What's holding us back? Understanding barriers to innovation in academic neurosurgery.
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Academic Medical Centers↗
Biomedical subjects
Eric C Leuthardt
Publications and source records attributed to Eric C Leuthardt.
Electrocorticography-based brain computer interface--the Seattle experience.
Electrocorticography (ECoG) has been demonstrated to be an effective modality as a platform for brain-computer interfaces (BCIs). Through our experience with ten subjects, we further demonstrate evidence to support the power and flexibility of this signal for BCI usage. In a subset of four patients, closed-loop BCI experiments were attempted with the patient receiving online feedback that consisted of one-dimensional cursor movement controlled by ECoG features that had shown correlation with various real and imagined motor and speech tasks. All four achieved control, with final target accuracies between 73%-100%. We assess the methods for achieving control and the manner in which enhancing online control can be accomplished by rescreening during online tasks. Additionally, we assess the relevant issues of the current experimental paradigm in light of their clinical constraints.
Cerebral Cortex↗
The emerging world of motor neuroprosthetics: a neurosurgical perspective.
A MOTOR NEUROPROSTHETIC device, or brain computer interface, is a machine that can take some type of signal from the brain and convert that information into overt device control such that it reflects the intentions of the user's brain. In essence, these constructs can decode the electrophysiological signals representing motor intent. With the parallel evolution of neuroscience, engineering, and rapid computing, the era of clinical neuroprosthetics is approaching as a practical reality for people with severe motor impairment. Patients with such diseases as spinal cord injury, stroke, limb loss, and neuromuscular disorders may benefit through the implantation of these brain computer interfaces that serve to augment their ability to communicate and interact with their environment. In the upcoming years, it will be important for the neurosurgeon to understand what a brain computer interface is, its fundamental principle of operation, and what the salient surgical issues are when considering implantation. We review the current state of the field of motor neuroprosthetics research, the early clinical applications, and the essential considerations from a neurosurgical perspective for the future.
Brain↗
Ventricular catheter tack-down suture: technical note.
Tubing migration accounts for a significant number of shunt complications. In an attempt to reduce the likelihood of disconnection and tubing migration, we have developed a technique to rigidly fix the proximal catheter to the skull. The method involves the placement of a small twist drill hole adjacent to the catheter burr hole through which a suture is passed. The suture is then used to rigidly bind the proximal shunt tubing and valve to the skull. This approach provides an efficient and effective means for reducing complications related to shunt tubing migration.
Cerebral Ventricles↗
Orthopedic surgery after selective dorsal rhizotomy for spastic diplegia in relation to ambulatory status and age.
OBJECT: A retrospective study was performed to determine the following: 1) whether children who walk independently after selective dorsal rhizotomy (SDR) undergo fewer subsequent orthopedic operations than those who walk with assistance; and 2) the effect of age at SDR on the rate of orthopedic operations. METHODS: The cases of 158 children with spastic diplegia who were 2 to 14 years of age when they underwent SDR were followed over a 5- to 9-year period. Patients were grouped by age at the time of SDR as follows: 2 to 3 years (Group 1), 4 to 7 years (Group 2), and 8 to 14 years (Group 3). Follow-up data showed that children in all age groups who walked independently after SDR underwent fewer orthopedic operations than did children who walked with assistance. Overall rates of orthopedic surgery 5 to 9 years after SDR at last follow up were 24% for independent walkers and 51% for assisted walkers. Two-way categorical analysis (age group by ambulation) yielded a highly significant effect of ambulation (p = 0.0003). Children in Group 1 needed the fewest orthopedic operations at follow-up evaluation. In the older age groups (Groups 2 and 3), those who walked independently at the time of SDR underwent fewer orthopedic operations after SDR than did walkers who required assistance (p = 0.01). CONCLUSIONS: These data are of value in advising parents about the likelihood of orthopedic surgery based on the child's gait status both at the time of SDR and at follow-up evaluation. Orthopedic surgery is more likely in patients destined to be nonambulators.
Activities of Daily Living↗
A brain-computer interface using electrocorticographic signals in humans.
Brain-computer interfaces (BCIs) enable users to control devices with electroencephalographic (EEG) activity from the scalp or with single-neuron activity from within the brain. Both methods have disadvantages: EEG has limited resolution and requires extensive training, while single-neuron recording entails significant clinical risks and has limited stability. We demonstrate here for the first time that electrocorticographic (ECoG) activity recorded from the surface of the brain can enable users to control a one-dimensional computer cursor rapidly and accurately. We first identified ECoG signals that were associated with different types of motor and speech imagery. Over brief training periods of 3-24 min, four patients then used these signals to master closed-loop control and to achieve success rates of 74-100% in a one-dimensional binary task. In additional open-loop experiments, we found that ECoG signals at frequencies up to 180 Hz encoded substantial information about the direction of two-dimensional joystick movements. Our results suggest that an ECoG-based BCI could provide for people with severe motor disabilities a non-muscular communication and control option that is more powerful than EEG-based BCIs and is potentially more stable and less traumatic than BCIs that use electrodes penetrating the brain.
Adult↗
9p21 and 13q14 dosages in ependymomas. A clinicopathologic study of 101 cases.
