- Fluctuating regional brainstem diffusion imaging measures of microstructure across the migraine cycle. [Journal Article]
- EeNeuro 2019 Jul 12
- The neural mechanisms responsible for the initiation and expression of migraines remain unknown. Though there is growing evidence of changes in brainstem anatomy and function between attacks, very li…
The neural mechanisms responsible for the initiation and expression of migraines remain unknown. Though there is growing evidence of changes in brainstem anatomy and function between attacks, very little is known about brainstem function and structure in the period immediately prior to a migraine. The aim of this investigation is to use brainstem-specific analyses of diffusion weighted images to determine if the brainstem pain processing regions display altered structure in individuals with migraine across the migraine cycle, and in particular immediately prior to a migraine. Diffusion tensor images (29 controls, 36 migraineurs) were used to assess brainstem anatomy in migraineurs compared with controls. We found that during the interictal phase, migraineurs displayed greater mean diffusivity in the region of the spinal trigeminal nucleus, dorsomedial/dorsolateral pons and midbrain periaqueductal gray matter/cuneiform nucleus. Remarkably, the mean diffusivity returned to controls levels during the 24-hour period immediately prior to a migraine, only to increase again within the three following days. Additionally, fractional anisotropy was significantly elevated in the region of the medial lemniscus/ventral trigeminal thalamic tract in migraineurs compared with controls over the entire migraine cycle. These data show that regional brainstem anatomy changes over the migraine cycle, with specific anatomical changes occurring in the 24 hours prior to onset. These changes may contribute to the activation of the ascending trigeminal pathway by either an increase in basal traffic or by sensitising the trigeminal nuclei to external triggers, with activation ultimately resulting in perception of head pain during a migraine attack.SIGNIFIANCE STATEMENT It has been hypothesised that modulation of brainstem pain pathways may be critical for the initiation of migraine attacks. There is some evidence that altered brainstem function, possibly involving increased astrocyte activation, occurs immediately prior to a migraine attack. We sought to obtain evidence to support this theory. Using diffusion tensor imaging, we found that immediately prior to a migraine, mean diffusivity decreased in the spinal trigeminal nucleus, dorsomedial/dorsolateral pons and midbrain periaqueductal gray matter/nucleus cuneiform. Mean diffusivity then increased again immediately following the migraine attack. Decreased mean diffusivity before a migraine is consistent with increased astrocyte activation, since astrocyte processes enlarge during activation. These changes may underlie changes in brainstem function that are essential for the generation of a migraine.
- "Eight and a half" and "nine syndrome" rare presentation of pontine lesions; case reports and review of literature. [Journal Article]
- IJIran J Neurol 2018 Oct 07; 17(4):189-191
- CONCLUSIONS: Apart from different etiologies, recognition of EHS or nine syndrome allows precise localization of the lesion to lower pontine tegmentum ipsilaterally.
- Diffusion Kurtosis Imaging Detects Microstructural Changes in a Methamphetamine-Induced Mouse Model of Parkinson's Disease. [Journal Article]
- NRNeurotox Res 2019 Jun 18
- Methamphetamine (METH) abuse is known to increase the risk of Parkinson's disease (PD) due to its dopaminergic neurotoxicity. This is the rationale for the METH model of PD developed by toxic METH do…
Methamphetamine (METH) abuse is known to increase the risk of Parkinson's disease (PD) due to its dopaminergic neurotoxicity. This is the rationale for the METH model of PD developed by toxic METH dosing (10 mg/kg four times every 2 h) which features robust neurodegeneration and typical motor impairment in mice. In this study, we used diffusion kurtosis imaging to reveal microstructural brain changes caused by METH-induced neurodegeneration. The METH-treated mice and saline-treated controls underwent diffusion kurtosis imaging scanning using the Bruker Avance 9.4 Tesla MRI system at two time-points: 5 days and 1 month to capture both early and late changes induced by METH. At 5 days, we found a decrease in kurtosis in substantia nigra, striatum and sensorimotor cortex, which is likely to indicate loss of DAergic neurons. At 1 month, we found an increase of kurtosis in striatum and sensorimotor cortex and hippocampus, which may reflect certain recovery processes. Furthermore, we performed tract-based spatial statistics analysis in the white matter and at 1 month, we observed increased kurtosis in ventral nucleus of the lateral lemniscus and some of the lateral thalamic nuclei. No changes were present at the early stage. This study confirms the ability of diffusion kurtosis imaging to detect microstructural pathological processes in both grey and white matter in the METH model of PD. The exact mechanisms underlying the kurtosis changes remain to be elucidated but kurtosis seems to be a valuable biomarker for tracking microstructural brain changes in PD and potentially other neurodegenerative disorders.
