Neurosurgery Blog

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Daily bibliographic review of the Neurosurgery Department. La Fe University Hospital. Valencia, Spain

Three-Dimensional Printed Modeling of Diffuse Low-Grade Gliomas and Associated White Matter Tract Anatomy

Neurosurgery 80:635–645, 2017

Diffuse low-grade gliomas (DLGGs) represent several pathological entities that infiltrate and invade cortical and subcortical structures in the brain.

OBJECTIVE: To describe methods for rapid prototyping of DLGGs and surgically relevant anatomy.

METHODS: Using high-definition imaging data and rapid prototyping technologies, we were able to generate 3 patient DLGGs to scale and represent the associated whitematter tracts in 3 dimensions using advanced diffusion tensor imaging techniques.

RESULTS: This report represents a novel application of 3-dimensional (3-D) printing in neurosurgery and a means to model individualized tumors in 3-D space with respect to subcorticalwhite matter tract anatomy. Faculty and resident evaluations of this technology were favorable at our institution.

CONCLUSION: Developing an understanding of the anatomic relationships existing within individuals is fundamental to successful neurosurgical therapy. Imaging-based rapid prototyping may improve on our ability to plan for and treat complex neuro-oncologic pathology.

Three-Dimensional Printed Modeling of Diffuse Low-Grade Gliomas and Associated White Matter Tract Anatomy

Neurosurgery 80:635–645, 2017

Diffuse low-grade gliomas (DLGGs) represent several pathological entities that infiltrate and invade cortical and subcortical structures in the brain.

OBJECTIVE: To describe methods for rapid prototyping of DLGGs and surgically relevant anatomy.

METHODS: Using high-definition imaging data and rapid prototyping technologies, we were able to generate 3 patient DLGGs to scale and represent the associated whitematter tracts in 3 dimensions using advanced diffusion tensor imaging techniques.

RESULTS: This report represents a novel application of 3-dimensional (3-D) printing in neurosurgery and a means to model individualized tumors in 3-D space with respect to subcorticalwhite matter tract anatomy. Faculty and resident evaluations of this technology were favorable at our institution.

CONCLUSION: Developing an understanding of the anatomic relationships existing within individuals is fundamental to successful neurosurgical therapy. Imaging-based rapid prototyping may improve on our ability to plan for and treat complex neuro-oncologic pathology.

Diffusion Tensor Imaging: A Possible Biomarker in Severe Traumatic Brain Injury and Aneurysmal Subarachnoid Hemorrhage?

diffusion-tensor-imaging-a-possible-biomarker-in-severe-traumatic-brain-injury-and-aneurysmal-subarachnoid-hemorrhage

Neurosurgery 79:786–793, 2016

A great need exists in traumatic brain injury (TBI) and aneurysmal subarachnoid hemorrhage (aSAH) for objective biomarkers to better characterize the disease process and to serve as early endpoints in clinical studies. Diffusion tensor imaging (DTI) has shown promise in TBI, but much less is known about aSAH.

OBJECTIVE: To explore the use of whole-brain DTI tractography in TBI and aSAH as a biomarker and early endpoint.

METHODS: Of a cohort of 43 patients with severe TBI (n = 20) or aSAH (n = 23) enrolled in a prospective, observational, multimodality monitoring study, DTI data were acquired at approximately day 12 (median, 12 days; interquartile range, 12-14 days) after injury in 22 patients (TBI, n = 12; aSAH, n = 10). Whole-brain DTI tractography was performed, and the following parameters quantified: average fractional anisotropy, mean diffusivity, tract length, and the total number of reconstructed fiber tracts. These were compared between TBI and aSAH patients and correlated with mortality and functional outcome assessed at 6 months by the Glasgow Outcome Scale Extended.

RESULTS: Significant differences were found for fractional anisotropy values (P = .01), total number of tracts (P = .03), and average tract length (P = .002) between survivors and nonsurvivors. A sensitivity analysis showed consistency of results between the TBI and aSAH patients for the various DTI measures.

CONCLUSION: DTI parameters, assessed at approximately day 12 after injury, correlated with mortality at 6 months in patients with severe TBI or aSAH. Similar patterns were found for both TBI and aSAH patients. This supports a potential role of DTI as early endpoint for clinical studies and a predictor of late mortality.

The evolving utility of diffusion tensor tractography in the surgical management of temporal lobe epilepsy

the-evolving-utility-of-diffusion-tensor-tractography-in-the-surgical-management-of-temporal-lobe-epilepsy

Acta Neurochir (2016) 158:2185–2193

Diffusion tensor imaging (DTI) is a relatively new imaging modality that has found many peri-operative applications in neurosurgery.

Methods A comprehensive survey of the applications of diffusion tensor imaging (DTI) in planning for temporal lobe epilepsy surgery was conducted. The presentation of this literature is supplemented by a case illustration.

