Overcoming signal resolution barriers of neural prostheses, such as the commercially available cochlear impant (CI) or the developing retinal implant, will likely require spatial control of regenerative neural elements. To rationally design materials that direct nerve growth, it is first necessary to determine pathfinding behavior of de novo neurite growth from prosthesis-relevant cells such as spiral ganglion neurons (SGNs) in the inner ear. Accordingly, in this work, repeating 90° turns were fabricated as multidirectional micropatterns to determine SGN neurite turning capability and pathfinding. Unidirectional micropatterns and unpatterned substrates are used as comparisons. Spiral ganglion Schwann cell alignment (SGSC) is also examined on each surface type. Micropatterns are fabricated using the spatial reaction control inherent to photopolymerization with photomasks that have either parallel line spacing gratings for unidirectional patterns or repeating 90° angle steps for multidirectional patterns. Feature depth is controlled by modulating UV exposure time by shuttering the light source at given time increments. Substrate topography is characterized by white light interferometry and scanning electron microscopy (SEM). Both pattern types exhibit features that are 25 μm in width and 7.4 ± 0.7 μm in depth. SGN neurites orient randomly on unpatterned photopolymer controls, align and consistently track unidirectional patterns, and are substantially influenced by, but do not consistently track, multidirectional turning cues. Neurite lengths are 20% shorter on multidirectional substrates compared to unidirectional patterns while neurite branching and microfeature crossing events are significantly higher. For both pattern types, the majority of the neurite length is located in depressed surface features. Developing methods to understand neural pathfinding and to guide de novo neurite growth to specific stimulatory elements will enable design of innovative biomaterials that improve functional outcomes of devices that interface with the nervous system.
BACKGROUND: Subdural to peritoneal shunt (SPS) placement is an established treatment option for chronic subdural hematoma (SDH) in the pediatric population. Practice patterns vary between institutions, with some advocating shunt removal while others leave the SPS in place after SDH resolution. There remain a paucity of data to document the safety and outcomes after removal of SPS. OBJECTIVE: To support the safety and efficacy of SPS placement and subsequent removal for chronic SDH in children younger than 2 years. METHODS: A total of 26 patients younger than 2 years underwent SPS removal procedures over a 5-year period from 2015 to 2019 at a single institution. Patient characteristics, hospital course, and outcomes were prospectively recorded in the hospital electronic medical record. Attention was given to change in head circumference, size of subdural collection, need for reoperation, or complications because of shunt removal. RESULTS: Patients who underwent SPS placement presented with macrocephaly, signs and symptoms of increased intracranial pressure, and radiographical evidence of subdural collections. The most common etiology of chronic SDH was nonaccidental head trauma (18 of 26 patients). SDS was kept in place for an average of 10 months. Resolution of SDH was demonstrated on imaging for all 26 patients. One patient did require reinsertion of SPS 2 weeks after SPS removal. CONCLUSION: Removal of SPS remains controversial, and careful consideration of patient, family, and provider preferences and potential risks associated with SPS removal must be taken into consideration.
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