Showing papers on "Neural tract published in 2012"

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

Abstract: 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.

Spinal Cord: Connections

Abstract: Connections of the spinal cord have been studied extensively in experimental animals, mostly in the rat, cat, and monkey These studies are based on electrophysiological and anatomical tract tracing methods In humans, our direct knowledge of spinal cord tracts is mostly based on data obtained from patients with localized traumatic and inflammatory lesions, or surgical interventions, which have resulted in ascending fiber degeneration or retrograde changes in spinal cells of origin Sensory-evoked potentials in the human spinal cord can be safely recorded from the epidural space Evaluation of the discharge rate and probability of one or more motor units in response to stimulation of peripheral afferents or corticospinal fibers has also been used to study functional connection of neurons in humans Recent development of diffusion tensor tractography allows visualization and localization of neural tracts in three dimensions and provides helpful and important information for clinicians This information allows clinicians to evaluate the state of a neural tract to predict clinical outcomes, or to set up scientific management strategies for patients with brain injury This chapter deals with propriospinal, ascending, and descending pathways of the human spinal cord We refer to the rat, cat, and monkey data where there is no or limited information for humans

Neural connection between injured cingulum and pedunculopontine nucleus in a patient with traumatic brain injury.

Abstract: We report on a patient with traumatic brain injury who showed neural connection between injured cingulum and pedunculopontine nucleus on diffusion tensor tractography (DTT). A 74-year-old male who had suffered a traffic accident underwent conservative management for subarachnoid haemorrhage. Brain MRI which was performed 6 months after onset showed no specific lesions. On 6-month DTTs for cingulum of the patient, we observed discontinuations of both cingulums above the genu of corpus callosum. However, the left cingulum was connected to the left PPN via a neural tract that passed through the anterior corona radiata and thalamus. The neural connection between the injured cingulum and PPN seems to be a compensatory phenomenon for the destruction of cholinergic pathways from basal forebrain. We believe that this result might suggest one of recovery mechanisms of injured cingulum following brain injury.

Neural tract injuries by brain herniations after head trauma.

Abstract: OBJECTIVES : Little is known about the usefulness and findings of brain herniation on diffusion tensor tractography (DTT). Using DTT, we demonstrated neural tract injuries in 2 patients who showed subfalcine and trasntentorial herniations after subdural hematoma resulting from motor vehicle accident. DESIGN : Two patients and 6 age- and sex-matched, healthy volunteers were recruited for this study. SETTING : An inpatient rehabilitation unit. MAIN OUTCOME MEASURES : Diffusion tensor tractography for the patients was performed 5 weeks after onset. RESULTS : Diffusion tensor tractography of patient 1 showed complete injury of both cingulums at or around the rostrum of the corpus callosum, the fornix at the anterior and posterior body, and both corticospinal tracts at the pons. In addition, partial injury of both somatosensory tracts at the midbrain was also observed. Patient 2 showed complete injury of both cingulums above the body of the corpus callosum, the fornix at the anterior and posterior body, and right corticospinal tracts at the pons level and partial injury of the right somatosensory tract. We found that the fractional anisotropy values of all neural tracts, except fornix, in both patients and left somatosensory tract in patient 2 and voxel number for left somatosensory tract in patient 2 were decreased 2 SDs below that of normal controls. CONCLUSIONS : We determined that DTT would be a good technique for use in the detection of underlying lesions in patients with brain herniation.

Fasciculography: Robust Prior-Free Real-Time Normalized Volumetric Neural Tract Parcellation

Abstract: Fiber tracking in diffusion tensor magnetic resonance images (DTIs) reveals 3-D structural connectivity of the brain conveniently and thus is a viable tool for investigating neural differences. Unfortunately, local noise, image artifacts and numerical tracking errors during integration-based techniques are cumulative. Prematurely terminated fibers and under-sampled fiber bundles result in incomplete reconstruction of white matter fiber tracts and hence incorrect anatomical measurements. Quantitative cross-subject tract analysis, which is critical for abnormality detection, is complicated by inefficient and inaccurate tract reconstruction and normalization from fiber bundles. Because of the above problems, we propose a parcellation method that aims for lower sensitivity to initialization and local orientation error by directly segmenting full white matter tracts (Fasciculography), rather than reconstructing individual curves, from diffusion tensor fields. A fast, robust volumetric, and intrinsically normalized solution is achieved by noise-filtering using a generic parametrized tract model to prevent premature tract termination. At the same time, orientation information reduces the search space, significantly speeding up the tract parcellation process with less human intervention. Detailed comparisons against streamline tracking, shortest-path tracking, and nonrigid registration using synthetic and real DTIs confirmed the superior properties of Fasciculography. Since a normalized tract can be delineated interactively in a just few seconds using the proposed method, accurate high volume tract comparisons become feasible.