Comparison of minimally invasive to standard temporal lobectomy approaches to epilepsy surgery: Seizure relief and visual confrontation naming outcomes.

The purpose of this study was to systematically examine three different surgical approaches in treating left medial temporal lobe epilepsy (mTLE) (viz., subtemporal selective amygdalohippocampectomy [subSAH], stereotactic laser amygdalohippocampotomy [SLAH], and anterior temporal lobectomy [ATL]), to determine which procedures are most favorable in terms of visual confrontation naming and seizure relief outcome. This was a retrospective study of 33 adults with intractable mTLE who underwent left temporal lobe surgery at three different epilepsy surgery centers who also underwent pre-, and at least 6-month post-surgical neuropsychological testing. Measures included the Boston Naming Test (BNT) and the Engel Epilepsy Surgery Outcome Scale. Fisher's exact tests revealed a statistically significant decline in naming in ATLs compared to SLAHs, but no other significant group differences. 82% of ATL and 36% of subSAH patients showed a significant naming decline whereas no SLAH patient (0%) had a significant naming decline. Significant postoperative naming improvement was seen in 36% of SLAH patients in contrast to 9% improvement in subSAH patients and 0% improvement in ATLs. Finally, there were no statistically significant differences between surgical approaches with regard to seizure freedom outcome, although there was a trend towards better seizure relief outcome among the ATL patients. Results support a possible benefit of SLAH in preserving visual confrontation naming after left TLE surgery. While result interpretation is limited by the small sample size, findings suggest outcome is likely to differ by surgical approach, and that further research on cognitive and seizure freedom outcomes is needed to inform patients and providers of potential risks and benefits with each.

A stereotactic near-infrared probe for localization during functional neurosurgical procedures: further experience.

OBJECT: The authors previously developed an optical stereotactic probe employing near-infrared (NIR) spectroscopy to provide intraoperative localization by distinguishing gray matter from white matter. In the current study they extend and further validate this technology. METHODS: Near-infrared probes were inserted 203 times during 138 procedures for movement disorders. Detailed validation with postoperative imaging was obtained for 121 of these procedures and with microelectrode recording (MER) for 30 procedures. Probes were constructed to interrogate tissue perpendicular to the probe path and to incorporate hollow channels for microelectrodes, deep brain stimulation (DBS) electrodes, and other payloads. RESULTS: The NIR data were highly correlated to imaging and MER recordings for thalamic targets. The NIR data were highly sensitive but less specific relative to imaging for subthalamic targets, confirming the ability to detect the subthalamic nucleus and to provide warnings of inaccurate localization. The difference between the NIR- and MER-detected midpoints of the subthalamic nucleus along the chosen tracks was 1.1 +/- 1.2 mm (SD). Data obtained during insertion and withdrawal of the NIR probe suggested that DBS electrodes may push their targets ahead of their paths. There was one symptomatic morbidity. Detailed NIR data could be obtained from a 7-cm track in less than 10 minutes. CONCLUSIONS: The NIR probe is a straightforward, quick, and robust tool for intraoperative localization during functional neurosurgery. Potential future applications include localization of targets for epilepsy and psychiatric disorders, and incorporation of NIR guidance into probes designed to convey various payloads.

Virtual framing: the feasibility of frameless radiosurgical planning for the Gamma Knife.

OBJECT: Gamma Knife (GK) treatments are typically delivered in 1 day with little opportunity to test different planning strategies. The authors demonstrate 2 methods for imposing GK coordinate systems upon imaging datasets without frame attachment to allow leisurely preprocedural planning, and discuss potential applications. METHODS: A "virtual framing" is constructed by coregistering a CT scan of a Leksell frame with a patient dataset using the GammaPlan (Multiview) module. Equations for skull radii are derived by approximating the skull as an ellipsoid. No proprietary software other than that of the GK system is required. In a second method, images of fiducial markers are directly superimposed on the patient dataset. Validation of the first method was achieved by comparing the lengths of 75 line segments and 60 single shot diameters measured in the virtual coordinates with those measured in real coordinates. In addition to preplanning, 2 applications are discussed. The first is the use of GK software to aid radiosurgical planning for other devices. The second is the use of virtual framing to enhance automatic optimization algorithms. RESULTS: Mean (+/- standard deviation) and root-mean-square differences in lengths were 0.18 +/- 0.32 and 0.37 mm. Mean and root-mean-square differences in diameters of single-shot plans were 0.01 +/- 0.18 and 0.18 mm. CONCLUSIONS: Virtual framing allows exploration of radiosurgical planning strategies prior to the day of treatment using only the GK software. Other applications include enhancement of radiosurgical planning for other systems and enhancement of optimization algorithms.

