Neurosurgery Blog

Neurosurgery 70:56–65, 2012 DOI: 10.1227/NEU.0b013e31822cb882

To reduce the risk of disabling postoperative functional deficit in patients with lesions in the dominant hemisphere, information about the localization of eloquent language areas is mandatory.

OBJECTIVE: To demonstrate the feasibility of arcuate fascicle (AF) tractography for proper localization of eloquent language areas in the superior temporal (STG) and inferior frontal gyrus (IFG).

METHODS: Between January and June 2010, we performed surgery in 13 patients with highly eloquent lesions with close spatial relationship to the primary language areas. All of them received preoperative diffusion tensor imaging for AF tractography. The STG and IFG were delineated at the ends of the AF. Five patients underwent functional magnetic resonance imaging of the primary language areas. The results were compared with tractography.

RESULTS: Tractography of the AF without prior knowledge of the localization of the STG and IFG was feasible in all cases. In the cases with functional magnetic resonance imaging, the activation maps matched the tractography results. In all but 1 patient, preservation of the primary language areas was possible, proven by the good neurological outcome. One patient suffered from a language dysfunction caused by a lesion in the medial and inferior temporal gyrus along the surgical pathway.

CONCLUSION: Tractography of the AF is a useful tool for identification of parts of the main primary language areas. Using tractography as a localization procedure to determine the primary language areas aids in the delineation of the STG and IFG and thus may help reduce the risk of postoperative permanent neurological deficit.

Neurosurgical Focus Jan 2012 / Vol. 32 / No. 1 / Page E1. DOI: 10.3171/2011.10.FOCUS11248

Recent technological developments open the field of therapeutic application of focused ultrasound to the brain through the intact cranium. The goal of this study was to apply the new transcranial magnetic resonance imaging–guided focused ultrasound (tcMRgFUS) technology to perform noninvasive central lateral thalamotomies (CLTs) as a treatment for chronic neuropathic pain.

METHODS

In 12 patients suffering from chronic therapy-resistant neuropathic pain, tcMRgFUS CLT was proposed. In 11 patients, precisely localized thermal ablations of 3–4 mm in diameter were produced in the posterior part of the central lateral thalamic nucleus at peak temperatures between 51°C and 64°C with the aid of real-time patient monitoring and MR imaging and MR thermometry guidance. The treated neuropathic pain syndromes had peripheral (5 patients) or central (6 patients) origins and covered all body parts (face, arm, leg, trunk, and hemibody).

RESULTS

Patients experienced mean pain relief of 49% at the 3-month follow-up (9 patients) and 57% at the 1-year follow-up (8 patients). Mean improvement according to the visual analog scale amounted to 42% at 3 months and 41% at 1 year. Six patients experienced immediate and persisting somatosensory improvements. Somatosensory and vestibular clinical manifestations were always observed during sonication time because of ultrasound-based neuronal activation and/or initial therapeutic effects. Quantitative electroencephalography (EEG) showed a significant reduction in EEG spectral overactivities. Thermal ablation sites showed sharply delineated ellipsoidal thermolesions surrounded by short-lived vasogenic edema. Lesion reconstructions (18 lesions in 9 patients) demonstrated targeting precision within a millimeter for all 3 coordinates. There was 1 complication, a bleed in the target with ischemia in the motor thalamus, which led to the introduction of 2 safety measures, that is, the detection of a potential cavitation by a cavitation detector and the maintenance of sonication temperatures below 60°C.

CONCLUSIONS

The authors assert that tcMRgFUS represents a noninvasive, precise, and radiation-free neurosurgical technique for the treatment of neuropathic pain. The procedure avoids mechanical brain tissue shift and eliminates the risk of infection. The possibility of applying sonication thermal spots free from trajectory restrictions should allow one to optimize target coverage. The real-time continuous MR imaging and MR thermometry monitoring of targeting accuracy and thermal effects are major factors in optimizing precision, safety, and efficacy in an outpatient context.

Neurosurgery 69:1299–1306, 2011 DOI: 10.1227/NEU.0b013e31822b7069

Introduction of the portable intraoperative CT scanner provides for a precise and cost-effective way of fusing head CT images with high-tesla MRI for the exquisite definition of soft tissue needed for stereotactic targeting.

