Non-lesional epilepsy does not necessarily convey poor outcomes after invasive monitoring followed by resection or thermal ablation.

OBJECTIVE: We aimed to compare outcomes including seizure-free status at the last follow-up in adult patients with medically refractory focal epilepsy identified as lesional vs. non-lesional based on their magnetic resonance imaging (MRI) findings who underwent invasive evaluation followed by subsequent resection or thermal ablation (LiTT). METHODS: We identified 88 adult patients who underwent intracranial monitoring between 2014 and 2021. Of those, 40 received resection or LiTT, and they were dichotomized based on MRI findings, as lesional (N = 28) and non-lesional (N = 12). Patient demographics, seizure characteristics, non-invasive interventions, intracranial monitoring, and surgical variables were compared between the groups. Postsurgical seizure outcome at the last follow-up was rated according to the Engel classification, and postoperative seizure freedom was determined by Kaplan-Meyer survival analysis. Statistical analyses employed Fisher's exact test to compare categorical variables, while a t-test was used for continuous variables. RESULTS: There were no differences in baseline characteristics between groups except for more often noted PET abnormality in the lesional group (p = 0.0003). 64% of the lesional group and 57% of the non-lesional group received surgical resection or LiTT (p = 0.78). At the last follow-up, 78.5% of the patients with lesional MRI findings achieved Engel I outcomes compared to 66.7% of non-lesional patients (p = 0.45). Kaplan-Meier curves did not show a significant difference in seizure-free duration between both groups after surgical intervention (p = 0.49). SIGNIFICANCE: In our sample, the absence of lesion on brain MRI was not associated with worse seizure outcomes in adult patients who underwent invasive intracranial monitoring followed by resection or thermal ablation.

Differential Cognitive Effects of Unilateral Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease.

OBJECTIVE: The aim of this study was to investigate the cognitive effects of unilateral directional versus ring subthalamic nucleus deep brain stimulation (STN DBS) in patients with advanced Parkinson's disease. METHODS: We examined 31 participants who underwent unilateral STN DBS (left n = 17; right n = 14) as part of an National Institutes of Health (NIH)-sponsored randomized, double-blind, crossover study contrasting directional versus ring stimulation. All participants received unilateral DBS implants in the hemisphere more severely affected by motor parkinsonism. Measures of cognition included verbal fluency, auditory-verbal memory, and response inhibition. We used mixed linear models to contrast the effects of directional versus ring stimulation and implant hemisphere on longitudinal cognitive function. RESULTS: Crossover analyses showed no evidence for group-level changes in cognitive performance related to directional versus ring stimulation. Implant hemisphere, however, impacted cognition in several ways. Left STN participants had lower baseline verbal fluency than patients with right implants (t [20.66 = -2.50, p = 0.02]). Verbal fluency declined after left (p = 0.013) but increased after right STN DBS (p < 0.001), and response inhibition was faster following right STN DBS (p = 0.031). Regardless of hemisphere, delayed recall declined modestly over time versus baseline (p = 0.001), and immediate recall was unchanged. INTERPRETATION: Directional versus ring STN DBS did not differentially affect cognition. Similar to prior bilateral DBS studies, unilateral left stimulation worsened verbal fluency performance. In contrast, unilateral right STN surgery increased performance on verbal fluency and response inhibition tasks. Our findings raise the hypothesis that unilateral right STN DBS in selected patients with predominant right brain motor parkinsonism could mitigate declines in verbal fluency associated with the bilateral intervention. ANN NEUROL 2024;95:1205-1219.

Applicant Perceptions of Postinterview Communication During the 2022 to 2023 Neurosurgery Recruitment Cycle: A Cross-Sectional Survey Study.

