Little is known about the abnormal temperature sensation in PD, although the impaired temperature sensation may negatively affect the quality of life in PD. Using QST as a diagnostic method, several studies found an increased temperature threshold in PD [14, 16–18]; other studies did not find any difference between the patients and the control group [13, 26]. In our study, only 21% of the patients had increased thermal detection thresholds (CDT or WDT or both) according to the normative data given by Rolke et al . With regard to these findings, abnormal thermal thresholds measured by QST are present in the minority of patients and do not seem to be a typical finding in PD. The study of Lin et al. found similar results . In their cohort of PD patients, 32.1% had abnormal thermal thresholds.
On the other hand, 50% of the patients had difficulty differentiating between warm and cold stimuli; increased thermal detection thresholds, however, were present only in 4 of those patients (28%). This means that patients may have preserved ability to detect a thermal stimulus per se, demonstrated as a normal thermal threshold in QST, but they have difficulty differentiating the type of the applied stimulus. This suggests a deficit in the central processing of the thermal information.
Previous studies [14, 17] found no difference in somatosensory thresholds between the dominant and non-dominant side. Our observation was different. PD patients in our cohort showed higher thermal thresholds on the more affected side compared to the non-dominant side, both for cold and warm stimuli.
Next, we focused on the disease duration, severity of the disease, and antiparkinsonian drug intake as possible modifying parameters of temperature detection thresholds. There was no correlation of CDT or WDT with the disease duration, suggesting that abnormal thermal sensation may be present from the early stages of PD. This finding is consistent with the reports by Nolano et al. [17, 18] and supported by the study of Strobel et al., who found abnormal thermal thresholds in idiopathic REM sleep behavior disorder , which is considered a frequent and important premotor symptom of PD .
The severity of motor impairment, as measured by Hoehn & Yahr scores, did not correlate with the thermal thresholds, suggesting no association between abnormal thermal detection thresholds and dopaminergic deficit. This is also supported by the finding of no significant difference in WDT or CDT in PD patients who take levodopa and who are dopa naïve. Our findings are consistent with other studies that showed no effect of dopamine treatment on thermal sensation [13, 14].