Ipsilateral motor pathway without contralateral motor pathway in a stroke patient

The ipsilateral motor pathway from the unaffected motor cortex to the affected extremity is one of the mechanisms of motor recovery following stroke. We report on a stroke patient who showed the ipsilateral motor pathway without the contralateral motor pathway on functional MRI and diffusion tensor tractography. A 53-year-old left hemiparetic patient with an infarct in the right middle cerebral artery territory was evaluated. During a period of three months after onset, motor function of the affected (left) hand had recovered slowly, to the extent that the patient was able to overcome gravity. FMRI showed that only the unaffected (left) primary sensorimotor cortex was activated by movements of the unaffected (right) hand or of the affected (left) hand. On diffusion tensor tractography, the corticospinal tract of the left hemisphere originated from the primary sensori-motor cortex and descended through the known corticospinal tract pathway. By contrast, the right corticospinal tract showed a disruption with Wallerian degeneration to the upper medulla. We conclude that the motor function of the affected (left) hand appeared to be controlled only by the ipsilateral motor pathway from the left motor cortex to the left hand. Motor function of the affected hand appeared to have been reorganized to the ipsilateral motor pathway from the unaffected motor cortex to the affected hand.     

Transcallosal motor pathway from affected motor cortex to affected hand in a patient with corona radiata infarct A diffusion tensor tractography and transcranial magnetic stimulation study

The mechanisms of motor recovery through the transcallosal pathway remain poorly understood.The present study reports on a hemiplegic patient with corona radiata infarct; it attempts to confirm motor recovery through the transcallosal motor pathway, from the affected motor cortex to the affected hand, using diffusion tensor tractography and transcranial magnetic stimulation. A 54-year-old, male patient and eight age-matched, normal subjects were enrolled in the study. The patient's right hand was initially completely paralyzed, but slowly recovered over 6 months. In the control subjects and the unaffected hemisphere (right) of the patient, the corticospinal tracts originated from the motor cortex and descended along the known corticospinal tract pathway.However, the corticospinal tract of the affected hemisphere was disrupted at the upper pons.Following transcranial stimulation of the affected (left) motor cortex, motor evoked potential from the affected (right) abductor pollicis brevis muscle exhibited longer latency than opposite motor evoked potential. Results from the present study suggest that motor function of the affected (right) hand recovered via the transcallosal motor pathway from the affected (left) motor cortex in this patient.     

Cortical reorganization demonstrated by diffusion tensor tractography analyzed using functional MRI activation

The diffusion tensor tractography (DTT) allows the corticospinal tract(CST) to be visualized at the subcortical level and functional MRI (fMRI) is capable of precisely identifying activation sites at the cortex. Therefore, it seems that combined DTT/fMRI would allow more accurate evaluation of the state of the CST. We have attempted to demonstrate cortical reorganization in a patient with cortical hemorrhage using DTT analyzed by fMRI activations. Six normal subjects and a 12-year-old female patient with a hemorrhage in the left fronto-parietal cortex were recruited. fMRI was performed at 1.5-T with timed hand grasp-release movements, and DTT was performed using 1.5-T with a Synergy-L Sensitivity Encoding head coil. Three-dimensional reconstructions of the fiber tracts were obtained using the fMRI activation as the seed region of interest and the CST area of the anterior pons as the target region of interest. The tract of the affected hemisphere originated from the lateral area of the injured precentral knob and descended along the known corticospinal tract pathway. It seems that the motor function of the affected hand was reorganized into the lateral area of the injured precentral knob. Therefore, these combined modalities would be helpful in elucidating the state of the CST.     

