Brett E. Youngerman

Motor deficits correlate with resting state motor network connectivity in patients with brain tumours

While a tumour in or abutting primary motor cortex leads to motor weakness, how tumours elsewhere in the frontal or parietal lobes affect functional connectivity in a weak patient is less clear. We hypothesized that diminished functional connectivity in a distributed network of motor centres would correlate with motor weakness in subjects with brain masses. Furthermore, we hypothesized that interhemispheric connections would be most vulnerable to subtle disruptions in functional connectivity. We used task-free functional magnetic resonance imaging connectivity to probe motor networks in control subjects and patients with brain tumours (n = 22). Using a control dataset, we developed a method for automated detection of key nodes in the motor network, including the primary motor cortex, supplementary motor area, premotor area and superior parietal lobule, based on the anatomic location of the hand-motor knob in the primary motor cortex. We then calculated functional connectivity between motor network nodes in control subjects, as well as patients with and without brain masses. We used this information to construct weighted, undirected graphs, which were then compared to variables of interest, including performance on a motor task, the grooved pegboard. Strong connectivity was observed within the identified motor networks between all nodes bilaterally, and especially between the primary motor cortex and supplementary motor area. Reduced connectivity was observed in subjects with motor weakness versus subjects with normal strength (P < 0.001). This difference was driven mostly by decreases in interhemispheric connectivity between the primary motor cortices (P < 0.05) and between the left primary motor cortex and the right premotor area (P < 0.05), as well as other premotor area connections. In the subjects without motor weakness, however, performance on the grooved pegboard did not relate to interhemispheric connectivity, but rather was inversely correlated with connectivity between the left premotor area and left supplementary motor area, for both the left and the right hands (P < 0.01). Finally, two subjects who experienced severe weakness following surgery for their brain tumours were followed longitudinally, and the subject who recovered showed reconstitution of her motor network at follow-up. The subject who was persistently weak did not reconstitute his motor network. Motor weakness in subjects with brain tumours that do not involve primary motor structures is associated with decreased connectivity within motor functional networks, particularly interhemispheric connections. Motor networks become weaker as the subjects become weaker, and may become strong again during motor recovery.

Neuroanatomical Characteristics Associated With Response to Dorsal Anterior Cingulotomy for Obsessive-Compulsive Disorder

IMPORTANCE Approximately 10% of patients with obsessive-compulsive disorder (OCD) have symptoms that are refractory to pharmacologic and cognitive-behavioral therapies. Neurosurgical interventions can be effective therapeutic options in these patients, but not all individuals respond. The mechanisms underlying this response variability are poorly understood. OBJECTIVE To identify neuroanatomical characteristics on preoperative imaging that differentiate responders from nonresponders to dorsal anterior cingulotomy, a neurosurgical lesion procedure used to treat refractory OCD. DESIGN, SETTING, AND PARTICIPANTS We retrospectively analyzed preoperative T1 and diffusion magnetic resonance imaging sequences from 15 patients (9 men and 6 women) who underwent dorsal anterior cingulotomy. Eight of the 15 patients (53%) responded to the procedure. MAIN OUTCOMES AND MEASURES We used voxel-based morphometry (VBM) and diffusion tensor imaging to identify structural and connectivity variations that could differentiate eventual responders from nonresponders. The VBM and probabilistic tractography metrics were correlated with clinical response to the cingulotomy procedure as measured by changes in the Yale-Brown Obsessive Compulsive Scale score. RESULTS Voxel-based morphometry analysis revealed a gray matter cluster in the right anterior cingulate cortex, anterior to the eventual lesion, for which signal strength correlated with poor response (P = .017). Decreased gray matter in this region of the dorsal anterior cingulate cortex predicted improved response (mean [SD] gray matter partial volume for responders vs nonresponders, 0.47 [0.03] vs 0.66 [0.03]; corresponding to mean Yale-Brown Obsessive Compulsive Scale score change, -60% [19] vs -11% [9], respectively). Hemispheric asymmetry in connectivity between the eventual lesion and the caudate (for responders vs nonresponders, mean [SD] group laterality for individual lesion seeds, -0.79 [0.18] vs -0.08 [0.65]; P = .04), putamen (-0.55 [0.35] vs 0.50 [0.33]; P = .001), thalamus (-0.82 [0.19] vs 0.41 [0.24]; P = .001), pallidum (-0.78 [0.18] vs 0.43 [0.48]; P = .001), and hippocampus (-0.66 [0.33] vs 0.33 [0.18]; P = .001) also correlated significantly with clinical response, with increased right-sided connectivity predicting greater response. CONCLUSIONS AND RELEVANCE We identified features of anterior cingulate cortex structure and connectivity that predict clinical response to dorsal anterior cingulotomy for refractory OCD. These results suggest that the variability seen in individual responses to a highly consistent, stereotyped procedure may be due to neuroanatomical variation in the patients. Furthermore, these variations may allow us to predict which patients are most likely to respond to cingulotomy, thereby refining our ability to individualize this treatment for refractory psychiatric disorders.

