Postoperative Diffusion Tensor Imaging Research Articles

Diffusion MRI Metrics Characterize Postoperative Clinical Outcomes After Surgery for Cervical Spondylotic Myelopathy.

Advanced diffusion-weighted MRI (DWI) modeling, such as diffusion tensor imaging (DTI) and diffusion basis spectrum imaging (DBSI), may help guide rehabilitation strategies after surgical decompression for cervical spondylotic myelopathy (CSM). Currently, however, postoperative DWI is difficult to interpret, owing to signal distortions from spinal instrumentation. Therefore, we examined the relationship between postoperative DTI/DBSI-extracted from the rostral C3 spinal level-and clinical outcome measures at 2-year follow-up after decompressive surgery for CSM. Fifty patients with CSM underwent complete clinical and DWI evaluation-followed by DTI/DBSI analysis-at baseline and 2-year follow-up. Clinical outcomes included the modified Japanese Orthopedic Association score and comprehensive patient-reported outcomes. DTI metrics included apparent diffusion coefficient, fractional anisotropy, axial diffusivity, and radial diffusivity. DBSI metrics evaluated white matter tracts through fractional anisotropy, fiber fraction, axial diffusivity, and radial diffusivity as well as extra-axonal pathology through restricted and nonrestricted fraction. Cross-sectional Spearman's correlations were used to compare postoperative DTI/DBSI metrics with clinical outcomes. Twenty-seven patients with CSM, including 15, 7, and 5 with mild, moderate, and severe disease, respectively, possessed complete baseline and postoperative DWI scans. At 2-year follow-up, there were 10 significant correlations among postoperative DBSI metrics and postoperative clinical outcomes compared with 3 among postoperative DTI metrics. Of the 13 significant correlations, 7 involved the neck disability index (NDI). The strongest relationships were between DBSI axial diffusivity and NDI (r = 0.60, P < .001), DBSI fiber fraction and NDI (rs = -0.58, P < .001), and DBSI restricted fraction and NDI (rs = 0.56, P < .001). The weakest correlation was between DTI apparent diffusion coefficient and NDI (r = 0.35, P = .02). Quantitative measures of spinal cord microstructure after surgery correlate with postoperative neurofunctional status, quality of life, and pain/disability at 2 years after decompressive surgery for CSM. In particular, DBSI metrics may serve as meaningful biomarkers for postoperative disease severity for patients with CSM.

A diffusion tensor imaging comparison of white matter development in nonsyndromic craniosynostosis to neurotypical infants.

Nonsyndromic craniosynostosis (NSC) is associated with neurocognitive deficits, and intervention at infancy is standard of care to limit the negative effects of NSC on brain development. In this study, diffusion tensor imaging (DTI) was implemented to investigate white matter microstructure in infants with NSC undergoing cranial vault remodeling, and a comparison was made with white matter development in neurotypical controls. Infants presenting with NSC (n = 12) underwent DTI scans before and after cranial vault remodeling. Neurotypical infants (n = 5), age matched to NSC patients at preoperative scans, were compared to preoperative DTI scans. Pre- and postoperative NSC scans were compared in aggregate, and the sagittal synostosis (n = 8) patients were evaluated separately. Finally, neurotypical infants from the University of North Carolina/University of New Mexico Baby Connectome Project (BCP), who underwent DTI scans at timepoints matching the NSC pre- and postoperative DTI scans, were analyzed (n = 9). Trends over the same time period were compared between NSC and BCP scans. No significant differences were found between preoperative NSC scans and controls. White matter development was more limited in NSC patients than in BCP patients, with microstructural parameters of the corpus body and genu and inferior and superior longitudinal fasciculi consistently lagging behind developmental changes observed in healthy patients. Infant white matter development appears more limited in NSC patients undergoing cranial vault remodeling relative to that in neurotypical controls. Further investigation is needed to explore these differences and the specific effects of early surgical intervention.

Metal artifact reduction around cervical spine implant using diffusion tensor imaging at 3T: A phantom study

