The somatotopic localisation of the descending cortical tract in the cerebral peduncle: a study using MRI of changes following Wallerian degeneration in the cerebral peduncle after a supratentorial vascular lesion

We studied the effects of Wallerian degeneration in the cerebral peduncle shown by magnetic resonance imaging (MRI) following a supratentorial vascular lesion, to identify the somatotopic localisation of the descending cortical tracts. Patients with a lesion involving a large area of a cerebral hemisphere had an area of abnormal signal intensity in the whole cerebral peduncle, suggesting Wallerian degeneration of all the whole descending cortical tracts. With a small lesion confined to the precentral gyrus, corona radiata, or posterior limb of the internal capsule there was an abnormal signal at the centre of the peduncle, suggesting degeneration of the precentrospinal tract. Those with a small lesion confined to the paracentral gyrus had an abnormal area slightly lateral to the centre of the peduncle, suggesting degeneration of the parietospinal tract. Patients with a lesion of the parietal or temporal lobes, not including the paracentral or precentral gyri, corona radiata, or the posterior limb of the internal capsule, had an abnormal area laterally in the peduncle, suggesting degeneration of the parietopontine or temporopontine tract.     

MR images of wallerian degeneration--relation between the time and MR findings of wallerian degeneration

On magnetic resonance (MR) images, wallerian degeneration of the pyramidal tract can be demonstrated as an abnormal intensity showing prolonged T1 and T2 relaxation times corresponding to the corticospinal tract, and/or as shrinkage of the ipsilateral cerebral peduncle and pons. We evaluated 150 cases with supratentorial cerebrovascular accident (CVA) and found the above findings in 35 patients (hematoma 21, infarction 14). The time interval between the ictus of CVA and manifestation of wallerian degeneration on MR images was evaluated. In all 35 cases the foci of CVA located at or extended into the motor cortex, the corona radiata of the pyramidal tract or the posterior limb of the internal capsule. Abnormal signal intensity appeared as early as 5 weeks after ictus and was observed in all 17 cases after 10 weeks. Ipsilateral shrinkage of the cerebral peduncle and the pons has appeared 13 months after ictus. MR appears to be the most useful modality for early detection of waller degeneration.     

Clinical experience with Tc-99m HM-PAO high resolution SPECT of the brain in patients with cerebrovascular accidents

In order to evaluate the diagnostic contribution of brain SPECT imaging with ^99mTc-HMPAO in cerebrovascular disease, we examined 92 stroke cases (144 lesions), 2 hematoma cases and 30 cases with transient neurologic symptoms. Abnormal tracer distribution is visible as zones of either hypoactivity or hyperactivity (border zone hyperemia or luxury perfusion). Remote vascularization changes could also be found (crossed cerebellar diaschisis or ipsilateral cortical perfusion reduction in thalamic or capsula interna lesions). Both X-ray CT and blood flow SPECT have comparable sensitivity in the exploration of cerebral infarction, with detection in, respectively, 89.5% and 87.5% of the lesions. False negative scintitomographic images are frequently recorded in small lacunar infarcts within the basal ganglia and white matter (capsula interna). Some early infarcts and asymmetry of brain perfusion in patients with transient neurologic symptoms are frequently not detected by CT. An additional advantage of blood flow SPECT is its ability to visualize remote blood flow changes and the changing pattern of vascularization of ischemic lesions and their surrounding areas including hyperemia.     

Effects of chemotherapy on the brain in childhood: diffusion tensor imaging of subtle white matter damage

Introduction

With reducing mortality in children with hematological malignancies, the survivors' quality of life regarding development of chronic neurological disturbances is important. We aimed to determine whether chemotherapy affects white matter (WM).

Methods

Using brain diffusion tensor imaging, we evaluated 17 patients (15 with acute lymphoblastic leukemia, 2 with non-Hodgkin's lymphoma; 9 male, 8 female; age, 1.6–13 years) before and after chemotherapy. We measured the quantitative values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) at the regions of interest (ROIs) such as periventricular WM, corona radiata, posterior limb of the internal capsule, and corpus callosum. We assessed sensorimotor and callosal tracts by tractography.

Results

Reduction in FA and increase in ADC were significant at the ROIs of the left and right anterior periventricular WM and corona radiata and at the tract passing through the genu. A significant reduction in FA with a nonsignificant increase in ADC was seen at the ROI of the genu and at the tracts passing through the body and isthmus.

