Category: MRI

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Higher-Resolution Magnetic Resonance Elastography in Meningiomas to Determine Intratumoral Consistency

Higher-Resolution Magnetic Resonance Elastography in Meningiomas to Determine Intratumoral Consistency

Neurosurgery 77:653–659, 2015

Magnetic resonance elastography (MRE) analyzes shear wave movement through tissue to determine stiffness. In a prior study, measurements with firstgeneration brain MRE techniques correlated with intraoperative observations of overall meningioma stiffness.

OBJECTIVE: To evaluate the diagnostic accuracy of a higher-resolution MRE technique to preoperatively detect intratumoral variations compared with surgeon assessment.

METHODS: Fifteen meningiomas in 14 patients underwent MRE. Tumors with regions of distinctly different stiffness were considered heterogeneous. Intratumoral portions were considered hard if there was a significant area ≥6 kPa. A 5-point scale graded intraoperative consistency. A durometer semiquantitatively measured surgical specimen hardness. Statistics included x2, sensitivity, specificity, positive and negative predicative values, and Spearman rank correlation coefficient.

RESULTS: For MRE and surgery, 9 (60%) and 7 (47%) tumors were homogeneous, 6 (40%) and 8 (53%) tumors were heterogeneous, 6 (40%) and 10 (67%) tumors had hard portions, and 14 (93%) and 12 (80%) tumors had soft portions, respectively. MRE sensitivity, specificity, and positive and negative predictive values were as follows: for heterogeneity, 75%, 100%, 100%, and 87%; for hardness, 60%, 100%, 100%, and 56%; and for softness, 100%, 33%, 86%, and 100%. Overall, 10 tumors (67%) matched well with MRE and intraoperative consistency and correlated between intraoperative observations (P = .02) and durometer readings (P = .03). Tumor size ≤3.5 cm or vascular tumors were more likely to be inconsistent (P < .05).

CONCLUSION: MRE was excellent at ruling in heterogeneity with hard portions but less effective in ruling out heterogeneity and hard portions, particularly in tumors more vascular or ≤3.5 cm. MRE is the first technology capable of prospectively evaluating intratumoral stiffness and, with further refinement, will likely prove useful in preoperative planning.

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Can Preoperative Imaging Predict Tumor Involvement of the Anterior Clinoid in Clinoid Region Meningiomas?

Can Preoperative Imaging Predict Tumor Involvement of the Anterior Clinoid in Clinoid Region Meningiomas?

Neurosurgery 77:525–530, 2015

Anterior clinoid region meningiomas may infiltrate the bone over which they arise, therefore requiring an anterior clinoidectomy to achieve a Simpson grade 1 resection. A clinoidectomy, however, is not without risks.

OBJECTIVE: We performed a study of diagnostic accuracy investigating whether preoperative imaging could predict tumor involvement of the clinoid, and thereby tailor the degree of bony removal.

METHODS: Patients having undergone resection of a clinoid region meningioma between 2001 and 2011 were identified. Included in further analysis were those patients in whom a clinoidectomy was performed with subsequent pathologically confirmed presence or absence of tumor in the clinoid process on decalcified specimens. Two neuroradiologists, blinded to pathology results, independently reviewed available preoperative imaging and stated whether or not they anticipated the clinoid to be involved by tumor. Interobserver agreement and the ability to accurately predict tumor involvement of the clinoid were then analyzed.

RESULTS: Sixty-two patients were included in the final analysis. Interobserver agreement was 100%. Sensitivity and specificity of preoperative imaging to predict tumor involvement was 89% and 52%, respectively, with positive and negative likelihood ratios of 1.85 and 0.20. Positive and negative predictive values were 73% and 76%, respectively.

CONCLUSION: Preoperative imaging of clinoid region meningiomas can accurately predict the presence or absence of tumor involvement of the clinoid in only approximately 75% of cases. In light of the fact that a quarter of patients with radiographically negative clinoids will have tumor present on pathological analysis, we recommend a clinoidectomy for all clinoid region meningiomas.

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What You See Is What You Get: Lead Location Within Deep Brain Structures Is Accurately Depicted by Stereotactic Magnetic Resonance Imaging

What You See Is What You Get- Lead Location Within Deep Brain Structures Is Accurately Depicted by Stereotactic Magnetic Resonance Imaging

Operative Neurosurgery 11:412–419, 2015

Magnetic resonance imaging (MRI)-verified deep brain stimulation relies on the correct interpretation of stereotactic imaging documenting lead location in relation to visible anatomic target. However, it has been suggested that local signal distortion from the lead itself renders its depiction on MRI unreliable.

