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1.
Article in English | MEDLINE | ID: mdl-38781486

ABSTRACT

BACKGROUND AND IMPORTANCE: A double-layer micromesh stent is designed for the treatment of carotid artery stenosis that has been reported to potentially provide a flow diversion effect. However, the actual flow diversion effect of stents remains unclear. Here, we present a case of a growing saphenous vein graft (SVG) aneurysm treated with the placement of the double-layer micromesh stent using its flow diversion effect. CLINICAL PRESENTATION: A 66-year-old woman, who underwent high-flow bypass using a SVG for a blister-like internal carotid artery aneurysm 13 years earlier at our institute, was referred to our hospital with a pulsatile cervical mass. Magnetic resonance angiography showed a 9-mm aneurysm on the left SVG, although the aneurysm was a small pouch 4 years earlier. Digital subtracted angiography demonstrated a 9.4 × 8.3-mm aneurysm from the SVG at the auricular level. Because the diameter of the graft was larger than that of the available flow diverter stents in Japan, we decided to place the double-layer micromesh stent (CASPER RX, 7 × 25 mm MicroVention) using its flow diversion effect. Computational fluid dynamics analysis before and after stent deployment showed a significant reduction in the average flow velocity and wall shear stress in the aneurysm, indicating actual flow diversion. An angiogram 2 months postoperatively showed complete obliteration of the aneurysm. CONCLUSION: Obliteration of the saphenous vein aneurysm was achieved because of the flow diversion effect of the double-layer micromesh stent. The stents might be a feasible alternative for treating cervical carotid aneurysms.

2.
Article in English | MEDLINE | ID: mdl-38789122

ABSTRACT

BACKGROUND AND PURPOSE: Quantitative susceptibility mapping has been proposed to assess intraplaque hemorrhage (IPH) in the carotid artery. The purpose of this study was to compare the diagnostic accuracy of preoperative quantitative susceptibility mapping with that of the conventional T1-weighed 3D-FSE sequence for detecting IPH in cervical ICA stenosis in patients undergoing carotid endarterectomy by using histology as the reference standard. MATERIALS AND METHODS: Carotid T1-weighted 3D-FSE and QSM images were obtained from 16 patients with cervical ICA stenosis before carotid endarterectomy. Relative signal intensity and susceptibility of the ICA were measured on 3 axial images, including the location of most severe stenosis on T1-weighted 3D-FSE and quantitative susceptibility mapping images, respectively. Three transverse sections of carotid plaques excised by carotid endarterectomy, which corresponded with images on MR imaging, were stained with H&E, antibody against glycophorin A, and Prussian blue, and the relative area of histologic IPH was calculated. RESULTS: The correlation coefficient was significantly greater between susceptibility and relative area-histologic IPH (ρ = 0.691) than between relative signal intensity and relative area-histologic IPH (ρ = 0.413; P = .0259). The areas under the receiver operating characteristic curves for detecting histologic sections consisting primarily of IPH (relative area-histologic IPH > 40.7%) tended to be greater for susceptibility (0.964) than for T1WI FSE-relative signal intensity (0.811). Marginal homogeneity was observed between susceptibility and histologic sections consisting primarily of IPH (P = .0412), but not between T1-weighted FSE-relative signal intensity and histologic sections consisting primarily of IPH (P = .1824). CONCLUSIONS: Pre-carotid endarterectomy quantitative susceptibility mapping detects histologic IPH in cervical ICA stenosis more accurately than preoperative T1-weighted 3D-FSE imaging.