OBJECTIVE: To evaluate the accuracy of stereotactic electrode placement in patients undergoing deep brain stimulation (DBS) by comparing frame-based postimplantation intraoperative CT (iCT) images fused to a recent 3T-MRI with frame-based postimplantation intraoperative MRI (iMRI) alone.

METHODS: Frame-based DBS surgeries of 46 targets performed from February 8, 2007 to April 28, 2008 in 26 patients with the use of immediate postimplantation iMRI for target localization were compared with frame-based immediate postimplantation iCT fused with a recent 3T brain MRI for DBS localization of 50 targets performed from August 13, 2008 to February 18, 2010 in 26 patients. Pre- and postoperative mid anterior commissure-posterior commissure line coordinates and XYZ coordinates for preoperatively calculated DBS targets (intended target) and for the permanent DBS lead tips were determined. The differences between preoperative DBS target and postoperative permanent DBS lead-tip coordinates based on postimplantation intraoperative MRI for the MRI-alone group and based on postimplantation intraoperative CT fused to recent preoperative MRI in the CTMRI group were measured. The t test and Yuen test were used for comparison.

RESULTS: No statistically significant differences were found between the 2 groups when comparing the pre- and postperative changes in mid anterior commissure-posterior commissure line coordinates and XYZ coordinates.

CONCLUSION: Postimplantation DBS lead localization and therefore targeting accuracy was not significantly different between frame-based stereotactic 1.5T-MRI and framebased stereotactic head CT fused with recent 3T-MRI.

Acta Neurochir (2011) 153:2307–2318. DOI 10.1007/s00701-011-1081-7

The aim of our study was to evaluate discrepancies between the electrophysiologically and MRI-defined subthalamic nucleus (STN) in order to contribute to the ongoing debate of whether or not microelectrode recording (MER) provides additional information to imageguided targeting in deep brain stimulation.

Methods: Forty-four STNs in 22 patients with Parkinson’s disease were investigated. The three-dimensional MRI-defined STN was derived from segmentations of axial and coronal T2-weighted images. The electrophysiological STNs were generated from intraoperative MERs in 1,487 locations. The stereotactical coordinates of positive and negative STN recordings were re-imported to the planning software, where a three-dimensional reconstruction of the electrophysiological STN was performed and fused to the MRI data set. The estimated borders of the MRI- and MERSTN were compared. For statistical analysis Student’s t, Mann-Whitney rank sum and Fisher’s exact tests were used.

Results: MER-STN volumes, which were found outside the MRI-STN, ranged from 0 mm3 to 87 mm3 (mean: 45 mm3). A mean of 44% of the MER-STN volumes exceeded the MRI-STN (maximum: 85.1%; minimum: 15.1 %); 53.4% (n=793) of the microelectrode recordings were concordant and 46.6% (n=694) discordant with the MRI-defined anatomical STN. Regarding the dorsal borders, we found discrepancies between the MER- and MRI-STN of 0.27 mm (= mean; SD: 0.51 mm) on the first operated side and 1.51 mm (SD: 1.5 mm) on the second (p=0.010, t-test).

Conclusions: MER provides additional information to highresolution anatomical MR images and may help to detect the amount and direction of brain shift.

Acta Neurochir (2011) 153:2293–2306. DOI 10.1007/s00701-011-1166-3

The indications for deep brain stimulation (DBS) are expanding, and the feasibility and efficacy of this surgical procedure in various neurologic and neuropsychiatric disorders continue to be tested.

This review attempts to provide background and rationale for applying this therapeutic option to obesity and addiction. We review neural targets currently under clinical investigation for DBS—the hypothalamus and nucleus accumbens—in conditions such as cluster headache and obsessive-compulsive disorder. These brain regions have also been strongly implicated in obesity and addiction. These disorders are frequently refractory, with very high rates of weight regain or relapse, respectively, despite the best available treatments.

Methods We performed a structured literature review of the animal studies of DBS, which revealed attenuation of food intake, increased metabolism, or decreased drug seeking. We also review the available radiologic evidence in humans, implicating the hypothalamus and nucleus in obesity and addiction.

