Magnetic Resonance Imaging and Cerebrospinal Fluid Valves
http://www.100md.com
《新英格兰医药杂志》
To the Editor: We are concerned that Dr. Akbar and his colleagues, as reported in their letter to the editor (Sept. 29 issue),1 used explanted cerebrospinal fluid shunt valves in their study of the susceptibility of these valves to malfunctions when exposed to magnetic fields as part of a magnetic resonance imaging (MRI) examination. Explanted valves contain biomaterials that are likely to change properties once the valve is explanted, which could affect valve function.
The 12 explanted Codman-Medos valves, removed from June 1998 to May 2004, were kindly returned to us by Dr. Akbar and colleagues. The valves were placed in an ultrasonic bath for 15 minutes for cleaning. Programming of the 12 valves was then performed a minimum of five times for the 30, 100, 30, 200 sequence. Despite the reported findings that the valves were rendered nonfunctional (totally or partially), all 12 valves could be programmed to the desired setting with no difficulties.
On the basis of our observations and the information supplied by Dr. Akbar and his colleagues regarding the source and condition of the valves used in testing, we think that the random failures and the intermittencies of programming operations are attributable to the sporadic presence of debris in the valve mechanism.
Christophe Mauge, Ph.D.
Sean Lilienfeld, M.D.
Codman
Raynham, MA 02767
cmauge@dpyus.jnj.com
Drs. Mauge and Lilienfeld are employees of Codman, a Johnson & Johnson company, which is the manufacturer of the Codman-Medos valves.
References
Akbar M, Stippich C, Aschoff A. Magnetic resonance imaging and cerebrospinal fluid shunt valves. N Engl J Med 2005;353:1413-1414.
The authors reply: Performance testing with new valves represents an ideal but an unrealistic condition1,2: the protein biofilm that is omnipresent in vivo is missing. A testing model using new, protein-perfused valves may be superior, but there is no proven model. Explanted valves that have been cleaned and tested with a protein biofilm with full adjustability represent as closely as possible in vivo conditions.
Since 1987, 402 explanted and 346 new valves have been examined in our laboratory, which has been visited by several experts from Codman since 1990. Of these, 87 of the valves were adjustable Medos valves that had been removed at surgery, washed, disinfected, stored in distilled water, and tested according to international standards (ISO 7197).3,4 The valves studied had no visible damage or debris when viewed under a magnifying glass and were in perfect working order before MRI exposure.
After exposure to magnetic fields, the valves were sent to Codman. Their data showed that three of the six valves could not be adjusted with a commonly available less powerful programmer (83-3121) but could be adjusted with a programmer with a stronger magnet (82-3190; this programmer is not readily available at many sites).
Thus, MRI exposure can influence valve function and the cause of any malfunctioning is not as simple as Mauge and Lilienfeld suggest.
Michael Akbar, M.D.
Christoph Stippich, M.D., Ph.D.
Alfred Aschoff, M.D., Ph.D.
University of Heidelberg
69118 Heidelberg, Germany
michael.akbar@ok.uni-heidelberg.de
References
Inoue T, Kuzu Y, Ogasawara K, Ogawa A. Effect of 3-tesla magnetic resonance imaging on various pressure programmable shunt valves. J Neurosurg 2005;103:Suppl:163-165.
Aschoff A, Kremer P, Benesch C, Fruh K, Klank A, Kunze S. Overdrainage and shunt technology: a critical comparison of programmable, hydrostatic and variable-resistance valves and flow-reducing devices. Childs Nerv Syst 1995;11:193-202.
International standard: neurosurgical implants — sterile, single-use hydrocephalus shunts and components. ISO 7197: 1989 (E) TC150/SC3-N 86. Geneva: International Organization of Standardization, 1994.
Standard practice for evaluating and specifying implantable shunt assemblies for neurosurgical application. Proposed revision of standard draft. West Conshohocken, Pa.: American Society of Testing and Materials, 2000. (Document no. ASTM F647-94(2000).)
The 12 explanted Codman-Medos valves, removed from June 1998 to May 2004, were kindly returned to us by Dr. Akbar and colleagues. The valves were placed in an ultrasonic bath for 15 minutes for cleaning. Programming of the 12 valves was then performed a minimum of five times for the 30, 100, 30, 200 sequence. Despite the reported findings that the valves were rendered nonfunctional (totally or partially), all 12 valves could be programmed to the desired setting with no difficulties.
On the basis of our observations and the information supplied by Dr. Akbar and his colleagues regarding the source and condition of the valves used in testing, we think that the random failures and the intermittencies of programming operations are attributable to the sporadic presence of debris in the valve mechanism.
Christophe Mauge, Ph.D.
Sean Lilienfeld, M.D.
Codman
Raynham, MA 02767
cmauge@dpyus.jnj.com
Drs. Mauge and Lilienfeld are employees of Codman, a Johnson & Johnson company, which is the manufacturer of the Codman-Medos valves.
References
Akbar M, Stippich C, Aschoff A. Magnetic resonance imaging and cerebrospinal fluid shunt valves. N Engl J Med 2005;353:1413-1414.
The authors reply: Performance testing with new valves represents an ideal but an unrealistic condition1,2: the protein biofilm that is omnipresent in vivo is missing. A testing model using new, protein-perfused valves may be superior, but there is no proven model. Explanted valves that have been cleaned and tested with a protein biofilm with full adjustability represent as closely as possible in vivo conditions.
Since 1987, 402 explanted and 346 new valves have been examined in our laboratory, which has been visited by several experts from Codman since 1990. Of these, 87 of the valves were adjustable Medos valves that had been removed at surgery, washed, disinfected, stored in distilled water, and tested according to international standards (ISO 7197).3,4 The valves studied had no visible damage or debris when viewed under a magnifying glass and were in perfect working order before MRI exposure.
After exposure to magnetic fields, the valves were sent to Codman. Their data showed that three of the six valves could not be adjusted with a commonly available less powerful programmer (83-3121) but could be adjusted with a programmer with a stronger magnet (82-3190; this programmer is not readily available at many sites).
Thus, MRI exposure can influence valve function and the cause of any malfunctioning is not as simple as Mauge and Lilienfeld suggest.
Michael Akbar, M.D.
Christoph Stippich, M.D., Ph.D.
Alfred Aschoff, M.D., Ph.D.
University of Heidelberg
69118 Heidelberg, Germany
michael.akbar@ok.uni-heidelberg.de
References
Inoue T, Kuzu Y, Ogasawara K, Ogawa A. Effect of 3-tesla magnetic resonance imaging on various pressure programmable shunt valves. J Neurosurg 2005;103:Suppl:163-165.
Aschoff A, Kremer P, Benesch C, Fruh K, Klank A, Kunze S. Overdrainage and shunt technology: a critical comparison of programmable, hydrostatic and variable-resistance valves and flow-reducing devices. Childs Nerv Syst 1995;11:193-202.
International standard: neurosurgical implants — sterile, single-use hydrocephalus shunts and components. ISO 7197: 1989 (E) TC150/SC3-N 86. Geneva: International Organization of Standardization, 1994.
Standard practice for evaluating and specifying implantable shunt assemblies for neurosurgical application. Proposed revision of standard draft. West Conshohocken, Pa.: American Society of Testing and Materials, 2000. (Document no. ASTM F647-94(2000).)