MRI and pathology comparisons in Rasmussen's encephalitis: a multi-institutional examination of hemispherotomy outcomes relative to imaging and histological severity.

PURPOSE: Rasmussen encephalitis (RE) is a very rare chronic neurological disorder of unilateral inflammation of the cerebral cortex. Hemispherotomy provides the best chance at achieving seizure freedom in RE patients, but with significant risks and variable long-term outcomes. The goal of this study is to utilize our multicenter pediatric cohort to characterize if differences in pathology and/or imaging characterization of RE may provide a window into post-operative seizure outcomes, which in turn could guide decision-making for parents and healthcare providers. METHODS: This multi-institutional retrospective review of medical record, imaging, and pathology samples was approved by each individual institution's review board. Data was collected from all known pediatric cases of peri-insular functional hemispherotomy from the earliest available electronic medical records. Mean follow-up time was 4.9 years. Clinical outcomes were measured by last follow-up visit using both Engel and ILAE scoring systems. Relationships between categorical and continuous variables were analyzed with Pearson correlation values. RESULTS: Twenty-seven patients met study criteria. No statistically significant correlations existed between patient imaging and pathology data. Pathology stage, MRI brain imaging stages, and a combined assessment of pathology and imaging stages showed no statistically significant correlation to post-operative seizure freedom rates. Hemispherectomy Outcome Prediction Scale scoring demonstrated seizure freedom in only 71% of patients receiving a score of 1 and 36% of patients receiving a score of 2 which were substantially lower than predicted. CONCLUSIONS: Our analysis did not find evidence for either independent or combined analysis of imaging and pathology staging being predictive for post peri-insular hemispherotomy seizure outcomes, prompting the need for other biomarkers to be explored. Our data stands in contrast to the recently proposed Hemispherectomy Outcome Prediction Scale and does not externally validate this metric for an RE cohort.

Toward Deep Brain Monitoring with Superficial EEG Sensors Plus Neuromodulatory Focused Ultrasound.

Noninvasive recordings of electrophysiological activity have limited anatomic specificity and depth. We hypothesized that spatially tagging a small volume of brain with a unique electroencephalography (EEG) signal induced by pulsed focused ultrasound could overcome those limitations. As a first step toward testing this hypothesis, we applied transcranial ultrasound (2 MHz, 200-ms pulses applied at 1050 Hz for 1 s at a spatial peak temporal average intensity of 1.4 W/cm(2)) to the brains of anesthetized rats while simultaneously recording EEG signals. We observed a significant 1050-Hz electrophysiological signal only when ultrasound was applied to a living brain. Moreover, amplitude demodulation of the EEG signal at 1050 Hz yielded measurement of gamma band (>30 Hz) brain activity consistent with direct measurements of that activity. These results represent preliminary support for use of pulsed focused ultrasound as a spatial tagging mechanism for non-invasive EEG-based mapping of deep brain activity with high spatial resolution.

Multi-scale analysis of neural activity in humans: Implications for micro-scale electrocorticography.

OBJECTIVE: Electrocorticography grids have been used to study and diagnose neural pathophysiology for over 50 years, and recently have been used for various neural prosthetic applications. Here we provide evidence that micro-scale electrodes are better suited for studying cortical pathology and function, and for implementing neural prostheses. METHODS: This work compares dynamics in space, time, and frequency of cortical field potentials recorded by three types of electrodes: electrocorticographic (ECoG) electrodes, non-penetrating micro-ECoG (µECoG) electrodes that use microelectrodes and have tighter interelectrode spacing; and penetrating microelectrodes (MEA) that penetrate the cortex to record single- or multiunit activity (SUA or MUA) and local field potentials (LFP). RESULTS: While the finest spatial scales are found in LFPs recorded intracortically, we found that LFP recorded from µECoG electrodes demonstrate scales of linear similarity (i.e., correlation, coherence, and phase) closer to the intracortical electrodes than the clinical ECoG electrodes. CONCLUSIONS: We conclude that LFPs can be recorded intracortically and epicortically at finer scales than clinical ECoG electrodes are capable of capturing. SIGNIFICANCE: Recorded with appropriately scaled electrodes and grids, field potentials expose a more detailed representation of cortical network activity, enabling advanced analyses of cortical pathology and demanding applications such as brain-computer interfaces.

