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Background We are developing an intradural approach to spinal cord stimulation, where the thin electrode array is affixed stably to the underside of the thoracic spinal dura mater without leakage of cerebrospinal fluid. As part of the design and testing process, we sought to evaluate the potential risk of inadvertent contact of the array with the pial surface of the spinal cord during variations in spinal loading. Methods As part of the risk assessment process, a 2-part study was undertaken. First, a retrospective review of the imaging studies of 25 patients was done in the supine, 45- and 90-degree positions to measure the positional shift between the T9 and T10 vertebral bodies as a function of spinal angulation. Second, similar measurements were made on a cadaveric model, with and without a prototype intradural stimulator implanted at the T9–T10 position and with and without 13.8 kg (30 lb) of axial spinal loading at the 90-degree orientation. Results In all cases, the measured relative displacement of the dura mater towards the spinal cord in both the imaging and the cadaveric arms of the study was less than 1 mm. Conclusions The implantation method for the thin intradural array of the prototype device will ensure that the anatomic separation between it and the pial surface of the spinal cord will be the same as that of the dura mater. Therefore the risk of inadvertent contact will be no greater than that due to the mass effects of standard epidural stimulator implants.

Background Chronic midline low back pain is the number one reason for disability in the United States despite the prolific use of medical and surgical interventions. Notwithstanding the widespread use of epidural spinal cord stimulators (SCSs), there remains a large portion of the population with inadequate pain control thought to be because of the limited volume of stimulated neural tissue. Intradural SCSs represent an underexplored alternative strategy with the potential to improve selectivity, power efficiency, and efficacy. We studied and carried out development of an intradural form of an SCS. Herein we present the findings of in vivo testing of a prototype intradural SCS in a porcine model. Methods Six female juvenile pigs underwent surgical investigation. One control animal underwent a laminectomy only, whereas the 5 other animals had implantation of an intradural SCS prototype. One of the prototypes was fully wired to enable acute stimulation and concurrent electromyographic recordings. All animals underwent terminal surgery 3 months postimplantation, with harvesting of the spinal column. Imaging (microcomputed tomography scan) and histopathologic examinations were subsequently performed. Results All animals survived implantation without evidence of neurologic deficits or infection. Postmortem imaging and histopathologic examination of the spinal column revealed no evidence of spinal cord damage, cerebrospinal fluid fistula formation, abnormal bony overgrowth, or dural defect. Viable dura was present between the intra- and extradural plates of the device. Electromyographic recordings revealed evoked motor units from the stimulator. Conclusions Chronically implanted intradural device in the porcine model demonstrated safety and feasibility for translation into humans.

Background Decompressive craniectomy procedures are performed in patients with malignant intracranial hypertension. A bone flap is removed to relieve pressure. Later, a second operation is performed to reconstruct the skull after brain swelling has resolved. This surgical treatment would be improved if it were possible to perform a single operation that decompressed the brain acutely and eliminated the need for a second operation. To design a device and procedure that achieve this objective, it is essential to understand how the brain swells after a craniectomy procedure. Methods We identified 20 patients with ischemic stroke who underwent a decompressive hemicraniectomy operation. Skull defect morphology and postoperative brain swelling were measured using computed tomography scan data. Additional intracranial volume created by placing a hypothetical cranial plate implant offset from the skull surface by 5 mm was measured for each patient. Results The average craniectomy area and brain herniation volume was 9999 ± 1283 mm 2 and 30.48 ± 23.56 mL, respectively. In all patients, the additional volume created by this hypothetical implant exceeded the volume of brain herniation observed. Conclusions These findings show that a cranial plate with a 5-mm offset accommodates the brain swelling that occurs in this patient population.

