The larynx is a small organ innervated by two branches of the vagus nerve. On first glance the study of this organ may appear to be simple but the field of neurolaryngology covers a vast range of research topics. The major areas are anatomy and physiology of the motor system, sensory system, proprioception, autonomic nervous system, laryngeal reflex, mechanism of neuronal transmission, laryngeal responses against the feedback system, voluntary motor activities, and neuromuscular pathologies. This paper describes the scope of these areas and presents the major results of basic and clinical investigations conducted by the author and colleagues at Kurume University over the past 35 years.

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Vestibulectomy is subtotal resection of the vestibular fold. Excision of this structure is advocated as (1) a definitive therapeutic procedure for removal of vestibular fold lesions and (2) an adjunctive diagnostic procedure when addressing vocal fold lesions. The surgical objectives are diagnostic and therapeutic when addressing vestibular fold lesions and primarily diagnostic when applied to vocal fold lesions. In the latter, superior exposure of the vocal fold, particularly of the lateral ventricle, permits direct visual and surgical access to the paraglottis and subglottis and is particularly suited to Ti and T2 glottic lesions when definitive excision can be undertaken. In T3 glottic lesions management options are expanded to permit larynx preservation procedures in lieu of the conventional laryngectomy.
Vestibulectomy allows unobstructed visual access intra-and postoperatively, particularly in cases where cordectomy has been performed. Adjunctive vestibulectomy has been useful in cases of postirradiation glottic carcinoma patients where the glottis cannot be competently visualized during follow-up examinations. Vestibulectomy is suited for inflammatory reactive lesions such as the laryngocele and saccular cysts. Voice is usually unaffected and swallowing and airway function are also preserved.
Vestibulectomy has been performed at the time of transverse cordotomy, a procedure which has been utilized in airway restoration after bilateral vocal fold paralysis. Superior exposure of the vocal fold facilitates adequate cordotomy and optimal airway enhancement.
The single complication in over 100 vestibulectomies has been postoperative superior laryngeal artery hemorrhage. This occurred in a case where vestibulectomy had been performed at the time of transverse cordotomy. The patient was returned to the operating room for hemostasis which was achieved with tamponade and laser coagulation.
Our current assessment is that vestibulectomy achieves (1) superior surgical access to the vocal fold intraoperatively, and (2) enhanced visual access postoperatively for clinical exam in 75-90% of cases particularly in patients who receive x-ray therapy and in whom reactiveswelling of the vestibular fold is not uncommon.
Revision vestibulectomy has been performed in select cases when additional enhancement of exposure and visual access to the vocal folds is needed.

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The present status of surgical treatment for laryngeal cancer in the People's Republic of China was reviewed. Partial laryngectomy procedures preserving laryngeal function have been widely developed in China during the last 20 years. According to published reports, 48 to 56% of laryngeal cancer surgery had been performed with partial laryngectomy procedures, and their 5 year survival rates ranged from 70 to 80% which precede those of total laryngectomy. The technique of horizonto-vertical partial laryngectomy (3/4 partial laryngectomy) has been well established in China, and its decanulation rate was 78 to 87% and its 5 year survival rate was 74 to 84%.

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The closure of the airway by the larynx has three functional ends : firstly the prevention of error in deglutition; secondly, trapping of the exhaled air flow inside the thoracic cavity (air trapping); and thirdly, phonation. These three functions were all present in the tertiary period, ca. 65 million years ago. The second function, air trapping, enabled the fixation of the thoracic cage, which is essential for obtaining the supporting points for the shoulder musculature during movements of the upper extremities. This morphological innovation originated in the three-dimesional, discontinuous arboreal habitat of the early mammals, and further evoked in tree-dwelling primates as a safety device to prevent falling from trees. The specificity of the primate larynx is the completely closure of the vocal cords during the air trapping. Although the complete closure of the vocal cords is expressed in humans as adaptation for the production of primary tones, its fundamental origin goes back to the three-dimensional arboreal locomotor adaptation in the Tertiary arboreal primates.