OBJECTIVE: To compare lead location on stereotactic MRI with subsequent location of its brain track after removal.

METHODS: Patients underwent deep brain stimulation with the use of MRI-guided and MRI-verified Leksell frame approach. Infection or suboptimal efficacy required lead removal and subsequent reimplantation by using the same technique. Postimplantation stereotactic MR images were analyzed. Lateral (x) and anteroposterior (y) distances from midcommissural point to center of the lead hypointensity were recorded at the anterior commissure-posterior commissure plane (pallidal electrode) or z = 24 (subthalamic electrode). Stereotactic MRI before the second procedure, x and y distances from the center of the visible lead track hypointensity to midcommissural point were independently recorded. Vectorial distance from center of the lead hypointensity to the center of its track was calculated.

RESULTS: Sixteen electrode tracks were studied in 10 patients. Mean differences between lead artifact location and lead track location were: x coordinate 0.4 mm 6 0.2; y coordinate 0.6 mm 6 0.3. Mean vectorial distance was 0.7 mm 6 0.2.

CONCLUSION: Stereotactic distance between lead location and subsequent brain track location on MRI was small. The mean discrepancy was approximately half the deep brain stimulation lead width. This suggests that lead hypointensity seen on postimplantation MRI is indeed an accurate representation of its real location within deep brain structures.

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Retrospective Analysis of Interobserver Spatial Variability in the Localization of Broca’s and Wernicke’s Areas Using Three Different fMRI Language Paradigms

Brocas'area

J Neuroimaging 2015;25:626-633

To determine interobserver spatial variability in language area localization using three commonly employed language tasks.

MATERIALS AND METHODS With institutional review board approval, 125 fMRI time series from 50 different clinical language cases were retrospectively reviewed by three blinded readers who selected 3- dimensional points representing the perceived center of Wernicke’s and Broca’s areas using three language tasks (semantic decision, SD; sentence comprehension, SC; and silent word generation, WG). Point dispersion values were then calculated using the perimeter of the 3-dimensional triangle defined by the three readers’ selections.

RESULTS After resolving interobserver laterality disagreements, there was no difference in spatial variability between the three tasks (P = .069). The SD task had the fewest interobserver laterality disagreements (P = .028) and the SC task had fewer failed localizations for Broca’s area (P = .050) and Wernicke’s area (P = .013).

CONCLUSION While there were no differences between interobserver spatial variability in language area localization between the three tasks, language task choice impacts the accuracy of fMRI language area identification because tasks vary in their rates of interobserver laterality disagreements and failed localizations. A combination of tasks including one with low laterality disagreements (eg, SD) and one with few failed localizations (eg, SC) may offer the best combination.

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Imaging-Based Features of Headaches in Chiari Malformation Type I

Imaging-Based Features of Headaches in Chiari Malformation Type I

Neurosurgery 77:96–103, 2015

Suboccipital cough-induced headaches are considered a hallmark symptom of Chiari malformation type I (CMI). However, non–Valsalva-related suboccipital headaches and headaches in other locations are also common in CMI. The diagnostic significance and the underlying factors associated with these different headaches types are not well understood.

OBJECTIVE: To compare cranial morphology and hydrodynamics in 3 types of headaches in CMI to better understand the pathophysiological basis for the different headache characteristics.

METHODS: Twenty-two cranial physiological and morphological measures were obtained with specialized magnetic resonance imaging scans from 63 symptomatic pretreated CMI patients, 40 with suboccipital headaches induced by Valsalva maneuvers (34 women; age, 36 6 10 years), 15 with non–Valsalva-related suboccipital headaches (10 women; age, 33 6 9 years), 8 with nonsuboccipital non–Valsalva-induced headaches (8 women; age, 39 6 13 years), and 37 control subjects (24 women; age, 36 6 12 years). Group differences were identified with the use of the 2-tailed Student t test. RESULTS: Posterior cranial fossa markers of CMI were similar among the 3 headache subtypes. However, the Valsalva-related suboccipital headaches cohort demonstrated a significantly lower intracranial compliance index than the non–Valsalva-related suboccipital headaches cohort (7.5 6 3.4 vs 10.9 6 4.9), lower intracranial volume change during the cardiac cycle (0.48 6 0.19 vs 0.61 6 0.16 mL), and higher magnetic resonance imaging–derived intracranial pressure (11.1 6 4.3 vs 7.7 6 2.8 mm Hg; P = .02). The Valsalva-related suboccipital headaches cohort had smaller intracranial and lateral ventricular volumes compared with the healthy cohort. The non–Valsalva-related suboccipital headaches cohort had reduced venous drainage through the jugular veins.

