Postoperative Fractional Anisotropy Research Articles

Preserved White Matter Integrity and Recovery After Brain Tumor Surgery: A Prospective Pilot Study on the Frontal Aslant Tract.

Introduction: Damage to white matter tracts can cause severe neurological deficits, which are often hardly predictable before brain tumor surgery. To explore the possibility of assessing white matter integrity and its preservation, we chose the frontal aslant tract (FAT) due to its involvement in multiple neurological functions such as speech and movement initiation. Methods: Right-handed patients with left hemispheric intracerebral tumors underwent FAT tractography within 7 days before and 3 days after surgery. Neurological performance score and aphasia score were assessed within 7 days before and after surgery, as well as at follow-up 3 months postoperatively. Results: Fifteen patients were prospectively analyzed. After multivariate analysis and receiver operating characteristic analysis, we found that preoperative fractional anisotropy (FA) of the left FAT indicated the preoperative aphasia score (cutoff 0.40, p = 0.015). Aphasia scores 3 months postoperatively were predicted by both postoperative FA of the left FAT (cutoff 0.35, p = 0.005) and postoperatively preserved FA of the left FAT (cutoff 95.8%, p = 0.017). Postoperatively preserved right FAT FA inversely predicted postoperative aphasia score (cutoff 95.1%, p = 0.016). Discussion: Assessment of white matter integrity preservation is possible and correlates with outcome after brain tumor surgery. It may be useful for patient counseling and assessment of rehabilitation potential, as well as to investigate relevant brain networks in the future. Clinical Trial Registration: The trial was prospectively registered at ClinicalTrials.gov (NCT04302857).

Analysis of the Curative Effect of Diffusion Tensor Imaging-Guided Percutaneous Endoscopic Lumbar Discectomy

Diffusion tensor imaging (DTI), a novel method of describing nerve structure, is a special form of magnetic resonance imaging (MRI). This new imaging method can be used to locate the diseased nerve roots in lumbar disc herniation. The objective of this study is to compare patient outcomes between single-level and doublesection percutaneous endoscopic lumbar discectomy (PELD) in the treatment of lumbar intervertebral disc herniation with single nerve root compression, where single-sided PELD is guided by magnetic resonance diffusion tensor imaging (DTI). The clinical data of patients with lumbar intervertebral disc herniation with double compression of single nerve root symptoms in the Affiliated Hospital of Weifang Medical University from January 2019 to May 2021 were retrospectively summarized and divided into single-level percutaneous endoscopic discectomy (PELD) group after DTI localization and double-section PELD group. The operation time, intraoperative bleeding, VAS score and JOA score of the two groups were compared, as well as the preoperative and postoperative fractional anisotropy (FA) values in the DTI group. The operation time and intraoperative bleeding volume of patients in the DTI group were significantly lower than those in the double segment group, and there was no significant difference between VAS scores and JOA scores in the two groups. After the operation, the nerve root FA value of the responsible compression site of patients in the DTI group increased significantly, but it was still lower than the healthy symmetrical part. The single-level PELD based on DTI has achieved a similar effect to that of the doublesegment PELD in 3 months after the operation, which can improve the FA value of the lesion nerve root. Its bleeding amount is less, and the operation time is shorter, but the efficacy of this technology still requires long-term follow-up of large samples.

Use of diffusion tensor imaging as a prognostic biomarker after decompression surgery for carpal tunnel syndrome.

