Role of Functional neurosurgery in Improving Patient Outcomes in Epilepsy, Movement Disorders, and Chronic Pain.

Functional neurosurgery encompasses surgical procedures geared towards treating movement disorders (such as Parkinson's disease and essential tremor), drug-resistant epilepsy, and various types of pain disorders. It is one of the most rapidly expanding fields within neurosurgery and utilizes both traditional open surgical methods such as open temporal lobectomy for epilepsy as well as neuromodulation-based treatments such as implanting brain or nerve stimulation devices. This review outlines the role functional neurosurgery plays in treatment of epilepsy, movement disorders, and pain, and how it is being implemented at the University of Missouri by the Department of Neurosurgery.

More widespread and rigid neuronal representation of reward expectation underlies impulsive choices.

Impulsive choices prioritize smaller, more immediate rewards over larger, delayed, or potentially uncertain rewards. Impulsive choices are a critical aspect of substance use disorders and maladaptive decision-making across the lifespan. Here, we sought to understand the neuronal underpinnings of expected reward and risk estimation on a trial-by-trial basis during impulsive choices. To do so, we acquired electrical recordings from the human brain while participants carried out a risky decision-making task designed to measure choice impulsivity. Behaviorally, we found a reward-accuracy tradeoff, whereby more impulsive choosers were more accurate at the task, opting for a more immediate reward while compromising overall task performance. We then examined how neuronal populations across frontal, temporal, and limbic brain regions parametrically encoded reinforcement learning model variables, namely reward and risk expectation and surprise, across trials. We found more widespread representations of reward value expectation and prediction error in more impulsive choosers, whereas less impulsive choosers preferentially represented risk expectation. A regional analysis of reward and risk encoding highlighted the anterior cingulate cortex for value expectation, the anterior insula for risk expectation and surprise, and distinct regional encoding between impulsivity groups. Beyond describing trial-by-trial population neuronal representations of reward and risk variables, these results suggest impaired inhibitory control and model-free learning underpinnings of impulsive choice. These findings shed light on neural processes underlying reinforced learning and decision-making in uncertain environments and how these processes may function in psychiatric disorders.

Chronic intracranial recordings after resection for epilepsy reveal a "running down" of epileptiform activity.

We describe an electrical "running down" phenomenon and also a consistent spectral change (in the aperiodic component of the power spectrum) derived from chronic interictal electrocorticography (ECoG) after surgery in a patient with drug-resistant epilepsy. These data were recorded using a closed-loop neurostimulation system that was implanted after resection. The patient has been seizure-free for 2.5 years since resection without requiring the neurostimulator to be turned on to stimulate. Concurrently, there was an exponential decrease in the number of epileptiform electrographic detections recorded by the device, particularly over the first 26 weeks, indicative of an electrical running down phenomenon as the brain adapted to an extended period of seizure freedom. We also find that the aperiodic exponent of the power spectrum gradually decreases over time. The aperiodic component of intracranial ECoG may represent a novel marker of epileptogenicity, independent of seizures.

Natural history of pituitary carcinoma with metastasis to the cervical spine: illustrative case.

BACKGROUND: Pituitary carcinoma is a rare tumor of the adenohypophysis with noncontiguous craniospinal dissemination and/or systemic metastases. Given the rarity of this malignancy, there is limited knowledge and consensus regarding its natural history, prognosis, and optimal treatment. OBSERVATIONS: The authors present the case of a 46-year-old woman initially treated with invasive prolactin-secreting pituitary macroadenoma who developed metastatic disease of the cervical spine 6 years later. The patient presented with acutely worsening compressive cervical myelopathy and required posterior cervical decompression, tumor resection, and instrumented arthrodesis for posterolateral fusion. LESSONS: This case underscores the importance of long-term monitoring of hormone levels and having a high clinical suspicion for metastatic disease to the spine in patients presenting with acute myelopathy or radiculopathy in the setting of previously treated invasive secreting pituitary adenoma.

Using chronic recordings from a closed-loop neurostimulation system to capture seizures across multiple thalamic nuclei.

