Functional Brain Imaging to Assess the Efficacy of Manipulative Therapy for Pain Relief

Abstract

Manipulative therapy refers to a manual physical therapy approach performedby a Judo therapist to treat muscle or joint injuries. Evaluation of manipulative therapy outcome in patients typically involves an assessment of the range of motion of the target joint anda measurement of subjective pain relief through an interview or using the visual analog scale (VAS) . However, this approach for pain relief assessment has the limitations of being less objective and problematic if the patient has difficulty communicating with the therapist. To address this concern, we used functional near-infraredspectroscopy (fNIRS) analysis of prefrontal activity to evaluate changes in pain intensity before andafter manipulative therapy. Participant was placedon a treatment table in a supine position with the knees kept straight, and fNIRS probes were attachedto bilateral prefrontal areas, in which the pain-inducedcognitive response occurs. The participant's right leg was kept straight andinflectedtowardthe trunk to the extent that the participant experienceda maximum pain level. At this time, the maximum hip joint flexion angle andthe VAS score were determinedas pre- therapy baseline response. The participant then receivedmanipulative therapy for 5 minutes, andthe right leg was inflectedagain to the same hip joint angle determinedat baseline and VAS score was obtained (post-therapy 1) . The participant's right leg was further inflectedto the extent that the participant experienceda maximum pain level, andthe maximum hip joint angle and VAS score were again determined (post-therapy 2) . Both the VAS score andthe prefrontal hemodynamic activity showed significant decreases after the manipulative therapy (baseline vs. post-therapy 1) suggesting that the therapy increasedthe range of joint motion, andless pain was experiencedat the same joint angle. The maximum inflection of the right leg significantly increasedthe maximum hip joint flexion angle (baseline vs. post-therapy 2). These results suggest that prefrontal hemodynamic activity can be used for objective measurement of pain intensity, andmay be applicable to quantitatively evaluate the effect of manipulative therapy.