OBJECTIVES: To evaluate and describe neurosurgery applicant perceptions of the postinterview communication (PIC) process during the US residency match. METHODS: A voluntary and anonymous postmatch web-based survey was developed and sent to 209 candidates who applied to 1 academic neurosurgery practice during the 2022-2023 recruitment cycle, approximately 1 week following match day. Survey questions focused on their perceptions of and participation behaviors with PIC and how this impacted their final rank list. RESULTS: Seventy-eight (37.3%) of the 209 candidates responded to the survey. Sixty-four (84.2%) respondents reported submitting a letter of intent (LOI) to their number 1 ranked program. Sixty-one (82%) felt pressured to send a LOI to improve their rank status, fearing that it may harm them if they did not. Fifty-four (73.0%) respondents felt pressured to send an early LOI despite not seeing the program in person to communicate interest before programs certified their rank lists. Fourteen (18.9%) respondents agreed that a second look experience impacted their rank list enough to where they regretted an early LOI. Fifty-five (76.4%) respondents disagreed that second-look attendance had no impact on their rank status with a program. Fifty (71.4%) respondents agreed that PIC causes undue stress during the match process. Sixty-one (84.7%) respondents agreed that aspects of PIC require universal guidelines. CONCLUSIONS: This is the first study to describe the perceptions of PIC and behaviors of neurosurgery applicants during the US residency match process. Standardized PIC practices may help to ensure transparency and relieve stress for applicants during the match process.

Alternative patterns of deep brain stimulation in neurologic and neuropsychiatric disorders.

Deep brain stimulation (DBS) is a widely used clinical therapy that modulates neuronal firing in subcortical structures, eliciting downstream network effects. Its effectiveness is determined by electrode geometry and location as well as adjustable stimulation parameters including pulse width, interstimulus interval, frequency, and amplitude. These parameters are often determined empirically during clinical or intraoperative programming and can be altered to an almost unlimited number of combinations. Conventional high-frequency stimulation uses a continuous high-frequency square-wave pulse (typically 130-160 Hz), but other stimulation patterns may prove efficacious, such as continuous or bursting theta-frequencies, variable frequencies, and coordinated reset stimulation. Here we summarize the current landscape and potential clinical applications for novel stimulation patterns.

Differential cognitive effects of unilateral left and right subthalamic nucleus deep brain stimulation for Parkinson disease.

Objective: To investigate hemispheric effects of directional versus ring subthalamic nucleus (STN) deep brain stimulation (DBS) surgery on cognitive function in patients with advanced Parkinson's disease (PD). Methods: We examined 31 PD patients (Left STN n = 17; Right STN n = 14) who underwent unilateral subthalamic nucleus (STN) DBS as part of a NIH-sponsored randomized, cross-over, double-blind (ring vs directional) clinical trial. Outcome measures were tests of verbal fluency, auditory-verbal memory, and response inhibition. First, all participants were pooled together to study the effects of directional versus ring stimulation. Then, we stratified the groups by surgery hemisphere and studied the longitudinal changes in cognition post-unilateral STN DBS. Results: Relative to pre-DBS cognitive baseline performances, there were no group changes in cognition following unilateral DBS for either directional or ring stimulation. However, assessment of unilateral DBS by hemisphere revealed a different pattern. The left STN DBS group had lower verbal fluency than the right STN group (t(20.66 = -2.50, p = 0.02). Over a period of eight months post-DBS, verbal fluency declined in the left STN DBS group (p = 0.013) and improved in the right STN DBS group over time (p < .001). Similarly, response inhibition improved following right STN DBS (p = 0.031). Immediate recall did not significantly differ over time, nor was it affected by implant hemisphere, but delayed recall equivalently declined over time for both left and right STN DBS groups (left STN DBS p = 0.001, right STN DBS differ from left STN DBS p = 0.794). Conclusions: Directional and ring DBS did not differentially or adversely affect cognition over time. Regarding hemisphere effects, verbal fluency decline was observed in those who received left STN DBS, along with the left and right STN DBS declines in delayed memory. The left STN DBS verbal fluency decrement is consistent with prior bilateral DBS research, likely reflecting disruption of the basal-ganglia-thalamocortical network connecting STN and inferior frontal gyrus. Interestingly, we found an improvement in verbal fluency and response inhibition following right STN DBS. It is possible that unilateral STN DBS, particularly in the right hemisphere, may mitigate cognitive decline.

