Neurosurgery Blog


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

Probabilistic versus deterministic tractography for delineation of the cortico-subthalamic hyperdirect pathway in patients with Parkinson disease selected for deep brain stimulation

J Neurosurg 126:1657–1668, 2017

Diffusion-weighted MRI (DWI) and tractography allows noninvasive mapping of the structural connections of the brain, and may provide important information for neurosurgical planning. The hyperdirect pathway, connecting the subthalamic nucleus (STN) with the motor cortex, is assumed to play a key role in mediating the effects of deep brain stimulation (DBS), which is an effective but poorly understood treatment for Parkinson disease. This study aimed to apply recent methodological advances in DWI acquisition and analysis to the delineation of the hyperdirect pathway in patients with Parkinson disease selected for surgery.

METHODS High spatial and angular resolution DWI data were acquired preoperatively from 5 patients with Parkinson disease undergoing DBS. The authors compared the delineated hyperdirect pathways and associated STN target maps generated by 2 different tractography methods: a tensor-based deterministic method, typically available in clinical settings, and an advanced probabilistic method based on constrained spherical deconvolution. In addition, 10 highresolution data sets with the same scanning parameters were acquired from a healthy control participant to assess the robustness of the tractography results.

RESULTS Both tractography approaches identified connections between the ipsilateral motor cortex and the STN. However, the 2 methods provided substantially different target regions in the STN, with the target center of gravity differing by > 1.4 mm on average. The probabilistic method (based on constrained spherical deconvolution) plausibly reconstructed a continuous set of connections from the motor cortex, terminating in the dorsolateral region of the STN. In contrast, the tensor-based method reconstructed a comparatively sparser and more variable subset of connections. Furthermore, across the control scans, the probabilistic method identified considerably more consistent targeting regions within the STN compared with the deterministic tensor-based method, which demonstrated a 1.9–2.4 times higher variation.

CONCLUSIONS These data provide a strong impetus for the use of a robust probabilistic tractography framework based on constrained spherical deconvolution, or similar advanced DWI models, in clinical settings. The inherent limitations and demonstrated inaccuracy of the tensor-based method leave it questionable for use in high-precision stereotactic DBS surgery. The authors have also described a straightforward method for importing tractography-derived information into any clinical neuronavigation system, based on the generation of track-density images.

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.

The Impact of Intracranial Tumor Proximity to White Matter Tracts on Morbidity and Mortality

Neurosurgery 80:193–200, 2017

Using difusion tensor imaging (DTI) in neurosurgical planning allows identification of white matter tracts and has been associated with a reduction in postoperative functional deficits.
OBJECTIVE: This study explores the relationship between the lesion-to-tract distance (LTD) and postoperative morbidity and mortality in patients with brain tumors in order to evaluate the role of DTI in predicting postoperative outcomes.

METHODS: Adult patients with brain tumors (n = 60) underwent preoperative DTI. Three major white matter pathways (superior longitudinal fasciculi [SLF], cingulum, and corticospinal tract) were identified using DTI images, and the shortest LTD was measured for each tract. Postoperative morbidity and mortality information was collected from electronic medical records.

RESULTS: The ipsilesional corticospinal tract LTD and left SLF LTD were significantly associated with the occurrence rate of total postoperative motor (P = .018) and language (P < .001) deficits, respectively. The left SLF LTD was also significantly associated with the occurrence rate of new postoperative language deficits (P = .003), and the LTD threshold that best predicted this occurrence was 1 cm (P < .001). Kaplan–Meier log-rank survival analyses in patients having high-grade tumors demonstrated a significantly higher mortality for patients with a left SLF LTD <1 cm (P = .01).

CONCLUSION: Measuring tumor proximity to major white matter tracts using DTI can inform clinicians of the likelihood of postoperative functional deficits. A distance of 1 cm or less from eloquent white matter structures most significantly predicts the occurrence of new deficits with current surgical and imaging techniques.


Prognostic value of corpus callosum injuries in severe head trauma

Acta Neurochir (2017) 159:25–32

This study was performed to investigate the relationship between corpus callosum (CC) injury and prognosis in traumatic axonal injury (TAI).