PurposeDiffusion MRI continues to play a key role in non-invasively assessing spinal cord integrity and pre-operative injury evaluation. However, post-operative Diffusion Tensor Imaging (DTI) acquisition of patients with metal implants results in severe geometric distortion. We propose and demonstrate a method to alleviate the technical challenges facing the acquisition of DTI on post-operative cases and longitudinal evaluation of therapeutics. Material and methodsThe described technique is based on the combination of the reduced Field-Of-View (rFOV) strategy and the phase segmented EPI, termed rFOV-PS-EPI. A custom-built phantom based on a cervical spine model with metal implants was used to collect DTI data at 3 Tesla scanner using: rFOV-PS-EPI, reduced Field-Of-View single-shot EPI (rFOV-SS-EPI), and conventional full FOV techniques including SS-EPI, PS-EPI, and readout-segmented EPI (RS-EPI). Geometric distortion, SNR, and signal void were assessed to evaluate images and compare the sequences. A two-sample t-test was performed with p-value of 0.05 or less to indicate statistical significance. ResultsThe reduced FOV techniques showed better capability to reduce distortions compared to the Full FOV techniques. The rFOV-PS-EPI method provided DTI images of the phantom at the level of the hardware whereas the conventional rFOV-SS-EPI is useful only when the metal is approximately 20 mm away. In addition, compared to the rFOV-SS-EPI technique, the suggested approach produced smaller signal voids area as well as significantly reduced geometric distortion in Circularity (p < 0.005) and Eccentricity (p < 0.005) measurements. No statistically significant differences were found for these geometric distortion measurements between the rFOV-PS-EPI DTI sequence and conventional structural T2 images (p > 0.05). ConclusionThe combination of rFOV and a phase-segmented acquisition approach is effective for reducing metal-induced distortions in DTI scan on spinal cord with metal hardware at 3 T.

Minimally Invasive Surgery of Deep-Seated Brain Lesions Using Tubular Retractors and Navigated Transcranial Magnetic Stimulation-Based Diffusion Tensor Imaging Tractography Guidance: The Minefield Paradigm.

Surgical treatment of deep-seated brain lesions is a major challenge for neurosurgeons. Recently, tubular retractors have been used to help neurosurgeons in achieving the targeting and resection of deep lesions. To describe a novel surgical approach based on the combination of tubular retractors and preoperative mapping by navigated transcranial magnetic stimulation (nTMS) and nTMS-based diffusion tensor imaging (DTI) tractography for the safe resection of deep-seated lesions. Ten consecutive patients affected by deep-seated brain lesions close to eloquent motor/language/visual pathways underwent preoperative nTMS mapping of motor/language cortical areas and nTMS-based DTI tractography of adjacent eloquent white matter tracts, including optic radiations. The nTMS-based information was used to plan the optimal surgical trajectory and to guide the insertion of tubular retractors within the brain parenchyma without causing injury to the eloquent cortical and subcortical structures. After surgery, all patients underwent a new nTMS-based DTI tractography of fascicles close to the tumor to verify their structural integrity. Gross total resection was achieved in 8 cases, subtotal resection in 1 case, and a biopsy in 1 case. No new postoperative deficits were observed, except in 1 case where a visual field defect due to injury to the optic radiations occurred. Postoperative nTMS-based DTI tractography showed the integrity of the subcortical fascicles crossed by tubular retractors trajectory in 9 cases. The novel strategy combining tubular retractors with functional nTMS-based preoperative mapping enables a safe microsurgical resection of deep-seated lesions through the preservation of eloquent cortical areas and subcortical fascicles, thus reducing the risk of new permanent deficits.

Validation of Presurgical Simulation of White Matter Damage Using Diffusion Tensor Imaging

The understanding of white matter (WM) was revolutionized by the emergence of tractography based on diffusion tensor imaging (DTI). Currently, DTI simulations are implemented in preoperative planning to optimize surgical approaches. The reliability of these simulations has been questioned and investigated seeking for correlation between neurological performance and anomalies in DTI parameters. However, the ability of preoperative WM simulations to predict a surgical injury has not been thoroughly evaluated. Our objective was to assess the reliability of preoperatively simulated WM injuries for conventional neurosurgical procedures. WM surgical damage was preoperatively simulated by creating a 3-dimensional volume representing the endoscope or the surgical trajectory. This volume was used as an additional region of interest in the fascicle reconstruction to be subtracted from the original fascicle. Simulated, injured fascicles were compared in terms of the number of fibers and volume to those created from postoperative DTI studies. Reliability was assimilated into the correlation between the simulation and the postoperative reconstruction; evaluated using the intraclass correlation coefficient or Lin's Concordance correlation coefficient (CCC), and represented on Bland-Altman plots. The preoperative and postoperative DTI studies of 30 patients undergoing various neurosurgical approaches were processed. The correlation between simulated injuries and postoperative studies was high in terms of fibers (Concordance correlation coefficient= Rho.C=0.989 [95% confidence interval= 0.979-0.995]) and volume (intraclass correlation coefficient=0.95 [95% CI= 0.89-0.97]). Bland-Altman plots demonstrated that the great majority of cases fell within the mean±2 Standard deviations. Presurgical simulation of WM fascicles based on DTI is consistent with postoperative DTI studies. These findings require further validation by neurophysiological and clinical correlation.

Mapping Motor Pathways in Parkinson's Disease Patients with Subthalamic Deep Brain Stimulator: A Diffusion MRI Tractography Study.

