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A magnetization transfer study of white matter in siblings of multiple sclerosis patients
JOURNAL
OF THE
NEUROLOGICAL SCIENCES
ELSEVIER
Journal
of NeurologicalSciences147(1997) 151-153
A magnetization transfer study of white matter in siblings of multiple sclerosis patients Massimo Filippi”‘“,
Adriana Campib, Gianvito Martinoc, Bruno Colombo”, Giancarlo Comi”
“Department of Neurology, Scientijic Institute Ospedale San Raffaele, University of Milan, Via Olgettina 60, 20132 Milan, Italy ‘Department of Neuroradiology, Scient$c Institute Ospedale San Raffaele, University of Milan, Via Olgettina 60, 20132 Milan, Italy ‘Department of Neuroimmunology, ScientiJic Institute Ospedale San Raffaele, University of Milan, Via Olgettina 60, 20132 Milan, Italy
Received3 June 1996;revised9 October1996;accepted20 October1996
Abstract In this study, we evaluated magnetization transfer ratio values in the brain white matter of siblings of multiple sclerosis (MS) patients and comparedthem to those obtained in sex- and age-matchednormal controls. No statistically significant difference was found between the two groups for all the white matter areasstudied (frontal and occipital lobes, centrum semiovale, periventricular white matter, internal capsule, genu and splenium of the corpus callosum). 0 1997 Elsevier Science B.V. Keywords:
Multiple sclerosis; Magnetization transfer; Familial risk
1. Introduction Population-based studies of multiple sclerosis (MS) have shown that increased familial risks range from 300fold for monozygotic twins to 20-40-fold for first degree relatives over the general population prevalence (Ebers et al., 1995). Recently, it has been demonstrated that the increased familial risk to develop MS is genetically determined without any effect of shared enviroment (Ebers et al., 1995). Although human-leukocyte-antigen genes are certainly implicated in the higher susceptibily risk of familial MS, the recent biochemical finding that myelin from MS brains is developmentally immature (Moscarello et al., 1994) suggests that an inherited myelin abnormality might also contribute to the genetic predisposition to MS. Magnetization transfer (MT) is a relatively new imaging technique based on the interactions between protons in a relatively free state and those in a restricted motion state. The difference of signal intensity without and with MT can be easily and reliably measured (Dousset et al., 1992) as a MT ratio (MTR) which indirectly indicates the integrity or *Correspondingauthor. Tel.: +0039 2 26432231;fax: +0039 2 26432335.
0 1997ElsevierScienceB.V.All rights reserved PI1 SOO22-510X(96)05322-1
0022-510X/97/$17.00
the damage of the macromolecular structure of cell membranes. In brain, the main macromolecular matrix consists of myelin, thus reduced MTRs in the white matter corresponds to myelin abnormalities (Dousset et al., 1995). Several authors (Dousset et al., 1992; Gass et al., 1994; Filippi et al., 199.5; Loevener et al., 1995) have demonstrated that MTR is reduced in the normal appearing-white matter (NAWM) of patients with MS, thus indicating the potential of this technique in detecting even subtle pathological changes. In this study, we investigated whether similar changes were detectable also in the brain white matter of siblings of patients with MS.