Impact of site of tumor recurrence upon survival for children with recurrent or progressive medulloblastoma.

OBJECT: The object of this study was to identify prognostic factors for survival among children with recurrent medulloblastoma. METHODS: Postprogression survival and patient, tumor, and treatment factors were examined in 46 cases of recurrent medulloblastoma (mean age of patients at diagnosis 6.5 years, mean age at progression 8.4 years). Differences were calculated by Kaplan-Meier log-rank analysis. Multivariate analysis was performed using the Cox proportional hazard model. RESULTS: The probability of 5-year survival was 26.3%. Forty-one patients received salvage therapy and five patients received hospice care only. Log-rank analysis showed an association between prolonged patient survival and recurrence limited to the primary site (p = 0.008), initial therapy including the Pediatric Oncology Group (POG) regimen for the treatment of brain tumors in infants ("Baby POG;" p = 0.037), and treatment with radiation therapy (RT) following initial progression (p = 0.015). Cox regression analysis showed a significant association between prolonged survival and only one variable--tumor recurrence restricted to the primary site (p = 0.037). There was no significant association between prolonged survival and any other variables, including patient sex, age at progression, interval from tumor diagnosis to progression, initial tumor stage, and salvage treatment with chemotherapy. Subgroup analysis revealed that site of tumor progression was also prognostic for survival among the subgroup of patients older than 3 years of age at diagnosis who were initially treated with RT and chemotherapy (p = 0.017, log-rank test). CONCLUSIONS: Some children with recurrent medulloblastoma will be long-term survivors, and certain features are associated with likelihood of survival. Patients whose tumors recur at only the primary tumor site have an increased chance of prolonged survival.

A volumetric study of CyberKnife hypofractionated stereotactic radiotherapy as salvage for progressive malignant brain tumors: initial experience.

OBJECTIVE: Radiosurgery is frequently offered to patients with progressive malignant brain tumors if radiation therapy or chemotherapy fails to provide local control. The use of single-shot regimens, however, is limited by the risk of complications when the tumor is large, surrounded by edema or has been pre-treated with radiation. Hypofractionation may confer safety but has not been tested for these difficult tumors. We report the results of hypofractionation as an alternative option in a small cohort of progressive malignant brain tumors. METHODS: Hypofractionated CyberKnife radiotherapy was chosen for 18 progressive malignant brain tumors (six high-grade gliomas and 12 metastatic lesions) in 15 patients because of size, previous treatment with radiation or surrounding edema. The mean dose was 21 +/- 4 Gy and the number of fractions was 5 +/- 0.6. The volume of each tumor at treatment was compared with the volume at follow-up. RESULTS: Thirteen of the 18 tumors (72%) showed a volume decrease. The average volume change was a decrease of 16 +/- 58% (median: 20%) with a follow-up of 180 +/- 121 days (median: 172 days). Toxicity occurred in only one patient, with symptoms improving on steroids. DISCUSSION: Progression of malignant brain tumors not ideal for single-shot radiosurgery can be arrested or reversed, at least for short periods, with minimal toxicity using hypofractionated radiotherapy. Longer studies will be needed to assess durability of this response in these difficult tumors.

The first formulation of image-based stereotactic principles: the forgotten work of Gaston Contremoulins.

Although image-based human stereotaxis began with Spiegel and Wycis in 1947, the major principles of radiographic stereotaxis were formulated 50 years earlier by the French scientific photographer Gaston Contremoulins. In 1897, frustrated by the high morbidity of bullet extraction from the brain, the Parisian surgeon Charles Rémy asked Contremoulins to devise a method for bullet localization using the then new technology of x-rays. In doing so, Contremoulins conceived of many of the modern principles of stereotaxis, including the use of a reference frame, radiopaque fiducials for registration, images to locate the target in relation to the frame, phantom devices to locate the target in relation to the fiducial marks, and the use of an adjustable pointer to guide the surgical approach. Contremoulins' ideas did not emerge from science or medicine, but instead were inspired by his training in the fine arts. Had he been a physician instead of an artist, he might have never discovered his extraordinary methods. Contremoulins' "compass" and its variants enjoyed great success during World War I, but were abandoned by 1920 for simpler methods. Although Contremoulins was one of the most eminent radiographers in France, he was not a physician, and his personality was uncompromising. By 1940, both he and his methods were forgotten. It was not until 1988 that he was rediscovered by Moreau while reviewing the history of French radiology, and chronicled by Mornet in his extensive biography. The authors examine Contremoulins' stereotactic methods in historical context, describe the details of his devices, relate his discoveries to his training in the fine arts, and discuss how his prescient formulation of stereotaxis was forgotten for more than half a century.

