Cerebral blood flow dynamics during pain processing investigated by functional transcranial Doppler sonography

Functional transcranial Doppler sonography (fTCD) enables reliable quantification of cerebral blood flow modulation during neural activation processes. Its high-time resolution, relatively simple technical arrangement, and low costs could make fTCD a useful tool in the investigation of brain activity underlying pain experience in fundamental and clinical research. The present pilot study explored the suitability of this technique to investigate cerebral hemodynamics during the processing of experimental heat pain.

In 46 healthy subjects, blood flow velocities in the anterior cerebral arteries (ACA) and middle cerebral arteries (MCA) of both hemispheres were recorded, while heat stimuli of 45 and 47°C were applied to their left forearms (stimulus duration 20 seconds). Subjective sensory and affective pain intensities were assessed using visual analog scales.

A biphasic right dominant blood flow increase arose in the ACA and MCA with maxima around 5 and 15 seconds after stimulus onset. The response was stronger under stimulation with 47°C with respect to 45°C, and the magnitude of the late response component correlated positively with sensory and affective pain intensity under the 45°C condition.

The findings suggest that fTCD measurements prove sensitive both to different levels of physical intensity of painful stimuli and to interindividual differences in nociceptive responding. fTCD may be a valuable tool in clinical pain research, for instance, when it comes to quantifying the temporal dynamics of exaggerated nociceptive responses in chronic pain, or evaluating treatment effects on nociceptive processing.