Endovascular treatment strategies for acute ischemic stroke.

The limitations of intravenous thrombolysis therapy have paved the way for the development of novel endovascular technologies for use in the setting of acute stroke. These technologies range from direct intraarterial thrombolysis to various thrombus disruption or retrieval devices to angioplasty and stenting. The tools in the armamentarium of the neuroendovascular interventionalist enable fast, effective revascularization to be offered to a wider population of patients that may otherwise have few therapeutic options available to them. In this paper, we review the current state-of-the-art in neuroendovascular intervention for acute ischemic stroke. Particular emphasis is placed on delineating the indications and outcomes for use of these various technologies.

Causes and Timing of Unplanned Early Readmission After Neurosurgery.

BACKGROUND Reducing the rate of 30-day hospital readmission has become a priority in healthcare quality improvement policy, with a focus on better characterizing the reasons for unplanned readmission. In neurosurgery, however, peer-reviewed analyses describing the patterns of readmission have been limited in their number and generalizability. OBJECTIVE To determine the incidence, timing, and causes of 30-day readmission after neurosurgical procedures. METHODS We conducted a retrospective longitudinal study from 2009 to 2012 using the Statewide Planning And Research Cooperative System, which collects patient-level details for all admissions and discharges within New York. We identified patients readmitted within 30 days of initial discharge. The rate of, reasons for, and time to readmission were determined overall and within 4 subgroups: craniotomies, cranial surgery without craniotomy, spine, and neuroendovascular procedures. RESULTS There were 163 743 index admissions, of whom 14 791 (9.03%) were readmitted. The most common reasons for unplanned readmission were infection (29.52%) and medical complications (19.22%). Median time to readmission was 11 days, with hemorrhagic strokes and seizures occurring earlier, and medical complications and infections occurring later. Readmission rates were highest among patients undergoing cerebrospinal fluid shunt revision and malignant tumor resection (15.57%-22.60%). Spinal decompressions, however, accounted for the largest volume of readmissions (33.13%). CONCLUSION Many readmissions may be preventable and occur at predictable time intervals. The causes and timing of readmission vary significantly across neurosurgical subgroups. Future studies should focus on detecting specific complications in select cohorts at predefined time points, which may allow for interventions to lower costs and reduce patient morbidity. ABBREVIATIONS CSF, cerebrospinal fluidIQR, interquartile rangeSPARCS, Statewide Planning And Research Cooperative System.

A decade of emerging indications: deep brain stimulation in the United States.

