Aftersensations in experimental and clinical hypersensitivity

Area of Science:

• Neuroscience
• Pain Research
• Clinical Medicine

Background:

• Nerve injury can lead to allodynia, a condition where non-painful stimuli cause pain.
• Sensory changes like aftersensations are common in chronic pain conditions.
• Understanding the mechanisms of aftersensations is crucial for pain management.

Purpose of the Study:

• To investigate aftersensations following repetitive pinprick stimulation.
• To compare aftersensations in nerve injury patients with allodynia and healthy controls with capsaicin-sensitized skin.
• To explore the relationship between evoked pain and aftersensations.

Main Methods:

• Repetitive pinprick stimulation using a computer-driven von Frey hair.
• Stimulation applied to sensitized and normal skin in 41 patients and 12 controls at 0.2 and 2.0 Hz.
• Pain scoring using an electronic visual analogue scale, with analysis of pain onset, duration, and aftersensations.

Main Results:

• Aftersensations were significantly more frequent in sensitized skin compared to normal skin in both groups.
• Evoked pain was more frequent and intense in sensitized skin, with higher scores at 2.0 Hz than 0.2 Hz.
• A positive correlation was found between maximum evoked pain and aftersensation duration in both patients and controls.

Conclusions:

• Aftersensations and evoked pain likely share a common, probably central, mechanism.
• Experimental models can replicate clinical aftersensations, suggesting their utility in assessing central sensitization.
• Aftersensations may serve as a valuable clinical assessment parameter for central sensitization.