- StatPearls: Physiology, Vibratory Sense [BOOK]
- BOOKStatPearls Publishing: Treasure Island (FL)
- Our somatosensory system has three basic types of sensory receptors which detect different types of external stimuli. These include mechanoreceptors which detect light touch, vibration, pressure and …
Our somatosensory system has three basic types of sensory receptors which detect different types of external stimuli. These include mechanoreceptors which detect light touch, vibration, pressure and texture; nociceptors which detect pain; and thermoreceptors which detect temperature. Mechanoreceptors further divide into Merkel disks, Meissner’s corpuscles, Ruffini endings, and Pacinian corpuscles based on the specific type of mechanical stimuli they perceive. The perception of vibratory sensation is by two main types of mechanoreceptors, Meissner corpuscles (MC) and Pacinian corpuscles (PC). MCs are large myelinated fibers which detect low-frequency vibration and are present in glabrous (smooth, hairless) skin on fingertips and eyelids. PCs contain large myelinated A-beta fibers which are rapidly adapting and are present in the deeper layers of skin, ligaments, and joints where their function is to detect high-frequency vibration and deep pressure. The vibratory sensations transmit via the dorsal column of the spinal cord to the primary somatosensory area of cortex. The sensory signals from Meissner and Pacinian corpuscles terminate in the cell body of dorsal root ganglion (pseudounipolar neurons) and constitute the first order neuron of dorsal column. The axonal processes leave the dorsal horn gray matter and enter the dorsal funiculus to constitute either the fasciculus gracilis or the fasciculus cuneatus. Fasciculus gracilis carries sensory information from the lower limbs and synapses with the nucleus gracilis in the caudal medulla. It is located medially in the dorsal column as compared to fasciculus cuneatus which is located laterally and carries sensory information from the upper extremities and synapses with nucleus cuneatus in caudal medulla. That is why fasciculus cuneatus is only present at spinal level T6 and above. Nucleus gracilis and nucleus cuneatus constitute the second order neurons of this pathway. The fibers from both sides decussate in caudal medulla as internal arcuate fibers and ascend contralaterally as medial lemniscus. The second synapse occurs in the ventral posterolateral nucleus (VPL) of the thalamus, which constitutes the third order neurons of the pathway. Axons from VPL nucleus travel through the posterior limb of the internal capsule and terminate in the primary somatosensory cortex, located in the postcentral gyrus.
- Cortical lateralization of cheirosensory processing in callosal dysgenesis. [Journal Article]
- NCNeuroimage Clin 2019 Apr 01; 23:101808
- The paradoxical absence of a split-brain syndrome in most cases of callosal dysgenesis has originated three main hypotheses, namely, (i) bilateral cortical representation of language, (ii) bilateral …
The paradoxical absence of a split-brain syndrome in most cases of callosal dysgenesis has originated three main hypotheses, namely, (i) bilateral cortical representation of language, (ii) bilateral thalamocortical projections of somatosensory pathways conveyed by the spinothalamic-medial lemniscus system, and (iii) a variable combination of (i) and (ii). We used functional neuroimaging to investigate the cortical representation and lateralization of somatosensory information from the palm of each hand in six cases of callosal dysgenesis (hypothesis [ii]). Cortical regions of interest were contralateral and ipsilateral S1 (areas 3a and 3b, 1 and 2 in the central sulcus and postcentral gyrus) and S2 (parts of areas 40 and 43 in the parietal operculum). The degree of cortical asymmetry was expressed by a laterality index (LI), which may assume values from -1 (fully left-lateralized) to +1 (fully right-lateralized). In callosal dysgenesis, LI values for the right and the left hands were, respectively, -1 and + 1 for both S1 and S2, indicating absence of engagement of ipsilateral S1 and S2. In controls, LI values were - 0.70 (S1) and - 0.51 (S2) for right hand stimulation, and 0.82 (S1) and 0.36 (S2) for left hand stimulation, reflecting bilateral asymmetric activations, which were significantly higher in the hemisphere contralateral to the stimulated hand. Therefore, none of the main hypotheses so far entertained to account for the callosal dysgenesis-split-brain paradox have succeeded. We conclude that the preserved interhemispheric transfer of somatosensory tactile information in callosal dysgenesis must be mediated by a fourth alternative, such as aberrant interhemispheric bundles, reorganization of subcortical commissures, or both.