Results The authors have found that DTI is well utilized in epilepsy surgery, primarily in the tractography of Meyer’s loop. DTI has also been used to demonstrate extratemporal connections that may be responsible for surgical failure as well as perioperative planning. The tractographic anatomy of the temporal lobe is discussed and presented with original DTI pictures.

Conclusions The uses of DTI in epilepsy surgery are varied and rapidly evolving. A discussion of the technology, its limitations, and its applications is well warranted and presented in this article.

In vivo visualization of the facial nerve in patients with acoustic neuroma using diffusion tensor imaging–based fiber tracking

study-of-facial-nerve-reconstruction

J Neurosurg 125:787–794, 2016

Preoperative determination of the facial nerve (FN) course is essential to preserving its function. Neither regular preoperative imaging examination nor intraoperative electrophysiological monitoring is able to determine the exact position of the FN. The diffusion tensor imaging–based fiber tracking (DTI-FT) technique has been widely used for the preoperative noninvasive visualization of the neural fasciculus in the white matter of brain. However, further studies are required to establish its role in the preoperative visualization of the FN in acoustic neuroma surgery. The object of this study is to evaluate the feasibility of using DTI-FT to visualize the FN.

Methods: Data from 15 patients with acoustic neuromas were collected using 3-T MRI. The visualized FN course and its position relative to the tumors were determined using DTI-FT with 3D Slicer software. The preoperative visualization results of FN tracking were verified using microscopic observation and electrophysiological monitoring during microsurgery.

Results: Preoperative visualization of the FN using DTI-FT was observed in 93.3% of the patients. However, in 92.9% of the patients, the FN visualization results were consistent with the actual surgery.

Conclusions: DTI-FT, in combination with intraoperative FN electrophysiological monitoring, demonstrated improved FN preservation in patients with acoustic neuroma. FN visualization mainly included the facial-vestibular nerve complex of the FN and vestibular nerve.

Human Connectome-Based Tractographic Atlas of the Brainstem Connections and Surgical Approaches

Human Connectome-Based Tractographic Atlas of the Brainstem Connections and Surgical Approaches

Neurosurgery 79:437–455, 2016

The brainstem is one of the most challenging areas for the neurosurgeon because of the limited space between gray matter nuclei and white matter pathways. Diffusion tensor imaging–based tractography has been used to study the brainstem structure, but the angular and spatial resolution could be improved further with advanced diffusion magnetic resonance imaging (MRI).

OBJECTIVE: To construct a high–angular/spatial resolution, wide-population–based, comprehensive tractography atlas that presents an anatomical review of the surgical approaches to the brainstem.

METHODS: We applied advanced diffusion MRI fiber tractography to a population-based atlas constructed with data from a total of 488 subjects from the Human Connectome Project-488. Five formalin-fixed brains were studied for surgical landmarks. Luxol Fast Blue–stained histological sections were used to validate the results of tractography.

RESULTS: We acquired the tractography of the major brainstem pathways and validated them with histological analysis. The pathways included the cerebellar peduncles, corticospinal tract, corticopontine tracts, medial lemniscus, lateral lemniscus, spinothalamic tract, rubrospinal tract, central tegmental tract, medial longitudinal fasciculus, and dorsal longitudinal fasciculus. Then, the reconstructed 3-dimensional brainstem structure was sectioned at the level of classic surgical approaches, namely supracollicular, infracollicular, lateral mesencephalic, perioculomotor, peritrigeminal, anterolateral (to the medulla), and retro-olivary approaches.

CONCLUSION: The advanced diffusion MRI fiber tracking is a powerful tool to explore the brainstem neuroanatomy and to achieve a better understanding of surgical approaches.

Fractional anisotropy in patients with disproportionately enlarged subarachnoid space hydrocephalus

Fractional anisotropy in patients with disproportionately enlarged subarachnoid space hydrocephalus

Acta Neurochir (2016) 158:1495–1500

Disproportionately enlarged subarachnoid space hydrocephalus (DESH) findings on MRI were described as a prognostic factor for responsiveness to the treatment of idiopathic normal pressure hydrocephalus (iNPH). Our premise is that DESH could be associated with compression of the cerebral white matter. Microstructural changes can be identified using diffusion tensor imaging (DTI), specifically fractional anisotropy (FA). The aim of this study is to compare FA in iNPH patients with and without DESH and healthy controls.

Methods: We analysed 1.5-T MRI scans of patients fulfilling the criteria of probable or possible iNPH and positive supplementary tests before and after surgery (ventriculo-peritoneal shunt). FA was measured in the anterior and posterior limb of the internal capsule (PLIC) and in the corpus callosum. Patients were divided into the DESH and non-DESH group. These data were also compared to FA values in the control group.

