Anatomical location of the spinothalamic tract in the subcortical white matter in the human brain: A diffusion tensor imaging study.

INTRODUCTION: We investigated the anatomical location of the spinothalamic tract and its thalamocortical pathway (STT) in the subcortical white matter in normal subjects, using diffusion tensor tractography (DTT). MATERIALS AND METHODS: The STT was reconstructed using FMRIB software in 40 normal subjects. The most probable locations of the STT were defined as the location on an axial slice of the centrum semiovale (CS), corona radiata (CR), and posterior limb of the internal capsule (PL). RESULTS: The STT was located at an average of 62.66% in the anterior to posterior direction along a horizontal line that passed between the anterior and posterior ends of the brain, and an average of 36.29% lateral from the midline in the CS. In the CR, the STT was located at an average of 79.60% in the anterior to posterior direction along the aforementioned horizontal line, and an average of 36.36% lateral from the midline. In the PL, the STT was located at an average of 83.58% in the anterior to posterior direction along a horizontal line that passed the middle point at the genu of the internal capsule and the posterior endpoint of the putamen, and an average of 69.69% lateral from the midline to the lateral end of the putamen. CONCLUSIONS: We found the precise anatomical location of the STT in the subcortical white matter in the human brain using DTT. We believe that the results of this study will be helpful to clinicians in the neuroscience field.

Aging of the Nigrostriatal Tract in the Human Brain: A Diffusion Tensor Imaging Study.

Background and Objectives: The loss of dopamine neurons in the nigrostriatal tract (NST) is one of the main pathological features of Parkinson's disease (PD), and degeneration of the NST leads to the motor symptoms observed in PD, which include hypokinesia, tremors, rigidity, and postural imbalance. In this study, we used diffusion tensor tractography (DTT) to investigate the aging of the NST in normal human subjects to elucidate human brain structures. Materials and Methods: Fifty-nine healthy subjects were recruited for this study and allocated to three groups, that is, a 20 to ≤39 year old group (the young group), a 40 to ≤59 year old group (the middle-aged group), and a ≥60 year old group (the old group). DTT scanning was performed, and NSTs were reconstructed using the probabilistic tractography method. NSTs were defined by selecting fibers passing through seed and target regions of interest placed on the substantia nigra and the striatum. Results: A significant negative correlation was observed between age and fractional anisotropy and tract volume (TV) of the NST. Mean TV values of the NST were significantly lower in the old group than in the young and middle-aged groups (p < 0.05). The TV values of the NST were significantly reduced with age for men and women (p < 0.05). Conclusion: We found that aging of the NST began in the 3rd decile and progressed steadily throughout life until old age, when it exhibited significant degeneration. We suspect these results are related to the correlation between the incidence of PD and age.

Injury of the dentato-rubro-thalamic tract in a patient with intentional tremor after mild traumatic brain injury: a case report.

OBJECTIVES: We imaged the dentato-rubro-thalamic tract (DRTT) and cortico-ponto-cerebellar tract (CPCT) using diffusion tensor tractography (DTT) to evaluate the cortico-cerebellar-cortical circuit in a patient with tremor in both hands after mild TBI. We found bilateral DRTT injury in the DTT. METHOD: A 50-year-old male presented with action tremor in both hands 1 week after mild TBI. One month before the visit, the patient had a head injury from a fall on a bus. The patient lost consciousness for 1 min and experienced post-traumatic amnesia for approximately 5 min after the accident. His Glasgow Coma Scale score was 15. The action tremor presented with a frequency of 3 Hz in both hands. No specific lesion was observed with a conventional brain MRI. RESULTS: DTT, performed 1.5 months after TBI, showed that the right DRTT was not reconstructed and the left DRTT had thinned. However, CPCT integrity was well-preserved in both hemispheres. The tremor disappeared after oral treatment with 30 mg/day indenol. The patient's tremor would have been caused by disruption of the bilateral DRTT following mild TBI. CONCLUSION: DRTT and CPCT analysis using DTT would be useful for diagnosing abnormal movement problems, including tremor and ataxia, in patients following mild TBI.