3.
Cerebrovasc Dis ; 2024 Feb 02.
Article in English | MEDLINE | ID: mdl-38310866

ABSTRACT

INTRODUCTION: While patients who experience improved cognition following carotid endarterectomy (CEA) typically demonstrate restored brain perfusion after the procedure, it is worth noting that less than 50% of patients in whom postoperative cerebral blood flow (CBF) restoration is achieved actually show improved cognition after postoperatively. This suggests that factors beyond the mere restoration of CBF may play a role in postoperative cognitive improvement. Increased iron deposition in the cerebral cortex may cause neural damage, and quantitative susceptibility mapping (QSM) obtained using magnetic resonance imaging (MRI) quantifies magnetic susceptibility in the cerebral cortex, allowing for the assessment of iron deposition in vivo. The purpose of the present study was to determine whether preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA. METHODS: Brain MRI with a three-dimensional gradient echo sequence was preoperatively performed in 53 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), and QSM with brain surface correction and vein removal was obtained. Cortical magnetic susceptibility was measured in the cerebral hemisphere ipsilateral to surgery on QSM. Preoperatively and at two months after the surgery, brain perfusion single-photon emission computed tomography (SPECT) and neuropsychological assessments were conducted. Using these collected data, we evaluated alterations in CBF within the affected hemisphere and assessed cognitive improvements following the operation. RESULTS: A logistic regression analysis showed that a postoperative greater increase in CBF (95% confidence interval [CI], 1.06-1.90; p = 0.0186) and preoperative lower cortical magnetic susceptibility (95% CI, 0.03-0.74; p = 0.0201) were significantly associated with postoperatively improved cognition. Although sensitivity, specificity, and positive- and negative-predictive values with the cutoff value lying closest to the upper left corner of a receiver operating characteristic curve for the prediction of postoperatively improved cognition did not differ between postoperative changes in CBF and preoperative cortical magnetic susceptibility, the specificity and the positive-predictive value were significantly greater for the combination of postoperative changes in CBF and preoperative cortical magnetic susceptibility (specificity, 95% CI, 93-100%; positive-predictive value 95% CI, 68-100%) than for the former parameter alone (specificity, 95% CI, 63-88%; positive-predictive value 95% CI, 20-64%). CONCLUSION: Preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA.

4.
J Phys Ther Sci ; 35(12): 777-782, 2023 Dec.
Article in English | MEDLINE | ID: mdl-38075518

ABSTRACT

[Purpose] Ankle foot orthosis (AFO) is widely used to regain gait function after injuries and/or stroke; however, limited information is currently available on their effects. We herein examined the effects of three-hour immobilization with AFO on corticospinal excitability and ankle joint movement during gait in healthy volunteers. [Participants and Methods] The participants comprised of seven healthy volunteers. Corticospinal excitability and ankle joint excursions were evaluated before and after three hours of immobilization with left limb AFO. We measured motor evoked potentials in the tibialis anterior (TA) and gastrocnemius (Ga) muscles induced by transcranial magnetic stimulation. In a kinematic analysis, we focused on transition points, such as the timing from dorsiflexion to plantarflexion of the ankle joint and/or vice versa, during gait. [Results] Corticospinal excitability in TA and Ga both significantly decreased. During the normalized gait cycle (GC), ankle angles showed less dorsiflexion at 0% GC and 100% GC, and during loading response and mid-swing and terminal swing phases. Furthermore, less plantarflexion was observed during the initial swing phase. [Conclusion] This study showed that short-term ankle joint immobilization with AFO induces a significant decrease in corticospinal excitability and has an effect on ankle joint excursion during gait. Further studies are needed on the effects of long-term immobilization by AFO.

5.
Neuroreport ; 34(12): 624-628, 2023 08 02.
Article in English | MEDLINE | ID: mdl-37395207

ABSTRACT

We aimed to investigate the effect of dual-task interference between cognitive and obstacle avoidance walking tasks, and the effect of transcranial direct current stimulation (tDCS) on the performance of this cognitive-motor dual task. The healthy young subjects participated in a single task consisting of a three-digit subtraction task (e.g. 783 - 7) or a 15-m track with six 7.5-cm high obstacles. Then, the subjects performed two single tasks simultaneously as dual tasks, before and after sham and anodal tDCS (2 mA, 20 min) to left dorsolateral prefrontal cortex (DLPFC, the F3 region of the 10/20 electroencephalogram electrode placement system). The effect of tDCS on each outcome (number of correct answers, the clearance height above the obstacle, and foot placement position) was analyzed using repeated-measures analysis of variance. Model effects included tDCS (real, sham), time (pre-, post-tDCS), and task (single task, dual task) conditions. A significant difference in the tDCS, time, and task conditions was observed; the correct number of subtraction tasks increased, and the clearance height and the distance between the obstacle and foot decreased in front of the obstacle. Our findings suggest that dual task performance is causally related to left DLPFC activation under complicated walking tasks and tDCS over this cortical area increases overloaded its information processing capacity.


