This case study describes the interpretation of the reaction time and accuracy of hand MR tasks for upper limb amputees experiencing phantom limb pain.
The patient was a right-handed man in his 40s whose left upper limb was caught in a factory roller, resulting in injury. The patient was urgently admitted to our hospital and underwent debridement and left upper arm amputation. The stump length was 20.0 cm from the acromion to the stump end. The range of motion of the left shoulder joint was 100° flexion and 90° abduction. On day 5 after injury, physical therapy was initiated, mainly involving stretching the shoulder girdle muscles, range of motion exercises for the shoulder joint, and stump management. The patient experienced a tingling sensation in the phantom limb from the left elbow to the fingertips, with a numerical rating scale (NRS) of 7. Tingling was triggered by changes in posture, such as pressure on the axilla or around the scapula, and the patient was unable to sleep at night. Therefore, we initiated motor imagery training using hand MR tasks to improve phantom pain.
The hand MR task presented 20 hand images on a display, and the patient was asked to judge whether the image was from the left or right hand. The results showed that the reaction time for the left hand was shorter than that for the right hand, and the accuracy for the left hand was lower than that for the right hand. This suggests that the patient was unable to perform first-person imagery because of body image disorder and perceived visual information as objects rather than as body parts. Therefore, instead of answering the task quickly, the patient was instructed to take time and prioritize accuracy.
The accuracy of the left-hand MR tasks increased, and phantom pain decreased to an NRS of 0–1, with the phantom limb disappearing.
In hand MR tasks, faster reaction times indicated higher motor imagery ability. However, despite the fast reaction time, the accuracy was low, indicating a body image disorder. Our previous studies have shown that the activation of motor-related regions is greater in first-person imagery than in visual imagery. Therefore, the patient was encouraged to spend time and focus on imagining the hands during MR tasks. Consequently, appropriate body image reconstruction progressed, improving phantom limb pain.
In motor imagery therapy, appropriate body imagery should be performed by taking time and evaluated and implemented properly to ensure accurate imagery.
motor imagery
phantom limb pain