Injury of auditory radiation and sensorineural hearing loss from mild traumatic brain injury.

OBJECTIVES: We report on a patient with sensorineural hearing loss from injury of the auditory radiation following mild TBI, diagnosed by diffusion tensor tractography (DTT). METHOD: A 35-year-old female patient suffered head trauma. While walking in a crosswalk, her left lumbar area was hit by a turning car and she fell to the ground. She was pulled behind the car for several meters while her occipital area repeatedly hit the ground. She complained that she began to feel hearing impairment approximately two weeks after the head trauma, that aggravated over time. Approximately 1.5 years after head trauma, when she visited a university hospital for evaluation of the brain, she complained of severe hearing impairment. To characterize the patient's hearing loss, pure tone audiometry was evaluated in a sound proof room to screen her hearing status for the frequencies 250-8000 Hz. A pure tone threshold in the range of 41-60 dB HL was considered moderate sensorineural hearing loss and 61-80 dB HL severe. However, no abnormality was observed in either ear on physical examination. The patient was diagnosed with bilateral moderate sensorineural hearing loss. RESULTS: On 1.5 year DTT, the auditory radiation was narrowed in both hemispheres. CONCLUSION: Neural injury of the auditory radiation was demonstrated in a patient with sensorineural hearing loss following mild TBI, using DTT.

Recovery of an injured cingulum concurrent with improvement of short-term memory in a patient with mild traumatic brain injury.

OBJECTIVES: We reported on a patient with mild traumatic brain injury (TBI) who showed recovery of an injured cingulum concurrent with improvement of short-term memory, which was demonstrated on follow-up diffusion tensor tractography (DTT). METHODS: A 55-year-old male patient suffered head trauma resulting from falling from approximately 2 m while working at a construction site. The patient showed mild memory impairment (especially short-term memory impairment) at 3 months after onset: Memory Assessment Scale (global memory: 95 (37%ile), short-term memory: 75 (5%ile), verbal memory: 80 (9%ile) and visual memory: 112 (79%ile)). By contrast, at 2 years after onset, his mild memory impairment had improved to a normal state: Memory Assessment Scale (global memory: 104 (61%ile), short-term memory: 95 (37%ile), verbal memory: 101 (53%ile) and visual memory: 106 (66%ile)). RESULTS: On 3-month DTT, discontinuation of the right anterior cingulum was observed over the genu of the corpus callosum, while on 2-year DTT, the discontinued right anterior cingulum was elongated to the right basal forebrain. CONCLUSION: In conclusion, recovery of an injured cingulum concurrent with improvement of short-term memory was demonstrated in a patient with mild TBI.

The relation between the motor evoked potential and diffusion tensor tractography for the corticospinal tract in chronic hemiparetic patients with cerebral infarct.

We examined the relation between the results of transcranial magnetic stimulation (TMS) and diffusion tensor tractography (DTT) for the corticospinal tract (CST) in chronic hemiparetic patients with a middle cerebral artery (MCA) territory infarct. The amplitude of motor evoked potential (MEP) was closely related to the FN of the CST on DTT in chronic hemiparetic patients with an MCA infarct. We believe that our results would be helpful in more precise estimation of the CST.

Differences of the medial lemniscus and spinothalamic tract according to the cortical termination areas: A diffusion tensor tractography study.

We investigated differences of the medial lemniscus and its thalamocortical pathway (ML), and the spinothalamic tract and its thalamocortical pathway (STT) according to the cortical termination areas. We found that the ML and STT terminated in the motor cortex and the somatosensory cortex. The ML may be closely related to the motor cortex for motor planning and execution, while the STT may be closely related to the cerebral cortex for somatosensory function and motor execution.

The anatomical location of the corticoreticular pathway at the subcortical white matter in the human brain: A diffusion tensor imaging study.