Results The available evidence of the promise of DBS in these conditions combined with significant medical need, support pursuing pilot studies and clinical trials of DBS in order to decrease the risk of dietary and drug relapse.

Conclusions Well-designed pilot studies and clinical trials enrolling carefully selected patients with obesity or addiction should be initiated.

Neurosurgery 69:1015–1029, 2011 DOI: 10.1227/NEU.0b013e318229cfcd

A significant number of patients with major depressive disorder are unresponsive to conventional therapies. For these patients, neuromodulation approaches are being investigated.

OBJECTIVE: To determine whether epidural cortical stimulation at the left dorsolateral prefrontal cortex is safe and efficacious for major depressive disorder through a safety and feasibility study.

METHODS: Twelve patients were recruited in this randomized, single-blind, shamcontrolled study with a 104-week follow-up period. The main outcome measures were Hamilton Depression Rating Scale-28 (HDRS), Montgomery-Asberg Depression Rating Scale (MADRS), Global Assessment of Function (GAF), and Quality of Life Enjoyment and Satisfaction (QLES) questionnaire. An electrode was implanted over Brodmann area 9/46 in the left hemisphere. The electrode provided long-term stimulation to this target via its connections to an implanted neurostimulator in the chest.

RESULTS: During the sham-controlled phase, there was no statistical difference between sham and active stimulation, although a trend toward efficacy was seen with the active stimulation group. In the open-label phase, we observed a significant improvement in outcome scores for the HDRS, MADRS, and GAF but not the QLES (HDRS: df = 7, F = 7.72, P < .001; MADRS: df = 7, F = 8.2, P < .001; GAF: df = 5, F = 16.87, P < .001; QLES: df = 5, F = 1.32, P . .2; repeated measures ANOVA). With regard to the HDRS, 6 patients had ≥40% improvement, 5 patients had ≥ 50% improvement, and 4 subjects achieved remission (HDRS , 10) at some point during the study.

CONCLUSION: Epidural cortical stimulation of the left dorsolateral prefrontal cortex appears to be a safe and potentially efficacious neuromodulation approach for treatment- refractory major depressive disorder.

Neurosurgery 69:1124–1130, 2011 DOI: 10.1227/NEU.0b013e3182296a42

The ventralis intermedius (VIM) nucleus of the thalamus is the primary surgical target for treatment of tremor. Most centers rely on indirect targeting based on atlas-defined coordinates rather than patient-specific anatomy, making intraoperative physiological mapping critical. Detailed identification of this target based on patientspecific anatomic features can help optimize the surgical treatment of tremor.

OBJECTIVE: To study colored fractional anisotropic images and diffusion tensor imaging (DTI) tractography to identify characteristic magnetic resonance appearances of the VIM nucleus.

METHODS: Four patients undergoing stereotactic surgery for essential tremor (ET) were retrospectively studied with analysis of magnetic resonance imaging-based colored fractional anisotropy (FA) images and fiber tractography. All were scanned with a 1.5-T magnetic resonance imaging unit, and all sequences were obtained before frame placement. Because the goal of this study was to identify the DTI characteristics of physiologically defined VIM nucleus, we selected and studied patients who had undergone DTI and had efficacious tremor control with intraoperative microlesioning effect and tremor reduction with less than 2.0-V stimulation.

RESULTS: Analysis of color FA maps, which graphically illustrate fiber directionality, revealed consistent anatomic patterns. The region of the VIM nucleus can be seen as an intermediate region where there is a characteristic transition of color. Presumptive VIM nucleus interconnectivity with sensorimotor cortex and cerebellum was identified via the internal capsule and the superior cerebellar peduncle, respectively. FA maps could also be used to distinguish segments of gray matter, white matter, and gray-white matter boundaries.

CONCLUSION: Analysis of DTI and FA maps on widely available 1.5-T magnetic resonance imaging yields clear identification of various structures key to neurosurgical targeting. Prospective evaluation of integrating DTI into neurosurgical planning may be warranted.