Results: Twenty-seven patients and 24 healthy controls were enrolled. DESH was present in 15 patients and lacking in 12. Twenty-three iNPH patients were shunt responders (85.2 %), and 4 were non-responders (14.8 %). All patients in the DESH group were shunt responders. In the non-DESH group, eight patients were responders (66.7 %). A significant difference between the DESH and non-DESH group was found in the FA of the PLIC. The mean value of FA in the PLIC was 0.72 in the DESH group and 0.66 in the non-DESH group. After the surgery FA decreased in both groups. In the DESH iNPH group FA PLIC decreased to 0.65 and in the non-DESH iNPH group to 0.60. In the healthy controls, the mean FA in the PLIC was 0.58.

Conclusion: DESH on MRI scans is related to a higher FA in the PLIC with a decrease after the surgery. It reflects a more severe compression of the white matter than in non-DESH patients or healthy volunteers. DESH patients had better outcome than non-DESH patients. This study confirmed the importance of DESH as a supportive sign for iNPH.

Visualization of Cranial Nerves Using High-Definition Fiber Tractography

Visualization of Cranial Nerves Using High-Definition Fiber Tractography

Neurosurgery 79:146–165, 2016

Recent studies have demonstrated diffusion tensor imaging tractography of cranial nerves (CNs). Spatial and angular resolution, however, is limited with this modality. A substantial improvement in image resolution can be achieved with high-angle diffusion magnetic resonance imaging and atlas-based fiber tracking to provide detailed trajectories of CNs.

OBJECTIVE: To use high-definition fiber tractography to identify CNs in healthy subjects and patients with brain tumors.

METHODS: Five neurologically healthy adults and 3 patients with brain tumors were scanned with diffusion spectrum imaging that allowed high-angular-resolution fiber tracking. In addition, a 488-subject diffusion magnetic resonance imaging template constructed from the Human Connectome Project data was used to conduct atlas space fiber tracking of CNs.

RESULTS: The cisternal portions of most CNs were tracked and visualized in each healthy subject and in atlas fiber tracking. The entire optic radiation, medial longitudinal fasciculus, spinal trigeminal nucleus/tract, petroclival portion of the abducens nerve, and intrabrainstem portion of the facial nerve from the root exit zone to the adjacent abducens nucleus were identified. This suggested that the high-angularresolution fiber tracking was able to distinguish the facial nerve from the vestibulocochlear nerve complex. The tractography clearly visualized CNs displaced by brain tumors. These tractography findings were confirmed intraoperatively.

CONCLUSION: Using high-angular-resolution fiber tracking and atlas-based fiber tracking, we were able to identify all CNs in unprecedented detail. This implies its potential in localization of CNs during surgical planning.

Autologous Mesenchymal Stem Cell Therapy for Spinal Cord Injury

A Phase III Clinical Trial Showing Limited Efficacy of Autologous Mesenchymal Stem Cell Therapy for Spinal Cord Injury

Neurosurgery 78:436–447, 2016

In our previous report, 3 of 10 patients with spinal cord injury who were injected with autologous mesenchymal stem cells (MSCs) showed motor improvement in the upper extremities and in activities of daily living.

OBJECTIVE: To report on the results of a phase III clinical trial of autologous MSCs therapy.

METHODS: Patients were selected based on the following criteria: chronic American Spinal Injury Association B status patients who had more than 12 months of cervical injury, and no neurological changes during the recent 3 months of vigorous rehabilitation. We injected 1.6 x10(7) autologous MSCs into the intramedullary area at the injured level and 3.2 x 10(7) autologous MSCs into the subdural space. Outcome data were collected over 6 months regarding neurological examination, magnetic resonance imaging with diffusion tensor imaging, and electrophysiological analyses.

RESULTS: Among the 16 patients, only 2 showed improvement in neurological status (unilateral right C8 segment from grade 1 to grade 3 in 1 patient and bilateral C6 from grade 3 to grade 4 and unilateral right C8 from grade 0 to grade 1 in 1 patient). Both patients with neurological improvement showed the appearance of continuity in the spinal cord tract by diffusion tensor imaging. There were no adverse effects associated with MSCs injection.

CONCLUSION: Single MSCs application to intramedullary and intradural space is safe, but has a very weak therapeutic effect compared with multiple MSCs injection. Further clinical trials to enhance the effect of MSCs injection are necessary.

DTI-MRI biomarkers in the search for normal pressure hydrocephalus aetiology

DTI chronic hydro

Neurosurg Rev (2015) 38:239–244

Normal pressure hydrocephalus (NPH) is a clinical syndrome characterized by gait disturbances, urinary incontinence and dementia. Clinical presentation overlaps with Alzheimer disease (AD).Early recognition thus early intervention (shunting) is important for successful treatment, but lack of a diagnostic test with sufficient sensitivity and specificity complicates the diagnosis.

