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Neuroimaging in children with neurofibromatosis type 1
834
Editorial correspondence
The Journal of Pediatrics May 1993
Reply To the Editor: We did compare the two groups of infants with respect to their birth weight, as mentioned in the Results section. There were no statistical differences (control group, 2899 • 562 gm; treatment group, 3119 • 546 gm); both groups contained only a few premature babies with, again, no statistical differences between them. We were well aware of the different management of premature babies, which can be recognized from Fig. 1. I Neither the treatment nor the control group contained very low birth weight babies, which is likely to differ in countries such as India. It would be of major interest ifa study similar to ours could be performed in India, where the incidence of both Rh hemolytic disease and prematurity is probably much higher than in Germany. The lgG levels in the infants in our study were not measured. However, because the birth weights did not differ among groups, we assumed that IgG levels were similar. Nevertheless, lgG levels are of interest because Kelton et al. 2 showed that IgG competes with immune complexes (and IgG-sensitized erythrocytes?) for macrophage Fc receptors in vivo, and thus might influence the clearance of sensitized erythrocytes. Future studies should take this into consideration. Our decisions for exchange transfusions were not based on a single determination of bilirubin levels. Fig. 2, in our publication, depicts only the last values before blood exchange.
differentiate progressive from nonprogressive tumors is poor. Progressive tumors are usually treated by radiation therapy or, more recently, chemotherapy. Although the treatments can be effective, they are potentially toxic and it is difficult to justify treatment of a symptom-free child solely on the basis of MRI findings. The benefit of early detection would tberefo1"e be identification of children who require very close clinical follow-up. Optic gliomas may grow very slowly, however, and therapy is generally initiated only when definite clinical signs of progression are noted. The decision to treat these potentially indolent tumors must be made very judiciously, and therefore the value of early MRI detection over the identification of children at risk by annual physical examination is unclear. Although MRI scanning is often viewed as being risk free, this is not always so. Children frequently are sedated for an MRI scan, and this conveys a small but real risk. The procedure itself can be an emotionally traumatic experience for an otherwise healthy child. The most common adverse effect of such scanning, however, can be the anxiety caused by a finding of unknown clinical significance, such as bright T2-weighted signals3 or thickening of the optic nerve. I believe that too much emphasis has been placed on the need for routine neuroimaging of symptom-free children with NF-I. Serious medical complications are not common in this population and, in my experience, can generally be detected clinically.
Volker Wahn, bid Department of Pediatrics University of Dusseldorf 4000 Dusseldorf Germany
Bruce R. Korf MD, PhD Director, Clinical Genetics Program Children's Hospital Assistant Professor of Neurology Harvard Medical School Boston, Massachusetts
9/3fi/45255
9/35/45754
REFERENCES i. Rfibo J, Albrecht K, Lasch P, et al. High-dose intravenous immune globulin therapy for hyperbilirubinemia caused by Rh hemolytic disease. J PEDIATR 1992;121:93-7. 2. Kelton JG, Singer J, Rodger C, et al. The concentration of lgG in the serum is a major determinant of Fc-dependent reticuloendothelial function. Blood 1985;66:490-5.
REFERENCES 1. Listernick R, Charrow J, Greenwald M. Emergence of optic pathway gliomas in children with neurofibromatosis type 1 after normal neuroimaging results. J PEDIA'rR 1992;121:584-7. 2. Easley JD, Scharf L, Chou JL, Riccardi VM. Controversy in the management of optic pathway gliomas. Neurofibromatosis 1988;1:248-51. 3. Sevick R J, Barkovich A J, Edwards MSB, Koch T, Berg B, Lempert T. Evolution of white matter lesions in neurofibromatosis type 1: MR findings. AJR Am J RoentgenoI 1992;159:171-5.