Neuroradiology (2011) 53:787–791.DOI 10.1007/s00234-011-0878-7
The dentatorubrothalamic tract (DRTT) originates from the dentate nucleus in the cerebellum and terminates in the contralateral ventrolateral nucleus (VL) of the thalamus after decussating to the contralateral red nucleus. Identification of the DRTT is difficult due to the fact that it is a long, multisynaptic, neural tract crossing to the opposite hemisphere. In the current study, we attempted to identify the DRTT in the human brain using a probabilistic tractography technique of diffusion tensor imaging.
Methods Diffusion tensor imaging was performed at 1.5-T using a synergy-L sensitivity encoding head coil. DRTTs were obtained by selection of fibers passing through three regions of interest (the dentate nucleus, the superior cerebellar peduncle, and the contralateral red nucleus) from 41 healthy volunteers. Probabilistic mapping was obtained from the highest probabilistic location at 2.3 mm above the anterior commissure–posterior commissure level.
Results DRTTs of all subjects, which originated from the dentate nucleus, ascended through the junction of the superior cerebellar peduncle and the contralateral red nucleus and then terminated at the VL nucleus of the thalamus. The highest probabilistic location for the DRTT at the thalamus was compatible with the location of the VL nucleus.
Conclusions We identified the DRTT in the human brain using probabilistic tractography. Our results could be useful in research on movement control.

Neurosurgery 69:870–875, 2011 DOI: 10.1227/NEU.0b013e318222ae33

A variety of imaging strategies may be used to derive reliable stereotactic coordinates when performing deep brain stimulation lead implants. No single technique has yet proved optimal.

OBJECTIVE: To compare the relative accuracy of stereotactic coordinates for the subthalamic nucleus (STN) derived either from fast spin echo/inversion recovery (FSE/IR) magnetic resonance imaging MRI alone (group 1) or FSE/IR in conjunction with T1- weighted spoiled gradient-echo MRI (group 2).

METHODS: A retrospective analysis of 145 consecutive STN deep brain stimulation lead placements (group 1, n = 72; group 2, n = 73) was performed in 81 Parkinson disease patients by 1 surgical team. From the operative reports, we recorded the number of microelectrode recording trajectories required to localize the desired STN target and the span of STN traversed along the implantation trajectory. In addition, we calculated the 3-dimensional vector difference between the initial MRI-derived coordinates and the final physiologically refined coordinates.

RESULTS: The proportion of implants completed with just 1 microelectrode recording trajectory was greater (81% vs 58%; P < .001) and the 3-dimensional vector difference between the anatomically selected target and the microelectrode recording–refined target was smaller (0.6 ± 1.2 vs 0.9 ± 1.3; P = .04) in group 2 than in group 1. At the same time, the mean expanse of STN recorded along the implantation trajectory was 8% greater in group 2 (4.8 ± 0.6 vs 5.2 ± 0.6 mm; P < .001).

CONCLUSION: A combination of stereotactic FSE/IR and spoiled gradient-echo MRI yields more accurate coordinates for the STN than FSE/IR MRI alone.

J Neurosurg 115:852–857, 2011.DOI: 10.3171/2011.5.JNS101457

Deep brain stimulation (DBS) is an established neurosurgical technique used to treat a variety of neurological disorders, including Parkinson disease, essential tremor, dystonia, epilepsy, depression, and obsessive-compulsive disorder. This study reports on the use of intraoperative MR imaging during DBS surgery to evaluate acute hemorrhage, intracranial air, brain shift, and accuracy of lead placement.

Methods. During a 46-month period, 143 patients underwent 152 DBS surgeries including 289 lead placements utilizing intraoperative 1.5-T MR imaging. Imaging was supervised by an MR imaging physicist to maintain the specific absorption rate below the required level of 0.1 W/kg and always included T1 magnetization-prepared rapid gradient echo and T2* gradient echo sequences with selected use of T2 fluid attenuated inversion recovery (FLAIR) and T2 fast spin echo (FSE). Retrospective review of the intraoperative MR imaging examinations was performed to quantify the amount of hemorrhage and the amount of air introduced during the DBS surgery.

