Hyeok Gyu Kwon

Mammillothalamic tract in human brain: Diffusion tensor tractography study

The mammillothalamic tract (MTT) is a part of the Papez circuit and connects the mammillary body and anterior thalamus. No studies of the MTT have been performed using diffusion tensor tractography (DTT). In the current study, we attempted to identify the MTT in the human brain using DTT. We recruited 25 healthy volunteers for this study. Diffusion tensor images (DTIs) were scanned using 1.5-T, and the MTT was obtained using FMRIB software. Values of fractional anisotropy (FA), mean diffusicity (MD), and tract volume of the MTT were measured. The location of the highest probability point of the MTT was measured at the bicommissural level. MTTs of all subjects, which originated from the mammillary body, ascended posteriorly to the bicommissural level, along the third ventricle, and then ascended to the anterior thalamus in the antero-lateral direction. Average location of the MTT was 37.15% from the most posterior border of the anterior commissure to the most posterior border of the third ventricle at the bicommissural level. We identified the MTT in the human brain using DTT. These methods and results would be helpful to both clinicians and researchers in this field.

The ascending reticular activating system from pontine reticular formation to the hypothalamus in the human brain: a diffusion tensor imaging study.

The ascending reticular activating system (ARAS) is responsible for regulation of consciousness. Precise evaluation of the ARAS is important for diagnosis and management of patients with impaired consciousness. In the current study, we attempted to reconstruct the portion of the ARAS from the pontine reticular formation (RF) to the hypothalamus in normal subjects, using diffusion tensor imaging (DTI). A total of 31 healthy subjects were recruited for this study. DTI scanning was performed using 1.5-T, and the ARAS from the pontine RF to the hypothalamus was reconstructed. Values of fractional anisotropy, mean diffusivity, and tract volume of the ARAS from the pontine RF to the hypothalamus were measured. In all subjects, the ARAS from the pontine RF to the hypothalamus originated from the RF at the level of the mid-pons, where the trigeminal nerve could be seen, ascended through the periaqueductal gray matter of the midbrain anterolaterally to the anterior commissure level, and then terminated into the hypothalamus. No significant differences in DTI parameters were observed between the left and right hemispheres and between males and females (p<0.05). We identified the ARAS between the pontine RF and the hypothalamus in normal subjects using DTI. We believe that the reconstruction methodology and the results of this study would be useful to clinicians involved in the care of patients with impaired consciousness and researchers in studies of the ARAS.

The relation between motor function of stroke patients and diffusion tensor imaging findings for the corticospinal tract

Although the corticospinal tract (CST) is a major neural tract for motor function, the detailed role of the CST has not been clearly elucidated. We investigated relations between motor function of patients with chronic hemiparetic stroke and diffusion tensor imaging (DTI) findings for the CST. We recruited 82 consecutive chronic stroke patients. Medical Research Council, Modified Brunnstrom Classification, and Functional Ambulatory Category were used in measurement of the affected side. All motor functions showed positive correlations with fractional anisotropy (FA) and fiber number (FN) ratios (p<0.05). With regard to Medical Research Council, shoulder abductor (r=0.70, 0.68), elbow flexor (r=0.75, 0.72), finger flexor (r=0.73, 0.74), and finger extensor (r=0.69, 0.77) showed strong correlations with FA and FN ratios. Modified Brunnstrom Classification (r=0.70, 0.73) also showed strong correlation. According to our findings, it appears that the CST is related to motor function of upper and lower extremities, with particular relation to motor function of upper extremities, including the hand, compared with other motor functions.

The rubrospinal tract in the human brain: diffusion tensor imaging study.

The rubrospinal tract (RST) is an extrapyramidal motor pathway in the human brain. In this study, using diffusion tensor tractography (DTT), we attempted to identify the RST in the normal human brain. Twenty-one healthy volunteers were recruited for this study. A 1.5-T scanner was used for scanning of diffusion tensor images, and the RSTs were isolated by DTT using FMRIB software. Values of fractional anisotropy (FA), mean diffusivity (MD), and tract volume of the RSTs were measured. Among 42 hemispheres of 21 subjects, RSTs were isolated in 27 hemispheres (64.28%) of 15 subjects. All identified tracts originated from the red nucleus and crossed the midline via ventral tegmental decussation. Then, they passed through the area between the inferior olivary nucleus and the inferior cerebellar peduncle in the contralateral medulla. The tracts finally descended through the lateral funiculus of the upper spinal cord. Mean values of FA, MD, and tract volume did not differ significantly between the left and right hemispheres (P>0.05). We believe that the methodologies used and the results of this study would be helpful to researchers interested in the function of the human RST and its clinical implications.