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Using the opportunity of Clinical Panel Discussion in the 10th Annual Meeting of Japan Society of Laryngology, all the members of Ishikawa Laryngectomee Club were asked to answer the questionnaire concerned about their quality of life, and 85 answers (73.3%) were received from 116 alaryngeal chants.
Nineteen patients were from 6 to 10 years after laryngectomy, and 17 from 10 to 15 years, 11 more than 20 years. Forty-seven patients (53.4%) could communicate with esophageal voice, using electrolarynx and 19 (21.6%) Tokyo artificial larynx (Tapia's flute).
The most serious problem of their life was related with their physical dysfunction : disability in expressing the emotion such as laughing and crying, and no sense of smell. The health problems such as catching common cold was seen in 13 patients (15.3%), and mental distress made significant effects on changing their personality. From this studies, not only the necessity to promote social welfare for such handicapped people but also to establish the technique for voice reconstruction after laryngectomy were clearly understood.

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The change of fundamental frequency of phonation (F0) per unit change of transglottal pressure (dF/dP) is known to vary depending on F0. In the coordinates with dF/dP as the y-axis and F0 as x-axis, dF/dP-F0 characteristic takes a shape like a letter V. The reason for this non-linear relation, is investigated with the rubber model of the vocal folds. The length and mass of the vibrating portion of this model are designed to vary in order to test the effects of these parameters on the values of dF/dP. The results suggest : 1) The F0-region lower than 200-250 Hz is mainly controlled by the elongation of the vocal folds. 2) The F0-region higher than these frequencies is mainly controlled by the mass-reduction of the vibrating portion. 3) This allotment in F0 control could be responsible for V shaped characteristic between dF /dP and F0. 4) The pathological lesions of the vocal folds alter this allotment.

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Two post-operated cases who got relatively good results of voice restoration following pharyngolaryngo-esophagotomy were reported. It is necessary to carry out the operation, focussing on air supply into rhinopharyngeal space, simply based on the mechanism of phonation. For operation at ordinary hospitals, it is adviserable not to stick to shunt operation but to be prepared for introduction of voice prosthesis, operation of fistula closing or primary and secondary operation, depending on individual cases. Finally, what is to considered when female post pharyngolaryngoesophagotomy patients acquire voice is how to enable them to acquire feminine voice.

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Since the introduction of the tracheoesophageal fistula (TEF) technique for restoration of voice in 1983, voice restoration using primary and secondary tracheoesophageal fistula in 83 patients undergoing laryngectomy and 24 post-laryngectomy patients have been performed. The success rate (good voice, fair voice) of the primary voice restoration with TEF was 73% between 1983 and 1985, 90% between 1986 and 1990, and 86% between 1991 and 1995. The success rate (good voice, fair voice) of the secondary voice restoration with TEF was 71% between 1983 and 1995. Our results suggest that the Blom-Singer TEF procedure is a safe, simple and effective means of alaryngeal communication.

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The strobo-motion-analyzer is a newly developed device that can synchronously record and analyze both the video signal of the vibrations of the vocal folds and certain voice-related signals (VRS), including the voice signal, EGG, and subglottic pressure by using the flash signal to the strobolight of the laryngostroboscope as a trigger pulse.
Laryngostrobography is a method of recording and analyzing with the strobo-motion-analyzer. It can order 128 fields of the vibratory images of the arbitrary transverse section of the vocal folds in time series as a single still image (Strobogram) superimposed with VRS.
The strobogram of vocal folds stiffened, for example by cancer, a postoperative scar, a cyst, or the like, is compared with that of the normal vocal folds.
The essential principle of vocal fold vibration is the traveling wave motion in the membranous portion of the vocal folds, whose wave crest travels continuously from the lower portion toward the upper potion of the vocal folds.
However, the traveling wave motion is greatly disturbed and changed into the standing wave motion when the vocal folds are stiffened.

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Stroboscopy is daily used to examine the larynx (vocal movement) and video casette recorders (VCR) are used to save the results. However, this sequential type of data storage device is limited. by its inability to : 1) support quick retrieval of the desired images, 2) allow frame by frame observation and printing, and 3) offer a speedy means of data editing and transfer. To solve these problems, the author have newly designed a full digital data system for the stroboscopy of the larynx. It offers following advantages : 1) easy operation, 2) quick display and retrieval of previous images, 3) basic digital image processes (rotation, cutting out of selected images, etc.), 4) capability to print 28 consecutive frames in 1 sheet with a fundamenal frequency, 5) ability to import any image from the VCR (previously recorded), 6) support many image formats (Quicktime, MPEG, AVI, etc.), and 7) send image to any place at any time (internet). This system will play an important role in the digital environment (including the internet) to connect facilities, send and receive images with sound and other biological data in the near future.