We attempted to investigate the anatomical location of the corticoreticular pathway (CRP) in the subcortical white matter in the human. Thirty-three healthy volunteers were recruited. The locations of the CRP and corticospinal tract (CST) were defined as the location on axial slice of the centrum semiovale, corona radiata, and posterior limb of the internal capsule. The CRP was located close antero-medially to the CST in all three regions of subcortical white matter.

Damage to the Optic Radiation in Patients With Mild Traumatic Brain Injury.

BACKGROUND: There are known limitations of conventional computed tomography and magnetic resonance imaging in detecting neural injury in patients with mild traumatic brain injury (TBI). Diffusion tensor imaging (DTI) provides a method to further assess cerebral injury in this patient population. We report 2 patients with mild TBI who showed injury of the optic radiation (OR) as demonstrated by DTI. METHOD: Two patients who complained of visual field loss after mild TBI and 9 age-matched normal control subjects were recruited for this study. Peripheral field defects were detected with automated perimetry in both patients. RESULTS: Regarding the configuration of OR, the total volume of OR was decreased in the right OR of both patients compared with controls; in contrast, the left ORs were divided into 2 parts in both patients. The voxel numbers of both ORs in both patients were more than 2 standard deviations lower than that of normal control subjects. The apparent diffusion coefficient value of the right OR in patient 2 was more than 2 standard deviations higher than that of normal controls. CONCLUSIONS: We demonstrated injury of the OR using DTI in 2 patients who showed visual field defects after mild TBI.

Traumatic axonal injury of the corticospinal tract in the subcortical white matter in patients with mild traumatic brain injury.

BACKGROUND: Little is known about injury of the corticospinal tract (CST) in patients with mild traumatic brain injury (TBI). This study reports on patients with mild TBI who showed traumatic axonal injury of the CST in the sub-cortical white matter, as demonstrated by diffusion tensor tractography (DTT). METHODS: Four patients with mild TBI who complained of motor weakness and had DTT parameters within the normal range, including fractional anisotropy, apparent diffusion coefficient and fibre number of the CST, and 10 normal control subjects were recruited for this study. RESULTS: All four patients showed partial tearing of the CSTs in a portion of the sub-cortical white matter in both hemispheres on DTT. However, three patients showed low amplitude on motor evoked potential obtained from both hand muscles by transcranial magnetic stimulation and two patients revealed abnormality of hand motor function in terms of grip strength or Purdue Pegboard score. CONCLUSIONS: This study demonstrated traumatic axonal injury of the CST using configurational evaluation of DTT in patients with mild TBI. It is believed that configurational evaluation using DTT would be a useful technique for detection of localized traumatic axonal injury in patients with mild TBI.

The distribution of the cortical origin of the corticoreticular pathway in the human brain: a diffusion tensor imaging study.

We investigated the distribution of the cortical origin of the corticoreticular pathway (CRP) in the human brain. Forty normal subjects were recruited and CRPs from four cortical areas were reconstructed. The first cortical origin area of the CRP was the premotor cortex and the next was the primary motor cortex. Although the CRP fibers also originated from the primary somatosensory cortex and prefrontal cortex, they occupied the smallest portion among four regions of interest.

Functional role of the corticoreticular pathway in chronic stroke patients.