CONCLUSION: Valsalva-induced worsening of occipital headaches appears to be related to a small intracranial volume rather than the smaller posterior cranial fossa. This explains the reduced intracranial compliance and corresponding higher pressure measured in CMI patients with headaches affected by Valsalva maneuvers.

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Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

 

J Neurosurg 123:212–225, 2015

Repetitive navigated transcranial magnetic stimulation (rTMS) is now increasingly used for preoperative language mapping in patients with lesions in language-related areas of the brain. Yet its correlation with intraoperative direct cortical stimulation (DCS) has to be improved. To increase rTMS’s specificity and positive predictive value, the authors aim to provide thresholds for rTMS’s positive language areas. Moreover, they propose a protocol for combining rTMS with functional MRI (fMRI) to combine the strength of both methods.

Methods The authors performed multimodal language mapping in 35 patients with left-sided perisylvian lesions by using rTMS, fMRI, and DCS. The rTMS mappings were conducted with a picture-to-trigger interval (PTI, time between stimulus presentation and stimulation onset) of either 0 or 300 msec. The error rates (ERs; that is, the number of errors per number of stimulations) were calculated for each region of the cortical parcellation system (CPS). Subsequently, the rTMS mappings were analyzed through different error rate thresholds (ERT; that is, the ER at which a CPS region was defined as language positive in terms of rTMS), and the 2-out-of-3 rule (a stimulation site was defined as language positive in terms of rTMS if at least 2 out of 3 stimulations caused an error). As a second step, the authors combined the results of fMRI and rTMS in a predefined protocol of combined noninvasive mapping. To validate this noninvasive protocol, they correlated its results to DCS during awake surgery.

Results The analysis by different rTMS ERTs obtained the highest correlation regarding sensitivity and a low rate of false positives for the ERTs of 15%, 20%, 25%, and the 2-out-of-3 rule. However, when comparing the combined fMRI and rTMS results with DCS, the authors observed an overall specificity of 83%, a positive predictive value of 51%, a sensitivity of 98%, and a negative predictive value of 95%.

Conclusions In comparison with fMRI, rTMS is a more sensitive but less specific tool for preoperative language mapping than DCS. Moreover, rTMS is most reliable when using ERTs of 15%, 20%, 25%, or the 2-out-of-3 rule and a PTI of 0 msec. Furthermore, the combination of fMRI and rTMS leads to a higher correlation to DCS than both techniques alone, and the presented protocols for combined noninvasive language mapping might play a supportive role in the language-mapping assessment prior to the gold-standard intraoperative DCS.

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Combination of Intraoperative Magnetic Resonance Imaging and Intraoperative Fluorescence to Enhance the Resection of Contrast Enhancing Gliomas

Combination of Intraoperative Magnetic Resonance Imaging and Intraoperative Fluorescence to Enhance the Resection of Contrast Enhancing Gliomaspdf

Neurosurgery 77:16–22, 2015

Evidence suggests that extent of resection (EOR) is a prognostic factor for patients harboring gliomas. Recent studies have displayed the importance of intraoperative magnetic resonance imaging (iMRI) with 5-aminolevulinic acid (5-ALA) fluorescence-guidance in order to maximize EOR.

OBJECTIVE: To compare iMRI and 5-ALA fluorescence-guidance and the impact on patient survival.

METHODS: Thirty-two patients with contrast-enhancing gliomas undergoing intended gross total resection (GTR) were included in a prospective study. Surgeries were started under white-light conditions. When GTR was thought to be achieved, an iMRI scan was performed and a blue light turned on to search for unintentionally remaining tumor tissue. iMRI findings were compared with intraoperative fluorescence findings. Histological examination of tumor bulk and any additionally resected tissue was performed. All patients underwent early postoperative high-field MRI to determine EOR.

RESULTS: In 13 patients (40.6%), iMRI and fluorescence unequivocally did not show residual tumor intraoperatively. In 19 patients (59.4%), resection was continued due to iMRI or fluorescence findings. In 9 of these (47.4%), iMRI and fluorescence findings were inconsistent regarding residual tumor. GTR according to postoperative MRI was achieved in all but 1 patient. Histological examination ruled out false positive findings in all additionally resected specimens. Sensitivity and specificity to detect residual tumor tissue were 75% and 100%, respectively, for iMRI and 70% and 100% for 5-ALA fluorescence.

CONCLUSION: Use of iMRI as well as fluorescence-guidance are appropriate methods to improve the extent of resection in surgery of contrast-enhancing gliomas. Best results can be achieved by complementary use of both modalities.