IntroductionThis study assessed the safety of postoperative diffusion tensor imaging (DTI) with on-state deep brain stimulation (DBS) and the feasibility of reconstruction of the white matter tracts in the vicinity of the stimulation site of the subthalamic nucleus (STN). The association between the impact of DBS on the nigrostriatal pathway (NSP) and the treatment effect on motor symptoms in Parkinson’s disease (PD) was then evaluated.MethodsThirty-one PD patients implanted with STN-DBS (mean age: 66 years; 25 male) were scanned on a 1.5-T magnetic resonance imaging (MRI) scanner using the DTI sequence with DBS on. Twenty-three of them were scanned a second time with DBS off. The NSP, dentato-rubro-thalamic tract (DRTT), and hyperdirect pathway (HDP) were generated using both deterministic and probabilistic tractography methods. The DBS-on-state and off-state tractography results were validated and compared. Afterward, the relationships between the characteristics of the reconstructed white matter tracts and the clinical assessment of PD symptoms and the DBS effect were further examined.ResultsNo adverse events related to DTI were identified in either the DBS-on-state or off-state. Overall, the NSP was best reconstructed, followed by the DRTT and HDP, using the probabilistic tractography method. The connection probability of the left NSP was significantly lower than that of the right side (p < 0.05), and a negative correlation (r = −0.39, p = 0.042) was identified between the preoperative symptom severity in the medication-on state and the connection probability of the left NSP in the DBS-on-state images. Furthermore, the distance from the estimated left-side volume of tissue activated (VTA) by STN-DBS to the ipsilateral NSP was significantly shorter in the DBS-responsive group compared to the DBS-non-responsive group (p = 0.046).ConclusionsDTI scanning is safe and delineation of white matter pathway is feasible for PD patients implanted with the DBS device. Postoperative DTI is a useful technique to strengthen our current understanding of the therapeutic effect of DBS for PD and has the potential to refine target selection strategies for brain stimulation.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40120-022-00331-1.

Endoscopic Surgery for Supratentorial Deep Cavernous Malformation Adjacent to Cortical Spinal Tract: Preliminary Experience and Technical Note.

In this study, we aimed to introduce a technical note and to explore the efficacy of endoscopic surgery combined with diffusion tensor imaging (DTI) navigation for supratentorial deep cerebral cavernous malformations (CCM). A prospectively maintained database of CCM patients was reviewed to identify all CCM patients treated by endoscopic surgery. The sagittal T1-weighted anatomical magnetic resonance imaging (MRI) and DTI were acquired before surgery. Endoscopic surgery was planned and performed based on preoperative DTI images and intraoperative DTI navigation. All patients were followed up more than 6 months. Motor function deficit and modified Rankin scale (mRS) scores were documented on follow-up. A final mRS score of 0–2 was considered a good outcome, and a final mRS score >2 was considered a poor outcome. Second DTI and 3DT1 were performed at 3 months after surgery. We tracked the ipsilateral corticospinal tract (CST) on pre- and postoperative DTI images. The overall mean FA values and the number of fibers of tracked CST were compared on pre- and postoperative DTI images. Risk factors associated with motor deficits and poor outcomes were analyzed. Seven patients with deep CCM and treated by endoscopic surgery were enrolled in this study. The mean value of preoperative mRS was 1.5 ± 0.98, but that score recovered to 0.86 ± 1.22 3 months later. The mRS scores were improved significantly according to statistical analysis (p = 0.012). According to the Spearman non-parametric test, only the fiber number of ipsilateral CST on postoperative DTI was significantly associated with muscle strength 6 months after surgery (p = 0.032). Compared with preoperative CST characteristics on DTI, the change of FA value (p = 0.289) and fiber number (p = 0.289) of ipsilateral CST on postoperative DTI was not significant It meant that the CST was protected during endoscopic surgery. Endoscopic surgery based on DTI navigation might be an effective method to protect fiber tracts in supratentorial deep CCM patients and improve long-term outcomes. However, more studies and cases are needed to confirm our findings.

Temporopolar amygdalohippocampectomy: seizure control and postoperative outcomes.

The objective of this study was to evaluate the efficacy and safety of a modified surgical approach for the treatment of temporal lobe epilepsy secondary to hippocampal sclerosis (HS). This modified approach, called temporopolar amygdalohippocampectomy (TP-AH), includes a transsylvian resection of the temporal pole and subsequent amygdalohippocampectomy utilizing the limen insula as an anatomical landmark. A total of 61 patients who were diagnosed with HS and underwent TP-AH between 2013 and 2017 were enrolled. Patients performed pre- and postoperative diffusion tensor imaging and were classified according to Engel's scale for seizure control. To evaluate the functional preservation of the temporal stem white-matter fiber tracts, the authors analyzed postoperative Humphrey perimetries and pre- and postoperative neurocognitive performance (Rey Auditory Verbal Learning Test [RAVLT], Weschler Memory Scale-Revised [WMS-R], intelligence quotient [IQ], Boston Naming Test [BNT], and semantic and phonemic fluency). Demographic data and surgical complications were also recorded and described. After a median follow-up of 36 ± 16 months, 46 patients (75.4%) achieved Engel class I, of whom 37 (60.6%) were Engel class IA. No significant changes in either the inferior frontooccipital fasciculus and optic radiation tractography were observed postoperatively for both left- and right-side surgeries. Reliable perimetry was obtained in 40 patients (65.6%), of whom 27 (67.5%) did not present any visual field defects (VFDs) attributable to surgery, while 12 patients (30%) presented with quadrant VFD, and 1 patient (2.5%) presented with hemifield VFD. Despite a significant decline in verbal memory (p = 0.007 for WMS-R, p = 0.02 for RAVLT recognition), there were significant improvements in both IQ (p < 0.001) and visual memory (p = 0.007). Semantic and phonemic fluency, and scores on the BNT, did not change postoperatively. TP-AH provided seizure control similar to historical temporal lobe approaches, with a tendency to preserve the temporal stem and a satisfactory incidence of VFD. Despite a significant decline in verbal memory, there were significant improvements in both IQ and visual memory, along with preservation of executive function. This approach can be considered a natural evolution of the selective transsylvian approach.

