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Pain processes in tennis elbow shown by PET scanning

By 11th February 2014No Comments

Physiological processes in
soft tissue pain such as chronic tennis elbow can be explored using diagnostic
imaging methods. This is demonstrated by researchers from Uppsala University in
Sweden; the results have recently been published (
Peterson M et al. PET-Scan Shows
Peripherally Increased Neurokinin 1 Receptor Availability in Chronic Tennis
Elbow: Visualizing Neurogenic Inflammation? PLoS ONE 8(10): e75859. doi:10.1371
). The work involved use of PET and a
tracer for the signal receptor NK1 for visualizing a physiological process
associated with pain. Musculoskeletal pain is the most common type of pain and
is one of the most common reasons for consultation in health care. However,
there are still very few effective methods for the localization and diagnosis
of the underlying pathophysiological mechanisms in pain from soft tissues,
(e.g. pain from muscles, tendons and ligaments). This means that diagnosis
still depends on clinical examination, which provides no guidance regarding
what mechanisms might underlie the pain. Consequently, treatment proceeds
purely on an empirical basis. An improved diagnostic method that allows not only
diagnosis of localization of the painful tissue processes, but also can provide
guidance regarding what pathophysiological mechanisms are involved, would
therefore be highly valuable.


The Swedish team injected a
PET tracer specific for NK1 receptors into the blood where it circulates
through the body and binds to available NK1 receptors. The study clearly
reveals an image of elevated levels of NK1 in the painful area compared with
the healthy arm. This is the first time an up-regulation of NK1 receptors has
been visualized by diagnostic imaging in painful tissue in humans. Following
tissue damage there is an up-regulation of the neuropeptide substance P and its
receptor NK1. This occurs not only in the dorsal horn of the spinal cord, but
also in the peripheral painful tissue. This up-regulation is part of an
interaction between peripheral nerves, immune cells, and the tissue itself that
seems to help guide the body’s own repair process. In chronic tennis elbow,
this up-regulation of the substance P-NK1 system lingers on. This is what the
researchers have managed to visualize with the help of PET and the marker for
NK1. The method is promising, but the costs are still high. PET is a
complicated procedure, which requires costly equipment. In the future, it is
hoped to be able to develop less expensive markers that could enable routine
use of the method in everyday clinical practice as well as other markers for
other physiological processes that are known to be active in chronic soft
tissue pain.