Recovery of the corticospinal tract after injury by transtentorial herniation: a case report

Little is known about recovery of the corticospinal tract (CST) after injury by transtentorial herniation (TH). We present with a patient who showed recovery of the CST after injury by TH, using diffusion tensor tractography (DTT) and transcranial magnetic stimulation (TMS). A 69-year-old female underwent craniotomy and drainage of an intracerebral hemorrhage in the left corona radiata and basal ganglia. Brain CT showed left TH and brain MRI revealed a leukomalactic lesion at the left cerebral peduncle. The patient presented with complete paralysis of the right extremities at ICH onset, but slowly recovered some function to the point of being able to move the affected extremities against gravity at about 6 months after onset. Three-week DTT showed disruption of the left CST below the cerebral peduncle; however, this disruption was recovered on 1-year DTT. Three-week TMS showed no motor evoked potential for the affected hemisphere; in contrast, motor evoked potentials that were compatible with regenerated CST were obtained from the affected hand muscle at 6 months. Using DTT and TMS in a patient with ICH, we demonstrated recovery of the CST after injury by TH.     

Prognostic factors for motor outcome in patients with compressed corticospinal tract by intracerebral hematoma

Little is known about prognostic factors associated with motor outcome when the corticospinal tract (CST) was compressed by hematoma. Using diffusion tensor tractography (DTT), we attempted to investigate prognostic factors for motor outcome in patients whose affected CST was compressed by hematoma. The study included 51 consecutive severe hemiparetic patients with a hematoma involving the corona radiata and basal ganglia. Integrities of the affected CSTs were preserved to the cerebral cortex and were found to be compressed by a hematoma on DTT. Patients were classified into four groups according to the region which the CST was originated from the precentral gyrus (type A), postcentral gyrus (type B), posterior parietal cortex (type C), and premotor cortex (type D). We measured the ratios of DTT parameters between affected/unaffected hemispheres.The motor function of the affected extremities at 6-month after onset was better with the following order: DTT type A, type B, type C, and type D patients. The 6-month motor function for DTT type A patients was higher than that of DTT type D patients (p=0.008). The fractional anisotropy ratio between the affected and unaffected CST was positively correlated with the 6-month motor function of the affected extremities (Pearson's correlation coefficient, p=0.025, r=0.313). We found that motor outcome differed according to the originated area of the affected CST and the degree of injury of the affected CST in patients whose affected CST was compressed by hematoma.     

Interhemispheric reorganization of motor hand function to the primary motor cortex predicted with functional magnetic resonance imaging and transcranial magnetic stimulation

The objective of this study was presurgical assessment of reorganization of motor hand function in an 11-year-old girl with intractable epilepsy and a right-sided hemiplegia resulting from an extensive perinatal left hemispheric stroke. Prior to a left functional hemispherectomy, functional magnetic resonance imaging (MRI) showed that both nonparetic and paretic motor hand function predominantly activated the right primary motor cortex, whereas no activation was found in the left hemisphere. Transcranial magnetic stimulation of the right central area yielded responses in both the nonparetic and the paretic hand, whereas no responses were obtained after stimulation of the affected hemisphere. Both techniques indicated that motor function was mediated by corticospinal fibers originating from the undamaged (primary) motor cortex and predicted no further loss of motor hand function after surgery. Indeed, subsequent functional hemispherectomy induced no new sensorimotor deficits. Functional MRI was repeated 22 months after surgery and matched preoperative sensorimotor functional MRI findings, confirming reorganization of the primary motor cortex. No additional reorganization was introduced by surgery.     

Limb apraxia in a patient with cerebral infarct: diffusion tensor tractography study

We report on a patient with ideomotor apraxia (IMA) and limb-kinetic apraxia (LKA) following cerebral infarct, which demonstrated neural tract injuries by diffusion tensor tractography (DTT). A 67-year-old male was diagnosed as cerebral infarct in the left frontal cortex (anterior portion of the precentral gyrus and prefrontal cortex) and centrum semiovale. The patient presented with severe paralysis of the right upper extremity and mild weakness of the right lower extremity at onset. At the time of DTT scanning (5 months after onset), the patient was able to move all joint muscles of the right upper extremity against gravity, except for the finger extensors, which he could extend partially against gravity. The patient showed intact ideational plan for motor performance; however, his movements were slow, clumsy, and mutilated when executing grasp-release movements of his affected hand. The patient's score on the ideomotor apraxia test was 20 (cut-off score < 32). DTTs for premotor cortex fibers, supplementary motor area fibers, and superior longitudinal fasciculus of the left hemisphere showed partial injuries, compared with those of the right side, and these injuries appeared to be responsible for IMA and LKA in this patient.     