Subject(s)
Transcranial Direct Current Stimulation , Humans , Dorsolateral Prefrontal Cortex , Prefrontal Cortex/physiology , Cognition/physiology , Gait
6.
Brain Sci ; 13(2)2023 Jan 28.
Article in English | MEDLINE | ID: mdl-36831760

ABSTRACT

BACKGROUND: While type 2 diabetes (T2D) is a major risk for ischemic stroke, the associated vessel wall characteristics remain essentially unknown. This study aimed to clarify intracranial vascular changes on three-dimensional vessel wall imaging (3D-VWI) using fast spin echo by employing 7Tesla (7T) magnetic resonance imaging (MRI) in T2D patients without advanced atherosclerosis as compared to healthy controls. METHODS: In 48 T2D patients and 35 healthy controls, the prevalence of cerebral small vessel diseases and intracranial plaques were evaluated by 3D-VWI with 7T MRI. RESULTS: The prevalence rate of lacunar infarction was significantly higher in T2D than in controls (n = 8 in T2D vs. n = 0 in control, p = 0.011). The mean number of intracranial plaques in both anterior and posterior circulation of each subject was significantly larger in T2D than in controls (2.23 in T2D vs. 0.94 in control, p < 0.01). In T2D patients, gender was associated with the presence of intracranial plaques. CONCLUSION: This is the first study to demonstrate the high prevalence of intracranial plaque in T2D patients with neither confirmed atherosclerotic disease nor symptoms by performing intracranial 3D-VWI employing 7TMRI. Investigation of intracranial VWI with 7T MRI is expected to provide novel insights allowing early intensive risk management for prevention of ischemic stroke in T2D patients.

7.
Magn Reson Med Sci ; 2022 Nov 30.
Article in English | MEDLINE | ID: mdl-36450525

ABSTRACT

Flip angle (FA) measurements using the actual flip angle imaging (AFI) method may induce significant errors in ultrahigh fields. We aimed to develop a method for detecting errors in FA measurements using phase information at 7 tesla. We performed computer simulations to elucidate the relationship between the FA calculation errors and the phase difference between the two AFI source images. We then examined whether a method based on the phase difference could detect FA calculation errors and determine the prescribed nominal FA of the scanner for accurate measurements in phantoms and healthy volunteers. The simulations confirmed that the calculated FA values erroneously decreased when the longitudinal magnetization and phase in one of the source images were inverted. Tests on phantoms and human subjects demonstrated that the phase difference information between the source images with a cut-off of 90° could readily detect FA calculation errors in the AFI method.

8.
Exp Brain Res ; 240(2): 421-428, 2022 Feb.
Article in English | MEDLINE | ID: mdl-34775531

ABSTRACT

Lack of attention to obstacles on the floor or walking path may cause trip and fall accidents. The preparatory activity in the motor cortex to the perturbation associated with obstacle avoidance movements with cognitive task is still unclear. The purpose of this study was to investigate the motor cortical activity involved in the preparation and execution of concurrent obstacle avoidance movement and cognitive task. Twenty young adults were required to step over obstacles that were projected on the floor while performing a cognitive task. The electroencephalogram was recorded, and the movement-related cortical potentials (MRCP) aligned by foot dorsiflexion were evaluated. There was no significant difference in the number of contacts between the toe and the obstacle between the obstacle avoidance task and obstacle avoidance with cognitive task; however, the distance between the toe and the obstacle just before obstacle avoidance movement was significantly extended in the latter task. The amplitude and the onset of MRCP during the dual task were decreased and delayed, respectively, compared with the simple obstacle avoidance movement task. These results suggest that the young participants changed their clearance strategy to stepping over the obstacle during the concurrent motor and cognitive dual task to reduce motor cortical activity.