Diffusion Tensor Imaging Connectomics Reveals Preoperative Neural Connectivity Changes in Children with Postsurgical Posterior Fossa Syndrome.

Posterior fossa syndrome (PFS), characterized by loss of language and other neurological impairments within the immediate postoperative period, occurs in approximately 25% of children who undergo surgical resection of posterior fossa tumors. Diffusion tensor imaging connectomics offer promise for elucidation of pathway-level disruption in neural connectivity of patients with this disorder. We aim to determine differences in pre- and postoperative connectomics between children with PFS and children with mild or no language deficit after surgery. Pre- and postoperative diffusion tensor imaging connectomics were applied and compared among patients with PFS, mild deficits, and intact language. A total of 35 patients were included in the study. Twenty-three patients with preoperative data and 24 patients with postoperative data were included in the analysis. Mean ages: PFS-8.5 years, mild-3.1 years, intact language-9.4 years (P = .02). Diagnoses included medulloblastoma (44.1%), pilocytic astrocytoma (28.6%), ependymoma (8.6%), other (11.4%), and unknown (8.6%). Five (21.7%) patients had PFS, 4 (17.4%) had mild deficits, and 14 (60.9%) had intact language. The assortativity coefficient was significantly higher in patients with PFS when compared to patients with mild deficits (P = .023). In the connectometry analyses, decreased connectivity was found involving the corpus callosum, right corticothalamic pathway, and right corticostriatal pathway in patients with PFS when compared to patients with intact language. Our findings revealed significant differences in preoperative neural connectivity involving the corticothalamic and other pathways among children who did, versus who did not, develop PFS postoperatively. Diffusion tensor imaging connectomics offers a unique opportunity to study the effect of the posterior fossa tumors on cerebello-cerebral networks and provide new insights into the mechanism of the structural plasticity/reorganization after surgery.

Impact of Multi-modality Monitoring Using Direct Electrical Stimulation to Determine Corticospinal Tract Shift and Integrity in Tumors using the Intraoperative MRI.

Preserving the integrity of the corticospinal tract (CST) while maximizing the extent of tumor resection is one of the key principles of brain tumor surgery to prevent new neurologic deficits. Our goal was to determine the impact of the use of perioperative diffusion tensor imaging (DTI) fiber-tracking protocols for location of the CSTs, in conjunction with intraoperative direct electrical stimulation (DES) on patient neurologic outcomes. The role of combining DES and CST shift in intraoperative magnetic resonance imaging (iMRI) to enhance extent of resection (EOR) has not been studied previously. A total of 53 patients underwent resection of tumors adjacent to the motor gyrus and the underlying CST between June 5, 2009, and April 16, 2013. All cases were performed in the iMRI (BrainSuite 1.5 T). Preoperative DTI mapping and intraoperative cortical and subcortical DES including postoperative DTI mapping were performed in all patients. There were 32 men and 21 women with 40 high-grade gliomas (76%), 4 low-grade gliomas (8%), and 9 (17%) metastases. Thirty-four patients (64%) were newly diagnosed, and 19 (36%) had a previous resection. There were 31 (59%) right-sided and 22 (42%) left-sided tumors. Eighteen patients (34%) had a re-resection after the first intraoperative scan. Most patients had motor-only mapping, and one patient had both speech and motor mapping. Relative to the resection margin, the CST after the first iMRI was designated as having an outward shift (OS), inward shift (IS), or no shift (NS). A gross total resection (GTR) was achieved in 41 patients (77%), subtotal resection in 4 (7.5%), and a partial resection in 8 (15%). Eighteen patients had a re-resection, and the mean EOR increased from 84% to 95% (p = 0.002). Of the 18 patients, 7 had an IS, 8 an OS, and in 3 NS was noted. More patients in the OS group had a GTR compared with the IS or NS groups (p = 0.004). Patients were divided into four groups based on the proximity of the tumor to the CST as measured from the preoperative scan. Group 1 (32%) included patients whose tumors were 0 to 5 mm from the CST based on preoperative scans; group 2 (28%), 6 to 10 mm; group 3 (13%), 11 to 15 mm; and group 4 (26%), 16 to 20 mm, respectively. Patients in group 4 had fewer neurologic complications compared with other groups at 1 and 3 months postoperatively (p = 0.001 and p = 0.007, respectively) despite achieving a similar degree of resection (p = 0.61). Furthermore, the current of intraoperative DES was correlated to the distance of the tumor to the CST, and the regression equation showed a close linear relationship between the two parameters. Combining information about intraoperative CST and DES in the iMRI can enhance resection in brain tumors (77% had a GTR). The relative relationship between the positions of the CST to the resection cavity can be a dynamic process that could further influence the surgeon's decision about the stimulation parameters and EOR. Also, the patients with an OS of the CST relative to the resection cavity had a GTR comparable with the other groups.