2. Patients and methods Fifteen siblings (10 women and 5 men; mean age+S.D. 3 1.725.4 years) of patients with clinically definite MS (8 women and 7 men; mean age?S.D. 33.526.3 years; median duration of the disease 4.5 years, range l-15 years; median Expanded Disability Status Scale (EDSS) (Kurtzke, 1983) score 3.5, range 1.0-5.0; 12 with a relapsing-remitting and 3 with a secondary-progressive
152
M. Filippi et al. I Journal of Neurological
course of the disease) and 12 age- and sex-matched healthy controls (8 women and 4 men; mean age&SD 31.4k5.2 years) entered the study. At the time MT imaging was performed, a detailed clinical history, a full neurological examination and a conventional magnetic resonance imaging (MRI) were obtained. To be included siblings and controls had to have no previous history of neurological deficits and normal neurological examination and conventional MRI scan. MTRs were performed on a 1.5 Tesla machine. First, proton density and T,-weighted SE images of the brain were acquired (TR/TE 2300/40,80; 5 mm contiguous axial slices; matrix 256X256, FOV 230 mm) to exclude the presence of any asymptomatic white matter lesion. MT imaging studies were performed by obtaining 2D GE images (TR/TE 600/12; slice thickness 5mm with an interslice gap 2mm; matrix 192X256) with and without a saturation pulse. The saturation pulse had the following parameters: off-resonance gaussian RF pulse centered 1.5 kHz below the water frequency, with a duration of 16.384 ms, a bandwidth of 250 Hz and a power intensity of 3.4X10e6 Tesla. From the two images, i.e. without (MO) and with (MS) saturation pulse, quantitative MTR images were derived pixel-by-pixel according to the following equation: MTR=(Mo-Ms)/MoX 100, in which MO is the mean signal intensity for a given region without the saturation pulse and MS is the mean signal intensity for the same region when the saturation pulse is applied. MTR were calculated from a 22-mm2 regions of interest (ROI) placed in 14 different locations in the supratentorial white matter (bilaterally in the frontal and occipital lobes, centrum semiovale, periventricular white matter, internal capsule, genu and splenium of the corpus callosum). To minimize volume-averaging artifacts, white matter distant to gray matter and cerebra-spinal fluid was selected by one of us (MF), unaware to which group the subjects belonged. A comparison of whole brain white matter mean MTRs and of MTRs in each of the 14 regions of white matter as identified previously was made between siblings and controls by the Student’s t-test. In the latter case, the mean MTRs obtain from the two bilateral measurements entered the analysis.
Sciences 147 (1997) 151-153
3. Results The mean (2S.D.) whole brain white matter MTR was 50.6 (f 1.O) for the healthy subjects and 50.6 (?. 1.1) for the siblings of patients with MS. The mean MTRs (+S.D.) in each specific location of the white matter for the two groups of subjects are presented in Table 1. In both groups, the genu of the corpus callosum, the splenium of the corpus callosum and the frontal lobe white matter had the highest values. No statistically significant difference was found between the siblings of the patients with MS and the healthy controls for all the white matter areas studied.
4. Discussion The increased risk to develop MS if there are affected family members seems to be exclusively due to genetic determinants (Ebers et al., 1995). The recent reports indicating that myelin is developmentally immature in MS population (Moscarello et al., 1994) and the NAWM of MS patients presents reduced MTR values (Dousset et al., 1992; Gass et al., 1994; Filippi et al., 1995; Loevener et al., 1995) suggest that myelin genes coding for a more fragile myelin can be, at least partially, implicated in the genetic-based familial predisposition to MS. An inherited altered myelin might represent the ideal target for the ‘putative’ MS agent able to ignite an immune-mediated processes leading to demyelination. We found no difference in the MTR of white matter of siblings of MS patients and of healthy volunteers. These results are supported by the absence of polimorphisms of two of the major myelin component genes (myelin basic protein Rose et al., 1993, and myelin oligodendrocytic glycoprotein Roth et al., 1995), but are in apparent contrast with the biochemical findings on myelin composition found by Moscarello et al. (1994). However, it is clear that changes in MTR, which measures bulk effects between the total pools of bound and free protons, cannot detect such subtle myelin organization changes, albeit immunopathologically relevant. On the other hand, such biochemi-
Table 1 Mean MTR values (2S.D.) in different white matter regions in siblings of patients with MS and in healthy controls Location
Mean MTR (2S.D.) in siblings (%)
Mean MTR (2S.D.) in control subjects (%)
Frontal white matter Occipital white matter Centrum semiovale Periventricular white matter Internal ‘capsule Genu of corpus callosum Splenium of corpus callosum
51.0 49.6 49.4 50.1 49.7 52.7 51.5
51.1 49.9 48.9 49.8 50.2 52.4 51.6
(0.9) (1.3) (0.8) (1.4) (0.8) (1.4) (1.3)
(1.0) (0.9) (0.9) (1.2) (0.6) (1.3) (1.4)
M. Filippi
et al. I Journal
of Neurological
cal abnormalities might be relevant for the development of early structural myelin abnormalities, potentially detectable by MR techniques. Therefore, our results suggest that, if present, these early structural white matter changes in siblings of MS patients remain below the resolution of in vivo imaging techniques. Further information to this respect should be obtained by studies evaluating MT characteristics of white matter of concordant and discordant monozygotic twins. The total absence of any MT abnormality of the white matter of siblings of patients with MS also confirms that microscopic changes within the NAWM of MS patients, detectable using different MR techniques (Dousset et al., 1992; Barbosa et al., 1994; Gass et al., 1994; Filippi et al., 1995; Loevener et al., 1995), are secondary to a pathological damage which is much more widespread than that detectable using conventional MR techniques.
