Is Enough Attention Paid to Muscle Pain in CP?

So many in the survey have muscle pain as part of CP, we wonder that more has not been said about it. “In theory, there is no difference between theory and practice. But, in practice, there is.”

A recent article by Taira, et al in Acta Neurochir Suppl. 2006;99:61-3. “Fifteen year experience of intrathecal baclofen treatment in Japan” makes us wonder if the failure to discuss muscle pain is due to vocabulary problems, time shortage in the clinics, failure to take a good history, or a preoccupation with the dominant pain, burning dysesthesia.

Baclofen is generally used to relieve SPASTICITY following spinal cord inury. Baclofen is a GABA-B receptor agonist (mimic of GABA-B at the receptor). GABA B a pain inhibitor, so Baclofen theoretically should have benefit against pain. However, theory and practice sometimes diverge. Baclofen is administered with a mechanical pump intrathecally (into the spinal fluid), usually after a test dose to see if it is effective.

We must ask the question. Effective at WHAT? Spasticity, pain, or pathologic pain? If pathologic pain is benefited, which TYPES of central pain are responsive? Is it burning dysesthesia, lightning pains, pins and needles, visceral pain, or muscle pain??? This is a fair question to ask about a procedure which in the U.S. may cost $30,000 and is inherently invasive.

Taira, who has the viewpoint of a neurosurgeon, makes a good case for including Baclofen in the regimen for central pain, but he fails to split the central pains into items we can talk about. It is all well and good to speak of SCI pain, post stroke pain, MS pain, neuropathic pain, pathologic pain, nerve injury pain, or whatever; but, this is not specific. It would be helpful to know WHICH of the central pains baclofen performs best at. Being an antispasticity drug, it seems reasonable to describe WHICH of the CP muscle pains it affects.

If someone has muscle pain of central origin, then relaxing those cramps and tightenings and pullings would of course benefit the pain. MOST patients in the survey do have muscle pain to one degree or another.

Other than the classic by Beric in Muscle and Nerve, we have not seen any article address muscle pain specifically in CP. There is an IASP review by McHenry which speculates that the sensory arm of the gamma motor system (muscle spindle) may be involved. Dr. McHenry himself, considering certain research on the muscle spindle casting possible doubt on its participation in CP, has theorized concerning other mechanisms, and has written alternative viewpoints here to counterpoint his own prior proposals for an explanation. However, the literature is ignoring muscle pain more than it ever has.

Whatever the mechanism, MANY more CP patients have muscle pain than one would gather from the literature. Judging from the surveys which are part of the Wall/McHenry database, sixty percent of CP subjects have significant muscle pain. The “MS Hug” (seen in perhaps 40% of MS patients), a feeling of tightening around the chest wall, is actually one of the very earliest signs of MS, and is itself a type of central pain. There is a very high incidence of muscle pain in CP but almost nothing in the literature about this.

We are glad to see Taira promote what in his experience has been beneficial. We cannot help wondering, however, if he himself knows that he is treating a SLICE of the central pains. Rational therapy would include a good history from ALL central pain patients, with questioning about muscle pains. These patients could then be selected for, and baclofen considered.

It is very hard to take at face value a study showing baclofen plays a role in central pain, when there is insufficient evidence that clinical history was a guiding feature. Perhaps baclofen was one hundred percent effective in those with muscle pain and zero percent effective in those who did not have it.

We simply do not know, because muscular central pain, which should be split into several words, such as “kinesthetic dysesthesia”, “isometric dysesthesia”, “confinement cramps” “unusual fatigue”, etc. following the approach of Beric, is spoken of as ONE pain, and that one not separated from skin pain! Some doctors mistakenly believe that the malady causing the central pain is conclusive as to symptomatology or therapy. This would be another area where theory and practice do not agree. The surveys indicate that the specific symptom, not the causation, provides a better indicator of which therapy, if any, will be effective. It is true that knowing a pain comes from peripheral and not central nerve injury provides helpful guidance on therapy, but we are not discussing PNI pain in this article.

This makes it impossible to gain the full benefit from any study on central pain. Most articles do not even distinguish between spinothalamic pain and lemniscal pain, which is an essential part of the clinical history. One would anticipate virtually one hundred percent of lemniscal pain responding to baclofen and none of the spinothalamic pain responding. This study does not tell us whether we are right or wrong. If some ST pain DOES respond to baclofen, this would be a curiosity and we would like more information on those individual cases.

Central pain continues to wallow in a sea of vagaries, with neurosurgeons, probably very helpful, administering very expensive and invasive modalities without providing a careful history. Hopefully, a trend will develop to speak with precision, and treat according to data which reflects knowledge of the components of pain of central origin. Taira’s conclusions only point to the likelihood that a great many CP patients have muscle pains, even if they are not discussed in categorized fashion.

We thank Taira for highlighting the fact that baclofen can be helpful. It is hard enough to come up with any neurosurgeon who finds Central Pain to be interesting, and sometimes tough to find one who even believes it exists. Even some of the great ones seem to place central pain on a par with low back pain. Perhaps many doctors are used to hearing SCI patients discuss the many pains which can attend spine disorders without realizing the huge upgrade which is genuine central pain. This is not to minimize anyone’s mechanical pain, it is merely to repeat Riddoch’s assertion that central pain is a “pain beyond pain”. Thus, Taira wins our gratitude, admiration and approval. We trust his concern enough to add that we would like to see the central pains fleshed out, so those of us considering pumps can have some basis for making decisions on their helpfulness for us. His study is handicapped by the failure to specify which type of muscle pain in CP he was addressing. You take what you can get and Taira is definitely of help and on our side. Yet, we can’t help wondering if the data could not be refined further.

This is the classic problem faced by CP patients with their doctors. the patient has generally been brutalized by several doctors who were unfamiliar with CP before they see an expert. Then, when they finally do contact an expert, they have much to teach the professional, but the patient has no way ot knowing which pains are neuropathic and which are nociceptive and so there is no educating of the professional which permits future refinement. The medical profession must lead by drawing up some categories of the central pains, and attempting to assign what the patient is experiencing to those categories, and only then deciding which therapies are rationally directed.

We love the good neurosurgeons and neurologists who treat pain, but we need them to listen a little more closely and help us through our vocabularly difficulties. We realize it is tiresome to listen to pain complaints, and impossible to tell who is really in terrible shape, since pain will drive even the moderate cases to complain bitterly. As quickly as possible, imaging techniques must be developed to give some quantitative measure of pain to which the doctor can react scientifically rather than by intuition or pure guess about pain severity. However, the doctor must not only realize that central pain exists, but that it has divisional categories which should be kept in mind when designing, evaluating, and recommending therapies.