Application and Feasibility of Bedside Cranial Ultrasound in Patients with a Translucent Cranial Implant: A Potential Path for an Introduction of a “Neurosurgical Stethoscope”

Abstract Background: Imaging is the cornerstone of management of neurosurgical patients. The use of ultrasound (US) in neurosurgery can potentially avoid some of the disadvantages of computed tomography (CT), including the need for patient transport, and radiation exposure. Traditionally limited in neurosurgical patients due to lack of skull penetrance, the recent introduction of translucent cranial implants can facilitate acoustic-based imaging. Objective: In this study, we sought to examine the feasibility of a bed-side US done post-operatively in patients with translucent cranial implants, and to qualitatively compare the accuracy of this modality in diagnosing basic neurosurgical “red flags” on imaging, to a head CT.Methods: We reviewed 5 cases operated in our institution which underwent implantation of sonolucent cranial implants. Implant size ranged from a burr hole cover to a fronto-temporo-parietal cranioplasty implant (2 – 15cm). Indications for surgery included: normal pressure hydrocephalus, complex hydrocephalus, superficial temporal artery to middle cerebral artery bypass, resection of a falcine meningioma and cranioplasty after decompressive hemicraniectomy. Patients were scanned by ultrasound between post-operative days 1 and 3, immediately prior to a CT scan ordered for a change in clinical status based on attending neurosurgeon’s decision. Results: Relevant anatomy correlated between US and CT in all cases. This included: ventricles contour and size, midline shift, the presence of a mass or mass effect, and catheter tip position when available. Bedside US evaluations were all obtained within 5 minutes (range: 2:00 – 5:30 minutes:seconds) using a handheld probe with standard sonication settings and minimal patient discomfort.Conclusion: Cranial sonolucent implants create an opportunity to use bedside US as a non-invasive imaging modality capable of enhancing the post-operative neurosurgical exam in an acute setting. Further study is needed to refine the use of this modality and characterize the relative advantages it may offer for neurosurgical patients.