Acknowledgments We would like to thank Dr. Vincent Dousset (Department of Neuroradiology, CHR University of Bordeaux, France) for providing the sequences for MT imaging, Dr. Mark A. Horsfield (Department of Medical Physics, University of Leicester, .UK) for providing the software for obtaining quantitative MTR images and Mr. Clodoaldo Pereira (Department of Neuroradiology, Scientific Institute Ospedale San Raffaele, University of Milan, Italy) for his skillful technical assistance.
References Barbosa, S., Blumhardt, L.D., Roberts, N., Lock, T. and Edwards, R.T.H. (1994) Magnetic resonance relaxation time mapping in multiple
Sciences
147 (1997)
1.5-153
1.53
sclerosis: normal appearing white matter and the ‘invisible’ lesion load. Magn. Reson. Imaging, 12: 33-42. Dousset, V., Grossman, RI., Ramer, K.N., Schnall, M.D., Young, L.H., Gonzales-Scarano, F., Lavi, E. and Cohen, J.A. (1992) Experimental allergic encephalomyelitis and multiple sclerosis: lesion characterization with magnetization transfer imaging. Radiology, 182: 483-491. Dousset, V., Brochet, B., Vital, A., Gross, C., Benazzouz, A., Boulleme, A., Bidabe, A.M., Gin, A.M. and Caille, J.M. (1995) Lysolecithininduced demyelination in primates: preliminary in vivo study with MR and magnetization transfer. Am. J. Neurol. Res., 16: 225-231. Ebers, G.C., Sadovnick, A.D., Risch, N.J. and the Canadian Collaborative Study Group (1995) A genetic basis for familial aggregation in multiple sclerosis. Nature, 377: 150- 15 I, Filippi, M., Campi, A., Dousset, V, Baratti, C., Martinelli, V., Canal, N., Scotti, G. and Comi, G. (1995) A magnetization transfer imaging study of normal-appearing white matter in multiple sclerosis. Neurology, 45: 478-482. Gass, A., Barker, G.J., Kidd, D., Thorpe, J.W., MacManus, D.G., Brennan, A., Tofts P.S., Thompson, A.J., McDonald, WI. and Miller, D.H. (1994) Correlation of magnetization transfer ratio with clinical disability in multiple sclerosis. Ann. Neurol., 36: 62-67. Kurtzke, J.F. (1983) Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS). Neurology, 33: 14441452. Loevener, L.A., Grossman, RI., Cohen, J.A., Lexa, F.J., Kessler, D. and Kolson, D.L. (1995) Microscopic disease in normal-appearing white matter on conventional MR images in patients with multiple sclerosis: assessment with magnetization measurements. Am. J. Neurol. Res., 196: 51 I-515. Moscarello, M.A., Wood, D.D., Ackerley, C. and Boulias, C. (1994) Myelin in multiple sclerosis is developmentally immature. J. Clin. Invest., 94: 146-154. Rose, J., Gerken, S., Lynch, S., Pisani, P., Varvil, T., Offemd, B. and Leppert, B. (1993) Genetic susceptibility in familial multiple sclerosis not linked to the myelin basic protein gene. Lancet, 341: 1179-I 181. Roth, M.P., Dolbois, L. and Borot, N. (1995) Myelin oligodendrocytic glycoprotein (MOG) gene polymorphisms and multiple sclerosis: no evidence of disease association with MOG. J. Neuroimmunol., 61: 117-122.