Method: We retrospectively reviewed 264 patients with severe head trauma who underwent a conventional MR imaging in the first 60 days after injury. They were selected from a prospectively collected database of 1048 patients with severe head trauma admitted in our hospital. TAI lesions were defined as areas of increased signal intensity on T2 and FLAIR or areas of decreased signal on gradient-echo T2. We attempted to determine whether any MR imaging findings of TAI lesions at CC could be related to prognosis. Neurological impairment was assessed at 1 year after injury by means of GOS-E (good outcome being GOS-E 4/5 and bad outcome being GOS-E <4). We adjusted the multivariable analysis for the prognostic factors according to the IMPACT studies: the Core model (age, motor score at admission, and pupillary reactivity) and the Extended model (including CT information and second insults).

Results: We found 97 patients (37 %) with TAI at CC and 167 patients (63 %) without CC lesions at MR. A total of 62 % of the patients with CC lesions had poor outcome, whereas 38 % showed good prognosis. The presence of TAI lesions at the corpus callosum was associated with poor outcome 1 year after brain trauma (p < 0.001, OR 3.8, 95 % CI: 2.04–7.06). The volume of CC lesions measured on T2 and FLAIR se- quences was negatively correlated with the GOS-E after ad- justment for independent prognostic factors (p = 0.01, OR 2.23, 95 % CI:1.17–4.26). Also the presence of lesions at splenium was statistically related to worse prognosis (p = 0.002, OR 8.1, 95 % CI: 2.2–29.82). We did not find statistical significance in outcome between hemorrhagic and non-hemorrhagic CC lesions.

Conclusions: The presence of CC is associated with a poor outcome. The total volume of the CC lesion is an independent prognostic factor for poor outcome in severe head trauma.

Fractal Analysis for the Differentiation of Brain Tumors Using 3-Tesla Magnetic Resonance Susceptibility-Weighted Imaging

Neurosurgery 79:839–846, 2016

Susceptibility-weighted imaging (SWI) of brain tumors provides information about neoplastic vasculature and intratumoral micro- and macrobleedings. Low- and high-grade gliomas can be distinguished by SWI due to their different vascular characteristics. Fractal analysis allows for quantification of these radiological differences by a computer-based morphological assessment of SWI patterns.

OBJECTIVE: To show the feasibility of SWI analysis on 3-T magnetic resonance imaging to distinguish different kinds of brain tumors.

METHODS: Seventy-eight patients affected by brain tumors of different histopathology (low- and high-grade gliomas, metastases, meningiomas, lymphomas) were included. All patients underwent preoperative 3-T magnetic resonance imaging including SWI, on which the lesions were contoured. The images underwent automated computation, extracting 2 quantitative parameters: the volume fraction of SWI signals within the tumors (signal ratio) and the morphological self-similar features (fractal dimension [FD]). The results were then correlated with each histopathological type of tumor.

RESULTS: Signal ratio and FD were able to differentiate low-grade gliomas from grade III and IV gliomas, metastases, and meningiomas (P , .05). FD was statistically different between lymphomas and high-grade gliomas (P , .05). A receiver-operating characteristic analysis showed that the optimal cutoff value for differentiating low- from highgrade gliomas was 1.75 for FD (sensitivity, 81%; specificity, 89%) and 0.03 for signal ratio (sensitivity, 80%; specificity, 86%).

CONCLUSION: FD of SWI on 3-T magnetic resonance imaging is a novel image biomarker for glioma grading and brain tumor characterization. Computational models offer promising results that may improve diagnosis and open perspectives in the radiological assessment of brain tumors.

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


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


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.

Interventional magnetic resonance imaging‑guided subthalamic nucleus deep brain stimulation for Parkinson’s disease: Patient selection


Surg Neurol Int 02-Aug-2016;7:

Interventional magnetic resonance imaging (iMRI) guided deep brain stimulation (DBS) for Parkinson’s disease (PD) has been shown to be effective. The costs of a dedicated intraoperative MRI may be prohibitive. The procedure can also be performed in a diagnostic scanner, however this presents challenges for utilization of time when the scanner is used both as a diagnostic and an interventional unit. This report outlines our novel methodology for patient selection for implantation in a diagnostic MR scanner, as an attempt to streamline the use of resources. A retrospective review of our outcomes is also presented.

Methods: DBS candidacy evaluation included a PD questionnaire‑39. Anxiety, age, difficulties in communication and body habitus were factors that were assessed in selecting patients for this technique. Eleven patients underwent iMRI‑guided DBS implantation in the subthalamic nucleus. All patients were implanted bilaterally. Unified PD rating scale (UPDRS) part III and L‑dopa dose were compared pre‑ and post‑stimulation. A cohort of 11 DBS patients not selected for iMRI‑guided DBS were also reported for comparison.