OBJECTIVE Deep brain stimulation (DBS) is an emerging treatment option for an expanding set of neurological and psychiatric diseases. Despite growing enthusiasm, the patterns and implications of this rapid adoption are largely unknown. National trends in DBS surgery performed for all indications between 2002 and 2011 are reported. METHODS Using a national database of hospital discharges, admissions for DBS for 14 indications were identified and categorized as either FDA approved, humanitarian device exempt (HDE), or emerging. Trends over time were examined, differences were analyzed by univariate analyses, and outcomes were analyzed by hierarchical regression analyses. RESULTS Between 2002 and 2011, there were an estimated 30,490 discharges following DBS for approved indications, 1647 for HDE indications, and 2014 for emerging indications. The volume for HDE and emerging indications grew at 36.1% annually in comparison with 7.0% for approved indications. DBS for emerging indications occurred at hospitals with more neurosurgeons and neurologists locally, but not necessarily at those with the highest DBS caseloads. Patients treated for HDE and emerging indications were younger with lower comorbidity scores. HDE and emerging indications were associated with greater rates of reported complications, longer lengths of stay, and greater total costs. CONCLUSIONS DBS for HDE and emerging indications underwent rapid growth in the last decade, and it is not exclusively the most experienced DBS practitioners leading the charge to treat the newest indications. Surgeons may be selecting younger and healthier patients for their early experiences. Differences in reported complication rates warrant further attention and additional costs should be anticipated as surgeons gain experience with new patient populations and targets.

Long-term growth and alignment after occipitocervical and atlantoaxial fusion with rigid internal fixation in young children

OBJECT The long-term consequences of atlantoaxial (AA) and occipitocervical (OC) fusion and instrumentation in young children are unknown. Anecdotal reports have raised concerns regarding altered growth and alignment of the cervical spine after surgical intervention. The purpose of this study was to determine the long-term effects of these surgeries on the growth and alignment of the maturing spine. METHODS A multiinstitutional retrospective chart review was conducted for patients less than or equal to 6 years of age who underwent OC or AA fusion with rigid instrumentation at 9 participating centers. All patients had at least 3 years of clinical and radiographic follow-up data and radiographically confirmed fusion. Preoperative, immediate postoperative, and most recent follow-up radiographs and/or CT scans were evaluated to assess changes in spinal growth and alignment. RESULTS Forty children (9 who underwent AA fusion and 31 who underwent OC fusion) were included in the study (mean follow-up duration 56 months). The mean vertical growth over the fused levels in the AA fusion patients represented 30% of the growth of the cervical spine (range 10%-50%). Three different vertical growth patterns of the fusion construct developed among the 31 OC fusion patients during the follow-up period: 1) 16 patients had substantial growth (13%-46% of the total growth of the cervical spine); 2) 9 patients had no meaningful growth; and 3) 6 patients, most of whom presented with a distracted atlantooccipital dislocation, had a decrease in the height of the fused levels (range 7-23 mm). Regarding spinal alignment, 85% (34/40) of the patients had good alignment at follow-up, with straight or mildly lordotic cervical curvatures. In 1 AA fusion patient (11%) and 5 OC fusion patients (16%), we observed new hyperlordosis (range 43°-62°). There were no cases of new kyphosis or swan-neck deformity, evidence of subaxial instability, or unintended subaxial fusion. No preoperative predictors of these growth patterns or alignment were evident. CONCLUSIONS These results demonstrate that most young children undergoing AA and OC fusion with rigid internal fixation continue to have good cervical alignment and continued growth within the fused levels during a prolonged follow-up period. However, some variability in vertical growth and alignment exists, highlighting the need to continue close long-term follow-up.