Is one motor cortex enough for two hands?

We report on a patient with mirror movements sustained by a mono‐hemispheric fast control of bilateral hand muscles and normal hand function. Transcranial magnetic stimulation of the right motor cortex evoked contractions of muscles in both hands while no responses were observed from the left hemisphere. Somatosensory‐evoked potentials, functional magnetic resonance, and diffusion tractography showed evidence of sensorimotor dissociation and asymmetry of corticospinal projections, suggestive of reorganization after early unilateral left brain lesion. This is the first evidence that, in certain rare conditions, good hand function is possible with ipsilateral corticospinal reorganization, supporting the role of unexplored mechanisms of motor recovery.     

Patterns of Structural Reorganization of the Corticospinal Tract in Children With Sturge-Weber Syndrome

BackgroundReorganization of the corticospinal tract after early damage can limit motor deficit. In this study, we explored patterns of structural corticospinal tract reorganization in children with Sturge-Weber syndrome.MethodsFive children (age 1.5-7 years) with motor deficit resulting from unilateral Sturge-Weber syndrome were studied prospectively and longitudinally (1-2 years follow-up). Corticospinal tract segments belonging to hand and leg movements were separated and their volume was measured by diffusion tensor imaging tractography using a recently validated method. Corticospinal tract segmental volumes were normalized and compared between the Sturge-Weber syndrome children and age-matched healthy controls. Volume changes during follow-up were also compared with clinical motor symptoms.ResultsIn the Sturge-Weber syndrome children, hand-related (but not leg-related) corticospinal tract volumes were consistently decreased in the affected cerebral hemisphere at baseline. At follow-up, two distinct patterns of hand corticospinal tract volume changes emerged. (1) Two children with extensive frontal lobe damage showed a corticospinal tract volume decrease in the lesional hemisphere and a concomitant increase in the nonlesional (contralateral) hemisphere. These children developed good hand grasp but no fine motor skills. (2) The three other children, with relative sparing of the frontal lobe, showed an interval increase of the normalized hand corticospinal tract volume in the affected hemisphere; these children showed no gross motor deficit at follow-up.ConclusionsDiffusion tensor imaging tractography can detect differential abnormalities in the hand corticospinal tract segment both ipsi- and contralateral to the lesion. Interval increase in the corticospinal tract hand segment suggests structural reorganization, whose pattern may determine clinical motor outcome and could guide strategies for early motor intervention.     

Cortical Reorganization Allows for Motor Recovery after Crossed Cerebrocerebellar Atrophy

The authors report the case of a 33-year-old woman who exhibited, at the age of 17, a left-sided hemiplegia, which was followed by good motor recovery, though with a permanent deficit in fine finger movements. She had a widespread loss of neural tissue in the right hemisphere (crossed cerebrocerebellar atrophy), including (1) marked atrophy and thinning of the precentral and postcentral gyri; (2) widespread deep white matter destruction, including the corticospinal tract; and (3) crossed cerebellar atrophy. Except over the supplementary motor area (SMA), transcranial magnetic stimulation did not elicit motor evoked potentials in the affected hand. Nevertheless, during opening and closing of the affected hand, functional magnetic resonance imaging showed an activation of the lesioned primary sensorimotor cortex (SMC), as well as of the intact SMA and the parietal areas, but not of the ipsilateral motor areas. The authors speculate that recovery was achieved by a motor command generated in the SMC and the parietal cortex, passing through corticospinal axons originating in the SMA.     