We performed literature search and composed a structured review of imaging biomarkers of NPH. Morphometric studies are not sufficient to diagnose NPH. Hydrocephalus is a common finding in elderly people due to the symmetric brain atrophy and is even more pronounced in patients with AD. The key MRI biomarker seems to be diffusion tensor imaging (DTI). According to recent studies, the DTI analysis of the splenium corporis callosi, posterior limb of internal capsule, hippocampus and fornix combined with measurement of Evans index is a promising MRI biomarker of NPH and could be used for NPH diagnostics and in the differential diagnosis from AD and other dementias.

The utility of preoperative diffusion tensor imaging in the surgical management of brainstem cavernous malformations

The utility of preoperative diffusion tensor imaging in the surgical management of brainstem cavernous malformations

J Neurosurg 122:653–662, 2015

Resection of brainstem cavernous malformations (BSCMs) may reduce the risk of stepwise neurological deterioration secondary to hemorrhage, but the morbidity of surgery remains high. Diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) are neuroimaging techniques that may assist in the complex surgical planning necessary for these lesions. The authors evaluate the utility of preoperative DTI and DTT in the surgical management of BSCMs and their correlation with functional outcome.

Methods A retrospective review was conducted to identify patients who underwent resection of a BSCM between 2007 and 2012. All patients had preoperative DTI/DTT studies and a minimum of 6 months of clinical and radiographic follow-up. Five major fiber tracts were evaluated preoperatively using the DTI/DTT protocol: 1) corticospinal tract, 2) medial lemniscus and medial longitudinal fasciculus, 3) inferior cerebellar peduncle, 4) middle cerebellar peduncle, and 5) superior cerebellar peduncle. Scores were applied according to the degree of distortion seen, and the sum of scores was used for analysis. Functional outcomes were measured at hospital admission, discharge, and last clinic visit using modified Rankin Scale (mRS) scores.

Results Eleven patients who underwent resection of a BSCM and preoperative DTI were identified. The mean age at presentation was 49 years, with a male-to-female ratio of 1.75:1. Cranial nerve deficit was the most common presenting symptom (81.8%), followed by cerebellar signs or gait/balance difficulties (54.5%) and hemibody anesthesia (27.2%). The majority of the lesions were located within the pons (54.5%). The mean diameter and estimated volume of lesions were 1.21 cm and 1.93 cm3, respectively. Using DTI and DTT, 9 patients (82%) were found to have involvement of 2 or more major fiber tracts; the corticospinal tract and medial lemniscus/medial longitudinal fasciculus were the most commonly affected. In 2 patients with BSCMs without pial presentation, DTI/DTT findings were important in the selection of the surgical approach. In 2 other patients, the results from preoperative DTI/DTT were important for selection of brainstem entry zones. All 11 patients underwent gross-total resection of their BSCMs. After a mean postoperative follow-up duration of 32.04 months, all 11 patients had excellent or good outcome (mRS Score 0–3) at the time of last outpatient clinic evaluation. DTI score did not correlate with long-term outcome.

Conclusions Preoperative DTI and DTT should be considered in the resection of symptomatic BSCMs. These imaging studies may influence the selection of surgical approach or brainstem entry zones, especially in deep-seated lesions without pial or ependymal presentation. DTI/DTT findings may allow for more aggressive management of lesions previously considered surgically inaccessible. Preoperative DTI/DTT changes do not appear to correlate with functional postoperative outcome in long-term follow-up.

Modulation of the Cerebello-Thalamo-Cortical Network in Thalamic Deep Brain Stimulation for Tremor

Modulation of the Cerebello-Thalamo-Cortical Network in Thalamic Deep Brain Stimulation for Tremor- A Diffusion Tensor Imaging Study

Neurosurgery 75:657–670, 2014

Deep brain stimulation alleviates tremor of various origins. Several regions like the ventralis intermediate nucleus of thalamus, the caudal zona incerta, and the posterior subthalamic region are generally targeted. Previous work with fiber tractography has shown the involvement of the cerebello-thalamo-cortical network in tremor control.

OBJECTIVE: To report the results of a prospective trial in a group of patients with tremor who underwent post hoc tractographic analysis after treatment with traditional thalamic deep brain stimulation.

METHODS: A total of 11 patients (aged 64 6 17 years, 6 male) were enrolled (essential tremor [6], Parkinson tremor [3], and myoclonic tremor in myoclonus dystonia [2]). Patients received 1 (3 patients), 2 (7 patients), or 3 (1 patient) quadripolar electrodes. A 32-direction diffusion tensor magnetic resonance imaging sequence was acquired preoperatively. Tractography was processed postoperatively for evaluation and the dentato-rubro-thalamic tract (DRT) was individually tracked. Electrode positions were determined with helical computed tomography. Electric fields (EFs) were simulated according to individual stimulation parameters in a standardized atlas brain space (ICBMMNI 152).