Results. Intraoperative MR imaging revealed 5 subdural hematomas, 3 subarachnoid hemorrhages, and 1 intraparenchymal hemorrhage in 9 of the 143 patients. Only 1 patient experiencing a subarachnoid hemorrhage developed clinically apparent symptoms, which included transient severe headache and mild confusion. Brain shift due to intracranial air was identified in 144 separate instances.

Conclusions. Intraoperative MR imaging can be safely performed and may assist in demonstrating acute changes involving intracranial hemorrhage and air during DBS surgery. These findings are rarely clinically significant and typically resolve prior to follow-up imaging. Selective use of T2 FLAIR and T2 FSE imaging can confirm the presence of hemorrhage or air and preclude the need for CT examinations

Neuroradiology(2011)53:787–791.DOI 10.1007/s00234-011-0878-7
The dentatorubrothalamic tract (DRTT) originates  from the dentate nucleus in the cerebellum and terminates in the contralateral ventrolateral nucleus (VL) of the thalamus after decussating to the contralateral red nucleus. Identification of the DRTT is difficult due to the fact that it is a long, multisynaptic, neural tract crossing to the opposite hemisphere.
In the current study, we attempted to identify the DRTT in the human brain using a probabilistic tractography technique of diffusion tensor imaging.
Methods Diffusion tensor imaging was performed at 1.5-T using a synergy-L sensitivity encoding head coil. DRTTs were obtained by selection of fibers passing through three regions of interest (the dentate nucleus, the superior cerebellar peduncle, and the contralateral red nucleus) from 41 healthy volunteers. Probabilistic mapping was obtained from the highest probabilistic location at 2.3 mm above the anterior commissure–posterior commissure level.
Results DRTTs of all subjects, which originated from the dentate nucleus, ascended through the junction of the superior cerebellar peduncle and the contralateral red nucleus and then terminated at the VL nucleus of the thalamus. The highest probabilistic location for the DRTT at the thalamus was compatible with the location of the VL nucleus.
Conclusions We identified the DRTT in the human brain using probabilistic tractography. Our results could be useful in research on movement control.

Neurosurgery 69:590–597, 2011 DOI: 10.1227/NEU.0b013e3182181be1

Functional magnetic resonance imaging (fMRI) is a less invasive way of mapping brain functions. The reliability of fMRI for localizing language-related function is yet to be determined.

OBJECTIVE: We performed a detailed analysis of language fMRI reliability by comparing the results of 3-T fMRI with maps determined by extraoperative electrocortical stimulation (ECS).

METHODS: This study was performed on 8 epileptic patients who underwent subdural electrode placement. The tasks performed during fMRI included verb generation, abstract/ concrete categorization, and picture naming. We focused on the frontal lobe, which was effectively activated by these tasks. In extraoperative ECS, 4 tasks were combined to determine the eloquent areas: spontaneous speech, picture naming, reading, and comprehension. We calculated the sensitivity and specificity with different Z score thresholds for each task and appropriate matching criteria. For further analysis, we divided the frontal lobe into 5 areas and investigated intergyrus variations in sensitivity and specificity.

RESULTS: The abstract/concrete categorization task was the most sensitive and specific task in fMRI, whereas the picture naming task detected eloquent areas most efficiently in ECS. The combination of the abstract/concrete categorization task and a 3-mm matching criterion gave the best tradeoff (sensitivity, 83%; specificity, 61%) when the Z score was 2.24. As for intergyrus variation, the posterior inferior frontal gyrus showed the best tradeoff (sensitivity, 91%; specificity, 59%), whereas the anterior middle frontal gyrus had low specificity.

CONCLUSION: Despite different tasks for fMRI and extraoperative ECS, the relatively low specificity might be caused by a fundamental discrepancy between the 2 techniques. Reliability of language fMRI activation might differ, depending on the brain region.

J Neurosurg 115:301–309, 2011. DOI: 10.3171/2011.3.JNS101642

Correct lead location in the desired target has been proven to be a strong influential factor for good clinical outcome in deep brain stimulation (DBS) surgery. Commonly, a surgeon’s first reliable assessment of such location is made on postoperative imaging. While intraoperative CT (iCT) and intraoperative MR imaging have been previously described, the authors present a series of frameless DBS procedures using O-arm iCT.

