Most PLF ears with persistent RWM perforation showed minimal differences between 2-week and 4-week groups. No remarkable CAP threshold changes were found at any frequencies tested following PLF induction in both the 2-week and 4-week groups. The unchanged 8 kHz threshold suggests that FAA concentration increases only at the basal end of the cochlea. FAAs accumulate within the basal end of scala tympani in ears with a healed RWM.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasminogen activators in tissue extract of aural cholesteatoma

Using a biochemical technique, the authors characterized and identified the plasminogen activator (PA) derived from tissue extracts of six aural cholesteatomas. The results of fibrin zymography indicated that the tissue extracts of two cholesteatomas demonstrated two lytic zones on fibrin-agarose plates. One of the lytic zones was at about 72 kd, while the other zone was at about 64 kd. Using various goat immunoglobulin G (IgG)-containing antibodies (anti-human uterine tissue type PA (t-PA), anti-human low-molecular-weight (LMW) urokinase, and nonspecific goat IgG) and plasminogen-free fibrin-agarose plates, we confirmed that the cholesteatoma tissue extracts contained 72 kd t-PA and 64 kd urokinase type PA (u-PA). Furthermore, we measured the t-PA and u-PA activities in the tissue extracts selectively by parabolic rate assay. In order to estimate the PA activity, we developed optimal conditions for this assay. The specific t-PA activity ranged from 0.03 to 0.43 mIU/micrograms-protein and the specific u-PA activity ranged from 0 to 0.35 mIU/microgram-protein. The highest percentage of u-PA with respect to the total PA activity was 44.9%. However, in four of the six cases, we failed to detect u-PA activity. In the present study, we thus clarified the presence of PAs in tissue extracts of aural cholesteatomas. Furthermore, we confirmed that measureable u-PA occurred in some tissue extracts. We anticipate that the u-PA in inflammatory tissues plays an important role in the degradation of the extracellular matrix via the formation of plasmin and collagenases.

Anionic sites on Reissner's membrane, stria vascularis, and spiral prominence

We demonstrated anionic sites on the lateral wall of cochlear duct and Reissner's membrane (RM) of ICR mice by Lowicryl K4M resin post-embedding and poly-L-lysine-colloidal gold conjugate (PL-CG) as a polycationic probe. The basement membrane and endolymphatic cell surface of RM were labeled with PL-CG pH 2.5 and pH 1.0. However, the perilymphatic cell surface was not labeled. PL-CG pH 2.5 and pH 1.0 strongly labeled the endolymphatic surface of the spiral prominence epithelium (SP), whereas the endolymphatic surface of the marginal cell (MC) in the stria vascularis was not labeled. Pre-digestion with several glycosidases eliminated PL-CG labeling. Our result suggests that an anionic charge located on the basement membrane of RM is largely due to the presence of heparan sulfate, chondroitin sulfate, and hyaluronic acid. An anionic charge on the endolymphatic cell surface of RM was mainly dependent on the presence of heparan sulfate. An anionic charge on the SP epithelium was caused to a substantial degree by chondroitin sulfate. We obtained histochemical evidence that the glycoconjugate content of the MC surface was quite different from that of the endolymphatic cell surface of RM and SP. We also identified RM-MC and SP-MC junctions at the ends of the stria vascularis between the marginal cells and the other endolymphatic epithelial cells of the cochlear duct.

Measurement of intracellular free Ca2+ concentration in guinea pig spiral ganglion cells

Intracellular free Ca2+ concentration ([Ca2+]i) in spiral ganglion cells (SGC) of guinea pig was measured using the fura-2 fluorescence method. Application of high-K+ external solution increased [Ca2+]i. [Ca2+]i elevation was suppressed by either depletion of external Ca2+ or application of the dihydropyridine Ca2+ channel antagonist, nicardipine. One of the putative hair cell afferent nerve neurotransmitters, L-glutamate (Glu), induced [Ca2+]i elevation in SGC. Pharmacological studies suggested that the Glu receptor may be a non-NMDA subtype. Glu-induced response was suppressed by either depletion of external Ca2+ or application of nicardipine, indicating that Glu-induced [Ca2+]i elevation is mainly carried out by the voltage-dependent Ca2+ channel in SGC.

