Accurate trajectory inference in time-series spatial transcriptomics with structurally-constrained optimal transport.

The use of surgical drills has become a key facet of temporal bone surgery. Although chisels can still be useful for particular applications, the introduction of rotating drills has enabled both efficient and precise removal of dense bone. Cutting burrs featuring sharp blades enable efficient local drilling, while diamond-coated burrs—without blades—provide a more localized effect to rather abrade the bone, eliminating the risk of blade-related injury to soft tissue. Nevertheless, the rotational force itself can still cause mechanical or thermal damage to adjacent soft tissue. A particularly vulnerable structure is the membranous labyrinth. This structure of the inner ear separates the endolymph from the surrounding perilymph. When the bony labyrinth is opened, as in semicircular canal plugging or vestibular implantation, the membrane may be ruptured by the rotating drill. For example, in the intralabyrinthine semicircular canal approach for vestibular implantation, a fenestration is made in each semicircular canal to allow advancement of an electrode to its ampulla. There, the electrode serves to stimulate the adjacent neural tissue, to facilitate the restoration of vestibular function. Surgically fenestrating and then plugging a semicircular canal may be indicated for certain patients with disabling superior canal dehiscence syndrome or benign paroxysmal positional vertigo. While inner ear function may be present in candidates for these procedures, hearing and vestibular function are at risk. Deterioration might occur due to rupture of this membrane, as it could cause leakage of endolymph, mixing of endolymph and perilymph, as well as mechanical stress on the sensory structures. Therefore, methods to spare the membranous labyrinth could play a crucial role in reducing the risk of the most debilitating adverse effect associated with inner ear surgery. By minimizing these risks, a broader range of patients could benefit from these procedures. The risk of rupture when opening the semicircular canals can be minimized by meticulously skeletonizing (‘bluelining’) and then using a microhook to remove the very thin remaining bone or endosteum. However, to use this method, the remaining bone must be drilled very thin, which increases the risk of accidentally opening the canal. In addition, the hook risks damaging the membrane. A recently investigated hand-guided robotic drill that relies on force and torque sensing parameters to automate cessation, provided promising results for drilling through bone while sparing the underlying membranous labyrinth. However, this drill is still under development and not yet clinically available.