Masafumi Nakagawa

Equivalent dipoles for middle latency auditory evoked potentials using the dipole tracing method

During the last decade, new dipole localization techniques have prompted the search for the neuronal generators of evoked potentials. In this study we have reported the equivalent dipoles for the middle latency auditory evoked potentials (MAEPs) by the mean of these localization using the dipole tracing method. MAEPs that were recorded from 19 normal human subjects attending to random binaural clicks were analyzed using the dipole tracing method. Equivalent dipoles (EDs) were found, using both the single-dipole model and the two-dipole model, for components occurring from 0 to 60 ms after stimulus onset. The dipole analysis accounted for the real head geometry based on three-dimensional digitization of measured head shape, and the results were experimentally correlated to those of magnetic resonance imaging to increase the accuracy of ED localization. For components in the first 15 ms latency (P0 and Na), neither model provided EDs with reproducible high dipolality. Na was particularly difficult to analyze, as this component was often contaminated by myogenic potentials. The results provided by the two-dipole model for the Pa component (20-30 ms) showed three variations: in three subjects, one ED was located in each supratemporal cortex; in another three, one ED was located in the right temporal cortex and the other in the midbrain; and in the remaining thirteen subjects, both EDs were in the midbrain. The single-dipole model and the two-dipole model both found EDs in the midbrain for Nb. Further study is necessary to determine the cause or causes of the variety in our results. And it is also necessary to try the study using unilateral ear stimulation with/without contralateral masking noise for understanding the mechanism of the binaural interaction.

Comparisons of auditory cortical imaging for the various dichotic listening

Abstract Aim : The study was designed to estimate the auditory laterality of the human brain that was based on the dichotic listening (DL) technique. Non-invasive detection to know the ear advantage is useful for the hearing aid fitting for mono-aural wearing. Subject : Ten normal hearing adult volunteers were employed in this study. Methods : 31ch-Auditory-evoked potentials (AEP) for the dichotic sounds were recorded electrically from the scalp. A 60dBSPL of vowel “/a/” was represented mono-aurally with a 50dBSPL of the contra-lateral masking noise, white noise, and multi-talker noise. Brain functions, especially for the cortical response, within the dichotic listening were visualized non-invasively using the scalp potential-based Laplacian mapping technique. Results : Right ear advantage for vowel sound within the left-brain dominancy can be observed in six subjects. The remaining four subjects could not be categorized in the term of ear advantage or brain laterality. Conclusion : It is observed that the auditory processing for the dichotic listening behavior differed from the mono-aural listening. Objective and non-invasive assessment for the brain laterality within the auditory dominancy can be applied for the hearing aids fitting technique.

Commercially Available Low Cost Hearing Aids and these Limitations

The incidence for the congenital profound sensori-neural deafness in birth will be one to two out of 500 cases or 0.2% to 0.4%. Now we can screen out the newborn deaf baby with accuracy using the mass screening system with the automated ABR (Auditory Brainstem Response) and/or the OAE (Oto Acoustic Emission). Some of them will be able to improve their hearing acuity with surgical technology of the cochlea implants. However, this story is only affordable in the developed countries.

Clinical Study of Laryngeal Cancer.

One hundred and nine cases of laryngeal cancer were treated between 1987 and 1997 in the Department of Otorhinolalyngology at Obihiro Kousei Hospital. The average age of the patients was 65.4 years old, and the male to female ratio was 21:1. Based on histopathological diagnosis, 108 cases were reported as squamous cell carcinoma and one case was reported as spindle cell carcinoma. There were 15 cases of supraglottic carcinoma, 91 cases of glottic carcinoma and 3 cases of subglottic carcinoma. There were 33 cases in stage I, 35 cases in stage II, 22 cases in stage III and 19 cases in stage IV. The five-year survival rates of the patients for stages I to IV were 100%, 90%, 66% and 65% respectively.

Nasal Allergy in Tokachi; A Clinical Study.

1993年4月1日より, 1995年7月31日までの間に帯広厚生病院耳鼻咽侯科を受診し, 鼻アレルギーと診断された患者でRISTおよびPASTを施行しえた患者336例を対象として, 十勝地方の鼻アレルギー患者, 特に花粉症においての臨床的検討を加えた。北海道地方ではイネ科花粉症が重要であるといわれているが, 十勝地方ではシラカンバの樹木花粉症が最も重要であり, カモガヤ, チモシーのイネ科花粉症同様ヨモギ花粉症も重要であることがわかった。これは十勝地方の気候, 植性によるものであり, 日常診療において役立てるべきであると思われた。

Enterobacter cloacae Infection of Nasal Cavity; A Case Report.

Enterobacter cloacae infection of the nasal cavity is very rare. A 65-year-old woman visited our hospital complaining of left epistaxis and nasal obstruction. Anterior rhinoscopy showed a black necrotic mass in the left nasal cavity, and a malignant tumor was suspected. The histopathological diagnosis of a biopsy specimen was necrotic tissue with bacterial colonies and no tumor cell. Bacteriological examination of the necrotic mass showed Enterobacter cloacae. So the diagnosis was Enterobacter cloacae granuloma. Piperacillin was given by intravenous infusion. The mass grew smaller and was removed from the nasal cavity.

Caustic burns of upper esophagus, pharynx, and larynx; Report of two cases and review of the literature.

Two patients suffered first-degree caustic burns of the pharynx, larynx and esophagus due to Hyamine solution.A 54-year-old male and a 58-year-old male drank about 30 ml of Hyamine solution administered by mistake instead of Sorbitol.Conservative treatment with electrolyte solution, antibiotics, steroids, and IVH was very effective, and resulted in good recovery.There were no narrowing of the esophagus on endoscopic inspection 9 months after discharge.A review of the literature and various combinations of emergency treatment are discussed.

A case of esophageal perforation caused by a metal chain.

A 6-month-old girl who had esophageal perforation caused by a 10cm metal chain was reported.Roentogenographic examination revealed a chain in the cervical esophagus, subcutaneous emphysema and pneumomediastinum. Even after the chain was removed using an endoscopic technique under general anesthesia, the subcutaneous emphysema and pneumomediastinum became worse.The perforation of the esophagus was primarily sutured via a lateral cervical incision.She fully recovered with no post-operative complications.