Measuring Pain Intensity in Headache Trials

Pain measurement tools are standardized instruments for measuring the subjective experience of pain. These tools have a crucial role in clinical practice and headache research, where they are used to aid diagnosis, evaluate treatment response, and investigate headache pathophysiology. The pain measurement tools are divided into unimodal tools, which measure pain intensity, and multimodal tools, which measure additional qualities of pain. Though numerous pain scales exist, the unimodal tools most established in clinical practice and research include the four—and six-point Verbal Rating Scale (VRS), the Numerical Rating Scale (NRS), the Visual Analogue Scale (VAS), and the Faces Pain Scale-Revised (FPS-R). Of these, the four-point VRS and the NRS are the most ubiquitous. The main multimodal scales in practice and research include the McGill Pain Questionnaire and the Brief Pain Inventory (BPI). Compared to the unimodal scales, the multimodal scales are less commonly used.

Pain scales allow systematic comparisons between headache intensity over time and between patients. Several pain scales are recommended in guidelines for clinical practice and trials, where they can be used to measure responses to both acute and preventive treatment. One drawback is their limited validation for head pain specifically. In addition, they vary in sensitivity and ease of use, and researchers and clinicians should consider which pain scale best suits a given scenario. Finally, while the unimodal pain scales measure pain intensity, they may not capture the full burden of headache disorders. To assess this, multimodal pain scales or patient reported outcomes may provide supplementary measures.