Quantitative Sensory Testing (QST) - Does assessing ... - TI Pharma

1. General introduction
ongoing pain, hyperalgesia and / or allodynia
which are frequently reported by patients with
neuropathic pain.
Primary afferent fibres (Aβ-, Aδ-, and C-fibres)
transmit impulses fromthe periphery, through the
the dorsal dorsal root ganglion root ganglion (DRG) and (DRG) into the and dorsal into horn the
dorsal of the spinal horn cord. of the Nociceptive spinal specific cord. Nociceptive
(NS) cells are
specific mainly found (NS) in the cells superficial are mainly dorsal horn found (laminae in
the I–II), superficial whereas most dorsal wide dynamic horn ranges (laminae (WDRs) I–II), are
whereas located deeper most (lamina wide dynamic V). Projection ranges neurones (WDRs) from
are lamina located I innervate deeper areas (lamina such as the V). parabrachial Projection area
neurones (PB) and periaqueductal from lamina grey I innervate (PAG) and areas such pathways such as
the are parabrachial affected by limbic area areas. (PB) and From periaqueductal
here descending
grey pathways (PAG) (yellow and arrows) such pathways from brainstem are affected nuclei such by as
limbic the rostral areas. ventromedial From here medulla descending (RVM) are pathways activated
(yellow and modulate arrows) spinal from processing. brainstem Lamina nuclei V neurones such
as mainly the rostral project to ventromedial the thalamus (spinothalamic medulla (RVM) tract),
Figure 1-2: Pain pathways from periphery
are and activated from here the and various modulate cortical spinal regions processing. forming the
to brain
Lamina ‘pain matrix’ V neurones (primary and mainly secondary project somatosensory, to the
thalamus insular, anterior (spinothalamic cingulate, and prefrontal tract), and cortices) from are
here activated. the various cortical regions forming the
‘pain From: matrix’ D’Mello R., (primary Dickenson and A. secondary H., Br. J. Anaesth. somatosensory, 2008;101:8-16 insular, (with permission).
anterior cingulate, and
prefrontal cortices) are activated.
1.1. Neuropathic pain
The International Association for the Study of Pain (IASP) defined pain as “an
unpleasant sensory and emotional experience associated with actual or potential
tissue damage, or described in terms of such damage”. Most pain resolves quickly
but sometimes pain becomes chronic despite removal of the stimulus and apparent
healing of the body. Chronic pain is defined as pain lasting more than three months
(Woolf & Mannion 1999). A specific subclass of chronic pain is neuropathic pain. The
IASP defined neuropathic pain as a direct consequence of a lesion or disease affecting
the somatosensory system (Treede et al 2008). The prevalence of neuropathic pain is
estimated to be as much as 7–8% of the general population in Europe (Bouhassira et
al 2008; Torrance et al 2006). Clinical entities of neuropathic pain include diabetic
polyneuropathies, postherpetic neuralgia, trigeminal neuralgia, central post stroke
pain and spinal cord injury pain. But also traumatic / postsurgical neuropathies and
painful radiculopathies represent common conditions (Torrance et al 2006).