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Referred pain
Soft tissue lesions mostly refer pain in a distal direction ; the real cause of the referred pain can lie outside the painful region. Different factors affect the intensity and localisation of the referred pain. Referred pain can be segmental or extrasegmental (= typical for dura mater).
Referred pain (2)
Rules of referred pain :
RP does not cross the midline
A unilateral lesion can only cause unilateral pain.
Example : a unilateral sacroiliac arthritis or a facet joint lesion give rise to unilateral pain only. A central disc protrusion, with pressure against the dura mater and /or nerve root could cause central, unilateral or bilateral pain.
RP is mainly segmental
The pain is referred according to the embryological origin of each structure.
Any structure of C5-origin could cause pain in the C5-dermatome.
Example : a shoulder arthritis or bursitis, supraspinatus or infraspinatus tendinitis all provoke similar pain in the arm (forearm). Hence, it is important to know the embryological derivation of all structures and the maps of the dermatomes.
Reference occurs mainly in a distal direction
It is abnormal for a local distal lesion to refer pain mainly in a proximal direction.
Example : a shoulder tendinitis may give rise to a pain felt as far as the base of the thumb (C5-dermatome) ; a tendinous lesion at the wrist does not cause pain as far as the shoulder. Or : a sacroiliac arthritis (S1-S2) can cause pain as far as the heel, whereas the pain of a retrocalcanean bursitis would not reach the buttock.
Reference in a proximal direction is only slight.
The lesion does not necessarily lie in the painful area
Palpation of local tenderness, with no other confirming examination, has poor diagnostic value. It should always be connected with other data from the clinical examination.
Example : shoulder joint arthritis. The pain is felt in the C5-dermatome and not necessarily only at the top of the shoulder. (It has to be said that this depends upon the individual differences in dermatomic distribution.).
Many soft tissues can cause referred pain
There is no difference in pain quality and ability to refer pain between a muscular, tendinous, ligamentous or other soft tissue pain.
The pain can be felt anywhere in the dermatome, not necessarily in the entire dermatome
We should not be mislead by the fact that RP can be confined to one part of the dermatome only.
Example : osteoarthrosis at the hip joint (L3) : the pain can be felt at the groin and down the front of the thigh, or just at the knee, or just in the upper buttock, or at the front of the leg as far as the medial malleolus. Hence, a patient who complains about an anterior knee pain, may have a hip lesion instead of a knee lesion.
Discrepancies exist between dermatomes and myotomes
A muscular structure does not necessarily lie underneath its dermatome ; it needs to be pointed out that this fact does not necessarily has important clinical value.
Example :
supraspinatus tendinitis (C5) : the C5-dermatome ends at the base of the thumb, but there
are no C5-muscles beyond the elbow.
The thumb and index finger lie in the C6-dermatome but the muscles in the hand are of C8- and T1-origin.
The proximal end of the C5-dermatome is at the mid-deltoid area. The supra- and infra-
spinatus muscles are C5-structures.
(Part I, p1-4)
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