Quantitative Sensory Testing - From bench to bedside

The methodology of Quantitative Sensory Testing (QST) comprises standardized testing procedures, which provide information of the integrity of the somatosensory nervous system. Over the years, different protocols have been established, which utilize similar but distinct testing procedures. They pursue the same overall objective to identify loss or gain of function of the respective sensory parameter to better understand the degree of abnormal nervous function and thereby improve patient care in the long-term. Laboratory-based QST protocols, which apply highly standardized testing procedures in pre-defined order and body regions, are considered as the gold standard in sensory testing. However, those protocols often require specifically trained personal, high equipment investment, and are time consuming. Thus, in recent years several attempts have been made to simplify testing protocols as well as reduce high costs of testing equipment such as thermal probe systems. These attempts have culminated in an array of sensory bedside testing protocols subserving the need for protocols that are easy to implement in and provide a standardized assessment within clinical trials. While laboratory and bedside QST that focus on static responses of single stimuli, protocols for testing dynamic QST focus on the functional response to pain also exist. Conditioned pain modulation (CPM) is often applied, which offers the ability to study endogenous inhibition of pain. All of these mentioned methodologies are considered as psychophysical measures and thus rely heavily on the cooperation of the patient or participant. In this chapter we provide an overview of QST along three main lines: (i) laboratory QST, (ii) bedside QST and (iii) dynamic QST. In addition, we discuss advantages and pitfalls of each modality. While we discuss along these lines, it should be noted that methodologies are overlapping: some bedside tests are similar or identical to lab-QST, many lab-QST protocols include a dynamic component, and assessment of dynamic QST requires to start with static assessments.