Acta Neurochir (2005) [Suppl] 92: 147–150 6 Springer-Verlag 2005
Printed in Austria
Myofascial pain mimicking radicular syndromes
E. Facco and F. Ceccherelli
Department of Pharmacology and Anesthesiology, University of Padua, Padua, Italy
Summary
Myofascial pain is very often underscored and misunderstood in clinical practice. In many cases the localization of myofascial pain may resemble other diseases, such as radicular syndromes (e.g., low back pain from herniated disc) and even diseases of internal or- gans (e.g., angina pectoris, bowel diseases or gynaecological distur- bances). In pain clinics one can routinely see patients with myofascial painful disorders showing a radicular topography and normal CT and MRI: as a consequence, when vertebral abnormalities are pres- ent on CT or MRI, it should be checked whether the cause of pain is radicular, myofascial, or both. On the other hand, the conventional approach to painful disorders may lead to errors and wrong diagno- sis, depending on several factors: a) pain is often considered a symp- tom of an organic disease; b) the diagnosis is usually directed to- wards the structural cause of pain only; c) the functional components of the su¤ering patient are underscored; d) the site of pain may introduce some bias. When the latter is concerned, it is usually ad- mitted that a neck pain may depend on muscle contraction (e.g. tor- ticollis), while such a cause is less commonly admitted for leg, where the attention is first directed towards the sciatic nerve; myofascial origin of pain is even less considered in abdominal or pelvic painful disorders, where patients with no structural detectable diseases are often considered as neurotic and referred to the psychiatrist. The reason for this topographical dependence of diagnosis lies in the conventional attitude to focus on the most relevant and frequent or- ganic diseases, thus introducing a bias with relevant epistemological implications.
Keywords: Myofascial pain; radicular syndrome; epistemological factor; pain diagnosis.
Introduction
Myofascial pain is very often underscored and mis- understood in clinical practice. In many cases the localization of myofascial pain may resemble other diseases, such as radicular syndromes (e.g., low back pain from herniated disc) and even diseases of internal organs (e.g., angina pectoris, bowel diseases or gynae- cological disturbances). In pain clinics one can rou- tinely see patients with myofascial painful disorders showing a radicular topography and normal CT and
MRI: as a consequence, when vertebral abnormalities are present on CT or MRI, it should be checked whether the cause of pain is radicular, myofascial, or both. On the other hand, the conventional approach to painful disorders may lead to errors and wrong di- agnosis, depending on several factors: a) pain is often considered a symptom of an organic disease; b) the di- agnosis is usually directed towards the structural cause of pain only; c) the functional components of the suf- fering patient are underscored; d) the site of pain may introduce some bias. When the latter is concerned, it is usually admitted that a neck pain may depend on muscle contraction (e.g. torticollis), while such a cause is less commonly admitted for leg, where the attention is first directed towards the sciatic nerve; myofascial origin of pain is even less considered in abdominal or pelvic painful disorders, where patients with no struc- tural detectable diseases are often considered as neu- rotic and referred to the psychiatrist. The reason for this topographical dependence of diagnosis lies in the conventional attitude to focus on the most relevant and frequent organic diseases, thus introducing a bias with relevant epistemological implications.
The crucial epistemological factor a¤ecting the di-
agnosis of pain in clinical practice is the so called rule
of ‘‘Occam Razor’’, or ‘‘Rule of Thrift’’ [2]: when a
phenomenon may depend on di¤erent causes, one is
inclined to choose the most evident or the preferred
one, skipping the others. This is routinely seen in pa-
tients with herniated disc and myofascial pain in the
lower limb, were many doctors perform the (wrong)
diagnosis relying on CT or MR only. Conversely, in
patients with pain resembling part of a radicular syn-
drome one should check whether myofascial compo-
nents are present, what is their role and whether the
structural abnormality is a cause or coincidence only.
Only this approach can avoid useless operations and disappointing surgical treatments of recurrent pain. In fact, failed surgery may depend on two main facts: a) the operation was correctly indicated and performed, but the apparently recurrent pain depends on new myofascial components; b) the operation was targeted to a coincident lesion in a patient with myofascial pain only.