RESULTS: Tremor was reduced in all patients (69.4% mean) on the global (bilateral) tremor score. Effective contacts were located inside or in proximity to the DRT. In moderate tremor reduction (2 patients), the EFs were centered on its anterior border. In good and excellent tremor reduction (9 patients), EFs focused on its center.

CONCLUSION: Deep brain stimulation of the cerebello-thalamo-cortical network reduces tremor. The DRT connects 3 traditional target regions for deep brain stimulation in tremor disease. Tractography techniques can be used to directly visualize the DRT and, therefore, optimize target definition in individual patients.

Diffusion tensor magnetic resonance imaging for predicting the consistency of intracranial meningiomas

Diffusion tensor magnetic resonance imaging for predicting the consistency of intracranial meningiomas

Acta Neurochir (2014) 156:1837–1845

The ability of preoperative MRI-sequences to predict the consistency of intracranial meningiomas has not yet been clearly defined.We aim to demonstrate that diffusion tensor imaging (DTI) improves the prediction of intracranial meningiomas consistency.

Methods We prospectively studied 110 meningioma patients operated on in a single center from March 1st to the 25th of May 2012. Demographic data, location and size of the tumor, peritumoral edema, T1WI, T2WI, proton density weighted (PDWI), fluid-attenuated inversion recover (FLAIR) sequences, and arterial spin labeling (ASL) perfusion were studied and compared with the gray matter signal to predict meningioma consistency. Diffusion tensor imaging (DTI) with fractional anisotropy (FA) and mean diffusivity (MD) maps were included in the preoperative MRI. Meningioma consistency was evaluated by the operating surgeon who was unaware of the neuroradiological findings.

Results In univariate analysis, meningioma size (diameter> 2 cm) and supratentorial or sphenoidal wing location were more frequently associated with hard-consistency meningiomas (p<0.05). In addition, isointense signal on MD maps (p=0.009), hyperintense signal on FA maps, and FA value > 0.3 (p=0.00001) were associated with hard-consistency tumors. Age and sex, T1WI, T2WI, PDWI, FLAIR, or ASL perfusion sequences and peritumoral edema were not significantly associated with meningioma consistency. In logistic regression analysis, the most accurate model (AUC: 0.9459) for predicting a hard-consistency meningioma shows that an isointense signal in MD-maps, a hyperintense signal in FA-maps, and an FA value of more than 0.3 have a significant predictive value.

Conclusions FA value and MD and FA maps are useful for prediction of meningioma consistency and, therefore, may be considered in the preoperative routine MRI examination of all patients with intracranial meningiomas.

Preoperative Imaging to Predict Intraoperative Changes in Tumor-to-Corticospinal Tract Distance

Preoperative Imaging to Predict Intraoperative Changes in Tumor-to-Corticospinal Tract Distance

Neurosurgery 75:23–30, 2014

Preoperative diffusion tensor imaging (DTI) is used to demonstrate corticospinal tract (CST) position. Intraoperative brain shifts may limit preoperative DTI value, and studies characterizing such shifts are lacking.

OBJECTIVE: To examine tumor characteristics that could predict intraoperative shift in tumor-to-CST distance using high-field intraoperative magnetic resonance imaging.

METHODS: We retrospectively evaluated preoperative and intraoperative DTIs, tumor pathology, and imaging characteristics of patients who underwent resection of an intraaxial tumor adjacent to the CST to identify covariates that significantly affected shift in tumor-to-CST distance. For validation, we analyzed data from a separate, 20-patient cohort.

RESULTS: In the first cohort, the mean intraoperative shift in the tumor-to-CST distance was 3.18 6 3.58 mm. The mean shift for the 20 patients with contrast and the 5 patients with non–contrast-enhancing tumors was 3.93 6 3.64 and 0.18 6 0.18 mm, respectively (P , .001). No association was found between intraoperative shift in tumor-to-CST distance and tumor pathology, tumor volume, edema volume, preoperative tumor-to- CST distance, or extent of resection. According to receiver-operating characteristic analysis, nonenhancement predicted a tumor-to-CST distance shift of #0.5 mm, with a sensitivity of 100% and a specificity of 75%. We validated these findings using the second cohort.

CONCLUSION: For nonenhancing intra-axial tumors, preoperative DTI is a reliable method for assessing intraoperative tumor-to-CST distance because of minimal intraoperative shift, a finding that is important in the interpretation of subcortical motor evoked potential to maximize extent of resection and to preserve motor function. In resection of intra-axial enhancing tumors, intraoperative imaging studies are crucial to compensate for brain shift.

Brainstem cavernoma surgery with the support of pre and postoperative diffusion tensor imaging

Brainstem cavernoma surgery

Neurosurg Rev (2014) 37:481–492

The spatial complexity of highly vulnerable structures makes surgical resection of brainstem cavernomas (BSC) a challenging procedure. Diffusion tensor imaging (DTI) allows for the visualization of white matter tracts and enables a better understanding of the anatomical location of corticospinal and sensory tracts before and after surgery.

