The inner ear, particularly the cochlea, remains one of the most challenging areas in medicine due to its complicated anatomy and limited accessibility. This presents significant hurdles in treating hearing loss (including hyperacusis) and other inner ear disorders. For more than a decade, a dedicated team of physicians and engineers at Columbia University has been working to overcome these challenges by developing a microneedle that to improve the provision of medical treatment for hearing impairments. Additive manufacturing played a crucial role in the development of this innovative device, enabling precise and efficient production.
Thanks to advances in 3D printing, ENT surgeon Anil Lalwani and mechanical engineer Jeffrey Kysar have managed to develop an ultra-thin, 3D printed microneedle for precision medicine in the inner ear. They believe this innovation could improve current therapies, particularly for previously inaccessible areas of the cochlea. The microneedle was created using two-photon photolithography, a specialized 3D printing technique that allows the creation of high-resolution structures. This method ensures that the needle is sharper than existing devices while remaining robust enough for practical use.
The microneedle can inject a contrast agent into the inner ear so that changes in the cochlea can be detected, helping to diagnose diseases such as Menière's disease. MRI images of a guinea pig's cochlea show the different compartments of the cochlea. (Source: Anil Lalwani/Columbia University Vagelos College of Physicians and Surgeons)
One difficulty is the complex anatomy of the cochlea. Dr. Lalwani explained that it is a spiral-shaped, fluid-filled bone: the hardest bone in our body. This makes it difficult to carry out therapy because to reach damaged cells you have to go through a 2 mm wide, very sensitive membrane that often tears with conventional instruments – a problem that can lead to hearing loss or even balance problems. Researchers needed to understand the factors that lead to tearing. For this reason, they imagined the membrane as a tightly stretched tarpaulin. If the hole is too large when inserted, the membrane will tear. The width of the finished 3D printed microneedle corresponds to the width of a human hair.
Therefore, the main goal was to enable treatment of the cochlea without damaging the membrane. In addition, the 3D printed microneedle allows fluid to be removed from the cochlea, which can help diagnose inner ear diseases such as Menière's disease, a localized disorder in the inner ear that causes dizziness, nausea and hearing loss.
Numerous operations have been performed on animals without negative effects or hearing loss and the membrane healed within two days after each procedure. It is currently assumed that the 3D printed microneedle could fundamentally improve the treatment of the inner ear through precise surgical procedures. Lalwani emphasizes: “It is no exaggeration to say that our microneedle could be the key to precision medicine for the inner ear.”
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*Cover photo: Anil Lalwani/Columbia University Vagelos College of Physicians and Surgeons