Asako Ikeda

Injection laryngoplasty with calcium phosphate cement

Objective: To assess the feasibility of injection laryngoplasty with calcium phosphate cement (CPC), which is an injectable paste, self-hardening, and which recrystallizes to calcium hydroxylapatite after injection. Study Design: A case series with planned data collection. Methods: Fifty-six patients with unilateral vocal fold paralysis, who received injection laryngoplasty with CPC between August 2003 and August 2007 with a minimum follow-up period of six months, were enrolled in this study. Volumetric and migration analysis for injected CPC were performed using CT after surgery. Vocal function was also assessed by GRBAS subjective voice assessment scale and maximum phonation time (MPT), acoustic analysis including period perturbation quotient (PPQ), amplitude perturbation period (APQ), and noise-to-harmonics ratio (NHR). Results: No remarkable migration or absorption of injected CPC was observed on CT up to two years after surgery. The average remaining volume of CPC was 87.8% ± 5.3% two years after injection compared to immediately after injection. Significant improvements in GRBAS scales, MPT, PPQ, APQ, and NHR were observed postoperatively. No adverse effects were observed. Conclusions: Our clinical experience revealed that CPC was safe, nonabsorbable, and effective. Injection laryngoplasty with CPC may be a useful option in the treatment of glottic insufficiency.

Suitability of Calcium Phosphate Cement for Injection Laryngoplasty in Rabbits

Calcium phosphate cement (CPC) consists of powder and liquid, which become an injectable paste after mixing, self-hardening and recrystallizing to calcium hydroxylapatite (CaHA) after injection into a living body. In this study, we investigated the suitability of CPC as an injectable material for injection laryngoplasty using rabbits. All rabbits underwent left recurrent laryngeal nerve section and injection laryngoplasty with CPC. At 7 days, scanning electron microscopic findings revealed that complete recrystallization from CPC to CaHA was achieved in the larynx. At 1, 3, and 6 months, injected CPC stayed in the paraglottic space and did not migrate, and the average remaining CPC volume percentage was 91.7%. Focal foreign body reaction to injected CPC was almost the same as that of autologous fat for all time periods observed. These results indicated that CPC appears to be biocompatible, nonabsorbable, nonmigratory, and suitable for injection laryngoplasty.

Sentinel node detection in n0 laryngeal cancer

Abstract Problem: Sentinel lymph node (SLN) is the lymph node that directly receives lymphatic flow from a primary cancer lesion. Attention has been focused on the SLN concept, which implies that lymphatic metastasis initially occurs at SLN. In SLN navigation surgery, lymph node dissection beyond SLN can be omitted if SLN is metastasis free. Favorable outcomes are reported for malignant tumors such as breast cancer, malignant melanoma, and gastrointestinal cancer, and the application of this concept to other types of cancer is anticipated. In this study, the implications of the SLN concept on laryngeal cancer were investigated by measuring the feasibility of determining indications for neck dissection according to the presence of metastasis to SLN. Methods: Eleven patients suffering from laryngeal cancer staged T2 or higher and clinically N0 were enrolled in this study. Ninety-nine mTc-phytate (74MBq/mL) was injected submucosally by 0.2 mL into the several sites adjacent to the tumor using endoscope on the day preceding surgery. The lymphoscintigrams were performed 2 hours after injection. SLNs were surveyed using a gamma probe immediately prior to incision and during neck dissection. Histopathological examinations were performed on the resected lymph nodes. Results: One to three SLNs were confirmed by preoperative lymphoscintigraphy and intraoperatively by gamma probe in all of the cases. The pathological evaluation of SLNs revealed that 4 cases had subclinical metastasis, showing consistency with the sentinel node concept. In other 7 cases, metastasis to SLN as well as to other lymph nodes was negative, reflecting the correct lymph node status. No false-negative results were observed. Conclusion: Although more cases need to be studied in order to determine the feasibility of applying the SLN concept to laryngeal cancer, so far all cases were consistent with the sentinel node concept. Significance: SLN detection may be useful for determining indications for neck dissection in N0 laryngeal cancer. Support: None reported.

Neurofunctional recovery after GDNF gene transfer in the recurrent laryngeal nerve-injured rat