Subject(s)
Movement , Walking , Cognition , Electroencephalography , Evoked Potentials , Gait , Humans , Young Adult
9.
J Stroke Cerebrovasc Dis ; 30(12): 106107, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34562793

ABSTRACT

BACKGROUND: The severity of chronic cerebral ischemia can be assessed using cerebrovascular reactivity (CVR) to acetazolamide (ACZ) challenge, which is measured by single-photon emission computed tomography (SPECT); however, this is an invasive method. We investigated whether intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) can assess impaired CVR in preoperative patients with chronic cerebral ischemia and compared it to SPECT-CVR. METHODS: Forty-seven patients with unilateral cervical carotid artery stenosis underwent diffusion-weighted MRI with 11 b-values in the range of 0-800 s/mm2 and cerebral perfusion SPECT with the ACZ challenge. The perfusion fraction (f) and diffusion coefficient (D) of the IVIM parameters were calculated using a bi-exponential model. The f and D values and these ratios of the ipsilateral middle cerebral artery territory against the contralateral side were compared with the CVR values of the affected side calculated from the SPECT data. RESULTS: The IVIM-f and D values in the affected side were significantly higher than those in the unaffected side (median: 7.74% vs. 7.45%, p = 0.027; 0.816 vs. 0.801 10-3mm2/s, p < 0.001; respectively). However, there were no significant correlations between the f or D values and SPECT-CVR values in the affected side. In contrast, the f ratio showed a moderate negative correlation with the SPECT-CVR values (r = -0.40, p = 0.006) and detected impaired CVR (< 18.4%) with a sensitivity/specificity of 0.71/0.90. CONCLUSION: The IVIM perfusion parameter, f, can noninvasively assess impaired CVR with high sensitivity and specificity in patients with unilateral cervical carotid artery stenosis.


Subject(s)
Brain Ischemia , Brain Ischemia/diagnostic imaging , Brain Ischemia/physiopathology , Humans , Magnetic Resonance Imaging , Motion
10.
Am J Phys Anthropol ; 174(4): 839-845, 2021 04.
Article in English | MEDLINE | ID: mdl-33438763

ABSTRACT

OBJECTIVES: Nasal passages adjust the temperature of inhaled air to reach the required body temperature for the lungs. The nasal regions of primates including humans are believed to have experienced anatomical modifications that are adaptive to effective conditioning of the atmospheric air in the habitat for a given species. Measurements of the nasal temperature are required to understand the air-conditioning performance for a given species. Unfortunately, repeated direct measurements within the nasal passage have been technically precluded in most nonhuman primates. MATERIALS AND METHODS: Computational fluid dynamics (CFD) simulation is a potential approach for examining the temperature profile in the nasal passage without any direct measurements. The CFD simulation model mainly comprises a computational model to simulate physiological mechanisms and a wall model to simulate the nasal passage's anatomical and physical properties. We used a computational model developed for humans and examined corrections for the developed wall model based on human properties for predicting its performance in Japanese macaques. RESULTS: This study confirmed that the epithelium layer thickness of the wall model affects the accuracy of the predictions for macaques. A convenient correction of the thickness based on body mass allows us to simulate the actual air temperature profile in macaques' nasal passage. DISCUSSION: The CFD simulations of the wall model corrected with body mass can be applied to other nonhuman primates and mammals. This convenient corrective approach allows us to examine the functional contributions of a specific morphology to the air-conditioning performance without any direct measurements to improve our understanding of primates' functional morphology and physical adaptations to the temperature environment in their habitat.