Reduced Fractional Anisotropy of Superior Cerebellar Peduncle is Associated With Persistent Ataxia in Children Undergoing Resection of Posterior Fossa Tumors

Abstract INTRODUCTION Persistent neurological deficits are seen in over 60% of children after resection of posterior fossa tumors. The goal of this study was to determine if these deficits are associated with persistent structural injury to white matter tracts. METHODS Demographic, clinical, and imaging data were reviewed for children undergoing resection of posterior fossa tumors at a tertiary care pediatric hospital. Preoperative, early postoperative (within 48 h of injury) and follow-up diffusion tensor imaging (DTI) were analyzed. Fractional anisotropy (FA) of the middle and superior cerebellar peduncles (SCP) were measured using manual regions of interest. Mean FA values before and after surgery were compared using paired sample T-test. Preoperative, postoperative and follow-up FA values were compared between patients with and without persistent neurological deficits. Statistical significance was set at P &lt; .05. RESULTS A toal of 20 patients (12 male, mean age 6.1 ± 4.1 yr) were included in this study. A total of Twelve patients (60%) underwent a trans-vermian approach and 15 patients (75%) underwent gross total resection. All patients had preoperative DTI scans, and follow-up DTI scans were available for 18 patients at a median duration of 19.7 mo (range 4-57.9 mo). Compared to preoperative DTI, FA of the left SCP was significantly reduced on early postoperative DTI scans (0.44 ± 0.07 vs 0.53 ± 0.1, P = .003). Significant reduction in left SCP FA on follow-up DTI was seen in patients with persistent ataxia at follow-up (0.43 ± 0.1 vs 0.55 ± 0.1, P = .016). Patients with persistent ataxia at follow-up (n = 10) had significantly lower FA of the left SCP at follow-up compared to patients who recovered from early postoperative ataxia (n = 4) (0.43 ± 0.1 vs 0.55 ± 0.04, P = .04). CONCLUSION Reduced FA of the SCP is associated with persistent ataxia at follow-up in children undergoing resection of posterior fossa tumors.

Posterior fossa syndrome and increased mean diffusivity in the olivary bodies.

Posterior fossa syndrome (PFS) is a common postoperative complication following resection of posterior fossa tumors in children. It typically presents 1 to 2 days after surgery with mutism, ataxia, emotional lability, and other behavioral symptoms. Recent structural MRI studies have found an association between PFS and hypertrophic olivary degeneration, which is detectable as T2 hyperintensity in the inferior olivary nuclei (IONs) months after surgery. In this study, the authors investigated whether immediate postoperative diffusion tensor imaging (DTI) of the ION can serve as an early imaging marker of PFS. The authors retrospectively reviewed pediatric brain tumor patients treated at their institution, Lucile Packard Children's Hospital at Stanford, from 2004 to 2016. They compared the immediate postoperative DTI studies obtained in 6 medulloblastoma patients who developed PFS to those of 6 age-matched controls. Patients with PFS had statistically significant increased mean diffusivity (MD) in the left ION (1085.17 ± 215.51 vs 860.17 ± 102.64, p = 0.044) and variably increased MD in the right ION (923.17 ± 119.2 vs 873.67 ± 60.16, p = 0.385) compared with age-matched controls. Patients with PFS had downward trending fractional anisotropy (FA) in both the left (0.28 ± 0.06 vs 0.23 ± 0.03, p = 0.085) and right (0.29 ± 0.06 vs 0.25 ± 0.02, p = 0.164) IONs compared with age-matched controls, although neither of these values reached statistical significance. Increased MD in the ION is associated with development of PFS. ION MD changes may represent an early imaging marker of PFS.

Association between postoperative DTI metrics and neurological deficits after posterior fossa tumor resection in children.

