Differences in the phonetic mechanism between monkeys and humans were studied using 6 adult Japanese monkeys. Their vocal cords were fixed with formalin and cut along and across the axis. Some of the samples were treated with 10% NaOH to dissolve cells and elastic fibers, and some of them were treated with 90% formic acid to consume cells and collagen fibers. Each sample was then fixed with OsO₄, dehydrated, dried at the critical point, ion-coated, and studied under a scanning electron microscope. Both collagen fibers and elastic fibers mostly ran straight, and their density was higher in upper layers, but little regional difference in the fiber properties was noted. In the muscle layer, connective tissue surrounded muscle fibers were scarce. From these findings, the fibrous structure of the monkey vocal cord is much simpler than that of human vocal cord, and this is considered to reflect the short and monotonous phonation of monkeys.

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Laryngoendoscopic observations and recordings of dynamic image obtained from patients with laryngeal lesions are performed using a rhino-larynx electronic endoscope system. The electronic endoscope differs from the flexible fiberscope in that it contains a small light-sensitive CCD chip which is attached to the tip of the flexible endoscope. This rhino-larynx electronic endoscope has the small CCD camera in the tip portion of approximately 5mm in diameter and can be passed through the nasal passage into the laryngeal cavity. The dynamic image provided by this electronic endoscope system is superior to that obtained by a fiberoptic endoscope in resolution of the detail. Some clinical cases observed by this system are presented.

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At our E. N. T. Clinic in Keio University Hospital, a visual observation is regarded as an especially important factor in making a diagnosis. An observation is made by enlarging the vocal fold image on a CTR using a laryngoscope.
It is essential that an examination should not only be performed but that the acquired results be utilized both effectively and efficiently.
To this end, all the examination results are recorded on a VTR and at the same time input in the form of digital video records into our personal computer. The computer used is widely used type and our own application software is developed for operating.
The method is as follows :
# 1 Register the patient's data to be used as a data base.
# 2 Label each VTR of patient's data.
# 3 Search the patient's past data and display the visual Image.
# 4 Search the patient's past data as it progresses over time, and display the visual image.
# 5 Analyze the results of stroboscopic imaging using fuzzy logic.
# 6 Display a demonstration video of laryngeal disorders.
# 7 Perform a phonetic screening test using fuzzy logic.
This method proves to be useful in making a diagnosis with regard to progress over time. It is also quite useful in informing patients and teaching students. Our report is an example of applying personal computers in medical treatment.

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The purpose of laryngostroboscopy is to observe the vibration of the vocal fold. The essential principle of human vocal fold vibration during phonation is the travelling wave phenomenon of the mucous membrane. This wave crest travels from the lower portion to the upper-lateral portion of the vocal fold continuously. Consequenly, both the so-called upper lip and the lower lip indicate the wave crest of the travelling wave.
This travelling wave phenomenon was clearly observed by the newly developed digital subtraction X-ray stroboscopy.
Furthermore, easy visualization and quantitative analysis of vibrations of the vocal fold synchronously with some voice-ralated signals (VRS) including the voice signal, EGG, subglottic pressure on laryngostroboscopy has become possible by the newly developed laryngostrobography.
The observation of the travelling wave by conventional laryngostroboscopy was explained by the aforementioned method.

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Diagnosis of vocal disorders require : 1) evaluation of the actual area of the lesion, 2) assessment of degree severity and the evaluation of the clinical course and 3) the determination of the causative factors. Establishing the type of vocal disorder and degree severity of organic vocal disorders can be diagnosed with video fiberscopy while phoniatric function tests are utilized to evaluate the prognosis of the patient during the course of therapy. Determination of maximum phonation time, range of voice, flow rate, change in intensity of voice and/or vocal pitch is a useful tool in diagnosing the degree severity or to evaluate the clinical course. In many cases, video fibroscopy alone cannot be definitive in diagnosing functional vocal disorders. Therefore, we incorporated the loading phoniatric function tests to ascertain the underlying vocal disorders and for differential diagnosis of organic vocal disorders from the functional vocal disorders. Furthermore, for organic vocal disorders, it is useful to evaluate the therapeutic results during the course of therapy.

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Aerodynamic test for phonatory function have focused on the interrelations of vocal pitch and intensity levels and air flow rate through the glottis supported by subglottic pressures in laryngeal diseases.
We examined the aerodynamic phonatory test for normal and laryngeal dysfunction, and discussed the clinical evaluation of the parameters such as Maximum phonation time (MPT), mean flow rate (MFR), Vocal velocity index (VVI), subglottal pressure (Psub) and Laryngeal efficiency (acoustic power/subglottic power : Le) sustained vowel /a/ phonation at maximum intensity and several seconds at comfortable pitch and intensity levels.
PS-77 equipment and the P1-201 computer analyzing system developed by Iwata in our clinic were utilized. To obtain the correct parameters, several clinical observation of the phonatory function test were explained precisely.
Although the values of these parameters may not give us the diagnosis, the data showed the degree of dysfunction and provided on objective evolution of larygeal diseases especially to compare with the data between pre and post treatments.