Anionic sites in blood capillaries of the mouse cochlear duct

The blood-cochlear barrier, which consists of the molecular size and ionic charge barriers, is known to play an important role in production and absorption of inner ear fluids. In this study, we employed poly-L-lysine colloidal gold conjugates (PL-CG) in combination with Lowicryl K4M resin to demonstrate anionic sites in blood capillaries of the cochlear duct. Male ICR mice weighing 30-40 g with a positive Preyer's reflex were used. The basement membranes of blood capillaries of the stria vascularis and the spiral ligament were successfully labeled with PL-CG pH 2.5. The luminal surface of capillaries in the stria vascularis and the spiral ligament intensely reacted with PL-CG pH 2.5. However, PL-CG pH 1.0 stained only the basement membrane of the spiral ligament. Predigestion with several glycosidases nearly eliminated PL-CG labeling. Anionic charge located on the luminal surface of the endothelial cell was mainly caused by the presence of sialic acid. On the contrary, anionic charge of the basement membrane was caused in a substantial degree by chondroitin and heparan sulfate-rich glycosaminoglycans. We obtained histochemical evidence that blood capillaries of the stria vascularis differ from those of the spiral ligament.

Effects of arterial occlusion on endocochlear DC potential and cochlear blood flow in guinea pigs

The present study was undertaken to investigate the role of collateral arteries in cochlear circulation by examining the effect of occlusion of branches of the basilar artery on endocochlear DC potential (EP) and cochlear blood flow (CBF). EP and CBF were measured at the basal turn of the cochlea during microclamp occlusion of the basilar artery, its branches and the posterior inferior cerebellar artery (PICA). CBF was measured with a laser Doppler flowmeter. Systemic blood pressure (SBP) increased at occlusion of the basilar artery, but was not influenced by any occlusion of its branches. Changes of EP and CBF at occlusion of the basilar artery were classified into two types: recovery type and non-recovery type. Thirty-five guinea pigs were classified into three groups according to the number of branches of the basilar artery: Group A with one branch in 10 animals (29%), Group B with two branches in 20 animals (57%), and group C with three branches in 5 animals (14%). From the results obtained at successive occlusions of branches of the basilar artery and PICA, it is clear that the anterior inferior cerebellar artery (AICA) supplies blood to the cochlea more or less in all animals, although the reduction of the blood volume by its occlusion is not enough to decrease EP in some animals. When vascular dysfunction occurs in AICA of such animals, other branches of the basilar artery and/or PICA will play an important role to maintain cochlear circulation.

Magnetic resonance imaging in patients with sudden deafness

Although many theories on the etiology of sudden deafness have been proposed, the main pathological focus remains uncertain. In this study, MR examinations were performed on patients with unilateral sudden deafness to study the relationship between MRI findings and response to treatments, i.e. amidotrizoate, steroid, or both. In 7 out of 30 cases, the cochlea and/or the vestibule showed higher signal intensity on proton density and T2-weighted images on the diseased side (MRI positive cases). These findings suggest changes in the chemical composition of the perilymph and/or the endolymph, since proton density and T2-weighted images reflect water content. It appears that MRI positive sudden deafness is more difficult to cure even with the use of amidotrizoate or steroid than MRI negative sudden deafness. Amidotrizoate seems to be more effective in MRI negative sudden deafness. MRI would help us to further classify the etiology of sudden deafness.

Effects of contrast media on the stria vascularis

The effects of contrast media on the stria vascularis were electron microscopically studied in mice after intravenous injection of amidotrizoate, iopamidol or ioxaglic acid at 10 or 20 ml/kg body weight. In furosemide-load groups, contrast media were injected via the tail vein at 10 ml/kg with preadministration of furosemide at 20 mg/kg body weight. In both groups, the stria vascularis was prepared for study 10 min after the injection of contrast media. No morphological changes could be found after administration of 10 ml/kg injection of any of the three contrast media. However, administration of 20 ml/kg of amidotrizoate caused a high degree of intercellular dilatation between marginal and intermediate cells. Iopamidol caused a slight degree of dilatation, and ioxaglic acid caused no change. In the furosemide-load groups, amidotrizoate induced severer effects than iopamidol while ioxaglic acid induced no effect. From these results it was concluded that contrast media affect the stria vascularis parallel with osmolality, although some ionic effect of amidotrizoate should be considered when it is used in combination with furosemide.