Magnetic resonance diffusion tensor imaging (MR-DTI) has been increasingly applied for carpal tunnel syndrome (CTS) diagnosis, but relatively little is known about the effect of CTS treatment on median nerve (MN) integrity and functional outcome prediction. To assess how structural changes in MR-DTI of the MN correlates with symptom severity, functional status, and electrophysiological parameters in patients suffering from CTS before and after decompression surgery. Nine wrists were prospectively enrolled to perform MR-DTI pre- and postoperatively. The apparent diffusion coefficients (ADC) and fractional anisotropy (FA) of the MN were examined in three different regions-distal radioulnar joint, pisiform bone, and hamate bone-and correlated with clinical and electrophysiological parameters. Postoperatively, mean Boston Carpal Tunnel Questionnaire scores decreased 1.55 points (range = 0.08-3; P = 0.0172) and 1.01 points (-0.13 to 1.88; P = 0.0381) in the symptomatic and functional domains, respectively. Postoperative clinical improvement was reflected in proximal FA elevation (P = 0.0078), but not in diffusivity in comparison to baseline examination. Preoperative electrophysiological parameters were correlated with a reduction in the pre- (sensory latencies [rho = -0.6826; P = 0.0312]) and postoperative (motor latencies [rho = -0.7488; P = 0.0325]) distal FA values. Higher sensory amplitudes indicated higher postoperative proximal FA values (rho = 0.7618; P = 0.0280) ​​and lower postoperative proximal ADC values (rho = -0.9047; P = 0.0020). Our study demonstrated that pre- and postoperative proximal FA values are useful biomarkers for the structural evaluation of the MN in patients with CTS. Symptomatic improvement can be better predicted by analyzing FA changes.

Quantitative Evaluation of Intraspinal Lumbar Disc Herniation-related Lumbosacral Radiculopathy Before and After Percutaneous Transforaminal Endoscopic Discectomy Using Diffusion Tensor Imaging.

A prospective study. The aim of this study was to investigate the relationship between diffusion tensor imaging (DTI) derived parameters of compressed nerve roots at subregions and the corresponding clinical symptoms to evaluate the patients with intraspinal lumbar disc herniation (LDH)-related lumbosacral radiculopathy pre- and postoperatively. It is crucial to explore whether magnetic resonanve imaging (MRI) can quantitatively evaluate intraspinal LDH-related lumbosacral radiculopathy before and after surgery. In all, 66 patients underwent MRI scans and Clinical assessment before and after percutaneous transforaminal endoscopic discectomy (PTED). Pre- and postoperative findings of the related lumbar disk and nerve tractography were compared with two-way contingency table analysis. The embedded paired t test toolbox was applied to respectively compare the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of nerves at the symptomatic and asymptomatic sides in three subregions pre- and postoperatively. The correlation of clinical Japanese Orthopedic Association (JOA) scores and FA/ADC values of nerves at three sub-regions was analyzed by stepwise multiple linear regression analysis. The postoperative FA values were significantly higher than the corresponding preoperative values (P < 0.001), while comparable ADC values were found. Using tractography, a notable improvement of compressed nerve was revealed after surgery (61 cases, 92.4%). Additionally, multiple linear regression analysis identified significant associations between JOA scores and FA values of the compressed nerves with the greatest effect at the proximal region. The FA values at subarticular zone can reflect the microstructural changes of the corresponding compressed nerves and well associate with clinical symptoms. Therefore, the DTI parameter FA can be considered an effective tool in clinic to quantitatively evaluate intraspinal LDH-related lumbosacral radiculopathy before and after PTED surgery.Level of Evidence: 3.

The Functional Relevance of Diffusion Tensor Imaging in Patients with Degenerative Cervical Myelopathy.

(1) Background: In addition to conventional magnetic resonance imaging (MRI), diffusion tensor imaging (DTI) has been investigated as a potential diagnostic and predictive tool for patients with degenerative cervical myelopathy (DCM). In this preliminary study, we evaluated the use of quantitative DTI in the clinical practice as a possible measure to correlate with upper limbs function. (2) Methods: A total of 11 patients were enrolled in this prospective observational study. Fractional anisotropy (FA) values was extracted from DTI data before and after surgery using a GE Signa 1.5 T MRI scanner. The Nine-Hole Peg Test and a digital dynamometer were used to measure dexterity and hand strength, respectively. (3) Results: We found a significant increase of FA values after surgery, in particular below the most compressed level (p = 0.044) as well as an improvement in postoperative dexterity and hand strength. Postoperative FA values moderately correlate with hand dexterity (r = 0.4272, R2 = 0.0735, p = 0.19 for the right hand; r = 0.2087, R2 = 0.2265, p = 0.53 for the left hand). (4) Conclusion: FA may be used as a marker of myelopathy and could represent a promising diagnostic value in patients affected by DCM. Surgical decompression can improve the clinical outcome of these patients, especially in terms of the control of finger-hand coordination and dexterity.