Conclusion

Chemotherapy in children with hematological malignancies predominantly affects the frontal WM. This finding might indicate a negative effect of chemotherapy on neurological development in children with hematological malignancies.     

The cranial computed tomographic findings in patients with pure sensory stroke

We reported three patients compatible with the clinical syndrome of pure sensory stroke (PSS). The computed tomography (CT) scan suggested the lesions responsible for the deficits were posterior thalamus, corona radiata, and parietal lobe. PSS could conceivably arise anywhere along the sensory systems and CT scan is reliable method for discussing the lesion responsible for PSS.     

Diffusion anisotropy of the internal capsule and the corona radiata in association with stroke and tumors as measured by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: Diffusion-weighted MR images have enabled measurement of directionality of diffusion (anisotropy) in white matter. To investigate differences in the anisotropy for various types of pathologic findings and the association between the anisotropy of tracts and neurologic dysfunction, we compared the anisotropy of the posterior limb of the internal capsule and the corona radiata between patients with stroke and those with tumors and between patients with and without hemiparesis. METHODS: Thirty-three patients consisting of 11 with tumors and 22 with ischemic disease (16 acute infarction, four old infarction, and two transient ischemic attack) and nine control patients were studied with a 1.5-T MR imager. Diffusion-weighted images were obtained with diffusion gradients applied in three orthogonal directions. The diffusion anisotropy measurements were obtained from regions of interests defined within the internal capsule and the corona radiata. RESULTS: The diffusion anisotropy was significantly reduced in all internal capsules and coronae radiata involved by infarcts, tumors, and peritumoral edema compared with that of the control patients (P <.0001). This reduction was most prominent in the tracts involved by tumors (P <.05). The anisotropy of the internal capsules and coronae radiata was significantly decreased in cases with moderate-to-severe hemiparesis as compared with those with no or mild hemiparesis (P <.0001). Diffusion anisotropy tended to be also reduced in normal-appearing internal capsules and coronae radiata that were remote from the involved segment of the corticospinal tract. CONCLUSION: The degree of impaired diffusion anisotropy may vary in different pathologic conditions and correlate with neurologic dysfunction. The measurement of diffusion anisotropy may provide additional information relating to neurologic function and transneuronal effects.     

CT-defined large subcortical infarcts: correlation of location with site of cerebrovascular occlusive disease.

PURPOSETo correlate the location of large subcortical infarcts with the site of cerebrovascular occlusive disease.METHODSWe examined CT and angiographic findings of 38 patients with major arterial occlusive disease and newly developed large subcortical infarcts of 2.0 cm or more, which were classified into three types: striatocapsular infarcts in the basal ganglia, terminal supply area infarcts in the corona radiata, and terminal supply area infarcts in the centrum semiovale.RESULTSTwo or three of the types of infarct were sometimes combined; the combination of the striatocapsular and corona radiata infarcts was the most frequent (14 [36.8%] of 38). Thirty-four (89.5%) had atherosclerotic major arterial occlusive diseases; 22 (57.9%) had occlusive diseases of the internal carotid artery, and 12 (31.6%) had diseases of the middle cerebral artery. The other 4 (10.5%) had embolic transient middle cerebral artery occlusion. Middle cerebral artery occlusive diseases frequently produced striatocapsular (13 [81.3%] of 16) and corona radiata (13 [81.3%] of 16) infarcts but never induced the centrum semiovale lesions. On the other hand, in patients with internal carotid artery occlusive disease, the centrum semiovale (16 [72.7%] of 22) was more susceptible to ischemia than the striatocapsular region (11 [50%] of 22) or the corona radiata (9 [40.9%] of 22).CONCLUSIONSMiddle cerebral artery occlusive diseases frequently produced striatocapsular and/or corona radiata infarcts but never induced the centrum semiovale lesions, which were usually associated with internal carotid artery occlusive diseases.     