Histochemical demonstration of mucin in lymphatic vessels of human middle ear cholesteatoma

We investigated the possible existence of mucin in lymphatic vessels in cholesteatoma perimatrix using the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method. Histochemical staining distinguished two types of lymphatic vessels, one of which contained PA-TCH-SP reacting substance showing a loose mesh-like appearance. Connective tissue was edematous around this vessel and was infiltrated by abundant round cells. The second type of lymphatic vessel did not contain PA-TCH-SP reacting substance and few round cells were seen infiltrating tissue around this vessel. Gland-like structures of mucous epithelium in the perimatrix were heavily stained by the PA-TCH-SP method. Secretory granules of the mucous epithelium and its luminal content had a loose mesh-like appearance. Since contents of the gland-like structures may leak through the chinks of epithelial cells into subepidermal connective tissues, the resultant inflow of mucin into the lymphatic vessels may then cause inflammation of the cholesteatoma perimatrix.

[A case of superficial siderosis of the central nervous system with total deafness]

Superficial siderosis of the central nervous system (SSCN) in a disease characterized by chronic deposition of hemosiderin in the leptomeninges, subpial tissue, spinal cord, and cranial nerves. Previously the diagnosis of SSCN could only be made at autopsy or during a neurosurgical procedure. Now, however, a diagnosis of SSCN can be made non-invasively by magnetic resonance imaging (MRI). We present the case of a 50-year-old male with SSCN accompanied by bilateral sensorineural hearing loss which gradually progressed to total deafness over a seven year period. This patient also had associated bilateral caloric weakness with episodes of severe recurrent headaches over the two preceding years. The deafness and gait disturbance, which were his chief complaints, were followed by other neurological manifestations including pyramidal tract signs, anosmia, and ageusia. High-field MRI on T-2 weighted images of the CNS showed diffuse marginal hypointensity of the cerebrum, brain stem, and cerebellum. Atrophy of the cerebellum and brain stem was also apparent. Low signal intensity along the proximal segment of the acoustic nerve and the facial nerve was noted from the cistern to the internal auditory canal. Neither bilateral transtympanic promontory nor round window electrical stimulation elicited any sound sensation. In this case it was thought that the acoustic nerve alone or both the acoustic nerve and the cochlea were affected by this disease. Consequently, cochlear implantation was not indicated. The source of bleeding into the subarachnoid space could not be detected despite thorough examination. This diagnosis will be made only by physicians who are aware of this rare entity and have knowledge of the characteristic clinical pathology.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical application of a newly developed surveying system for designing and fabricating removable partial dentures

In this paper, some problems in commercially available surveying systems were discussed, and a clinical technique for designing and fabricating clasps by using an improved 'Digital Surveyor' and a computer system were presented. This system has the advantages as follows: (1) morphological factors on abutment teeth could be measured and evaluated using the improved 'Digital Surveyor' and its accessories set, (2) clasps providing with proper mechanical properties according to various conditions in the mouth could be designed and fabricated precisely and easily. It became clear that conventional surveying methods involved empirical rules should be re-examined and replaced by the more rational surveying method like this system.

Histopathology of eighth cranial nerve of mass stranded dolphins at Goto Islands, Japan

We examined four dolphins (Grampus griseus) of 582 mass-stranded. Almost no contents were found in the alimentary canal. Nasitrema gondo and Crassicauda grampicola were found in the tympanic cavity. Severe degeneration of the eighth cranial nerve was observed microscopically in all animals and an egg of Nasitrema was found in a tissue crevice of the nerve. We propose that the nerves were damaged directly by Nasitrema.

Venous drainage through the internal auditory meatus of the guinea pig cochlea

The angioarchitecture of the guinea pig cochlea has been investigated closely using light microscopy and resin injections. However, detailed information concerning the vasculature of the modiolus is still unavailable, and even the existence of venous drainage through the internal auditory meatus is not agreed upon. In the present investigation, vascular casts of guinea pig temporal bones were studied using scanning electron microscopy. A vessel, formed by the confluence of the vascular network on the modiolar wall and having a spiral course into the internal auditory meatus was found in the modiolus of the basal turn. The vessel had a venous pattern on its cast surface and, after existing from the internal auditory meatus, drained finally into the dural sinus. These scanning electron microscopic findings were confirmable by serial sections of the dural veins in the internal auditory meatus and the modiolus. The vessel found may correspond to the so-called internal auditory vein, but it would be more appropriate to call it "the vein of the internal auditory meatus," since it appears to be an independent route of venous drainage from the modiolus.