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The introduction of the video system is an innovative enhancement to the clinical application of stroboscopy. However, the performance of videostroboscopy is limited to some degree. The NTSC format video system can divide laryngeal movement into 30 frames or 60 fields per second and its maximum resolution is 640 by 480 pixels (picture element). Although this performance is generally sufficient for clinical applications, it has problems with finer observation of laryngeal lesions and lack of brightness occuring during observation of low tone phonation. Clinical application of videostroboscopy is useful but attention should be paid to problems caused by video format.

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Stroboscopy is an essential diagnostic tool in the assessment of the vocal folds during phonation. To evaluate stroboscopy, attention has been focused on symmetry, periodicity, glottic closure, amplitudes, waveforms and non-vibrating segments. Rating forms of the above criteria are used in evaluation, but this assessment is rough and not quantitative. For a more detailed estimation, this paper makes two proposals 1) the use of video prints of multiple sequence images of the glottal cycle and 2) the superimposition of the fundamental frequency (F0) on videostroboscopy. Usage of these video prints enables quantitative evaluation such as measurement of closed phase and glottal area and is effective for patient follow-up. Singers sometimes complain voice problems in high pitch phonation. Superimposition of F0 on videostroboscopy is useful in the detection of such an abnormality according to the changes of F0.

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Over the past 20 years, tracheoesophageal (TE) fistulization has been being performed for voice reconstruction after total laryngectomy in Kobe University Hospital. The essential part of this technique consists of the construction of TE fistula using the membranous part of the trachea, and currently the esophageal muscular loop production arround the esophagus and TE fistula has been added to the original method for preventing aspiration.
Out of a total number of 307 patients, 262 (80%) succeeded in the postoperative TE speech. The rate of the aspiration was clearly improved from 59% in the original technique to 89% in the current one. Main reasons for restoration failure were the obstruction, the destruction of the TE fis-tula and lack of passion in patients.
The pitfall of this technique was precisely discussed.

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The glottis closes during not only cough reflex but also sneezing. It indicates that the activity of laryngeal motor neurons within the nucleus ambiguus is influenced by both the superior laryngeal and the trigeminal afferents. In this study, the convergence of inputs originated from the superior laryngeal and the anterior ethmoidal nerves is examined in decerebrate cats. Thirty two neurons are activated orthodromically by ipsilateral stimulation to the superior laryngeal nerve. Fifty eight neurons are activated orthodromically by ipsilateral stimulation to the anterior ethmoidal nerve. These two neuronal groups are overlapped each other in the nucleus reticularis parvicellularis of medulla. However, the neurons receiving afferents from the superior laryngeal nerve tend to exist in the dorso-lateral portion of the nucleus, while the neurons receiving afferents from the ethmoidal nerve tend to exist in the medio-ventral portion. Seven neurons receive afferents from both nerves. Most of these neurons are located in the overlapped area of two neuronal groups, which is apart from the nucleus ambiguus. The projectional pattern that different inputs converge into the reticular neurons outside of the nucleus ambiguus can be useful for evoking the adequate airway reflex related to the larynx.

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Vocal fold vibration was observed in normal volunteers and patients with laryngeal paralysis using a laryngeal stroboscope to quantitatively evaluate the size of the glottal area. In addition, in order to evaluate vocal function, supraglottic pressure, subglottic pressure and air flow rate were simultaneously measured to determine supra-subglottic pressure difference and average glottal resistance. The subjects consisted of 12 normal volunteers and 24 patients with unilateral laryngeal paralysis (11 median fixation cases, 9 paramedian fixation cases and 4 intermediate fixation cases). For phonatory examination, the sustained vowel /e/ with easy phonation was used. In the laryngeal paralysis patients, the average glottal area was larger as the glottal position deviated from the median position. The supra-subglottic pressure difference was maintained almost constantly regardless of the average glottal area in both the normal volunteers and laryngeal paralysis patients. The average glottal area was directly proportional to the average air flow rate, and the average glottal area was inversely proportional to the average glottal resistance. The supra-subglottic pressure difference, average air flow rate and average glottal resistance of the median fixation cases without glottal closure disorders were almost the same as those of normal volunteers. However, in the median fixation cases with glottal closure disorders, the average air flow rate was higher and the average glottal resistance was lower than those of the normal volunteers.

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[in Japanese]

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[in Japanese]

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