弥散张量纤维束成像和经颅磁刺激显现脑出血患者独立的皮质脊髓束

Diffusion tensor tractography allows visualization of the corticospinal tract (CST) in three dimensions. Transcranial magnetic stimulation offers a unique advantage in that it can distinguish between the corticospinal tract and the non-CST by analyzing the characteristics of a motor-evoked potential. A 15 year-old female showed right hemiparesis, due to intracerebral hemorrhage in the left corona radiata, and the posterior limb of the internal capsule. Diffusion tensor tractography revealed that the tracts of both hemispheres originated from the precentral gyrus, and descended through the known CST pathway. Specifically, the tract of the affected hemisphere descended through an isolated area in the leukomalactic lesion at the posterior limb level. In addition, the characteristics of the motor-evoked potential obtained from the right hand when stimulating the hot spot of the left motor cortex corresponded to a CST. In conclusion, we report on a patient with intracerebral hemorrhage who showed an isolated CST in a leukomalactic lesion. This result suggests the importance of saving the adjacent area or penumbra around a hematoma after an intracerebral hemorrhage.     

Motor cortex activation is preserved in patients with chronic hemiplegic stroke

Many central nervous system conditions that cause weakness, including many strokes, injure corticospinal tract but leave motor cortex intact. Little is known about the functional properties of surviving cortical regions in this setting, in part because many studies have used probes reliant on the corticospinal tract. We hypothesized that many features of motor cortex function would be preserved when assessed independent of the stroke-affected corticospinal tract. Functional MRI was used to study 11 patients with chronic hemiplegia after unilateral stroke that spared regions of motor cortex. Activation in stroke-affected hemisphere was evaluated using 3 probes independent of affected corticospinal tract: passive finger movement, a hand-related visuomotor stimulus, and tapping by the nonstroke index finger. The site and magnitude of cortical activation were similar when comparing the stroke hemisphere to findings in 19 control subjects. Patients activated each of 8 cortical regions with similar frequency as compared to controls, generally with a smaller activation volume. In some cases, clinical measures correlated with the size or the site of stroke hemisphere activation. The results suggest that, despite stroke producing contralateral hemiplegia, surviving regions of motor cortex actively participate in the same proprioceptive, visuomotor, and bilateral movement control processes seen in control subjects.     

Motor recovery via aberrant pyramidal tract in a patient with a cerebral peduncle infarct*●

The presence of the aberrant pyramidal tract has been demonstrated by several studies;however,little is known about its role in motor recovery in stroke patients.In the present study,we reported a 69-year-old right-handed female patient with an infarct in the mid to lateral portion of the left cerebral peduncle,who showed an aberrant pyramidal tract by diffusion tensor tractography.The patient presented with severe weakness of the right extremities at stroke onset.The patient showed progressive motor recovery as much as being able to extend the affected extremities against some resistance at 6 months after onset.At 20 months after stroke onset,motor function of the left extremities had recovered to a nearly normal state.Diffusion tensor tractography results showed that the PT was disrupted at the lower midbrain of the affected(left) hemisphere at 3 weeks after stroke onset and this disruption was not changed at 20 months.An aberrant pyramidal tract in the left hemisphere was also observed,which originated from the primary motor cortex and descended through the corona radiata,posterior limb of the internal capsule,thalamus,the medial lemniscus pathway from the midbrain to the pons,and then entered into the pyramidal tract area at the pontomedullary junction.Transcranial magnetic stimulation did not elicit motor evoked potential from the affected hand muscle at 3 weeks,but it elicited motor evoked potential with mildly delayed latency and low amplitude in the affected hand muscle at 20 months.The main motor functions of the affected extremities in this patient appeared to be recovered via this aberrant pyramidal tract.     