Myringoplasty in children

Our 11 years of experience of myringoplasty in 87 children aged 3 to 14 years were retrospectively studied. The children were followed up over a period of 3 years. Children in the 3-to-12-year-old age group had a success rate of 57.7%. Graft-take rate was 100% in children operated on at the age of 13 and 14 years. Revision surgery was needed in 33 ears, and ultimate success was achieved in 88.9%. Within the same period, 38 ears were conservatively treated and 20 perforations of them were spontaneously closed. The state of the opposite ear and the perforation size were not a decisive factor in the results of myringoplasty. Children between 7 and 10 years old with small mastoid pneumatization had a statistically lower graft-take rate. We concluded that myringoplasty is warranted for children 13 years of age and older or children aged 7 to 12 years with large mastoid pneumatization.

[Phinocerebral mucormycosis--report of a case]

Rhinocerebral mucormycosis is a rare and fatal deep fungus infection occurring in debilitated patients. Its reports have been recently increased because of the increase of such conditions as uncontrolled diabetics, leukemia, and cancer. A 60-year-old male suffering from continuous headache and fever was diagnosed as meningitis, and repeated culture of cerebrospinal fluid was negative. Antibiotic therapy was ineffective. CT scan revealed brain abscess in the right frontal lobe and bone defect over the right posterior ethmoidal sinuses. Both maxillary and ethmoidal sinuses were operated on 38 years ago. The patient was suspected to have rhinologic brain abscess. We intended to remove the source of infection in the right posterior ethmoidal sinuses beneath the base of the skull and to repair the defect of dura mater. The operation was tried on the 6th hospital day. There was a cyst in the posterior ethmoidal sinuses and an intact denuded dura mater over the cyst. The causative organism was not detected by smear test, bacteriological and fungal culture. He relapsed into lethargy, and died on the 21st hospital day due to the vast cerebral infarction. Autopsy revealed rhinocerebral mucormycosis. The literature on this disease was also reviewed and discussed.

Long term effects of intense sound on endocochlear DC potential

Changes in endocochlear DC potential (EP) after single and repeated intense sound exposure and negative EP induced by anoxia were observed in guinea pigs with passage of time. The intense sound used was a pure tone of 2 kHz at 145 dB SPL for 4 h. The single exposure group was divided into 8 groups of 1, 2, 5, 10, 20, 30, 45, and 60 days after sound exposure. The EP level dropped remarkably in the 1 and 2 day groups and recovered almost completely in the remaining groups. In the 60 day group, EP was significantly higher than that of the control group. The double exposure group consisted of 1, 2, 5, 10, 20, and 30 day groups after the second exposure at an interval of 30 to 40 days. EP in the 1, 2, 5, and 10 day groups was significantly lower than the control level and in the 20 and 30 day groups was almost the same as that of the controls. In all groups after single and double sound exposure, disappearance of negative EP during anoxia was observed. The EP decrease after sound exposure was apparently caused by a mechanical but reversible lesion at the stria vascularis. The disappearance of negative EP after sound exposure was thought to be induced by an irreversible lesion of Corti's organ.

Long-term effects of intense sound on hair cells of Corti's organ and endocochlear DC potential

Cochleograms of guinea pig ears were made 30-40 days after exposure to intense pure tones of 300 Hz, 500 Hz, 2 kHz, or 4 kHz at 130-150 dB SPL for 4-24 h. At 4 kHz, hair cells in the basal turn disappeared totally, in the second turn moderately, and were relatively undamaged in the third and apical turns. At 500 Hz, hair cells in the second and third turns were almost completely injured and at 300 Hz moderately damaged in the third and apical turns although the basal turn remained undamaged. At 2 kHz for 9 h, hair cells were almost completely injured in all turns. Negative endocochlear DC potential (negative EP) induced by furosemide was observed in the basal turn but not in the third turn of animals exposed to 300 Hz. Contrarily, negative EP was observed in the third turn but not in the basal turn of animals exposed to 4 kHz. We conclude that the hair cells of Corti's organ play an essential role in the production of negative EP.

