Transsynaptic degeneration of lateral geniculate bodies in blind children: in vivo MR demonstration (original) (raw)
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Neuroradiology, 1998
MRI was used to study possible morphological changes in the visual system in 12 patients suffering from congenital blindness of peripheral (ocular) origin. While their optical pathways showed degeneration, hypoplasia or atrophy in 7 out of 12 cases, the occipital cortex appeared normal in all cases. This dissociation between afferent pathways and the cortex is contrary to the assumption that visually deprived cortex may undergo degeneration. The finding is congruent with evidence that the occipital cortex is used for other, nonvisual functions.
Congenital blindness affects diencephalic but not mesencephalic structures in the human brain
Brain Structure and Function, 2015
While there is ample evidence that the structure and function of visual cortical areas are affected by early visual deprivation, little is known of how early blindness modifies subcortical relay and association thalamic nuclei, as well as mesencephalic structures. Therefore, in the present multicenter study, we used MRI to measure volume of the superior and inferior colliculi, as well as of the thalamic nuclei relaying sensory and motor information to the neocortex, parcellated according to atlas-based thalamo-cortical connections, in 29 individuals with congenital blindness of peripheral origin (17 M, age 35.7 ± 14.3 years) and 29 sighted subjects (17 M, age 31.9 ± 9.0). Blind participants showed an overall volume reduction in the left (p = 0.008) and right (p = 0.007) thalami, as compared to the sighted individuals. Specifically, the lateral geniculate (i.e., primary visual thalamic relay nucleus) was 40 % reduced (left: p = 4 9 10-6 , right: p \ 1 9 10-6), consistent with findings from animal studies. In addition, associated thalamic nuclei that project to temporal (left: p = 0.005, right: p = 0.005), prefrontal (left: p = 0.010, right: p = 0.014), occipital (left: p = 0.005, right: p = 0.023), and right premotor (p = 0.024) cortical regions were also significantly reduced in the congenitally blind group. Conversely, volumes of the relay nuclei directly involved in auditory, motor, and somatosensory processing were not affected by visual deprivation. In contrast, no difference in volume was observed in either the superior or the inferior colliculus between the two groups. Our findings indicate that visual loss since birth leads to selective volumetric changes within diencephalic, but not mesencephalic, structures. Both changes in reciprocal cortico-thalamic connections or modifications in the intrinsic connectivity between relay and association nuclei of the thalamus may contribute to explain these alterations in thalamic volumes. Sparing of the superior colliculi is in line with their composite, multisensory projections, and with their not exclusive visual nature.
Role of MRI scanning in the diagnosis of cerebral visual disturbance
Pediatric Neurology, 1986
Visual dysfunction as part of cerebral palsy may be due to lesions of the retrochiasmatic visual pathways. Cranial computed tomography can reveal conspicuous and characteristic abnormalities in most patients presenting with the condition; however, in some patients the abnormalities may appear so subde on computed tomography that they can be easily overlooked or their true significance questioned. Magnetic resonance imaging has proved to be of great value in demonstrating the neuroanatomic anomalies underlying the visual handicap of this latter group of patients, allowing for early diagnosis and predse management.
Early diffusion evidence of retrograde transsynaptic degeneration in the human visual system
Neurology, 2016
Objective: We investigated whether diffusion tensor imaging (DTI) indices of white matter integrity would offer early markers of retrograde transsynaptic degeneration (RTD) in the visual system after stroke. Methods: We performed a prospective longitudinal analysis of the sensitivity of DTI markers of optic tract health in 12 patients with postsynaptic visual pathway stroke, 12 stroke controls, and 28 healthy controls. We examined group differences in (1) optic tract fractional anisotropy (FA-asymmetry), (2) perimetric measures of visual impairment, and (3) the relationship between FA-asymmetry and perimetric assessment. Results: FA-asymmetry was higher in patients with visual pathway lesions than in control groups. These differences were evident 3 months from the time of injury and did not change significantly at 12 months. Perimetric measures showed evidence of impairment in participants with visual pathway stroke but not in control groups. A significant association was observed between FA-asymmetry and perimetric measures at 3 months, which persisted at 12 months. Conclusions: DTI markers of RTD are apparent 3 months from the time of injury. This represents the earliest noninvasive evidence of RTD in any species. Furthermore, these measures associate with measures of visual impairment. DTI measures offer a reproducible, noninvasive, and sensitive method of investigating RTD and its role in visual impairment. Neurology ® 2016;87:1-8 GLOSSARY DTI 5 diffusion tensor imaging; FA 5 fractional anisotropy; HVFD 5 homonymous visual field defect; OCT 5 optical coherence tomography; OT 5 optic tract; RNFL 5 retinal nerve fiber layer; RTD 5 retrograde transsynaptic degeneration; TE 5 echo time; TR 5 repetition time; VF 5 visual field.
