Robotic Applications in Cranial Neurosurgery: Current and Future.

Robotics applied to cranial surgery is a fast-moving and fascinating field, which is transforming the practice of neurosurgery. With exponential increases in computing power, improvements in connectivity, artificial intelligence, and enhanced precision of accessing target structures, robots are likely to be incorporated into more areas of neurosurgery in the future-making procedures safer and more efficient. Overall, improved efficiency can offset upfront costs and potentially prove cost-effective. In this narrative review, we aim to translate a broad clinical experience into practical information for the incorporation of robotics into neurosurgical practice. We begin with procedures where robotics take the role of a stereotactic frame and guide instruments along a linear trajectory. Next, we discuss robotics in endoscopic surgery, where the robot functions similar to a surgical assistant by holding the endoscope and providing retraction, supplemental lighting, and correlation of the surgical field with navigation. Then, we look at early experience with endovascular robots, where robots carry out tasks of the primary surgeon while the surgeon directs these movements remotely. We briefly discuss a novel microsurgical robot that can perform many of the critical operative steps (with potential for fine motor augmentation) remotely. Finally, we highlight 2 innovative technologies that allow instruments to take nonlinear, predetermined paths to an intracranial destination and allow magnetic control of instruments for real-time adjustment of trajectories. We believe that robots will play an increasingly important role in the future of neurosurgery and aim to cover some of the aspects that this field holds for neurosurgical innovation.

Electrode Placement Accuracy in Robot-Assisted Asleep Deep Brain Stimulation.

Deep brain stimulation (DBS) involves the implantation of electrodes into specific central brain structures for the treatment of Parkinson's disease. Image guidance and robot-assisted techniques have been developed to assist in the accuracy of electrode placement. Traditional DBS is performed with the patient awake and utilizes microelectrode recording for feedback, which yields lengthy operating room times. Asleep DBS procedures use imaging techniques to verify electrode placement. The objective of this study is to demonstrate the validity of an asleep robot-assisted DBS procedure that utilizes intraoperative imaging techniques for precise electrode placement in a large, inclusive cohort. Preoperative magnetic resonance imaging (MRI) was used to plan the surgical procedure for the 128 patients that underwent asleep DBS. During the surgery, robot assistance was used during the implantation of the electrodes. To verify electrode placement, intraoperative CT scans were fused with the preoperative MRIs. The mean radial error of all final electrode placements is 0.85 ± 0.38 mm. MRI-CT fusion error is 0.64 ± 0.40 mm. The average operating room time for bilateral and unilateral implantations are 139.3 ± 34.7 and 115.4 ± 42.1 min, respectively. This study shows the validity of the presented asleep DBS procedure using robot assistance and intraoperative CT verification for accurate electrode placement with shorter operating room times.

Resistance to venous flow: A mathematical description and implications for compartment syndromes.

BACKGROUND: The object of this work was to describe resistance to flow within a vein in a closed compartment. METHODS: A vein is mathematically modeled as a collapsible cylinder with fixed perimeter exposed to extraluminal hydrostatic pressure within a closed compartment of the body. The principle of minimization of energy is used to determine the cross-sectional area and resistance to flow through such a cylinder in various states of collapse. RESULTS: A mathematical expression for the cross-sectional area of a partially collapsed tube is derived. Resistance to flow is calculated within the tube in various states of collapse and compared with the resistance to flow in an annular tube of identical cross-sectional area. Resistance increases very rapidly in the first 5% of collapse and remains greater than that in an annular vessel of identical cross-sectional area through all further collapse. Resistance to flow closely follows a logarithmic gain as the tube undergoes collapse from extraluminal pressure until opposite sides of the vein make contact. CONCLUSION: Within a closed compartment in which there is rising pressure, resistance to flow through a vein is predicted to increase as a logarithmic function of the vein's cross-sectional area. This rapid rise in resistance and hence decline in flow are consistent with the position that in compartment syndromes of all anatomic locations, the venous contribution to resistance of flow is of paramount importance to the pathophysiology.

Are upright lateral cervical radiographs in the obtunded trauma patient useful? A retrospective study.

BACKGROUND: The best method for radiographic "clearance" of the cervical spine in obtunded patients prior to removal of cervical immobilization devices remains debated. Dynamic radiographs or MRI are thought to demonstrate unstable injuries, but can be expensive and cumbersome to obtain. An upright lateral cervical radiograph (ULCR) was performed in selected patients to investigate whether this study could provide this same information, to enable removal of cervical immobilization devices in the multiple trauma patient. METHODS: We retrospectively reviewed our experience with ULCR in 683 blunt trauma victims who presented over a 3-year period, with either a Glasgow Coma Score <13 or who were intubated at the time of presentation. RESULTS: ULCR was performed in 163 patients. Seven patients had studies interpreted to be abnormal, of which six were also abnormal, by either CT or MRI. The seventh patient's only abnormality was soft tissue swelling; MRI was otherwise normal. Six patients had ULCR interpreted as normal, but had abnormalities on either CT or MRI. None of the missed injuries required surgical stabilization, although one had a vertebral artery injury demonstrated on subsequent angiography. ULCR had an apparent sensitivity of 45.5% and specificity of 71.4%. CONCLUSION: ULCR are inferior to both CT and MRI in the detection of cervical injury in patients with normal plain radiographs. We therefore cannot recommend the use of ULCR in the obtunded trauma patient.

The benefit of neurogenic mixed evoked potentials for intraoperative spinal cord monitoring during correction of severe scoliosis: a case study.

STUDY DESIGN: A case report is presented. OBJECTIVE: To present a case in which surgical correction of a severe scoliotic curve caused unilateral loss of neurogenic mixed evoked potential data despite unchanged somatosensory data. SUMMARY OF BACKGROUND DATA: Surgical correction of large scoliotic curves presents a risk to the function of the spinal cord. Multimodality intraoperative neurophysiologic monitoring of the spinal cord is recommended during such procedures. METHODS: A 13-year-old girl with severe double major scoliosis underwent a staged operative procedure for correction of her spine deformity. Intraoperative neurophysiologic monitoring using somatosensory-evoked potentials and neurogenic mixed evoked potentials was performed for each stage. RESULTS: During the final stage (a T4-L5 posterior instrumentation and fusion) left neurogenic mixed evoked potential data were lost approximately 45 minutes after placement of the left-side, correcting rod. The surgeon was warned of the data change. Set bolts were loosened at all fixation points, and the data quickly returned to within normal limits of baseline. Somatosensory data never approached warning criteria at any point during surgery. The patient awakened with no neurologic deficit. CONCLUSIONS: Neurophysiologic monitoring using both somatosensory-evoked potentials and neurogenic mixed evoked potentials is recommended when surgery is performed to correct spine deformity. The Stagnara wake-up test, somatosensory-evoked potentials, and neurogenic mixed evoked potentials are important components of spinal cord monitoring during surgery, and should be used together for optimal protection of neurologic function.