[Application of occlusal splint for the patient with temporomandibular joint dysfunction. An application of silane coupling treatment: a case report]

The bite plane therapy has been one of the most useful treatment methods for patients with temporomandibular joint (TMJ) dysfunction. But the bite plane usually causes esthetic and articulation disturbances and it is occasionally difficult to use during mastication. The authors have fabricated a new type of bite plane, named occlusal splints, which covers each side of the premolars and molars. The occlusal splint was constructed by a hard-resin for the occlusal part and cast clasps for the retentive part and these parts were adhered after a pre-treatment of metal by the use of a silane coupling agent (Silicoater system). The patient was a 35 year-old man, with a chief complaint of left side reciprocal TMJ clicking. The anterior repositioning type of bite plane was applied for the treatment with the diagnosis of anterior disk displacement with reduction. But he complained of esthetic and articulation disturbances especially during working and eating. After four months we fabricated an occlusal splint that can be used for a long period of time. The patient was satisfied to use this occlusal splint and no symptoms of TMJ dysfunction were found with this appliance. It is suggested that the occlusal splint consisting of a hard-resin and cast clasps is a useful appliance especially for the purpose of use during working and eating, and for evaluating the properness of mandibular position.

The ultrastructure of lymphatic vessels in the human middle ear with cholesteatoma

Lymphatic vessels were few in the edematous portion of the cholesteatoma perimatrix of the human middle ear. But the lymphatic vessels contained mucus and consisted of degenerated endothelial cells. Edema of the perimatrix was considered to be caused by the degeneration of lymphatic vessels. Normal lymphatic vessels were found in the fibrous perimatrix, while macrophages infiltrated and phagocytosed cell debris. In addition, regenerating blood vessels were observed. Degeneration of connective tissue due to lymphatic edema and its repair were both present in the perimatrix. The degeneration of perimatrix was hypothesized to be caused by confined mucous epithelium behind the cholesteatoma matrix.

The effects of anesthesia of the tympanic membrane on eustachian tube function

In our previous histological studies of the tympanic membrane, we reported the presence of encapsulated nerve corpuscles that are capable of detecting middle ear pressure. Based on these findings, the relation between sensory receptors in the tympanic membrane and tubal function was examined in a clinical study. Tubal function was tested during Valsalva maneuvers and its active equilibration. Function was recorded as a change of the static compliance of the tympanic membrane on an otoadmittance meter. To paralyze the sensory receptors in the tympanic membrane, iontophoresis was used to induce anesthesia of the drum. Forty ears of 20 subjects were tested. All ears were able to equalize positive middle ear pressure without or with a single swallowing. After anesthesia, 13 ears needed more than two swallows and 4 ears failed to equalize middle ear pressure in spite of repeated swallowings. As eustachian tube function changed following anesthesia of the tympanic membranes, a neural connection between sensory receptors in the tympanic membrane and tubal muscles is suggested.

[Effect of bite plane on electromyographic activity of masticatory muscles. 1. Muscle activity during tapping movement]

The purpose of this study is to examine the influence of the insertion of bite plane on masticatory muscle activity during tapping movement, and find out useful parameters for examination and diagnosis of stomatognathic dysfunction. The subjects in this study were twenty normal subjects with intact dentition and no signs of mandibular dysfunction as the control group, and twelve subjects with unilateral temporomandibular joint pain during jaw opening or closing movement as the patient group. Electromyographic activity in the bilateral anterior temporal and masseter muscles and mandibular movement using the Mandibular Kinesiograph were recorded simultaneously during tapping movement. The usefulness of the 61 items used in this study was evaluated. The results were summarized as follows: 1. In the patient group, a significant correlation between the jaw opening degree during tapping movement and the maximal jaw opening one without pain was recognized. 2. The total muscle activity in the patient group decreased significantly by the insertion of the bite plane. 3. Many subjects of the patient group showed a significant difference between the right and left activity of each muscle. 4. A significant difference between the two groups was found in the duration of muscle activity before and after Silent period, those coefficients of variation and the difference between those durations of the right and left muscle activity. This study suggests that the above factors are very useful parameters for examination and diagnosis of temporomandibular joint dysfunction.

Pathogenesis of cholesteatoma based on clinical results of anterior tympanotomy

A new conception of the pathogenesis of cholesteatoma is proposed based on clinical results of anterior tympanotomy, a procedure developed in order to prevent recurrence of cholesteatoma following retraction pocket formation after canal-up operation. In the cholesteatomatous ear, there is always a long, thick bony septum between the epitympanum and the supratubal recess. This septum is called the anterior attic bony plate, forming the tympanic diaphragm together with the tensor tympani mucosal fold. In anterior tympanotomy, this bony plate is removed finishing intact canal wall mastoidectomy, making a new ventilating route to the eustachian tube. With this technique, the rate of recurrence was reduced from 17 to 5%. Based on these results it is proposed that the real pathogenesis of cholesteatoma is not tubal dysfunction, but the osseous tympanic diaphragm.