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.

Visualization of peri-prostatic neurovascular fibers before and after radical prostatectomy by means of diffusion tensor imaging (DTI) with clinical correlations: preliminary report.

To evaluate if diffusion tensor imaging (DTI) is able to detect morphological changes of peri-prostatic neurovascular fibers (PNF) before and after robot-assisted radical prostatectomy (RARP) and if these changes are related to urinary incontinence (UI) and erectile dysfunction (ED). From October 2014 and August 2017, 26 patients with biopsy-proven prostate cancer underwent prostatic multiparametric magnetic resonance imaging (mp-MRI) including DTI sequencing before, and 6 months after, RARP. Images were analyzed by placing six regions of interest (ROI), respectively, at base, mid gland, and apex, one for each side, to obtain tractographic reconstruction of the PNF. Patients were asked to complete International Consultation Incontinence Questionnaire-Short Form (ICIQ-SF) and International Index of Erectile Function (IIEF-5) questionnaires before RARP and 6months post-operatively. Fractional anisotropy (FA), number (N), and length (L) of PNF before and after RARP were compared by means of Student's t test; Spearman's test was used to evaluate correlation between DTI parameters and questionnaires' scores. We observed a significant difference in N values before and after RARP (p < 0.001) and a negative correlation between IIEF-5 score and post-operative FA values at both the right (rho = - 0.42; p = 0.0456) and left (rho = - 0.66; p = 0.0006) base of the prostate. DTI with tractography of PNF is able to detect quantitative changes in N, L, and FA values in PNF after RARP. In particular, we observed an inverse correlation between FA of PNF and ED at 6months after RARP. Further investigations are needed to confirm this trend.

Longitudinal diffusion tensor imaging of patients with degenerative cervical myelopathy following decompression surgery

Previous studies have reported the utility of diffusion tensor imaging (DTI) as an imaging biomarker for the severity of myelopathy and subsequent surgical outcome in patients with degenerative cervical myelopathy (DCM). We hypothesized that DTI may reflect neurological recovery following surgery. The purpose of this study was to evaluate the ability of DTI to assess the post-operative alteration of neural status in patients with DCM as well as to predict post-operative recovery. We enrolled 15 patients with DCM who underwent decompression surgery. The Japanese Orthopaedic Association (JOA) score was evaluated before and 1 year after surgery. The participants were examined using DTI on a 3.0 T magnetic resonance scanner before, and 1 year after surgery. Fractional anisotropy (FA) and mean diffusivity (MD) were assessed for both time points. The correlations between the pre- and post-operative FA and MD values and the pre- and post-operative JOA scores were analyzed. Although the JOA score improved significantly after surgery from 8.9 to 12.3, there was no significant change between the pre- and post-operative FA and MD values. The post-operative outcomes after 1 year moderately correlated with the pre-operative FA values (Spearman’s ρ = 0.55, p = 0.03 and Spearman’s ρ = 0.56, p = 0.03 for change and recovery rate of the JOA score, respectively). However, there was no correlation between the post-operative FA and post-operative JOA scores nor between MD and clinical outcomes. DTI cannot be utilized as a biomarker for post-operative alterations of neural status of the spinal cord; however, pre-operative DTI may be useful as a predictor of surgical outcomes.

