The reflex response to nociceptive stimulation has been investigated in selected cases, and seems to be moderately reduced. 7 Furthermore, the spinal cord is preserved in these patients, so that avoidance reactions should be possible and relatively normal, unlike the usual situation in syringomyelia. Occasional reports suggest that most or all perception of thermal and pain stimuli is lost. 3 4 5 6 However, we have no real knowledge of what is preserved in the patients with severe or complete lesion of the spinothalamic tract at the medullary level. Selective lesioning of the spinothalamic tract in the lateral medulla results in a contralateral thermoalgic dissociation, which is often incomplete. 1 2 Noxious stimuli also activate the reticular system, which increases arousal. These reactions to heat and pain are mainly carried along the spinothalamic tract and the thalamocortical projections and in the spinal cord, with a multimetameric organization. This helps protect the individual from cutaneous lesion. Thermal and painful stimuli are experienced qualitatively and produce a sensation of unbearable pain and avoidance reactions when they exceed a critical threshold. Patients with Wallenberg syndrome should be informed and made aware of their residual perception of and reactions to noxious stimulation. This implies that noxious thermal stimulation can still be perceived via extra spinothalamic pathways (which are slow and multisynaptic), such as the spinoreticulothalamic tract. Assessment of the RIII noxious reflex revealed persistent response withdrawal reactions, with an increased threshold on the affected side, and partial consciousness of the noxious nature of the stimulus.Ĭonclusions-To our knowledge, this is the first description of the appearance of pain perception of high temperatures in patients with severe spinothalamic injury who are suffering from a complete loss of temperature perception. There were no laser-evoked potentials on this side, which suggested major spinothalamic injury. Analysis of subjective perception of laser stimulation showed a much higher pain threshold on the affected hand. Cold stimulation elicited similar pain perception in one patient. The delay was much shorter when the temperature was increased by 4☌ to 5☌. Pain always occurred after a prolonged delay of 8 to 10 seconds in response to threshold heat, and was described as deep and osseous, and clearly different from that perceived on the nonaffected side. Pain perception could be elicited in both patients by increasing the temperature, with a reproducible threshold of 47☌ to 49☌. Warm stimulation, <45☌, elicited no thermal perception or discrimination. They reported pain perception when touching very warm (>50☌ to 60☌) objects and a brisk, occasionally uncontrolled withdrawal reaction of the arm and hand under the same conditions, without any perception of the heat nature of the stimulus.
0 Comments
Leave a Reply. |