Ependymomas are glial neoplasms whose clinical behavior is difficult to predict based on histology alone. Recently, a comparative genomic hybridization study identified frequent chromosome 9p and 13q losses in anaplastic ependymomas, suggesting that p16 and RB alterations may be involved in tumor progression. In order to test this hypothesis further, 101 myxopapillary, conventional, and anaplastic ependymomas (51 spinal and 50 intracranial tumors) were tested for RB and p16 deletions using fluorescence in situ hybridization. Clinical follow-up, ranging from 2 to 198 months (median 46 months), was obtained in 90 cases (91%). RB and p16 deletions were seen in 22 of 92 (24%) and 22 of 89 (25%) informative cases, respectively. Polysomies were more frequent in the grade I and II spinal tumors, consistent with prior reports of increased aneuploidy in such cases. No significant genetic associations were seen with tumor grade, recurrence, or death, suggesting that 9p and 13q deletions do not play a prominent role in the malignant progression of ependymomas, as has been implicated in other glioma subtypes.
Adolescent↗
Effect of selective dorsal rhizotomy on need for orthopedic surgery for spastic quadriplegic cerebral palsy: long-term outcome analysis in relation to age.
OBJECT: The authors performed a long-term evaluation of gait status to determine the frequency with which orthopedic operations for cerebral palsy are conducted before and after selective dorsal rhizotomy (SDR) and the relation between pre- and post-SDR orthopedic surgery and age. METHODS: Fifty-two patients with spastic quadriplegia were prospectively followed for 5 to 9 years. All children were evaluated and underwent SDR at St. Louis Children's Hospital. Preoperative scores for gait function and details of previous orthopedic procedures were recorded for two age groups: those 2 to 5 (Group 1) and those 6 to 14 years of age (Group 2). Data were collected from parents who completed a questionnaire a mean of 7.5 years after SDR. Relations between gait status and the number/type of pre- and post-SDR orthopedic procedures, rate of improvement after SDR, benefit of operation according to parents, and return of spasticity were analyzed. Forty-nine percent of patients in Group 1 and 25% of those in Group 2 had improved gait scores. The interaction between pre- or post-SDR time frame and walking mode was statistically significant (p = 0.004). Among those children who had not undergone orthopedic surgery before SDR, the incidence of surgery post-SDR was higher in the older children (Group 2) than the younger children (Group 1 [70% compared with 34%]). Parents of 75% of the Group 1 patients and 88% of the Group 2 patients felt that their children benefited from SDR. CONCLUSIONS: The results of this study highlight the effect of SDR on gait status in children with spastic quadriplegic cerebral palsy. The percentage of patients needing orthopedic operations was not as high as reported previously. Parents indicated that SDR was beneficial to their children.
Adolescent↗
Diffusion-weighted MR imaging in the preoperative assessment of brain abscesses.
BACKGROUND: Diffusion-weighted MR imaging (DWI) has recently shown promise in differentiating ring-enhancing lesions such as brain abscess and malignant neoplasm. The ability of DWI to strongly suggest brain abscess enables a neurosurgeon to alter stereotactic planning to optimize diagnosis. We report our experience with DWI in 5 patients with lesions on MR imaging and review the literature to assess the usefulness of this technique in the preoperative evaluation of cerebral abscess. METHODS: The MR images of 5 patients presenting with ring-enhancing lesions that ultimately proved to be brain abscesses were retrospectively reviewed. In addition to standard MR sequences, trace DWI and apparent diffusion coefficient (ADC) calculations were performed on all patients. Additionally, 15 recently published articles or references in press concerning DWI in cerebral abscesses were reviewed. RESULTS: All lesions were markedly hyperintense on DWI and had diminished ADC. Thirty-eight of 39 previously reported abscesses were hyperintense on DWI with reduced ADC. Of 165 nonpyogenic lesions with DWI findings, 87 were hypointense or isointense, 78 lesions had variable hyperintensities, and few manifested the degree of hyperintensity observed with abscesses. Most of these included chordomas and epidermoids, which are not likely to be confused with abscesses. CONCLUSIONS: Restricted water diffusion, as indicated by hyperintensity on DWI and low ADC, in ring-enhancing lesions assists in differentiating brain abscess from necrotic tumor. This information facilitates stereotactic surgical planning: abscesses should be preferentially centrally aspirated, whereas necrotic brain tumors should have diagnostic tissue biopsied from cavity walls. Although not definitive for brain abscess, restricted water diffusion is an important MR imaging sign and is useful in neurosurgical treatment strategies for ring-enhancing lesions.
Adult↗
Frameless stereotaxy without rigid pin fixation during awake craniotomies.
OBJECTIVE: The accuracy and precision of resection with awake brain mapping is augmented when combined with frameless stereotaxy. Frameless stereotactic assisted surgery, however, typically involves immobilization in Mayfield pins. Rigid fixation, however, may be problematic for individuals undergoing awake craniotomy. We describe an alternate method of frameless stereotaxy without the use of pin fixation. METHODS: The MRI fiducials are placed in proximity to the proposed incision and prepared and draped in the operative field. After craniotomy, the epidural skull clamp (standardly used to support the electrode holder during corticography) is attached. Using the Stealth Navigational System, a spinal reference arc is then clamped onto the skull clamp base. After the fiducials and arc are registered, the probe is used for frameless guidance. RESULTS: In 14 of 15 cases (93%), this technique was successful. One case failed because of close proximity of the fiducials to the incision. The accuracy of the 14 successful cases was less than 4 mm. The error within the lesion itself was always less than 2 mm. Overall, these results are comparable to those achieved using a Mayfield head holder. In all tumor cases, postoperative imaging concurred with intraoperative assessment of a total versus subtotal resection. CONCLUSIONS: By affixing the spinal arc to the skull, the complications and discomfort associated with pin fixation are avoided completely. The patient is free to move without affecting the accuracy. The spine arc, in combination with the skull clamp, provides an efficient, well-tolerated, and accurate method of frameless navigation for the awake patient undergoing craniotomy.
Awareness↗