We investigated the feasibility and clinical usefulness of DTI-based fiber tractography in patients with BSC.Pre- and postoperative DTI visualization of corticospinal and sensory tracts were retrospectively analyzed in 23 individuals with BSC. Preoperative and postoperative DTIfiber accuracy were associated to the neurological findings.

Preoperatively, the corticospinal tracts were visualized in 90%of the cases and the sensory tracts were visualized in 74 % of the cases. Postoperatively, the corticospinal tracts were visualized in 97 % of the cases and the sensory tracts could be visualized in 80 % of the cases. In all cases, the BSC had caused displacement, thinning, or interruption of the fiber tracts to various degrees. Tract visualization was associated with pre- and postoperative neurological findings. Postoperative damage of the corticospinal tracts was observed in two patients. On follow-up, the Patzold Rating (PR) improved in 19 out of 23 patients (83 %, p= 0.0002).

This study confirms that DTI tractography allows accurate and detailed white matter tract visualization in the brainstem, even when an intraaxial lesion affects this structure. Furthermore, visualizing the tracts adjacent to the lesion adds to our understanding of the distorted intrinsic brainstem anatomy and it may assists in planning the surgical approach in specific cases.

 

Fiber tractography of basal ganglia and cerebellum in PD

Fiber tractography of basal ganglia and cerebellum in PD

J Neurosurg 120:988–996, 2014

Stimulation of white matter pathways near targeted structures may contribute to therapeutic effects of deep brain stimulation (DBS) for patients with Parkinson disease (PD). Two tracts linking the basal ganglia and cerebellum have been described in primates: the subthalamopontocerebellar tract (SPCT) and the dentatothalamic tract (DTT). The authors used fiber tractography to evaluate white matter tracts that connect the cerebellum to the region of the basal ganglia in patients with PD who were candidates for DBS.

Methods. Fourteen patients with advanced PD underwent 3-T MRI, including 30-directional diffusion-weighted imaging sequences. Diffusion tensor tractography was performed using 2 regions of interest: ipsilateral subthalamic and red nuclei, and contralateral cerebellar hemisphere. Nine patients underwent subthalamic DBS, and the course of each tract was observed relative to the location of the most effective stimulation contact and the volume of tissue activated.

Results. In all patients 2 distinct tracts were identified that corresponded closely to the described anatomical features of the SPCT and DTT, respectively. The mean overall distance from the active contact to the DTT was 2.18 ± 0.35 mm, and the mean proportional distance relative to the volume of tissue activated was 1.35 ± 0.48. There was a nonsignificant trend toward better postoperative tremor control in patients with electrodes closer to the DTT.

Conclusions. The SPCT and the DTT may be related to the expression of symptoms in PD, and this may have implications for DBS targeting. The use of tractography to identify the DTT might assist with DBS targeting in the future.

Diffusion Tensor Imaging of the Spinal Cord

Diffusion_Tensor_Imaging_of_the_Spinal_Cord__

Neurosurgery 74:1–8, 2014

Diffusion tensor imaging (DTI) provides a measure of the directional diffusion of water molecules in tissues. The measurement of DTI indexes within the spinal cord provides a quantitative assessment of neural damage in various spinal cord pathologies.

DTI studies in animal models of spinal cord injury indicate that DTI is a reliable imaging technique with important histological and functional correlates. These studies demonstrate that DTI is a noninvasive marker of microstructural change within the spinal cord.

In human studies, spinal cord DTI shows definite changes in subjects with acute and chronic spinal cord injury, as well as cervical spondylotic myelopathy. Interestingly, changes in DTI indexes are visualized in regions of the cord, which appear normal on conventional magnetic resonance imaging and are remote from the site of cord compression.

Spinal cord DTI provides data that can help us understand underlying microstructural changes within the cord and assist in prognostication and planning of therapies. In this article, we review the use of DTI to investigate spinal cord pathology in animals and humans and describe advances in this technique that establish DTI as a promising biomarker for spinal cord disorders.

Real-Time Atlas-Based Stereotactic Neuronavigation

Real-Time Atlas-Based Stereotactic Neuronavigation

Neurosurgery 74:128–134, 2014

Surgery for tumors in eloquent brain faces immense challenges when attempting to maximize resection and avoid neurological deficits.

OBJECTIVE: In order to give the surgeon real-time atlas-based anatomic information linked to the patient’s anatomy, we developed a software-based interface between deformable anatomic templates (DATs) and an intraoperative navigation system.