Methods. Twelve consecutive patients with 15 leads underwent frameless DBS placement using electrophysiological testing and O-arm iCT. Initial target coordinates were made using standard indirect and direct assessment. Microelectrode recording (MER) with kinesthetic responses was performed, followed by microstimulation to evaluate the side-effect profile. Intraoperative 3D CT acquisitions obtained between each MER pass and after final lead placement were fused with the preoperative MR image to verify intended MER movements around the target area and to identify the final lead location. Tip coordinates from the initial plan, final intended target, and actual lead location on iCT were later compared with the lead location on postoperative MR imaging, and euclidean distances were calculated. The amount of radiation exposure during each procedure was calculated and compared with the estimated radiation exposure if iCT was not performed.

Results. The mean euclidean distances between the coordinates for the initial plan, final intended target, and actual lead on iCT compared with the lead coordinates on postoperative MR imaging were 3.04 ± 1.45 mm (p = 0.0001), 2.62 ± 1.50 mm (p = 0.0001), and 1.52 ± 1.78 mm (p = 0.0052), respectively. The authors obtained good merging error during image fusion, and postoperative brain shift was minimal. The actual radiation exposure from iCT was invariably less than estimates of exposure using standard lateral fluoroscopy and anteroposterior radiographs (p < 0.0001).

Conclusions. O-arm iCT may be useful in frameless DBS surgery to approximate microelectrode or lead locations intraoperatively. Intraoperative CT, however, may not replace fundamental DBS surgical techniques such as electrophysiological testing in movement disorder surgery. Despite the lack of evidence for brain shift from the procedure, iCT-measured coordinates were statistically different from those obtained postoperatively, probably indicating image merging inaccuracy and the difficulties in accurately denoting lead location. Therefore, electrophysiological testing may truly be the only means of precisely knowing the location in 3D space intraoperatively. While iCT may provide clues to electrode or lead location during the procedure, its true utility may be in DBS procedures targeting areas where electrophysiology is less useful. The use of iCT appears to reduce radiation exposure compared with the authors’ traditional frameless technique.

Neurosurgery 69:294–300, 2011 DOI: 10.1227/NEU.0b013e318214abda

Deep brain stimulation (DBS) at the subthalamic nucleus (STN) is an effective treatment for the motor manifestations of advanced medically refractory Parkinson disease. Because of the medial location of the target, surgical trajectories to the STN may violate the ipsilateral lateral ventricle.

OBJECTIVE: To determine whether violating the ventricle during STN DBS surgery is associated with postoperative confusion.

METHODS: A retrospective chart review of all STN implantation procedures for Parkinson disease performed by 1 surgeon between January 2005 and September 2008 was performed. Postoperative magnetic resonance imaging was performed in all cases, and each scan was reviewed for evidence of ventricular wall violation. All charts were reviewed for postoperative confusion and/or increased length of hospital stay.

RESULTS: A total of 145 leads were implanted in 81 patients over 102 admissions. Fortythree patients underwent contemporaneous bilateral lead implantation; 23 underwent unilateral implantation; and 18 underwent staged bilateral implantation. The cases of 8 patients were complicated by postoperative confusion and increased length of stay. Sixteen magnetic resonance imaging scans demonstrated evidence of ventricular wall violation including all 8 patients with postoperative confusion. The relative risk of having postoperative confusion after traversing the ventricle is 87 (P , .001).

CONCLUSION: Violating the ventricular system during STN DBS surgery correlated significantly with postoperative altered mental status and subsequent increased length of hospital stay. This finding may explain why cognitive complications are observed more frequently in Parkinson disease patients undergoing DBS at the STN compared with the internal globus pallidus.

Neurosurgery 69:207–214, 2011 DOI: 10.1227/NEU.0b013e318218c7ae

Knowledge of the anatomic location of the deep brain stimulation (DBS) electrode in the brain is essential in quality control and judicious selection of stimulation parameters. Postoperative computed tomography (CT) imaging coregistered with preoperative magnetic resonance imaging (MRI) is commonly used to document the electrode location safely. The accuracy of this method, however, depends on many factors, including the quality of the source images, the area of signal artifact created by the DBS lead, and the fusion algorithm.