The topic of myofascial syndromes resembling neurogenic in origin is quite a wide complex; here we can only recall the definition of neurogenic pain and shortly outline the essentials of myofascial pain, fo- cussing on the most relevant syndromes resembling those of radicular origin (for further details see [7, 8]).
Neurogenic pain
Neurogenic pain may be acute or chronic: the latter may be the result of properly operated vertebral lesions which had caused a lesion of spinal roots or cord.
Chronic neurogenic pain is defined as pain arising from dysfunction within the peripheral or central nervous system with the following features: a) free in- terval from the time of nerve injury to the onset of pain (usually 1–3 months); b) a structural lesion may not be detected; c) pain is usually burning; d) intermittent bursts of pain may be present; e) paresthesia and dys- esthesia, allodynia, hyperalgesia and/or hyperesthesia are usually present.
It is emphasized that paresthesia and dysesthesia, although essential features of neurogenic pain, may be found in myofascial pain too.
Fibromyalgia
Fibromyalgia is a chronic disorder of unknown origin characterized by bilateral musculoskeletal pain associated with tender points (TPs) in at least 11 of 18 anatomically defined positions [9] (Table 1). Most patients are women of 40–50 years of age. Trauma, surgery, infection and, mainly, psychological factors (such as insomnia, depression) and functional dis- orders of internal organs (such as colitis or urodynia) may be associated with fibromyalgia. Pain is wide- spread and seems to be related to a pain threshold lower than normal, probably depending on a nocicep- tive dysfunction.
There is a tendency to consider fibromyalgia and myofascial pain as two members of the same family with some overlapping [3, 4]: in fact, several patients
with fibromyalgia have both myofascial trigger points (MPTs) and TPs. Despite this, fibromyalgia is not a neurogenic pain disorder, it may be associated with allodynia and dysesthesia.
Myofascial pain
Myofascial pain includes a wide range of acute or chronic painful conditions, the features of which are the presence of MPTs in one or several muscles, pain, rigidity, weakness, spasms and/or autonomic abnor- malities. The symptoms are usually reported in areas far from the MPT. There is virtually a specific syn- drome for each muscle of the body. These syndromes are the most common cause of severe pain located in the head, neck, shoulder, arms, legs, thorax, and even abdomen: they are often misdiagnosed and thus taken for neuralgia, arthritis, radiculopathy, visceral dis- eases. Misdiagnosis may lead to wrong and unsuc- cessful therapies, even invasive (like surgery), which apparently leave pain intractable, thus frustrating the patient and giving rise to reactive depression. On the other hand, some patients with no detectable structural lesions are considered neurotic and are referred to the psychiatrist further worsening their frustration.
Several factors may yield myofascial pain such as psychological disorders, physical conditions, acute or repetitive trauma or microtrauma, cold or heat, stress, concurrent diseases, fatigue.
MPTs are discrete, focal, hyperirritable spots lo- cated in a taut band of skeletal muscle [6, 7]; They produce pain locally and in a referred pattern. The physical finding typically associated with an MPT is a hypersensitive bundle or nodule of muscle fiber with a consistency harder than normal where palpation elicits
Table 1. Anatomic locations of tender points in fibromyalgia syn- drome [9]
1–2 Suboccipital muscle insertion at the occiput 3–4 Anterior aspects of the intertrasverse spaces of C5-C7 5–6 Midpoint of the upper border of trapezius
7–8 Near the origin of supraspinatus above the spine of scapula
9–10 Upper surface of II rib, just lateral to the 2nd costochondral junction
11–12 2 cm distal to the epicondyle on the extensor muscle 13–14 Upper outer quadrants of buttocks in anterior fold of
muscle
15–16 Greater trochanter (posterior to the prominence) 17–18 Medial fat pad of the knee, proximal to the joint line
and condyle
148
E. Facco and F. Ceccherellipain directly over the a¤ected area and/or may cause radiation of pain toward a zone of reference and a local twitch response. Muscle dysfunction resulting from MPTs may lead to weakness and decreased range of motion; the decreased use of muscle sooner or later leads to overload and new MPTs in other muscles.
