Hideaki Nishimoto

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.

Postoperative Changes in Cerebral Metabolites Associated with Cognitive Improvement and Impairment after Carotid Endarterectomy: A 3T Proton MR Spectroscopy Study

This study assessed the use of metabolites seen on MRS as markers of change in cognitive status after carotid artery surgery. MRS and neurocognitive testing were obtained before and after surgery in 100 patients. The results showed that cognition remained unchanged in 80%, improved in 10%, and was impaired in 10% of patients postoperatively and that in these last 2 groups, NAA/Cr correlated well the clinical status. Thus, NAA/Cr may serve as a marker of neurologic status after carotid artery surgery (see accompanying editorial by Lövblad and Pereira). BACKGROUND AND PURPOSE: Cognitive function can improve or decline after carotid endarterectomy. Proton MR spectroscopy can be used evaluate cerebral metabolites, such as N-acetylaspartate, choline, and creatine, in vivo. The purpose of the present study was to determine whether postoperative changes in cerebral metabolites measured by using 3T proton MR spectroscopy were associated with changes in cognitive function after CEA. MATERIALS AND METHODS: In 100 patients undergoing CEA for ipsilateral cervical internal carotid artery stenosis (≥70%), brain proton MR spectroscopy was performed before and after surgery. NAA/Cr and Cho/Cr ratios were measured in regions of interest placed in the centrum semiovale of both cerebral hemispheres. Neuropsychological testing was also performed preoperatively and 1 month postoperatively. Multivariate statistical analysis of factors related to postoperatively changed cognition was performed, and odds ratios with 95% confidence intervals were calculated. RESULTS: On the basis of the neuropsychological assessments, 10 (10%), 80 (80%), and 10 (10%) patients were defined as having postoperatively improved, unchanged, and impaired cognition, respectively. A positive and high ΔNAA/Cr ratio (postoperative value–preoperative value) in the cerebral hemisphere ipsilateral to the operative site was significantly associated with postoperatively improved cognition (95% CI, 13.3–21.3; P = .0016). Negative and high absolute values of the ΔNAA/Cr ratio (95% CI, 0.018–0.101; P = .0039) and ΔCho/Cr ratio (95% CI, 0.042–0.135; P = .0046) in the ipsilateral cerebral hemisphere were significantly associated with postoperatively impaired cognition. CONCLUSIONS: Postoperative changes in cerebral metabolites measured by using proton MR spectroscopy were associated with changes in cognitive function after CEA.

Prediction of Motor Function Outcome after Intracerebral Hemorrhage Using Fractional Anisotropy Calculated from Diffusion Tensor Imaging

Background: The efficacy of surgical evacuation in patients with intracerebral hemorrhage (ICH) remains unclear for recovery of motor function. The relationship between improvement of motor function outcome and sequential change of fractional anisotropy (FA) values was investigated in patients with ICH, to explore whether motor function outcome can be predicted in the early phase. Indication of the surgical hematoma evacuation was also considered. Methods: This prospective study included 23 patients with ICH. All patients underwent diffusion tensor imaging to measure the FA value five times: within 3 days, day 14, day 30, day 60, and day 90 after the onset. The regions of interest were determined on the b = 0 step of the echo planar imaging scans in the bilateral cerebral peduncles and were automatically transferred onto the FA images. The FA value was then calculated for each patient. Patients were divided into good and poor recovery groups according to the motor function outcome on day 90. Results: The mean FA value of the poor recovery group gradually decreased until day 90, but remained unchanged in the good recovery group. The mean FA value on day 3 was significantly higher (p < 0.001) in the good recovery group (0.745 ± 0.0073) than in the poor recovery group (0.682 ± 0.0090). Receiver operating characteristic curve analysis showed that the FA value on day 3 could predict motor function outcome with a sensitivity of 100% and a specificity of 77.8% at an FA value of 0.7 on day 3. Conclusion: The main finding of this study was that the FA values of the cerebral peduncle on the pathological side in patients with ICH on day 3 could predict the motor function outcome on day 90.

