Limits...
Magnetic resonance in studies of glaucoma.

Fiedorowicz M, Dyda W, Rejdak R, Grieb P - Med. Sci. Monit. (2011)

Bottom Line: These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density.Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye.Further applications of MR techniques in studies of glaucomatous brains are indicated.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Pharmacology, Polish Academy of Science Medical Research Centre, Warsaw, Poland. mfied@cmdik.pan.pl

ABSTRACT
Glaucoma is the second leading cause of blindness. It affects retinal ganglion cells and the optic nerve. However, there is emerging evidence that glaucoma also affects other components of the visual pathway and visual cortex. There is a need to employ new methods of in vivo brain evaluation to characterize these changes. Magnetic resonance (MR) techniques are well suited for this purpose. We review data on the MR evaluation of the visual pathway and the use of MR techniques in the study of glaucoma, both in humans and in animal models. These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density. Studies on rats employing manganese-enhanced MRI showed that axonal transport in the optic nerve is affected. Diffusion tensor MRI revealed signs of degeneration of the optic pathway. Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye. Magnetic resonance spectroscopy demonstrated changes in metabolite levels in the visual cortex in a rat model of glaucoma, although not in glaucoma patients. Further applications of MR techniques in studies of glaucomatous brains are indicated.

Show MeSH

Related in: MedlinePlus

(Top row) Illustration of the localization of the 4Ă—1Ă—4 mm3 voxels (solid-line boxes) in the glaucomatous (L) and control (R) rat visual cortex for 1H MRS. (Bottom row) Averaged spectra for single voxel 1H MRS on each side of the visual cortex. Note the apparently lower Cho signal (arrow) with respect to the Cr signal in the left glaucomatous visual cortex than in the right control visual cortex. (L: left; R: right; A: anterior; P: posterior.). Reprinted from Chan et al. [48]. Copyright (2009), with permission from Elsevier.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3539477&req=5

f3-medscimonit-17-10-ra227: (Top row) Illustration of the localization of the 4Ă—1Ă—4 mm3 voxels (solid-line boxes) in the glaucomatous (L) and control (R) rat visual cortex for 1H MRS. (Bottom row) Averaged spectra for single voxel 1H MRS on each side of the visual cortex. Note the apparently lower Cho signal (arrow) with respect to the Cr signal in the left glaucomatous visual cortex than in the right control visual cortex. (L: left; R: right; A: anterior; P: posterior.). Reprinted from Chan et al. [48]. Copyright (2009), with permission from Elsevier.

Mentions: Although 1H MRS has many potential clinical applications in the area of neurodegenerative diseases (eg, Parkinson’s [46], Alzheimer’s disease [38], and multiple sclerosis [47]), this technique has been rarely used in glaucoma studies. Chan et al. [48] recorded 1H MR spectra in a rat model of ocular hypertension induced by photocoagulation of episcleral and limbal veins with an argon laser. Six weeks after initiation of intraocular hypertension, they found decreased Cho/Cr ratio in the visual cortex suggestive of a dysfunction in the cholinergic system of the visual pathway (Figure 3). However, Boucard et al. [49] could not detect statistically significant differences of NAA, Cr and Cho resonance signals in patients with POAG compared to non-glaucomatous controls. Different results from the animal and human studies may reflect a difference between the acute animal models (where quick degeneration is observed) and prolonged degeneration in humans subjects.


Magnetic resonance in studies of glaucoma.

Fiedorowicz M, Dyda W, Rejdak R, Grieb P - Med. Sci. Monit. (2011)

(Top row) Illustration of the localization of the 4Ă—1Ă—4 mm3 voxels (solid-line boxes) in the glaucomatous (L) and control (R) rat visual cortex for 1H MRS. (Bottom row) Averaged spectra for single voxel 1H MRS on each side of the visual cortex. Note the apparently lower Cho signal (arrow) with respect to the Cr signal in the left glaucomatous visual cortex than in the right control visual cortex. (L: left; R: right; A: anterior; P: posterior.). Reprinted from Chan et al. [48]. Copyright (2009), with permission from Elsevier.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3539477&req=5

f3-medscimonit-17-10-ra227: (Top row) Illustration of the localization of the 4Ă—1Ă—4 mm3 voxels (solid-line boxes) in the glaucomatous (L) and control (R) rat visual cortex for 1H MRS. (Bottom row) Averaged spectra for single voxel 1H MRS on each side of the visual cortex. Note the apparently lower Cho signal (arrow) with respect to the Cr signal in the left glaucomatous visual cortex than in the right control visual cortex. (L: left; R: right; A: anterior; P: posterior.). Reprinted from Chan et al. [48]. Copyright (2009), with permission from Elsevier.
Mentions: Although 1H MRS has many potential clinical applications in the area of neurodegenerative diseases (eg, Parkinson’s [46], Alzheimer’s disease [38], and multiple sclerosis [47]), this technique has been rarely used in glaucoma studies. Chan et al. [48] recorded 1H MR spectra in a rat model of ocular hypertension induced by photocoagulation of episcleral and limbal veins with an argon laser. Six weeks after initiation of intraocular hypertension, they found decreased Cho/Cr ratio in the visual cortex suggestive of a dysfunction in the cholinergic system of the visual pathway (Figure 3). However, Boucard et al. [49] could not detect statistically significant differences of NAA, Cr and Cho resonance signals in patients with POAG compared to non-glaucomatous controls. Different results from the animal and human studies may reflect a difference between the acute animal models (where quick degeneration is observed) and prolonged degeneration in humans subjects.

Bottom Line: These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density.Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye.Further applications of MR techniques in studies of glaucomatous brains are indicated.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Pharmacology, Polish Academy of Science Medical Research Centre, Warsaw, Poland. mfied@cmdik.pan.pl

ABSTRACT
Glaucoma is the second leading cause of blindness. It affects retinal ganglion cells and the optic nerve. However, there is emerging evidence that glaucoma also affects other components of the visual pathway and visual cortex. There is a need to employ new methods of in vivo brain evaluation to characterize these changes. Magnetic resonance (MR) techniques are well suited for this purpose. We review data on the MR evaluation of the visual pathway and the use of MR techniques in the study of glaucoma, both in humans and in animal models. These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density. Studies on rats employing manganese-enhanced MRI showed that axonal transport in the optic nerve is affected. Diffusion tensor MRI revealed signs of degeneration of the optic pathway. Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye. Magnetic resonance spectroscopy demonstrated changes in metabolite levels in the visual cortex in a rat model of glaucoma, although not in glaucoma patients. Further applications of MR techniques in studies of glaucomatous brains are indicated.

Show MeSH
Related in: MedlinePlus