Abstract Problem: To assess the possibility of gene therapy for recurrent laryngeal nerve (RLN) injury, we examined the neuroprotective effect after glial cell line-derived neurotrophic factor (GDNF) gene transfer into nucleus ambiguus in a rat vagal nerve avulsion model. Morphological preservation of motoneurons has previously been demonstrated (Brain Res 962: 61–67, 2003). However, functional recovery of RLN after gene therapy has not been demonstrated. In the present study, we examined neurofunctional recovery after GDNF gene transfer in a rat RLN injury model. Methods: The left RLN of Sprague-Dawley rats was crushed for 60 seconds with forceps. Immediately after the crush and confirmation of left fixed vocal fold, an adenoviral vector encoding beta-galactosidase gene (AxCALacZ) or GDNF (AxCAhGDNF) was directly injected into the crushed site of RLN. Transgene expression by AxCALacZ in nucleus ambiguus was examined by X-gal histochemistry. Measurement of conduction velocity (CV) of RLN and laryngoscopy to check motion recovery of the left vocal fold were performed 2 and 4 weeks postoperation. The cross-section of RLN was histologically examined after epon/toluidine blue staining. Results: Motoneurons and their neurites in nucleus ambiguus were labeled with X-gal staining 4 days after AxCALacZ injection, indicating successful induction of foreign gene into the nucleus ambiguus by retrogradely transported adenoviral vector from the crushed site. In comparison between AxCAhGDNF-injected, AxCALacZ-injected, and noninjected animals, significantly better CV of RLN and better vocal fold motion recovery rate were observed in AxCAhGDNF-injected animals 2 and 4 weeks postoperation. RLN cross section of AxCAhGDNF-injected animals showed better myelination compared to the controls. Conclusion: Injection of adenoviral vectors into the crushed site of RLN successfully induced the foreign gene into motoneurons in nucleus ambiguus. Adenoviral GDNF gene transfer after RLN crush improved the CV of RLN and motion recovery of the paralyzed vocal fold. Significance: Adenoviral GDNF gene therapy may provide neurofunctional recovery in humans with a paralyzed vocal fold. Support: None reported.

A histopathological study after vocal fold injection of calcium phosphate paste

Abstract Problem: The injection of space-occupying materials into the lateral vocal fold is the commonly used technique for vocal fold (VF) medialization. The ideal injectable material would be biocompatible, nonreactive, nonvolatile, noncarcinogenic, and easily injected and would maintain its volume and position after injection. It is also clinically important that it be easily prepared. In Japan, aside from autologus tissue (fat, etc), the only available injectable material is atelocollagen. However, it is quickly absorbed and needs repeat injection; therefore, a new injectable material is needed. Calcium phosphate paste (CPP) (BIOPEX, Mitsubishi Materials Corporation, Tokyo) is currently used in a wide variety of surgical settings including orthopedic procedures and craniofacial reconstructions, and has been proved to be safe and injectable. In this study we examined if CPP could be used as an injectable material for VF medialization. Using rabbit models, soft tissue response and the migratory and absorption property of CPP were investigated. Methods: New Zealand white rabbits underwent left recurrent laryngeal nerve section for denervation and CPP was injected into the paraglottic space. One, 3, and 6 after the operation, the animals were painlessly euthanized, the larynges were excised, and histopathologic, volume, and migration analysis were performed. Results: The position of CPP was stable in the paraglottic space and the volume remained constant through all time periods. Thin fibrous encapsulation around CPP was also observed and remained unchanged when compared at one, three, and six months after injection. A very small number of local foreign body giant cells were observed; however, there was no apparent infiltration of inflammatory cells. Three and 6 months after injection, ossification adjacent to the thyroid cartilage was observed. Conclusion: After vocal fold injection using CPP in rabbit, soft tissue response was minimal, and the volume and position of CPP were stable. Significance: CPP could be used as a new injectable material for VF medialization. Support: None reported.

Gene transfer to the vocal fold mucosa

Abstract Problem: Scar formation after surgical manipulation or trauma on the vocal fold mucosa causes dysphonia due to impaired vocal fold vibration. There is no effective treatment modality to prevent scar formation to date. On the other hand, recent advances in wound healing research revealed the mechanism of wound healing. Specific growth factors or their inhibitors may potentially prevent scar formation in the vocal fold. Although the use of growth factors or their inhibitors appears promising for the treatment of scar formation, clinical application is limited by the inability to achieve steady state level in the vocal fold mucosa after single administration of the agent. Gene transfer seems to be an attractive way to achieve long-term but not permanent expression of growth factors to modulate the wound healing process. This study investigated the possibility of gene transfer to the vocal fold mucosa using adenovirus vectors. Methods: New Zealand white rabbits (NZWRs) were anesthetized and replication-defective recombinant adenovirus carrying beta-galactosidase gene (AxCALacZ) was injected into the vocal fold. In other NZWRs, 3 × 3 mm mucosal wounds were made and were topically applied with AxCALacZ. Animals were euthanized 3 days after surgery and the larynges were excised for histological analysis. All specimens were stained with X-gal solution to detect beta-galactosidase expression. Results: X-gal staining revealed remarkable expression of beta-galactosidase in vocal fold mucosa, submucosa, and vocalis muscle at the injection site. When the vector was applied topically to the wounds, remarkable expression of beta-galactosidase was observed in vocal fold mucosa and the surface of the wound. Conclusion: Local injection and topical application of adenovirus vectors to the vocal fold successfully induced the foreign gene into vocal fold mucosa. Significance: Adenovirus-mediated gene transfer could be a new therapeutic system for preventing scar formation, to express growth factors or their inhibitors to modulate wound healing in vocal fold mucosa. Support: None reported.