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Magnetic resonance spectroscopy detection of high lipid levels in intraaxial tumors without central necrosis: a characteristic of malignant lymphoma

Magnetic resonance spectroscopy detection of high lipid levels in intraaxial tumors without central necrosis- a characteristic of malignant lymphoma
J Neurosurg 122:1370–1379, 2015

The differentiation of malignant lymphomas from gliomas or malignant gliomas by conventional MRI can be difficult. The authors studied Gd-enhanced MR images to obtain a differential diagnosis between malignant lymphomas and gliomas without central necrosis or cystic changes and investigated the diagnostic value of single-voxel proton MR spectroscopy (1H-MRS) using different parameters, including lipid levels.
Methods This was a retrospective study of patients with primary malignant CNS lymphoma (n = 17) and glioma (n = 122 [Grades I, II, III, and IV in 10, 30, 33, and 49 patients, respectively]) who were treated between 2007 and 2013. The authors focused on 15 patients with homogeneously enhanced primary malignant CNS lymphomas and 7 homogeneously enhanced gliomas. Images of all the included tumors were acquired with 1H-MRS at 3 T, and the diagnoses were histologically confirmed.
Results Using a short echo time 1H-MRS, large lipid peaks were observed in all 17 patients with a malignant lymphoma, in 39 patients (79.6%) with a Grade IV glioma, and in 10 patients (30.3%) with a Grade III glioma. A focus on homogeneously enhanced tumors revealed large lipid peaks in 15 malignant lymphomas that were free of central necrosis on Gd-enhanced T1-weighted images. Conversely, in the 7 homogeneously enhanced gliomas (glioblastoma and anaplastic astrocytoma, n = 2 each; anaplastic oligodendroglioma, diffuse astrocytoma, and pilomyxoid astrocytoma, n = 1 each), lipid peaks were small or absent.
Conclusions Large lipid peaks on 1H-MRS images of tumors without central necrosis were characteristic of malignant lymphomas. Conversely, small or absent lipid peaks in intraaxial tumors without central necrosis were strongly suggestive of glioma.

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Intraoperative subcortical mapping of a language-associated deep frontal tract connecting the superior frontal gyrus to Broca’s area in the dominant hemisphere of patients with glioma

Intraoperative subcortical mapping of a language-associated deep frontal tract connecting the superior frontal gyrus to Broca’s area in the dominant hemisphere of patients with glioma

J Neurosurg 122:1390–1396, 2015

The deep frontal pathway connecting the superior frontal gyrus to Broca’s area, recently named the frontal aslant tract (FAT), is assumed to be associated with language functions, especially speech initiation and spontaneity. Injury to the deep frontal lobe is known to cause aphasia that mimics the aphasia caused by damage to the supplementary motor area. Although fiber dissection and tractography have revealed the existence of the tract, little is known about its function. The aim of this study was to determine the function of the FAT via electrical stimulation in patients with glioma who underwent awake surgery.

Methods The authors analyzed the data from subcortical mapping with electrical stimulation in 5 consecutive cases (3 males and 2 females, age range 40–54 years) with gliomas in the left frontal lobe. Diffusion tensor imaging (DTI) and tractography of the FAT were performed in all cases. A navigation system and intraoperative MRI were used in all cases. During the awake phase of the surgery, cortical mapping was performed to find the precentral gyrus and Broca’s area, followed by tumor resection. After the cortical layer was removed, subcortical mapping was performed to assess language-associated fibers in the white matter.

Results In all 5 cases, positive responses were obtained at the stimulation sites in the subcortical area adjacent to the FAT, which was visualized by the navigation system. Speech arrest was observed in 4 cases, and remarkably slow speech and conversation was observed in 1 case. The location of these sites was also determined on intraoperative MR images and estimated on preoperative MR images with DTI tractography, confirming the spatial relationships among the stimulation sites and white matter tracts. Tumor removal was successfully performed without damage to this tract, and language function did not deteriorate in any of the cases postoperatively.

Conclusions The authors identified the left FAT and confirmed that it was associated with language functions. This tract should be recognized by clinicians to preserve language function during brain tumor surgery, especially for tumors located in the deep frontal lobe on the language-dominant side.

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Assessment of ETV patency with the 3D-SPACE technique

Assessment of third ventriculostomy patency with the 3D-SPACE technique

J Neurosurg 122:1347–1355, 2015

The goal of this study was to determine the value of the 3D sampling perfection with application-optimized contrasts using different flip-angle evolutions (3D-SPACE) technique in the evaluation of endoscopic third ventriculostomy (ETV) patency.

