Somatosensory Profile of Central Post Stroke Pain of Thalamic Origin: Findings of a Quantitative Sensory Testing Study

Abstract

Introduction: Central post stroke pain (CPSP) is attributed to vascular lesions of the central somatosensory system, including the thalamus.

Objective: A better characterisation of clinical findings in patients with CPSP after thalamic stroke can facilitate research and treatment of this refractory pain syndrome. We aimed to quantify somatosensory abnormalities in CPSP patients after thalamic stroke.

Methods: Sixteen patients with CPSP after thalamic stroke, 14 patients with a history of thalamic stroke without any pain (stroke control patients, SCP) and 12 healthy controls (HC) underwent detailed clinical examination, standardised quantitative sensory testing (QST) and a pain questionnaire. QST results were compared to age and sex adjusted reference data to obtain z-scores. Group comparisons were performed with one-way analysis of variance.

Results: Temperature perception did not differ in CPSP patients, apart from thermal sensory limen (higher in CPSP vs. HC but no difference vs. SCP). Patients with CPSP showed higher mechanical detection thresholds compared to SCP (Δ = 1.26, p = 0.017, no difference vs. HC) and they were more sensitive to mechanical pain than SCP (lower mechanical pain thresholds vs. SCP: Δ = -1.32, p = 0.014, no difference vs. HC).

Conclusion: Our results indicate somatosensory abnormalities in patients with CPSP after thalamic stroke, associated with the perception of mechanical stimuli. A short somatosensory screening including mechanical perception may contribute to an accurate diagnosis of this debilitating condition.

Significance statement: Thalamic CPSP is very rare, thus our data contribute to the clinical and sensory phenotyping of patients suffering from this debilitating condition. We did not find abnormalities in thermal measures, but only mechanical thresholds in our cohort, suggesting that not only changes in temperature perception are necessary for the development of pain after thalamic stroke. Our findings suggest that a short QST protocol including mechanical testing using von Frey filaments and pin-prick-stimulators may be useful in the diagnosis of thalamic CPSP.

Keywords: CPSP; QST; mechanical pain sensitivity; phenotyping; thalamic pain; thalamic stroke.

FIGURE 1

Pain characteristics in the CPSP group. The description of different pain characteristics is based on the patients' answers in the standardised pain questionnaire (“Deutscher Schmerzfragebogen”). (a) pain character, (b) accompanying symptoms (Skin hypersensitivity refers to the area of pain), (c) affective description, (d) worsening factors (Body posture refers to prolonged sitting/standing/walking) and (e) alleviating factors. Multiple answers were possible, n = number of participants who gave at least one answer (for some questions 1–2 missing).

FIGURE 2

Z‐score values of all QST parameters per group. The age‐ and sex‐adjusted Z‐score values of all QST parameters (based on previously published reference data (Magerl et al. 2010)) are displayed in boxplots per study group. The following QST parameters are shown: (a) cold detection threshold (b) warm detection threshold (c) temperature sensory limen (d) cold pain threshold (e) heat pain threshold (f) mechanical detection threshold (g) mechanical pain threshold (h) mechanical pain sensitivity (i) dynamic mechanical allodynia (j) wind‐up‐ratio (k) vibration detection threshold (l) pressure pain threshold. Note that the Z score values which were outside the 95% CI are depicted in grey. The only parameters showing significant group‐differences were (c) temperature sensory limen, (f) mechanical detection‐ and (g) mechanical pain thresholds, the p‐values of these comparisons are shown in the figure.°C, Degree Celsius; CPSP, Central post stroke pain patients; HC, Healthy controls; mN, Millinewton; SCP, Stroke Control patients.

FIGURE 3

Topography of pain and heatmap of pain distribution in the CPSP group. (a) Visualisation of Heatmap showing the distribution of pain for specific body regions across all CPSP patients. Pain localised in the lower leg (n = 4), face, head (n = 5), upper leg (n = 7), trunk (n = 8), lower arm, foot (n = 10), hand, shoulder (n = 12) and upper arm (n = 14). Please note that the body areas affected by pain were assessed by a standardised pain questionnaire (“Deutscher Schmerzfragebogen”, DGSS, created by the German Pain Association, copyright: https://www.schmerzgesellschaft.de/). (b) Visualisation of Topography of pain and positive/negative sensory symptoms in the CPSP group “Predominant pain” (in red) refers to the body region with the most severe/frequent neuropathic pain. “All pain” (in pink) refers to any body region where the patients experienced pain, not related to the predominant neuropathic pain. “Hypesthesia” (yellow) refers to body regions that showed reduced sensitivity to light touch at bed‐side neurological examination, while “hyperesthesia” (blue bars) refers to positive symptoms revealed or reported by the patients at bed‐side examination (including paresthesia, dysesthesias, hyperesthesia for light touch and allodynia). All illustrations are standardised to show all symptoms on the left side.