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Diffuse noxious inhibitory controls in man. Involvement of the spinoreticular tract
T De Broucker1, P Cesaro, J C Willer
1Clinique Neurologique, Hôpital Beaujon, Clichy, France.
Brain : a Journal of Neurology
|August 1, 1990
Summary
Diffuse Noxious Inhibitory Controls (DNIC) involve supraspinal structures. Painful stimuli inhibit reflexes in healthy individuals, but not in Wallenberg
Area of Science:
- Neuroscience
- Pain Research
- Spinal Cord Injury
Background:
- Heterotopic painful stimuli normally decrease pain sensation and the spinal nociceptive flexion (RIII) reflex.
- This inhibition, mediated by Diffuse Noxious Inhibitory Controls (DNIC), is absent in complete spinal cord transection, indicating supraspinal involvement.
Purpose of the Study:
- To investigate the role of supraspinal structures in DNIC by examining patients with thalamic lesions and Wallenberg's syndrome (WS).
- To determine the neural pathways involved in triggering DNIC in humans.
Main Methods:
- Examined the effect of heterotopic nociceptive stimuli on the RIII reflex in patients with unilateral thalamic vascular lesions and WS.
- Conditioning stimuli were applied to the analgesic and non-analgesic hands of participants.
Main Results:
- Thalamic lesion patients exhibited profound RIII reflex inhibition and after-effects, similar to normal subjects, when stimulated on the analgesic hand.
- WS patients showed no RIII reflex inhibition with conditioning stimuli applied to the analgesic hand.
- Stimulation of the non-analgesic hand in WS patients resulted in inhibition comparable to normal subjects.
Conclusions:
- DNIC triggering in thalamic lesions, even with non-painful noxious stimuli, suggests attentional processes are not the primary mechanism.
- Lemniscal and spinothalamic pathways are not essential for triggering DNIC in humans.
- The brainstem and spinoreticular tract are likely crucial neuronal components of the DNIC pathway in humans.