Simple Assessment of Cerebral Hemodynamics Using Single-Slab 3D Time-of-Flight MR Angiography in Patients with Cervical Internal Carotid Artery Steno-Occlusive Diseases : Comparison with Quantitative Perfusion Single-Photon Emission CT

BACKGROUND AND PURPOSE: Visualization of the peripheral arteries on single-slab 3D time-of-flight (TOF) MR angiography (MRA) can reflect blood flow velocity. The velocity in the middle cerebral artery (MCA) may correlate with cerebrovascular reactivity (CVR) to acetazolamide, which can be used to assess hemodynamic impairment. The goal of this study was to compare the signal intensity of the MCA on MRA versus CVR quantified by perfusion single-photon emission CT (SPECT). MATERIALS AND METHODS: The signal intensity of the MCA on single-slab 3D time-of-flight MRA was graded according to the ability to visualize the MCA in 108 cerebral hemispheres of 87 patients with unilateral or bilateral cervical internal carotid artery (ICA) steno-occlusive diseases. SPECT-CVR was also calculated by measuring cerebral blood flow before and after acetazolamide challenge. Ten healthy subjects were studied to obtain control SPECT-CVR values. All subjects provided written informed consent before the study. RESULTS: CVR was significantly lower in cerebral hemispheres with reduced MCA signal intensity than in those with normal intensity (P < .05). When the reduced signal intensity of the MCA on MRA was defined as abnormal, and when a CVR less than the mean − 2 SD of healthy subjects was defined as reduced, MRA grading resulted in a 86.2% sensitivity and 69.6% specificity, with 51.0% positive-predictive and 93.2% negative-predictive values to detect reduced CVR. CONCLUSIONS: This simple MRA method can assess hemodynamic impairment with a high negative-predictive value.

Postoperative increase in cerebral white matter fractional anisotropy on diffusion tensor magnetic resonance imaging is associated with cognitive improvement after uncomplicated carotid endarterectomy: tract-based spatial statistics analysis.

BACKGROUND Carotid endarterectomy (CEA) might improve cognitive function. Fractional anisotropy (FA) values in the cerebral white matter derived from diffusion tensor magnetic resonance imaging (DTI) correlate with cognitive function in patients with various central nervous system diseases. OBJECTIVE To use tract-based spatial statistics to determine whether postoperative changes of FA values in the cerebral white matter derived from DTI are associated with cognitive improvement after uncomplicated CEA. METHODS In 80 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), FA values in the cerebral white matter were derived from DTI before and 1 month after surgery and were analyzed by using tract-based spatial statistics. 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. RESULTS Based on the neuropsychological assessments, 11 (14%) patients were defined as having postoperatively improved cognition. The difference between the 2 mean FA values (postoperative values minus preoperative values) in the cerebral hemisphere ipsilateral to surgery was significantly associated with postoperative cognitive improvement (95% confidence intervals, 2.632-9.877; P = .008). White matter FA values in patients with postoperative cognitive improvement were significantly increased after surgery in the whole ipsilateral cerebral hemisphere, in the contralateral anterior cerebral artery territory, and in the watershed zone between the contralateral anterior and middle cerebral arteries. CONCLUSION Postoperative increase in cerebral white matter FA on DTI is associated with cognitive improvement after uncomplicated CEA.

Brain Temperature Measured by Using Proton MR Spectroscopy Predicts Cerebral Hyperperfusion after Carotid Endarterectomy