Surgically treatable adult epilepsy: a changing patient population. Experience from a level 4 epilepsy center.

OBJECTIVE: Invasive monitoring has long been utilized in the evaluation of patients for epilepsy surgery, providing localizing information to guide resection. Stereoelectroencephalography (SEEG) was introduced at the authors' level 4 epilepsy surgery program in 2013, with responsive neurostimulation (RNS) becoming available the following year. The authors sought to characterize patient demographics and epilepsy-related variables before and after SEEG introduction to understand whether differences emerged in their patient population. This information will be useful in understanding how SEEG, possibly in conjunction with RNS availability, may have changed practice patterns over time. METHODS: This is a retrospective cohort study of consecutive patients who underwent surgery for epilepsy from 2006 to 2018, comprising 7 years before and 5 years after the introduction of SEEG. The authors performed univariate analyses of patient characteristics and outcomes and used generalized estimating equations logistic regression for predictive analysis. RESULTS: A total of 178 patients were analyzed, with 109 patients in the pre-SEEG cohort and 69 patients in the post-SEEG cohort. In the post-SEEG cohort, more patients underwent invasive monitoring for suspected bilateral seizure onsets (40.6% vs 22.0%, p = 0.01) and extratemporal seizure onsets (68.1% vs 8.3%, p < 0.0001). The post-SEEG cohort had a higher proportion of patients with seizures arising from eloquent cortex (14.5% vs 0.9%, p < 0.001). Twelve patients underwent RNS insertion in the post-SEEG group versus none in the pre-SEEG group. Fewer patients underwent resection in the post-SEEG group (55.1% vs 96.3%, p < 0.0001), but there was no significant difference in rates of seizure freedom between cohorts for those patients having undergone a follow-up resection (53.1% vs 59.8%, p = 0.44). CONCLUSIONS: These findings demonstrate that more patients with suspected bilateral, eloquent, or extratemporal epilepsy underwent invasive monitoring after adoption of SEEG. This shift occurred coincident with the adoption of RNS, both of which likely contributed to increased patient complexity. The authors conclude that their practice now considers invasive monitoring for patients who likely would not previously have been candidates for surgical investigation and subsequent intervention.

Subcortical short-term plasticity elicited by deep brain stimulation.

OBJECTIVE: To investigate local short-term neuroplasticity elicited by subthalamic, thalamic, and pallidal deep brain stimulation (DBS) for movement disorders. METHODS: During DBS surgery, we delivered pairs of stimulus pulses with both circular and directional leads across 90 interstimulus intervals in 17 participants and recorded local field potentials from unused contacts on the implanted electrode array. We removed the stimulus artifact, validated the neural origin of the underlying signals, and examined short-term plasticity as a function of interstimulus interval and DBS target, using linear mixed effects models. RESULTS: DBS evokes short latency local field potentials that are readily detected with both circular and directional leads at all stimulation targets (0.31 ± 0.10 msec peak latency, mean ± SD). Peak amplitude, area, and latency are modified strongly by interstimulus interval (P < 0.001) and display absolute and relative refractory periods (0.56 ± 0.08 and 2.94 ± 1.05 msec, respectively). We also identified later oscillatory activity in the subthalamic-pallidal circuit (4.50 ± 1.11 msec peak latency) that displays paired pulse facilitation (present in 5/8 subthalamic, 4/5 pallidal, and 0/6 thalamic trajectories, P = 0.018, Fisher's exact test), and correlates with resting beta frequency power (P < 0.001), therapeutic DBS frequencies, and stimulation sites chosen later for therapy in the ambulatory setting (P = 0.031). INTERPRETATION: Paired DBS pulses synchronize local circuit electrophysiology and elicit short-term neuroplasticity in the subthalamic-pallidal circuit. Collectively, these responses likely represent the earliest detectable interaction between the DBS pulse and local neuronal tissue in humans. Evoked subcortical field potentials could serve as a predictive biomarker to guide the implementation of next-generation directional and adaptive stimulation devices.