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The effects of transglottal pressure on fundamental frequency of phonation (dF/dP) were investigated by loading a sudden transglottal pressure change during sustained phonation.
1) Human experiments
Fourteen human subjects participated. The results showed that the values of dF/dP within the modal register were smallest around 200 Hz in males, and 250-400Hz in females and children. The values of dF/dP as a function of F₀ varied following a V-shaped pattern, indicating that the role of transglottal pressure on F₀ was not only important in low modal register, but also in high modal register.
2) Dog experiments
Five dogs were involved. The forced phonation under simulated activities of cricoarytenoid (CT) muscles and thyroarytenoid (TA) muscles showed that the CT muscle activities have the strongest effects on the V-shaped pattern.
Human and dog experiments revealed the definite role of transglottal pressure for regulation of F₀ in high modal register.

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Voluntary use of voice in human speech and song is supported by uniquely human mechanisms of peripheral apparatus and neural adaptation to their forms. This paper examines various mechanisms of voice fundamental frequency (F0) control by laryngeal muscles based on previous reports by the author and others. Besides the well-known function of the cricothyroid, other intrinsic muscles potentially contribute to voice control by their own unique manners. Extrinsic laryngeal muscles apply horizontal and vertical forces to the laryngeal framework to enhance F0 control. The horizontal component interacts with supra-laryngeal articulators and provides causal explanation of the intrinsic vowel F0. The vertical component produces a rotation of the cricoid cartilage by means of vertical laryngeal movement along the curvature of the carvical spine. Thus, F0 is tuned by overall force balance among a number of laryngeal muscles, and our capacity of its voluntary use reflects morphological characteristics of the human larynx.

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The variability and controllability of vocal fundamental frequency (F₀) are investigated by analyzing the acoustic and perceptual characteristics of sustained vowel samples recorded from patients with spasmodic dysphonia (SPD) as well as patients with various types of laryngeal disorders and normal controls. All the pathological groups show larger variations in F₀ or lower controllability than the normal controls. The voice segments perceptually judged as non-sporadic show significantly larger variations in F₀ than the normal controls. From the voice segments perceptually judged as sporadic, instantaneous changes in F₀ or in amplitude, chaotic changes in voice waveform such as bifurcations are observed. Based on the obtained results, a model of normal and disordered voice control mechanism is proposed, in which morphological and neural abnormalities affect voice variability. The acoustic analysis method described here is found beneficial in analyzing voice variability and controllability, and can provide useful information to know normal and disordered voice control mechanisms.

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Observations of the shape of the mouth opening and the position of the larynx during whispering reveal that the mouth opening widens and the larynx lifts when speakers intend to whisper in high pitch. On the contrary, the mouth opening narrows and the larynx lowers in low pitch. These movements of the mouth and the larynx seem to play an important role for changing pitch in whispered vowels. This result supports the conclusion obtained from our perceptual and acoustical study for whispered vowels that the shifts of the first and the second formant frequencies correspond to the perception of the pitch change.
Flow rates, subglottal pressure and/or mesopharyngeal pressure were proved to be among the important aerodynamic cues for changing loudness in whispered vowels.
It is suggested that there are some physiological mechanisms to substitute the lack of vocal fold vibration to change pitch and intensity in whispered speech.

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Three cases of external laryngeal trauma due to traffic accident were reported.
Case 1, an 18-year-old male, was hospitalized due to increasing dyspnea and dysphonia. Tracheotomy following naso-tracheal intubation was performed, and the patient was symptom free two weeks later without further surgical treatment.
Case 2, a 31-year-old male, was admitted with laryngeal framework fracture and other multiple injuries. Tracheotomy and stent insertion to the larynx were done to establish his airway and to support the laryngeal framework. Three months later, he was discharged with mild dysphonia.
Case 3, an 18-year-old male, was transferred from another hospital with difficult decanulation following tracheotomy for laryngeal trauma. We performed staged operations; upper tracheal re-construction using rib-cartilage graft and thyroplasty type 1. Normal airway and improved voice were obtained after these operations, and the patient returned to a normal social life.
In this paper, we emphasized that the goals of treatment for laryngeal trauma are to establish an adequate airway and to obtain a satisfactory voice. Furthermore, the necessity of strict course observation and the usefulness of some surgical technics for laryngeal trauma were discussed.

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Surgical management of the injured larynx is described. Laryngeal injuries are classified as external or internal, depending on the cause of injury. External injuries include penetrating and blunt traumas. Internal injuries include acute intubation trauma, chronic subglottic stenosis due to prolonged intubation, web formation after endoscopic laryngeal surgery, and so on.
Clinical features of each external laryngeal trauma differ from one another. Multiple procedures may be necessary to improve laryngeal function. Five cases of external laryngeal trauma are demonstrated.
In contrast, intubation granuloma and laryngeal web may be treated with a distinct policy. Surgical procedures for these conditions are described.