Methods Twenty-six patients with ETV were examined using 3-T MRI units. Sagittal-plane 3D-SPACE with variant flip-angle mode, 3D T1-weighted (T1W), and 3D heavily T2-weighted (T2W) images were obtained with isotropic voxel sizes. Also, sagittal-axial plane phase-contrast cine (PC)-MR images were obtained. The following findings were evaluated: diameters of stoma and third ventricle, flow-void sign on 3D-SPACE and PC-MR images, integrity of the third ventricle on heavily T2W images, and quantitative PC-MRI parameters of the stoma. Obtained sequences were evaluated singly, in combination with one another, and all together.

Results The mean area, flow, and velocity values measured at the level of stoma in patients with patent stoma were significantly higher than those measured in patients with closed stoma (p < 0.05). There was significant correlation among PC-MRI, 3D-SPACE, and 3D heavily T2W techniques regarding assessment of ETV patency (p < 0.001). The 3D-SPACE technique provided the lowest rate of ambiguous results.

Conclusions The 3D-SPACE technique seems to be the most efficient one for determination of ETV patency. The authors suggest the use of 3D-SPACE as a stand-alone first-line sequence in addition to routine brain MRI protocols in assessing patients with ETV, thereby decreasing scan time and reserving the use of a combination of additional sequences such as PC-MRI and 3D heavily T2W images in suspicious or complex cases.

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Comparison of language cortex reorganization patterns between cerebral arteriovenous malformations and gliomas: a functional MRI study

Comparison of language cortex reorganization patterns between cerebral arteriovenous malformations and gliomas- a functional MRI study

J Neurosurg 122:996–1003, 2015

Cerebral arteriovenous malformations (AVMs) are congenital malformations that may grow in the language cortex but usually do not lead to aphasia. In contrast, language dysfunction is a common presentation for patients with a glioma that involves language areas. The authors attempted to demonstrate the difference in patterns of language cortex reorganization between cerebral AVMs and gliomas by blood oxygen level–dependent (BOLD) functional MRI (fMRI) evaluation.

Methods The authors retrospectively reviewed clinical and imaging data of 63 patients with an unruptured cerebral AVM (AVM group) and 38 patients with a glioma (glioma group) who underwent fMRI. All the patients were right handed, and all their lesions were located in the left cerebral hemisphere. Patients were further categorized into 1 of the 2 following subgroups according to their lesion location: the BA subgroup (overlying or adjacent to the inferior frontal or the middle frontal gyri [the Broca area]) and the WA subgroup (overlying or adjacent to the supramarginal, angular, or superior temporal gyri [the Wernicke area]). Lateralization indices of BOLD signal activations were calculated separately for the Broca and Wernicke areas. Statistical analysis was performed to identify the difference in patterns of language cortex reorganization between the 2 groups.

Results In the AVM group, right-sided lateralization of BOLD signal activations was observed in 23 patients (36.5%), including 6 with right-sided lateralization in the Broca area alone, 12 in the Wernicke area alone, and 5 in both areas. More specifically, in the 34 patients in the AVM-BA subgroup, right-sided lateralization of the Broca area was detected in 9 patients (26.5%), and right-sided lateralization of the Wernicke area was detected in 4 (11.8%); in the 29 patients in the AVM-WA subgroup, 2 (6.9%) had right-sided lateralization of the Broca area, and 13 (44.8%) had right-sided lateralization of the Wernicke area. In the glioma group, 6 patients (15.8%) showed right-sided lateralization of the Wernicke area, including 2 patients in the glioma-BA subgroup and 4 patients in the glioma-WA subgroup. No patient showed right-sided lateralization of the Broca area. Moreover, although the incidence of right-sided lateralization was higher in cases of low-grade gliomas (5 in 26 [19.2%]) than in high-grade gliomas (1 in 12 [8.3%]), no significant difference was detected between them (p = 0.643). Compared with the AVM group, the incidence of aphasia was significantly higher (p < 0.001), and right-sided lateralization of language areas was significantly rarer (p = 0.026) in the glioma group.

Conclusions Right-sided lateralization of BOLD signal activations was observed in patients with a cerebral AVM and in those with a glioma, suggesting that language cortex reorganization may occur with both diseases. However, the potential of reorganization in patients with gliomas seems to be insufficient compared with patients AVMs, which is suggested by clinical manifestations and the fMRI findings. Moreover, this study seems to indicate that in patients with an AVM, a nidus near the Broca area mainly leads to right-sided lateralization of the Broca area, and a nidus near the Wernicke area mainly leads to right-sided lateralization of the Wernicke area.