Risk factors for wound-related complications after microvascular decompression.

Retrosigmoid craniotomy for microvascular decompression (MVD) has been traditionally performed via craniectomy. Various closure techniques have been described, yet factors associated with wound-related complications remain undetermined. Accordingly, herein, we sought to identify risk factors associated with wound-related complications after such procedures. An institutional retrospective case-control study was performed; outcomes of interest were cerebrospinal fluid (CSF) leak, wound dehiscence, wound infection, and pseudomeningocele. Univariate analysis was performed using Wilcoxon rank sum test for non-parametric continuous outcomes and chi-square test for categorical outcomes. Multivariate logistic regression was performed on binomial outcome variables. The study population included 197 patients who underwent MVD for trigeminal neuralgia (83.2%), hemifacial spasm (12.2%), vestibular nerve section (3.0%), and glossopharyngeal neuralgia (1.5%). The overall wound-related complication rate was 14.2% (n = 28), including twelve patients (6.1%) with CSF leak, ten patients (5.1%) with wound infection, ten patients (5.1%) with pseudomeningocele, and nine (4.6%) patients with wound dehiscence. Using multivariate logistic regression, preoperative anemia and current tobacco use were associated with significantly higher rates of complications (OR 6.01 and 4.58, respectively; p < 0.05), including CSF leak (OR 12.83 and 12.40, respectively, p < 0.05). Of note, use of synthetic bone substitute for cranioplasty was associated with a significantly lower rate of complications (OR 0.13, p < 0.01). Preoperative anemia and current tobacco use significantly increased, while synthetic bone substitute cranioplasty significantly decreased, odds of wound-related complications, the need for treatment, and CSF leaks. Additionally, higher BMI, longer operative duration, and prior radiosurgery may increase risk for wound-related complications.

Comparison of signal decomposition techniques for analysis of human cortical signals.

OBJECTIVE: Conventional neural signal analysis methods assume that features of interest are linear, time-invariant signals confined to well-delineated spectral bands. However, new evidence suggests that neural signals exhibit important non-stationary characteristics with ill-defined spectral distributions. These features pose a need for signal processing algorithms that can characterize temporal and spectral features of non-linear time series. This study compares the effectiveness of four algorithms in extracting neural information for use in decoding cortical signals: Fast Fourier Transform bandpass filtering (FFT), principal spectral component analysis (PSCA), wavelet analysis (WA), and empirical mode decomposition (EMD). APPROACH: Electrocorticographic signals were recorded from the motor and sensory cortex of two epileptic patients performing finger movements. Each signal processing algorithm was used to extract beta (10-30 Hz) and gamma (66-114 Hz) band power to detect thumb movement and decode finger flexions, respectively. Naïve-Bayes (NB), support vector machine (SVM), and linear discriminant analysis (LDA) classifiers using each signal were validated using leave-one-out cross-validation. MAIN RESULTS: Decoders using all four signal decompositions achieved above 90% average accuracy in finger movement detection using beta power. When decoding individual finger flexion using gamma, the PSCA NB classifiers achieved 78 ± 4% accuracy while FFT, WA, and EMD analysis achieved accuracies of 73 ± 8%, 68 ± 7%, and 62 ± 3% respectively, with similar results using SVM and LDA. SIGNIFICANCE: These results illustrate the relative levels of useful information contributed by each decomposition method in the case of finger movement decoding, which can inform the development of effective neural decoding pipelines. Further analyses could compare performance using more specific non-sinusoidal features, such as transients and phase-amplitude coupling.