We report the case of a patient with unilateral diffuse frontotemporal epilepsy in whom we implanted a responsive neurostimulation system with leads spanning the anterior and centromedian nucleus of the thalamus. During chronic recording, ictal activity in the centromedian nucleus consistently preceded the anterior nucleus, implying a temporally organized seizure network involving the thalamus. With stimulation, the patient had resolution of focal impaired awareness seizures and secondarily generalized seizures. This report describes chronic recordings of seizure activity from multiple thalamic nuclei within a hemisphere and demonstrates the potential efficacy of closed-loop neurostimulation of multiple thalamic nuclei to control seizures.

Evaluating the concordance of functional MRI-based language lateralization and Wada testing in epilepsy patients: A single-center analysis.

BACKGROUND: For patients with drug-resistant epilepsy, surgery may be effective in controlling their disease. Surgical evaluation may involve localization of the language areas using functional magnetic resonance imaging (fMRI) or Wada testing. We evaluated the accuracy of task-based fMRI versus Wada-based language lateralization in a cohort of our epilepsy patients. METHODS: In a single-center, retrospective analysis, we identified patients with medically intractable epilepsy who participated in presurgical language mapping (n = 35) with fMRI and Wada testing. Demographic variables and imaging metrics were obtained. We calculated the laterality index (LI) from task-evoked fMRI activation maps across language areas during auditory and reading tasks to determine lateralization. Possible scores for LI range from -1 (strongly left-hemisphere dominant) to 1 (strongly right-hemisphere dominant). Concordance between fMRI and Wada was estimated using Cohen's Kappa coefficient. Association between the LI scores from the auditory and reading tasks was tested using Spearman's rank correlation coefficient. RESULTS: The fMRI-based laterality indices were concordant with results from Wada testing in 91.4% of patients during the reading task (κ = .55) and 96.9% of patients during the auditory task (κ = .79). The mean LIs for the reading and auditory tasks were -0.52 ± 0.43 and -0.68 ± 0.42, respectively. The LI scores for the language and reading tasks were strongly correlated, r(30) = 0.57 (p = 0.001). CONCLUSION: Our findings suggest that fMRI is generally an accurate, low-risk alternative to Wada testing for language lateralization. However, when fMRI indicates atypical language lateralization (e.g., bilateral dominance), patients may benefit from subsequent Wada testing or intraoperative language mapping.

Outcomes using linear accelerator stereotactic radiosurgery for the treatment of trigeminal neuralgia: A single-center, retrospective study.

Background: Linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) treatment of trigeminal neuralgia (TN) may have similar efficacy to Gamma Knife SRS (GK-SRS), but the preponderance of data comes from patients treated with GK-SRS. Our objective was to analyze the outcomes for LINAC-based treatment of TN in patients at our institution. Methods: We retrospectively analyzed data for patients who underwent LINAC-based SRS for TN from 2006 to 2018. Data were collected from the patients' medical records. Nonparametric statistics were used for the analysis. Results: Of the 41 patients treated with LINAC-based SRS (typically 90 Gy dosed using a 4 mm collimator for one fraction) during that time, follow-up data of >3 weeks post-SRS were available for 32 patients. The median pretreatment Barrow Neurological Institute (BNI) pain score was 5 (range 4-5). The follow-up period ranged from 0.9 to 113.2 months (median 5 months). There was significant improvement in postradiation BNI pain score (P < 0.001), with 23 (72%) patients who improved to a BNI pain score of 1-3. One patient had bothersome hypoesthesia postradiation. Approximately 38% of patients who had initial pain control had recurrence of symptoms (BNI > 3). Survival analysis showed a median time to pain recurrence of 30 months. There was no relationship between prior microvascular decompression (MVD) surgery and change in BNI pain score pre- to posttreatment. Conclusion: The results demonstrate that LINAC-based SRS is an effective means to treat TN. Prior MVD surgery did not affect efficacy of SRS in lowering the BNI score from pre- to posttreatment in this patient cohort.

Cranio-Orbital Approach for Single-Stage En Bloc Resection of Optic Nerve Glioma: Technical Note.

