Hisayoshi Kojima

Regeneration of the vocal fold using autologous mesenchymal stem cells

The aim of this study was to regenerate the injured vocal fold by means of selective cultured autologous mesenchymal stem cells (MSCs). Eight adult beagle dogs were used for this experiment. Selective incubation of MSCs from bone marrow was done. These MSCs were submitted to 3-dimensional incubation in 1% hydrochloric acid atelocollagen. Three-dimensional incubated MSCs were injected into the left vocal fold, and atelocollagen only was injected into the right vocal fold of the same dog as a control. Four days after injection, the posterior parts of the vocal folds were incised. The regeneration of the vocal fold was estimated by morphological and histologic evaluations. Our results showed that 3-dimensional incubated MSCs were useful in the regeneration of the injured vocal fold. This study shows that damaged tissues such as an injured vocal fold would be able to be regenerated by tissue engineering.

Recent Modifications in Thyroplasty Type I

Among thyroplasties, type I is the most frequently used for medialization of the vocal cord. Follow-up study on patients indicated that reversion of voice can occur after operation. Revision was done in five cases with improvement of voice. On the basis of this experience, modifications were made in the technique of thyroplasty type I. They include 1) cutting the calcified cartilage with minimal intervention in the soft tissue, 2) fixation of the window with a silicone plug to enhance medialization, and 3) overmedialization of the vocal cord and definition of criteria for it that can be used during surgery.

Cortical processing mechanism for vocalization with auditory verbal feedback.

To investigate the relationship between motor and sensory speech center, cortical activity was examined using PET while normal subjects perceived their own voice which sounded different to the articulated one. The results showed significant activation in the superior temporal gyri with absence of activity in the supplementary motor area (SMA). In a previous study we found significant activation in SMA with no activity in the superior temporal gyrus when normal subjects simply vocalized. Thus, two different cortical pathways for vocalization were delineated: programmed pathway in SMA, and pathway with auditory verbal feedback. The former is thought to be the mature system in the adult, and the latter may be related to speech acquisition.

Cortical activation by monaural speech sound stimulation demonstrated by positron emission tomography.

To investigate how auditory input from each ear contributes to spoken language processing, cortical activation by monaural speech sound stimulation was examined in 12 normal subjects using15O-labeled water positron emission tomography. Regional cerebral blood flow (rCBF) was measured under four different sound stimulation conditions: (1) silence, (2) white noise, (3) sequential Japanese sentences (“speech”), and (4) Japanese sentences played backward (“reversed speech”), and the results were evaluated by statistical parametric mapping (SPM). Noise induced significant rCBF increase in the contralateral Heschl’s gyrus. Speech and reversed speech stimuli caused significant rCBF increase in the contralateral Heschl’s gyrus and the bilateral superior temporal gyri, with contralateral activation broader than that in the ipsilateral hemisphere. Monaurally input speech sound signals that reach the contralateral Heschl’s gyrus may be processed chiefly and phonologically in the surrounding superior temporal gyrus in the same hemisphere. Comparison of speech activation with reversed speech activation failed to demonstrate a significant difference, which made it difficult to identify the area for lexical and semantic processing.

Vocal Fold Atrophy and its Surgical Treatment

The effectiveness of surgical treatment for vocal fold atrophy of various causes was examined. Type I thyroplasty was performed on 31 patients with vocal fold atrophy, often bilaterally and occasionally combined with type III thyroplasty. Of these 31 patients, 3 patients underwent the operation twice, for a total of 34 operations. The surgery was found to be effective in improving the voice quality and the ease of phonation. When a scar or sulcus was present, the results were not as satisfactory. The intraoperative decision-making process as to which procedure to perform is extremely important for achieving an optimal voice, and should be based on the intraoperative voice quality, fiberoptic findings, and manual tests. In operations for vocal fold atrophy in which the vocal folds are mobile, a silicone shim should be firmly fixed to prevent migration. Overcorrection is generally recommended. No complications were encountered. It was often the increased ease of phonation rather than the improved voice quality that patients appreciated after surgery.

Cortical speech processing mechanisms while vocalizing visually presented languages.