Latency of subthalamic nucleus deep brain stimulation-evoked cortical activity as a potential biomarker for postoperative motor side effects.

OBJECTIVE: Here, we investigate whether cortical activation predicts motor side effects of deep brain stimulation (DBS) and whether these potential biomarkers have utility under general anesthesia. METHODS: We recorded scalp potentials elicited by DBS during surgery (n = 11), both awake and under general anesthesia, and in an independent ambulatory cohort (n = 8). Across a range of stimulus configurations, we measured the amplitude and timing of short- and long-latency response components and linked them to motor side effects. RESULTS: Regardless of anesthesia state, in both cohorts, DBS settings with capsular side effects elicited early responses with peak latencies clustering at <1 ms. This early response was preserved under anesthesia in all participants (11/11). In contrast, the long-latency components were suppressed completely in 6/11 participants. Finally, the latency of the earliest response could predict the presence of postoperative motor side effects both awake and under general anesthesia (84.8% and 75.8% accuracy, awake and under anesthesia, respectively). CONCLUSION: DBS elicits short-latency cortical activation, both awake and under general anesthesia, which appears to reveal interactions between the stimulus and the corticospinal tract. SIGNIFICANCE: Short-latency evoked cortical activity can potentially be used to aid both DBS lead placement and post-operative programming.

Robot-assisted stereoelectroencephalography exploration of the limbic thalamus in human focal epilepsy: implantation technique and complications in the first 24 patients.

OBJECTIVE: Despite numerous imaging studies highlighting the importance of the thalamus in a patient's surgical prognosis, human electrophysiological studies involving the limbic thalamic nuclei are limited. The objective of this study was to evaluate the safety and accuracy of robot-assisted stereotactic electrode placement in the limbic thalamic nuclei of patients with suspected temporal lobe epilepsy (TLE). METHODS: After providing informed consent, 24 adults with drug-resistant, suspected TLE undergoing evaluation with stereoelectroencephalography (SEEG) were enrolled in the prospective study. The trajectory of one electrode planned for clinical sampling of the operculoinsular cortex was modified to extend it to the thalamus, thereby preventing the need for additional electrode placement for research. The anterior nucleus of the thalamus (ANT) (n = 13) and the medial group of thalamic nuclei (MED) (n = 11), including the mediodorsal and centromedian nuclei, were targeted. The postimplantation CT scan was coregistered to the preoperative MR image, and Morel's thalamic atlas was used to confirm the accuracy of implantation. RESULTS: Ten (77%) of 13 patients in the ANT group and 10 (91%) of 11 patients in the MED group had electrodes accurately placed in the thalamic nuclei. None of the patients had a thalamic hemorrhage. However, trace asymptomatic hemorrhages at the cortical-level entry site were noted in 20.8% of patients, who did not require additional surgical intervention. SEEG data from all the patients were interpretable and analyzable. The trajectories for the ANT implant differed slightly from those of the MED group at the entry point-i.e., the precentral gyrus in the former and the postcentral gyrus in the latter. CONCLUSIONS: Using judiciously planned robot-assisted SEEG, the authors demonstrate the safety of electrophysiological sampling from various thalamic nuclei for research recordings, presenting a technique that avoids implanting additional depth electrodes or compromising clinical care. With these results, we propose that if patients are fully informed of the risks involved, there are potential benefits of gaining mechanistic insights to seizure genesis, which may help to develop neuromodulation therapies.

Subcortical Intermittent Theta-Burst Stimulation (iTBS) Increases Theta-Power in Dorsolateral Prefrontal Cortex (DLPFC).