Increases of corticospinal excitability in self-related processing

Involvement of fronto‐parietal structures within the right hemisphere in bodily self recognition has gained convergent support from behavioural, neuropsychological and neuroimaging studies. Increases in corticospinal excitability via transcranial magnetic stimulation (TMS) also testify to right hemisphere self‐related processing. However, evidence for self‐dependent modulations of motor excitability is limited to the processing of face‐related information that, by definition, conveys someone’s identity. Here we tested the hypothesis that vision of one’s own hand, as compared with vision of somebody else’s hand, would also engage specific self‐hand processing in the right hemisphere. Healthy participants were submitted to a classic TMS paradigm to assess changes in corticospinal excitability of the right (Experiment 1) and left (Experiment 2) motor cortex, while viewing pictures of a (contralateral) still hand, which could either be their own (Self) or not (Other). As a control for body selectivity, subjects were also presented with pictures of a hand‐related, but non‐corporeal object, i.e. a mobile phone, which could similarly be their own or not. Results showed a selective right hemisphere increase in corticospinal excitability with self‐hand and self‐phone stimuli with respect to Other stimuli. Such a Self vs. Other modulation of primary motor cortex appeared at 600 ms and was maintained at 900 ms, but was not present at earlier timings (100 and 300 ms) and was completely absent following stimulation of the left hemisphere. A similar pattern observed for self‐hand and self‐phone stimuli suggests that owned hands and objects may undergo similar self‐processing, possibly via a different cortical network from that responsible for self‐face processing.     

Motor cortex localization using functional MRI and transcranial magnetic stimulation.

OBJECTIVE: Congenital brain lesions producing focal seizures may be accompanied by reorganization of the areas responsible for motor and sensory functions within the brain due to a phenomenon that has been termed "neuronal plasticity." This can be studied using functional MRI (fMRI) and transcranial magnetic stimulation (TMS). Using either method, the motor cortex can be localized noninvasively, but to date there have been few studies correlating the level of agreement between the two techniques. METHODS: We used fMRI and TMS to localize the motor cortex in a young woman with intractable focal seizures, congenital left arm weakness, and a dysplastic right hemisphere on MRI. RESULTS: There was excellent agreement in the localization of motor representation for each hand. Both were predominantly located in the left hemisphere. fMRI also showed an area of posterior activation in the right hemisphere, but there was no evidence of descending corticospinal projections from this site using TMS, direct cortical stimulation, and Wada testing. CONCLUSIONS: Functional MRI (fMRI) and transcranial magnetic stimulation (TMS) were successfully used to localize cortical motor function before epilepsy surgery. Each technique demonstrated migration of motor function for the left hand to the left motor cortex. After resection of the dysplastic right precentral gyrus there was no permanent increase in weakness or disability. The two techniques are complementary; fMRI indicates all cortical areas activated by the motor task, whereas TMS identifies only those areas giving rise to corticospinal projections.     

延髓锥体梗死患者运动功能恢复与皮质脊髓束穿行于梗死延髓锥体的小块空余区

The present study reported a 58-year-old male patient who exhibited complete paralysis of the right extremities at stroke onset.Brain MR images showed an infarct in the left medullary pyramid and a small spared area on the medial side of the infarct.He gained the ability to extend the affected fingers against gravity and to dorsiflex the affected ankle without gravity at 3 months after stroke onset.Diffusion tensor imaging results showed that at 6 months after stroke onset,the corticospinal tract of the affected(left) hemisphere descended through the small spared area of the infarcted medullary pyramid.No motor-evoked potential was elicited from the affected(left) hemisphere at 2 weeks after stroke onset;however,motor-evoked potential was elicited at 6 months as shown by transcranial magnetic stimulation results.The motor function of the affected side of this patient appears to have been recovered via the corticospinal tract that passed through the small spared area within the infarcted medullary pyramid.     

Degeneration of corpus callosum and recovery of motor function after stroke: A multimodal magnetic resonance imaging study

