Problems in utility and safety of otological allografts

Creutzfeldt–Jakob disease and ENT

Objective:

This review addresses Creutzfeldt–Jakob disease in the context of ENT, and aims to summarise the relevant history, pathophysiology and implications for contemporary practice.

Overview:

Creutzfeldt–Jakob disease is a rare, fatal, neurodegenerative disorder. It is a prion disease with four different subtypes that can only be definitively diagnosed post-mortem. The main implications for the ENT surgeon lie in the risk of iatrogenic transmission. The three facets of assessing individual patient risk are: patient history; tissue infectivity; and procedure infectivity.

Conclusion:

This is a controversial area in medicine, and ENT in particular. This review highlights a clinically applicable approach for everyday use.

A standardized comparison of commercially available prion decontamination reagents using the Standard Steel-Binding Assay

Prions are comprised principally of aggregates of a misfolded host protein and cause fatal transmissible neurodegenerative disorders of mammals, such as variant Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy in cattle. Prions pose significant public health concerns through contamination of blood products and surgical instruments, and can resist conventional hospital sterilization methods. Prion infectivity binds avidly to surgical steel and can efficiently transfer infectivity to a suitable host, and much research has been performed to achieve effective prion decontamination of metal surfaces. Here, we exploit the highly sensitive Standard Steel-Binding Assay (SSBA) to perform a direct comparison of a variety of commercially available decontamination reagents marketed for the removal of prions, alongside conventional sterilization methods. We demonstrate that the efficacy of marketed prion decontamination reagents is highly variable and that the SSBA is able to rapidly evaluate current and future decontamination reagents.

Revisiting the risks involved in using homograft ossicles in otological surgery

Despite the fact that cartilage, cortical bone and corneal homograft tissue is still widely used in South Africa and that there has never been a reported case of human immunodeficiency virus or Creutzfeldt-Jakob disease infection transmission via this route, otolaryngologists are still reluctant to use homograft ossicles. In third world countries, such as South Africa, where ossicular prostheses are not always readily available due to financial constraints, the question arises as to whether we should be reconsidering the use of homograft ossicles. This review examines the risk of developing Creutzfeldt-Jakob disease or acquiring human immunodeficiency virus following the use of homograft ossicles during ossicular reconstruction, and discusses sterilization techniques that have proven effective in eradicating the human immunodeficiency virus and prions. For decades, homograft ossicles have been used worldwide in otological surgery, especially in patients lacking suitable autograft ossicles. There has never been a reported case of transmission of the human immunodeficiency virus, and no cases of transmissible spongiform encephalopathy have been reported in the literature after otological surgery involving only the use of homograft ossicles. There have only been two documented otological cases of Creutzfeldt-Jakob disease; these involved the use of cadaveric dura mater and pericardium for tympanic membrane grafting. The human immunodeficiency virus is easily inactivated by simple sterilisation techniques, and there is a statistically insignificant risk of transmitting this virus if proper sterilisation protocols are followed.

A new ossicle homograft inactivation/preservation procedure: clinical results

A new NaOH-autoclaving inactivation/preservation procedure (IPP) for ossicle homografts, complying with the actual infectious disease guidelines, has been developed and used in our institution for 5 years. This study compares the clinical and audiological results of middle ear reconstruction using the new NaOH-autoclaving inactivated ossicle homografts (22 patients) and the previously used cialit-formaldehyde inactivation procedure (28 patients). During the follow-up period, no homograft extrusion, resorption or disease transmission was observed either for the NaOH-autoclaving or for the cialit-formaldehyde protocol. A postoperative air-bone gap of less than 20 dB in 44% and a postoperative hearing improvement of 10-50 dB in 70% of patients complies with the published success rates of homograft ossiculoplasty in the literature. The analysis and comparison of both tested IPP-patient groups showed no statistically significant differences in the clinical and the audiological results. The NaOH-autoclaving inactivation/preservation protocol should increase ossicle homograft safety even with respect to prion exposure. The good anatomic and audiological long-term results of the new IPP protocol confirm homograft ossicles as a valid and inexpensive approach for middle ear reconstruction.