INTRODUCTION: Cognitive symptoms from Parkinson's disease cause severe disability and significantly limit quality of life. Little is known about mechanisms of cognitive impairment in PD, although aberrant oscillatory activity in basal ganglia-thalamo-prefrontal cortical circuits likely plays an important role. While continuous high-frequency deep brain stimulation (DBS) improves motor symptoms, it is generally ineffective for cognitive symptoms. Although we lack robust treatment options for these symptoms, recent studies with transcranial magnetic stimulation (TMS), applying intermittent theta-burst stimulation (iTBS) to dorsolateral prefrontal cortex (DLPFC), suggest beneficial effects for certain aspects of cognition, such as memory or inhibitory control. While TMS is non-invasive, its results are transient and require repeated application. Subcortical DBS targets have strong reciprocal connections with prefrontal cortex, such that iTBS through the permanently implanted lead might represent a more durable solution. Here we demonstrate safety and feasibility for delivering iTBS from the DBS electrode and explore changes in DLPFC electrophysiology. METHODS: We enrolled seven participants with medically refractory Parkinson's disease who underwent DBS surgery targeting either the subthalamic nucleus (STN) or globus pallidus interna (GPi). We temporarily placed an electrocorticography strip over DLPFC through the DBS burr hole. After placement of the DBS electrode into either GPi (n = 3) or STN (n = 4), awake subjects rested quietly during iTBS (three 50-Hz pulses delivered at 5 Hz for 2 s, followed by 8 s of rest). We contrasted power spectra in DLPFC local field potentials during iTBS versus at rest, as well as between iTBS and conventional high-frequency stimulation (HFS). RESULTS: Dominant frequencies in DLPFC at rest varied among subjects and along the subdural strip electrode, though they were generally localized in theta (3-8 Hz) and/or beta (10-30 Hz) ranges. Both iTBS and HFS were well-tolerated and imperceptible. iTBS increased theta-frequency activity more than HFS. Further, GPi stimulation resulted in significantly greater theta-power versus STN stimulation in our sample. CONCLUSION: Acute subcortical iTBS from the DBS electrode was safe and well-tolerated. This novel stimulation pattern delivered from the GPi may increase theta-frequency power in ipsilateral DLPFC. Future studies will confirm these changes in DLPFC activity during iTBS and evaluate whether they are associated with improvements in cognitive or behavioral symptoms from PD.

Percutaneous Trigeminal Nerve Stimulation for Persistent Idiopathic Facial Pain: A Case Series.

BACKGROUND: Persistent idiopathic facial pain (PIFP) can be refractory to conventional management approaches. Neuromodulatory procedures such as percutaneous trigeminal nerve stimulation (TNS) have been sparsely reported as potential treatment options for amelioration of debilitating refractory pain associated with PIFP. The present study investigated the use of percutaneous TNS in a series of patients with PIFP to evaluate the potential efficacy of pain relief. METHODS: We performed a retrospective medical record review for patients with PIFP who had presented to Emory University Hospital and had undergone TNS for PIFP. The primary outcomes were postoperative pain using the visual analog scale (VAS) for pain and morphine equivalent use. Descriptive statistics, mean ± standard deviation, and the nonparametric Wilcoxon sign rank test were used, as appropriate. A P value of <0.05 was considered statistically significant. RESULTS: A total of 23 patients underwent percutaneous TNS for PIFP. Of the 23 patients, 20 (86.9%) reported a >50% improvement after trial stimulation. Of the patients who had received permanent TNS implants, 13 of 17 (76.4%) had VAS scores available. For these patients, the mean preoperative VAS score had decreased from 5.69 ± 2.09 to 0.15 ± 0.55 postoperatively. The VAS scores displayed a statistically significant decrease after TNS (P = 0.0014). A subset of 9 patients with available data also demonstrated a significant reduction in morphine equivalent use after TNS (before, 50.54 ± 51.30; after, 25.83 ± 33.58; P = 0.048). CONCLUSION: The results from the present study have indicated that percutaneous stimulation of the trigeminal nerve is efficacious in the treatment of PIFP and can significantly decrease morphine equivalent use. Further longitudinal studies are required to validate our results.

