Neuropathic pain is accompanied by both positive and negative sensory signs. To explore the spectrum of sensory abnormalities, 1236 patients with a clinical diagnosis of neuropathic pain were assessed by quantitative sensory testing (QST) following the protocol of DFNS (German Research Network on Neuropathic Pain), using both thermal and mechanical nociceptive as well as non-nociceptive stimuli.
Data distributions showed a systematic shift to hyperalgesia for nociceptive, and to hypoesthesia for non-nociceptive parameters. Across all parameters, 92% of the patients presented at least one abnormality. Thermosensory or mechanical hypoesthesia (up to 41%) was more frequent than hypoalgesia (up to 18% for mechanical stimuli). Mechanical hyperalgesias occurred more often (blunt pressure: 36%, pinprick: 29%) than thermal hyperalgesias (cold: 19%, heat: 24%), dynamic mechanical allodynia (20%), paradoxical heat sensations (18%) or enhanced wind-up (13%). Hyperesthesia was less than 5%. Every single sensory abnormality occurred in each neurological syndrome, but with different frequencies: thermal and mechanical hyperalgesias were most frequent in complex regional pain syndrome and peripheral nerve injury, allodynia in postherpetic neuralgia. In postherpetic neuralgia and in central pain, subgroups showed either mechanical hyperalgesia or mechanical hypoalgesia. The most frequent combinations of gain and loss were mixed thermal/mechanical loss without hyperalgesia (central pain and polyneuropathy), mixed loss with mechanical hyperalgesia in peripheral neuropathies, mechanical hyperalgesia without any loss in trigeminal neuralgia.
Thus, somatosensory profiles with different combinations of loss and gain are shared across the major neuropathic pain syndromes. The characterization of underlying mechanisms will be needed to make a mechanism-based classification feasible.
aDepartment of Pain Management, BG Universitätsklinikum Bergmannsheil GmbH, Ruhr University, Bochum, Germany
bDivision of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany
cDepartment of Neurology, Technische Universität, München, Germany
dDepartment of Neurophysiology, Center for Biomedicine and Medical Technology Mannheim, Ruprecht-Karls-University, Heidelberg, Germany
eDepartment of Neurology, University Medical Center of the Johannes-Gutenberg-University, Mainz, Germany
fInstitute of Physiology and Experimental Pathophysiology, University of Erlangen, Germany
gDepartment of Cognitive and Clinical Neuroscience, Central Institute for Mental Health, Ruprecht-Karls-University, Heidelberg, Germany
hDepartment of Anaesthesiology, Ludwig-Maximilians-University, Munich, Germany
iInstitute of Medical Psychology and Behavioural Neurobiology, University of Tübingen, Germany
jDepartment of Neurology, University of Würzburg, Germany
kDepartment of Neurology, University of Ulm, Germany
lDepartment of Neurosurgery, University Campus Lübeck, Germany
*Corresponding author. Address: Deutscher Forschungsverbund Neuropathischer Schmerz (DFNS), c/o Prof. Dr. Christoph Maier, Berufsgenossenschaftliches Universitätsklinikum Bergmannsheil GmbH Bochum, Ruhr University, Bochum, Bürkle-de-la-Camp-Platz 1, D 44789 Bochum, Germany.
1DFNS steering committee.
2These authors equally contributed to this work.
Submitted November 13, 2009; revised April 13, 2010; accepted May 5, 2010.