Identification of peri-prostatic neurovascular fibers before and after radical prostatectomy by means of diffusion tensor imaging (DTI) with clinical correlations: initial experience

Aim: To evaluate if Diffusion Tensor Imaging (DTI) is able to detect morphological changes of peri-prostatic neurovascular fibers (PNF) before and after robot-assisted radical prostatectomy (RARP) and if these changes are related to urinary incontinence (UI) and erectile dysfunction (ED). Materials and methods: From October 2014 and August 2017 26 patients with biopsy-proven prostate cancer underwent prostatic multi-parametric magnetic resonance imaging (mp-MRI) including DTI sequencing before and six months after, RARP. Images were analyzed by placing six regions of interest (ROI) respectively at the base, mid-gland and apex, one for each side, to obtain tractography reconstruction of the PNF. Patients were asked to complete an International Consultation Incontinence Questionnaire – Short Form (ICIQ-SF) and International Index of Erectile Function (IIEF-5) questionnaires before RARP and 6 months postoperatively. Fractional anisotropy (FA), number (N) and length (L) of PNF before and after RARP were compared by means of Student's t-test; Spearman test was used to evaluate the correlation between DTI parameters and questionnaires scores. We observed a significant difference in N values before and after RARP (p&lt;0.001) and a negative correlation between IIEF-5 score and post-operative FA values at both the right (rho=-0.42; p= 0.0456) and left (rho=- 0.66; p=0.0006) base of the prostate. DTI with tractography of PNF is able to detect quantitative changes in N, L and FA values in PNF after RARP. In particular we observed an inverse correlation between FA of PNF and ED at 6 months after RARP. Further investigations are needed to confirm this trend.

A change in brain white matter after shunt surgery in idiopathic normal pressure hydrocephalus: a tract-based spatial statistics study

BackgroundThe aim of this study was to elucidate changes in cerebral white matter after shunt surgery in idiopathic normal pressure hydrocephalus (INPH) using diffusion tensor imaging (DTI).MethodsTwenty-eight consecutive INPH patients whose symptoms were followed for 1 year after shunt placement and 10 healthy control (HC) subjects were enrolled. Twenty of the initial 28 INPH patients were shunt-responsive (SR) and the other 8 patients were non-responsive (SNR). The cerebral white matter integrity was detected by assessing fractional anisotropy (FA) and mean diffusivity (MD). The mean hemispheric DTI indices and the ventricular sizes were calculated, and a map of these DTI indices was created for each subject. The DTI maps were analysed to compare preshunt INPH with HC and preshunt INPH with 1 year after shunt placement in each INPH group, using tract-based spatial statistics. We restricted analyses to the left hemisphere because of shunt valve artefacts.ResultsThe ventricles became significantly smaller after shunt placement both in the SR and SNR groups. In addition, there was a significant interaction between clinical improvement after shunt and decrease in ventricular size. Although the hemispheric DTI indices were not significantly changed after shunt placement, there was a significant interaction between clinical improvement and increase in hemispheric MD. Compared with the HC group, FA in the corpus callosum and in the subcortical white matter of the convexity and the occipital cortex was significantly lower in SR at baseline, whereas MD in the periventricular and peri-Sylvian white matter was significantly higher in the SR group. Compared with the pre-operative images, the post-operative FA was only decreased in the corona radiata and only in the SR group. There were no significant regions in which DTI indices were altered after shunt placement in the SNR group.ConclusionsBrain white matter regions in which FA was decreased after shunt placement were in the corona radiata between the lateral ventricles and the Sylvian fissures. This finding was observed only in shunt-responsive INPH patients and might reflect the plasticity of the brain for mechanical pressure changes from the cerebrospinal fluid system.