Neuroimaging in children with neurofibromatosis type 1
Reply
To the Editor:
To the Editor:
In their report on the emergence of optic gliomas, Listernick et al. 1 raise the question of the need for routine neuroimaging in patients with neurofibromatosis type 1 (NF-I). A decision to perform a screening study for a symptom-free individual should take account of the benefits and risks of screening and the predictive value of the test. The benefit of presymptomatic detection of optic glioma would be initiation of treatment before the onset of serious and potentially irreversible symptoms. Optic gliomas in NF-I can remain quiescent indefinitely or may be progressive.2 The predictive value of screening with magnetic resonance imaging (MRI) to
Although the utility of presymptomatic screening of children with neurofibromatosis type I (NF- 1) for optic pathway tumors has yet to be proved, a survey performed by us revealed that at least 33% of the NF clinical care centers are routinely performing neuroimaging. Arguments in favor of such screening include the following: 1. Optic gliomas may be present without any evidence of visual dysfunction. In our previous study of optic gliomas in an unbiased population of children with NF-I, definite abnormalities of vision were found in only 20% of the children at the time of diagnosis of the optic glioma by neuroimagingJ We are now in the process of
Editorial correspondence
The Journal of Pediatrics May 1993
Reply To the Editor: We did compare the two groups of infants with respect to their birth weight, as mentioned in the Results section. There were no statistical differences (control group, 2899 • 562 gm; treatment group, 3119 • 546 gm); both groups contained only a few premature babies with, again, no statistical differences between them. We were well aware of the different management of premature babies, which can be recognized from Fig. 1. I Neither the treatment nor the control group contained very low birth weight babies, which is likely to differ in countries such as India. It would be of major interest ifa study similar to ours could be performed in India, where the incidence of both Rh hemolytic disease and prematurity is probably much higher than in Germany. The lgG levels in the infants in our study were not measured. However, because the birth weights did not differ among groups, we assumed that IgG levels were similar. Nevertheless, lgG levels are of interest because Kelton et al. 2 showed that IgG competes with immune complexes (and IgG-sensitized erythrocytes?) for macrophage Fc receptors in vivo, and thus might influence the clearance of sensitized erythrocytes. Future studies should take this into consideration. Our decisions for exchange transfusions were not based on a single determination of bilirubin levels. Fig. 2, in our publication, depicts only the last values before blood exchange.
differentiate progressive from nonprogressive tumors is poor. Progressive tumors are usually treated by radiation therapy or, more recently, chemotherapy. Although the treatments can be effective, they are potentially toxic and it is difficult to justify treatment of a symptom-free child solely on the basis of MRI findings. The benefit of early detection would tberefo1"e be identification of children who require very close clinical follow-up. Optic gliomas may grow very slowly, however, and therapy is generally initiated only when definite clinical signs of progression are noted. The decision to treat these potentially indolent tumors must be made very judiciously, and therefore the value of early MRI detection over the identification of children at risk by annual physical examination is unclear. Although MRI scanning is often viewed as being risk free, this is not always so. Children frequently are sedated for an MRI scan, and this conveys a small but real risk. The procedure itself can be an emotionally traumatic experience for an otherwise healthy child. The most common adverse effect of such scanning, however, can be the anxiety caused by a finding of unknown clinical significance, such as bright T2-weighted signals3 or thickening of the optic nerve. I believe that too much emphasis has been placed on the need for routine neuroimaging of symptom-free children with NF-I. Serious medical complications are not common in this population and, in my experience, can generally be detected clinically.
Volker Wahn, bid Department of Pediatrics University of Dusseldorf 4000 Dusseldorf Germany
Bruce R. Korf MD, PhD Director, Clinical Genetics Program Children's Hospital Assistant Professor of Neurology Harvard Medical School Boston, Massachusetts
9/3fi/45255
9/35/45754
REFERENCES i. Rfibo J, Albrecht K, Lasch P, et al. High-dose intravenous immune globulin therapy for hyperbilirubinemia caused by Rh hemolytic disease. J PEDIATR 1992;121:93-7. 2. Kelton JG, Singer J, Rodger C, et al. The concentration of lgG in the serum is a major determinant of Fc-dependent reticuloendothelial function. Blood 1985;66:490-5.
REFERENCES 1. Listernick R, Charrow J, Greenwald M. Emergence of optic pathway gliomas in children with neurofibromatosis type 1 after normal neuroimaging results. J PEDIA'rR 1992;121:584-7. 2. Easley JD, Scharf L, Chou JL, Riccardi VM. Controversy in the management of optic pathway gliomas. Neurofibromatosis 1988;1:248-51. 3. Sevick R J, Barkovich A J, Edwards MSB, Koch T, Berg B, Lempert T. Evolution of white matter lesions in neurofibromatosis type 1: MR findings. AJR Am J RoentgenoI 1992;159:171-5.
Neuroimaging in children with neurofibromatosis type 1
Reply
To the Editor:
To the Editor:
In their report on the emergence of optic gliomas, Listernick et al. 1 raise the question of the need for routine neuroimaging in patients with neurofibromatosis type 1 (NF-I). A decision to perform a screening study for a symptom-free individual should take account of the benefits and risks of screening and the predictive value of the test. The benefit of presymptomatic detection of optic glioma would be initiation of treatment before the onset of serious and potentially irreversible symptoms. Optic gliomas in NF-I can remain quiescent indefinitely or may be progressive.2 The predictive value of screening with magnetic resonance imaging (MRI) to
Although the utility of presymptomatic screening of children with neurofibromatosis type I (NF- 1) for optic pathway tumors has yet to be proved, a survey performed by us revealed that at least 33% of the NF clinical care centers are routinely performing neuroimaging. Arguments in favor of such screening include the following: 1. Optic gliomas may be present without any evidence of visual dysfunction. In our previous study of optic gliomas in an unbiased population of children with NF-I, definite abnormalities of vision were found in only 20% of the children at the time of diagnosis of the optic glioma by neuroimagingJ We are now in the process of