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Evaluation of spinal cord compression and hyperintense intramedullary lesions on T2-weighted sequences in patients with cervical spondylotic myelopathy using flexion-extension MRI protocol

Evaluation of spinal cord compression and hyperintense intramedullary lesions on T2-weighted sequences in patients with cervical spondylotic myelopathy using flexion-extension MRI protocol

The Spine Journal 15 (2015) 668–674

Acquired cervical stenosis is caused by the combination of disc protrusion, facet joint degeneration, hypertrophy of the ligamentum flavum, and osteophyte formation. Although these mechanical factors seem to play an important role in the pathogenesis of myelopathy, the role of dynamic factors has been suggested by many authors. Based on these results, dynamic magnetic resonance imaging (MRI) was proposed to improve diagnostic techniques in patients with cervical myelopathy.

PURPOSE: The purpose of the study was to evaluate the importance of dynamic MRI in the assessment of cervical canal stenosis and to determine the percentage of levels in which cord impingement was only visible in the extension MRI and the percentage of cases in which hyperintense intramedullary lesions (HILs) were identified only on the flexion MRI.

STUDY DESIGN: This is a retrospective case series study.

PATIENT SAMPLE: Patients with spondylotic myelopathy who had dynamic cervical MRI at our department from October 2005 to February 2007 were included.

MATERIALS AND METHODS: Fifty-one consecutive patients with spondylotic myelopathy had MRI in the neutral, flexion, and extension positions of the cervical spine.

OUTCOME MEASURES: The following entities were evaluated: canal stenosis (the evaluation of the stenosis was based on the Muhle classification) and the presence or absence of HILs.

RESULTS: Two hundred fifty-five levels were evaluated in the three positions. At each level, the stages in extension were higher than the stages in neutral and flexion positions (p<.05). From C3 to C6, around 22.5% of Stage 3 levels in the extension were Stage 1 in the neutral position. In flexion, HILs are better identified than in neutral and extension positions (p<.05). In 10% of the patients, HILs were identified only in the flexion T2-weighted sequence.

CONCLUSIONS: Extension MRI helps to identify significant cervical canal stenosis that is partially or completely absent on neutral and flexion MRI and to determine the exact number of levels to decompress surgically. Flexion MRI permits better visualization of HILs on T2-weighted sequences.

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Frameless Stereotactic Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy to Perform Bilateral Anterior Cingulotomy for Intractable Pain

Frameless Stereotactic Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy to Perform Bilateral Anterior Cingulotomy for Intractable Pain

Operative Neurosurgery 11:17–25, 2015

Bilateral anterior cingulotomy is well described for certain pain and psychiatric disorders. Typically, stereotactic frame-based radiofrequency ablation is used. We report the feasibility of a frameless approach using magnetic resonance imaging-guided laser induced thermal therapy (MRgLITT).

OBJECTIVE: To report experience and outcomes for MRgLITT in bilateral anterior cingulotomy.

METHODS: Three patients with chronic refractory cancer-related pain underwent bilateral anterior cingulotomy. The Brief Pain Inventory (Short Form) was used for pain evaluation. Frameless stereotaxy using the Medtronic S7 Navigation system was used for laser catheter placement. Patients were followed for evaluation of pain control outcomes.

RESULTS: Four MRgLITT bilateral cingulotomy procedures were performed in 3 patients. Two patients had a single MRgLITT procedure while the third had repeat ablation after pain recurrence. First time ablation coordinates were (medians): x = 7.9 mm (range, 6.9-8.6); y = 20.5 mm(range, 20-22); z = 6.9 mm(range, 2.9-7.0) above the lateral ventricle roof. Median trajectory length was 85.5 mm (range, 80-90). Median ablation volume was 1.5 cm3 (range, 0.6-1.2). Median ablation time was 257 seconds (range, 136-338) per cingulum and power was 10.0 Watts (range, 10-11). Median preoperative pain severity (PSS) and interference scores (PIS) were 7.7 (range, 7.5-9.3) and 9.9 (range, 9.7-10.0), respectively. Median postoperative PSS and PIS scores were 1.6 (range, 1.0-2.8) and 2.0 (range, 0.3-2.6), respectively.

CONCLUSION: MRgLITT cingulotomy is well tolerated for treatment of cancer pain and can be easily performed framelessly for appropriate candidates.

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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.