Clinical experience with Tc-99m HM-PAO high resolution SPECT of the brain in patients with cerebrovascular accidents

In order to evaluate the diagnostic contribution of brain SPECT imaging with 99mTc-HMPAO in cerebrovascular disease, we examined 92 stroke cases (144 lesions), 2 hematoma cases and 30 cases with transient neurologic symptoms. Abnormal tracer distribution is visible as zones of either hypoactivity or hyperactivity (border zone hyperemia or luxury perfusion). Remote vascularization changes could also be found (crossed cerebellar diaschisis or ipsilateral cortical perfusion reduction in thalamic or capsula interna lesions). Both X-ray CT and blood flow SPECT have comparable sensitivity in the exploration of cerebral infarction, with detection in, respectively, 89.5% and 87.5% of the lesions. False negative scintitomographic images are frequently recorded in small lacunar infarcts within the basal ganglia and white matter (capsula interna). Some early infarcts and asymmetry of brain perfusion in patients with transient neurologic symptoms are frequently not detected by CT. An additional advantage of blood flow SPECT is its ability to visualize remote blood flow changes and the changing pattern of vascularization of ischemic lesions and their surrounding areas including hyperemia.     

Quantitative apparent diffusion coefficient measurements in term neonates for early detection of hypoxic-ischemic brain injury: initial experience

PURPOSE: To determine the utility of using quantitative apparent diffusion coefficient (ADC) values as an objective means of early detection of brain injury caused by hypoxic-ischemic encephalopathy (HIE) in term neonates. MATERIALS AND METHODS: Conventional images, diffusion-weighted images, ADC maps, and clinical charts from 13 term neonates clinically suspected of having HIE were retrospectively reviewed. Four term neonates without HIE served as control subjects. ADC values were calculated in predefined regions in patients and compared with those in control subjects. A Student t test was performed for each region to compare patients and control subjects. RESULTS: Abnormalities were more easily detected on diffusion-weighted images and ADC maps, compared with conventional images. ADC values in patients with HIE were significantly different from those of control subjects in the posterior limb of the internal capsule, corona radiata, posterior frontal white matter, and parietal white matter bilaterally. CONCLUSION: Evaluation of ADC maps can improve conspicuity of hypoxic-ischemic injury in the acute and/or subacute setting (within 12 days of insult), and calculation of ADC values can provide an objective measure of hypoxic-ischemic injury.     

DTI在涉及皮质脊髓束缺血性脑梗塞中的应用

目的:探讨磁共振弥散张量成像(DTI)在涉及皮质脊髓束的缺血性脑梗塞的应用价值。方法:应用西门子1.5TMR成像系统,对30例累及内囊后肢或放射冠的脑梗塞患者进行检查,均行DTI序列(b值=0,500s/mm2)及颅脑MRI扫描,在Siemens Leonardo工作站应用纤维束跟踪软件(Siemens Standar 12 dirs)进行后处理。结果:梗塞灶FA值较对侧相应部位明显降低,ADC值较对侧相应部位明显升高,皮质脊髓束穿过梗塞灶的患者运动功能恢复较差,皮质脊髓束未穿过梗塞灶的患者运动功能恢复较好。结论:DTI白质纤维束成像可以无创性显示皮质脊髓束与缺血性梗塞灶的空间关系,帮助判断运动功能受损情况与预测预后。     

MR assessment of myelination in infants and children: usefulness of marker sites

A retrospective study was made of 60 patients, 1 month to 3 years old, to determine the normal progression of white matter myelination on MR imaging. All examinations were performed with a 1.5-T unit, and axial T1- and T2-weighted images were evaluated in each patient. Multiple sites in the cerebral hemisphere and cerebellum were examined in each case for the presence and degree of myelination. The results show that MR imaging is sensitive to the early changes of white matter myelination, and imaging patterns correlate with known patterns from pathologic studies. At the time of birth in a full-term infant the posterior limb of the internal capsule, central corona radiata, and cerebellar peduncles show visible myelination. Myelination in the centrum semiovale then proceeds anteriorly and posteriorly. Both T1- and T2-weighted images show these changes, which are best explained by a decrease in the water content of white matter as myelination progresses. Knowledge of these normal myelination patterns is essential in evaluating MR imaging studies in infants and children and in diagnosing delayed myelination.     

In vivo MR study of brain maturation in normal fetuses.