BACKGROUND AND IMPORTANCE: There is no consensus on the optimal surgical approach for managing optic nerve gliomas. For solely intraorbital tumors, a single-stage lateral orbitotomy approach for resection may be performed, but when the nerve within the optic canal is affected, two-stage cranial and orbital approaches are often used. The authors describe their technique to safely achieve aggressive nerve resection to minimize the probability of recurrence that might affect the optic tracts, optic chiasm, and contralateral optic nerve. CLINICAL PRESENTATION: A 28-yr-old woman presented with painless progressive vision loss, resulting in blindness. The second of 2 transorbital biopsies was diagnostic and consistent with low-grade glioma. The lesion continued to grow on serial imaging. The patient was offered a globe-sparing operative approach, with aggressive resection of the lesion to minimize the probability of tumor recurrence, which could possibly affect vision in her contralateral eye. The patient did well postoperatively, with clean tumor margins on pathological analysis and no evidence of residual on imaging. On postoperative examination, she had a mild ptosis, which was nearly resolved at her 6-wk outpatient follow-up. CONCLUSION: This aggressive single-stage en bloc resection of an optic nerve glioma can achieve excellent tumor margins and preservation of extraocular muscle function.

Preoperative Magnetic Resonance Imaging Abnormalities Predict Symptomatic Adjacent Segment Degeneration After Anterior Cervical Discectomy and Fusion.

Introduction Anterior cervical discectomy and fusions (ACDFs) are generally limited to the levels causing neurological symptoms, but whether adjacent asymptomatic levels should be included if they demonstrate severe radiographic degeneration is a matter of controversy. We evaluated whether asymptomatic preoperative magnetic resonance imaging (MRI) abnormalities at adjacent levels were predictive of reoperation for symptomatic adjacent-segment degeneration (ASD) after the initial ACDF. Methods We reviewed patients treated with ACDF in 2000-2010 who had MRIs preoperatively and again ≥3 years after the index surgery to evaluate new neurological symptoms. Patients were stratified by ASD severity score, calculated based on MRI features. The associations between preoperative ASD severity score and reoperation for ASD were evaluated with logistic and Cox regressions after adjusting for covariates. Results Of 1038 patients who underwent ACDF, 96 (9%) had MRI evaluation ≥3 years postoperatively (mean follow-up 78 months). Of the 195 adjacent segments evaluated, 14 (7%) were included in subsequent fusion procedures. The 10-year surgery-free survival estimate was 82.7% (73.4-93.2%). After adjusting for covariates, ASD severity scores were predictive of reoperation only for patients with the highest score (hazard ratio [HR] 4.5 [1.0-19.8]) and those with foraminal stenosis (HR 4.2 [.4-12.7]). However, the prevalence of reoperation for ASD in these groups was only 16% and 15%, respectively. Conclusion The prevalence of reoperation for ASD was low for patients who presented with new symptoms ≥3 years after the index ACDF. Our findings do not support including asymptomatic levels in an anterior fusion construct, even if severe MRI abnormalities are present preoperatively.

Endoscopic Posterior Approach for Cervicothoracic and Upper Thoracic Foraminotomies: 2-Dimensional Operative Video.

Lower cervical and cervicothoracic radiculopathies can be challenging to treat through an anterior approach in patients with short-statured necks. With unilateral pathology, a posterior foraminotomy affords preservation of motion and avoids risks to anterior structures; yet, traditional open or even tubular retractor-based open systems are associated with postoperative muscle pain. Endoscopic approaches reduce muscle retraction and resection and are associated with shorter recovery time. This video demonstrates the endoscopic technique for performing cervicothoracic and thoracic foraminotomies. We present the case of a patient with severe left-hand weakness, particularly in grasp and hand intrinsic muscles. The differential diagnosis included a combined median and ulnar neuropathy, lower trunk plexopathy, medial cord plexopathy, thoracic outlet syndrome, and combined C8 and T1 radiculopathies. Imaging did not show brachial plexus pathology; instead, severe foraminal narrowing at the C8 and T1 roots was noted. We performed a fully endoscopic approach to decompress 2 levels of foraminal stenosis on the left side. Because the levels were adjacent, we operated through a single incision. Recovery of motor-evoked potentials to the abductor pollicis brevis was identified intraoperatively. The patient consented to the procedure and publication.