METHODS: Magnetic resonance imaging (MRI), diffusion tensor imaging, and/or functional MRI were performed on 3 patients preoperatively for the purposes of tumor resection by the use of neuronavigation. The DAT was registered to the patients’ navigation coordinate system and utilized coordinates from the navigation system during surgery. This provided the surgeon with a list of proximal anatomic and functional structures and a real-time image of the atlas at that location fused to the patient’s MRI. The clinical feasibility of this approach was evaluated during the resection of 3 eloquent tumors (right postcentral gyrus, left inferior frontal gyrus, and left occipital cuneus gyrus).

RESULTS: Tumor resection was performed successfully in all 3 patients. With the use of the coordinates from the navigation system, anatomic and functional structures and their distances were visualized interactively during tumor resection by using the DAT.

CONCLUSION: This is a proof of concept that an interactive atlas-based navigation can provide detailed anatomic and functional information that supplements MRI, diffusion tensor imaging, and functional MRI. The atlas-based navigation generated distances to important anatomic structures from the navigation probe tip. It can be used to guide direct electrical stimulation and highlight areas to avoid during tumor resection.

Deformable Anatomic Templates Improve Analysis of Gliomas With Minimal Mass Effect in Eloquent Areas

Deformable Anatomic Templates Improve Analysis of Gliomas With Minimal Mass Effect in Eloquent Areas

Neurosurgery 73:534–542, 2013

Despite improvements in advanced magnetic resonance imaging and intraoperative mapping, cases remain in which it is difficult to determine whether viable eloquent structures are involved by a glioma. A novel software program, deformable anatomic templates (DAT), rapidly embeds the normal location of eloquent cortex and functional tracts in the magnetic resonance images of glioma-bearing brain.

OBJECTIVE: To investigate the feasibility of the DAT technique in patients with gliomas related to eloquent brain.

METHODS: Forty cases of gliomas (grade II-IV) with minimal mass effect were referred for a prospective preoperative and postoperative DAT analysis. The DAT results were compared with the patient’s functional magnetic resonance imaging, diffusion tensor imaging, operative stimulation, and new postoperative clinical deficits.

RESULTS: Fifteen of the 40 glioma patients had overlap between tumor and eloquent structures. Immediate postoperative neurological deficits were seen in 9 cases in which the DAT showed the eloquent area both within the tumor and within or at the edge of the resection cavity. In 6 cases with no deficits, DAT placed the eloquent area in the tumor but outside the resection cavity.

CONCLUSION: This is proof of concept that DAT can improve the analysis of diffuse gliomas of any grade by efficiently alerting the surgeon to the possibility of eloquent area invasion. The technique is especially helpful in diffuse glioma because these tumors tend to infiltrate rather than displace eloquent structures. DAT is limited by tract displacement in gliomas that produces moderate to severe mass effect.

White matter fiber tractography: why we need to move beyond DTI

DTI

J Neurosurg 118:1367–1377, 2013

Diffusion-based MRI tractography is an imaging tool increasingly used in neurosurgical procedures to generate 3D maps of white matter pathways as an aid to identifying safe margins of resection. The majority of white matter fiber tractography software packages currently available to clinicians rely on a fundamentally flawed framework to generate fiber orientations from diffusion-weighted data, namely diffusion tensor imaging (DTI). This work provides the first extensive and systematic exploration of the practical limitations of DTI-based tractography and investigates whether the higher-order tractography model constrained spherical deconvolution provides a reasonable solution to these problems within a clinically feasible timeframe.

Methods. Comparison of tractography methodologies in visualizing the corticospinal tracts was made using the diffusion-weighted data sets from 45 healthy controls and 10 patients undergoing presurgical imaging assessment. Tensor-based and constrained spherical deconvolution–based tractography methodologies were applied to both patients and controls.

Results. Diffusion tensor imaging–based tractography methods (using both deterministic and probabilistic tractography algorithms) substantially underestimated the extent of tracks connecting to the sensorimotor cortex in all participants in the control group. In contrast, the constrained spherical deconvolution tractography method consistently produced the biologically expected fan-shaped configuration of tracks. In the clinical cases, in which tractography was performed to visualize the corticospinal pathways in patients with concomitant risk of neurological deficit following neurosurgical resection, the constrained spherical deconvolution–based and tensor-based tractography methodologies indicated very different apparent safe margins of resection; the constrained spherical deconvolution– based method identified corticospinal tracts extending to the entire sensorimotor cortex, while the tensor-based method only identified a narrow subset of tracts extending medially to the vertex.

Conclusions. This comprehensive study shows that the most widely used clinical tractography method (diffusion tensor imaging–based tractography) results in systematically unreliable and clinically misleading information. The higher-order tractography model, using the same diffusion-weighted data, clearly demonstrates fiber tracts more accurately, providing improved estimates of safety margins that may be useful in neurosurgical procedures. We therefore need to move beyond the diffusion tensor framework if we are to begin to provide neurosurgeons with biologically reliable tractography information.