OF THE
NEUROLOGICAL SCIENCES
ELSEVIER
Journal
of NeurologicalSciences147(1997) 151-153
A magnetization transfer study of white matter in siblings of multiple sclerosis patients Massimo Filippi”‘“,
Adriana Campib, Gianvito Martinoc, Bruno Colombo”, Giancarlo Comi”
“Department of Neurology, Scientijic Institute Ospedale San Raffaele, University of Milan, Via Olgettina 60, 20132 Milan, Italy ‘Department of Neuroradiology, Scient$c Institute Ospedale San Raffaele, University of Milan, Via Olgettina 60, 20132 Milan, Italy ‘Department of Neuroimmunology, ScientiJic Institute Ospedale San Raffaele, University of Milan, Via Olgettina 60, 20132 Milan, Italy
Received3 June 1996;revised9 October1996;accepted20 October1996
Abstract In this study, we evaluated magnetization transfer ratio values in the brain white matter of siblings of multiple sclerosis (MS) patients and comparedthem to those obtained in sex- and age-matchednormal controls. No statistically significant difference was found between the two groups for all the white matter areasstudied (frontal and occipital lobes, centrum semiovale, periventricular white matter, internal capsule, genu and splenium of the corpus callosum). 0 1997 Elsevier Science B.V. Keywords:
Multiple sclerosis; Magnetization transfer; Familial risk
1. Introduction Population-based studies of multiple sclerosis (MS) have shown that increased familial risks range from 300fold for monozygotic twins to 20-40-fold for first degree relatives over the general population prevalence (Ebers et al., 1995). Recently, it has been demonstrated that the increased familial risk to develop MS is genetically determined without any effect of shared enviroment (Ebers et al., 1995). Although human-leukocyte-antigen genes are certainly implicated in the higher susceptibily risk of familial MS, the recent biochemical finding that myelin from MS brains is developmentally immature (Moscarello et al., 1994) suggests that an inherited myelin abnormality might also contribute to the genetic predisposition to MS. Magnetization transfer (MT) is a relatively new imaging technique based on the interactions between protons in a relatively free state and those in a restricted motion state. The difference of signal intensity without and with MT can be easily and reliably measured (Dousset et al., 1992) as a MT ratio (MTR) which indirectly indicates the integrity or *Correspondingauthor. Tel.: +0039 2 26432231;fax: +0039 2 26432335.
0 1997ElsevierScienceB.V.All rights reserved PI1 SOO22-510X(96)05322-1
0022-510X/97/$17.00
the damage of the macromolecular structure of cell membranes. In brain, the main macromolecular matrix consists of myelin, thus reduced MTRs in the white matter corresponds to myelin abnormalities (Dousset et al., 1995). Several authors (Dousset et al., 1992; Gass et al., 1994; Filippi et al., 199.5; Loevener et al., 1995) have demonstrated that MTR is reduced in the normal appearing-white matter (NAWM) of patients with MS, thus indicating the potential of this technique in detecting even subtle pathological changes. In this study, we investigated whether similar changes were detectable also in the brain white matter of siblings of patients with MS.
