Why isn’t there increased itching in Central Pain. Except for one possible exception, all of the itch patients have turned out to have peripheral neuropathy. There should be a matching condition in pain of central origin.
As we approach a thousand respondents to the survey, we find not a single person who has itching from injury to the Central Nervous System. This is more surprising than one might think. The reason is that the conventional viewpoint is that there is a continuum of sensations from touch to pain, with itch in between along with what are called metasensations, which is a nice way of saying the person cannot describe them. Itch is said to be one of the alarm sensations to prevent injury or damage. We question the notion of a continuum, based on the surveys.
Everyone has played the child’s game of “rock, paper, and scissors”. No matter what one chooses, something else has the potential to trump it. If there really is a continuum, what then has happened to the itching in nerve injury? It is common knowledge that scratching stops itching. How can this possibly be? If a continuum is the explanation, a noxious event such as scratching should upgrade the firing rate until pain is noted. Indeed, scratching a sensitized area does indeed cause increased pain. Thus, what is sensitized in Central Pain must NOT be sensitized in itching.
Thus, it simply cannot be that simple. If pain covers itch, why does loss of touch cause pain, such as we see in Central Pain, where the dysesthetic burning occurs only where there is diminution in the sense of touch.
it is also noted that opiates INCREASE itch, through disinhibition, which means opiates suppress pain inhibition pathways in the brain, yet we are talking about ITCH here. We are back to rock, paper, and scissors. The paradox is consistent since opiates also cause more pain by disinhibition in the brain, yet they increase itch. The reciprocal reactions are not clear, are not linked in an obvious fashion, and do not account for the pain where loss of touch comes from nerve injury. We think a better explanation would be found by abandoning the idea of a continuum, and thinking more along the “if…then” way of viewing sensation. Pain can take priority over other sensations, and claim whatever space touch vacates with nerve injury, in recruiting via the interneurons, but itch is not part of the pathways which carry burning pain. Other conclusions are possible but must explain why scratch relieves itching.
December 29th, 2005 at 12:02 am
I am not sure from what is written above what is being said. Here is my story: In April of 04, I was launched from a stopped jumping horse onto my head, breaking in four places my C1 vertebra. (Jefferson fx). I have been through a lot in the last year and 9 months and am still struggling. I have seen many doctors, and am currently under the care of a neurologist who seems disinterested and has a different theory each time I see him.
I also suffered a “significant traumatic brain injury”. I’ve dealt with lots of issues, but the physical ones which remain are that numbness you so aptly describe as being the Positive Negative, in my feet and palms of hands. They feel numb, but I can feel anything touched to them. And they are painful in a different way, a very deep and central way.
But itching is another thing, one of the most distressing things that I have. It is at once severe and intense. I do scratch, but it relieves it only momentarily, and then it goes into a deep, stabbing pain. I have learned from many syringomyelia patients online that they all, for the most part, experience this itching. I take a small amt of Benadryl for relief, and it does work. The itching is slightly present most of the time, and always intensifies in the evening and at bedtime, when I take the Benadryl.
The point I’m at now is I just had an MRI done again of the Cspine, and 2 xrays (flexion and the other). My neuro told me a month ago I had mild spinal injury. Now he feels that all of my sx are due to emotional issues. And has prescribed another neuro psych test. I know very strongly that I am emotionally better than ever, and that my sx are very physical and due to physical injury. I’m thinking now of requesting a new neurologist.
Please tell me if you see itching as a sx from sci. I would appreciate your feedback. And I want to comment that reading your articles so far is a wonderful thing for me. For the first time, I see someone describing what I have! And having compassion for it. Thank you from the bottom of my heart!
Virginia
Ed Note. One of the problems in central pain research is that the patient’s history is often so focused on pain, that peripheral issues, such as itching simply do not make it into the list of questions which gets asked. Unfortunately, we do not know the incidence of itching in central pain, and neither does anyone else. Most physicians treating patients with central pain would be quite surprised at the large number of exant symptoms which have never come up, partly because dysesthetic pain dominates the conversation, because the patient is struggling for the right verbal descriptor term, and to a great extent because the doctors today simply do not have the time in an office visit to tap much of what is going on. It is not unusual to find a neurologist who is unaware of atopoesthesia in CP, for example, although it is very common. Our list of questions for survey respondents is as extensive as any we are aware of the in the world, but it does not include a question on itching. We are dependent on comments such as this very important one from Virginia, in order to learn and to ask more questions.