Use of sagittal images for localization of the subthalamic nucleus. Technical note.

Direct observation of the subthalamic nucleus (STN) is not always possible, and physicians at many centers rely on indirect methods that relate the position of the STN to more easily recognized structures such as the red nucleus (RN). In this paper the authors describe an indirect method of viewing the STN based on the anatomy depicted on sagittal magnetic resonance (MR) images. A review of sagittal slices appearing in standard stereotactic atlases showed that the STN lies within the angle formed by the descending internal capsule (IC) and the substantia nigra (SN). The authors' technique consists of marking the location of the STN in this nigrocapsular angle on each sagittal MR image between the RN and the lateral border of the brainstem, and transferring these points to axial MR images to build a locus of points used to describe the STN. A point is chosen in the center of this locus as the stereotactic target. Two hundred eighty-two sagittal images obtained from 71 MR imaging studies performed in 29 patients by using a fast-spin echo inversion-recovery technique were examined for the presence of the STN, the SN, and the IC. The descending IC could be detected in 97% of the slices, the SN in 95% of the slices, and the STN in 73% of the slices. This indirect method involving sagittal anatomy can be used to refine localization of the STN.

A Strange Case of Downward Displacement of a Deep Brain Stimulation Electrode 10 Years Following Implantation: The Gliding Movement of Snakes Theory.

BACKGROUND: Despite the best efforts to ensure stereotactic precision, deep brain stimulation (DBS) electrodes can wander from their intended position after implantation. We report a case of downward electrode migration 10 years following successful implantation in a patient with Parkinson disease. METHODS: A 53-year-old man with Parkinson disease underwent bilateral implantation of DBS electrodes connected to a subclavicular 2-channel pulse generator. The generator was replaced 7 years later, and a computed tomography (CT) scan confirmed the correct position of both leads. The patient developed a gradual worsening affecting his right side 3 years later, 10 years after the original implantation. A CT scan revealed displacement of the left electrode inferiorly into the pons. The new CT scans and the CT scans obtained immediately after the implantation were merged within a stereotactic planning workstation (Brainlab). RESULTS: Comparing the CT scans, the distal end of the electrode was in the same position, the proximal tip being significantly more inferior. The size and configuration of the coiled portions of the electrode had not changed. At implantation, the length was 27.7 cm; after 10 years, the length was 30.6 cm. CONCLUSIONS: These data suggests that the electrode had been stretched into its new position rather than pushed. Clinicians evaluating patients with a delayed worsening should be aware of this rare event.

Local electronic storage of radiological studies for radiosurgery.

OBJECTIVE: Although radiosurgical practice mandates meticulous radiological follow-up, even the most efficient radiology department can be overwhelmed by the large number of radiosurgical patients who have undergone diagnostic studies for many years at many different institutions to follow many separate lesions. Although the task of assembling these studies is theoretically possible, because they are spread out in time and space, it is often impractical. We therefore sought to construct a computer-based system that could store images from multiple sources and present them instantly for review. METHODS: We attached a flatbed film scanner to a standard desktop computer in our clinic and scanned selected sheets of film into an image database at each visit of a radiosurgical patient. "Low-tech" solutions were deliberately chosen-that is, to enhance ease and software compatibility, we used the operating system's directory structure for organization of data instead of proprietary software. Standard commercially available software was used to review studies that had been previously scanned. RESULTS: During a 2- to 3-year period, images were scanned from 1129 studies performed on 435 patients. Images could be reviewed instantly and compared with current studies, and scanning a single piece of film required approximately 30 seconds. We estimate that the current capacity of our computer memory will satisfy our needs for approximately 12 years. CONCLUSION: Assembly of an efficient and inexpensive system for image storage and retrieval suitable for radiosurgical practice is feasible and straightforward. Although our system is not a substitute for a radiology department, it obviates the constant frustration of "finding the films" and has become an essential part of our radiosurgical practice.

Validation of a near-infrared probe for detection of thin intracranial white matter structures.