Rapid sequence magnetic resonance imaging in the assessment of children with hydrocephalus.

OBJECTIVE: Recent reports have shown the utility of rapid-acquisition magnetic resonance imaging (MRI) in the evaluation of children with hydrocephalus. Rapid sequence MRI (RS-MRI) acquires clinically useful images in seconds without exposing children to the risks of ionizing radiation or sedation. We review our experience with RS-MRI in children with shunts. METHODS: Overall image quality, cost, catheter visualization, motion artifact, and ventricular size were reviewed for all RS-MRI studies obtained at Seattle Children's Hospital during a 2-year period. Image acquisition time was 12-19 seconds, with sessions usually lasting less than 3 minutes. RESULTS: Image quality was very good or excellent in 94% of studies, whereas only one was graded as poor. Significant motion artifact was noted in 7%, whereas 77% had little or no motion artifact. Catheter visualization was good or excellent in 57%, poor in 36%, and misleading in 7%. Small ventricular size was correlated with poor catheter visualization (Spearman's ρ = 0.586; P < 0.00001). RS-MRI imaging cost ∼$650 more than conventional computed tomography (CT). CONCLUSIONS: Our study supports that RS-MRI is an adequate substitute that allows reduced use of CT imaging and resultant exposure to ionizing radiation. Catheter position visualization remains suboptimal when ventricles are small, but shunt malfunction can be adequately determined in most cases. The cost is significantly more than CT, but the potential for lifetime reduction in radiation exposure may justify this expense in children. Limitations include the risk of valve malfunction after repeated exposure to high magnetic fields and the need for reprogramming with many types of adjustable valves.

A survey of complementary and alternative medicine (CAM) awareness among neurosurgeons in Washington State.

OBJECTIVES: Use of complementary and alternative medicine (CAM) by the U.S. population increased significantly in the past 2 decades. To maximize a patient's recovery from a neurosurgical procedure, it is critical that neurosurgeons be aware of the benefits and potential adverse complications of CAM therapies. The survey's purpose was to assess the current patterns of CAM utilization by neurosurgery patients and neurosurgeon knowledge of CAM therapies among Washington State Association of Neurological Surgeons (WSANS) members. METHODS: Members of the WSANS were surveyed in 2005. The survey was sent via e-mail and the data were anonymously collected using an online survey tool, Catalyst WebQ. RESULTS: The majority of responses (79%) stated that their neurosurgery practice was > or =75% adults. Acupuncture, herbs, massage therapy, prayer, and yoga were the most common CAM treatments patients used or discussed with their neurosurgeon. Fifty percent (50%) of neurosurgeons discussed the use of acupuncture among their colleagues. Concerning prayer and spirituality, 38% of the surveyed neurosurgeons stated that > or =25% of their patients have disclosed that they pray for their health; 42% stated that spirituality and prayer may affect neurosurgery outcome; and 38% stated that they pray for their patients. Overall, 63% of surveyed neurosurgeons stated that CAM treatments have a role in neurosurgery. CONCLUSIONS: The use of CAM may influence neurosurgical care; and the role of spirituality and prayer should be further explored. Because CAM utilization is ubiquitous, open discussion and familiarity with CAM treatments are becoming increasingly important in the field of neurosurgery.

Cerebral hemispherectomy in infants and young children.

BACKGROUND: Children with seizure disorders unresponsive to medical management may undergo surgical disconnection of a cerebral hemisphere, or hemispherectomy, in order to reduce or eliminate seizures. Because early cessation of seizures is thought to improve developmental outcomes, infants and young children with intractable seizures are undergoing hemispherectomies with increasing frequency. Previously, these procedures have been noted to be accompanied by severe cardiovascular, pulmonary, neurologic and coagulopathic complications. Newer surgical techniques (i.e. 'functional' rather than 'anatomic' hemispherectomy) and improved anesthetic management may reduce the perioperative complication rate of this procedure. The aim of this case series was to determine the incidence of major complication of functional hemispherectomy in our institution. METHODS: A retrospective chart review was conducted of all children <3 years of age undergoing functional hemispherectomies for intractable seizures over a 4-year period at our institution. RESULTS: Seven children were identified. No serious cardiovascular, pulmonary, neurologic or coagulopathic adverse events occurred. Perioperative blood loss and its sequelae were the most common complication. Postoperative management was generally uncomplicated, although one patient required readmission to the ICU for treatment of diabetes insipidus. All children survived and, at latest follow-up, all but one remained seizure-free. CONCLUSION: This small case series suggests that improvements in anesthetic and surgical techniques may be associated with a decreased complication rate for infants and small children undergoing seizure surgery than previously reported.