Asleep Deep Brain Stimulator Placement in the Intraoperative Magnetic Resonance Imaging System Hybrid Operating Suite: 2-Dimensional Operative Video.

Asleep, image-guided deep brain stimulation (DBS) placement is rapidly gaining popularity because it offers greater patient comfort and comparable accuracy with frame-based methods using microelectrode recording.1 In this video, we demonstrate our protocol to use the frameless, stereotactic ClearPoint system (MRI Interventions Inc, Irvine, California) to place DBS electrodes within an intraoperative magnetic resonance imaging hybrid operating suite (IMRIS; Deerfield Imaging Inc, Minnetonka, Minnesota).1-4 This system uses a skull-mounted aiming device coupled with sequential, intraoperative magnetic resonance imaging guidance to direct DBS lead placement to subcortical targets.2,5 Importantly, this method allows the patient to remain asleep during the operation and does not require medication holidays or additional microelectrode recording equipment. The literature indicates it has comparable accuracy1,6 and outcomes2 with the awake method. We demonstrate this technique with the case of a patient with Parkinson disease who required lead placement in the bilateral subthalamic nuclei.7-9 The patient consented to the procedure and publication. Patient positioning, draping nuances, initial indirect targeting, and final direct targeting are demonstrated. Risks of the operation include a risk of hemorrhage, hardware failure, and infection.10 DBS is currently an underutilized treatment option for patients with Parkinson disease.11 Offering the asleep option may be more tolerable for many patients who are wary of awake surgery.

A systematic exploration of parameters affecting evoked intracranial potentials in patients with epilepsy.

BACKGROUND: Brain activity is constrained by and evolves over a network of structural and functional connections. Corticocortical evoked potentials (CCEPs) have been used to measure this connectivity and to discern brain areas involved in both brain function and disease. However, how varying stimulation parameters influences the measured CCEP across brain areas has not been well characterized. OBJECTIVE: To better understand the factors that influence the amplitude of the CCEPs as well as evoked gamma-band power (70-150 Hz) resulting from single-pulse stimulation via cortical surface and depth electrodes. METHODS: CCEPs from 4370 stimulation-response channel pairs were recorded across a range of stimulation parameters and brain regions in 11 patients undergoing long-term monitoring for epilepsy. A generalized mixed-effects model was used to model cortical response amplitudes from 5 to 100 ms post-stimulation. RESULTS: Stimulation levels <5.5 mA generated variable CCEPs with low amplitude and reduced spatial spread. Stimulation at ≥5.5 mA yielded a reliable and maximal CCEP across stimulation-response pairs over all regions. These findings were similar when examining the evoked gamma-band power. The amplitude of both measures was inversely correlated with distance. CCEPs and evoked gamma power were largest when measured in the hippocampus compared with other areas. Larger CCEP size and evoked gamma power were measured within the seizure onset zone compared with outside this zone. CONCLUSION: These results will help guide future stimulation protocols directed at quantifying network connectivity across cognitive and disease states.

Fornicotomy for the Treatment of Epilepsy: An Examination of Historical Literature in the Setting of Modern Operative Techniques.

Fornicotomy has been used to treat intractable temporal lobe epilepsy with mixed success historically; however, modern advances in stereotactic, neurosurgical, and imaging techniques offer new opportunities to target the fornix with greater precision and safety. In this review, we discuss the historical uses and quantify the outcomes of fornicotomy for the treatment of temporal lobe epilepsy, highlight the potential mechanisms of benefit, and address what is known about the side effects of the procedure. We find that fornicotomy, with or without anterior commissurotomy, resulted in 61% (83/136) of patients having some seizure control benefit. We discuss the potential operative approaches for targeting the fornix, including laser ablation and the use of focused ultrasound ablation. More work is needed to address the true efficacy of fornicotomy in the modern surgical setting. This review is intended to serve as a framework for developing this approach.