Results: For the iMRI‑guided patients, mean “Off” UPDRS III score was 47.6 (standard deviation [SD] 8.26). Postoperative “On” medication, “On” stimulation UPDRS III was 13.6 (SD 5.23). Mean preoperative L‑dopa dose was 1060 mg (SD 474.3) and mean postoperative L‑dopa dose was 320 (SD 298.3).

Conclusion: iMRI‑guided DBS is a newly emerging technique for surgical treatment of patients with PD. We present a novel scoring system for patient selection assessing anxiety, age, ability to communicate, and body habitus to identify patients who will be benefited most from this technique.

Resting-state functional MRI in an intraoperative MRI setting

Resting-state functional MRI in an intraoperative MRI setting-1

J Neurosurg 125:401–409, 2016

The authors’ aim in this paper is to prove the feasibility of resting-state (RS) functional MRI (fMRI) in an intraoperative setting (iRS-fMRI) and to correlate findings with the clinical condition of patients pre- and postoperatively.

Methods: Twelve patients underwent intraoperative MRI-guided resection of lesions in or directly adjacent to the central region and/or pyramidal tract. Intraoperative RS (iRS)–fMRI was performed pre- and intraoperatively and was correlated with patients’ postoperative clinical condition, as well as with intraoperative monitoring results. Independent component analysis (ICA) was used to postprocess the RS-fMRI data concerning the sensorimotor networks, and the mean z-scores were statistically analyzed.

Results: iRS-fMRI in anesthetized patients proved to be feasible and analysis revealed no significant differences in preoperative z-scores between the sensorimotor areas ipsi- and contralateral to the tumor. A significant decrease in z-score (p < 0.01) was seen in patients with new neurological deficits postoperatively. The intraoperative z-score in the hemisphere ipsilateral to the tumor had a significant negative correlation with the degree of paresis immediately after the operation (r = -0.67, p < 0.001) and on the day of discharge from the hospital (r = -0.65, p < 0.001). Receiver operating characteristic curve analysis demonstrated moderate prognostic value of the intraoperative z-score (area under the curve 0.84) for the paresis score at patient discharge.

Conclusions: The use of iRS-fMRI with ICA-based postprocessing and functional activity mapping is feasible and the results may correlate with clinical parameters, demonstrating a significant negative correlation between the intensity of the iRS-fMRI signal and the postoperative neurological changes.

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.

Fiber tracking for temporal tumors

Distinct displacements of the optic radiation based on tumor location revealed using preoperative diffusion tensor imaging

J Neurosurg 124:1343–1352, 2016

Visual field defects (VFDs) due to optic radiation (OR) injury are a common complication of temporal lobe surgery. The authors analyzed whether preoperative visualization of the optic tract would reduce this complication by influencing the surgeon’s decisions about surgical approaches. The authors also determined whether white matter shifts caused by temporal lobe tumors would follow predetermined patterns based on the tumor’s topography.

Methods One hundred thirteen patients with intraaxial tumors of the temporal lobe underwent preoperative diffusion tensor imaging (DTI) fiber tracking. In 54 of those patients, both pre- and postoperative VFDs were documented using computerized perimetry. Brainlab’s iPlan 2.5 navigation software was used for tumor reconstruction and fiber visualization after the fusion of DTI studies with their respective magnetization-prepared rapid gradient-echo (MP-RAGE) images. The tracking algorithm was as follows: minimum fiber length 100 mm, fractional anisotropy threshold 0.1. The lateral geniculate body and the calcarine cortex were employed as tract seeding points. Shifts of the OR caused by tumor were visualized in comparison with the fiber tracking of the patient’s healthy hemisphere.

Results Temporal tumors produced a dislocation of the OR but no apparent fiber destruction. The shift of white matter tracts followed fixed patterns dependent on tumor location: Temporolateral tumors resulted in a medial fiber shift, and thus a lateral transcortical approach is recommended. Temporopolar tumors led to a posterior shift, always including Meyer’s loop; therefore, a pterional transcortical approach is recommended. Temporomesial tumors produced a lateral and superior shift; thus, a transsylvian-transcisternal approach will result in maximum sparing of the fibers. Temporocentric tumors also induced a lateral fiber shift. For those tumors, a transsylvian-transopercular approach is recommended. Tumors of the fusiform gyrus generated a superior (and lateral) shift; consequently, a subtemporal approach is recommended to avoid white matter injury. In applying the approaches recommended above, new or worsened VFDs occurred in 4% of the patient cohort. Total neurological and surgical morbidity were less than 10%. In 90% of patients, gross-total resection was accomplished.