Neurosurgery Department. “La Fe” University Hospital. Valencia, Spain

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Neurosurgery CNS: Flash Fluorescence for MCA Bypass Video 1

Neurosurgery CNS: Endoscopic Transventricular Lamina Terminalis Fenestration Video 2

Neurosurgery CNS: Endoscopic Transventricular Lamina Terminalis Fenestration Video 1

Neurosurgery CNS: Surgery for Giant PCOM Aneurysms Video 2

Neurosurgery CNS: Surgery for Giant PCOM Aneurysms Video 1

NeurosurgeryCNS: Endovascular-Surgical Approach to Cavernous dAVF

Neurosurgery CNS: Lateral Supraorbital Approach Applied to Anterior Clinoidal Meningiomas Video 4

Neurosurgery CNS: Lateral Supraorbital Approach Applied to Anterior Clinoidal Meningiomas Video 3

Neurosurgery CNS: Lateral Supraorbital Approach Applied to Anterior Clinoidal Meningiomas Video 2

Neurosurgery CNS: Lateral Supraorbital Approach Applied to Anterior Clinoidal Meningiomas Video 1

NeurosurgeryCNS: Surgery of AVMs in Motor Areas

NeurosurgeryCNS: The Fenestrated Yaşargil T-Bar Clip

NeurosurgeryCNS: Cotton-Clipping Technique to Repair Intraoperative Aneurysm Neck Tear Video 3

NeurosurgeryCNS: Cotton-Clipping Technique to Repair Intraoperative Aneurysm Neck Tear Video 2

NeurosurgeryCNS: Cotton-Clipping Technique to Repair Intraoperative Aneurysm Neck Tear Video 1

NeurosurgeryCNS. ‘Double-Stick Tape’ Technique for Offending Vessel Transposition in Microvascular Decompression

NeurosurgeryCNS: Advances in the Treatment and Outcome of Brain Stem Cavernous Malformation Surgery: 300 Patients

3T MRI Integrated Neuro Suite

NeurosurgeryCNS: 3D In Vivo Modeling of Vestibular Schwannomas and Surrounding Cranial Nerves Using DIT

NeurosurgeryCNS: Microsurgery for Previously Coiled Aneurysms: Experience on 81 Patients: Video 7

NeurosurgeryCNS: Microsurgery for Previously Coiled Aneurysms: Experience on 81 Patients: Video 6

NeurosurgeryCNS: Microsurgery for Previously Coiled Aneurysms: Experience on 81 Patients: Video 5

NeurosurgeryCNS: Microsurgery for Previously Coiled Aneurysms: Experience on 81 Patients: Video 4

NeurosurgeryCNS: Microsurgery for Previously Coiled Aneurysms: Experience on 81 Patients: Video 3

NeurosurgeryCNS: Microsurgery for Previously Coiled Aneurysms: Experience on 81 Patients: Video 2

NeurosurgeryCNS: Microsurgery for Previously Coiled Aneurysms: Experience on 81 Patients: Video 1

NeurosurgeryCNS: Corticotomy Closure Avoids Subdural Collections After Hemispherotomy

NeurosurgeryCNS: Operative Nuances of Side-to-Side in Situ PICA-PICA Bypass Procedure

NeurosurgeryCNS. Waterjet Dissection in Neurosurgery: An Update After 208 Procedures: Video 3

NeurosurgeryCNS. Waterjet Dissection in Neurosurgery: An Update After 208 Procedures: Video 2

NeurosurgeryCNS. Waterjet Dissection in Neurosurgery: An Update After 208 Procedures: Video 1

NeurosurgeryCNS: Fusiform Aneurysms of the Anterior Communicating Artery

NeurosurgeryCNS. Initial Clinical Experience with a High Definition Exoscope System for Microneurosurgery

NeurosurgeryCNS: Endoscopic Treatment of Arachnoid Cysts Video 2

NeurosurgeryCNS: Endoscopic Treatment of Arachnoid Cysts Video 1

NeurosurgeryCNS: Typical colloid cyst at the foramen of Monro.

NeurosurgeryCNS: Neuronavigation for Neuroendoscopic Surgery

NeurosurgeryCNS:New Aneurysm Clip System for Particularly Complex Aneurysm Surgery

NeurosurgeryCNS: AICA/PICA Anatomical Variants Penetrating the Subarcuate Fossa Dura

Craniopharyngioma Supra-Orbital Removal

NeurosurgeryCNS: Use of Flexible Hollow-Core CO2 Laser in Microsurgical Resection of CNS Lesions

NeurosurgeryCNS: Ulnar Nerve Decompression

NeurosurgeryCNS: Microvascular decompression for hemifacial spasm

NeurosurgeryCNS: ICG Videoangiography

NeurosurgeryCNS: Inappropiate aneurysm clip applications


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