OBJECTIVE: To calculate the accuracy of determining the location of active contacts of the DBS electrode by coregistering postoperative CT image to intraoperative MRI.

METHODS: Intraoperative MRI with a surrogate marker (carbothane stylette) was digitally coregistered with postoperative CT with DBS electrodes in 8 consecutive patients. The location of the active contact of the DBS electrode was calculated in the stereotactic frame space, and the discrepancy between the 2 images was assessed.

RESULTS: The carbothane stylette significantly reduces the signal void on the MRI to a mean diameter of 1.4 6 0.1 mm. The discrepancy between the CT and MRI coregistration in assessing the active contact location of the DBS lead is 1.6 6 0.2 mm, P < .001 with iPlan (BrainLab AG, Erlangen, Germany) and 1.5 6 0.2 mm, P < .001 with Framelink (Medtronic, Minneapolis, Minnesota) software.

CONCLUSION: CT/MRI coregistration is an acceptable method of identifying the anatomic location of DBS electrode and active contacts.

Neurosurg Rev (2011) 34:373–380. DOI 10.1007/s10143-011-0310-0

The success of microvascular decompression stitched sling retraction techniques for treating trigeminal neuralgia (TN), hemifacial spasm (HFS), and glossopharyngeal neuralgia (GPN), focusing on the stitching point for slinging the offending artery in the appropriate direction.

Between January 2007 and March 2009, 28 patients with TN, 5 patients with HFS, and 3 patients with GPN underwent MVD with a sling retraction technique. In cases of TN, MVD was performed using the infratentorial lateral supracerebellar approach, and the offending superior cerebellar artery was superomedially transposed with a sling stitched to the tentorium cerebelli. In cases of HFS, MVD was performed using the lateral suboccipital infrafloccular approach, and the offending vertebral artery was superolaterally transposed with a sling stitched to the petrous dura. In cases of GPN, MVD was performed using the transcondylar fossa approach, in which the posterior inferior cerebellar artery was inferolaterally mobilized with a sling secured to the jugular tubercle. No patient suffered recurrence in the follow-up period.

For the sling retraction technique to be performed successfully, it is important for a stitch to be placed at a suitable site to sling the offending vessel in the intended direction. An appropriate surgical approach must be used to obtain a sufficient operative field for performing the stitching procedures safely.

Neurosurgery 68:E1501–E1505, 2011 DOI: 10.1227/NEU.0b013e318210c859

Camptocormia is characterized by abnormal flexion of the thoracolumbar spine that increases during upright posture and abates in the recumbent position and has been reported to occur in patients with Parkinson disease. Camptocormia causes significant spinal and abdominal pain, impairment of balance, and social stigma.

CLINICAL PRESENTATION: A 57-year-old woman with Parkinson disease developed severe camptocormia, which did not improve with trials of antiparkinsonian and muscle relaxant medications. The patient was successfully treated with bilateral globus pallidus interna deep brain stimulation surgery under general anesthesia. High-frequency neuromodulation afforded relief of camptocormia and improvement in Parkinson disease symptoms.

CONCLUSION: Camptocormia in Parkinson disease may represent a form of dystonia and can be treated effectively with chronic pallidal neuromodulation.

Acta Neurochir (2011) 153:1087–1095 DOI 10.1007/s00701-011-0953-1

Microelectrode recording (MER) is widely used during deep brain stimulation (DBS) procedures because MER can identify structural borders and eloquent structures, localize somatotopic arrangements, and provide an outline of the three-dimensional shapes of target nuclei. However, MER may cause intracranial hemorrhage. We performed single track MER during DBS procedures, analyzed the accuracy of electrode positioning with MRI, and compared the amount of air and the potential risk of intracranial hemorrhage.

Method A total of 46 electrodes were placed in 23 patients who suffered from advanced Parkinson’s disease and who underwent bilateral subthalamic nucleus DBS using single track MER. Each patient’s Unified Parkinson’s Disease Rating Scale (UPDRS) score and levo-dopa equivalent dosage (LED) were estimated pre- and postoperatively. The accuracy of electrode positioning and fontal air thickness was measured by a pre- or postoperative magnetic resonance imaging (MRI) merging technique.