Brain Microstructural White and Gray Matter Alterations after Cardiopulmonary Bypass: Anatomical Distribution and Corresponding Neurocognitive Deficit

Background: We sought to detect microstructural brain injury after coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB) and to define its anatomical distribution. Analyses were performed to determine possible correlation with postoperative neurocognitive deficit.Methods: Seven patients undergoing CPB-CABG were assigned for serial cerebral designated diffusion tensor (DTI)-magnetic resonance imaging (MRI) examinations, preoperatively, on postoperative day (POD) 1 and 5. Levels of mean diffusivity (MD) and fractional anisotropy (FA) were analysed to assess gray and white matter injury. BBBdisruption and microembolic load were concomitantly evaluated by dynamic contrast enhancement (DCE)-MRI and diffusion-weighted imaging (DWI)-MRI methods, respectively. Neuropsychological tests were performed one day preoperatively and on POD 5.Results: Increase in MD and decrease in FA were evident on POD 1 in gray matter structures including the hippocampus (MD, 0.000768 mm2/s ± 0.0000347 versus 0.000804 mm2/s ± 0.0000267, p<0.01; FA, 0.180 ± 0.03 mm2/s versus 0.163 mm2/s ± 0.032, p<0.01), middle frontal gyrus (MD, 0.000989 mm2/s ± 0.0000487 versus 0.001068 mm2/s ± 0.0000553, p<0.01), orbital gyrus (MD, 0.000867 mm2/s ± 0.0000374 versus 0.000908 mm2/s ± 0.0000356, p<0.01) and in the following white matter structures: Superior longitudinal fasciculus (MD, 0.000836 mm2/s ± 0.0000384 versus 0.000874 mm2/s ± 0.0000359, p<0.01; FA, 0.324 mm2/s ± 0.018 versus 0.305 mm2/s ± 0.022, p<0.01), frontal white matter (FA, 0.277 mm2/s ± 0.031 versus 0.26 mm2/s ± 0.033, p<0.01) internal capsule (MD, 0.000772 mm2/s ± 0.0000648 versus 0.000803 mm2/s ± 0.0000601, p<0.01; FA,0.364 mm2/s ± 0.032 versus 0.343 mm2/s ± 0.029, p<0.01) and corticospinal tract (MD, 0.000759 mm2/s ± 0.0000557 versus 0.00078 mm2/s ± 0.0000591, p<0.01; FA, 0.440 mm2/s ± 0.023 versus 0.411 mm2/s ± 0.023, p<0.01). Corticospinal tract fibre tracing showed significant decrease in postoperative fibre number. DTI findings persisted through POD 5 without spontaneous regression. BBB-disruption reflected by increased K^trans was detected in five patients (71%) on POD 1, mainly in frontal lobes and spontaneously restored by POD 5. Postoperative global cognitive score was reduced in all patients (98.2 ± 12 vs. 95.1 ± 11, p=0.032), predominantly in executive function and attention (91.8 ± 13 vs. 86.9±12, p=0.042). Postoperative FA decline significantly correlated with delta K^trans (R=0.6) and with postoperative decline in attention and Go-no-Go response inhibition tests (R=0.66 and 0.63, respectively).Conclusion: CABG using CPB elicits gray and white matter microstructure injury in the above-mentioned anatomical distribution. These alterations are associated with transient BBB-disruption and may account for postoperative neurocognitive dysfunction.

Role of diffusion tensor imaging in evaluation of prognosis in patients with cervical intraspinal tumors