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A new method of laryngeal laser surgery under local anesthesia was developed for the treatment of benign mass lesions using KTP laser. Thirteen patients have underwent this surgery since August 1995 to April 1996. Lesions involved were leukoplakia in five patients, granuloma in four, hemangioma in one, and papilloma in three. Ten cases underwent this laser surgery once and have demonstrated no evidence of recurrence. One case of granuloma showed recurrence repeatedly, and needed this laser surgery three times. One case of papilloma showed widespread lesion, and we could not remove the tumor by this procedure and required laryngomicrosurgery. A recurrent small lesion which occurs after laryngomicrosurgery could be well controlled by the present laser surgery under local anesthesia. Another case of widespread papilloma displayed remnant lesion after this surgery and dropped out. No case had a postoperative hemorrhage and edema of larynx. This method has proved to be useful for treating benign laryngeal mass lesions easily and repeatedly under local anesthesia on an outpatient basis.

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To clarify the vocal function in laryngeal cancer as a function of the T stage, the voice was evaluated both aerodynamically and acoustically. The number of patients were 417 patients (390 male, 27 female), with glottic cancer (Tis : 8, T1a : 117, T1b : 80, T2 : 73, T3 : 27, T4 : 12), and with supraglottic cancer (T1 : 9, T2 : 53, T3 : 32, T4 : 6). The voice was evaluated in terms of the these parameters : maximum phonation time (MPT); mean air flow rate during phonation over comfort able duration (MFRc); fundamental frequency (F0); sound pressure level (SPL); fundamental frequency range of phonation (FOrange); sound pressure level range of phonation (SPLrange); pitch perturbation quotient (PPQ); amplitude perturbation quotient (APQ); normalized noise energy for 0-4kHz (NNEa); normalized noise energy for 1-4kHz (NNEb). The results are summarized as follows. In glottic cancer, 1) MPT and MFR remained in normal range in many patients except for T4, 2) F0 tended to decrease as T stage advanced, 3) SPL tended to increase as T stage advanced, 4) acoustic parameters, such as PPQ, APQ, NNEa and NNEb, tended to increase as T stage advanced. In supraglottic cancer, 4) MPT, MFR and SPL range remained in normal range in T1, and 2) acoustic parameters tended to increase as T stage advanced.

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A 30-year-old woman suffering from subglottic stenosis due to Wegener's granulomatosis (WG) was reported. She first visited us in 1982 because of exudative otitis media (EOM) on the right. The saddle nose and crusting in the nasal cavity gradually became apparent in 1990. Subsequently, she developed left EOM in 1993. Repeated examinations showed no inflammatory signs and negative titer of cytoplasmic pattern of antineutrophil cytoplasmic antibody (CANCA). In January, 1995, she suddenly developed severe dysphonia and exertional dyspnea. Laryngoscopy revealed marked swelling of the subglottic mucosa. Histologic examination of the nasal mucosa revealed vasculitis, lymphocyte infiltration, and foreign body giant cells, and CANCA was found positive. Thus, thirteen years after onset, the diagnosis was established as WG. She was given prednisolone (PSL) at 60mg/day for five days, which greatly relieved her of the subglottic stenosis. Administration of PSL was then tapered to 5 mg/day.
Cyclophosphamide (CPM) was not given to her. Although combination of PSL and CPM therapy greatly contributed improvement of life prognosis in patients with generalized WG, this treatment might be too aggressive to the patients with WG limited to the head and neck region because of unfavorable drug side effects such as increased occurrences of infection and cancer of the urinary bladder. Since subglottic stenosis is troublesome to treat surgically, it is indispensable to diagnose WG in its early stage in order to start appropriate medical treatment for improvement of the stenosis.

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A case of a 50-year-old man complaining of swelling in the right submandibular region was reported. Laryngoscopic examination revealed a swelling of the right false cord. Cervical X-ray and MRI examinations showed an air-filled mass from the right submandibular to paralaryngeal regions, which was removed surgically by a lateral neck approach. In a microscopic examination, the cyst was found to be lined with the pseudostratified ciliated epithelium similar to that in the upper respiratory tracts, and was diagnosed as laryngocele.
It was known that laryngocele is derived from enlargement of the laryngeal saccule located in the laryngeal ventricle. It is also known that the incidence of laryngocele in Japan is very rare compared to that in Europe and the USA. To clarify the reasons for the difference in incidence of laryngocele, measurements of thirteen laryngeal saccules were performed in thirteen surgical specimens of total laryngectomized cases here in our department. Although the incidence and location of laryngeal saccule were similar to those of the Caucasian cases recorded, the length of saccule was found to be shorter. From the results, the difference in shape of laryngeal saccule, especially the length, could be one of the reasons for the difference in incidence of laryngocele between Japanese and non-Japanese investigated.

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A case of malignant lymphoma in the larynx of a 57-year-old male was reported. Laryngoscopic examination revealed a submucosal tumor in left false vocal cord. Biopsy of the lesion showed a histopathological finding of non-Hodgkin malignant lymphoma (diffuse lymphoma, medium-sized cell type), and the clinical stage was diagnosed as IE. The patient underwent radiation therapy (50Gy) and chemotherapy (CHOP). No recurrence was observed for seven years after the therapy. Cases of malignant lymphoma in the larynx including this case were reviewed and discussed.

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