Conclusions Preoperative visualization of the OR may help in avoiding postoperative VFDs.

fMRI activation in the middle frontal gyrus as an indicator of hemispheric dominance for language in brain tumor patients: a comparison with Broca’s area

Functional imaging

Neuroradiology (2016) 58:513–520

Functional MRI (fMRI) can assess language lateralization in brain tumor patients; however, this can be limited if the primary language area—Broca’s area (BA)—is affected by the tumor. We hypothesized that the middle frontal gyrus (MFG) can be used as a clinical indicator of hemispheric dominance for language during presurgical workup.

Methods: Fifty-two right-handed subjects with solitary left hemispheric primary brain tumors were retrospectively studied. Subjects performed a verbal fluency task during fMRI. The MFG was compared to BA for fMRI voxel activation, language laterality index (LI), and the effect of tumor grade on the LI.

Results: Language fMRI (verbal fluency) activated more voxels in MFG than in BA (MFG=315, BA=216, p<0.001). Voxel activations in the left-hemispheric MFG and BA were positively correlated (r = 0.69, p < 0.001). Mean LI in the MFG was comparable to that in BA (MFG = 0.48, BA = 0.39, p = 0.06). LIs in MFG and BA were positively correlated (r = 0.62, p < 0.001). Subjects with high- grade tumors demonstrate lower language lateralization than those with low-grade tumors in both BA and MFG (p = 0.02, p = 0.02, respectively).

Conclusion: MFG is comparable to BA in its ability to indicate hemispheric dominance for language using a measure of verbal fluency and may be an adjunct measure in the clinical determination of language laterality for presurgical planning.

Assessing size of pituitary adenomas: a comparison of qualitative and quantitative methods on MR

Assessing size of pituitary adenomas- a comparison of qualitative and quantitative methods on MR

Acta Neurochir (2016) 158:677–683

A variety of methods are used for estimating pituitary tumour size in clinical practice and in research. Quantitative methods, such as maximum tumour dimension, and qualitative methods, such as Hardy and Knosp grades, are well established but do not give an accurate assessment of the tumour volume. We therefore sought to compare existing measures of pituitary tumours with more quantitative methods of tumour volume estimation.

Method Magnetic resonance imaging was reviewed for 99 consecutive patients with pituitary adenomas awaiting surgery between 2010 and 2013. Maximal tumour diameter, Hardy and Knosp grades were compared with tumour volume estimates by the ellipsoid equation, [4/3 π (a.b.c) ], (i.e. ellipsoid volume) and slice-by-slice perimetry (i.e. perimeter volume).

Results Ellipsoid and perimeter methods of tumour volume estimation strongly correlated (R2 = 0.99, p < 0.0001). However the correlation was less strong with increasing tumour size, with the ellipsoid method slightly underestimating. The mean differences were −0.11 (95 % CI, −0.35, 0.14), −0.74 (95 % CI, −2.2, 0.74) and −1.4 (95 % CI, −6.4, 3.7) for micro-tumours, macro-tumours and giant tumours respectively. Tumour volume correlated with maximal diameter, fol- lowing a cubic distribution. Correlations of tumour volume with Hardy and Knosp grades was less strong.

Conclusions Perimeter and ellipsoid methods give a good estimation of tumour volume, whereas Knosp and Hardy grades may offer other clinically relevant information, such as cavernous sinus invasion or chiasmal compression. Thus the different methods of estimating tumour size are likely to have different clinical utilities.

Combining 5-Aminolevulinic Acid Fluorescence and Intraoperative Magnetic Resonance Imaging in Glioblastoma Surgery

Combining 5-Aminolevulinic Acid Fluorescence and Intraoperative Magnetic Resonance Imaging in Glioblastoma Surgery

Neurosurgery 78:475–483, 2016

Glioblastoma resection guided by 5-aminolevulinic acid (5-ALA) fluorescence and intraoperative magnetic resonance imaging (iMRI) may improve surgical results and prolong survival.

OBJECTIVE: To evaluate 5-ALA fluorescence combined with subsequent low-field iMRI for resection control in glioblastoma surgery.

METHODS: Fourteen patients with suspected glioblastoma suitable for complete resection of contrast-enhancing portions were enrolled. The surgery was carried out using 5-ALA–induced fluorescence and frameless navigation. Areas suspicious for tumor underwent biopsy. After complete resection of fluorescent tissue, low-field iMRI was performed. Areas suspicious for tumor remnant underwent biopsy under navigation guidance and were resected. The histological analysis was blinded.