Characterization of Focal Brain Tissue Water Measurements in Human Traumatic Brain Injury.

BACKGROUND: Cerebral edema is a major cause of morbidity in patients with severe traumatic brain injury (TBI). Intraparenchymal thermal conductivity-based probes that measure local cerebral blood flow can measure percent brain tissue water (%BTW) content, but such measures have been insufficiently characterized in patients with TBI. METHODS: We retrospectively reviewed physiologic data from patients with severe TBI treated at our institution (2014-2016) who underwent cerebral blood flow monitoring. RESULTS: Sixteen patients underwent focal %BTW measurements at a 15-minute sampling rate. %BTW measurements showed characteristic temporal profiles, with a mean time to peak of 3.7 ± 1.7 days. The mean minimum and maximum %BTWs were 71.0 ± 3.9% and 82.7 ± 7.4%, respectively (overall mean %BTW, 77.0 ± 2.9%). Intracranial pressure (ICP) values of 22 mm Hg (the current treatment threshold for patients with trauma) corresponded to 75.8 ± 5.4 %BTW. Repeated measures correlation showed that %BTW is negatively correlated with serum sodium concentration (r = -0.3; P < 0.001) and weakly positively correlated with ICP (r = 0.08; P = 0.01) and regional cerebral blood flow (r = 0.06; P < 0.001). These effects were consistent in a multivariable model including time from injury. In the best model, time was modeled as a quadratic term because the %BTW followed a parabolic trajectory. CONCLUSIONS: %BTW may be a clinically useful, real-time measurement of cerebral edema in patients with TBI. It is closely associated with the serum sodium concentration and follows a characteristic temporal course with characteristic trajectory and stability over time.

Improved Surgical Safety via Intraoperative Navigation for Transnasal Transsphenoidal Resection of Pituitary Adenomas.

Objectives Intraoperative navigation during neurosurgery can aid in the detection of critical structures and target lesions. The safety and efficacy of intraoperative, stereotactic computed tomography (CT) in the transnasal transsphenoidal resection of pituitary adenomas were explored. Design Retrospective chart review Setting Tertiary care hospital Participants Patients who underwent transsphenoidal resection of pituitary adenomas from February 2002 to May 2017. Intraoperative stereotactic CT navigation was used for all patients after mid-October 2013. Main Outcome Measures Operative time, estimated blood loss, gross total resection rate. Results Of 634 patients included, 175 underwent surgery with intraoperative navigation and 444 had no intraoperative navigation during surgery. There was no difference in mean age, sex, tumor type, or tumor size between the two groups. Operative time, endoscope use, cerebrospinal fluid diversion, and estimated blood loss were also similar. Two patients showed intraoperative, iatrogenic misdirection in the absence of stereotactic CT navigation ( p = 0.99) but similar numbers of patients having navigated and non-navigated surgery returned to the operating room, underwent gross total resection, and showed endocrinological normalization. Conclusions These results suggest that intraoperative navigation can reduce injury without resulting in increased operative time, estimated blood loss, or reduction in gross total resection.

Mapping language dominance through the lens of the Wada test.

The sodium amytal test, or Wada test, named after Juhn Wada, has remained a pillar of presurgical planning and is used to identify the laterality of the dominant language and memory areas in the brain. What is perhaps less well known is that the original intent of the test was to abort seizure activity from an affected hemisphere and also to protect that hemisphere from the effects of electroconvulsive treatment. Some 80 years after Paul Broca described the frontal operculum as an essential area of expressive language and well before the age of MRI, Wada used the test to determine language dominance. The test was later adopted to study hemispheric memory dominance but was met with less consistent success because of the vascular anatomy of the mesial temporal structures. With the advent of functional MRI, the use of the Wada test has narrowed to application in select patients. The concept of selectively inhibiting part of the brain to determine its function, however, remains crucial to understanding brain function. In this review, the authors discuss the rise and fall of the Wada test, an important historical example of the innovation of clinicians in neuroscience.

Evaluation of Complications and Costs During Overlapping Transsphenoidal Surgery in the Treatment of Pituitary Adenoma.