A simple, inexpensive method for subcortical stereotactic targeting in nonhuman primates.

BACKGROUND: Many current neuroscience studies in large animal models have focused on recordings from cortical structures. While sufficient for analyzing sensorimotor systems, many processes are modulated by subcortical nuclei. Large animal models, such as nonhuman primates (NHP), provide an optimal model for studying these circuits, but the ability to target subcortical structures has been hampered by lack of a straightforward approach to targeting. NEW METHOD: Here we present a method of subcortical targeting in NHP that uses MRI-compatible titanium screws as fiducials. The in vivo study used a cellular marker for histologic confirmation of accuracy. RESULTS: Histologic results are presented showing a cellular stem cell marker within targeted structures, with mean errors ± standard deviations (SD) of 1.40 ±â€¯1.19 mm in the X-axis and 0.9 ±â€¯0.97 mm in the Z-axis. The Y-axis errors ± SD ranged from 1.5 ±â€¯0.43 to 4.2 ±â€¯1.72 mm. COMPARISON WITH EXISTING METHODS: This method is easy and inexpensive, and requires no fabrication of equipment, keeping in mind the goal of optimizing a technique for implantation or injection into multiple interconnected areas. CONCLUSION: This procedure will enable primate researchers to target deep, subcortical structures more precisely in animals of varying ages and weights.

Robust tactile sensory responses in finger area of primate motor cortex relevant to prosthetic control.

OBJECTIVE: Challenges in improving the performance of dexterous upper-limb brain-machine interfaces (BMIs) have prompted renewed interest in quantifying the amount and type of sensory information naturally encoded in the primary motor cortex (M1). Previous single unit studies in monkeys showed M1 is responsive to tactile stimulation, as well as passive and active movement of the limbs. However, recent work in this area has focused primarily on proprioception. Here we examined instead how tactile somatosensation of the hand and fingers is represented in M1. APPROACH: We recorded multi- and single units and thresholded neural activity from macaque M1 while gently brushing individual finger pads at 2 Hz. We also recorded broadband neural activity from electrocorticogram (ECoG) grids placed on human motor cortex, while applying the same tactile stimulus. MAIN RESULTS: Units displaying significant differences in firing rates between individual fingers (p < 0.05) represented up to 76.7% of sorted multiunits across four monkeys. After normalizing by the number of channels with significant motor finger responses, the percentage of electrodes with significant tactile responses was 74.9% ± 24.7%. No somatotopic organization of finger preference was obvious across cortex, but many units exhibited cosine-like tuning across multiple digits. Sufficient sensory information was present in M1 to correctly decode stimulus position from multiunit activity above chance levels in all monkeys, and also from ECoG gamma power in two human subjects. SIGNIFICANCE: These results provide some explanation for difficulties experienced by motor decoders in clinical trials of cortically controlled prosthetic hands, as well as the general problem of disentangling motor and sensory signals in primate motor cortex during dextrous tasks. Additionally, examination of unit tuning during tactile and proprioceptive inputs indicates cells are often tuned differently in different contexts, reinforcing the need for continued refinement of BMI training and decoding approaches to closed-loop BMI systems for dexterous grasping.

Influence of Intracranial Air on Electrode Position and Clinical Outcomes following Deep Brain Stimulation for Parkinson's Disease.