PURPOSETo illustrate normal maturation of the fetal brain, including the migrational layer, gray matter, early myelination of internal capsules, optic radiations, and corona radiata.METHODSSeventy-seven fetal brains, ranging from 21 to 38 weeks of gestational age, were examined with MR in vivo; 33 were considered normal. MR examinations were performed as T1-weighted sequences in the axial, sagittal, and coronal planes. The neuropathologic examination (four cases) and clinical and/or neuroradiologic examinations confirmed the antenatal data.RESULTSFrom 21 to 25 weeks, the cerebral ventricles are large, corresponding to the relative fetal hydrocephalus. A slight high signal intensity can be observed in the basal ganglia as early as 21 weeks. In the cerebral hemispheres, a multilayered pattern that can be observed from 23 to 28 weeks includes the cortical ribbon, the germinal matrix, and an intermediate layer corresponding to the migrating glial cells. These findings are probably related to areas of increased cellularity. A high signal intensity can be seen within the dorsal part of the brain stem as early as 23 weeks, within the posterior limb of the internal capsules at 31 weeks, and within the central area of the cerebral hemispheres at 35 weeks. Those patterns are probably caused by the evolving process of myelination.CONCLUSIONSMR allows depiction of signal changes corresponding either to an increase in cellularity or to the evolving processes of myelination, depending on the stage of the pregnancy.     

Posterior alien hand syndrome: case report

The alien hand syndrome (AHS) is involuntary uncontrolled movement of an arm with a sense of estrangement from the limb itself. AHS was initially used to describe interhemispheric disconnection phenomena in patients with lesions in the anterior corpus callosum, but it has been found in patients with posterior cerebral lesions without involvement of the corpus callosum, for example parietal infarcts or corticobasal degeneration. The posterior alien hand syndrome is less frequent and presents with nonpurposive behaviour like lifting the arm or writhing fingers. We report an 80-year-old woman with a posterior AHS of the dominant right hand. MRI showed atrophy of the pre- and postcentral gyri without involvement of the corpus callosum. We discuss the aetiology of the posterior AHS and the differences from the anterior varieties.     

High intensity areas on noncontrast T1-weighted MR images in cerebral infarction

Among 46 noncontrast magnetic resonance studies on patients with cerebral infarction, 11 showed areas of high signal intensity of the involved brain on T1-weighted images. These areas were more frequent in cerebral or cerebellar cortical lesions. Lacunar infarcts in lenticular nuclei, internal capsules, corona radiata, or brain stem did not show any high signal intensity areas on T1-weighted images, whereas the thalamic infarcts did. Sequential studies revealed that these lesions displayed low signal intensity on T2-weighted images at first, and then a high signal intensity area appeared on T1-weighted images. We suggest that these high signal intensity areas on the T1-weighted images in cerebral infarction are caused by hemorrhagic changes at the periphery of the infarction, where blood flow is restored by recanalization or collateral supply.     

Evaluation of diseased coronary arterial branches by polar representations of thallium-201 rotational myocardial imaging

The perfusion territories in polar representations of stress Tl-201 rotational myocardial imaging in patients with angina pectoris who had one diseased coronary segment were analyzed. The lesions proximal or distal to the first major septal perforator in left anterior descending arteries were detected by the presence or absence of defects at the base of the anterior septum. Right coronary artery lesions were detected by the presence of defects at the basal posterior septum, in contrast to the preservation of myocardial uptake at this portion in lesions of the left circumflex artery. The specific defect patterns were detected in cases with lesions at the first diagonal, obtuse marginal, and posterolateral branches. Recognition of these defects in the polar maps allows detailed detection of diseased coronary arterial branches.     

Three-dimensional white matter tractography by diffusion tensor imaging in ischaemic stroke involving the corticospinal tract

Diffusion tensor MR imaging (DTI) provides information on diffusion anisotropy, which can be expressed with three-dimensional (3D) white matter tractography. We used 3D white matter tractography to show the corticospinal tract in eight patients with acute or early subacute ischaemic stroke involving the posterior limb of the internal capsule or corona radiata and to assess involvement of the tract. Infarcts and the tract were shown simultaneously, providing information on their spatial relationships. In five of the eight patients, 3D fibre tract maps showed the corticospinal tract in close proximity to the infarct but not to pass through it. All these patients recovered well, with maximum improvement from the lowest score on manual muscle testing (MMT) up to the full score through rehabilitation. In the other three patients the corticospinal tract was shown running through the infarct; reduction in MMT did not necessarily improve favourably or last longer, other than in one patient. As 3D white matter tractography can show spatial relationships between the corticospinal tract and an infarct, it might be helpful in prognosis of gross motor function.     