Resection of posterior fossa tumors in children may be associated with persistent neurological deficits. It is unclear if these neurological deficits are associated with persistent structural damage to the cerebellar pathways. The purpose of this research was to define longitudinal changes in diffusion tensor imaging (DTI) metrics in white matter cerebellar tracts and the clinical correlates of these metrics in children undergoing resection of posterior fossa tumors. Longitudinal brain DTI was performed in a cohort of pediatric patients who underwent resection of posterior fossa tumors. Fractional anisotropy (FA) of the superior cerebellar peduncles (SCPs) and middle cerebellar peduncles (MCPs) was measured on preoperative, postoperative, and follow-up DTI. Early postoperative (< 48 hours) and longer-term follow-up neurological deficits (mutism, ataxia, and extraocular movement dysfunction) were documented. Statistical analysis was performed to determine differences in FA values based on presence or absence of neurological deficits. Statistical significance was set at p < 0.05. Twenty children (mean age 6.1 ± 4.1 years [SD], 12 males and 8 females) were included in this study. Follow-up DTI was performed at a median duration of 14.3 months after surgery, and the median duration of follow-up was 19.7 months. FA of the left SCP was significantly reduced on postoperative DTI in comparison with preoperative DTI (0.44 ± 0.07 vs 0.53 ± 0.1, p = 0.003). Presence of ataxia at follow-up was associated with a persistent reduction in the left SCP FA on follow-up DTI (0.43 ± 0.1 vs 0.55 ± 0.1, p = 0.016). Patients with early postoperative mutism who did not recover at follow-up had significantly decreased FA of the left SCP on early postoperative DTI in comparison with those who recovered (0.38 ± 0.05 vs 0.48 ± 0.06, p = 0.04). DTI after resection of posterior fossa tumors in children shows that persistent reduction of SCP FA is associated with ataxia at follow-up.

Diffusion tensor imaging as an additional postoperative prognostic predictor factor in cervical myelopathy patients: An observational study.

Introduction:Multiple investigation modalities have been invented for diagnosis and for planning management of degenerative cervical myelopathy, which include magnetic resonance imaging (MRI), computed tomography scan, and plain X-rays. Diffusion tensor imaging (DTI) of the spinal cord is a special variety of MRI where diffusion of water molecules across and along the tracts is mapped. The changes in anisotropy at the stenotic level can be a postoperative prognostic factor. The aim of this study was to establish postoperative prognostic predictive value of DTI in cases of degenerative cervical myelopathy.Materials and Methods:The study included 30 indoor patients in a tertiary care hospital diagnosed with degenerative compressive cervical myelopathy based on both clinical and radiological parameters with complete clinical data including follow-up. All patients with medical neurological diseases, cases who underwent repeat surgery, cases who developed surgical site infection, and those patients who were lost to follow-up were excluded from the study. The patients underwent operative decompression through either anterior or posterior approach with or without fixation with titanium implants as per indication. All patients underwent pre- and postoperative DTI. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were noted in both pre- and postoperative imaging. Epidemiological data such as age and sex were noted. Pre- and postoperative modified Japanese Orthopedic Association (mJOA) scores were calculated.Results:There was a significant improvement in FA values postoperatively. Preoperatively, both FA and ADC values showed a significant correlation with preoperative Neurological status of the patient while postoperatively only FA values were found to be significantly correlated. The regression equations for determining postoperative mJOA score based on preoperative FA and ADC values revealed mJOA = 9.77 + 12.1 (FA), mJOA = 14.2 + 2408.4 (ADC), and mJOA = 9.54 + 11.2 (FA) +1575.5 (ADC). This means that postoperative mJOA score, i.e., postoperative clinical status improvement can be determined using DTI variables which are an objective preoperative data. However, relative strength of prediction for FA value is 66.7% and for ADC value is 28.7%.Conclusion:DTI tractography of the spinal cord will be a helpful objective prognostic factor for patients in whom surgery is planned. However, a study with larger subject size is required to increase the accuracy of determination of regression coefficient.

Microstructural changes are coincident with the improvement of clinical symptoms in surgically treated compressed nerve roots

Diffusion tensor imaging (DTI) has been widely used to visualize peripheral nerves, but the microstructure of compressed nerve roots can be assessed using DTI. However, there are no data regarding the association among microstructural changes evaluated using DTI, the symptoms assessed using the Oswestry Disability Index (ODI) and the duration of symptoms after surgery in patients with lumbar disc herniation (LDH). Thirty patients with unilateral radiculopathy were investigated using DTI. The changes in the mean fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) values as well as the correlation between these changes and the severity and duration of the clinical symptoms were investigated before and at least one month after surgery. The FA values were significantly increased after surgical treatment (p < 0.0001). Both the ADC and ODI values were noticeably decreased (p < 0.0001). A strong positive correlation between the preoperative and postoperative DTI parameters (p < 0.0001) as well as between the preoperative ODI and postoperative ODI/ODI changes (p < 0.0001) were found. In addition, there was a significant positive correlation between the changes in the DTI parameters and changes in the ODI (p < 0.0001). This preliminary study suggests it may be possible to use DTI to diagnose, quantitatively evaluate and follow-up patients with LDH.