Cortical language localization in left, dominant hemisphere. An electrical stimulation mapping investigation in 117 patients. 1989.

The localization of cortical sites essential for language was assessed by stimulation mapping in the left, dominant hemispheres of 117 patients. Sites were related to language when stimulation at a current below the threshold for afterdischarge evoked repeated statistically significant errors in object naming. The language center was highly localized in many patients to form several mosaics of 1 to 2 sq cm, usually one in the frontal and one or more in the temporoparietal lobe. The area of individual mosaics, and the total area related to language was usually much smaller than the traditional Broca-Wernicke areas. There was substantial individual variability in the exact location of language function, some of which correlated with the patient's sex and verbal intelligence. These features were present for patients as young as 4 years and as old as 80 years, and for those with lesions acquired in early life or adulthood. These findings indicate a need for revision of the classical model of language localization. The combination of discrete localization in individual patients but substantial individual variability between patients also has major clinical implications for cortical resections of the dominant hemisphere, for it means that language cannot be reliably localized on anatomic criteria alone. A maximal resection with minimal risk of postoperative aphasia requires individual localization of language with a technique like stimulation mapping.

Spontaneous subdural fluid collections following transection of a fatty filum terminale: case report and review of the literature.

We present the case of a 6-year-old girl who developed bilateral subdural fluid collections following transection of her fatty filum terminale. The patient presented to our emergency department 3 weeks subsequent to surgery, reporting symptoms of headache, nausea, and vomiting. The presence of bilateral subdural fluid collections was confirmed by head computerized tomography. Subdural fluid collections and hematomas have been associated with intracranial hypotension and excessive cerebrospinal fluid leakage; however, there are relatively few cases of subdural fluid collections/hematomas following spine surgery reported in the literature. To our knowledge, this is a unique description of development and resolution of subdural fluid collections following surgical transection of a fatty filum terminale.

Electrocorticographic frequency alteration mapping: a clinical technique for mapping the motor cortex.

OBJECTIVE: Electrocortical stimulation (ECS) has been well established for delineating the eloquent cortex. However, ECS is still coarse and inefficient in delineating regions of the functional cortex and can be hampered by after-discharges. Given these constraints, an adjunct approach to defining the motor cortex is the use of electrocorticographic signal changes associated with active regions of the cortex. The broad range of frequency oscillations are categorized into two main groups with respect to the sensorimotor cortex: low and high frequency bands. The low frequency bands tend to show a power reduction with cortical activation, whereas the high frequency bands show power increases. These power changes associated with the activated cortex could potentially provide a powerful tool in delineating areas of the motor cortex. We explore electrocorticographic signal alterations as they occur with activated regions of the motor cortex, as well as its potential in clinical brain mapping applications. METHODS: We evaluated seven patients who underwent invasive monitoring for seizure localization. Each patient had extraoperative ECS mapping to identify the motor cortex. All patients also performed overt hand and tongue motor tasks to identify associated frequency power changes in regard to location and degree of concordance with ECS results that localized either hand or tongue motor function. RESULTS: The low frequency bands had a high sensitivity (88.9-100%) and a lower specificity (79.0-82.6%) for identifying electrodes with either hand or tongue ECS motor responses. The high frequency bands had a lower sensitivity (72.7-88.9%) and a higher specificity (92.4-94.9%) in correlation with the same respective ECS positive electrodes. CONCLUSION: The concordance between stimulation and spectral power changes demonstrate the possible utility of electrocorticographic frequency alteration mapping as an adjunct method to improve the efficiency and resolution of identifying the motor cortex.