- Brain Structural Alterations in Left-Behind Children: A Magnetic Resonance Imaging Study. [Journal Article]
- FNFront Neural Circuits 2019; 13:33
- Parental migration has caused millions of children left behind, especially in China and India. Left-behind children (LBC) have a high risk of mental disorders and may present negative life outcomes i…
Parental migration has caused millions of children left behind, especially in China and India. Left-behind children (LBC) have a high risk of mental disorders and may present negative life outcomes in the future. However, little is known whether there are cerebral structural alterations in LBC in relative to those with parents. This study is to explore the effect of parental migration on brain maturation by comparing gray matter volume (GMV) and fractional anisotropy (FA) of LBC with well-matched non-LBC. Thirty-eight LBC (21 boys, age = 9.60 ± 1.8 years) and 30 non-LBC (19 boys, age = 10.00 ± 1.95 years) were recruited and underwent brain scans in 3.0 T MR. Intelligence quotient and other factors including family income, guardians' educational level and separation time were also acquired. GMV and FA were measured for each participant and compared between groups using 2-sample t-tests with atlas-based analysis. Compared to non-LBC, LBC exhibited greater GMV in emotional and cortico-striato-thalamo-cortical circuits, and altered FA in bilateral superior occipitofrontal fasciculi and right medial lemniscus (p < 0.05, Cohen's d > 0.89, corrected for false-discovery rate). Other factors including family income, guardians' educational level and separation time were not associated with these brain changes. Our study provides empirical evidence of altered brain structure in LBC compared to non-LBC, responsible for emotion regulation and processing, which may account for mental disorders and negative life outcome of LBC. Our study suggests that absence of direct biological parental care may impact children's brain development. Therefore, public health efforts may be needed to provide additional academic and social/emotional supports to LBC when their parents migrate to seeking better economic circumstances, which has become increasingly common in developing countries.
- DTI study on rehabilitation of the congenital deafness auditory pathway and speech center by cochlear implantation. [Journal Article]
- EAEur Arch Otorhinolaryngol 2019 May 24
- CONCLUSIONS: Preoperative children ages and inferior colliculus FA values were important factors influencing postoperative CAP score. Inferior colliculus FA value is a vital influencing factor in rehabilitation after cochlear implantation.
- Microstructural integrity of corticospinal and medial lemniscus tracts: insights from diffusion tensor tractography of right-hand amputees. [Journal Article]
- JNJ Neurophysiol 2019 Jul 01; 122(1):316-324
- Reductions in sensory and motor activity following unilateral upper limb amputation during adulthood are associated with widespread, activity-dependent reorganization of the gray matter and white mat…
Reductions in sensory and motor activity following unilateral upper limb amputation during adulthood are associated with widespread, activity-dependent reorganization of the gray matter and white matter through the central nervous system. Likewise, in cases of congenital limb absence there is evidence that limited afferent or efferent activity affects the structural integrity of white matter pathways serving the affected side. Evidence that the structural integrity of mature sensory and motor tracts controlling the lost upper limb exhibits similar activity dependence is, however, sparse and inconsistent. Here we used diffusion tensor tractography to test whether amputation of the dominant right hand during adulthood (n = 16) alters the microstructural integrity of the major sensory (medial lemniscus, ML) and motor (corticospinal tract, CST) pathways controlling missing hand function. Consistent with prior findings, healthy control subjects (n = 27) exhibited higher fractional anisotropy (FA), an index of white matter microstructural integrity, within dominant left CST and nondominant right ML. Critically, in contrast to what might be expected if the microstructural organization of these tracts is activity dependent, these asymmetries persisted in amputees. Moreover, we failed to detect any differences in dominant left ML or CST between healthy control subjects and amputees. Our results are consistent with these white matter tracts being robust to changes in activity once mature or that continued use of the residual limb (in a compensatory fashion or with prosthesis) provides stimulation sufficient to maintain tract integrity. NEW & NOTEWORTHY We report that unilateral hand amputation in adults has no significant effects on the structure of major sensory or motor pathways contralateral to the amputation. Our results are consistent with the organization of these white matter tracts being robust to changes in activity once mature or that continued use of the residual limb (with or without a prosthesis) provides stimulation sufficient to maintain tract integrity.