Efficacy of Diffusion Tensor Imaging Indices in Assessing Postoperative Neural Recovery in Cervical Spondylotic Myelopathy.

Prospective observational cohort study. The aim of this study was to analyze the efficacy of diffusion tensor imaging (DTI) anisotropy indices in predicting the postoperative recovery in cervical spondylotic myelopathy (CSM) patients and to describe postoperative changes in the DTI indices based on neurological recovery after surgery. Surgical results of CSM are unpredictable and cannot be estimated based on preoperative MRI. DTI indices were found to have good sensitivity to detect changes in CSM, but their efficacy in predicting postoperative recovery and postoperative changes in DTI indices has not been studied before. Thirty-five patients who underwent surgical decompression for cervical spondylotic myelopathy underwent DTI evaluation preoperatively and postoperatively at 12 months. DTI indices-fractional anisotropy, apparent diffusion coefficient (ADC), relative anisotropy, volume ratio, and eigen vectors (E1, E2, and E3)-were obtained and clinical evaluations were made preoperatively and 12 months postoperatively. Twenty-six patients were available for final follow-up at 12 months. Twenty patients showed improvement by at least 1 Nurick grade, five maintained the preoperative Nurick grade status and one patient was noted to have deterioration by 1 grade. The preoperative DTI values could not predict neurological recovery patterns postoperatively. Although conventional MRI showed adequate decompression in all patients irrespective of the clinical outcome, DTI indices showed variable results. There were significant improvements in postoperative DTI indices for ADC (P = 0.002), E1 (P < 0.001), and E2 (P = 0.012) values in patients who showed neurological recovery at 12 months. Postoperative DTI indices for coefficients ADC, E1, and E2 in neurologically static/worsened individuals remained unchanged or insignificant (P = 0.05) CONCLUSION.: The DTI indices were sensitive enough to indicate postoperative neurological recovery observed following surgery. Preoperative DTI evaluation could not predict postoperative recovery for patients with cervical spondylotic myelopathy. 4.

Postoperative axonal changes in the contralateral hemisphere in children with medically refractory epilepsy: A longitudinal diffusion tensor imaging connectome analysis

To determine brain plasticity changes due to resective epilepsy surgery in children, we performed a longitudinal connectome analysis on the pattern of axonal connectivity in the contralateral hemisphere. Pre- and postoperative diffusion tensor imaging (DTI) data were acquired from 35 children with intractable focal epilepsy. A total of 54 brain regions of interest (ROIs) were generated in the hemisphere contralateral to the resection. Within a 54×54 connectivity matrix, a pairwise connectivity score was calculated for each connection between two ROIs, based on the DTI fiber streamline number in each connection. A permuted Spearman's ρ-rank analysis was used to identify specific inter-regional connections showing a significant association between the postoperative change of connectivity score and clinical variables. Nineteen connections in the contralateral hemisphere showed postoperative increases in the strength of connectivity. Postoperative increase in connectivity between insular-inferior frontal operculum regions as well as that between superior frontal orbital and mid frontal orbital regions were both significantly associated with a larger surgical resection volume (ρ>+0.40) and a younger patient age (ρ>-0.34). These increases were more robust in patients with frontal resection and in those achieving seizure freedom. Neuropsychological evaluation on subsets of patients revealed that such increases in connectivity were associated with preserved or improved cognitive functions such as visual memory and planning. Resective epilepsy surgery may lead to increased contralateral axonal connectivity in children with focal epilepsy. Our data lead to a hypothesis that such increased connectivity may be an imaging marker of postoperative brain plasticity to compensate for cognitive function. Hum Brain Mapp 37:3946-3956, 2016. © 2016 Wiley Periodicals, Inc.

Application of neuronavigation multimodal fusing combining intraoperative electrophysiological techniques in the tumor surgery of brain motor areas

