Central pruritus. Case report.

An 82-year-old woman experienced generalized pruritus not due to skin or systemic disease. Scratching the skin with a needle induced a crisis of intense pruritus, insensitive to any drug. The pruritus had the characteristics of a central sensation.

Reflex sympathetic dystrophies and algodystrophies: historical and pathogenic considerations.

This paper reviews the historical development of the concepts of 'sympathy' of organs and of the sympathetic nervous system. In particular, the afferent function of the sympathetic system is discussed. The attention is focussed on sympathetic reflex dystrophies, known in some European schools as 'algodystrophies'. The pathogenic mechanisms of these affections, especially of causalgia, are discussed, considering the importance of peripheral damage to nerves, lateralisation of pain, 'mirror phenomena', and the relationship between peripheral and central mechanisms of pain.

Pain in mitral valve prolapse.

Thirty subjects with mitral valve prolapse were carefully observed, in order to investigate whether chest pain, characteristic of angina pectoris, was present. No cases of angina pectoris or of heart pain were observed. A characteristic which did emerge was that 86% of the subjects suffered a typical myofascial pain of the muscles of the chest. There does not appear to be a clear relationship between mitral valve prolapse and myofascial pain.

Myocardial infarction without pain. A study of the sensory function of the upper limbs.

The sensory function of the upper limbs was examined in 18 subjects who had a myocardial infarction without a well-defined episode of chest pain. The cutaneous pain threshold was significantly higher than in normals. The ischaemia of the upper limbs induced patterns of sensations different from the normals, with onset of pain and of autonomic and coenaesthesic disturbances. These modifications of the sensory function are the same as observed in subjects with a previous painful infarction, but are quite different from those observed in patients with angina pectoris.

Cutaneous pain threshold changes after sympathetic block in reflex dystrophies.

In a group of 30 subjects suffering from sympathetic reflex dystrophies of the limbs, the sympathetic ganglia of the affected side were blocked with a local anesthetic. Using an original method, we measured the cutaneous pain threshold before the block and at prefixed intervals after the block during a period of 2 days. In all subjects the cutaneous pain threshold showed damped oscillations both in the limb ipsilateral to the block and in the contralateral one. The analysis of these oscillations showed: (a) that the sympathetic control of the cutaneous pain threshold may be exerted through a negative feedback loop (skin-afferent input-CNS-sympathetic output-skin); (b) that the afferent discharge of a limb controls the contralateral sympathetic output through central mechanisms.

The effects of non-painful transcutaneous electrical nerve stimulation on cutaneous pain threshold and muscular reflexes in normal men and in subjects with chronic pain.

In healthy subjects and in subjects with chronic myofascial pain of one lower limb, the following was measured in both lower limbs: (i) sequential Hoffman (H) reflex, (ii) sequential Achilles tendon (T) reflex, (iii) cutaneous pain threshold determined with electrical stimuli, before, during and after transcutaneous electrical nerve stimulation (TENS). In healthy subjects no significant differences were observed between the pain thresholds of the two limbs. During and after TENS, changes of the reflexes were related to the pain thresholds. In the pathological subjects a significant difference of pain threshold was present between the affected limb and the contralateral one. An important difference between healthy and pathological subjects is not the quality but the quantity of the changes induced by TENS, in the sense that the levels of inhibition and facilitation of the reflexes are more evident in patients with pain. Indeed, TENS induces a reset of sensory and of motor system and a parallel long lasting effect both on sensory and on muscular function, with concomitant pain relief in the pathological subjects.

Lateralisation of pain in cluster headache.

In 27 patients with cluster headache a careful sensory examination of the entire body was performed. The exam included: the measurement of sensory thresholds with mechanical and electrical stimuli, the assessment of cutaneous and deep hyperalgesia and the ischaemic test of the upper limbs with limbs at rest. In most patients a lateralisation of the findings was observed: cutaneous and deep hyperalgesia were prevalent in the side of cluster headache attacks. The results indicate that in cluster headache, as in other pain syndromes, a lateralisation may be induced throughout the body, probably by phenomena of facilitation in the central nervous system and by activation of reflex arcs.

The effects of non-painful transcutaneous electrical nerve stimulation on cutaneous pain threshold and muscular reflexes in normal men and in subjects with chronic pain

In healthy subjects and in subjects with chronic myofascial pain of one lower limb, the following was measured in both lower limbs: (i) sequential Hoffman (H) reflex, (ii) sequential Achilles tendon (T) reflex, (iii) cutaneous pain threshold determined with electrical stimuli, before, during and after transcutaneous electrical nerve stimulation (TENS). In healthy subjects no significant differences were observed between the pain thresholds of the two limbs. During and after TENS, changes of the reflexes were related to the pain thresholds. In the pathological subjects a significant difference of pain threshold was present between the affected limb and the contralateral one. An important difference between healthy and pathological subjects is not the quality but the quantity of the changes induced by TENS, in the sense that the levels of inhibition and facilitation of the reflexes are more evident in patients with pain. Indeed, TENS induces a reset of sensory and of motor system and a parallel long lasting effect both on sensory and on muscular function, with concomitant pain relief in the pathological subjects.