14th Congress of the European Federation of Neurological Societies
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The laboratory tools (from punch biopsy to heat evoked potentials and functional neuroimaging)
Rolf-Detlef Treede
Rolf-Detlef Treede
Mannheim, Germany  
Topic: Other
34 slide(s) – 00:22:43– English –2010-09-26
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As a first step to distinguish nociceptive and neuropathic types of pain, questionnaires are useful as screening tools (Haanpää et al. 2009). However, these tools do not allow to make a diagnosis.Medical history and clinical examination are indispensible for that purpose, as usual in neurology. To distinguish different types of pain, the sensory examination is the most important part of the neurological assessment. Motor or autonomic signs may be indirect surrogate markers of peripheral nerve damage. Although these signs are more objective than sensory signs, they do not indicate the state of the pain-signalling system. Quantitative sensory testing uses precise stimuli in the sensory examination, but the outcome is still the patient’s subjective report. There are a few candidate techniques to provide objective evidence for the functional status of the nociceptive system (Cruccu et al. 2010). Punch skin biopsy is an objective measure of epidermal innervation density. It is moderately invasive, and the criteria for quantitative evaluation of the histological sections are still under development to reduce the influence of observer factors. Heat evoked potentials can be elicited by either infrared lasers or contact thermodes. First degree burns may occur as adverse effects of these heat stimuli. Heat evoked potentials are sensitive to detect deficits in the nociceptive system due to both peripheral and central nervous system lesions in patients. In experimental studies, nociceptive signal processing in parasylvian cortex can be distinguished from that in cingulate cortex. Functional neuroimaging is an excellent tool for spatially resolved monitoring of the activity of the entire brain during nociceptive stimulation. It has led to major discoveries on the functions of the nociceptive network in the brain by studying groups of patients or subjects. Two major shortcomings are related to the limited sensitivity of fMRI: negative findings in group comparisons are inconclusive, and as a corollary this means that fMRI cannot currently be used to demonstrate nociceptive deficits at the single subject level. Clinically meaningful findings at the single case level currently require either punch skin biopsy (peripheral nerve terminals) or heat evoked potentials (entire nociceptive system).
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References: Cruccu G, Sommer C,Anand P,Attal N, Baron R, Garcia-Larrea L, Haanpaa M, Jensen TS, Serra J, Treede RD (2010) EFNS guidelines on neuropathic pain assessment: revised 2009. Eur J Neurol. 2010 Mar 8. [Epub ahead of print] Haanpää ML, Backonja MM, Bennett MI, Bouhassira D, Cruccu G, Hansson PT, Jensen TS, Kauppila T, Rice AS, Smith BH, Treede RD, Baron R (2010) Assessment of neuropathic pain in primary care.Am J Med 122:S13-21.
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