Objective The Wishbone device is designed to enable surgeons to quickly and accurately localize the cranial midline. It is intended to be of particular use when localizing the burr hole site during posterior ventriculoperitoneal shunt (VPS) surgery. Methods The Wishbone is a simple mechanical device with 2 adjustable caliper arms that reversibly attach to a patient's left and right external auditory canals. The Wishbone's laser localizer illuminates the midline scalp. The Wishbone was used to localize the posterior midline in a pilot series of patients undergoing VPS surgery. Midline localization and ventricular catheter placement accuracy were determined using findings from postoperative computed tomography scans. Results The Wishbone is a mechanically robust device and proved easy for surgeons to use. Forty patients underwent VPS surgery using the Wishbone to localize the posterior midline. The localization procedure took less than 3 minutes. The average distance separating the Wishbone-localized midline scalp location and the computed tomography−defined anatomical midline was 2.9 mm (95% confidence interval 1.6–4.1 mm). In all cases, the ventricular catheter entered the ipsilateral lateral ventricle. The catheter tips were placed in the ipsilateral (n = 34) or contralateral (n = 5) frontal horn in all but 1 patient. In 1 patient, the catheter tip entered the parenchyma due to a burr hole localization error in the rostrocaudal dimension, unrelated to the Wishbone. Conclusions We describe a simple, efficient, and cost-effective system for accurately localizing the posterior cranial midline. A larger patient series is required to definitively compare its clinical utility relative to frameless stereotaxis-based midline localization methods.

Introduction Contemporary approaches to surgical site infections have evolved significantly over the last several decades in response to the economic pressures of soaring health care costs and increasing patient expectations of safety. Neurosurgeons face multiple unique challenges when striving to avoid as well as manage surgical implant infections. The tissue compartment, organ system, or joint is characterized by biological factors and physical forces that may not be universally relevant. Such implants, once rare, are now routine. Although the prevention, diagnosis, and treatment of surgical site infections involving neural implants has advanced, guidelines are ever changing, and the incidence still exceeds acceptable levels. We assess the impact of these factors on a new class of implantable neuromodulation devices. Methods The available evidence along with practice patterns were examined and organized to establish relevant groupings for continuing evaluation and to propose justifiable recommendations for the treatment of infections that might arise in the case of intradural spinal cord stimulators. Results Few studies in the modern era have systematically evaluated preventive behaviors that were applied to intradural neural implants alone. We anticipate that future efforts will focus even more on the investigation of modifiable factors along a continuum from bacterially repellant implants to weight management. Early diagnosis could offer the best hope for device salvage but to date has been largely understudied. Conclusions Historically, prevention is the cornerstone to infection mitigation. However, immediate diagnosis and hardware salvage have not received the attention deserved, and that approach may be especially important for intradural devices.

Objective Compare therapeutic response of patients to conventional versus high-frequency spinal cord stimulation (SCS). Methods Twelve patients with back and leg pain who met standard clinical criteria for a trial of conventional SCS (low-frequency stimulation [LFS]) participated in a half-day session of high-frequency stimulation (HFS) during their weeklong conventional trial. HFS consisted of frequencies ranging from 50 Hz to 4 kHz, or 100 Hz to10 kHz, at constant voltage settings increasing from 0.5 V to 10 V. Visual Analog Scale scores from 0 to10 were recorded, along with notes of any clinical discomfort and open patient comments. Results Two of 12 patients had no benefit from either LFS or HFS. In the remaining 10 patients, paresthesias were significantly altered by HFS, and four experienced complete elimination of paresthesias. Five patients preferred HFS to LFS, with an additional three preferring both equally. Abrupt sensation to the onset of HFS was described in six patients, and in ten patients, HFS allowed maximum voltage stimulation of 10 V without discomfort. The four patients who did not have a successful trial of stimulation had significantly longer duration of pain compared to the eight patients who went on to permanent implant (11.2 vs. 4.3 years, P = 0.04). Conclusions HFS significantly altered the feeling of paresthesias in the majority of patients (ten of 12), was preferred to LFS in five of 12 patients, and non-inferior to LFS in eight of 12 patients. Both 4 kHz and 10 kHz stimulation allowed patients to benefit from HFS. HFS allowed maximum voltage stimulation without discomfort.