Differences in neural connectivity between the substantia nigra and ventral tegmental area in the human brain

Objectives: Many animal and a few human studies have reported on the neural connectivity of the substantia nigra (SN) and the ventral tegmental area (VTA). However, it has not been clearly elucidated so far. We attempted to investigate any differences in neural connectivity of the SN/VTA in the human brain, using diffusion tensor imaging (DTI). Methods: Sixty-three healthy subjects were recruited for this study. DTIs were acquired using a sensitivity-encoding head coil at 1. 5T. Connectivity was defined as the incidence of connection between the SN/VTA and each brain regions in the brain. Results: The connectivity of SN was higher than that of the VTA. This included in the primary motor cortex, primary somatosensory cortex, premotor cortex, prefrontal cortex, caudate nucleus, globus pallidus, putamen, nucleus accumbens, temporal lobe, amygdala, pontine basis, occipital lobe, anterior and posterior lobe of cerebellum, corpus callosum, and external capsule (p < 0.05). However, no significant differences were observed in the red nucleus, thalamus, pontine tegmentum, and medial temporal lobe between the SN and VTA (p > 0.05). Conclusions: We found the differences in neural connectivity of the SN/VTA in the human brain. The method and results of this study can provide useful information for clinicians and researchers in neuroscience, especially who work for Parkinson’s disease and patients with brain injury.

Delayed gait disturbance due to injury of the corticoreticular pathway in a patient with mild traumatic brain injury

Abstract Background: Many studies have demonstrated neural injury in patients with mild traumatic brain injury, using diffusion tensor imaging (DTI). However, knowledge regarding injury of the corticoreticular pathway (CRP) is limited. This study reports on a patient with mild TBI who showed delayed gait disturbance due to injury of the CRP following head trauma, which was demonstrated by DTI. Methods: A 14-year-old female patient suffered from an in-car accident: her head was hit with the backseat during hyperextension after flexion movement when her sedan was struck by another sedan from behind. She showed mild quadriparesis after onset. At 29 days after onset, she noted gait disturbance and aggravated quadriparesis with more severe weakness of the proximal joints. Results: No abnormality was observed on brain MRI and electromyography study performed at 10 weeks after onset. Both CRPs were discontinued at the midbrain level on 10-week DTI. Conclusion: It appears that the proximal weakness of this patient was attributed to injury of both CRPs following head trauma. It is assumed that the mild weakness at the onset of head trauma was caused by the primary traumatic axonal injury and the aggravated weakness that started from 29 days might be ascribed to the secondary traumatic axonal injury.

Anatomic Location and Somatotopic Arrangement of the Corticospinal Tract at the Cerebral Peduncle in the Human Brain

BACKGROUND AND PURPOSE: Little is known about the detailed anatomic location and somatotopic arrangement at the CP. Using DTT with FSL tools, we conducted an investigation of the anatomic location and somatotopic arrangement of the CST at the CP in the human brain. MATERIALS AND METHODS: We recruited 43 healthy volunteers for this study. DTI was obtained by using 1.5T, and CSTs for the hand and leg were obtained by using the FSL tool. The somatotopic location of the CST was evaluated as the highest probabilistic location at the upper and lower midbrain. The posterior boundary was determined as the line between the interpeduncular fossa and the lateral sulcus; we then drew a rectangle on the basis of the boundary of the CP. RESULTS: In the mediolateral direction, the highest probabilistic locations for the hand and leg were an average of 60.46% and 69.98% from the medial boundary at the upper midbrain level and 53.44% and 62.76% at the lower midbrain level, respectively. As for the anteroposterior direction, the highest probabilistic locations for the hand and leg were an average of 28.26% and 32.03% from the anterior boundary at the upper midbrain level and 30.19% and 33.59% at the lower midbrain level, respectively. CONCLUSIONS: We found that the hand somatotopy for the CST is located at the middle portion of the CP and the leg somatotopy is located lateral to the hand somatotopy.