BACKGROUND AND PURPOSE: The corticoreticular pathway (CRP) is known to be an important extrapyramidal tract for walking ability. However, little is known about the functional role of the CRP in recovery of walking ability. We investigated relation between the CRP and walking ability in chronic hemiparetic stroke patients. METHODS: Among 209 consecutive patients, 54 patients, who showed complete injury of the corticospinal tract (CST) in the affected hemisphere on diffusion tensor tractography, and 20 normal subjects were recruited. Functional ambulation category was used in measurement of walking ability. The fractional anisotropy value, apparent diffusion coefficient value, and fiber volume of the CRP and CST were used for the diffusion tensor imaging parameters. RESULTS: In the affected hemisphere, no significant difference in diffusion tensor imaging parameters of the CRP was observed between patient subgroups. In the unaffected hemisphere, patients who were able to walk showed significantly increased fiber volume of the CRP, compared with patients who could not walk and normal control subjects (P<0.05), without significant difference in fractional anisotropy and apparent diffusion coefficient values. In addition, the fiber volume of the CRP in the unaffected hemisphere showed positive correlation with functional ambulation category (P<0.05). In contrast, diffusion tensor imaging parameters of the CST in the unaffected hemisphere showed no correlation with functional ambulation category (P>0.05). CONCLUSIONS: The increased fiber volume of the CRP in the unaffected hemisphere seems to be related to walking ability in patients with chronic stroke. Therefore, the compensation of the CRP in the unaffected hemisphere seems to be one of the mechanisms for recovery of walking ability after stroke.

Comparison of cortical activation patterns by somatosensory stimulation on the palm and dorsum of the hand.

OBJECTIVES: Little is known about differences of cortical activation according to body location. We attempted to compare brain activation patterns by somatosensory stimulation on the palm and dorsum of the hand, using functional magnetic resonance imaging (fMRI). METHOD: We recruited 15 healthy right-handed volunteers for this study. fMRI was performed during touch stimulation using a rubber brush on an area of the same size on the palm or dorsum of the hand. Regions of interest (ROIs) were drawn at the primary sensory-motor cortex (SM1), posterior parietal cortex, and secondary somatosensory cortex. RESULTS: Group analysis of fMRI data indicated that touch stimulation on the palm resulted in production of more activated voxels in the contralateral SM1 and posterior parietal cortex than on the dorsum of the hand. The most activated ROI was found to be the contralateral SM1 by stimulation of the palm or dorsum, and the number of activated voxels (5875) of SM1 by palm stimulation was more than 2 times that (2282) of dorsum stimulation. The peak activated value in the SM1 by palm stimulation (16.43) was also higher than that of the dorsum (5.52). CONCLUSION: We found that stimulation of the palm resulted in more cortical activation in the contralateral SM1 than stimulation of the dorsum. Our results suggested that the palm of the hand might have larger somatotopy of somatosensory representation for touch in the cerebral cortex than the dorsum of the hand. Our results would be useful as a rehabilitation strategy when more or less somatosensory stimulation of the hand is necessary.

Diffusion tensor imaging findings of optic radiation in patients with putaminal hemorrhage.

OBJECTIVES: Little is known about optic radiation (OR) injury in intracerebral hemorrhage (ICH). We attempted to investigate OR injury in patients with ICH by diffusion tensor imaging (DTI). METHODS: Forty-three consecutive patients with putaminal hemorrhage and 40 normal healthy control subjects were recruited. DTI data were acquired at the beginning of rehabilitation (average 34 days after onset). DTI-Studio software was used to reconstruct the OR. Fractional anisotropies (FA) and fiber numbers of the ORs were measured. FA values and fiber numbers of affected ORs were described as abnormal when they were more than 2.5 SD lower than those of normal controls. RESULTS: Thirty (70%) of the 43 patients showed an OR abnormality in the affected hemisphere. In 13 (30%) patients, the affected OR was disrupted or nonreconstructable. On the other hand, of the 20 patients with preserved OR integrity, 14 (33%) had a low FA value and 3 (7%) a low FA and fiber number. The other 13 (30%) of the 43 patients had no abnormal OR findings. CONCLUSION: Seventy percent of patients showed any abnormality of OR in the affected hemisphere on DTI. This result suggests that patients with putaminal hemorrhage are at high risk of OR injury.

Traumatic thalamic injury demonstrated by diffusion tensor tractography of the spinothalamic pathway.