Background The decompressive hemicraniectomy operation is highly effective in relieving refractory intracranial hypertension. However, one limitation of this treatment strategy is the requirement to perform a subsequent cranioplasty operation to reconstruct the skull defect—an expensive procedure with high complication rates. An implant that is capable of accommodated post-hemicraniectomy brain swelling, but also provides acceptable skull defect coverage after brain swelling abates, would theoretically eliminate the need for the cranioplasty operation. In an earlier report, the concept of using a thin, moveable plate implant for this purpose was introduced. Methods Measurements were obtained in a series of stroke patients to determine whether a plate offset from the skull by 5 mm would accommodate the observed post-hemicraniectomy brain swelling. The volume of brain swelling measured in all patients in the stroke series would be accommodated by a 5-mm offset plate. In the current report, we expanded our analysis to study brain swelling patterns in a different population of patients requiring a hemicraniectomy operation: those with traumatic brain injuries (TBI). Results We identified 56 patients with TBI and measured their postoperative brain herniation volumes. A moveable plate offset by 5 mm would create sufficient additional volume to accommodate the brain swelling measured in all but one patient. That patient had malignant intraoperative brain swelling and died the following day. Conclusions These data suggest that a 5 mm offset plate will provide sufficient volume for brain expansion for almost all hemicraniectomy operations.

John C. VanGilder, the former professor and chairman of neurosurgery at The University of Iowa died on August 27, 2007 after making a lasting impact to the field of neurosurgery both in the United States and abroad. In this manuscript, we review VanGilder's life and achievements. VanGilder was born in 1935 in West Virginia and received his undergraduate education at West Virginia University in Morgantown. He studied medicine at the University of West Virginia, completing his final 2 years at the University of Pittsburgh, and after serving in the U.S. military, completed his neurosurgical training at Washington University in St. Louis. He was appointed to faculty positions first at Yale University and later at The University of Iowa, where he became professor and later chairman of the Division of Neurosurgery. VanGilder also served as president of the Society of Neurological Surgeons (1997-1998), president of the Neurosurgical Society of America (1998-1999), chairman of the American Board of Neurological Surgery (1997-1998), and vice president of the American Academy of Neurological Surgery. At The University of Iowa, VanGilder played a key role in the transition of the Division of Neurosurgery to a Department of Neurosurgery and mentored several neurosurgeons who would go on to become department chairmen or make other important neurosurgical contributions at other medical schools in the United States.

Background The posterior ventriculoperitoneal shunt (VPS) placement procedure is technically efficient and cosmetically appealing. The main limitations of the posterior approach relate to the technical challenges associated with accurately placing the ventricular catheter. In this report, we describe methods and simple devices used for posterior VPS surgery that have evolved over a >25-year period to enhance catheter placement accuracy and reduce complication rates. Objective We describe the combination of methods and customized devices used at a single institution to perform posterior VPS surgery. Results are presented for the most recent 11-year epoch, along with a description of sources of technical errors and plans for further methodologic refinements. Materials and Methods The medical records and imaging studies of 468 patients undergoing posterior VPS, from 2007 to 2018 were reviewed. Ventricular catheter placement accuracy data were collected and complications were identified and recorded. Results Optimal ventricular catheter placement was achieved in 98.29%. Of the remaining 1.71%, one half (0.85%) required acute revision surgery. Four patients (0.85%) developed new neurologic deficits following surgery; 2 were related to intraparenchymal hemorrhages and 2 (0.43%) as a result of a misplaced catheter. The deficits resulting from poor catheter placement were transient. The complication rates due to causes other than catheter placement accuracy compared favorably with those reported previously in the literature. Conclusions Using the methods and devices described in this series, posterior VPS operations can be performed safely with a high degree of ventricular catheter placement accuracy.