Subject(s)
Computer Simulation , Nasal Cavity/physiology , Temperature , Air Movements , Animals , Female , Humans , Hydrodynamics , Macaca fuscata , Nasal Cavity/diagnostic imaging , Tomography, X-Ray Computed
12.
JGH Open ; 4(5): 958-963, 2020 Oct.
Article in English | MEDLINE | ID: mdl-33102770

ABSTRACT

BACKGROUND AND AIM: We evaluated whether diffusion kurtosis and tensor imaging (DKI/DTI) could reveal microstructural alterations in the brains of patients with functional gastrointestinal disorders (FGIDs), and whether imaging findings were correlated with health-related quality of life (HRQOL). METHODS: Twelve patients with FGIDs fulfilling the Rome IV criteria, and seven healthy controls were examined using a 3 T magnetic resonance (MR) scanner. Tract-based spatial statistics and regions of interest analyses were performed to compare the mean kurtosis (MK), fractional anisotropy (FA), and mean diffusivity (MD) between patients with FGIDs versus controls. HRQOL was assessed in patients with FGIDs using the eight-item short form of the Medical Outcome Study Questionnaire (SF-8) and the Gastrointestinal Symptom Rating Scale. RESULTS: Patients with FGIDs had extensive, widespread regions of reduced MD in the white matter in comparison with healthy controls, whereas no significant differences were observed in MK and FA. No significant differences in deep gray matter for the MK, FA, and MD values were observed between patients with FGIDs and controls. In patients with FGIDs, the FA values in the globus pallidus had a significant and negative correlation with SF-8 (a mental component summary) (r = -0.797, P = 0.01 uncorrected for multiple comparisons). CONCLUSIONS: DKI/DTI can help identify microstructural white matter alterations in patients with FGIDs. The FA values in the globus pallidus may be useful for a severity assessment of FGIDs.

13.
J Stroke Cerebrovasc Dis ; 29(9): 105081, 2020 Sep.
Article in English | MEDLINE | ID: mdl-32807478

ABSTRACT

BACKGROUND: Cerebrovascular reactivity (CVR) to acetazolamide (ACZ) on single-photon emission computed tomography (SPECT) can be used to assess the severity of chronic cerebral ischemia; however, this is an invasive method. We examined whether whole-brain magnetic resonance angiography (MRA) at 7T could non-invasively detect impaired CVR in patients with chronic cerebral ischemia by demonstrating the leptomeningeal collaterals (LMCs). METHODS: Fifty-seven patients with symptomatic unilateral cervical stenosis underwent whole-brain time-of-flight MRA at 7T and cerebral perfusion SPECT before/after the ACZ challenge. MRA images were visually assessed based on 6-point grading systems to evaluate the development of LMCs toward the middle cerebral artery (MCA) and antegrade flow of MCA. CVR of the affected side was calculated from the SPECT data. Subsequently, we compared the LMC grades on MRA with CVR on SPECT. RESULTS: CVR was significantly lower in grades ≥ 2 of LMCs than in grades 0-1 (P < 0.05) when applying LMCs from the anterior cerebral artery (ACA) and/or posterior cerebral artery (PCA). These differences were more evident than those in the grading of the antegrade MCA flow. The LMC grades from ACA/PCA readily detected reduced CVR (< 18.4%) with a sensitivity/specificity of 0.79/0.82. CONCLUSION: The development of LMCs on whole-brain MRA at 7T can non-invasively detect reduced CVR with a high sensitivity/specificity in patients with unilateral cervical stenosis.


Subject(s)
Cerebral Angiography/methods , Cerebrovascular Circulation , Collateral Circulation , Magnetic Resonance Angiography , Meninges/blood supply , Middle Cerebral Artery/diagnostic imaging , Vertebrobasilar Insufficiency/diagnostic imaging , Aged , Aged, 80 and over , Chronic Disease , Feasibility Studies , Female , Humans , Male , Middle Aged , Middle Cerebral Artery/physiopathology , Perfusion Imaging , Predictive Value of Tests , Prospective Studies , Reproducibility of Results , Severity of Illness Index , Tomography, Emission-Computed, Single-Photon , Vertebrobasilar Insufficiency/physiopathology
14.
Neuroreport ; 31(3): 251-255, 2020 02 05.
Article in English | MEDLINE | ID: mdl-31923024