OBJECT: The authors have developed an intracranial near-infrared (NIR) probe that analyzes the scattering of light emitted from its tip to measure the optical properties of cerebral tissue. Despite its success in distinguishing graymatter from white matter in humans during stereotactic surgery, the limits of this instrument's resolution remain unclear. In this study, the authors determined the spatial resolution of this new probe by using a rodent model supplemented with phantom measurements and computer simulation. METHODS: A phantom consisting of Intralipid and gelatin was constructed to resemble a layer of white matter overlying a layer of gray matter. Near-infrared measurements were obtained as the probe was inserted through the gray-white matter transition. A computer simulation of NIR measurements through a gray-white matter transition was also performed using Monte Carlo techniques. The NIR probe was then used to study 19 tracks from the cortical surface through the corpus callosum in an in vivo rodent preparation. The animals were killed and histological sections through the tracks were obtained. Data from the phantom models and computer simulations showed that the NIR probe samples a volume of tissue extending 1 to 1.5 mm in front of the probe tip (this distance is termed the "lookthrough" distance). Measurements obtained from an NIR probe passing through a thin layer of white matter consisted of an initial segment of increasing values, a maximum (peak) value, and a trailing segment of decreasing values. The length of the initial segment is the lookthrough distance, the position of the peak indicates the location of the superficial white matter boundary, and the length of the trailing segment is the thickness of the layer. These considerations were confirmed in experiments with rodents. All tracks passed through the corpus callosum, which was demonstrated as a broad peak on each NIR graph. The position of the dorsal boundary of the corpus callosum and its width (based on histological measurements) correlated well with the peak of the NIR curve and its trailing segment, respectively. The initial segments correlated well with estimates of the lookthrough distance. Five of the tracks transected the smaller anterior commissure (diameter 0.2 mm), producing a narrow NIR peak at the correct depth. CONCLUSIONS: Data in this study confirm that the NIR probe can reliably detect and measure the thickness of layers of white matter as thin as 0.2 mm. Such resolution should be adequate to detect larger structures of interest encountered during stereotactic surgery in humans.

Linearity and non-linearity in cerebral hemodynamics.

BACKGROUND: Transcranial Doppler ultrasound has been extensively used to study cerebral hemodynamics, and yet the basic characteristics of the input/output system of blood pressure/velocity are little known. We examine whether this system can best be considered linear or non-linear. METHODS: We assessed the adequacy of linear modeling in four ways: (1) Known properties of cerebral blood flow were reviewed and analyzed from a systems standpoint; (2) 1100 ARX & OE model types were tested with data from 29 normal subjects, with and without lowpass filtering; (3) time-frequency analysis was used to identify nonstationary behavior and markers of non-linearity (such as bifurcations, chirps, and intermittent autoregulatory impairment) in the same data sets; (4) simple computer models of autoregulation incorporating time delays and non-linear elements were tested for production of spontaneous oscillations. RESULTS: (1) Several aspects of cerebral hemodynamics are poorly described by linear models, (2) the ARX & OE models performed poorly, (3) time-frequency analysis showed non-linear and nonstationary behavior, (4) the computer models produced spontaneous oscillations similar to those observed in humans. CONCLUSIONS: There is strong evidence that the blood pressure/velocity system is non-linear.

Recurrent adult choroid plexus carcinoma treated with high-dose chemotherapy and syngeneic stem cell (bone marrow) transplant.

Choroid plexus carcinomas (CPCs) are rare epithelial central nervous system tumors. CPC occurs mainly in infants and young children, comprising ≈ 1 to 4% of all pediatric brain neoplasms. There is very limited information available regarding tumor biology and CPC treatment due to its rarity. There have been various case reports and meta-analyses of reported cases with CPC. Surgical resection is often challenging but remains a well-established treatment option. Chemotherapy is often reserved for recurrent or refractory cases, but the goal of treatment is usually palliative. We present a case of recurrent, adult CPC with disseminated leptomeningeal involvement treated with salvage chemotherapy including high-dose ifosfamide, carboplatin, and etoposide; once a remission was achieved, this response was consolidated with a syngeneic stem cell (bone marrow) transplant after a preparative regimen of high-dose chemotherapy with carboplatin, etoposide, and thiotepa. Although the patient tolerated the transplant well and remained disease-free for 12 months, she subsequently succumbed to relapsed disease 18 months posttransplant. We believe that this is the first report of using syngeneic stem cell transplant in CPC to consolidate a remission achieved by salvage chemotherapy.

The utility and feasibility of business training for neurosurgeons.