BACKGROUND: The introduction of intracranial air during deep brain stimulation (DBS) surgery is believed to negatively impact targeting accuracy and clinical outcomes. OBJECTIVE: To quantify the relationship between intracranial air (ICA) volumes, targeting accuracy, and clinical outcomes in patients undergoing subthalamic nucleus (STN) DBS for Parkinson's disease. METHODS: ICA in 73 consecutive STN DBS cases (146 leads) was measured by high-resolution CT and correlated with proximal lead bowing, electrode displacement, targeting accuracy, and clinical outcomes at 6 and 12 months. RESULTS: There was a statistically significant correlation of ICA volume (mean ± SEM: 21.3 ± 13.7 cm3) and proximal lead bowing (2.8 ± 1.4 mm, r = 0.34, p = 0.01). There was no significant correlation of ICA with targeting error (2.0 ± 1.2 mm), distal contact deviation (1.2 ± 0.7 mm), motor Movement Disorder Society-Unified Parkinson's Disease Rating Scale Part III improvement at 6 months (42.3 ± 4.5%) or 12 months (30.3 ± 7.7%), or dopaminergic medication reduction at 6 months (44.7± 4.2%) or 12 months (32.9 ± 5.9%). Comparison of top and bottom ICA quintile extremes also revealed no differences in these measures. CONCLUSIONS: Though the proximal DBS lead bends in association with ICA, movement of the distal contact, targeting error, and clinical outcomes are not affected by ICA. This unexpected finding is maintained at ICA quintile extremes.

Ruptured pediatric cerebellopontine angle epidermoid cyst: a case report detailing radiographic evolution and clinical course.

Epidermoid cysts (ECs) are uncommon pediatric tumors that often occur in the cerebellopontine angle. Although cyst rupture is a recognized complication, the radiographic evolution of an EC following rupture and the resultant parenchymal brainstem edema have not been reported. The authors present the case of a 13-year-old female with a newly diagnosed cerebellopontine angle EC who presented with worsening headaches, photophobia, and emesis. Magnetic resonance imaging demonstrated significant pericystic brainstem edema and mass effect with effacement of the fourth ventricle. Refractory symptoms prompted repeat imaging, revealing cyst enlargement and dense rim enhancement. Resection of the EC resolved both her symptoms and the brainstem edema. This case documents the radiographic evolution of EC rupture and subsequent clinical course.

Patient misconceptions concerning lumbar spondylosis diagnosis and treatment.

OBJECT Patient outcome measures are becoming increasingly important in the evaluation of health care quality and physician performance. Of the many novel measures currently being explored, patient satisfaction and other subjective measures of patient experience are among the most heavily weighted. However, these subjective measures are strongly influenced by a number of factors, including patient demographics, level of understanding of the disorder and its treatment, and patient expectations. In the present study, patients referred to a neurosurgery clinic for degenerative spinal disorders were surveyed to determine their understanding of lumbar spondylosis diagnosis and treatment. METHODS A multiple-choice, 6-question survey was distributed to all patients referred to a general neurosurgical spine clinic at a tertiary care center over a period of 11 months as a quality improvement initiative to assist the provider with individualized patient counseling. The survey consisted of questions designed to assess patient understanding of the role of radiological imaging in the diagnosis and treatment of low-back and leg pain, and patient perception of the indications for surgical compared with conservative management. Demographic data were also collected. RESULTS A total of 121 surveys were included in the analysis. More than 50% of the patients indicated that they would undergo spine surgery based on abnormalities found on MRI, even without symptoms; more than 40% of patients indicated the same for plain radiographs. Similarly, a large proportion of patients (33%) believed that back surgery was more effective than physical therapy in the treatment of back pain without leg pain. Nearly one-fifth of the survey group (17%) also believed that back injections were riskier than back surgery. There were no significant differences in survey responses among patients with a previous history of spine surgery compared with those without previous spine surgery. CONCLUSIONS These results show that a surprisingly high percentage of patients have misconceptions regarding the diagnosis and treatment of lumbar spondylosis, and that these misconceptions persist in patients with a history of spine surgery. Specifically, patients overemphasize the value of radiological studies and have mixed perceptions of the relative risk and effectiveness of surgical intervention compared with more conservative management. These misconceptions have the potential to alter patient expectations and decrease satisfaction, which could negatively impact patient outcomes and subjective valuations of physician performance. While these results are preliminary, they highlight a need for improved communication and patient education during surgical consultation for lumbar spondylosis.