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Mapping p53 Mutations in Low-Grade Glioma: A Voxel-Based Neuroimaging Analysis

Mapping p53 Mutations in Low-Grade Glioma

AJNR Am J Neuroradiol 36:70–76

Brain tumor location has proved to be a prognostic factor that may be associated with features of neoplastic origin. Mutation of p53 is an atypical genetic change that occurs during tumorigenesis. Thus, a potential correlation may exist between tumor location and p53 status. The purpose of the current study was to identify anatomic characteristics of mutant p53 expression by using quantitative neuroimaging analyses.

MATERIALS AND METHODS: Preoperative MR images from 182 patients with histologically confirmed low-grade gliomas were retrospectively analyzed. All tumors were manually marked and registered to the standard space. Using a voxel-based lesion-symptom mapping analysis, we located brain regions associated with a high occurrence of p53 mutation and corrected them by using a permutation test. The acquired clusters were further included as a factor in survival analyses.

RESULTS: Statistical analysis demonstrated that the left medial temporal lobe and right anterior temporal lobe were specifically associated with high expression of mutant p53. Kaplan-Meier curves showed that tumors located in these regions were associated with significantly worse progression-free survival compared with tumors occurring elsewhere.

CONCLUSIONS: Our voxel-level imaging analysis provides new evidence that genetic changes during cancer may have anatomic specificity. Additionally, the current study suggests that tumor location identified on structural MR images could potentially be used for customized presurgical outcome prediction.

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Localizing hand motor area using resting-state fMRI

Localizing hand motor area using resting-state fMRI

Acta Neurochir (2014) 156:2295–2302

Resting-state functional magnetic resonance imaging (R-fMRI) is a promising tool in clinical application, especially in presurgicalmapping for neurosurgery. This study aimed to investigate the sensitivity and specificity of R-fMRI in the localization of hand motor area in patients with brain tumors validated by direct cortical stimulation (DCS).We also compared this technique to task-based blood oxygenation level-dependent (BOLD) fMRI (T-fMRI).

Methods R-fMRI and T-fMRI were acquired from 17 patients with brain tumors. The cortex sites of the hand motor area were recorded by DCS. Site-by-site comparisons between R-fMRI/TfMRI andDCS were performed to calculate R-fMRI and T-fMRI sensitivity and specificity using DCS as a “gold standard”. RfMRI and T-fMRI performances were compared statistically

Results A total of 609 cortex sites were tested with DCS and compared with R-fMRI findings in 17 patients. For hand motor area localization, R-fMRI sensitivity and specificity were 90.91 and 89.41%, respectively. Given that two subjects could not comply with T-fMRI, 520 DCS sites were compared with T-fMRI findings in 15 patients. The sensitivity and specificity of T-fMRI were 78.57 and 84.76 %, respectively. In the 15 patients who successfully underwent both R-fMRI and T-fMRI, there was no statistical difference in sensitivity or specificity between the two methods (p=0.3198 and p= 0.1431, respectively)

Conclusions R-fMRI sensitivity and specificity are high for localizing hand motor area and even equivalent or slightly higher compared with T-fMRI. Given its convenience for patients, R-fMRI is a promising substitute for T-fMRI for pre surgical mapping.

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Navigated Transcranial Magnetic Stimulation for “Somatotopic” Tractography of the Corticospinal Tract

SOMATOTOPIC RECONSTRUCTION OF CORTICOSPINAL TRACT

Operative Neurosurgery 10:542–554, 2014

Diffusion tensor imaging tractography provides 3-dimensional reconstruction of principal white matter tracts, but its spatial accuracy has been questioned. Navigated transcranial magnetic stimulation (nTMS) enables somatotopic mapping of the motor cortex.

OBJECTIVE: We used motor maps to reconstruct the corticospinal tract (CST) by integrating elements of its somatotopic organization. We analyzed the accuracy of this method compared with a standard technique and verified its reliability with intraoperative subcortical stimulation.

METHODS: We prospectively collected data from patients who underwent surgery between January 2012 and October 2013 for lesions involving the CST. nTMS-based diffusion tensor imaging tractography was compared with a standard technique. The reliability and accuracy between the 2 techniques were analyzed by comparing the number of fibers, the concordance in size, and the location of the cortical end of the CST and the motor area. The accuracy of the technique was assessed by using direct subcortical stimulation.

RESULTS: Twenty patients were enrolled in the study. nTMS-based tractography provided a detailed somatotopic reconstruction of the CST. This nTMS-based reconstruction resulted in a decreased number of fibers (305.16 231.7 vs 10246 193, P , .001) and a significantly greater overlap between the motor cortex and the cortical end-region of the CST compared with the standard technique (90.5 6 8.8% vs 58.3 6 16.6%, P , .001). Direct subcortical stimulation confirmed the CST location and the somatotopic reconstruction in all cases.