BACKGROUND: This study reports on a patient with traumatic brain injury (TBI) with a thalamic lesion in the ventroposterolateral nucleus which was demonstrated by diffusion tensor tractography (DTT) for the spinothalamic tract and its thalamocortical pathway (STP). METHODS: One patient with TBI and eight normal control subjects were recruited. A 64-year-old woman who had suffered a motor vehicle accident presented with a persisting tingling sensation and pain in her right upper and lower extremities at 3 weeks after onset. The patient showed impaired touch sensation, but normal proprioception. Diffusion tensor imaging was performed at 1 month after onset. Fractional anisotropy (FA) and mean diffusivity were measured using a region of interest method along the STP. RESULTS: DTT showed normal STP integrities as compared with normal controls. However, the FA values of the left STP at the thalamus were more than 2 SD decreased. The diminished FA value of the left STP in the left thalamus seems to indicate injury of the left ventrolateroposterior nucleus. Central pain and impaired touch sensation of right extremities supports the presence of left STP injury at the ventroposterolateral nucleus in this patient. CONCLUSION: It is believed that DTT for the STP provides a useful means of detecting thalamic injury in TBI.

Neural Injury of the Dopaminergic Pathways in Patients with Middle Cerebral Artery Territory Infarct: A Diffusion Tensor Imaging Study.

The mesocortical tract (MCT) and mesolimbic tract (MLT), dopaminergic pathways originating from the ventral tegmental area in the midbrain to the ventral striatum (nucleus accumbens) and prefrontal cortex, play a crucial role in regulating incentive salience. This study aimed to investigate the potential changes in the MCT and MLT pathways following ischemic stroke, such as middle cerebral artery (MCA) infarction. We enrolled thirty-six patients with MCA infarction and forty healthy individuals with no history of psychiatric or neurological disorders. Using diffusion tensor tractography, we examined the injury to the affected and unaffected MCT and MLT pathways in patients with MCA infarction, comparing them to the control group. Our findings revealed a significant difference in the mean values of fractional anisotropy (FA) and tract volume (TV) of the MCT and MLT pathways between the patient and control groups (p < 0.05). Specifically, the mean FA of the MCT and MLT showed a decrease of 7.94% and 6.33%, respectively, in the affected side compared to the control group (p < 0.05). Similarly, the mean TV of the MCT and MLT showed a decrease of 73.22% and 78.79%, respectively, in the affected side compared to the control group (p < 0.05). These changes were significantly different from those of the unaffected MCT, MLT, and control groups (p < 0.05). Our study suggests that MCA infarction can cause significant damage to the affected MCT and MLT pathways, potentially contributing to our understanding of the pathophysiology of post-stroke depression.

Degeneration of nigrostriatal pathway in patients with middle cerebral infarct: A diffusion tensor imaging study.

The nigrostriatal tract (NST) is a dopaminergic pathway that runs from the substantia nigra pars compacta in the midbrain to the dorsal striatum (caudate nucleus and putamen) and regulates voluntary movement via the basal ganglia motor loops. However, it is unclear whether the effects of ischemic stroke, such as middle cerebral artery (MCA) infarction, are associated with changes in the NST. Thirty MCA infarct patients and 40 healthy subjects with no history of psychiatric or neurological disorders were enrolled in the present study. Diffusion tensor tractography was used to investigate injury to the ipsilesional and contralesional NST in MCA infarct patients compared to the normal human brain. There was a significant difference in the mean fractional anisotropy and tract volume values of the NST between the patient and control groups (P < .05). post hoc analysis revealed that the mean fractional anisotropy and tract volume from the ipsilesional NST showed a significant difference compared with those of the contralesional NST and control groups (P < .05). MCA infarction can lead to damage to the ipsilesional NST, which can impair one's ability to stop unwanted muscular contractions or voluntary movement.

Aging of reward dopamine tracts in the human brain: A diffusion tensor imaging study.