- Nicotinic acetylcholine receptor subunit α7 knockout mice exhibit degraded auditory temporal processing. [Journal Article]
- JNJ Neurophysiol 2019 May 22
- The CHRNA7 gene that encodes α7 subunit of the nicotinic acetylcholine receptor (α7 nAChR) has been associated with some autism spectrum disorders and other neurodevelopmental conditions characterize…
The CHRNA7 gene that encodes α7 subunit of the nicotinic acetylcholine receptor (α7 nAChR) has been associated with some autism spectrum disorders and other neurodevelopmental conditions characterized, in part, by auditory and language impairment. These conditions may include auditory processing disorders that represent impaired timing of neural activity, often accompanied by problems understanding speech. Here, we measure timing properties of sound-evoked activity via the auditory brainstem response (ABR) of α7 nAChR knockout mice of both sexes and wild type colony controls. We find a significant timing delay in evoked ABR signals that represents midbrain activity in knockouts. We also examine spike-timing properties of neurons in the inferior colliculus, a midbrain nucleus that exhibits high levels of α7 nAChR during development. We find delays of evoked responses along with degraded spiking precision in knockout animals. We find similar timing deficits in responses of neurons in the superior paraolivary nucleus and ventral nucleus of the lateral lemniscus, which are brainstem nuclei thought to shape temporal precision in the midbrain. In addition, we find that other measures of temporal acuity including forward masking and gap detection are impaired for knockout animals. We conclude that altered temporal processing at the level of the brainstem in α7 nAChR-deficient mice may contribute to degraded spike-timing in the midbrain, which may underlie the observed timing delay in the ABR signals. Our findings are consistent with a role for the α7 nAChR in types of neurodevelopmental and auditory processing disorders and we identify potential neural targets for intervention.
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- Oculodentodigital Dysplasia: A Hypomyelinating Leukodystrophy with a Characteristic MRI Pattern of Brain Stem Involvement. [Journal Article]
- AAAJNR Am J Neuroradiol 2019; 40(5):903-907
- Oculodentodigital dysplasia, a rare genetic disorder caused by mutations in the gene encoding gap junction protein 1, classically presents with typical facial features, dental and ocular anomalies, a…
Oculodentodigital dysplasia, a rare genetic disorder caused by mutations in the gene encoding gap junction protein 1, classically presents with typical facial features, dental and ocular anomalies, and syndactyly. Oligosymptomatic patients are common and difficult to recognize, in particular if syndactyly is absent. Neurologic manifestation occurs in approximately 30% of patients, and leukodystrophy or T2 hypointensity of gray matter structures or both have been noted in individual patients. To investigate MR imaging changes in oculodentodigital dysplasia, we retrospectively and systematically reviewed 12 MRIs from 6 genetically confirmed patients. Diffuse supratentorial hypomyelination, T2-hypointense Rolandic and primary visual cortex, and symmetric involvement of middle cerebellar peduncle, pyramidal tract, and medial lemniscus was present in all, T2-hypointense pallidum and dentate nucleus in 2 patients each. This consistent, characteristic pattern of diffuse supratentorial hypomyelination and brain stem involvement differs from other hypomyelinating and nonhypomyelinating leukodystrophies with brain stem involvement, and its recognition should trigger genetic testing for oculodentodigital dysplasia.