Objective To investigate the change characteristics of diffusion tensor imaging(DTI)parameters value in patients with cervical intraspinal tumor and its relationship with spinal cord function and prognosis. Methods Twenty-two patients with cervical intraspinal tumor(test group)treated with surgical resection in Department of Neurosurgery, Fuzhou General Hospital of Nanjing Military Command, Fuzhou Clinical Medicine School of the Second Military Medical University between February 2014 and January 2015 were selected. Cervical spinal cord MRI conventional sequences and DTI scans were performed at 3 days before procedure and 1 month after procedure respectively. At the same time, 22 healthy subjects were selected as healthy control(HC)group. The values of fractional anisotropy(FA)and apparent diffusion coefficient(ADC)of each cervical spinal cord level were measured in both groups. The whole cervical spinal cord was divided into 3 areas, the tumor head area, tumor area, and tumor tail area, and the FA and ADC values of the 3 areas were calculated. Differences of FA and ADC between two groups and their relationship with McCormick grading were compared and analyzed. Results The FA values of the 3 areas of cervical spinal cord of the test group were significantly lower than those of the HC group(all P<0.05), and the ADC values were significantly higher than those of the HC group(all P<0.05). There were significant differences in FA and ADC values among each area in test group(all P<0.05). The FA values in the tumor area and tumor head area at 1 month after procedure were increased significantly compared with those before procedure(all P<0.05). The improvement rate of spinal cord function in the group of increased FA value in tumor head area after procedure was significantly higher than that of the decreased group(P<0.05). The sensitivity of the change of postoperative FA values for predicting spinal cord function and prognosis in tumor head area was 88%. Conclusions The DTI index of cervical cord in patients with cervical intraspinal tumor may change significantly in the whole range of the cervical spinal cord. These changes after procedure may show different degrees of recovery in the different regions of cervical spinal cord, and it is associated with the improvement of cervical spinal cord function. The change of FA value in tumor head area after procedure is a rather sensitive predictor for spinal cord function and prognosis. Key words: Spinal cord neoplasms; Diffusion tensor imaging; Fractional anisotropy; Apparent diffusion coefficient

Distinct types of white matter changes are observed after anterior temporal lobectomy in epilepsy.

Anterior temporal lobectomy (ATL) is commonly adopted to control medically intractable temporal lobe epilepsy (TLE). Depending on the side of resection, the degree to which Wallerian degeneration and adaptive plasticity occur after ATL has important implications for understanding cognitive and clinical outcome. We obtained diffusion tensor imaging from 24 TLE patients (12 left) before and after surgery, and 12 matched controls at comparable time intervals. Voxel-based analyses were performed on fractional anisotropy (FA) before and after surgery. Areas with postoperative FA increase were further investigated to distinguish between genuine plasticity and processes related to the degeneration of crossing fibers. Before surgery, both patient groups showed bilateral reduced FA in numerous tracts, but left TLE patients showed more extensive effects, including language tracts in the contralateral hemisphere (superior longitudinal fasciculus and uncinate). After surgery, FA decreased ipsilaterally in both ATL groups, affecting the fornix, uncinate, stria terminalis, and corpus callosum. FA increased ipsilaterally along the superior corona radiata in both left and right ATL groups, exceeding normal FA values. In these clusters, the mode of anisotropy increased as well, confirming fiber degeneration in an area with crossing fibers. In left ATL patients, pre-existing low FA values in right superior longitudinal and uncinate fasciculi normalized after surgery, while MO values did not change. Preoperative verbal fluency correlated with FA values in all areas that later increased FA in left TLE patients, but postoperative verbal fluency correlated only with FA of the right superior longitudinal fasciculus. Our results demonstrate that genuine reorganization occurs in non-dominant language tracts after dominant hemisphere resection, a process that may help implement the inter-hemispheric shift of language activation found in fMRI studies. The results indicate that left TLE patients, despite showing more initial white matter damage, have the potential for greater adaptive changes postoperatively than right TLE patients.

Postoperative Cerebral White Matter Damage Associated with Cerebral Hyperperfusion and Cognitive Impairment after Carotid Endarterectomy: A Diffusion Tensor Magnetic Resonance Imaging Study