TO elucidate cortical processing during vocalization, we used positron emission tomography to measure regional cerebral blood flow during vocalization in six Japanese subjects. During reading Japanese sentences used daily or short syllables aloud, the visual cortices, the left Heschls gyrus, Brocas area, the primary motor area of the articulatory organs, the supplementary motor area and the cerebellum were significantly activated, compared with resting conditions. The superior temporal gyri were rarely activated. Significant activation of the cerebellum was observed by comparing cortical activity during reading sentences used daily with that during reading meaningless short syllables. These results suggest that vocalization of familiar materials is taken over by the cerebellum, rather than cortical speech areas, and without engagement of the superior temporal gyri.

Vocal Fold Atrophy: Quantitative Glottic Measurement and Vocal Function

Videostroboscopic glottic measurements and vocal function were evaluated in 41 vocal fold atrophy patients with bowed vocal folds. The amount of bowing in the resting position and the glottal gap area and vibratory amplitude during phonation were measured from digitized videostroboscopic images. Vibratory amplitude was not decreased on atrophic vocal folds. With the same amount of total bowing, the glottal gap area for bilateral atrophy was smaller than for unilateral atrophy. These results suggest that vocal fold atrophy is not disadvantageous to thyroplasty type I, and that bilateral procedures may produce a better outcome than a unilateral procedure in the treatment of bilateral atrophy. Acoustic, aerodynamic, and perceptual parameters of vocal function were measured. The acoustic high-frequency power ratio and the H-index correlated with the glottal gap area. The mean flow rate correlated with the amount of bowing. The degree of dysphonia was related to the size of the glottal gap and bowing.

Acoustic characteristics of rough voice: Subharmonics*

This study investigates the relationship between rough voice and the presence of subharmonics, which correspond to smaller yet distinct peaks located between two consecutive harmonic peaks in the power spectrum. Spectrum analysis was undertaken in 389 pathologic voices, of which 20 had subharmonics. Although all 20 voices had roughness perceptually, 8 had normal jitter and/or shimmer. The degree of roughness had a significant inverse relationship with the frequency of subharmonics. By digital signal processing, sound samples with various types of subharmonics were synthesized and perceptually analyzed. Power and frequency of subharmonics in the synthesized sound also had significant relationships with the degree of roughness. Rough voice is acoustically characterized not only by jitter and shimmer but also by the presence of subharmonics in the power spectrum. Subharmonics are important acoustic properties for objective evaluation of rough voices.

Videoendoscopic laryngeal surgery.

This paper introduces videoendoscope-assisted laryngeal surgery with office-based equipment. With this technique, a patient is seated and the nose, pharynx, and larynx are topically anesthetized. A flexible videoendoscope with a light-sensitive charge-coupled device chip built into the tip is transnasally inserted by an assistant. Specially designed fine-tipped forceps and scalpels were developed for removal of laryngeal lesions. Videoendoscopic laryngeal surgery was undertaken in 114 cases of laryngeal lesions such as polyps, granuloma, and cancer. For benign vocal fold lesions, postoperative vocal function was shown to be improved on aerodynamic and perceptual analyses. For laryngeal tumors, biopsy of the lesion was easily undertaken. Videoendoscopic laryngeal surgery presents the following advantages. It is applicable to outpatients not requiring general anesthesia, it enables functional monitoring of the patients voice and vocal fold during phonation, it allows for delicate manipulations with both hands, and it gives high-resolution images in comparison to conventional fiberscopy.

Recurrent laryngeal nerve regeneration by tissue engineering

The recurrent laryngeal nerve (RLN) does not regenerate well after it has been cut, and no current surgical methods achieve functional regeneration. Here, we evaluate the functional regeneration of the RLN after reconstruction using a biodegradable nerve conduit or an autologous nerve graft. The nerve conduit was made of a polyglycolic acid (PGA) tube coated with collagen. A 10-mm gap in the resected nerve was bridged by a PGA tube in 6 adult beagle dogs (group 1) and by an autologous nerve graft in 3 dogs (group 2). Fiberscopic observation revealed functional regeneration of the RLN in 4 of the 6 dogs in group 1. No regeneration of the RLN was observed in any dog in group 2. We also tested for axonal transport, and measured the compound muscle action potential. The RLN can be functionally regenerated with a PGA tube, which may act as a scaffold for the growth of regenerating axons.