OBJECTIVE: Socioeconomic changes have imposed many administrative demands on neurosurgeons, including managing facilities such as the intensive care unit without absolute authority and maintaining referrals, marketing in an increasingly competitive environment, effecting change within stubborn hospital systems, negotiating fair contracts with insurance companies, using financial statements to make financial decisions, managing small groups under new rules of human resources, navigating a Byzantine system of reimbursement, and assessing entrepreneurial opportunities. A set of new tools and skills has been developed by the business community in response to similar problems that may be of use to neurosurgeons. These advances are reviewed in a neurosurgical context, and routes to business training for the neurosurgeon are discussed. METHODS: Recent advances in business are discussed with a focus on their relevance to neurosurgical practice. Current neurosurgical interest in business training and training opportunities for neurosurgeons are presented. RESULTS: Interest in business training within the neurosurgery community is keen, and advances in the field of business may be helpful in addressing the new tasks faced by neurosurgeons. CONCLUSION: New tools from advances in business are available which have been invaluable to corporations and may be helpful to neurosurgeons wanting to improve efficiency and maintain competitive advantage. Business training is available to neurosurgeons through a variety of routes.

Multidisciplinary treatment of a large cerebral dural arteriovenous fistula using embolization, surgery, and radiosurgery.

Dural arteriovenous fistulae are rare lesions composed of abnormal connections between meningeal arteries and the dural sinuses or lepto-meningeal veins. Treatment is challenging because of the small size and wide distribution of the myriad sites of fistulous connection. We present a case of a dural arteriovenous fistula presenting with visual deterioration, pulsatile tinnitus, and intracranial hypertension that was successfully treated with a multidisciplinary approach combining angiographic, surgical, and radiosurgical intervention. This is one of the largest of these formidable lesions treated in this fashion that has been reported.

Determination of optical probe interrogation field of near-infrared reflectance: phantom and Monte Carlo study.

An optical probe used to localize human brain tissues in vivo has been reported previously. It was able to sense the underlying tissue structure with an optical interrogation field, termed as "look ahead distance" (LAD). A new side-firing probe has been designed with its optical window along its side. We have defined the optical interrogation field of the new side probe as "look aside distance" (LASD). The purpose of this study is to understand the dependence of the LAD and LASD on the optical properties of tissue, the light source intensity, and the integration time of the detector, using experimental and computational methods. The results show that a decrease in light intensity does decrease the LAD and LASD and that an increase in integration time of detection may not necessarily improve the depths of LAD and LASD. Furthermore, Monte Carlo simulation results suggest that the LAD/LASD decreases with an increase in reduced scattering coefficient to a point, after which the LAD/LASD remains constant. We expect that an optical interrogation field of a tip or side probe is approximately 1-2 mm in white matter and 2-3.5 mm in gray matter. These conclusions will help us optimally manipulate the parameter settings during surgery and determine the spatial resolution of the probe.

Human cerebral autoregulation before, during and after spaceflight.

Exposure to microgravity alters the distribution of body fluids and the degree of distension of cranial blood vessels, and these changes in turn may provoke structural remodelling and altered cerebral autoregulation. Impaired cerebral autoregulation has been documented following weightlessness simulated by head-down bed rest in humans, and is proposed as a mechanism responsible for postspaceflight orthostatic intolerance. In this study, we tested the hypothesis that spaceflight impairs cerebral autoregulation. We studied six astronauts approximately 72 and 23 days before, after 1 and 2 weeks in space (n = 4), on landing day, and 1 day after the 16 day Neurolab space shuttle mission. Beat-by-beat changes of photoplethysmographic mean arterial pressure and transcranial Doppler middle cerebral artery blood flow velocity were measured during 5 min of spontaneous breathing, 30 mmHg lower body suction to simulate standing in space, and 10 min of 60 deg passive upright tilt on Earth. Dynamic cerebral autoregulation was quantified by analysis of the transfer function between spontaneous changes of mean arterial pressure and cerebral artery blood flow velocity, in the very low- (0.02-0.07 Hz), low- (0.07-0.20 Hz) and high-frequency (0.20-0.35 Hz) ranges. Resting middle cerebral artery blood flow velocity did not change significantly from preflight values during or after spaceflight. Reductions of cerebral blood flow velocity during lower body suction were significant before spaceflight (P < 0.05, repeated measures ANOVA), but not during or after spaceflight. Absolute and percentage reductions of mean (+/- s.e.m.) cerebral blood flow velocity after 10 min upright tilt were smaller after than before spaceflight (absolute, -4 +/- 3 cm s(-1) after versus -14 +/- 3 cm s(-1) before, P = 0.001; and percentage, -8.0 +/- 4.8% after versus -24.8 +/- 4.4% before, P < 0.05), consistent with improved rather than impaired cerebral blood flow regulation. Low-frequency gain decreased significantly (P < 0.05) by 26, 23 and 27% after 1 and 2 weeks in space and on landing day, respectively, compared with preflight values, which is also consistent with improved autoregulation. We conclude that human cerebral autoregulation is preserved, and possibly even improved, by short-duration spaceflight.