RESULTS: In 13 of 14 cases, the diagnosis was glioblastoma multiforme. One lymphoma and 1 case without fluorescence were excluded. In 11 of 12 operations, residual contrast enhancement on iMRI was found after complete resection of 5-ALA fluorescent tissue. In 1 case, the iMRI enhancement was in an eloquent area and did not undergo a biopsy. The 28 biopsies of areas suspicious for tumor on iMRI in the remaining 10 cases showed tumor in 39.3%, infiltration zone in 25%, reactive central nervous system tissue in 32.1%, and normal brain in 3.6%. Ninety-three fluorescent and 24 non-fluorescent tissue samples collected before iMRI contained tumor in 95.7% and 87.5%, respectively.

CONCLUSION: 5-ALA fluorescence–guided resection may leave some glioblastoma tissue undetected. MRI might detect areas suspicious for tumor even after complete resection of all fluorescent tissue; however, due to the limited accuracy of iMRI in predicting tumor remnant (64.3%), resection of this tissue has to be considered with caution in eloquent regions.

Orientation of the facet joints in degenerative rotatory lumbar scoliosis

Orientation of the facet joints in degenerative rotatory lumbar scoliosis- an MR study on 52 patients

Acta Neurochir (2016) 158:473–479

Because of a degenerative component, degenerative rotatory scoliosis seems different from congenital and idiopathic subtypes of the disease. This study aims to examine the orientation of facet joints, as a known cause of degeneration, in patients with degenerative rotatory scoliosis.

Methods Lumbar magnetic resonance (MR) images and plain radiographs of 52 symptomatic patients (mean age, 50.17 years) with degenerative rotatory lumbar scoliosis (mean curve, 19.22 degrees) and 50 healthy individuals were reviewed. Facet joint angles in rotated segments and the minimum neural foramen width at all lumbar levels were measured by three observers and the average was recorded.

Results The maximum vertebral rotation was most frequent at L4-L5 (75 %), and the majority was of type I (84.6 %) according to the Nash-Moe classification. At all lumbar spinal levels the mean facet joint angles were significantly higher on the side of rotation (L2-L3, 57.92 degrees; L3-L4, 45.00 degrees; L4-L5, 43.88 degrees) compared to those on the contralateral side (L2-L3, 20.42 degrees; L3-L4, 15.48 degrees; L4-L5, 13.12 degrees) and in controls (L2-L3, 30.21 degrees; L3- L4, 40.81 degrees; L4-L5, 45.20 degrees) (p<0.001 for all comparisons). The mean facet joint angle increased significantly from L4-L5 to L2-L3 in cases and reversely in controls. The mean minimum neural foramen width was 1.29 ± 0.85 mm on the side of rotation, 5.50 ± 1.09 mm on the contralateral side, and 6.78± 1.75 mm in controls (p<0.001).

Conclusions Substantial asymmetries and abnormal orientations in facet joints were documented in patients with degenerative rotatory lumbar scoliosis. Such asymmetries may adversely affect neural foramen width.

Identification of cranial nerves around trigeminal schwannomas using diffusion tensor tractography

Identification of cranial nerves around trigeminal schwannomas using diffusion tensor tractography

Acta Neurochir (2016) 158:429–435

There are no large series studies identifying the locations of cranial nerves (CNs) around trigeminal schwannomas (TSs); however, surgically induced cranial neuropathies are commonly observed after surgeries to remove TSs. In this study, we preoperatively identified the location of CNs near TSs using diffusion tensor tractography (DTT).

Methods An observational study of the DTT results and intraoperative findings was performed. We preoperatively completed tractography from images of patients with TSs who received surgical therapy. The result was later validated during tumorectomy.

Results A total of three consecutive patients were involved in this study. The locations of CNs V-VIII in relation to the tumor was clearly revealed in all cases, except for CN VI in case 3.The predicted fiber tracts were in agreement with intraoperative observations.

Conclusions In this study, preoperative DTT accurately predicted the location of the majority of the nerves of interest. This technique can be applied by surgeons to preoperatively visualize nerve arrangements.

Suprasellar Arachnoid Cysts: Toward a New Simple Classification Based on Prognosis and Treatment Modality

Suprasellar Arachnoid Cysts- Toward a New Simple Classification Based on Prognosis and Treatment Modality

Neurosurgery 78:370–380, 2016

Suprasellar arachnoid cysts (SAC) represent between 9% and 21% of pediatric arachnoid cysts. Recent improvements in magnetic resonance imaging, as well as increasing prenatal diagnosis, have allowed more precise knowledge and follow-up.