ABSTRACT

In stroke patients, muscle tone on the unaffected side is often increased during voluntary tasks. This is known as a mirror movement and might be an impediment to function recovery, but its neural background is still unclear. In this study, we investigated the effect of unilateral muscle hypertonia on ipsilateral cortical activity and contralateral motor function. Fourteen right-handed healthy young subjects lifted a weight of 10% body weight with the right upper limb to increase muscle tone (weight task), while no weight lifting was set as the control 'nonweight' task. We recorded the motor-evoked potential (MEP), resting motor threshold and H-reflex from the left flexor carpi radialis muscle during both tasks. To estimate the functional effect of the weight task, subjects performed the 'Purdue pegboard test', consisting of examination for 30 seconds (peg-30) and assembly for 60 seconds (peg assembly). Left-hand grip strength was also measured. When subjects performed the weight task, the MEP amplitude increased significantly and the MT decreased significantly. There was no significant difference of H-reflex amplitude between the two tasks. No significant difference of the peg-30 score was observed between weight and nonweight tasks, but the peg assembly score was significantly lower during the weight task. Grip strength showed a significant increase during the weight task. These results indicate that the present weight load model may have the potential to advance our understanding of the mechanisms underlying mirror movements after stroke.


Subject(s)
Evoked Potentials, Motor/physiology , Muscle Hypertonia/physiopathology , Muscle Tonus/physiology , Stroke/physiopathology , Adult , Female , Hand Strength/physiology , Healthy Volunteers , Humans , Male , Motor Skills/physiology , Muscle, Skeletal/physiology , Transcranial Magnetic Stimulation
15.
J Stroke Cerebrovasc Dis ; 28(11): 104339, 2019 Nov.
Article in English | MEDLINE | ID: mdl-31451338

ABSTRACT

BACKGROUND: Infarcts in the lateral striate artery (LSA) territory can be caused by several pathological changes, including lipohyalinosis and microatheroma. However, fluid dynamic effects on these changes remain unknown. Thus, we investigated whether the fluid dynamic metrics of the LSAs were altered in patients with acute ischemic stroke using computational fluid dynamics (CFD) analysis. METHODS: Fifty-one patients with acute ischemic stroke confined in the basal ganglia and/or corona radiata underwent high-resolution magnetic resonance angiography (HR-MRA) at 7T. We performed CFD analyses to obtain indices including the wall shear stress (WSS), WSS gradient (WSSG), and flow velocity (FV) and compared these values between the ipsilesional and contralesional sides in the patients with infarcts in the LSA or non-LSA territories. RESULTS: In patients with LSA-territory infarcts, the WSS, WSSG, and FV values were significantly lower in the ipsilesional LSAs than in the contralesional LSAs (P = .01-.03), while these values in the proximal middle cerebral arteries showed no significant lateralities. In contrast, in patients with non-LSA-territory infarcts, there were no significant lateralities in the metrics between the ipsilesional and contralesional sides. CONCLUSIONS: The CFD analyses using HR-MRA revealed significantly low WSS and WSSG values of the ipsilesional LSAs compared with that of the contralesional side in patients with LSA-territory infarcts, suggesting that fluid dynamic factors of LSAs can be one of the risk factors for LSA-territory infarctions.


Subject(s)
Brain Ischemia/diagnostic imaging , Cerebral Angiography/methods , Cerebral Arteries/diagnostic imaging , Cerebrovascular Circulation , Magnetic Resonance Angiography , Models, Cardiovascular , Patient-Specific Modeling , Stroke/diagnostic imaging , Adult , Aged , Aged, 80 and over , Blood Flow Velocity , Brain Ischemia/physiopathology , Cerebral Arteries/physiopathology , Female , Humans , Male , Middle Aged , Predictive Value of Tests , Prospective Studies , Stress, Mechanical , Stroke/physiopathology
16.
J Neurophysiol ; 122(1): 398-412, 2019 07 01.
Article in English | MEDLINE | ID: mdl-31116630

