SYNOPSIS A quantitative method for the examination ofthermal sensibility was applied in 26 normal subjects and in patients with various neurological disorders. The stimulation technique resembled Bekesy audiometry: the patient reversed the direction of the temperature change of a thermode whenever warm, cold, or thermal pain thresholds were reached. The resulting temperature curve enables a quantitative description of the subject's thermal sensibility and of the degree of impairment displayed by neurological patients.It is well known that a disturbance of the temperature sense occurs in many neurological patients as a consequence of lesions in the peripheral or central nervous system. It usually occurs together with a disturbance of other sensory modalities such as cutaneous pain, but it may also appear separately (Goldscheider, 1926).For a closer study of changes in thermal sensibility, a quantitative technique is necessary which allows reliable measurement of warm, cold, and thermal pain thresholds by pure thermal stimuli without tactile components. The method should be easy and quick enough to be combined with routine neurological examination. Although in neurophysiological and psychophysical research several methods have been developed for the study of temperature sensibility (for references cf Kenshalo, 1970), all of them are too complicated and time consuming to be applied FIG. 1 The Marstock stimulator. A thermocouple is clinically. The technique described here has proved to fixed to the centre of the stimulating surface (area be easy enough to be used routinely and repeatedly in 25 x 50 mm). patients in whom it was desirable to establish the degree or the temporal course of a neurological disorder affecting thermosensibility.tions which produce a temperature difference between METHODS upper and lower side of the stimulator when a current STIMULATOR is passed through them. As the reverse side of the stimulator is thermally buffered by a metal block perThe thermostimulator has a rectangular stimulating fused with water of 30°C temperature, the stimulating surface of 25 x 50 mm (Fig. 1), and it operates on the surface can be either warmed or cooled depending on Peltier principle. It consists of semiconductor junc-the direction of the current. The temperature is

A hand-held pressure algometer with a pressure sensitive strain gauge at the tip was used to measure the pressure-pain threshold (PPT) in the temporal region of healthy volunteers. Various sizes of circular tips and various application rates were tested before selecting an area of 0.5 cm2 and a constant application rate of 0.68 N X sec-1 for future use. A highly significant correlation was found between PPT values obtained from the two sides (of the head) (P less than 0.001) and between PPT values obtained with a 3-week interval (P less than 0.001). In a series of 50 immediate consecutive measurements in the same individual, the mean PPT was 171 kPa (N = 6, 2 S.D. 24%). The mean relative change in PPT after a 3-week interval was 0 +/- 51% (N = 11, 2 S.D.). In the course of 5 repeated determinations at weekly intervals there was a significant increase in PPT (ANOVA, P less than 0.05). Subcutaneous lignocaine significantly elevated PPT compared to placebo. Due to the high inter-individual variation, determinations of PPT for group comparisons should include rather large population samples, whereas in paired studies, the intra-individual variation allows the investigation of much smaller groups (10-20 subjects). It is our experience that the pressure algometer is easy to operate in the hands of a skilled laboratory assistant.

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Thirty-eight consecutive patients with neuralgia after peripheral nerve injury were treated with one or two series of peripheral local anesthetic blocks. All patients experienced an initial total relief of ongoing pain for 4-12 h. Evoked pain (hyperalgesia or allodynia), which occurred in 17 patients, was blocked simultaneously with the spontaneous pain. In 18 patients the analgesia outlasted the conduction block and there was a period of complete pain relief of 12-48 h in 13 patients and of 2-6 days in the other 5. In 8 patients there was a second phase of analgesia of 4 h to 6 days duration occurring within 12 h of pain recurrence. Thus, mono- or biphasic prolonged complete analgesia occurred in 25 out of 38 patients. A prolonged analgesia may be the result of a central action of the local anesthetic at the spinal level after intra-axonal incorporation and centripetal axoplasmic transport. To test this hypothesis, an experimental study with [3H]lidocaine was performed in 6 rats. The radioactive local anesthetic was injected into one hind limb foot with the other side serving as a control. Tissue samples from the peripheral nerve, nerve root and the lumbosacral spinal cord segment were analyzed for radioactivity using a scintillation counter technique at various time intervals after the [3H]lidocaine injection. There was a low grade of activity in all samples and no difference between the test side and the control side. Thus these experiments provided no evidence in support of this hypothesis. Various alternative peripheral and central mechanisms are discussed. Further studies specifically directed to these alternatives and with longitudinal controls are prompted.