Table 2.
Recognition of Neuropathic Pain: Sensory Symptoms and Signs of Neuropathic Pain, Clinical and Laboratory Tests, and Underlying Mechanisms
| Sensory symptom and sign | Bedside examination | Laboratory examination | Mechanism |
|---|---|---|---|
| 1. Negative sensory symptoms and signs | |||
| 1) Reduced touch | Touch skin with cotton wool | Graded von Frey hair | Aβ fibers |
| 2) Reduced pin prick | Prick skin with a pin single stimulus | von Frey hair specific (e.g., 100-g) | Aδ fibers |
| 3) Reduced cold and warm | Thermal response to cold and warm objects (20℃ and 45℃) | Detection of pain threshold for warm and cold objects | Aδ/C fibers |
| 4) Reduced vibration | Tuning fork on the medial malleolus | Vibrometer | Aβ fibers |
| 2. Positive sensory symptoms and signs | |||
| 1) Spontaneous pain | |||
| (1) Paresthesia | Grade (0-10) | Area in cm2 grade (0-10) | Spontaneous activity in long-term Aβ afferent fibers |
| (2) Dysesthesia | Grade (0-10) | Area in cm2 grade (0-10) | Spontaneous activity in Aδ/C afferent fibers |
| (3) Paroxysms | Grade (0-10) | Threshold for evocation | Spontaneous activity in C nociceptors |
| (4) Superficial burning pain | Grade (0-10) | Area in cm2 grade (0-10) | Spontaneous activity in C nociceptors |
| (5) Deep pain | Grade (0-10) | Area in cm2 grade (0-10) | Spontaneous activity in joint/muscle nociceptors |
| 2) Evoked pain | |||
| (1) Touch evoked hyperalgesia | Stroking skin with brush | None | Central sensitization: C fiber input and loss of C fiber input |
| (2) Static hyperalgesia | Gentle mechanical pressure | Evoked pain to pressure | Peripheral sensitization |
| (3) Punctate hyperalgesia | Pricking skin with a pin | von Frey hair | Central sensitization: Aδ afferent fibers input |
| (4) Punctate repetitive hyperalgesia (windup-like pain) | Pricking skin with a pin 60 times/30 sec | von Frey hair | Central sensitization: Aδ afferent fibers input |
| (5) Aftersensation | Measurement of pain duration after stimulation | Measurement of pain duration after stimulation | Central sensitization |
| (6) Cold hyperalgesia | Stimulation skin with cool metal roller | Evoked pain to cold stimuli | Central sensitization and disinhibition |
| (7) Heat hyperalgesia | Stimulation skin with warm metal roller | Evoked pain to heat stimuli | Peripheral sensitization |
| (8) Chemical hyperalgesia | Topical capsaicin | Topical capsaicin | Peripheral sensitization |
| (9) Sympathetic maintained pain | Sympathetic blockade | Modulation of sympathetic outflow | Sympathetic afferent coupling |
Reproduced from the article of Jensen and Baron (Pain 2003; 102: 1-8) [2].