OBJECTIVE: To describe a novel classification of SAC.

METHODS: We present 35 cases of SAC treated between 1996 and 2014. Patient records and imaging studies were reviewed retrospectively to assess symptomatology, radiological findings, treatment, and long-term follow-up.

RESULTS: Fourteen SAC were diagnosed prenatally (39%). We observed 15 (43%) cases presenting hydrocephalus (SAC-1) removing Liliequist membrane downward. Lower forms (SAC-2) with free third ventricle were observed in 11 (31%) cases. Asymmetrical forms (SAC-3) with Sylvian or temporal extension were seen in the 9 (26%) remaining patients. Twenty-three (66%) patients were treated by ventriculocisternostomy, 3 (8.5%) by shunt surgery, and 3 (8.5%) by craniotomy. Six (17%) patients had no surgery, including 5 cases (14%) that had prenatal diagnosis. Outcomes were initially favorable in 26 cases (87%). Eight (22%) patients had endocrine abnormalities at the end of the follow-up, 3 (8.5%) had developmental delay, and 6 (17%) had minor neuropsychological disturbances.

CONCLUSION: SAC are heterogeneous entities. SAC-1 may come from an expansion of the diencephalic leaf of the Liliequist membrane. SAC-2 show a dilatation of the interpeduncular cistern and correspond to a defect of the mesencephalic leaf of the Liliequist membrane. SAC-3 correspond to the asymmetrical forms expanding to other subarachnoid spaces. Surgical treatment is not always necessary. The recognition of the different subtypes will allow choosing the best treatment option.

Delayed contrast-enhanced MRI for brain metastases

Delayed contrast-enhanced MRI for brain metastases

J Neurosurg 124:489–495, 2016

Contrast-enhanced MRI is the preeminent diagnostic test for brain metastasis (BM). Detection of BMs for stereotactic radiosurgery (SRS) planning may improve with a time delay following administration of a high-relaxivity agent for 1.5-T and 3-T imaging systems. Metastasis detection with time-delayed MRI was evaluated in this study.

Methods Fifty-three volumetric MRI studies from 38 patients undergoing SRS for BMs were evaluated. All studies used 0.1-mmol/kg gadobenate dimeglumine (MultiHance; Bracco Diagnostics) immediately after injection, followed by 2 more axial T1-weighted sequences after 5-minute intervals (final image acquisition commenced 15 minutes after contrast injection). Two studies were motion limited and excluded. Two hundred eighty-seven BMs were identified. The studies were randomized and examined separately by 3 radiologists, who were blinded to the temporal sequence. Each radiologist recorded the number of BMs detected per scan. A Wilcoxon signed-rank test compared BM numbers between scans. One radiologist determined the scan on which BMs were best defined. All confirmed, visible tumors were contoured using iPlan RT treatment planning software on each of the 3 MRI data sets. A linear mixed model was used to analyze volume changes.

Results The interclass correlations for Scans 1, 2, and 3 were 0.7392, 0.7951, and 0.7290, respectively, demonstrating excellent interrater reliability. At least 1 new lesion was detected in the second scan as compared with the first in 35.3% of subjects (95% CI 22.4%–49.9%). The increase in BM numbers between Scans 1 and 2 ranged from 1 to 10. At least 1 new lesion was detected in the third scan as compared with the second in 21.6% of subjects (95% CI 11.3%–35.3%). The increase in BM numbers between Scans 2 and 3 ranged from 1 to 9. Between Scans 1 and 3, additional tumors were seen on 43.1% of scans (increase ranged from 1 to 14). The median increase in tumor number for all comparisons was 1. There was a significant increase in number of BMs detected from Scan 1 to Scan 2 (p < 0.0367) and from Scan 1 to Scan 3 (p < 0.0264). In 34 of the 51 subjects (66.7%), the radiologist selected the third scan as the one providing the clearest tumor definition. There was an average 25.4% increase in BM volume between Scans 1 and 2 (p < 0.0001) and a 9% increase in BM volume between Scans 2 and 3 (p = 0.0001).

Conclusions In patients who are being prepared for SRS of BMs, delayed MRI after contrast injection revealed more targets that needed treatment. In addition, apparent treatment volumes increased with a time delay. To avoid missing tumors that could be treated at the time of planned SRS and resultant “treatment failures,” the authors recommend that postcontrast MR images be acquired between 10 and 15 minutes after injection in patients undergoing SRS for treatment of BMs.

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


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