PURPOSE To determine whether brain temperature measured by using preoperative proton magnetic resonance (MR) spectroscopy could help identify patients at risk for cerebral hyperperfusion after carotid endarterectomy (CEA). MATERIALS AND METHODS Institutional review board approval and informed consent were obtained. Acquisition of proton MR spectroscopic data by using point-resolved spectroscopy without water suppression was performed before CEA in the bilateral cerebral hemispheres of 84 patients with unilateral internal carotid artery stenosis (> or =70%) and without contralateral internal carotid artery steno-occlusive disease. Brain temperature was calculated from the chemical shift difference between water and N-acetylaspartate signals at proton MR spectroscopy. Cerebral blood flow (CBF) was also measured by using single photon emission computed tomography and N-isopropyl-p-[(123)I]-iodoamphetamine before and immediately after CEA and on the 3rd postoperative day. The relationship between each variable and the development of post-CEA hyperperfusion (CBF increase > or = 100% compared with preoperative values) was evaluated with univariate statistical analysis followed by multivariate analysis. RESULTS A linear correlation was observed between preoperative brain temperature difference (the value in the affected hemisphere minus the value in the contralateral hemisphere) and increases in CBF immediately after CEA (r = 0.763 and P < .001) when the preoperative brain temperature difference was greater than 0. Cerebral hyperperfusion immediately after CEA was observed in nine patients (11%). Elevated preoperative brain temperature difference was the only significant independent predictor of post-CEA hyperperfusion. When elevated brain temperature difference was defined as a marker of hemodynamic impairment in the affected cerebral hemisphere, use of preoperative brain temperature difference resulted in 100% sensitivity and 87% specificity, with a 47% positive predictive value and a 100% negative predictive value for the prediction of post-CEA hyperperfusion. Hyperperfusion syndrome developed on the 3rd and 4th postoperative days in two of the nine patients who exhibited hyperperfusion immediately after CEA. CONCLUSION Brain temperature measured by using preoperative proton MR spectroscopy may help identify patients at risk for post-CEA cerebral hyperperfusion.

Acute Intracranial Hypertension due to Occlusion of the Brachiocephalic Vein in a Patient Undergoing Hemodialysis

Introduction Stenoses and occlusions of central veins may occur after repeated or prolonged catheterization for hemodialysis access [1–3] . If the draining vein of a functioning shunt is obstructed, extreme venous hypertension can develop and result in pain, incapacitating swelling, and venous stasis ulcers of the arm, chest, neck and face on the ipsilateral side [4, 5] . A few reports have suggested that intracranial venous hypertension may also occur in the context of peripheral venous obstruction [6, 7] . We report a case of acute intracranial hypertension due to occlusion of the brachiocephalic vein in a patient undergoing hemodialysis. Case Report A 62-year-old woman, who had undergone ongoing hemodialysis for 9 years via a left arm arteriovenous fi stula, presented with dyspnea and was admitted to a local hospital. Physical and radiological examinations demonstrated pulmonary edema due to volume overload, presumably related to underdialysis. Venography was performed via the left arteriovenous fi stula from the left subclavian artery and showed stenosis of the left brachiocephalic vein. The patient underwent percutaneous angioplasty and stenting through the right femoral vein without diffi culty. On the day following percutaneous angioplasty and stenting for stenosis of the left brachiocephalic vein, the patient underwent hemodialysis uneventfully. Blood chemistries before hemodialysis showed elevations in urea nitrogen (64.0 mg/dl) and creatinine (6.8 mg/dl). Following dialysis, these values decreased to the normal range (urea nitrogen of 10.2 mg/dl and creatinine of 0.4 mg/dl). Serum sodium and calcium were within normal limits both before and after hemodialysis. Hypotension did not occur during the procedure. However, on the second postoperative day, the patient experienced abrupt onset of headache and generalized seizures. Systemic blood pressure measured at this time was 200/105 mm Hg. The patient was transferred to our Department for further evaluation and care. On admission, the patient was confused. Systemic blood pressure was 180/100 mm Hg, and physical examination was notable for the absence of dilated veins on the chest, neck or face. Blood chemistry revealed a slightly elevated serum creatinine of 1.2 mg/dl. Computed tomography and magnetic resonance imaging showed no abnormal fi nding. Venography of the left arteriovenous fi stula via the left subclavian artery demonstrated occlusion of the left brachiocephalic vein and refl ux of the left brachial

1H-magnetic resonance spectroscopy indicates damage to cerebral white matter in the subacute phase after CO poisoning

