Guest guest Posted February 5, 2004 Report Share Posted February 5, 2004 I understood part of the question related to doing NF when a client has a metal plate in place of skull bone. This has been a question I’ve wondered about for awhile myself. Would there be any reason to suspect that the readings would be different if a site to be worked was right were the metal is. In other words, does more or less eeg energy come through the metal plate (as opposed to bone) and then would one have to interpret in light of this? For example, if a metal plate allows more eeg energy through, then there would seem to be a higher amplitude coming through, and appear to be a problem, when in reality all it could be is a factor of the plate. Or, conversely, if the plate allows less eeg energy to come through you’d have the opposite issue. Any thoughts on this? Or has anyone actually worked with a person with a plate? Wigton plate issues Gerald, No reason not to work around the area with the slow activity. It would probably be a good idea to try to gain some activation there before training down much of the fast activity. I imagine that you have high coherence in the fast activity as well; that often follows head injury. Pete Van Deusen BrainTrainer () 16246 SW 92nd Ave, Miami, FL 33157 305/321-1595 plate effects on NF I am working with a client who sustained a moderate TBI with impact occipitally but most of the injury to cerebral structures occurring frontally. He had a craniotomy in the right anterotemporal area, had a section of bone removed for a period of time, then reinserted. He also had a small plate inserted in this area. His assessment shows significant slow wave activity everywhere in the front. (Interestingly, he also shows excessive fast activity in the parietals and temporal areas, leading me to think his brain has been accommodating for the injury by moving its processing demands to more posterior structures). I am curious to know what the implications might be for neurofeedback in this situation. Should the area around the plate be avoided altogether, or might there still be something to gain by training down the slow wave activity in this area? Thanks for your help. Gerald Showalter Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 6, 2004 Report Share Posted February 6, 2004 Hi, et al. An electrically conductive plate will behave in a fairly specific way. By virture of being a conductor, all points on the plate will be at the same potential (voltage) all the time at EEG frequencies. The whole plate may move up and down in voltage, but all points on the plate will change voltage together. Said another way, there will not be any potential (voltage) differences between any points on the plate at any given instant. If we put an electrode " on top of " the plate, the electrode signal will be influenced by the plate. The plate will serve as a kind of averaging device, so our electrode will detect primarily the larger amplitude influences in the region near the plate. A lot will depend upon the size of the plate compared to the electrode. If the plate is much larger, then this averaging effect will be more profound. If they are of about the same size, the electrode will report some averaging directly " in front " of itself, but will also receive signals from tissue lying near (but outside) the metal edge. If the plate were large enough to enclose the whole brain, we would see no EEG outside that shell. One of our clients had a cerebral aneurism that was repaired using some type of needle-shaped metal device to pinch off the distended part of the blood vessel. The pin remains in place, but our client is so scared, there is no ongoing discussion about doing QEEG. This client now tolerates neurofeedback, but even that was a leap of faith. Dave Myer Boston Neurofeedback At 08:21 PM 2/5/2004 -0700, you wrote: I understood part of the question related to doing NF when a client has a metal plate in place of skull bone. This has been a question Ive wondered about for awhile myself. Would there be any reason to suspect that the readings would be different if a site to be worked was right were the metal is. In other words, does more or less eeg energy come through the metal plate (as opposed to bone) and then would one have to interpret in light of this? For example, if a metal plate allows more eeg energy through, then there would seem to be a higher amplitude coming through, and appear to be a problem, when in reality all it could be is a factor of the plate. Or, conversely, if the plate allows less eeg energy to come through youd have the opposite issue. Any thoughts on this? Or has anyone actually worked with a person with a plate? Wigton plate issues Gerald, No reason not to work around the area with the slow activity. It would probably be a good idea to try to gain some activation there before training down much of the fast activity. I imagine that you have high coherence in the fast activity as well; that often follows head injury. Pete Van Deusen BrainTrainer () 16246 SW 92nd Ave, Miami, FL 33157 305/321-1595 plate effects on NF I am working with a client who sustained a moderate TBI with impact occipitally but most of the injury to cerebral structures occurring frontally. He had a craniotomy in the right anterotemporal area, had a section of bone removed for a period of time, then reinserted. He also had a small plate inserted