The National Institute for Clinical Excellence is examining collagen injection for vocal cord augmentation and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about collagen injection for vocal cord augmentation.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

• comments on the preliminary recommendations
• the identification of factual inaccuracies
• additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows:

• The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
• The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales and Scotland.

For further details, see the Interventional Procedures Programme manual, which is available from the Institute's website (www.nice.org.uk/ipprogrammemanual).

Closing date for comments: 22 March 2005

Target date for publication of guidance: June 2005

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

Current evidence on vocal cord augmentation suggests that there are no major safety concerns and that it is efficacious in patients requiring short-term symptom relief. However, evidence on long-term efficacy is lacking.

Patients should be fully informed of the uncertainty about the procedure's long-term efficacy, and of the alternative treatment options. Use of the Institute's Information for the public is recommended.

Glottic insufficiency, which may be secondary to vocal fold (cord) scarring, atrophy or paresis, is a condition that leaves patients with phonatory compromise in both voice intensity and frequency. Vocal fold paresis (where the nerves that control the muscles acting on the vocal fold fail) may be idiopathic or have an iatrogenic cause; either of the vocal folds may be affected or it may be bilateral.

Conservative management by voice therapy may be beneficial if the muscle groups affected by vocal fold paresis can be developed through vocal exercise. Surgical approaches can be used to reposition or reshape the vocal fold and they may involve implanting a physical device. Autogenous fat, Teflon and silicone can be injected to improve vocal fold function. Of these, autogenous fat is generally well tolerated. Teflon and silicone, however, may (rarely) produce complications because of sensitivity reactions to the materials used.

The collagen is injected either transorally or transcutaneously from below the vocal fold using a laryngeal needle. The exact placement of collagen varies depending on the patient's pathology. The procedure can be carried out with local anaesthesia, and may not require admission. A variety of collagen products have been used in research studies, for example biochemical cross-linked products and purified bovine collagen. Patients who are selected for therapy commonly undergo a skin sensitivity test. Antibiotic prophylaxis may be given.

In a case series of 45 patients with glottic insufficiency for whom other forms of treatment were considered unsuitable, collagen injection improved the maximum voice intensity by a mean of 2.91 dB (p < 0.026) at 12 months after the procedure. However, the mean change in normal voice intensity was not statistically significant.

One case series of 18 patients with electromyographically confirmed vocal fold paralysis who were injected with purified bovine collagen showed good improvement in dysphonia score compared with baseline in 95% (13/14) of patients at 6.5 months after treatment. In the same study, an improvement was found in maximum phonation time (8.6 seconds compared with 5.7 seconds at baseline). In a longer-term follow-up of patients in this study, 83% (5/6) of patients maintained good results in terms of subjective voice assessment at 3 years. In the four patients available for objective voice assessment at 3 years, maximum phonation time had improved further (12.2 seconds compared with 4.2 seconds at baseline). For more details, refer to the sources of evidence (see Appendix).

In a case series of 27 patients treated with collagen injection, one patient had an immediate short-term decrease in voice quality which was associated with excessive injection, and one patient had transient vocal fold oedema.

Two case series with a total of 63 patients reported no serious adverse events up to 12 months following the procedure. In six patients followed-up for 3 years, there were no complications such as seroma, granuloma formation or migration of injected collagen. For more details, refer to the sources of evidence (see Appendix).

The Committee noted that collagen was just one of a variety of agents used for vocal fold augmentation, and that these may have different risk and benefit profiles.

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

Interventional procedure overview of collagen injection for vocal cord augmentation, December 2004

Available from: www.nice.org.uk/ip258overview