ABSTRACT

Several qualitative features distinguish bipedal from quadrupedal locomotion in mammals. In this study we show quantitative differences between quadrupedal and bipedal gait in the Japanese monkey in terms of gait patterns, trunk/hindlimb kinematics, and electromyographic (EMG) activity, obtained from 3 macaques during treadmill walking. We predicted that as a consequence of an almost upright body axis, bipedal gait would show properties consistent with temporal and spatial optimization countering higher trunk/hindlimb loads and a less stable center of mass (CoM). A comparatively larger step width, an ~9% longer duty cycle, and ~20% increased relative duration of the double-support phase were all in line with such a strategy. Bipedal joint kinematics showed the strongest differences in proximal, and least in distal, hindlimb joint excursions compared with quadrupedal gait. Hindlimb joint coordination (cyclograms) revealed more periods of single-joint rotations during bipedal gait and predominance of proximal joints during single support. The CoM described a symmetrical, quasi-sinusoidal left/right path during bipedal gait, with an alternating shift toward the weight-supporting limb during stance. Trunk/hindlimb EMG activity was nonuniformally increased during bipedal gait, most prominently in proximal antigravity muscles during stance (up to 10-fold). Non-antigravity hindlimb EMG showed altered temporal profiles during liftoff or touchdown. Muscle coactivation was more, but muscle synergies less, frequent during bipedal gait. Together, these results show that behavioral and EMG properties of bipedal vs. quadrupedal gait are quantitatively distinct and suggest that the neural control of bipedal primate locomotion underwent specific adaptations to generate these particular behavioral features to counteract increased load and instability. NEW & NOTEWORTHY Bipedal locomotion imposes particular biomechanical constraints on motor control. In a within-species comparative study, we investigated joint kinematics and electromyographic characteristics of bipedal vs. quadrupedal treadmill locomotion in Japanese macaques. Because these features represent (to a large extent) emergent properties of the underlying neural control, they provide a comparative, behavioral, and neurophysiological framework for understanding the neural system dedicated to bipedal locomotion in this nonhuman primate, which constitutes a critical animal model for human bipedalism.


Subject(s)
Extremities/physiology , Gait , Muscle Contraction , Postural Balance , Animals , Biomechanical Phenomena , Extremities/innervation , Female , Macaca fuscata , Male , Muscle, Skeletal/innervation , Muscle, Skeletal/physiology
17.
Acad Radiol ; 26(11): e333-e339, 2019 11.
Article in English | MEDLINE | ID: mdl-30658931

ABSTRACT

RATIONALE AND OBJECTIVE: Differentiation between multiple system atrophy (MSA) and other spinocerebellar degenerations showing cerebellar ataxia is often difficult. Hence, we investigated whether magnetic resonance diffusion kurtosis imaging (DKI) could detect pathological changes that occur in these patients and be used for differential diagnosis. METHODS: Thirty-six subjects (12 patients with MSA accompanied by predominant cerebellar ataxia [MSA-C], 10 patients with spinocerebellar ataxias [SCAs] or sporadic adult-onset ataxia of unknown etiology [SAOA], and 14 healthy controls) were examined using 1.5- or 3-T magnetic resonance scanners. From the DKI data, the mean kurtosis, fractional anisotropy, and mean diffusivity values of the pontine crossing tract (PCT), middle cerebellar peduncle, and cerebellum were automatically measured, and the ratios against the values of the corpus callosum were calculated. RESULTS: We found significant decreases in mean kurtosis and fractional anisotropy ratios in the PCT and middle cerebellar peduncle, and a significant increase in the mean diffusivity ratio in the PCT in the MSA-C group, as compared with the SCA/SAOA and control groups (p < 0.027-0.001). Among these metrics, there were no significant differences in the diagnostic performance. By contrast, the ratios in the cerebellum showed no significant differences between the MSA-C and SCA/SAOA groups but were significantly altered when compared with the controls (p < 0.001). CONCLUSION: Quantitative DKI analyses can be used to differentiate between patients with MSA-C and those with SCA/SAOA.