CONCLUSION: These results suggest that nTMS-based tractography of the CST is more accurate and less operator dependent than the standard technique and provides a reliable anatomic and functional characterization of the motor pathway.

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Intraoperative high-field MRI for transsphenoidal reoperations of nonfunctioning pituitary adenoma

Intraoperative high-field MRI for transsphenoidal reoperations of nonfunctioning pituitary adenoma

J Neurosurg 121:1166–1175, 2014

The loss of anatomical landmarks, frequently invasive tumor growth, and tissue changes make transsphenoidal reoperation of nonfunctioning pituitary adenomas (NFAs) challenging. The use of intraoperative MRI (iMRI) may lead to improved results. The goal of this retrospective study was to evaluate the impact of iMRI on transsphenoidal reoperations for NFA.

Methods. Between September 2002 and July 2012, 109 patients underwent reoperations in which 111 transsphenoidal procedures were performed and are represented in this study. A 1.5-T Magnetom Sonata Maestro Class scanner (Siemens) was used for iMRI. Follow-up iMRI scans were acquired if gross-total resection (GTR) was suspected or if no further removal seemed possible.

Results. Surgery was performed for tumor persistence and regrowth in 26 (23%) and 85 (77%) patients, respectively. On the initial iMRI scans, GTR was confirmed in 19 (17%) patients. Remnants were located as follows: 65 in the cavernous sinus (71%), 35 in the suprasellar space (38%), 9 in the retrosellar space (10%). Additional resection was possible in 62 (67%) patients, resulting in a significant volume reduction and increased GTR rate (49%). The GTR rates of invasive tumors on initial iMRI and postoperative MRI (poMRI) were 7% and 25%, respectively. Additional remnant resection was possible in 64% of the patients. Noninvasive tumors were shown to be totally resected on the initial iMRI in 31% of cases. After additional resection for 69% of the procedures, the GTR rate on poMRI was 75%. Transcranial surgery to resect tumor remnants was indicated in 5 (5%), and radiotherapy was performed in 29 (27%) patients. After GTR, no recurrence was detected during a mean follow-up of 2.2 ± 2.1 years.

Conclusions. The use of iMRI in transsphenoidal reoperations for NFA leads to significantly higher GTR rates. It thus prevents additional operations and reduces the number of tumor remnants. The complication rates do not exceed the incidences reported in the literature for primary transsphenoidal surgery. If complete tumor resection is not possible, iMRI guidance can facilitate tumor volume reduction.

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Magnetic Resonance Imaging Measures of Posterior Cranial Fossa Morphology and Cerebrospinal Fluid Physiology in Chiari Malformation Type I

Magnetic Resonance Imaging Measures of Posterior Cranial Fossa Morphology and Cerebrospinal Fluid Physiology in Chiari Malformation Type I

Neurosurgery 75:515–522, 2014

It has been well documented that, along with tonsillar herniation, Chiari Malformation Type I (CMI) is associated with smaller posterior cranial fossa (PCF) and altered cerebrospinal fluid (CSF) flow and tissue motion in the craniocervical junction.

OBJECTIVE: This study assesses the relationship between PCF volumetry and CSF and tissue dynamics toward a combined imaging-based morphological-physiological characterization of CMI. Multivariate analysis is used to identify the subset of parameters that best discriminates CMI from a healthy cohort.

METHODS: Eleven length and volumetric measures of PCF, including crowdedness and 4th ventricle volume, 4 measures of CSF and cord motion in the craniocervical junction, and 5 global intracranial measures, including intracranial compliance and pressure, were measured by magnetic resonance imaging (MRI) in 36 symptomatic CMI subjects (28 female, 37 6 11 years) and 37 control subjects (24 female, 36 6 12 years). The CMI group was further divided based on symptomatology into “typical” and “atypical” subgroups.

RESULTS: Ten of the 20 morphologic and physiologic measures were significantly different between the CMI and the control cohorts. These parameters also had less variability and stronger significance in the typical CMI compared with the atypical. The measures with the most significance were clival and supraocciput lengths, PCF crowdedness, normalized PCF volume, 4th ventricle volume, maximal cord displacement (P , .001), and MR measure of intracranial pressure (P = .007). Multivariate testing identified cord displacement, PCF crowdedness, and normalized PCF as the strongest discriminator subset between CMI and controls. MR measure of intracranial pressure was higher in the typical CMI cohort compared with the atypical.

CONCLUSION: The identified 10 complementing morphological and physiological measures provide a more complete and symptomatology-relevant characterization of CMI than tonsillar herniation alone.

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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.

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