The mesocortical tract (MCT) and mesolimbic tract (MLT) are reward dopaminergic tracts that have been shown to play a role in regulating reward stimuli, including both incentive salience and social stimuli. In the current study, we examined aging of the MCT and MLT in normal human participants to explain human brain structures using diffusion tensor tractography (DTT). Sixty-four healthy participants were recruited for this study and allocated to 3 groups based on participants' age. Diffusion tensor imaging was performed, and MCTs and MLTs were reconstructed using the probabilistic tractography method. A significant negative correlation was observed between age and fractional anisotropy and tract volume of the MCT and MLT, whereas a positive correlation was observed between age and mean diffusivity. The mean fractional anisotropy value of the MCT was significantly lower in the old group than in the young and middle-aged groups (P < .05). The mean diffusivity values of the MCT and MLT were significantly higher in the old group than in the young and middle-aged groups (P < .05). The mean tract volume values of the MCT and MLT were significantly lower in the old group than in the young group (P < .05). We found that degenerative changes in the MCT and MLT began in participants in the 20s-30s, progressed steadily throughout life, and accelerated in the 60s.

Traumatic trigeminal neuropathy after whiplash injury: A case report.

RATIONALE: Many studies using diffusion tensor tractography (DTT) have reported trigeminal neuropathy in various neurological diseases. However, no study on traumatic trigeminal neuropathy following whiplash has been reported. PATIENT CONCERNS: A 51-year old female suffered an indirect head trauma resulting from a flexion-hyperextension injury. At approximately 30 minutes after onset, she began to sense a headache in the left frontal area and sensory changes in the left facial area, signs that intensified with the passage of time. At 7 days after onset, she visited the rehabilitation department of our university hospital and described the characteristics and severity of pain as follows: headache on the left frontal area including the forehead with intermittent squeezing and numbness sensations. Her visual analog scale pain score was 6 with her left cheek having a continuous, dull, swelling sensation (visual analog scale score: 1). On neurological examination, she revealed mild allodynia without hyperalgesia or somatosensory change on the head, cheek, tongue, and oral cavity. DIAGNOSIS: Diffusion tensor imaging data were acquired 7 days after onset. On DTT, the left trigeminal nerve showed discontinuation in the middle portion compared to that of the right trigeminal nerve. Traumatic trigeminal neuropathy was diagnosed based on her clinical features and DTT findings. INTERVENTION: She was prescribed carbamazepine (200 mg/day) and pregabalin (150 mg/day), and her facial pain was well-controlled to a tolerable level. OUTCOMES: These drugs were stopped after approximately 7 month's administration, however, she did not complain of facial pain. LESSONS: By using DTT, we demonstrated traumatic trigeminal neuropathy in a patient with whiplash. We suggest that DTT would be a useful tool for detection of traumatic trigeminal neuropathy in patients who show clinical features of trigeminal neuropathy following whiplash.

Aging of the mesolimbic tract in the human brain: A diffusion tensor imaging study.

The mesolibic tract (MLT) is a dopaminergic tract that has been shown to play a role in regulating reward stimuli, including both incentive salience and social stimuli. In the current study, we examined the aging of MLT in normal human participants to explain human brain structures using diffusion tensor tractography (DTT). Fifty-seven healthy participants were recruited for this study and allocated to six groups based on their age. Diffusion tensor imaging (DTI) scanning was performed and MLTs were reconstructed using the probabilistic tractography method. MLTs were defined by selecting fibers passing through the seed and target regions of interest placed on the ventral segmental area and nucleus accumbens. A significant negative correlation was observed between age and the voxel number (VN) of MLT, while a positive correlation was observed between age and the apparent diffusion coefficient (ADC). The mean VN value of the MLT was significantly lower in the 60s and 70s age groups than in the 20s, 40s, and 50s (P < .05). The mean ADC value of the MLT was significantly higher in the 60s and 70s groups than in the 20s, 30s, and 40s, 50s groups (P < .05). We found that aging of the MLT began in the 20s or 30s and progressed steadily throughout life until the 60s, when it exhibited significant degeneration. We believe this affect may play a role in the decline of memory and social interaction with aging in normal participants.