in this area. His assessment shows significant slow wave activity everywhere in the front. (Interestingly, he also shows excessive fast activity in the parietals and temporal areas, leading me to think his brain has been accommodating for the injury by moving its processing demands to more posterior structures). I am curious to know what the implications might be for neurofeedback in this situation. Should the area around the plate be avoided altogether, or might there still be something to gain by training down the slow wave activity in this area? Thanks for your help. Gerald Showalter Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 6, 2004 Report Share Posted February 6, 2004 Gerald, I think a plastic " plate " would be hard to detect. That is, it would have only very subtle effects even if we got real fussy about our measurements in the lab. At low frequencies where EEG waveforms live, essentially all electrically conductive materials would behave about the same way. This would include some esoteric stuff like some carbon fiber composites, aluminum, stainless steel, and titanium. Metals that react with water (e.g. sodium) are not included in this thought process. If you imagine holding a flashlight whose illumination is a cone projecting from the bulb, and imagine that you shine it on your client's head, there would be portions of the cortex that would be in the shadow of the metal plate. There would also be regions not in the shadow. The signal from the plate would be the average of all the cortical activity in the shadowed area; the EEG signal would all have to come from the regions illuminated by the flashlight. So, I would expect the plate signal to be mostly low frequencies, declining in frequency and amplitude as the plate got larger and larger. What may be pretty important, is that this perspective should be reversible. That would mean that it might be pretty difficult to train higher frequency activity using the plate as an intermediary for your electrode. I suspect you would make out better by placing your electrode near the edge of the plate. Dave Myer Boston Neurofeedback At 09:40 AM 2/6/2004 -0500, you wrote: Dave, and Pete, Thanks very much for your responses. I am also curious whether the type of plate might be an influencing factor, and to what extent. I believe my client's plate is titanium. I would think training over the plate with him might be substantially different than training over a plate constructed of a type of plastic, for instance. plate issues Gerald, No reason not to work around the area with the slow activity. It would probably be a good idea to try to gain some activation there before training down much of the fast activity. I imagine that you have high coherence in the fast activity as well; that often follows head injury. Pete Van Deusen BrainTrainer () 16246 SW 92nd Ave, Miami, FL 33157 305/321-1595 plate effects on NF I am working with a client who sustained a moderate TBI with impact occipitally but most of the injury to cerebral structures occurring frontally. He had a craniotomy in the right anterotemporal area, had a section of bone removed for a period of time, then reinserted. He also had a small plate inserted in this area. His assessment shows significant slow wave activity everywhere in the front. (Interestingly, he also shows excessive fast activity in the parietals and temporal areas, leading me to think his brain has been accommodating for the injury by moving its processing demands to more posterior structures). I am curious to know what the implications might be for neurofeedback in this situation. Should the area around the plate be avoided altogether, or might there still be something to gain by training down the slow wave activity in this area? Thanks for your help. Gerald Showalter Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 6, 2004 Report Share Posted February 6, 2004 Dave,Thanks for your response and helpful analogy. Will give your suggestion a try. Gerald plate issues Gerald, No reason not to work around the area with the slow activity. It would probably be a good idea to try to gain some activation there before training down much of the fast activity. I imagine that you have high coherence in the fast activity as well; that often follows head injury. Pete Van Deusen BrainTrainer () 16246 SW 92nd Ave, Miami, FL 33157 305/321-1595 plate effects on NF I am working with a client who sustained a moderate TBI with impact occipitally but most of the injury to cerebral structures occurring frontally. He had a craniotomy in the right anterotemporal area, had a section of bone removed for a period of time, then reinserted. He also had a small plate inserted in this area. His assessment shows significant slow wave activity everywhere in the front. (Interestingly, he also shows excessive fast activity in the parietals and temporal areas, leading me to think his brain has been accommodating for the injury by moving its processing demands to more posterior structures). I am curious to know what the implications might be for neurofeedback in this situation. Should the area around the plate be avoided altogether, or might there still be something to gain by training down the slow wave activity in this area? Thanks for your help. Gerald Showalter Quote Link to comment Share on other sites More sharing options...
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