BACKGROUND: Pituitary adenomas are among the most common primary brain tumors. Recently, overlapping surgery has been curbed in many institutions because of the suggestion there might be more significant adverse events, despite several studies showing that complication rates are equivalent. OBJECTIVE: To assess complications and costs associated with overlapping surgery during the transsphenoidal resection of pituitary adenomas. METHODS: A single-center, retrospective cohort study was performed to evaluate the cases of patients who underwent a transsphenoidal approach for pituitary tumor resection. Patient, surgical, complication, and cost (value-driven outcome) variables were analyzed. RESULTS: A total of 629 patients (302 nonoverlapping, 327 overlapping cases) were identified. No significant differences in age (P = .6), sex (P = .5), tumor type (P = .5), or prior rates of pituitary adenoma resection (P = .5) were seen. Similar presenting symptoms were observed in the 2 groups, and follow-up length was comparable (P = .3). No differences in tumor sizes (P = .5), operative time (P = .4), fat/fascia use (P = .4), or cerebrospinal fluid diversion (P = .8) were seen between groups. The gross total resection rate was not significantly different (P = .9), and no difference in recurrence rate was seen (P = .4). A comparable complication rate was seen between groups (P = .6). No differences in total or subtotal costs were seen either. CONCLUSION: The results of this study offer additional evidence that overlapping surgery does not result in worsened complications, lengthened surgery, or increased patient cost for patients undergoing transsphenoidal resection of pituitary adenomas. Thus, studies and policy aiming to improve patient safety and cost should focus on optimizing other aspects of healthcare delivery.

Nationwide Shift From Percutaneous Rhizotomy to Microvascular Decompression for Treatment of Trigeminal and Other Cranial Nerve Neuralgias.

OBJECTIVE: The aim of this study was to report the trends in the use of common surgical interventions over the past decade to treat cranial nerve neuralgias. METHODS: The Centers for Medicare and Medicaid Services Part B National Summary Data File from 2000 to 2016 were studied. RESULTS: A total of 57.1 million persons were enrolled in 2016, up from 39.6 million persons in 2000. Suboccipital craniectomy done for cranial nerve decompressions (including cranial nerves V, VII, and IX) increased by 33.9 cases per year so that in 2016 the number of cases was 167% of what it was 17 years earlier (ie, from 655 cases in 2000 to 1096 cases in 2016). The less commonly used subtemporal approach craniectomy to treat trigeminal neuralgia (TN) increased by 1.13 cases per year (ie, from 25 cases in 2000 to 46 cases in 2016). The less invasive percutaneous rhizotomy procedures, including glycerol and radiofrequency ablation, for treatment of TN decreased by 42.9 cases per year (64%; ie, from 2578 cases in 2000 to 1206 cases in 2016). CONCLUSIONS: Overall trends show increased use of open surgery and decreased use of percutaneous rhizotomy, including destruction of the trigeminal nerve using balloon compression, glycerol injection, or thermal injury. These trends may be related to differences in outcomes between treatment modalities.

Deep brain stimulation for the treatment of disorders of consciousness and cognition in traumatic brain injury patients: a review.

Traumatic brain injury (TBI) is a looming epidemic, growing most rapidly in the elderly population. Some of the most devastating sequelae of TBI are related to depressed levels of consciousness (e.g., coma, minimally conscious state) or deficits in executive function. To date, pharmacological and rehabilitative therapies to treat these sequelae are limited. Deep brain stimulation (DBS) has been used to treat a number of pathologies, including Parkinson disease, essential tremor, and epilepsy. Animal and clinical research shows that targets addressing depressed levels of consciousness include components of the ascending reticular activating system and areas of the thalamus. Targets for improving executive function are more varied and include areas that modulate attention and memory, such as the frontal and prefrontal cortex, fornix, nucleus accumbens, internal capsule, thalamus, and some brainstem nuclei. The authors review the literature addressing the use of DBS to treat higher-order cognitive dysfunction and disorders of consciousness in TBI patients, while also offering suggestions on directions for future research.