Injury of the mammillothalamic tract in patients with subarachnoid haemorrhage: a retrospective diffusion tensor imaging study

Objective Few studies have reported on injury of the mammillothalamic tract (MTT) in patients with stroke. However, no study in patients with subarachnoid haemorrhage (SAH) has been reported. Using diffusion tensor tractography, we attempted to investigate injury of the MTT in patients with SAH. Methods We recruited 16 patients with SAH and 15 control participants. DTI was obtained at 5.7±1.5 weeks after onset and reconstruction of the MTT was performed using the probabilistic tractography method. The fractional anisotropy (FA) value and tract number of the MTT and the Mini-Mental State Examination (MMSE) score were determined. Values of FA and tract volume showing a decrement of more than two SDs that of normal control were defined as abnormal. Results The FA value and tract volume in the patient group were significantly lower than those in the control group (p<0.05). In addition, MMSE showed strong (r=0.67, p=0.005) positive correlation with tract volume without correlation with FA. In the individual analysis, 16 MTTs of 32 MTTs in 16 patients showed abnormalities of the MTT in terms of the FA value, the tract volume or the presence of a reconstructed MTT. As a result, 10 (62.5%) of 16 patients showed abnormality of the MTT in at least one hemisphere. Conclusions We found that patients with SAH showed injury of the MTT and this injury showed correlation with cognitive dysfunction.

Injury of the dentato-rubro-thalamic tract in a patient with mild traumatic brain injury

Abstract Background: Several studies using diffusion tensor tractography (DTT) have demonstrated injury of the dentato-rubro-thalamic tract (DRTT) in various brain pathologies. However, no study on traumatic brain injury (TBI) has been reported. This case study attempted to demonstrate injury of the DRTT in a patient with mild TBI, using DTT. Case description: A 41-year-old female patient suffered from head trauma resulting from flexion-hyperextension injury by being hit from behind by a running car while stopped at an intersection. The patient lost consciousness and experienced post-traumatic amnesia for ∼1minute from the time of the car-accident. The patient’s Glasgow Coma Scale score was 15. No specific lesion was observed on brain MRI. At 2 weeks after onset, the patient began to show resting and intentional tremor (more severe in the right upper and lower extremities) and ataxic gait. Her symptoms had been aggravated with the passage of time. On 1-month DTT, the left DRTT, which originated from the left dentate nucleus of the cerebellum, was thinner than the right DRTT. Conclusions: This study demonstrated injury of the DRTT in a patient with tremor and ataxia following mild TBI, using DTT. It is believed that analysis of the DRTT using DTT would be useful in elucidating the cause of post-traumatic abnormal movements.

Neural connectivity of the anterior body of the fornix in the human brain: Diffusion tensor imaging study

A few studies have reported on the neural connectivity of the fornix in the human brain, however, little is known about the neural connectivity of the anterior body of the fornix. In this study, we used diffusion tensor imaging in investigation of the neural connectivity of the anterior body of the fornix in normal subjects. Forty healthy subjects were recruited for this study. A seed region of interest was placed on the anterior body of the fornix using the FMRIB Software Library. Connectivity was defined as the incidence of connection between the anterior body of the fornix and any neural structure of the brain at the threshold of 5, 25, and 50 streamlines. In all subjects, the anterior body of the fornix showed 100% connectivity to the anterior commissure and hypothalamus at thresholds of 5, 25, and 50. On the other hand, regarding the thresholds of 5, 25, and 50, the anterior body of the fornix showed connectivity to the septal forebrain region (53.8, 23.8, and 15.0%), frontal lobe via anterior commissure (41.3,12.5, and 10.0%), medial temporal lobe (85.0,66.3, and 62.5%), lateral temporal lobe (75.0, 56.3, and 35.0%), occipital lobe (21.3, 5.0, and 1.3%), frontal lobe via septum pellucidum (28.8, 13.8, and 8.8%), tegmentum of midbrain (7.5, 5.0, and 0%), tectum of midbrain (2.5,0, and 0%), and tegmentum of pons (5.0,0, and 0%). The anterior body of the fornix showed high connectivity with the anterior commissure and hypothalamus, and brain areas relevant to cholinergic nuclei (the septal forebrain region and brainstem) and memory function (the medial temporal lobe).