Pain often increases over night and on waking up, when the muscle shortens in resting conditions. Some- times MPTs may be associated with autonomic symp- toms (such as local vasoconstriction or vasodilation, lacrimation, local sweating, rhinitis), vertigo, tinnitus, visual disturbances. For example, an MPT in sterno- cleidomastoid muscle may yield a frontotemporal headache, associated with lacrimation, resembling an atypical cluster headache.
Patient’s su¤ering may be deeply a¤ected by emo- tional and cognitive aspects of pain experience, in- cluding its persistence, intractability and wrong diag-
nosis: the image of the persistent, intractable pain cause a reactive depression and leads to a vicious circle (Fig. 1), where pain and psychological malaise are the two facets of the same medal, calling for a holistic approach to the su¤ering patient.
Myofascial syndromes resembling radiculopathies Any muscle of the body may virtually cause a spe- cific myofascial syndrome. Pain in the neck, shoulder and arm and low back pain caused by MPTs may often resemble a radiculopathy, with a wide range of pictures (see [7, 8]); in this paper we briefly analyse only the most outstanding.
It is worth recalling once again that checking struc- tural vertebral lesions is of course an essential step but it is not enough and functional components of pain should be evaluated as well. In other words, pain in the leg does not always depend on sciatic radiculopathy, whatever the CT or MR finding, but may be caused by MPTs.
The most outstanding myofascial syndromes re- sembling radiculopathies are those caused by MPTs of pectoralis minor, scalene, serratus anterior, gluteus minimus and piriformis. Anyway, all other muscles of arm and leg may cause local pain in the areas of the suspected radiculopathy.
The pectoralis minor syndrome causes shoulder pain, which may irradiate along the arm simulating a radi- culopathy C
7-C
8(Fig. 2); furthermore, a contracted
Fig. 1. Relationship between chronic pain and depression
Fig. 2. Site of pain in the pectoralis minor syndrome (left) and in scalene syndrome (right)
Myofascial pain mimicking radicular syndromes
149
pectoralis minor may compress the axillary artery and the brachial plexus close to its insertion to coracoid process during arm abduction, thus adding a neuro- vascular syndrome to pain. When pain is irradiated toward the precordial region, the myofascial pain may be taken for angina pectoris: thus, according to the main symptoms, the patient may be referred to the neurologist, neurosurgeon or cardiologist.
In the scalene syndrome the pain is radiated to the radial part of the arm down to the I and II finger, sim- ulating a C
6radicular pain (Fig. 2). This is also true for the pectoralis minor syndrome, here one can su¤er from paresthesia, too when the contracted scalene compresses the brachial plexus.
The serratus anterior usually causes pain in the chest under the axilla, causing sometimes dyspnea, which increases during deep breaths. However, pain may ra- diate down the ulnar part of the arm, simulating a C
7- C
8radicular pain.
When low back pain is concerned, pain from gluteus minimus radiates down the posterior or lateral part of the leg and may reach the ankle: therefore, the site
of pain may simulate a radiculopathy L
4-L
5or L
5-S
1(Fig. 3). Pain may be severe, hampering both walking and resting in bed.
The piriformis may yield a pain radiating down the leg, which may be associated with paresthesia when the sciatic nerve is compressed by the contracted mus- cle, thus resembling low back pain from herniated disc.
In fact, in about 10–20% of cases the whole sciatic nerve or its peroneal component crosses the piriformis muscle and may be compressed by its contraction [1, 5].
In conclusion, the painful myofascial syndromes radiating to the arm or leg may look like radicular pain, calling for a careful di¤erential diagnosis, espe- cially when vertebral abnormalities are present on CT or MR: pain is a complex phenomenon includ- ing many functional implications, which cannot be detected by radiological investigations and involve the whole patient. A structural abnormality may be the cause of pain, but pain may not depend on structural lesions and in many instances only a multidisciplinary approach allows for a right diagnosis and treatment, thus avoiding useless and disappointing surgical treat- ments.
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Correspondence: Prof. Enrico Facco, Department of Pharmacol- ogy and Anesthesiology, University of Padua, via C. Battisti 267, 35121 Padova, Italy. e-mail: enrico.facco@unipd.it
Fig. 3. Site of pain in the gluteus minimus syndrome