Findings The mean electrode positioning error was 0.92 mm (0.3–2.94 mm). The mean frontal air thickness on postoperative MRI was 3.85 mm (0–10.3 mm), which did not affect the electrode accuracy statistically (p=0.730). A total of nine electrodes required repositioning after single-track MER because they affected microstimulation or because an abnormally short STN length was observed during MER. In this series, one patient suffered from an intracranial hemorrhage after surgery that appeared to be due to venous infarction rather than related to MER.

Conclusions Although MER can facilitate accurate positioning of electrodes, multi-track MER may increase the risk of intracranial hemorrhage. The accuracy of electrode positioning appears to be acceptable under single track MER during STN DBS with careful electrophysiological and neurological monitoring. The risk of intracranial hemorrhage appears to be minimal, especially in elderly patients with atrophic brains.

Neurosurgery 68:1069–1076, 2011 DOI: 10.1227/NEU.0b013e31820a1a20

Deep brain stimulation (DBS) has been proven to alleviate tremor of various origins. Distinct regions have been targeted. One explanation for good clinical tremor control might be the involvement of the dentatorubrothalamic tract (DRT) as has been suggested in superficial (thalamic) and inferior (posterior subthalamic) target regions. Beyond a correlation with atlas data and the postmortem evaluation of patients treated with lesion surgery, proof for the involvement of DRT in tremor reduction in the living, the scope of this work, is elusive.

OBJECTIVE: To report a case of unilateral refractory tremor in tremor-dominant Parkinson disease treated with thalamic DBS.

METHODS: Preoperative diffusion tensor imaging (DTI) was performed. Correlation with individual DBS electrode contact locations was obtained through postoperative fusion of helical computed tomography (CT) data with DTI fiber tracking.

RESULTS: Tremor was alleviated effectively. An evaluation of the active electrode contact position revealed clear involvement of the DRT in tremor control. A closer evaluation of clinical effects and side effects revealed a highly detailed individual fiber map of the subthalamic region with DTI fiber tracking.

CONCLUSION: This is the first time the involvement of the DRT in tremor reduction through DBS has been shown in the living. The combination of DTI with postoperative CT and the evaluation of the electrophysiological environment of distinct electrode contacts led to an individual detailed fiber map and might be extrapolated to refined DTI-based targeting strategies in the future. Data acquisition for a larger study group is the topic of our ongoing research.

Neurosurgery 68[ONS Suppl 1]:ons114–ons124, 2011. DOI: 10.1227/NEU.0b013e31820781bc

The efficacy of deep brain stimulation (DBS) is highly dependent on the accuracy of lead placement.

OBJECTIVE: To describe the use of intraoperative computed tomography (iCT) to confirm lead location before surgical closure and to study the accuracy of this technique.

METHODS: Fifteen patients underwent awake microelectrode-guided DBS surgery in a stereotactic frame. A portable iCT scanner (Medtronic O-arm) was positioned around the patient’s head throughout the procedure and was used to confirm lead location before fixation of the lead to the skull. Images were computationally fused with preoperative magnetic resonance imaging (MRI), and lead tip coordinates with respect to the midpoint of the anterior commissure-posterior commissure line were measured. Tip coordinates were compared with those obtained from postoperative MRI.

RESULTS: iCT was integrated into standard frame-based microelectrode-guided DBS surgery with a minimal increase in surgical time or complexity. Technically adequate 2-dimensional and 3-dimensional images were obtained in all cases. Head positioning and fixation techniques that allow unobstructed imaging are described. Lead tip measurements on iCT fused with preoperative MRI were statistically indistinguishable from those obtained with postoperative MRI.

CONCLUSION: iCT can be easily incorporated into standard DBS surgery, replaces the need for C-arm fluoroscopy, and provides accurate intraoperative 3-dimensional confirmation of electrode tip locations relative to preoperative images and surgical plans. iCT fused to preoperative MRI may obviate the need for routine postoperative MRI in DBS surgery. Technical nuances that must be mastered for the efficient use of iCT during DBS implantation are described.