2. Patients and methods Fifteen siblings (10 women and 5 men; mean age+S.D. 3 1.725.4 years) of patients with clinically definite MS (8 women and 7 men; mean age?S.D. 33.526.3 years; median duration of the disease 4.5 years, range l-15 years; median Expanded Disability Status Scale (EDSS) (Kurtzke, 1983) score 3.5, range 1.0-5.0; 12 with a relapsing-remitting and 3 with a secondary-progressive
152
M. Filippi et al. I Journal of Neurological
course of the disease) and 12 age- and sex-matched healthy controls (8 women and 4 men; mean age&SD 31.4k5.2 years) entered the study. At the time MT imaging was performed, a detailed clinical history, a full neurological examination and a conventional magnetic resonance imaging (MRI) were obtained. To be included siblings and controls had to have no previous history of neurological deficits and normal neurological examination and conventional MRI scan. MTRs were performed on a 1.5 Tesla machine. First, proton density and T,-weighted SE images of the brain were acquired (TR/TE 2300/40,80; 5 mm contiguous axial slices; matrix 256X256, FOV 230 mm) to exclude the presence of any asymptomatic white matter lesion. MT imaging studies were performed by obtaining 2D GE images (TR/TE 600/12; slice thickness 5mm with an interslice gap 2mm; matrix 192X256) with and without a saturation pulse. The saturation pulse had the following parameters: off-resonance gaussian RF pulse centered 1.5 kHz below the water frequency, with a duration of 16.384 ms, a bandwidth of 250 Hz and a power intensity of 3.4X10e6 Tesla. From the two images, i.e. without (MO) and with (MS) saturation pulse, quantitative MTR images were derived pixel-by-pixel according to the following equation: MTR=(Mo-Ms)/MoX 100, in which MO is the mean signal intensity for a given region without the saturation pulse and MS is the mean signal intensity for the same region when the saturation pulse is applied. MTR were calculated from a 22-mm2 regions of interest (ROI) placed in 14 different locations in the supratentorial white matter (bilaterally in the frontal and occipital lobes, centrum semiovale, periventricular white matter, internal capsule, genu and splenium of the corpus callosum). To minimize volume-averaging artifacts, white matter distant to gray matter and cerebra-spinal fluid was selected by one of us (MF), unaware to which group the subjects belonged. A comparison of whole brain white matter mean MTRs and of MTRs in each of the 14 regions of white matter as identified previously was made between siblings and controls by the Student’s t-test. In the latter case, the mean MTRs obtain from the two bilateral measurements entered the analysis.
Sciences 147 (1997) 151-153
3. Results The mean (2S.D.) whole brain white matter MTR was 50.6 (f 1.O) for the healthy subjects and 50.6 (?. 1.1) for the siblings of patients with MS. The mean MTRs (+S.D.) in each specific location of the white matter for the two groups of subjects are presented in Table 1. In both groups, the genu of the corpus callosum, the splenium of the corpus callosum and the frontal lobe white matter had the highest values. No statistically significant difference was found between the siblings of the patients with MS and the healthy controls for all the white matter areas studied.
4. Discussion The increased risk to develop MS if there are affected family members seems to be exclusively due to genetic determinants (Ebers et al., 1995). The recent reports indicating that myelin is developmentally immature in MS population (Moscarello et al., 1994) and the NAWM of MS patients presents reduced MTR values (Dousset et al., 1992; Gass et al., 1994; Filippi et al., 1995; Loevener et al., 1995) suggest that myelin genes coding for a more fragile myelin can be, at least partially, implicated in the genetic-based familial predisposition to MS. An inherited altered myelin might represent the ideal target for the ‘putative’ MS agent able to ignite an immune-mediated processes leading to demyelination. We found no difference in the MTR of white matter of siblings of MS patients and of healthy volunteers. These results are supported by the absence of polimorphisms of two of the major myelin component genes (myelin basic protein Rose et al., 1993, and myelin oligodendrocytic glycoprotein Roth et al., 1995), but are in apparent contrast with the biochemical findings on myelin composition found by Moscarello et al. (1994). However, it is clear that changes in MTR, which measures bulk effects between the total pools of bound and free protons, cannot detect such subtle myelin organization changes, albeit immunopathologically relevant. On the other hand, such biochemi-
Table 1 Mean MTR values (2S.D.) in different white matter regions in siblings of patients with MS and in healthy controls Location
Mean MTR (2S.D.) in siblings (%)
Mean MTR (2S.D.) in control subjects (%)
Frontal white matter Occipital white matter Centrum semiovale Periventricular white matter Internal ‘capsule Genu of corpus callosum Splenium of corpus callosum
51.0 49.6 49.4 50.1 49.7 52.7 51.5
51.1 49.9 48.9 49.8 50.2 52.4 51.6
(0.9) (1.3) (0.8) (1.4) (0.8) (1.4) (1.3)
(1.0) (0.9) (0.9) (1.2) (0.6) (1.3) (1.4)
M. Filippi
et al. I Journal
of Neurological
cal abnormalities might be relevant for the development of early structural myelin abnormalities, potentially detectable by MR techniques. Therefore, our results suggest that, if present, these early structural white matter changes in siblings of MS patients remain below the resolution of in vivo imaging techniques. Further information to this respect should be obtained by studies evaluating MT characteristics of white matter of concordant and discordant monozygotic twins. The total absence of any MT abnormality of the white matter of siblings of patients with MS also confirms that microscopic changes within the NAWM of MS patients, detectable using different MR techniques (Dousset et al., 1992; Barbosa et al., 1994; Gass et al., 1994; Filippi et al., 1995; Loevener et al., 1995), are secondary to a pathological damage which is much more widespread than that detectable using conventional MR techniques.