Alterations of the visual pathways in congenital blindness
Experimental Brain Research, 2008
We used whole brain MRI voxel-based morphometry (VBM) to study the anatomical organization of the visual system in congenitally blind (CB) adults. Eleven CB without a history of visual perception were compared with 21 age- and sex-matched normal-sighted controls (NS). CB showed significant atrophy of the geniculo-striate system, encompassing the optic nerves, the optic chiasm, the optic radiations and the primary visual cortex (BA17). The volume decrease in BA17 reached 25% in both hemispheres. The pulvinar and its projections to the associative visual areas were also dramatically altered, BA18/19 and the middle temporal cortex (MT) showing volume reductions of up to 20%. Additional significant white matter alterations were observed in the inferior longitudinal tract and in the posterior part of the corpus callosum, which links the visual areas of both hemispheres. Our data indicate that the afferent projections to the visual cortex in CB are largely atrophied. Despite the massive volume reductions in the occipital lobes, there is compelling evidence from the literature (reviewed in Noppeney 2007; Ptito and Kupers 2005) that blind subjects activate their visual cortex when performing tasks that involve somatosensory or auditory inputs, suggesting a reorganization of the neural pathways that transmit sensory information to the visual cortex.
Blindsight in children with congenital and acquired cerebral lesions
Cortex, 2013
Functional MRI Spatial vision Congenital brain lesion a b s t r a c t It has been shown that unconscious visual function can survive lesions to optical radiations and/or primary visual cortex (V1), a phenomenon termed "blindsight". Studies on animal models (cat and monkey) show that the age when the lesion occurs determines the extent of residual visual capacities. Much less is known about the functional and underlying neuronal repercussions of early cortical damage in humans. We measured sensitivity to several visual tasks in four children with congenital unilateral brain lesions that severely affected optic radiations, and in another group of three children with similar lesions, acquired in childhood. In two of the congenital patients, we measured blood oxygenation level dependent (BOLD) activity in response to stimulation of each visual field quadrants.
Bilateral Progressive Visual Loss in an Epileptic, Mentally Retarded Boy
Leber's hereditary optic neuropathy (LHON) is a maternally inherited, monosymptomatic disorder, characterized by severe central vision loss and optic atrophy that most frequently affects young men. The classic LHON phenotype is associated to three mitochondrial DNA mutations, mostly homoplasmic, in the Mt-ND4, Mt-ND6, and Mt-ND1 genes, encoding for complex I subunits of the mitochondrial respiratory chain. Rare cases have been described in the literature in association with variable central nervous system involvement in a syndromic form called LHON 'plus.' In the present study, we report the case of a 16-year-old boy with the 3460/ND1 mutation who presented with epilepsy, migraine, and mental retardation as nonophthalmic features. We also investigated his relatives who all had the 3460/ND1 mutation.
Impact of early brain lesions on the optic radiations in children with cerebral palsy
Frontiers in Neuroscience
Due to their early brain lesion, children with unilateral spastic cerebral palsy (USCP) present important changes in brain gray and white matter, often manifested by perturbed sensorimotor functions. We predicted that type and side of the lesion could influence the microstructure of white matter tracts. Using diffusion tensor imaging in 40 children with USCP, we investigated optic radiation (OR) characteristics: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). First, we compared the OR of the lesional and non-lesional hemisphere. Then we evaluated the impact of the brain lesion type (periventricular or cortico-subcortical) and side in the differences observed in the lesional and non-lesional OR. Additionally, we examined the relationship between OR characteristics and performance of a visuospatial attention task. We observed alterations in the OR of children with USCP on the lesional hemisphere compared with the non-lesional hemi...