Establishing proof of concept for sonolucent cranioplasty and point of care ultrasound imaging after posterior fossa decompression for Chiari malformation

Background: Evaluation after posterior fossa decompression for Chiari malformation can require repeated imaging, particularly with persistent symptoms. Typically, CT or MRI is used. However, CT carries radiation risk and MRI is costly. Ultrasound is an inexpensive, radiation-free, point-of-care modality that has, thus far, been limited by intact skull and traditional cranioplasty materials. Ultrasound also allows for imaging in different head positions and body postures, which may lend insight into cause for persistent symptoms despite adequate decompression on traditional neutral static CT or MRI. We evaluate safety and feasibility of ultrasound as a post-operative imaging modality in patients reconstructed with sonolucent cranioplasty during posterior fossa decompression for Chiari malformation. Methods: Outcomes were analyzed for 26 consecutive patients treated with a Chiari-specific sonolucent cranioplasty. This included infection, need for revision, CSF leak, and pseudomeningocele. Ultrasound was performed point-of-care in the outpatient clinic by the neurosurgery team to assess feasibility. Results: In eight months mean follow up, there were no surgical site infections or revisions with this novel sonolucent cranioplasty. Posterior fossa anatomy was discernable via transcutaneous ultrasound obtained point-of-care in the clinic setting at follow up visits. Conclusion: We demonstrate proof of concept for ultrasound as a post-operative imaging modality after posterior fossa decompression for Chiari malformation. With further investigation, ultrasound may prove to serve as an alternative to CT and MRI in this patient population, or as an adjunct to provide positional and dynamic information. Use of sonolucent cranioplasty is safe. This technique deserves further study.