Frontal Networks Associated With Command Following After Hemorrhagic Stroke

Background and Purpose— Level of consciousness is frequently assessed by command-following ability in the clinical setting. However, it is unclear what brain circuits are needed to follow commands. We sought to determine what networks differentiate command following from noncommand following patients after hemorrhagic stroke. Methods— Structural MRI, resting-state functional MRI, and electroencephalography were performed on 25 awake and unresponsive patients with acute intracerebral and subarachnoid hemorrhage. Structural injury was assessed via volumetric T1-weighted MRI analysis. Functional connectivity differences were analyzed against a template of standard resting-state networks. The default mode network (DMN) and the task-positive network were investigated using seed-based functional connectivity. Networks were interrogated by pairwise coherence of electroencephalograph leads in regions of interest defined by functional MRI. Results— Functional imaging of unresponsive patients identified significant differences in 6 of 16 standard resting-state networks. Significant voxels were found in premotor cortex, dorsal anterior cingulate gyrus, and supplementary motor area. Direct interrogation of the DMN and task-positive network revealed loss of connectivity between the DMN and the orbitofrontal cortex and new connections between the task-positive network and DMN. Coherence between electrodes corresponding to right executive network and visual networks was also decreased in unresponsive patients. Conclusions— Resting-state functional MRI and electroencephalography coherence data support a model in which multiple, chiefly frontal networks are required for command following. Loss of DMN anticorrelation with task-positive network may reflect a loss of inhibitory control of the DMN by motor-executive regions. Frontal networks should thus be a target for future investigations into the mechanism of responsiveness in the intensive care unit environment.

Features and timing of the response of single neurons to novelty in the substantia nigra

Substantia nigra neurons are known to play a key role in normal cognitive processes and disease states. While animal models and neuroimaging studies link dopamine neurons to novelty detection, this has not been demonstrated electrophysiologically in humans. We used single neuron extracellular recordings in awake human subjects undergoing surgery for Parkinson disease to characterize the features and timing of this response in the substantia nigra. We recorded 49 neurons in the substantia nigra. Using an auditory oddball task, we showed that they fired more rapidly following novel sounds than repetitive tones. The response was biphasic with peaks at approximately 250 ms, comparable to that described in primate studies, and a second peak at 500 ms. This response was primarily driven by slower firing neurons as firing rate was inversely correlated to novelty response. Our data provide human validation of the purported role of dopamine neurons in novelty detection and suggest modifications to proposed models of novelty detection circuitry.

Laser ablation is effective for temporal lobe epilepsy with and without mesial temporal sclerosis if hippocampal seizure onsets are localized by stereoelectroencephalography

Selective laser amygdalohippocampotomy (SLAH) using magnetic resonance–guided laser interstitial thermal therapy (MRgLITT) is emerging as a treatment option for drug‐resistant mesial temporal lobe epilepsy (MTLE). SLAH is less invasive than open resection, but there are limited series reporting its safety and efficacy, particularly in patients without clear evidence of mesial temporal sclerosis (MTS).

Making Milestones: Development and Implementation of a Formal Socioeconomic Curriculum in a Neurosurgical Residency Training Program.

BACKGROUND Improved training in the socioeconomic aspects of medicine is a priority of the Accreditation Council for Graduate Medical Education and the American Board of Neurological Surgeons. There is evidence that young neurosurgeons feel ill equipped in these areas and that additional education would improve patient care. OBJECTIVE To present our experience with the introduction of a succinct but formal socioeconomic training course to the residency curriculum at our institution. METHODS A monthly series of twelve 1-hour interactive modules was designed to address the pertinent Accreditation Council for Graduate Medical Education-American Board of Neurological Surgeons outcomes-based educational milestones. Slide-based lectures provided a comprehensive overview of social, legal, and business issues, and a monthly forum for open discussion allowed residents to draw on their applied experience. Residents took a 20-question pre- and postcourse knowledge assessment, as well as feedback surveys at 6 and 12 months. RESULTS Residents were able to participate in the lectures, with an overall attendance rate of 91%. Residents felt that the course goals and objectives were well defined and communicated (4.88/5) and rated highly the content, quality, and relevance of the lectures (4.94/5). Performance on the knowledge assessment improved from 58% to 66%. CONCLUSION Our experience demonstrates the feasibility of including a formal socioeconomic course in neurosurgical residency training with positive resident feedback and achievement of outcomes-based milestones. Extension to a 2-year curriculum cycle may allow the course to cover more material without compromising other residency training goals. Online modules should also be explored to allow for wider and more flexible participation. ABBREVIATIONS ABNS, American Board of Neurological SurgeonsACGME, Accreditation Council for Graduate Medical Education.