Objective The authors examined whether 1H-magnetic resonance spectroscopy (MRS) can identify damage to the centrum semiovale in the subacute phase after CO exposure. Methods Subjects comprised 29 adult patients who were treated with hyperbaric oxygenation within a range of 4–95 h (mean 18.7 h) after CO exposure. Subjects were classified into three groups according to clinical behaviours: Group A, patients with transit acute symptoms only; Group P, patients with persistent neurological symptoms; and Group D, patients with ‘delayed neuropsychiatric sequelae’ occurring after a lucid interval. MRS of bilateral centrum semiovale was performed 2 weeks after CO inhalation for all patients and 13 healthy volunteers. The mean ratios of choline-containing compounds/creatine (meanCho/Cr) and N-acetylaspartate/Cr (meanNAA/Cr) for bilateral centrum semiovale were calculated and compared between the three CO groups and controls. Myelin basic protein (MBP) concentration in cerebrospinal fluid was examined at 2 weeks to evaluate the degree of demyelination in patients. Results MBP concentration was abnormal for almost all patients in Groups P and D, but was not abnormal for any Group A patients. The meanCho/Cr ratios were significantly higher in Groups P and D than in Group A. No significant difference in meanNAA/Cr ratio was seen between the three pathological groups and controls. A significant correlation was identified between MBP and meanCho/Cr ratio. Conclusions These results suggest that the Cho/Cr ratio in the subacute phase after CO intoxication represents early demyelination in the centrum semiovale, and can predict chronic neurological symptoms.

Primary granulomatous angiitis of the central nervous system: findings of magnetic resonance spectroscopy and fractional anisotropy in diffusion tensor imaging prior to surgery. Case report.

Primary granulomatous angiitis of the central nervous system (CNS) is extremely rare. Its preoperative diagnosis is difficult as the condition displays nonspecific features on routine neuroimaging investigations. In this paper, the authors report findings of magnetic resonance (MR) spectroscopy and fractional anisotropy (FA) with diffusion tensor MR imaging in a case of granulomatous angiitis of the CNS. A 30-year-old man presented with morning headaches and grand mal seizures. An MR image revealed a mass resembling glioblastoma in the right temporal lobe. Magnetic resonance spectroscopy showed a high choline/creatine (Cho/Cr) ratio indicative of a malignant neoplasm, accompanied by a slight elevation of glutamate and glutamine. The FA value was very low, which is inconsistent with malignant glioma. The mass was totally removed surgically. Histologically, the peripheral lesion of the mass consisted of a rough accumulation of fat granule cells, infiltration of inflammatory cells, and distribution of capillary vessels. Some vessels within the lesion were replaced by granulomas. The histological diagnosis was granulomatous angiitis of the CNS. The MIB-1-positive rate of the granuloma was approximately 5%. Both MR spectroscopy and FA were unable to accurately diagnose granulomatous angiitis of the CNS prior to surgery; however, elevated Cho/Cr and glutamate and glutamine shown by MR spectroscopy may indicate the moderate proliferation potential of the granuloma and the inflammatory process, respectively, in this condition. Although the low FA value in the present case enabled the authors to rule out a diagnosis of glioblastoma, FA values in inflammatory lesions require careful interpretation.

Preoperative imaging of superficially located glioma resection using short inversion-time inversion recovery images in high-field magnetic resonance imaging

OBJECTIVES Short inversion-time inversion recovery (STIR) is the only magnetic resonance imaging (MRI) sequence able to produce high contrast images of both brain-CSF and gray matter-white matter in the central nervous system. The aim of the present study is to evaluate the effectiveness of STIR in imaging tumor involvement of the cortical surface and intra-axial structures, its usefulness in the resection of superficially located gliomas. PATIENTS AND METHODS In this study, we perform conventional MRI (1.5 T) and STIR (3.0 T) before surgery in 10 patients with superficially located glioma. We estimate the spatial relationship between the tumor bulk, the adjacent cortical surface and intra-axial structures on T2WI (1.5 T) and STIR (3.0 T). STIR findings are applied to resection of the tumor in each case. RESULTS For all patients, STIR provided more satisfactory images than T2WI of both the cortical surface structures and intra-axial structures surrounding the tumor. During surgery, the clear demonstration of cortical surface structures on preoperative STIR images assisted in determining tumor location and the sulci to be split for the trans-sulcal approach for patients whose cortex was normal in colour. Clear contrast on STIR between the tumor margin and peritumoral edema was useful for tumor resection. CONCLUSION STIR is able to demonstrate anatomical details of the cortical surface and intra-axial structures of the brain and is therefore suitable for the preoperative evaluation of superficially located gliomas.