Animal models of stroke demonstrated that white matter ischemia may cause both axonal damage and myelin degradation distant from the core lesion, thereby impacting on behavior and functional outcome after stroke. We here used parameters derived from diffusion magnetic resonance imaging (MRI) to investigate the effect of focal white matter ischemia on functional reorganization within the motor system. Patients (n = 18) suffering from hand motor deficits in the subacute or chronic stage after subcortical stroke and healthy controls (n = 12) were scanned with both diffusion MRI and functional MRI while performing a motor task with the left or right hand. A laterality index was employed on activated voxels to assess functional reorganization across hemispheres. Regression analyses revealed that diffusion MRI parameters of both the ipsilesional corticospinal tract (CST) and corpus callosum (CC) predicted increased activation of the unaffected hemisphere during movements of the stroke‐affected hand. Changes in diffusion MRI parameters possibly reflecting axonal damage and/or destruction of myelin sheath correlated with a stronger bilateral recruitment of motor areas and poorer motor performance. Probabilistic fiber tracking analyses revealed that the region in the CC correlating with the fMRI laterality index and motor deficits connected to sensorimotor cortex, supplementary motor area, ventral premotor cortex, superior parietal lobule, and temporoparietal junction. The results suggest that degeneration of transcallosal fibers connecting higher order sensorimotor regions constitute a relevant factor influencing cortical reorganization and motor outcome after subcortical stroke. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.     

Activation of less affected corticospinal tract and poor motor outcome in hemiplegic pediatric patients:a diffusion tensor tractography imaging study

The less affected hemisphere is important in motor recovery in mature brains.However,in terms of motor outcome in immature brains,no study has been reported on the less affected corticospinal tract in hemiplegic pediatric patients.Therefore,we examined the relationship between the condition of the less affected corticospinal tract and motor function in hemiplegic pediatric patients.Forty patients with hemiplegia due to perinatal or prenatal injury(13.7±3.0 months)and 40 age-matched typically developing controls were recruited.These patients were divided into two age-matched groups,the high functioning group(20 patients)and the low functioning group(20 patients)using functional level of hemiplegia scale.Diffusion tensor tractography images showed that compared with the control group,the patient group of the less affected corticospinal tract showed significantly increased fiber number and significantly decreased fractional anisotropy value.Significantly increased fiber number and significantly decreased fractional anisotropy value in the low functioning group were observed than in the high functioning group.These findings suggest that activation of the less affected hemisphere presenting as increased fiber number and decreased fractional anisotropy value is related to poor motor function in pediatric hemiplegic patients.     

Spared integrity of corticospinal tract within a pontine infarct A diffusion tensor tractography study

Integrity of the corticospinal tract is mandatory for good recovery of impaired motor function in patients who have suffered a stroke. A 67-year-old left hemiparetic female showed an infarct in the right pons. Three months after onset, motor function of the affected extremities recovered rapidly to a nearly complete state. Diffusion tensor tractography of both hemispheres showed that the corticospinal tract originated from the primary sensori-motor cortex and descended through the known corticospinal tract ...     

Réorganisation du cortex sensorimoteur dans le cadre de la paralysie cérébrale unilatérale : apports des neurosciences

Cerebral palsy (CP) is a non-progressive injury to the developing central nervous system and defines as permanent disorders of the development of movement and posture, causing activity limitation. This neurodevelopmental disorder may lead to spastic unilateral cerebral palsy after early unilateral brain lesions. Physical and rehabilitation medicine has a particular interest in the study of organization and reorganization of the sensorimotor cortex following early brain injury. From neuroscience standpoint, early brain lesions have been shown to induce substantial neural reorganization owing to the higher plasticity in the developing brain. Unilateral injuries either to the motor cortex or the corticospinal tract can lead to different patterns of reorganization of the sensorimotor cortex. Many patients develop ipsilateral corticospinal pathways to control the paretic hand with the non-lesioned hemisphere. This type of reorganization is often observed following unilateral periventricular brain lesions, which damage the corticospinal tracts in the periventricular white matter. In this group of patients, the primary motor cortex has been found to be represented in the non-lesioned precentral gyrus ipsilateral to the paretic side. Inversely, in patients with perinatal unilateral middle cerebral artery stroke, primary motor cortex remains organised in the lesioned precentral gyrus contralateral to the paretic hand. However, regardless of these inter- or intrahemispheric motor representations, the primary somatosensory cortex representation remains in the lesioned hemisphere in both groups. These two types of corticospinal reorganization could influence the efficacy of rehabilitation.