Objective To investigate the clinical application value of neuronavigation multimodal fusing (DTI and BOLD) combining intraoperative electrophysiological monitoring techniques in tumor surgery of brain motor areas. Methods From October 2014 to January 2015, 20 right-handed patients whose lesions were located near the brain motor areas admitted to the Department of Neurosurgery, Changhai Hospital, the Second Military Medical University were analyzed retrospectively. The patients received preoperative magnetic resonance diffusion tensor imaging (DTI) and blood oxygen level dependent-functional magnetic resonance imaging (BOLD-fMRI) examinations. The original data of white matter fiber tracts and BOLD data were obtained. The neural navigation multimodal fusion DTI, BOLD, anatomical images [brain magnetic resonance venography (MRV), if necessary], and the three-dimensional reconstruction were performed. The microsurgery was performed under the assisted navigation during the operation, and the anterior central gyrus, central sulcus, posterior central gyrus, and subcortical tracts were determined under the neural electrophysiological monitoring. Results Of the 20 patients with motor area tumor, the lesions of 17 patients were resected, and 3 were resected subtotally. The intraoperative electrophysiological results were consistent with the preoperative DTI and BOLD reconstructed results. Postoperative pathological results: 9 patients had glioma (low-level 4 and high-level 5) and 11 had meningioma. The postoperative muscle strength of 15 patients did not have any change, 5 had transient hemiparesis. DTI showed that there was no obvious damage to the nerve tracts at 24 h after procedure. After being followed up for 2 weeks to 3 months, the patients were able to take care of themselves. Conclusions Neuronavigation multimodal fusing can accurately locate the motor function areas, and combined electrophysiological monitoring can compensate for the errors caused by the drift of the neural navigation. The peripheral adjacent tracks and functional areas were protected real timely during the operation in order to reduce the postoperative neurological dysfunction. The tumors were resected in a maximum degree within the safe range. In addition, the intraoperative electrophysiological monitoring and early postoperative DTI examination can predict the postoperative muscle strength and improve the postoperative quality of life of patients. Key words: Neuronavigation; Diffusion tensor imaging; Functional magnetic resonance imaging; Electrophysiology; Microsurgery

Chronic spatial working memory deficit associated with the superior longitudinal fasciculus: a study using voxel-based lesion-symptom mapping and intraoperative direct stimulation in right prefrontal glioma surgery

OBJECTIVE Although the right prefrontal region is regarded as a silent area, chronic deficits of the executive function, including working memory (WM), could occur after resection of a right prefrontal glioma. This may be overlooked by postoperative standard examinations, and the disabilities could affect the patient's professional life. The right prefrontal region is a part of the frontoparietal network and is subserved by the superior longitudinal fasciculus (SLF); however, the role of the SLF in spatial WM is unclear. This study investigated a persistent spatial WM deficit in patients who underwent right prefrontal glioma resection, and evaluated the relationship between the spatial WM deficit and the SLF. METHODS Spatial WM was examined in 24 patients who underwent prefrontal glioma resection (right, n = 14; left, n = 10) and in 14 healthy volunteers using a spatial 2-back task during the long-term postoperative period. The neural correlates of spatial WM were evaluated using lesion mapping and voxel-based lesion-symptom mapping. In addition, the spatial 2-back task was performed during surgery under direct subcortical electrical stimulation in 2 patients with right prefrontal gliomas. RESULTS Patients with a right prefrontal lesion had a significant chronic spatial WM deficit. Voxel-based lesion-symptom mapping analysis revealed a significant correlation between spatial WM deficit and the region that overlapped the first and second segments of the SLF (SLF I and SLF II). Two patients underwent awake surgery and had difficulties providing the correct responses in the spatial 2-back task with direct subcortical electrical stimulation on the SLF I, which was preserved and confirmed by postoperative diffusion tensor imaging tractography. These patients exhibited no spatial WM deficits during the postoperative immediate and long-term periods. CONCLUSIONS Spatial WM deficits may persist in patients who undergo resection of the tumor located in the right prefrontal brain parenchyma. Injury to the dorsal frontoparietal subcortical white matter pathway, i.e., the SLF I or SLF I and II, could play a causal role in this chronic deficit. A persistent spatial WM deficit, without motor and language deficits, could affect the professional life of the patient. In such cases, awake surgery would be useful to detect the spatial WM network with appropriate task during tumor exploration.

Preoperative and Postoperative Diffusion Tensor Imaging in Patients with Extra-Axial Lesions at the Frontal or Temporal Regions of the Brain and Their Correlations with Neuropsychological Outcomes

The underlying changes in the neuronal connectivity adjacent to brain tumours cannot always be depicted by conventional MR imaging. The hypothesis of this study was that preoperative neuropsychological deficits were associated with impairment of diffusivity in association fibre bundles. Hence, we investigated the potential of combined diffusion tensor imaging (DTI) fibre tracking and fractional anisotropy (FA) values of the fibres to determine changes in association fibres and their correlation to neuropsychological scores. Our study consisted of eighteen patients with extra-axial brain tumours in areas adjacent to the frontal and temporal lobes. They were assessed pre- and postoperatively with DTI and neuropsychological assessments. MR examinations were performed on a 3T-scanner. FA values were calculated for the uncinate fasciculus, arcuate fasciculus, superior fronto-occipital fasciculus, inferior fronto-occipital fasciculus and corticospinal tracts ipsilateral and contralateral to the tumor. These values were compared with neuropsychological scores for language, memory and attention. The analysis revealed marked differences in pre- and post-excision of the tumor in both FA values and neuropsychological scores. Quantitative DTI was able to show significant differences in diffusivity of the association fibres before and after the surgery (P < 0.05). The additional use of DTI-fibre integrity and neuropsychological tests may aid in prognostication and decision making prior to surgery.