Correlation of cognitive dysfunction and diffusion tensor MRI measures in patients with mild and moderate multiple sclerosis

Purpose

To compare the diffusion tensor imaging (DTI) measures of multiple sclerosis (MS) patients and healthy subjects in every brain voxel and to correlate them with Paced Auditory Serial Addition Test (PASAT) scores.

Materials and Methods

Fractional anisotropy (FA), and mean, longitudinal, and transverse diffusivity are compared between control subjects and MS patients, which were subdivided as mildly and moderately impaired. In addition, PASAT scores are correlated for both MS groups with the diffusion measures. An optimized voxel based analysis (VBA) method, in terms of coregistration, atlas construction, and image smoothing, was thereby used.

Results:

Diffusion differences between the control subjects and the patients with MS were found in the corpus callosum, inferior longitudinal fasciculus, cortico spinal tracts, forceps major, superior longitudinal fasciculus, and cingulum. In addition, we observed significant correlations of the FA and PASAT scores in the left inferior longitudinal fasciculus, the forceps minor, the capsula interna and externa, the genu of the corpus callosum, the left cingulum, the superior longitudinal fasciculus, and the corona radiata.

Conclusion:

Diffusion differences were observed between the mildly impaired MS patients and control subjects. In addition, different diffusion measures correlated with PASAT scores for cognitive decline in parietal, frontal, as well as temporal white matter (WM) regions. J. Magn. Reson. Imaging 2010;31:1492–1498. © 2010 Wiley‐Liss, Inc.     

The anterior inferior cerebellar artery in mass lesions. Preliminary findings with emphasis on the lateral projection.

Analysis of abnormalities of the configuration of the anterior inferior cerebellar artery in lateral projection facilitates diagnosis of posterior fossa masses. Cerebellopontomedullary angle lesions frequently cause arcuate posterior-inferior displacements of the rostrolateral artery or reversal of curvature of the ascending segment of the meatal loop. Vermian, hemispheric, intra-fourth ventricular, and suitably situated extra-axial masses alter the plane of the lateral loop of the caudomedial artery. Tonsillar herniation may be detected in patients with hypoplastic or absent posterior inferior cerebellar arteries by analyzing the relationship of the biventral segment of the descending or caudomedial artery to the foramen magnum.     

Maple syrup urine disease: diffusion-weighted MRI findings during acute metabolic encephalopathic crisis

Maple syrup urine disease (MSUD) is caused by a genetic defect of branched-chain amino acids, which include leucine, isoleucine and valine. We report diffusion-weighted imaging (DWI) findings in a newborn child with MSUD who presented with acute metabolic encephalopathic crisis. DWI (b = 1,000 s/mm(2)) showed high signal localized within the myelinated white matter (WM) areas including the cerebellar white matter, pons, bulbus, cerebral peduncles, lentiform nucleus, posterior limbs of the internal capsules, corona radiata and bilateral perirolandic cortex. The apparent diffusion coefficient values of these regions were markedly low in the affected areas. The presence of these findings was considered cytotoxic or intramyelinic edema evidenced by restricted water diffusion. In conclusion, our findings suggest that during the acute phase and early encephalopathic crisis stage of MSUD, DWI can demonstrate the involvement of myelinated WM in newborns.     

MR signal intensity of the perirolandic cortex in the neonate and infant

Our purpose was to study the magnetic resonance (MR) signal intensity of the perirolandic gyri perinatally and to correlate it with the histological findings in formalinfixed brains, focusing on myelination. MRI of 20 neurologically normal neonates and infants, of 37–64 weeks postconception (PCA), were studied retrospectively. We reviewed four formalin-fixed brains of infants 37–46 weeks PCA microscopically. The posterior cortex of the precentral gyrus (P-PRE) and the anterior cortex of the postcentral gyrus (A-PST) had different signal intensity from the adjacent surrounding cortex. On T1-weighted images P-PRE and A-PST gave higher signal 41–44 weeks PCA; on T2-weighted images, they gave lower signal 37–51 weeks PCA. Histological examination revealed very little myelination of the nerve fibres within both the P-PRE and the A-PST, while considerable myelination was present in the internal capsule and central corona radiata. The changes in signal intensity in the perirolandic gyri may reflect not only the degree of myelination but also the more advanced development of the nerve cells, associated with rapid proliferation and formation of oligodendroglial cells, synapses and dendrites. They could be another important landmark for brain maturation.