Acknowledgments We would like to thank Dr. Vincent Dousset (Department of Neuroradiology, CHR University of Bordeaux, France) for providing the sequences for MT imaging, Dr. Mark A. Horsfield (Department of Medical Physics, University of Leicester, .UK) for providing the software for obtaining quantitative MTR images and Mr. Clodoaldo Pereira (Department of Neuroradiology, Scientific Institute Ospedale San Raffaele, University of Milan, Italy) for his skillful technical assistance.
References Barbosa, S., Blumhardt, L.D., Roberts, N., Lock, T. and Edwards, R.T.H. (1994) Magnetic resonance relaxation time mapping in multiple
Sciences
147 (1997)
1.5-153
1.53
sclerosis: normal appearing white matter and the ‘invisible’ lesion load. Magn. Reson. Imaging, 12: 33-42. Dousset, V., Grossman, RI., Ramer, K.N., Schnall, M.D., Young, L.H., Gonzales-Scarano, F., Lavi, E. and Cohen, J.A. (1992) Experimental allergic encephalomyelitis and multiple sclerosis: lesion characterization with magnetization transfer imaging. Radiology, 182: 483-491. Dousset, V., Brochet, B., Vital, A., Gross, C., Benazzouz, A., Boulleme, A., Bidabe, A.M., Gin, A.M. and Caille, J.M. (1995) Lysolecithininduced demyelination in primates: preliminary in vivo study with MR and magnetization transfer. Am. J. Neurol. Res., 16: 225-231. Ebers, G.C., Sadovnick, A.D., Risch, N.J. and the Canadian Collaborative Study Group (1995) A genetic basis for familial aggregation in multiple sclerosis. Nature, 377: 150- 15 I, Filippi, M., Campi, A., Dousset, V, Baratti, C., Martinelli, V., Canal, N., Scotti, G. and Comi, G. (1995) A magnetization transfer imaging study of normal-appearing white matter in multiple sclerosis. Neurology, 45: 478-482. Gass, A., Barker, G.J., Kidd, D., Thorpe, J.W., MacManus, D.G., Brennan, A., Tofts P.S., Thompson, A.J., McDonald, WI. and Miller, D.H. (1994) Correlation of magnetization transfer ratio with clinical disability in multiple sclerosis. Ann. Neurol., 36: 62-67. Kurtzke, J.F. (1983) Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS). Neurology, 33: 14441452. Loevener, L.A., Grossman, RI., Cohen, J.A., Lexa, F.J., Kessler, D. and Kolson, D.L. (1995) Microscopic disease in normal-appearing white matter on conventional MR images in patients with multiple sclerosis: assessment with magnetization measurements. Am. J. Neurol. Res., 196: 51 I-515. Moscarello, M.A., Wood, D.D., Ackerley, C. and Boulias, C. (1994) Myelin in multiple sclerosis is developmentally immature. J. Clin. Invest., 94: 146-154. Rose, J., Gerken, S., Lynch, S., Pisani, P., Varvil, T., Offemd, B. and Leppert, B. (1993) Genetic susceptibility in familial multiple sclerosis not linked to the myelin basic protein gene. Lancet, 341: 1179-I 181. Roth, M.P., Dolbois, L. and Borot, N. (1995) Myelin oligodendrocytic glycoprotein (MOG) gene polymorphisms and multiple sclerosis: no evidence of disease association with MOG. J. Neuroimmunol., 61: 117-122.