Background: Cerebral hyperperfusion after carotid endarterectomy (CEA), even when asymptomatic, often impairs cognitive function. However, conventional magnetic resonance (MR) imaging rarely demonstrates structural brain damage associated with postoperative cognitive impairment. MR diffusion tensor imaging (DTI) is potentially more sensitive for detection of white matter damage. Among the common parameters derived by DTI, fractional anisotropy (FA) is a marker of tract integrity, and mechanical disruption of axonal cylinders and loss of continuity of myelin sheaths may be responsible for reduced FA in white matter. The purpose of the present study was to determine whether postoperative cerebral white matter damage that can be detected by FA derived by DTI is associated with cerebral hyperperfusion after CEA and correlates with postoperative cognitive impairment. Methods: In 70 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), cerebral blood flow (CBF) was measured using single-photon emission computed tomography (SPECT) before and immediately after CEA and on postoperative day 3. FA values in cerebral white matter were assessed using DTI before and 1 month after surgery. These values were normalized and analyzed using statistical parametric mapping 5. In each corresponding voxel in the pre- and postoperative normalized FA maps of each patient, a postoperative FA value minus a preoperative FA value was calculated, and a voxel with postoperatively reduced FA was defined based on data obtained from healthy volunteers. The number of voxels with postoperatively reduced FA was calculated and defined as the volume with postoperatively reduced FA. Neuropsychological testing, consisting of the Wechsler Adult Intelligence Scale Revised, the Wechsler Memory Scale and the Rey-Osterreith Complex Figure test, was also performed preoperatively and after the first postoperative month. Postoperative cognitive impairment on neuropsychological testing in each patient was defined based on data obtained from patients with asymptomatic unruptured cerebral aneurysms. Results: Post-CEA hyperperfusion on brain perfusion SPECT (CBF increase ≥100% compared with preoperative values) and postoperative cognitive impairment on neuropsychological testing were observed in 11 (16%) and 9 patients (13%), respectively. The volume with postoperatively reduced FA in cerebral white matter ipsilateral to surgery was significantly greater in patients with post-CEA hyperperfusion than in those without (p < 0.0001). This volume in cerebral white matter ipsilateral to surgery was also significantly associated with postoperative cognitive impairment (95% confidence interval, 1.559–8.853; p = 0.0085). Conclusions: Cerebral hyperperfusion after CEA results in postoperative cerebral white matter damage that correlates with postoperative cognitive impairment.

PATH61 Structural plasticity of white matter networks following anterior temporal lobe resection

Anterior temporal lobe resection (ATLR) is an effective treatment for temporal lobe epilepsy (TLE). The structural consequences of ATLR and how these relate to language function after surgery remain unknown....

The structural plasticity of white matter networks following anterior temporal lobe resection

Anterior temporal lobe resection is an effective treatment for refractory temporal lobe epilepsy. The structural consequences of such surgery in the white matter, and how these relate to language function after surgery remain unknown. We carried out a longitudinal study with diffusion tensor imaging in 26 left and 20 right temporal lobe epilepsy patients before and a mean of 4.5 months after anterior temporal lobe resection. The whole-brain analysis technique tract-based spatial statistics was used to compare pre- and postoperative data in the left and right temporal lobe epilepsy groups separately. We observed widespread, significant, mean 7%, decreases in fractional anisotropy in white matter networks connected to the area of resection, following both left and right temporal lobe resections. However, we also observed a widespread, mean 8%, increase in fractional anisotropy after left anterior temporal lobe resection in the ipsilateral external capsule and posterior limb of the internal capsule, and corona radiata. These findings were confirmed on analysis of the native clusters and hand drawn regions of interest. Postoperative tractography seeded from this area suggests that this cluster is part of the ventro-medial language network. The mean pre- and postoperative fractional anisotropy and parallel diffusivity in this cluster were significantly correlated with postoperative verbal fluency and naming test scores. In addition, the percentage change in parallel diffusivity in this cluster was correlated with the percentage change in verbal fluency after anterior temporal lobe resection, such that the bigger the increase in parallel diffusivity, the smaller the fall in language proficiency after surgery. We suggest that the findings of increased fractional anisotropy in this ventro-medial language network represent structural reorganization in response to the anterior temporal lobe resection, which may damage the more susceptible dorso-lateral language pathway. These findings have important implications for our understanding of brain injury and rehabilitation, and may also prove useful in the prediction and minimization of postoperative language deficits.