Subject(s)
Cerebellum/pathology , Diffusion Magnetic Resonance Imaging/methods , Image Processing, Computer-Assisted/methods , Multiple System Atrophy/diagnosis , Spinocerebellar Degenerations/diagnosis , Adult , Aged , Aged, 80 and over , Diagnosis, Differential , Female , Humans , Male , Middle Aged
19.
Stroke ; 49(9): 2061-2066, 2018 09.
Article in English | MEDLINE | ID: mdl-30354998

ABSTRACT

Background and Purpose- The frictional force because of blood flow may dislodge masses present on the surface of a plaque. Such frictional force is calculated as wall shear stress (WSS) using computational fluid dynamics. The aims of the present study were to determine whether, in addition to carotid plaque intensity on T1-weighted magnetic resonance (MR) imaging, WSS calculated using computational fluid dynamics analysis for carotid arteries is associated with development of an embolism during exposure of carotid arteries during carotid endarterectomy. Methods- One hundred patients with internal carotid artery stenosis (≥70%) underwent carotid plaque imaging with MR, and 54 patients with a vulnerable plaque (intraplaque hemorrhage or lipid/necrotic core) displayed as a high-intensity lesion underwent additional cervical 3-dimensional MR angiography. The maximum value of WSS within the most severe stenotic segment of the internal carotid artery was calculated using MR angiography. Transcranial Doppler monitoring of microembolic signals (MES) in the ipsilateral middle cerebral artery was performed during carotid endarterectomy. Results- Although none of the 46 patients with a nonvulnerable carotid plaque had MES during exposure of carotid arteries, 24 of the 54 patients with a vulnerable carotid plaque (44%) had MES. Logistic regression analysis showed that higher plaque intensity ( P=0.0107) and higher WSS ( P=0.0029) were significantly associated with the development of MES. When both cutoff points of plaque intensity and WSS in the receiver operating characteristic curves for predicting development of MES were combined, specificity (from 63% to 93%) and positive predictive value (from 66% to 90%) became greater than those for plaque intensity alone. Conclusions- In addition to carotid plaque intensity on T1-weighted MR imaging, WSS calculated using computational fluid dynamics analysis for carotid arteries is associated with development of an embolism during exposure of carotid arteries during carotid endarterectomy.


Subject(s)
Carotid Artery, Internal/surgery , Carotid Stenosis/surgery , Endarterectomy, Carotid , Intracranial Embolism/diagnostic imaging , Middle Cerebral Artery/diagnostic imaging , Plaque, Atherosclerotic/surgery , Stress, Mechanical , Aged , Aged, 80 and over , Carotid Artery, Internal/diagnostic imaging , Carotid Stenosis/diagnostic imaging , Female , Humans , Intraoperative Care , Magnetic Resonance Imaging , Male , Middle Aged , Plaque, Atherosclerotic/diagnostic imaging , Prospective Studies , ROC Curve , Ultrasonography, Doppler, Transcranial
20.
Neuroreport ; 28(16): 1092-1096, 2017 Nov 08.
Article in English | MEDLINE | ID: mdl-28906346

ABSTRACT

The short-term joint immobilization induces a decrease of corticospinal excitability; however, detailed time course of the immobilization-induced central nervous system changes and their extent have not yet been clarified. To evaluate the time course of changes in corticospinal excitability during forearm/hand immobilization for 24 h and investigate the effect on muscle strength, adhesive casting tape was used to immobilize the nondominant forearm/hand. The amplitude of the motor-evoked potential of the flexor pollicis brevis muscle induced by transcranial magnetic stimulation was measured during immobilization and after cast removal. The muscle strength was evaluated after the termination of immobilization. The resting motor-evoked potential recorded from flexor pollicis brevis muscle showed a significant decrease 3 h after initiation of immobilization and gradually declined further until the end of immobilization. It then increased over 2 h after cast removal, but was still significantly below baseline. However, no significant difference from baseline was observed at 3 h. Both pinch power and integrated electromyogram were significantly reduced by immobilization, and then gradually returned to baseline after the cast was removed. These results indicate that short-term forearm/hand immobilization rapidly reduces corticospinal excitability, and this change is rapidly reversed after resumption of movement.


Subject(s)
Evoked Potentials, Motor/physiology , Forearm/physiology , Hand/physiology , Immobilization/physiology , Muscle Strength/physiology , Muscle, Skeletal/physiology , Pyramidal Tracts/physiology , Adult , Electromyography , Female , Humans , Male , Time Factors , Transcranial Magnetic Stimulation , Young Adult
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